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5903114 | Prophage repression as a model for the study of gene regulation. I. Titration of the lambda repressor. | Wiesmeyer, Herbert (Vanderbilt University, Nashville, Tenn.). Prophage repression as a model for the study of gene regulation. I. Titration of the lambda repressor. J. Bacteriol. 91:89-94. 1966.-The concentration of lambda repressor molecules within a lambda lysogenic cell was estimated from the multiplicity of superinfecting homologous phage necessary to permit replication and release of plaque-forming units. A multiplicity of 20 superinfecting phage was found sufficient to permit replication to occur in the normal lambda lysogen. The phage released after lysis of the superinfected lysogen posed of both prophage and superinfecting phage types. Superinfection of the lysogen at lower multiplicities resulted in the lysis of only a small percentage of infected cells and is thought to represent a possible heterogeneity of repressor concentration in the lysogenic population. Viability of the superinfecting particle was found to be unnecessary for titration of the repressor. The repressor concentration in three lysogens of the nonultraviolet-inducible mutant of lambda, lambda(ind-), was found to be greater than 20 regardless of the host bacterium. However, the number of cells yielding phage after superinfection was found to vary with the particular host. The specificity of the lambda repressor was shown to be limited to homologous phage, as determined following heterologous superinfection experiments with phages T6r, 82c, 434c, 434hy, and 424. In all instances except that of superinfection with phage 434hy, only heterologous phage replication occurred. Superinfection by phage 434hy resulted in the release of both prophage and superinfecting phage types. The latter type represented approximately 80% of the total phage released. |
5903115 | Physicochemical properties of fowlpox virus deoxyribonucleic acid and its anomalous infectious behavior. | Randall, Charles C. (University of Mississippi, Jackson), Lanelle G. Gafford, Richard L. Soehner, and James M. Hyde. Physicochemical properties of fowlpox virus deoxyribonucleic acid and its anomalous infectious behavior. J. Bacteriol. 91:95-100. 1966.-Deoxyribonucleic acid (DNA) was extracted from fowlpox virus-infected tissue, purified inclusions, and purified virus by five variations of detergent and phenol methods. Phenol methods gave a poor yield, whereas detergent techniques extracted up to 78% of the DNA. The buoyant density was 1.695 g/ml, and the melting temperature in 7.2 m NaClO(4) was 39 C, both approximately equivalent to a guanine plus cytosine content of 35 moles per cent. Further proof of the double-stranded nature of the DNA was shown by the characteristic behavior toward deoxyribonuclease, formaldehyde, and heat. Infectious DNA was obtained by the various methods described, but this manifestation of biological activity was capricious and for unknown reasons was often not evident. The infectivity could not be related quantitatively to the amount of DNA employed. Furthermore, the infectious nature of fowlpox virus DNA was demonstrable only when the route of infection was the chorioallantoic membrane. In contrast, whole virus infected both membrane and chick skin with equal efficiency. |
5903150 | On the distribution of a permeable solute during Poiseuille flow in capillary tubes. | Equations are derived describing the dispersion of a permeable solute during Poiseuille flow in a capillary model. It is shown that for the normal range of physiological parameters such as capillary radius, capillary length, blood flow, permeability coefficients, and diffusion constants, the center of mass of a bolus of solute moves at a speed very close to the mean speed of flow and that the solute leaves the capillary with an exponential time course depending on the permeability but not on the diffusion constant. There is no appreciable difference in the dispersion of the solute or in its rate of permeation from the capillary whether one considers piston flow or Poiseuille flow. A bolus of arbitrary radial shape tends to e radially uniform very close to the arterial end of the capillary. |
5903151 | Analysis of permeability data for the case of parallel diffusion pathways. | A method of analyzing permeability or diffusion temperature-flux data, for the case of two parallel, independent diffusion fluxes is presented. Separate activation energies and frequency factors corresponding to independent and concurrent Arrhenius mechanisms are obtained from this procedure when the fluxes are parable magnitude. The method is developed in terms of membrane permeability theory since spatially separate and distinct diffusion pathways are of frequent occurrence in biological membranes. It is illustrated in the specific case of water diffusion through a keratin membrane. The results implicate the presence of "bound" water as a crucial factor in passive diffusion of water and polar molecules through the membrane. |
5903152 | The input impedance of an assembly of randomly branching elastic tubes. | Computations are presented of the input impedance of assemblies of randomly bifurcating elastic tubes, as a generalized model of the arterial system. Account is taken of the viscosity of the fluid, the viscoelastic properties of the walls, the variation of elasticity in the different orders of branches, and the variation in cross-sectional area at the bifurcations. The results show that the distributed and scattered nature of the terminations of such an assembly greatly reduces the influence of reflections upon the behavior of the input impedance. The variation of impedance with frequency is very similar in form to that found in animal experiments for the input impedance of the aorta. The architecture of the arterial system may thus be considered to play an important part in determining the favorably low impedance presented to the heart by the aorta. |
5903154 | An attempt to infer the electrophysiological functions of some intracellular structures in cardiac cells by an electronic analogue. | A circuit which simulates the electrical conduction characteristics of the neuron has been modified by the addition of a feedback loop to simulate the electrical properties of some of the "specialized" tissues of the mammalian heart. It is suggested that there is similar electrical feedback in the muscle cells which is responsible for their electrical properties, and possible relationships between the feedback and observed structures are discussed. |
5903153 | Anisometric transport of ions and particles in anisotropic tissue spaces. | The results of time-lapse measurements and electron microscopic observations on the diffusion of histological dyes, colloidal particles, and heavy metal salts in excised chicken breast tendon are reported. In all cases, the transport was found to be anisometric, the extent of the spreading being much greater parallel than perpendicular to the collagen fibers. The diffusion of colloidal gold was shown to be governed by a random diffusion process, with coefficients of 3 to 5 x 10(-7) and 1 to 2 x 10(-7) cm(2)/sec for the parallel and perpendicular directions, respectively; the anisotropy was attributed to steric hindrance. In the diffusion of uranyl nitrate, a sharp boundary appeared at the leading edge of the diffusate and advanced at a rate proportional to the square root of time. Electron micrographs showed uranyl nitrate clusters localized in space on the surface of the collagen fibrils and tightly bound to the polar amino acid regions of the macromolecule. A model was proposed involving diffusion with attrition, and predicted a sharp boundary advancing proportionally to the square root of time and to the 0.65 power of the initial diffusate concentration. Application of the model to the experimental results for uranyl nitrate gave a diffusion coefficient of 10 x 10(-7) and 4 x 10(-7) cm(2)/sec for the parallel and perpendicular directions, respectively, and a possible explanation of this large difference was advanced. The importance of anisometric transport in anisotropic tissues was indicated. |
5903155 | A mathematical evaluation of the core conductor model. | This paper is a mathematical evaluation of the core conductor model where its three dimensionality is taken into account. The problem considered is that of a single, active, unmyelinated nerve fiber situated in an extensive, homogeneous, conducting medium. Expressions for the various core conductor parameters have been derived in a mathematically rigorous manner according to the principles of electromagnetic theory. The purpose of employing mathematical rigor in this study is to bring to light the inherent assumptions of the one dimensional core conductor model, providing a method of evaluating the accuracy of this linear model. Based on the use of synthetic squid axon data, the conclusion of this study is that the linear core conductor model is a good approximation for internal but not external parameters. |
5903165 | Paracervical block anesthesia in labour. | The efficacy and safety of paracervical block anesthesia were studied in 153 patients in the first stage of labour. Transient decrease in uterine activity was noted in 77 patients. There was no acceleration in cervical dilatation following the block. The duration of action of the block in 80 primiparas was 31 to 120 minutes in 69, and over 120 minutes in five. In the 73 multiparas, 53 of the blocks lasted 31 to 90 minutes, eight from 90 to 120 minutes, and two over 120 minutes. The results were good in 66 primiparas and 54 multiparas. The blocks failed in four primiparas and six multiparas. Twenty-six infants had low Apgar scores, but in none could this be related to the paracervical block. There were no significant fetal or plications. |
5903166 | On the history of men and genocide. | A historical and psychological study of genocide is presented in which special emphasis is given to modern manifestations of this phenomenon. The policy of eradication of the Jews by the Hitler regime is considered as an example of genocide in the twentieth century. The psychopathology of genocide and plex relationships among aggressors, victims and witnesses are elaborated. Inferences are drawn from past and present patterns of genocide that may provide some leads to the future. It is now possible to envisage an all-consuming genocide unless nations can learn to live together, not necessarily in unity but in diversity. |
5903164 | The effects of peritoneal dialysis on the physiological disposition of oxacillin, ampicillin and tetracycline in patients with renal disease. | Seven patients with acute or chronic renal failure who were receiving intermittent peritoneal dialysis and who required parenteral oxacillin, ampicillin or tetracycline were studied to determine the disposition of these antibiotics in severe renal disease and the effects of peritoneal dialysis. While severe renal impairment markedly prolongs persistence in the serum of ampicillin and tetracycline, there is little effect on oxacillin. Whereas required doses of ampicillin and tetracycline are lower in the presence of severe renal disease, oxacillin should be given in doses equivalent to those used for patients with normal renal function. Peritoneal dialysis does not alter these dosage requirements.Four patients receiving ampicillin or tetracycline in the infusing solution during peritoneal dialysis were studied to determine the amount of systemic absorption. Local prophylaxis alone is not achieved with this method of administration, since small amounts of both antibiotics are absorbed systemically from the infusing solution. The serum concentration of tetracycline attained is inadequate for treatment of systemic infections but is probably significant, with repeated use in intermittent dialysis, in causing adverse effects. Tetracycline should be abandoned in the local prophylaxis of peritonitis during peritoneal dialysis. |
