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Biomedical subjects

S Cohen

Publications and source records attributed to S Cohen.

At least 1,063 records · Page 59Linked to original sources
PubMed1977

Hormonal factors concerned with liver regeneration.

Hepatic regeneration in partially hepatectomized, eviscerated rats, and survival in mice infected with lethal doses of murine hepatitis virus, are both strikingly promoted by combined administration of insulin and glucagon. These two hormones, although potent promotors, fail as initiators of hepatocyte proliferation in animals with intact liver, which suggests a requirement for additional factors, probably derived from non-portal-splanchnic organs. We now find that continous intraperitoneal infusion of epidermal growth factor (EGF) initiates DNA synthesis, as determined by incorporation of [3H] thymidine, in livers of adult rats in vivo. The rise in DNA labelling, which is small with EGF alone, is augmented by addition to the infusion of either glucagon or insulin. This is in agreement with reports on adult hepatocytes in culture. Whether EGF has a physiological role in regulating liver growth under normal conditions in vivo remains to be determined.

Age Factors↗
PubMed1977

Tolerance to marijuana: heart rate and subjective "high".

In a 94-day supervised study of 30 subjects smoking marijuana, with drug-free periods interspersed, mean heart rate and subjective "high" decreased over the smoking period. Light smokers had greater chronotrophic and subjective effects than heavy smokers, but both demonstrated evidence of tolerance. Cumulation and minor withdrawal effects were noted.

Adult↗
PubMed1977

Human colonic myoelectric activity in response to prostigmin and the gastrointestinal hormones.

Colonic myoelectric activity was determined using a mucosal clip electrode in normal human subjects, in the basal state and following the administration of prostigmin, pentagastrin, cholecystokinin, or secretin. Slow-wave activity was present 49 +/- 3.0% of the recording time and occurred at two frequencies, 6.5 +/- 0.1 cycles/min and 3.5 +/- 0.1 cycles/min, in the rectum. Spike potentials were infrequent in the basal state. Prostigmin, pentagastrin, or cholecystokinin did not affect the slow-wave activity or frequency, but these agents significantly increased the number of spike potentials (P less than 0.05). Secretin had no effect on myoelectric activity. The electrode system was tested in the cat and showed excellent correlation of the myoelectric activity between the mucosal clip electrode and a serosal electrode. These studies indicate: (1) a mucosal clip electrode provides an accurate method of recording colonic myoelectric activity when compared to a serosal electrode in the cat; (2) in man, slow-wave activity is present only intermittently and exists at two frequencies, approximately 6 cycles/min and 3 cycles/min; (3) gastrointestinal hormones and prostigmin increase spike potential discharge without altering slow-wave activity or frequency.

Adult↗
PubMed1977

Mechanisms of malarial immunity.

Immunity to malaria in many species, including man, is acquired only after long exposure to infection and is associated with chronic low-grade parasitaemia. Vaccination of Rhesus monkeys with P. knowlesi merozoites in FCA induces sterilizing immunity which is species specific. Merozoite-blocking (inhibitory) antibody usually correlates with clinical immunity and protection can be passively transferred with immune sera. However, vaccination using adjuvants other than FCA may induce inhibitory antibody without clinical protection. In addition, vaccinated animals usually become susceptible to challenge 4 to 5 weeks after splenectomy, although inhibitory antibody levels are not reduced. These observations indicate that immunity induced by merozoite vaccination involves merozoite blocking (inhibitory) antibody and also specific antibody or immune complexes acting synergistically with cytotoxic splenic cells stimulated by FCA. During natural infection on the other hand soluble circulating antigens, partly derived from the merozoite coat during red cell penetration, are produced and these may block immune effector mechanisms and promote parasite survival.

Animals↗
PubMed1977

Cervical teratoma in infants and children.

Teratoma of the neck in infants and children, though uncommon, should be included in the differential diagnosis of neck masses in this age group. Radiographic examination should be an integral part of the patient's evaluation and may allow a definitive diagnosis. The clinical and radiologic aspects of this tumor are discussed. The finding of a soft tissue mass indenting the trachea and containing calcification should indicate the diagnosis of teratoma.

Calcinosis↗
PubMed1977

Mutations in prophage phi11 that impair the transducibility of their Staphylococcus aureus lysogens for methicillin resistance.