5903168 | Chronic hemodialysis for terminal renal failure. | Ten terminal uremic patients seen over the period of one and one-half years have been kept alive by repeated hemodialysis using a modification of the Seattle system, carried out for the most part by nurses and technicians. All the patients had creatinine clearance values below 5 ml./min., and blood urea nitrogen values which ranged between 156 and 453 mg. % before beginning the first dialysis.Selection was based on their ability to co-operate with and to tolerate the regimen. Nine patients were fully rehabilitated.The plications were those related to shunt-site infections, including septicemia, bacterial endocarditis, septic arthritis, septic pulmonary embolism and mycotic aneurysm.Nevertheless, all patients except one were rehabilitated and resumed their full-time occupations and have continued to lead happy and useful lives. |
5903169 | Intermittent hemodialysis in terminal chronic renal failure. | Seven patients with chronic renal failure underwent intermittent hemodialysis for five to 37 months (111 patient-months on a twice-weekly basis) employing arteriovenous Teflon-Silastic cannulas and the modified two-layer Kiil hemodialyzer. A single-pass 37 degrees C. dialysate system has been used. One patient died of an indirectly related cause. All other patients have been successfully rehabilitated and now carry on normal activity of moderate sedentary type. Complications included recurring infection and clotting of arteriovenous cannulas. Hypertension and anemia plications requiring careful control. Peripheral neuropathy was noted in five of the seven patients but was of clinical significance in only one patient. Metastatic calcification, osteoporosis and urolithiasis also occurred in this patient. Peptic ulcers with hemorrhage developed in two patients. The degree of rehabilitation and psychological adjustment achieved by this group of patients strongly indicates the need for expansion of dialysis facilities and further research into the medical and economic aspects of dialysis. |
5903337 | Synthetic myosin filaments. | A stable preparation of myosin filaments was formed in a medium at pH 8.0. The filament length varied from 0.2 to 0.5 micron. Most of the material sedimented at 21S, but there was a minor peak (due to monomer) at 6.8S. The filaments did not taper and had large bulbous irregularities at the ends. |
5903338 | Liquid water in frozen tissue: study by nuclear magnetic resonance. | Nuclear magnetic resonance (NMR) spectroscopy was used to examine the behavior and extent of liquid water in postrigor-frozen tissue of cod at temperatures below 0 degrees C. A liquid-water phase persists in the tissue down to about -70 degrees C; the extent of the phase decreases rapidly between 0 degrees and -10 degrees C and slowly at lower temperatures. That the NMR absorption peak of the liquid water increases in width, with decreasing temperature, suggests loss of mobility or structuring of the phase. A technique for introducing geometrically uniform cores of muscle into the probe of the high-resolution spectrometer permits quantitative determinations of liquid water. |
5903339 | Thyrocalcitonin inhibition of bone resorption induced by parathyroid hormone in tissue culture. | Added thyrocalcitonin greatly diminished parathyroid-hormone-induced resorption of bone in tissue culture. The results indicate that bone is primary site of action of thyrocalcitonin. |
5903340 | Tryptophan pyrrolase induced in human liver by hydrocortisone: effect on excretion of kynurenine. | Administration of hydrocortisone causes two- to fourfold increase in the level of activity of tryptophan pyrrolase in human liver, as measured in needle-biopsy specimens. Correlation of the higher levels of the enzyme with the amounts of urinary kynurenine suggests that the tryptophan pyrrolase level, which is regulated by adrenocortical hormones, may be the important variable in the increased excretion of tryptophan metabolites that panies various diseases. |
5903341 | Light sense in nematodes. | The stimulating effect of daylight on the oxygen uptake of the infective larvae of Haemonchus contortus and Nippostrongylus basiliensis, measured at constant temperature, provides the first proof of a dermal light sense in the Nematoda. Nippostrongylus larvae are less sensitive than those of Haemonchus and require very high light intensities before a significant effect can be detected. |
5903342 | Fluctuation tests with antibody-forming spleen cell populations. | Shortly after immunization of mice, cells forming specific antibodies to one antigen, for example, sheep red blood cells, are nonrandomly distributed throughout the spleen. If the spleen donor has been immunized with two different antigens, for example, sheep red blood cells and chicken red blood cells, the nonrandom distribution of spleen cells forming antibody to one antigen differs significantly from that of cells forming antibody to the other antigen. These findings are in accord with a clonal distribution of antibody-forming cells. |
5903343 | Pheromone: evidence in a decapod crustacean. | Males of the species Portunus sanguinolentus display a behavioral response to the presence of premolt females which is the same as their behavior when they are exposed to water in which premolt females have been kept. Release of a sex-attractant pheromone is indicated. When females are prevented from releasing urine, there is no evidence of the attractant. |
5903344 | Starch-deficient maize mutant lacking adenosine dephosphate glucose pyrophosphorylase activity. | The maize mutant shrunken-2 synthesizes only 25 to 30 percent as much starch as normal maize; pletely lacks adenosine diphosphate glucose pyrophosphorylase activity in both endosperm and embryo tissue. Identification of the mutant block indicates that the greater portion of starch in the endosperm of normal maize is synthesized by way of enzyme systems that utilize adenosine diphosphate glucose as a substrate, and that the latter is formed chiefly by adenosine diphosphate glucose pyrophosphorylase. |
5903345 | Subcellular sources of luminescence in Noctiluca. | The perivacuolar cytoplasm of Noctiluca miliaris contains approximately 10(4) microsources of luminescence, with dimensions of 0.5 to 1.5 microns, which exhibit marked fluorescence with ultraviolet excitation. Local invasion by an action potential elicits light emission (microflashes) from these sources with a coupling latency of about 2 milliseconds. Magnitudes of the microflash vary directly with the dimensions of the source. Time courses of the microflash resemble that of the macroflash emitted by the whole cell but have somewhat shorter time constants. The small discrepancy induration between micro- and macroflash can be explained by the 5- to 10-millisecond asynchrony of microsource triggering that results from the conduction time of the action potential. Reversible gradations in amplitude of the macroflash, as from potentiation or fatigue, result from parallel summation of graded changes in microflash intensity. Thus the macroflash gives a reasonably true picture of the subcellular kinetics of luminescence. |
5903346 | Enhanced distress vocalization through selective reinforcement. | Eighteen Peking ducklings were imprinted and tested for their tendency to emit distress calls during the presentation and withdrawal of the imprinted stimulus. A subsequent arrangement in which each distress vocalization led to a 5-second presentation of the imprinted stimulus resulted in an enhanced tendency to emit distress calls. |
5903347 | Age differences in infants' attention to patterns of different complexities. | Infants 3 weeks, 8 weeks, and 14 weeks old were presented with checkerboard patterns which differed in the number of squares they contained. The older the infants, the plex was the checkerboard that they looked at longest. This result does not appear to depend on changes in visual acuity or modation related to age. |
5903581 | Structure and organization of the living mitotic spindle of Haemanthus endosperm. | New details of mitotic spindle structures in the endosperm of Haemanthus katherinae (Bak) have been demonstrated by differential interference microscopy. Spindle fibers are clearly seen in the living spindle extending from the kinetochores to the polar region. Individual spindle fibers consist of a bundle of smaller filaments which diverge slightly from the kinetochore and intermingle with filaments from other spindle fibers as they approach the polar region. The degree of intermingling increases during metaphase and anaphase. The chromosomes stop moving when the spindle fibers are still 5 to 10microns long; then the fibers disappear. These observations explain some aspects of spindle movements which were difficult to reconcile with earlier concepts of spindle organization. |
5903582 | Pentobarbital sodium: variation in toxicity. | The survival rate of groups of female mice given a standard dose of pentobarbital sodium varied during a 12-hour period. When survival rate was plotted against time, a curve with several inflections was described. |
5903584 | Chromosomal aberrations in a population of ground squirrels. | Chromosomes were analyzed from a population of Spermophilus beldingi that included an adult female and three juveniles from the same burrow. All animals had a diploid number of 30. The adult and a juvenile female from the burrow had identical aberrant karyotypes containing an unpaired submetacentric and a minute metacentric chromosome. A familial aberration involving an X chromosome, without phenotypic alteration, is most probable. |
5903583 | Ozone: nonlinear relation of dose and injury in plants. | Ozone produces a sigmoidal dose-injury response in sensitive tobacco and pinto bean. A definite threshold concentration and presentation time are required before injury is initiated. |
5903585 | Sex-linked anemia: a hypochromic anemia of mice. | This hereditary anemia is most severe in young mice and tends to diminish with increasing age. Erythrocytes show great variation in size and form, with hypochromia and formation of target cells. Though the anemia occurs on a normal diet, it responds rapidly to iron-dextran injection. It may represent an unusual primary disturbance of iron metabolism. |
5903586 | Swimming speed of a Pacific bottlenose porpoise. | Four kinds of speed runs showed a Pacific bottlenose porpoise (Tursiops gilli) to have a top speed of 29.9 kilometers per hour (16.1 knots) for 7.5 seconds and a top speed of 21.9 kilometers per hour (11.8 knots) for 50 seconds. These pare closely with highest predictions based upon rigid body drag calculations, the same power output per unit body weight as for athletes, and a propulsive efficiency of 85 percent. |
5903587 | Sialic acid binding sites: role in hemagglutination by Mycoplasma gallisepticum. | Hemagglutination of turkey erythrocytes by Mycoplasma gallisepticum was inhibited by mucoproteins containing sialic acid, by sialic acid itself, and by treatment of the erythrocytes with neuraminidase. Neuraminidase treatment of the mucoprotein-rich inhibitors reduced or abolished their inhibitory activity. The findings indicate that sialic acid on the erythrocyte surface provides binding sites for Mycoplasma gallisepticum. |
5903588 | Correction to one of MacArthur's species-abundance formulas. | The expected relative abundances of moner species in a biological population are less if the niches are overlapping than if they are non-overlapping. MacArthur's mathematical arguments, which lead to the opposite conclusion, are incorrect. |
5903589 | Puromycin effect on successive phases of memory storage. | Mice injected bitemporally with puromycin 5 hours before training learned to escape or to avoid shock by choosing the correct limb of a Y-maze. When retested 15 minutes after training they had normal retention. In the ensuing 2(3/4) hours the animals injected with puromycin, unlike the controls, showed a progressive decrease of savings to less than 7 percent. |
5903712 | Electronystagmography: its clinical application. | Nystagmus is a phenomenon of considerable physiological significance and one of the most important expressions of vestibular disease. Electronystagmography (ENG) makes possible the exact recording of the eyeball movements and the quantitative assessment of the various parameters of nystagmus, spontaneous or induced, with obvious advantages in the differential diagnosis of neuro-otological disorders. The principles and methods of this procedure are demonstrated and analysis of ENG tracings in illustrative clinical cases is shown. |
5903711 | [Pulmonary arteriovenous fistula]. | A case of multiple pulmonary arteriovenous fistulas is reported. Hereditary hemorrhagic telangiectasia is a characteristic associated finding, and in this instance affected 10 members of the patient's family over four generations. This association suggests that the pulmonary condition in its congenital form is part of a generalized vascular dysplasia. Clinically, the patient experienced increased dyspnea and fatigue but cyanosis and polycythemia were not noted. After surgical excision of the fistula with conservation of as much pulmonary tissue as possible, prompt relief of symptoms was obtained. Furthermore, angiographic studies revealed that the small fistulas in the other lung did not enlarge. The presence of multiple fistulas is not a contraindication to surgery, and such fistulas should be excised to improve the patient's condition and prevent plications. |
5903713 | Revascularization of the entire heart by internal mammary artery implantation, epicardiectomy and free omental graft. | The indications for and the contraindications to total cardiac revascularization are described on the basis of the author's experience. bined operation of internal mammary artery implant, epicardiectomy and free omental graft was performed on 62 patients. Of 45 who did not have angina at rest without exciting cause (Grade I) 39 showed improvement; 32 returned to full-time work, 18 of whom had been unable to work before operation. There were two operative deaths. Among the 17 patients who were "bed-chair cripples" (angina at rest without cause-Grade II), there was a 24% operative mortality (four deaths), but 76% of the survivors had marked improvement. Only one of this group had been working full-time preoperatively; now nine are working full-time. |
5903951 | Interocular generalization: a study of mirror-image reversal following monocular discrimination training in the pigeon. | Generalization gradients along a continuum of angular orientation were obtained from four pigeons, following monocular training on a discrimination between a 45 degrees oblique line (S+) and a 135 degrees oblique line (S-). All pigeons were trained on a chain DRO VI 1 schedule of reinforcement. Generalization gradients obtained with the trained and untrained eye pared. All pigeons responded maximally to the 45 degrees line (S+) when tested with only the trained eye open. During generalization tests of interocular transfer with only the untrained eye open, three pigeons responded maximally to S- (135 degrees ), the mirror-image of the stimulus associated with reinforcement during training (45 degrees ). The other pigeon failed to show interocular transfer of the discrimination. Interocular reversal of left-right mirror-image stimuli has not been reported for any other species. |
5903953 | The motivational properties of schedule-induced polydipsia. | Schedule-induced polydipsia occurred during initial magazine training to Noyes pellets (45 mg), disappeared when lever-pressing was acquired on a continuous reinforcement schedule (CRF), and reappeared when the food contingency was changed to a 1-min variable interval schedule (VI 1 min). Polydipsia also developed under a VI 1 min food schedule when water was concurrently available on various fixed ratios (FR), rather than being freely available. The level of the polydipsia and its motivating properties allow it to be classified as a form of adjunctive behavior. |
5903954 | Some discriminative properties of fixed ratio performance in the pigeon. | The discriminative control over a spatial choice response exercised by prior behavior was studied using a procedure involving discrete exposures to a two-member chained schedule. The initial member (red key) was either a smaller or larger fixed ratio (Mix FR:FR), pletion of which produced, after a 1-sec delay, two white response keys. If the larger FR had pleted as the initial chain member, a single peck on the right white key was reinforced; after the smaller FR, a peck on the left white key was reinforced. Frequencies of unreinforced responses (S(Delta) responses) were determined with several pairs of red-key FRs: 95-5, 75-25, 65-35, 60-40, 58-42 and 50-50. The S(Delta) response frequencies were low through the FR pair 65-35; sharp increases were obtained with pairs 60-40 and 58-42. Later, curves analogous to stimulus generalization functions were obtained using a probe procedure. Finally, the delay interval pletion of a red-key FR and the white-key choice response was manipulated: results were variable, but S(Delta) response frequencies tended to increase with increasing delays. |
5903956 | Threshold for conditioned suppression using x-rays as the pre-aversive stimulus. | Four male, 12-week-old Sprague-Dawley rats were used to determine the threshold for behavioral response to X-irradiation using the conditioned suppression technique. They were maintained at 80 per cent body weight and initially trained to stable performance on a VI 1 min schedule with 16 per cent sucrose solution as reinforcement. After a stable baseline was obtained, animals were placed in the instrumental conditioning box beneath the X-ray machine for a half-hour session each day. While subjects were actively pressing the lever for reinforcement, 15-sec X-ray exposures of 0.5 R/sec were administered, followed immediately by electric shock. After all animals had exhibited conditioned suppression, the dose-rate was decreased in subsequent sessions in an effort to establish threshold. The results indicate that X-rays at a dose-rate as low as 0.004 R/sec can be an effective pre-aversive stimulus for the rat. |
5903958 | Schedule-induced polydipsia as a function of fixed interval length. | Rats were trained to bar-press for Noyes pellets on an FI schedule which was increased serially through several values from 2 sec to as high as 300 sec. Concurrently, water was freely available. As FI length was increased, the degree of polydipsia increased linearly to a maximum value. |
5903960 | A comparison of two types of extinction following fixed-ratio training. | Five groups of pigeons were food reinforced on various schedules. Half of each group were extinguished in the normal manner; the others were presented with a stimulus change, previously paired with reinforcement, each time pleted their respective fixed ratios. Response rate in training was an increasing negatively accelerated function of the FR. Increasing the FR produced transitory rate changes, the amount of which yielded a quantitative index of ratio strain. Cumulative records of extinction performance revealed that the stimulus change exerted discriminative control by maintaining the cohesiveness of FR response units. Nevertheless, neither the absolute number of extinction responses nor extinction response units differed appreciably for the two extinction procedures. |
5903964 | Punishment of an extinguishing shock-avoidance response by time-out from positive reinforcement. | Two experiments were conducted to determine the effects of punishment by time-out from positive reinforcement on the extinction of discriminated shock-avoidance responding. Subjects were trained initially to bar press for food on an intermittent schedule of reinforcement and, concurrently, to avoid shock at the onset of a warning signal. Experiment pared avoidance extinction performance under no punishment and when avoidance responding resulted in a 30-sec TO from reinforced appetitive responding. In Exp II, the contingent use of TO punishment pared with its random, or noncontingent use. The results of both experiments showed that in the absence of punishment, avoidance extinction was characterized by short latencies and nearly 100% avoidance responding. Avoidance responding in extinction was little affected by noncontingent TO punishment. When TO was made contingent upon avoidance responding, however, avoidance latencies immediately increased and the frequency of avoidance responses subsequently decreased to zero. |
5903966 | Discrimination and emission of temporal intervals by pigeons. | Because the frequency distribution of IRTs showed little or no control by a DRL schedule, the schedule was modified so that the pigeon's behavior after each IRT would indicate whether or not it had discriminated the duration of the IRT. After every two pecks on a red key, the key changed to blue for 30 sec. Then it automatically became red again. Pecks on the blue key were reinforced with food on a VI schedule only when the preceding IRT on the red key had been longer than 18 sec. The birds did not selectively emit longer IRTs on the red key: the value of IRTs/op did not increase with IRT duration. However, they did discriminate the duration of the IRT emitted on the red key: the rate of pecking on the blue key was an increasing function of the duration of the preceding IRT on the red key. |
5903967 | Operant conditioning of a small-scale muscle response. | Six naive male subjects were reinforced for responses in the 20-30 microvolt range, and two each for those in 10-20 and 30-40 microvolt ranges. Records were taken of 15 min of "settling down," 15 min of initial operant level responding, 30 min of conditioning, and 45 min of extinction, 30 min with light present and 15 min without. The results were: (1) small-scale muscle potentials from the thenar eminence, in the 10-20, 20-30, and 30-40 microvolt ranges, were conditioned, using pointer movement as the reinforcement; (2) the response rate in adjacent ranges of greater and lesser amplitude also increased during such conditioning and decreased during the subsequent extinction; (3) during conditioning the frequency of response distribution shifted toward the reinforced range; (4) subjects were unaware of the reinforced response; (5) observing a noncontingent moving pointer increased the response rate in the 20-30 microvolt range, but did not lead to conditioning. |