Methicillin resistance (mec) is not transduced into Staphylococcus aureus 8325-4, but is transduced into this host after it has been lysogenized with phage phi11 and has acquired the penicillinase plasmid pI524 by a separate transduction (Cohen and Sweeney, 1970, 1973). Strain 8325-4 is competent for transformation of typical plasmid or chromosomal markers and for mec only if it is lysogenic for phi11 or a related prophage (Sjöström et al., 1974, 1975). A mutant strain of phi11 that was temperature sensitive (Ts) for vegetative multiplication did not mediate competence for transformation of its 8325-4 lysogen if the lysogen had been grown at a nonpermissive temperature (Sjöström and Philipson, 1974). We isolated four Ts mutants of phi11 that did not mediate transducibility of their 8325-4(pI524) lysogens for mec after growth at nonpermissive temperatures (40 to 42 degrees C). Transduction of typical plasmid or chromosomal markers was not affected. These phi11-Ts mutants mediated normal competence of their lysogens for transformation of a tetracycline resistance plasmid. Similarly, phi11-Ts mutants that rendered their lysogens temperature sensitive for transformation did not depress the frequency of transduction of mec. These two types of phi11-Ts mutants fell into two different genetic complementation groups that differed in the physiology of deoxyribonucleic acid synthesis and in the time of expression of the mutations during a single-burst growth cycle at a nonpermissive temperature. A virulent mutant of phi11, which plaqued with 100% efficiency on 8325(phi11), also failed to condition strain 8325-4 for transducibility of mec but retained the ability to confer competence for transformation of a tetracycline resistance plasmid. Different genetic loci and physiological functions are involved in phi11 mutations that affect transducibility of mec and those that affect competence for transformation of markers generally in S. aureus 8325-4.

DNA, Viral↗
PubMed1977

Influence of vagal cooling on esophageal function.

Experiments were performed on adult opossums to determine the effect of decreased vagal activity on the esophageal peristalsis and lower esophageal sphincter (LES) relaxation associated with pharyngeal stimulation (PS) and esophageal balloon distension (ED). The cervical vagi were exposed and cooled (individually and bilaterally) to 3 degrees C using Dry Ice and alcohol-chilled saline. Unilateral vagal cooling had no effect on the esophageal peristalsis or LES relaxation associated with PS or ED. Similarly, bilateral vagal cooling did not alter the peristalsis and sphincter relaxation induced by ED. Bilateral vagal cooling, on the other hand, significantly decreased the incidence of peristalsis and the sphincter relaxation associated with PS. Studies were also performed to examine the effect of unilateral and bilateral vagotomy of esophageal function. Neither right nor left cervical vagotomy affected esophageal peristalsis or LES relaxation, regardless of the model of stimulation. Bilateral vagotomy, however, diminished the esophageal response to PS but was without effect on the peristalsis and LES relaxation produced in response to ED. From the studies we condlude: 1) the vagus nerve is of primary importance in regulating the esophageal response to PS, and 2) local neuromuscular factors within the esophageal wall appear sufficient to initiate and maintain an esophageal response to distension.

Animals↗
PubMed1977

Migrating action potential complex of cholera: a possible prostaglandin-induced response.

Distal ileal loops of New Zealand white rabbits exposed to cholera toxin demonstrated the presence of a highly organized myoelectric pattern defined as the migrating action potential complex (MAPC). We investigated the mechanism by which cholera enterotoxin stimulates MAPC activity. Certain anti-inflammatory drugs have altered the secretory component of cholera diarrhea. We investigated effects of these anti-inflammatory drugs on the MAPC. Indomethacin, 5.0 mg/kg iv, abolished all MAPC activity. Indomethacin, 1.5 mg/kg iv, or acetylsalicylic acid, 150 mg/kg given intragastrically, altered propagation velocity and at times its direction of propagation, but did not abolish the MAPC. An infusion of prostaglandin F2alpha, 2 microng/kg per min intraluminally, induced MAPC activity similar to that of the cholera complex. Indomethacin, 5.0 mg/kg iv, produced no significant changes in number of complexes or propagation velocity. These observations suggested that inhibition of the cholera complex by indomethacin may result from the alteration of prostaglandin synthesis and that prostaglandins may initiate the motility component of cholera diarrhea.

Action Potentials↗
PubMed1977

The effect of the alkaline tide on serum-ionized calcium concentration in man.

The effect of the gastric alkaline tide on serum-ionized calcium levels was determined in human subjects. Gastric acid seretion was stimulated by a standard steak meal, human synthetic gastrin, and betazole hydrochloride. Ionized calcium levels fell to a similar extent after each stimulus. The mean decrease in calcium ion concentration in all experiments was 5.4% of the basal concentration. The fall in serum calcium ion concentration was highly correlated with the rise in serum pH. We speculate that increased formation of calcium bicarbonate complex in the serum as well as increased binding of ionized calcium by serum protein accounts for the surprisingly large effect of the alkaline tide on serumionized calcium levels.

Acid-Base Equilibrium↗
PubMed1977

Bacteremia and the barium enema.

To investigate the possible association of bacteremia with barium enema examinations, blood samples were obtained from 42 patients before and at 5, 10, and 20 min after administration of the enema. Patients with fever or symptoms suggestive of inflammatory bowel disease were not included in the study; neither were patients who had received antimicrobiotic medication during the preceding 3 months. Pour-plate blood cultures showed no bacteremia due to enteric organism in the 42 patients-a result at variance with previously published reports.

Barium Sulfate↗