5904586 | Suppression of plant growth by nitrogen dioxide. | Nicotiana glutinosa and pinto bean seedlings (Phaseolus vulgaris) were exposed for short periods (3 days or less) to high concentrations of NO(2) (4.11-20.53 mg/m(3) pare the resulting leaf lesions with ozone damage produced at concentrations of 0.43 to 0.86 mg/m(3). Although the same physiological age leaf tissue was damaged by both toxicants, damage caused by NO(2) was unlike that caused by ozone. Pinto bean (Phaseolus vulgaris) and Pearson improved tomato (Lycopersicon esculentum) seedlings were continuously exposed for 10 to 22 days, to low concentrations of NO(2) (less than 1.03 mg/m(3)). These exposures caused significant growth suppression, increase in green color (total chlorophyll content), and distortion of leaves. |
5904587 | Fat metabolism in higher plants. XXVI. Biosynthesis of fatty acids in tissues of developing seeds and germinating seedlings of safflower (Carthamus tinctorius L.). | The capacity of both developing seeds and germinating seedlings of safflower for the incorporation of acetate-C(14) into long-chain fatty acids is examined. Intact tissue of the developing seed shows a low rate of acetate incorporation into fatty acid initially but between the tenth and twenty-fifth day after flowering the tissue has a high rate of synthesis, in particular with respect to the unsaturated fatty acids. Centrifuged fractionation of homogenates of this developmental tissue yielded several active fractions, the most active being the P(I) fraction consisting mostly of plastids. Cofactor requirements and pH effects are examined. Germinating tissue shows a more uniform capacity for synthesis of fatty acids since there is no marked change in synthetic capacity. The newly synthesized fatty acids are consistently palmitic, stearic, and oleic acid. No linoleic synthesis could be detected. The most active fraction of cell-free preparation of germinating tissue is the plastid fraction (P(I)), similar to what was formed with developing tissue. |
5904588 | Action of inhibitors of RNA and protein synthesis on cell enlargement. | Further studies with inhibitors of protein synthesis are presented to support the conclusion, drawn from work with chloramphenicol, that protein synthesis is a critical limiting factor in auxin-induced cell expansion. The indoleacetic acid-induced elongation of oat coleoptile sections was strongly inhibited by dl-p-fluorophenylalanine, and the inhibition is antagonized by phenylalanine. Puromycin at 10(-4)m very strongly inhibited the indoleacetic acid-induced growth of oat coleoptile and artichoke tuber sections and exerted a less powerful effect on pea stem sections. As found earlier with chloramphenicol, concentrations of puromycin effective in inhibiting the growth of coleoptile sections had quantitatively similar effects on protein synthesis, as measured by the incorporation of C(14)-leucine into protein of the coleoptile tissue. Several analogues of RNA bases were also tested, but while 8-azaguanine very strongly inhibited growth of artichoke tuber disks, 6-azauracil was the only one of this group clearly inhibitory to growth in coleoptile or pea stem sections. Actinomycin D actively inhibited both elongation and the incorporation of C(14)-leucine into protein in oat coleoptile sections. Inhibition of the 2 processes went closely parallel. Actinomycin D also powerfully inhibited growth of artichoke tuber disks. All pounds effective in inhibiting growth generally inhibited the uptake of leucine as well. The possibility that auxin causes cell enlargement in plants by inducing the synthesis of a messenger RNA and of one or more new but unstable enzymes, is discussed. Possible but less favored alternative explanations are: A) that auxin induces synthesis of a wall protein, or B) that the continued synthesis of some other unstable protein (by a process independent of auxin) may be a prerequisite for cell enlargement. |
5904589 | Movement of indoleacetic acid in coleoptiles of Avena sativa L. II. Suspension of polarity by total inhibition of the basipetal transport. | Acropetal and basipetal movement of indole-3-acetic acid through coleoptiles of Avena sativa L. was studied. Sections 10-mm long were supplied with either apical or basal sources containing C(14) carboxyl-labeled indoleacetic acid (10(-5)m). Anaerobic conditions inhibit metabolically dependent movement (transport) thus reducing basipetal but not acropetal movement. Total inhibition of basipetal transport abolishes the polarity of auxin uptake and movement. The nonpolar movement that remains in anaerobic sections is free diffusion with an average diffusion coefficient of approximately 1 x 10(-4) mm(2) per second. During an 8-hour diffusion, at least the first millimeter of the es to equilibrium at approximately the same concentration as the donor.Acropetal movement is probably by diffusion and is panied by an aerobic immobilization of indoleacetic acid that increases more than proportionally to concentration. Anaerobic conditions totally prevent this immobilization and reduce acropetal uptake but not the amount of indoleacetic acid moving into the upper parts of the section; there is, therefore, no evidence for acropetal transport. Polarity of auxin movement in aerobic coleoptile sections is achieved by strict basipetal transport of auxin. The basipetal transport may intensify the polarity by recycling auxin that is moving acropetally. |
5904590 | Monochromatic light saturation curves for photosynthesis in Chlorella. | We used a small oxygen electrode and a grating monochromator of 10 mmu half-band width to determine light-saturation curves of photosynthesis for films of Chlorella pyrenoidosa no more than 1 cell thick. All curves were referenced to the lightsaturated rate observed in 5 mw/cm(2) of 680 mmu. To a close approximation (+/- 2%) the light-saturated rate was independent of wavelength over the region in which light intensity was sufficient to make the test (450-705 mmu). At wavelengths of high absorption we obtained intensities sufficient to cause photoinhibition. As a measure of photoinhibition we used the breakpoint, the lowest intensity at which rate of photosynthesis decreased with time. In general, the saturated rate was slightly lower and the estimated breakpoint was considerably lower at wavelengths of high absorption. Maximum rate of absorption of quanta at the breakpoint was highest in the far-red (>/= 700 mmu), lower and relatively constant in the near-red (630-680 mmu), and lowest in the blue. At 435 and 450 mmu the breakpoint occurred below saturation. We attribute small deviations in maximum rate of photosynthesis to effects of photoinhibition. Independence of wavelength observed for the light-saturated rate is consistent with models of photosynthesis in which maximum rate is limited by the same dark reaction at all wavelengths. |
5904925 | Powassan virus: vernal spread during 1965. | Powassan virus was isolated from seven pools of Ixodes cookei ticks removed from groundhogs (Marmota monax) collected near North Bay, Ontario, between May and August 1965, including five pools obtained during spring. Tick pools, prising one to nine ticks, contained 2.0 to 5.5 log(10) TCD(50) of virus upon titration in monolayer cultures of primary swine kidney cells. Powassan virus neutralizing antibody prevalence in sera of the current season's groundhogs increased steadily from zero during May to 25% during August but remained relatively unchanged (42% to 58%) in the previous season's groundhogs, thereby confirming that active infection had occurred particularly amongst juvenile groundhogs mainly during spring 1965. Isolation of one strain of Silverwater virus from Haemaphysalis leporis-palustris ticks and detection of neutralizing antibody in three of nine snowshoe hares (Lepus americanus) confirmed the active spread of this agent during 1965. |
5904926 | [Traumatic thrombosis of the internal carotid artery]. | Two cases of post-traumatic thrombosis of the internal carotid artery are presented, which are of interest because of their relative rarity. A detailed understanding of the pathogenesis and variety of clinical presentations, an adequate appraisal of the diverse proposed treatments, and an improvement in the prognosis, which is poor even in young patients-these await further enquiry and research. |
5904927 | Conjoint psychotherapy of marital pairs. | Many traditional concepts are being challenged in contemporary psychiatric practice, including the classical "one-to-one" relationship of individual psychotherapy. Where the patient's presenting difficulties include significant inability to function or feel happy in the marital role, the technique of conjoint psychotherapy (having both partners treated simultaneously by the same doctor) may be indicated. Conjoint therapy is envisaged as a continuum, embracing a considerable range of situations where it is sound practice to see husband and wife together. The treatment plan has three plaint, clarification, promise, each of which presents specific features and pitfalls. Emphasis is placed on dealing with individual psychopathology of each partner, both per se and in relation to the marital situation. Results to date suggest that conjoint treatment represents a promising therapeutic modality. Even in cases where individual psychopathology cannot fully be resolved, certain plateaus of satisfaction may be attained munication improves. |
5904975 | Aseptic addition method for Lactobacillus casei assay of folate activity in human serum. | An ;aseptic addition' method is described for microbiological assay with Lactobacillis casei of folate activity in human serum. It has the following advantages over the previously reported ;standard' method. 1 The manipulations involved in the assay are halved, by deleting autoclaving of serum in buffers. 2 The use of 1 g.% ascorbate better preserves serum folates than the lower amounts of ascorbate which are the maximum quantities usable in the standard methods. 3 Only 0.3 ml. of serum is required (0.1 ml. for one sample; 0.2 ml. for its duplicate). |
5904976 | Method of assay of red cell folate activity and the value of the assay as a test for folate deficiency. | A simplified microbiological assay for determining the folate content of red cells is described. As in previously reported methods Lactobacillus casei is used as test organism but two modifications are introduced. First, haemolysis is carried out in water containing 1 g.% of ascorbic acid; secondly, haemolysates are not incubated before the assay. Using this assay, recovery of pteroylglutamic acid added in two different concentrations to five different whole blood samples was 97.0 +/- 1.9 S.E. % and 106.1 +/- 4.7 S.E. % respectively. The coefficient of variation of the assay was between 11.2 and 15.0%. Haemolysates were best stored deep frozen, showing no significant loss of L. casei activity for three to five months at -20 degrees C. On the other hand, non-haemolysed blood samples were best stored at 4 degrees C. when there was no loss of activity for seven to 10 days. Experiments confirmed that plasma is necessary for the maximum release of red cell L. casei activity, and showed that only small amounts of plasma are necessary; folate- and B(12)-deficient plasma released slightly lower L. casei activities from red cells than did normal plasma. The red cell folate levels of 40 healthy normal subjects ranged from 160 to 640 mmug. per ml. of packed red cells. One hundred and twenty patients with subnormal serum folate levels due to idiopathic steatorrhoea, nutritional folate deficiency and Crohn's disease, partial gastrectomy, myelosclerosis, and polycythaemia vera were studied. Red cell folate levels were subnormal (range from 7 to 143 mmug. per ml.) in 40 patients with megaloblastic anaemia, the lowest levels occurring in the most anaemic patients. Subnormal red cell folate levels also occurred in 23 (29%) of the 80 non-anaemic patients. There was a good correlation between red cell folate level and severity of folate deficiency assessed by polymorph nuclear lobe counts, and, in the non-anaemic patients bone marrow morphology. It is concluded that, in the absence of B(12) deficiency, the red cell folate level is a precise guide to the severity of folate deficiency. Patients with serum folate levels less than 3.0 mmug. per ml. almost always had megaloblastic anaemia or obvious morphological changes of folate deficiency. In patients with borderline serum folate levels (3.0-5.9 mmug. per ml.) haematological changes varied widely. The degree of change correlated with the red cell folate level in these patients. The formiminoglutamic acid (Figlu) test was positive (range 20-660 mg. excreted in eight hours) in all 30 patients with megaloblastic anaemia due to folate deficiency tested and also in 17 (31%) of 54 non-anaemic patients who were folate deficient. The amount of Figlu excreted paralleled the red cell folate level in both the anaemic and non-anaemic, folate-deficient patients tested. Figlu excretion, like the red cell folate level, appeared to be a satisfactory index of tissue folate stores. In 46 patients with pernicious anaemia, the red cell folate levels ranged from 26 to 396 mmug. per ml., 29 (63%) of them having subnormal levels. The ratio of mean red cell to mean serum folate level, 13.0:1, was lower than that of normal subjects. As in folate deficiency the patients with the lowest haemoglobin concentrations had the lowest red cell folate levels. Figlu was positively excreted in 10 (59%) of 17 patients with pernicious anaemia tested, being particularly increased in those with low red cell folate levels. Reticulocytes of patients with pernicious anaemia on treatment and with haemolytic anaemia were shown to have higher folate levels than their corresponding mature cells. It is concluded that reticulocytes in general have relatively high folate levels. |
5904978 | Folic acid deficiency in leukemia and lymphomas. | Serum folic acid levels and the urinary excretion of Figlu have been studied in patients with leukaemia or lymphomas. The results indicate that folic acid deficiency is plication of these diseases. Bone marrow examinations of those with evidence of such a deficiency frequently show megaloblastic erythropoiesis. The Figlu test appears to be a useful screening test for folic acid deficiency in patients with leukaemia or lymphomas. |
5904977 | An account of 335 cases of megaloblastic anaemia of pregnancy and the puerperium. | The incidence of megaloblastic anaemia in pregnancy and the puerperium in north Staffordshire has steadily declined as a result of prophylaxis with folic acid. In the presence of advanced folic acid deficiency and with a florid megaloblastic marrow, the anaemia is usually severe, but in many patients the disease is relatively mild and the degree of anaemia is determined more by blood loss or associated iron deficiency than by the megaloblastosis. Microscopic examination of marrow films is still the most reliable method of diagnosis, although estimation of the labile serum folate has produced a 95% correlation with the marrow findings. There are three main factors which operate in the pathogenesis of megaloblastic anaemia in pregnancy and the puerperium. First, the maternal stores of folic acid are used up by the growing foetus, and this process is accelerated in multiple pregnancies, after haemorrhage, or in women with haemolytic anaemia. Secondly, an insufficient intake of folic acid, due to poor diet in pregnancy, plays a part in many cases. The third, and possibly the most important, factor is an absorption defect. Folic acid absorption is usually impaired in established cases, and this can still be demonstrated years later in a majority of patients, when they are neither pregnant nor anaemic. More than 20% of all cases also show abnormal fat absorption. An inherited defect in folic acid absorption may also explain why certain women appear to be constitutionally predisposed to megaloblastic anaemia of pregnancy and the puerperium, as shown by the abnormal blood group distribution in these patients and by the tendency of megaloblastic anaemia to recur not only in subsequent pregnancies, but, as in six of our cases, following other kinds of stress. The significance monly associated conditions like pre-eclampsia and infection is still pletely understood. Although the treatment of megaloblastic anaemia is simple and effective, the main emphasis should be placed on prophylaxis by administering folic acid to all pregnant women. |
5904979 | Correlation of peripheral white cell and bone marrow changes with folate levels in pregnancy and their clinical significance. | Two hundred and thirty-eight ;megaloblastic' pregnancies are reviewed. Bone-marrow aspiration was performed in every case. Serum folate estimations were strongly suggestive of folic acid deficiency in only 34% of cases. If, however, the red cell folate was determined as well, there was an plete agreement with the changes in the erythroblasts. It is suggested that hyper-segmentation of the neutrophils in association with a diminished red cell folate level is indicative of significant folic acid deficiency. This series possibly shows a slight but statistically insignificant increase of accidental haemorrhage. No effect on birth weight or incidence of stillbirth was demonstrable. |
5904980 | Relative importance of formiminoglutamic and urocanic acid excretion after a histidine load. | A thin-layer chromatographic method for the simultaneous assessment of formimino-glutamic (Figlu) and urocanic acid excretion after loading with 15 g. histidine has been applied to 15 control subjects and to 49 selected patients. Upper limits of normal excretion were determined for urocanic acid and Figlu alone (15 mg. and 30 mg/8 hr. respectively), and for bined metabolites (40 mg./8 hr.). Of the 49 patients studied, 27 excreted total metabolites above 40 mg./8 hr.; of these 19 would have been revealed by their abnormal excretion of Figlu and 22 by their abnormal excretion of urocanic acid. Of 74 tests in the 64 subjects, urocanic acid was present in all but 27% of the tests, and in 29.8% of the tests urocanic acid was in excess of the amount of Figlu excreted. In six normal and six abnormal tests urocanic acid was the sole metabolite present. These results re-emphasize the value of estimating both histidine metabolites in tests for folate deficiency in man, and underline the greater relative importance of urocanic acid. |
5904981 | Effect of ascorbic acid on the serum folic acid estimation. | Ascorbic acid added to the basal medium increased the growth response of Lactobacillus casei in folic acid standards. The effect in the serum extracts was not marked, resulting in lowered serum folic acid estimations. However, results obtained on prolonged incubation were similar whether ascorbic acid was added or not. The presence or absence of ascorbic acid and variation of the incubation period may account for differences in reported normal ranges of serum folic acid levels. |
5904982 | Rapid microbiological assay of serum vitamin B 12 by electronic counter. | A new method of measuring the growth of Lactobacillus leichmannii is reported. Its adoption for the estimation of serum vitamin B(12) levels shortens the incubation period required to five hours at 45 degrees C. The method pared statistically with a standard method of estimation, requiring incubation at 37 degrees C., by duplicate determinations on 106 hospital patients. The significance of the apparently decreased accuracy of the new method at low serum levels is discussed, and a re-appraisal of the optimum growth temperature of Lactobacillus leichmannii suggested. |
5904983 | Plasma lactate dehydrogenase in megaloblastic anaemia. | Raised plasma lactate dehydrogenase (LDH) values were found in 26 patients with marked megaloblastic anaemia due either to vitamin B(12) or folic-acid deficiency or bination of these factors.Minor megaloblastic changes were not usually panied by plasma LDH elevation. Serial LDH estimations were as valuable as serial reticulocyte counts in assessing the response to physiological doses of folic acid and therefore in deciding whether megaloblastic anaemia is partially pletely due to folic acid deficiency. |
5904984 | Occurrence of lymphopenia in heart failure. | The incidence of lymphopenia and eosinopenia in 10 patients admitted to hospital in heart failure pared with that in 11 ;cold' admissions and 10 with acute diseases admitted via the Casualty Department. Plasma cortisol determinations were made simultaneously. A significant difference was found between the heart failure group and the ;cold' controls in respect of lymphopenia, eosinopenia, and cortisol levels. The ;acute' control patients showed an overlap with both groups. It is concluded that this lymphopenia is part of a response to stress.Seventy-two hours after admission there was no significant change in these values although the figures suggest the beginning of a return to normal. |
5904985 | Lipogranuloma of bone. | Five cases of lipogranuloma of bone are described. The possible aetiology and nomenclature of the condition are discussed. |
5904986 | Observations on the epidemiology of Candida albicans. | The carriage rates for C. albicans were found to vary for different groups of people but hospital patients appeared to have higher rates than the non-hospital population. Candida albicans was recovered more frequently from the bedding of patients than from that of school children. The variable concentration of this fungus in the air and on the bedding suggested that its presence might be related to the presence of individual patients. |
5904987 | Neonatal meningitis caused by Flavobacterium meningosepticum type F. | Two infants, one premature and one full-term, died from meningitis due to Flav. meningosepticum type F. Careful bacteriological studies are required to prevent possible confusion with other Gram-negative bacilli which may cause meningitis in this age group. |
5904988 | Disinfection of heat-sensitive material by low-temperature steam and formaldehyde. | Steam under subatmospheric pressure at temperatures below 90 degrees C. rapidly killed nonsporing organisms after air had been removed by a high-vacuum pump. Most bacterial spores were killed but small proportions of the populations were very resistant. The destruction of spores was not logarithmic. The addition of formaldehyde vapour to the steam greatly increased its sterilizing power, with deep penetration into fabrics and destruction of spores. Penetration into wide tubes was good, but was poor in narrow tubes. Most fabrics, plastics, and instruments were unharmed. Low-temperature steam with formaldehyde is probably as efficient a sterilizing agent as ethylene oxide. |
5905238 | The release of specific bactericidal antibodies by endotoxin. | Studies presented in this report are concerned with the effect of endotoxin upon the release of bactericidal antibodies as determined by the agar plaque technique. We found that shortly after the injection of mice with small amounts of endotoxin the number of plaque-forming cells in the spleen was substantially reduced and remained low for about 12 hr. At the same time the titer of specific bactericidal antibodies in the circulation was increased, 6-mercaptopurine was shown to be an effective suppressor of the immune response by inhibiting the multiplication of bactericidin-forming cells. However, administration of this drug did not modify the initial responses of antibodies and plaque-forming cells to endotoxin. Thus, we postulate that endotoxin does not induce destruction and subsequent reconstitution of bactericidin-forming cells, but that the observed changes represent a release of preformed antibodies petent cells. For a limited time, thereafter, these cells e inactive, but soon resume their normal function of releasing bactericidal antibodies. |
5905239 | An antiviral substance from Penicillium funiculosum. IV. Inquiry into the mechanism by which helenine exerts its antiviral effect. | 1. Helenine injected intraperitoneally 24 hr prior to a regularly fatal dose of Semliki Forest virus saves most of the mice to which it is administered. 2. Mice saved by helenine develop no viral immunity and regularly succumb when rechallenged 2 wk later with the same dose of virus from which they were originally saved. 3. The time during which helenine is optimally effective in protecting mice from death by Semliki Forest virus covers a period of approximately 36 hr beginning after about 12 hr and extending to 48 hr before virus infection. When periods of less than 12 hr, or more than 48 hr, elapse between the time of helenine administration and virus inoculation, its protective effectiveness diminishes progressively. 4. Repeated injections of helenine at 2- or 3-day intervals, if continued long enough, exhaust the capacity of a host to respond favorably to helenine administered 24 hr before virus inoculation. 5. Helenine injections at intervals of 4, 3, and 2 wk before its administration 24 hr prior to infection do not decrease the effectiveness of this final dose in protecting mice from fatal infection by the virus. The experimental results here reported indicate that, as suggested by the findings of earlier work, helenine does not act directly as an antiviral substance, but instead exerts its effect through some substance that it induces the host to elaborate. The nature of this induced antiviral substance is as yet unknown though, to judge from the failure of spared mice to acquire viral immunity, it appears to act at a stage in viral replication prior to that at which antigenic viral protein is produced. The findings with helenine and those thus far reported for interferon afford no factual basis for judging the relationship of the two, if any. |
5905241 | The role of the microbial flora in uremia. II. Uremic colitis, cardiovascular lesions, and biochemical observations. | Uremic colitis of varying severity occurred in the majority of conventionalized rats dying after removal of both kidneys, but was not found in uremic conventionalized and germfree rats sacrificed preterminally, or in germfree and limited-flora rats dying from uremia, or in any of the controls. The lesions were restricted to the cecum and their incidence and severity paralleled a shorter duration of survival. Cardiovascular damage including focal myocardial necrosis and calcification and patchy aortic and coronary calcification were observed in uremic rats regardless of their microbial status. These lesions had a higher incidence, developed more rapidly, and were more severe in the germfree and limited-flora rats than in the conventionalized animals. The presence or severity of the lesions, however, did not correlate with survival time of rats dying from uremia or with total plasma calcium and inorganic phosphorus levels of individual animals. Generalized necrotizing arteritis was not observed. Wound healing was poor in all uremic rats regardless of microbial status. Focal infection was noted in a few conventionalized rats dying from uremia, did not correlate with survival time, and was absent in all other groups. Comparison of biochemical findings between uremic germfree and conventionalized rats show a higher blood urea nitrogen and elevated plasma indoxyl sulfate in the presence of a microbial flora and a greater amount of plasma inorganic phosphorus in its absence. Uremia resulted in a decrease in hematocrit and increase in plasma and muscle potassium that were similar for germfree and conventionalized rats. Plasma and muscle sodium, total plasma calcium, glucose, and total protein were essentially unchanged by microbial status or uremia. Because the foregoing differences in the metabolic and histopathologic changes of uremia are linked to the known difference in microbial status of the fasting bilaterally-nephrectomized rats that were studied, they are a tangible indication of ways by which the indigenous microbial flora and position may affect the course of acute uremia. |
5905240 | Immunochemical study of antigenic specificity in delayed hypersensitivity. V. Immunization with monovalent low molecular weight conjugates. | Hapten-specific delayed hypersensitivity was produced by immunization of guinea pigs with arsanilic acid conjugated to N-acetyltyrosine or other small aromatic molecules. Such hapten-specific delayed sensitivity could be passively transferred by peritoneal exudate cells. While a conjugate made from a polymer of D-amino acids was ineffective in producing sensitization, the conjugate made with D-tyrosine was effective, suggesting that the inability of D-amino acid polymers to be broken down by enzymes might be bypassed by use of the monomer. The effectiveness of such monomers in producing delayed sensitivity, but not antibody production, is consistent with a hypothesis that different types of antigenic determinants are involved in the production of each. |
5905242 | Immunologic competence of thoracic duct cells. I. Delayed hypersensitivity. | Delayed hypersensitivity was produced in donor Lewis rats by sensitization with soluble protein antigens emulsified plete Freund's adjuvant. Cells of their thoracic duct lymph were collected for varying periods of time and transferred intravenously to isogenic Lewis recipients. With this model the following conclusions were reached: 1. Delayed hypersensitivity was transferred by thoracic duct cells. 2. The longer the drainage of the thoracic duct, the fewer cells were needed to achieve a successful transfer. With continuing drainage the proportion of small lymphocytes decreased and large cells increased. There was, therefore, a better correlation between successful transfer of delayed hypersensitivity and the number of large cells transfused than between positive skin reactions and transfer of small lymphocytes. 3. Prolonged fistula of the thoracic duct did not diminish the skin reaction of sensitized donors to specific antigen. 4. Delayed hypersensitivity was elicited in recipients 3 wk after transfer of sensitized cells. There was evidence that delayed hypersensitivity was enhanced in recipients, possibly because of prior skin testing. 5. Total body X-irradiation abolished the lesions of passively transferred delayed hypersensitivity. Recovery of positive skin tests was observed 19 to 20 days later. 6. The lesions of delayed hypersensitivity were probably mediated by cells. There was no evidence that a circulating high affinity antibody played a role in this type of immunologic reaction. |
5905243 | The influence of cortisone on experimental viral infection. VI. Inhibition by hydrocortisone of interferon synthesis in the chick embryo. | The initial observations that cortisone may act as an inhibitor of viral interference (11, 4) are now explicable as an inhibitory effect on interferon synthesis. The suggestion that the action of interferon is also inhibited by cortisone or its analogues (6) has not been confirmed in a plaque reduction type of interferon assay system in which autointerference by the challenge inoculum is a lesser problem. In this respect, the present results are in accord with those obtained by DeMaeyer and DeMaeyer (8) with hydrocortisone in a system in which a low multiplicity (0.1) Sindbis virus infection in monolayer culture was employed with cytopathic effect (CPE) as an end-point. It has been shown that hydrocortisone is restrictive to the synthesis of interferon induced by inoculation of either infective or inactivated virus into the chick embryo, and that this inhibitory effect is temporary. However, in another study in the chick embryo, three spaced injections of hydrocortisone (0.25 mg/dose) prevented the appearance of detectable interferon during the entire 64 hr observation period following inoculation of 10(3.3) EID(50) of Lee virus (12). The importance of explicit definition of experimental conditions in assessing hormonal effects on infection is illustrated by the capacity of hydrocortisone either to inhibit or increase interferon synthesis in vitro, depending on the proportion of inactivated and infective virus in the inoculum employed, and the time at which interferon is measured. As suggested previously, it is not unlikely that similar shifts in hormone-virus-interferon balance may operate in vivo to influence the e of infection. |
5905245 | The state of hemoglobin in sickled erythrocytes. | Electron microscopic and other evidence have provided support for the hypothesis that the sickling phenomenon is due to the intracellular formation of long slender crystals of reduced sickle hemoglobin. The rapid growth of these crystals causing tenting of the cell membrane is responsible for the bizarre distortion of the erythrocytes and presumably for the disease itself. |
5905244 | The influence of cortisone on experimental viral infection. VII. Kinetics of interferon formation and its inhibition with hydrocortisone in relation to viral strain and virulence. | parative study was undertaken of the pathogenesis of infection of the allantoic sac of the chick embryo with three influenza viruses of differing virulence, and of the influence of hydrocortisone on the course of infection. Judged on the basis of earlier onset and greater degree of inflammatory response and diminished survival time of infected embryos, Mel. and Lee viruses were markedly more virulent than PR8, despite the earlier appearance of virus in PR8-infected embryos. Interferon appeared first and in greater quantity in the allantoic fluid of Lee-infected embryos and latest with PR8 infection. Thus, there was no correlation of avirulence and better interferon production with the viruses under study in the present system. Furthermore, evidence obtained suggested that Lee virus ("virulent") was most susceptible to interferon action, and also that viral synthesis in the chorioallantoic membrane with PR8 ("avirulent") persisted after the appearance of interferon. The injection of hydrocortisone within 2 hr of the initiation of infection delayed the synthesis of all three viruses; had no significant effect upon the inflammatory response; and transiently inhibited the synthesis of interferon, while prolonging the survival of Lee- and Mel.-infected embryos. Late administration of hydrocortisone suppresses both the inflammatory response and the production of interferon. Only in the case of Lee virus infection did hydrocortisone administration lead to augmentation of final yields of virus with the low infection multiplicity employed in the present experiments. It is postulated that Lee virus is a better inducer of interferon because its infectivity in vivo is more rapidly inactivated. As a consequence synthesis of Lee virus is more under the control of endogenous interferon than is the case with PR8 or Mel. virus. Therefore, inhibition of interferon synthesis with hydrocortisone has a greater influence on final yields of Lee virus. |
5905948 | Naturally occurring toxic factors in plants and animals used as food. | ponents of natural foodstuffs are discussed, with special reference to lathyrogens, pressor amines, azoxyglycosides, and labile pounds. The osteolathyrogen, gamma-glutamyl-beta-aminopropionitrile, in sweet pea (Lathyrus odoratus) seeds induces skeletal deformities and aortic rupture, probably by interfering with normal maturation of collagen fibres. Neurolathyrism in man may be caused by beta-N-oxalyl-L-alpha,beta-diaminopropionic acid, a neurotoxin recently identified in Lathyrus sativus seeds. Histamine, tyramine, noradrenaline, serotonin and other pressor amines occur in fruits and fermented foods such as bananas, pineapples, cheese and wine. Consumption of such foods by patients taking monoamine oxidase-inhibiting drugs (e.g. tranylcypromine) may produce serious hypertensive crises. Cycad nuts, widely used as human food in tropical and subtropical areas, contain a potent carcinogen, methyl azoxymethanol, which is more or less removed prior to use by leaching in water. Consumption of plants of the onion, cabbage and cress families introduces into the body such toxic chemicals as benzyl cyanide, goitrin and thiocyanates. The lachrymatory substance in onions is propenyl sulfenic acid. |
5905949 | Food-borne bacterial toxins. | Food poisoning caused by the ingestion of preformed bacterial toxins is considered in relation parative symptoms, procedures for extraction and purification of the causal toxins, their chemistry, serology, assay procedures and pharmacology, in so far as these are known.The bacteria discussed in this context are Clostridium botulinum, C. perfringens, Staphylococcus aureus, Bacillus cereus, and Vibrio parahemolyticus. The possible roles of the enterococci, Proteus, E. coli and of unknown species, in relation to production of non-antigenic toxic substances, are discussed briefly.Requirements for prevention of the various forms of bacterial food poisoning are outlined. |
5905950 | Problems related to the use of pesticides. | Potentiation and additive effects of pesticides are considered major problems in the determination of safe daily intakes of these chemicals. Examples of potentiation between two organophosphates, such as ethyl-p-nitrophenyl benzenethionophosphonate (EPN) and malathion, delnav and malathion, and guthion and dipterex are considered. Although this type of potentiation could give rise to acute accidents, the most important point in evaluation centres on the possible effects of small amounts of pounds in the daily diet. Likewise, certain drugs of the phenothiazine type potentiate the toxic effects of organophosphates. A review of the data for both types of potentiation indicates that the consumption of raw agricultural products containing pesticides at tolerance levels constitutes a minimal hazard. A two-year rat-feeding investigation using bination of eight flavouring agents and six pesticides, at use levels and higher, did not cause a significant alteration of toxicity parison with the toxicity of the individual substances. |
5905951 | Regulatory agencies and food safety. | Prior to Confederation, food control legislation in Canada consisted of only a few simple laws governing the quality, grading, packing and inspection of certain staple foods. The Inland Revenue Act of 1875 provided the first real control in Canada over adulteration of liquor, foods and drugs. Since then, food legislation has evolved in scope plexity as the industries involved have developed, as consumers have e better informed, and as scientific advances have provided a sound basis for regulations. Present regulations under the Food and Drugs Act are intended to give consumers broad protection against health hazards and fraud in the production, manufacture, labelling, packaging, advertising, and sale of foods. This principle is well illustrated by present requirements for the control of pesticide residues, chemical additives, and the addition of vitamins to foods. In today's era of rapid technological change, application of current scientific knowledge to the food industry obviously involves the possibility of hazards to health. Regulatory agencies with responsibility for food safety must, therefore, fully utilize scientific knowledge in order to reduce the risks involved to a minimum. |
5906374 | Multiple hydrolases in bean leaves (Phaseolus vulgaris L.) and the effect of the halo blight disease caused by Pseudomonas phaseolicola (Burkh.) Dowson. | Multiple forms of hydrolytic enzymes were demonstrated in extracts of healthy bean leaves (Phascolus vulgaris L.) and bean leaves infected with the halo blight organism [Pseudomonas phaseolicola (Burkh.) Dowson] by polyacrylamide disc electrophoresis. Bean leaves contained up to 4 acid phosphatase bands, 9 esterase bands active towards alpha-naphthyl acetate, and 7 esterase bands towards alpha-naphthyl butyrate. Only low or no activity was found for alkaline phosphatase, lipase, and aminopeptidase. Two artifacts are described which were observed with the lead phosphate method for acid phosphatase and the Tween method for demonstration of lipase. After infection with the halo blight organism the major acid phosphatase of the host increased during early and decreased at later infection stages. An acid phosphatase of bacterial origin with a more neutral pH optimum could be demonstrated in infected leaves. It is suggested that the bacterial acid phosphatase plays a role in uptake of metabolites by the pathogen. Several esterase bands decreased after infection. One host band with activity towards alpha-naphthyl butyrate increased. Also the pathogen showed an esterase band with high activity towards alpha-naphthyl butyrate. |
5906375 | Light effects on the nucleic acids of excised cotton cotyledons. | The effects of light and glucose in the nutrient medium on the nucleic acid metabolism of excised 8-day cotton (Gossypium hirsutum var. Acala 44) cotyledons were determined. The rates of synthesis as affected by light and glucose were determined by brief exposures to C(14)-labeled orotic acid. The nucleic acids were fractionated by homogenizing in Tris-HCl buffer and centrifuging to obtain soluble and microsomal RNA (20,000 x g supernatant) and a particulate nucleic acid fraction (20,000 x g precipitate) or by extracting in phenol followed by 10% NaCl extraction at 100 degrees . The phenol extract was analyzed by density gradient centrifugation. Light and glucose caused parallel changes in nucleic acid levels of the various fractions, in orotic acid-6-C(14) absorption and in rates of synthesis of nucleic acids. Light and glucose appear to enhance binding of the ribosome nucleic acid so that it es less extractable in Tris-HCl buffer or phenol. The bound nucleic acids were labeled at a slightly higher rate than the total nucleic acids extracted by Tris-HCl or phenol. However, light treatment for 48 hours promoted a very high labeling rate in the soluble, low molecular weight nucleic acid as shown by density gradient centrifugation of the phenol extractable fraction.It was concluded that a part of the nucleic acid changes were brought about by light acting through the photosynthetic production of carbohydrate. This conclusion was strengthened by the observation that herbicide inhibitors of photosynthesis and limited atmospheric CO(2) concentrations partially inhibited the nucleic acid changes. However, glucose did not cause changes in nucleic acid levels as large as those caused by light and changes were observed to occur in light even though the endogenous sugar levels were maintained at a low level by the inhibition of photosynthesis with herbicides. The data indicated that light may produce changes in nucleic acid levels by other mechanisms additional to those regulating the sugar level in the tissue. |
5906376 | Methionine transport in Chlorella vulgaris. | Absorption of (35)S-l-methionine by Chlorella vulgaris was measured at concentrations that ranged from 0.1 to 10.0 mumoles/ml. A brief, rapid phase of uptake was followed by a more prolonged, slower phase that was linear only at the lowest concentrations. The radioactivity accumulated by the end of 1 hour's incubation at an exogenous level of 0.1 mumole/ml was retained by the cells despite the inclusion of 10 mumoles/ml of nonradioactive methionine in the rinse medium. As the exogenous concentration was raised, the ratio of intracellular soluble radioactivity to exogenous radioactivity decreased. Analysis of the accumulated, soluble radioactivity showed that 90% was in the form of methionine and that about 10% had been converted to pound with properties of S-adenosylmethionine. Azide and ethionine were the most effective of the inhibitors tested. |
5906377 | Comparative study of uptake and cellular distribution of Hg203-labeled phenyl-mercuric acetate and mercuric acetate by pea roots. | Uptake and cellular distribution of mercury(203) from dilute mercuric acetate or phenylmercuric acetate solutions by excised pea roots (Pisum sativum) have been investigated. The time course of uptake showed that the amount of mercury uptake was increased with the time of incubation, and was similar for inorganic mercury or phenylmercuric acetate. The trend of mercury(203) incorporation into ponents from mercuric acetate and phenylmercuric acetate differed greatly as the time of incubation increased. The concentrations of mercuric acetate and phenylmercuric acetate solutions or the temperature of incubation also affected the mercury(203) uptake as well as its cellular distribution. Longer time of exposure or higher concentration resulted in a greater mercury incorporation into mitochondrial fraction from phenylmercuric acetate than from inorganic mercury. This difference in intracellular distribution may be responsible for the degree of toxicity between inorganic mercury and phenylmercuric acetate in biological systems. |
5906378 | Deamination of 4-aminopyrimidine nucleosides by extracts of rye grass (Lolium perenne). | A deaminase specific for 4-aminopyrimidine nucleosides has been found in rye grass. Lolium perenne. The pH optimum, temperature stability, Km values and specificity was determined.A new and more accurate method for following the course of deamination is reported. This method depends on the shift in maximum absorbance wavelength of the mixture containing the 4-aminopyrimidine nucleoside and its deaminated product. |
5906379 | Studies on the formation of phycocyanin, porphyrins, and a blue phycobilin by wild-type and mutant strains of Cyanidium caldarium. | The synthesis of chlorophyll a and the bile-pigment and protein moieties of phycocyanin were arrested in illuminated cells of Cyanidium caldarium, strain III-D-2, incubated with chloramphenicol, ethionine, p-fluorophenylalanine, and p-chloromercuribenzoate. Pigment synthesis was similarly retarded in illuminated cells provided with nutrient medium lacking nitrogen.Porphobilinogen, porphyrins, and a blue phycobilin were excreted into the nutrient medium by illuminated and unilluminated cells of wild-type and mutant C. caldarium strains incubated with delta-aminolevulinic acid in darkness. Pigment production from delta-aminolevulinic acid was sensitive to treatment with chloramphenicol and ethionine. Cells of C. caldarium excreted 7 red-fluorescing porphyrins into the suspending medium during incubation with delta-aminolevulinic acid. Three of these porphyrins were identified as uroporphyrin III, coproporphyrin III, and protoporphyrin on the basis of their spectral properties and by paper chromatogaphy with standards. The blue phycobilin was characterized spectrally pared with biliverdin. The algal phycobilin displayed properties of a pigment with a violin-type structure. The phycobilin may be an immediate precursor of phycocyanobilin, the phycocyanin chromophore, or identical to it. |
5906380 | Lipid synthesis in the presence of nitrogenous compounds in Chlorella pyrenoidosa. | Acetate was incorporated by Chlorella pyrenoidosa into nonvolatile pounds (amino acids, organic acids and carbohydrates) with pH optimum between 4 and 5. Incorporation into lipid was maximal at pH 7.5. The proportion of incorporated acetate in lipid was not significantly affected by acetate concentration and chlorophyll concentration in the ranges tested. Illumination of Chlorella during acetate metabolism increased the synthesis of lipid with itant decrease in the synthesis of pounds. Nitrate and ammonium ions had essentially no effect on acetate metabolism. Inhibition by nitrite was greater on the synthesis of lipid. Illumination reversed the gross inhibition by nitrite, but altered the distribution of incorporated label in favor of the pounds. |
5906381 | Sap concentrations in halophytes and some other plants. | Freezing point depression in xylem sap of mangroves was found to range from 0.05 to 0.5 degrees , in desert plants from 0.01 to 0.16 degrees . In crush juices from leaves of Batis and Salicornia, 90% or more of the freezing point depression was made up of sodium and chlorine ions; in mangroves they constituted 50 to 70%, the rest probably being organic solutes. Plants growing in seawater have -30 to -60 atmospheres pressure in the xylem sap. As shown earlier, at zero turgor pressure the intracellular freezing point of the parenchyma cells matches closely the negative pressure in the xylem sap. This agrees with the present data, that the fluid which exudes from the xylem by applying gas pressure on the leaves is practically pure water; freezing point is rarely above 0.01 to 0.02 degrees . To perform this ultrafiltration, the plasma membrane is subjected to a hydrostatic pressure gradient which in some cases may exceed 100 atmospheres. |
5907284 | Electron microscopic autoradiography of rabbit reticulocytes active and inactive in protein synthesis. | Electron microscopic autoradiography indicates that only a fraction of ribosome-containing reticulocytes (from phenylhydrazine-treated rabbits) is capable of active protein synthesis in vitro. Ribosomes, and, indeed, polyribosomes, do not appear to limit the rate of protein synthesis. |
5907285 | Polysome morphology: evidence for endocrine control during chick embryogenesis. | Surgical removal of the pituitary gland had little apparent effect on the distribution or morphology of skin and feather polysomes in chicken embryos incubated for 12 days. However, polysome patterns obtained from 15-day-old hypophysectomized embryos differed markedly from those of their controls. In addition, a tetrad-shaped polysome, characteristic of the 158S peak of the 12-day-old embryo but not of the 15-day-old control, is still retained in the operated embryo at 15 days. Therefore, it appears that after day 12 of embryogenesis the structure of the four-ribosome polysome from skin and feathers is contingent on a functional hypophysis. |
5907286 | Lobster hemocyanin: properties of the minimum functional subunit and of aggregates. | Lobster hemocyanin dissociates into a functional subunit of 68,000 to 70,000 molecular weight when Ca(2+) ions are removed from an alkaline solution of low ionic strength. Succinylation results in a further dissociation into two nonfunctional subunits of approximately 34,000 to 35,000 molecular weight. Amino acid analysis and tryptic peptide patterns indicate that the functional subunit posed of at least two polypeptide chains which are similar. |
5907287 | Actinomycin D: inhibition of respiration and glycolysis. | Actinomycin D inhibited respiration and anaerobic glycolysis of human leukemic leukocytes and lowered the adenosine triphosphate content of the cells. Inhibitory effects on respiration and on RNA synthesis could not be dissociated from one another over a wide range of drug concentrations. Actinomycin D also impaired protein synthesis, probably by decreasing the availability of adenosine triphosphate and by inhibiting messenger RNA. |
5907288 | Transport of sugars and amino acids in the intestine: evidence for a common carrier. | D-Galactose, L-arginine, and their respective actively transported analogs are petitive inhibitors of the active transport of neutral amino acids in the small intestine of hamsters. Since the aforesaid classes pounds are all transported by similar, sodium-ion-dependent mechanisms and elicit countertransport of each other, all may share mon, polyfunctional carrier in which a series of separate binding sites, namely, one each for sugars, neutral amino acids, basic amino acids, and Na(+) are joined together, as in a mosaic. |
5907289 | Visually evoked potentials: amplitude changes with age. | Visually evoked potentials of 215 subjects, aged 1 month to 81 years, were studied. Amplitudes of waves in the first 250 milliseconds of the response changed markedly with age. In responses recorded from the occiput, there was a rapid increase in amplitude reaching a maximum in the 5- to 6-year-old group, with means of amplitudes at this age being about twice as large as means of some older age groups. With children 7 years and older there was a rapid decline in amplitude until ages 13 to 14, when an abrupt increase in amplitude appeared. Amplitude appeared to stabilize at about age 16. In older subjects, mean age 60 and beyond, significant changes were noted in the ponents of the response. |
5907290 | Acrylamide-gel electrophorograms by mechanical fractionation: radioactive adenovirus proteins. | A mechanical fractionator was developed to produce electrophorograms by extrusion of polyacrylamide gels through a narrow orifice in a continuous, sequential stream. The system permits separation of uniform fractions free of zone distortion. An electrophorogram of radioactive type-2 adenovirus proteins so fractionated gave a pattern in excellent agreement with the pattern obtained by laborious manual sectioning and in agreement with the pattern obtained on a replicate gel stained with Coomassie brilliant blue R250. The adenovirus particle yielded about ten resolvable ponents in unequal amounts. Like picornaviruses, these icosahedral animal viruses have multiple ponents in the viral coat. |
5907291 | Polyribosome disaggregation during metaphase. | Polyribosomes as examined by both sucrose-gradient analysis and electron microscopy disaggregate during metaphase in both normal HeLa cells and those arrested in metaphase by treatment with colchicine. |
5907320 | Rheumatoid arthritis--atlanto-axial subluxation and its clinical presentation. | The clinical picture, radiological findings and treatment of 22 patients with atlantoaxial subluxation and rheumatoid arthritis are described. This lesion, untreated, may result in damage to the spinal cord, paresis or sudden death. Occipital headache, present in 13 of 22 patients, was often aggravated by working with the head in forward flexion. Paresthesias were present in six patients. The spine of the axis was often prominent. In three patients there was objective evidence of pression with sensory and/or pyramidal signs. In eight the lesion was asymptomatic and discovered by routine lateral radiography in flexion, the position of maximum subluxation.Conservative treatment involved the continuous use of a cervical collar to limit neck flexion. This usually relieved subjective symptoms including headaches. Successful surgical fixation was performed in two individuals. Surgical indications included acute or chronic pression or severe symptoms unrelieved by a collar. |
5907321 | The emotional needs of children in hospital. | Hospitalization of a child for physical reasons brings with it separation from parents, siblings and familiar surroundings, as well as the probability of subjection to frightening and painful procedures. Unless steps are taken to prevent or modify the resultant stress, behavioural disturbances may arise and may result in permanent damage to the developing personality. |
5907470 | Hepatic fibrosis in a child possibly due to prolonged methotrexate. | A case is described in which marked hepatic fibrosis probably resulted from the prolonged treatment of acute leukaemia with methotrexate. |
5907581 | Selection of students for admission to medical school: A two-class decision approach. | The validity coefficient alone does municate sufficient information to estimate the errors in decisions to accept or reject candidates. By means of probability theory, it is demonstrated how information concerning errors in decisions may be estimated. With estimates of the frequencies of correct and incorrect decisions and the costs of such decisions, a utility index was defined, for which a minimum was sought as a function of the entrance requirement. Under the analytic criterion defined for utility, it was possible to determine for a number of cost systems the entrance score which would, in the long run, reduce losses to a minimum. The application of the model is illustrated using empirical data and hypothetical cost systems. For these data entrance requirements were determined according to the criterion in addition to selection ratios and probabilities of success. |
5907582 | A survey of women graduates from a Canadian medical school. | Information was obtained from 104 of 106 surviving women medical graduates of the University of Western Ontario in a study designed to determine subsequent working careers and related factors. Of those who had graduated six or more years before this study 85% were engaged in medical work (66% full-time and 19% part-time). General practice, psychiatry and preventive medicine were the leading categories of work. Childbearing was the most important determinant of occupational status. Fewer of the women who had borne children were currently engaged in medical work than were either single or childless married women. The apparent contribution of other factors to working status arose from their correlation with child-bearing. Comparison with other studies suggests that the percentage of female graduates doing medical work is substantially higher than in Britain and about the same as in the United States. |
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