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Biomedical subjects

S Cohen

Publications and source records attributed to S Cohen.

At least 1,009 records · Page 56Linked to original sources
PubMed1978

[Interaction of epidermal growth factor with human fibroblasts in culture: an autoradiographic study at the ultrastructural level].

The potent mitogen epidermal growth factor (EGF) binds to specific receptors on human fibroblasts. In the present study we have used a quantitative EM autoradiographic approach to visualize the events involved in the binding process. When 125I-EGF is incubated at 4 degrees C for 120 min, labeled EGF primarily localizes to the plasma membrane of the fibroblast but when incubated at 37 degrees C for 120 min., over 2/3 of the labeled material is internalized by the cell. The internalized radioacitivity is primarily localized to lysomes. These studies demonstrate a temperature-dependent internalization of EGF following initial binding to specific plasma membrane receptors.

Cell Membrane↗
PubMed1978

Colonic myoelectrical activity in irritable-bowel syndrome. Effect of eating and anticholinergics.

To determine the effect of a standard meal on colonic myoelectrical and motor activity in the irritable-bowel syndrome and to determine the effect of a single dose of an oral anticholinergic drug (clidinium bromide) on this response, we studied 10 patients. These patients showed a prolonged increase in both colonic spike (P less than 0.05) and motor activity (P less than 0.05) after eating as compared to normal subjects. Clidinium did not affect the frequency of colonic slow waves or the basal colonic spike and motor activity. However, the anticholinergic reduced the prolonged postprandial colonic spike and motor response in the patients and also reduced the postprandial increase in colonic contractions at 3 cycles per minute (P less than 0.05). These studies indicate that patients with the irritable-bowel syndrome show an abnormally prolonged post-prandial increase in colonic spike and motor activity. An anticholinergic drug reduces the duration and the magnitude of this abnormal colonic response.

Administration, Oral↗
PubMed1978

Impact of aftercare services on recidivism of mental hospital patients.

The subjects in this study were 129 patients released within a 2-year period from a large state hospital to a three-county area. Patient information on demographic, inhospital, and posthospital variables and the extent of participation in an aftercare program was collected from existing records. The relationship between the community support system available to the patient and recidivism was determined. Three criteria of recidivism were used: readmission within 1 year following discharge, number of days in the community within 1 year following discharge, and number of days to first readmission. No single predictor was adequate in predicting hospital readmission. When the effects of confounding variables were eliminated using multiple-regression techniques, the amount of aftercare received was an important factor in predicting recidivism. However, current situational factors appeared to be more important predictors of recidivism than receipt of aftercare services.

Adolescent↗
PubMed1978

A new approach to teaching normal human growth and development. The role of clinical simulations as a teaching and evaluation device for preclinical medical students.

A new approach to teaching Normal Growth and Development to preclinical medical students is described. By using specially constructed multidisciplinary clinical simulations as training and evaluation devices, students were gradually and simultaneously exposed to: (1) subject matter; (2) the concept of multidisciplinary health care delivery; and (3) the objectives, strategies, and techniques of problem solving and diagnostic reasoning that characterize experienced physicians. The course, designed by a child psychiatrist and medical educators, was taught by a multidisciplinary teaching team drawn from faculty and health care representatives. Student evaluations of the course were favorable.

Consumer Behavior↗
PubMed1978

Antigenic analysis of sequential erythrocytic stages of Plasmodium knowlesi.

The antigenic composition of sequential erythrocytic stages of Plasmodium knowlesi has been compared by crossed immuno-electrophoresis using a pool of immune rhesus monkey antiserum. Eleven major parasite antigens have been identified; 9 are stage-independent, and 2 stage-dependent. Differences in the relative amount of the stage-independent antigens have been demonstrated and quantified. The distribution of antigens between parasites and schizont and infected red cell membranes has been examined. Only 6 of the 11 parasite antigens were exhibited by a schizont membrane preparation, all these antigens were also expressed by the intracellular parasite. Antigens exclusive to the schizont membrane were not demonstrated.

Animals↗
PubMed1978

Epidermal growth factor: morphological demonstration of binding, internalization, and lysosomal association in human fibroblasts.

Using a quantitative electron microscopic autoradiographic technique, we have localized the initial binding step of 125I-labeled epidermal growth factor (125I-EGF) to the plasma membrane of the human fibroblast. After initial binding, labeled EGF is internalized progressively by the cell in a time- and temperature-dependent fashion; when cell-associated radioactivity comes to steady state, approximately 1/3 of the autoradiographic grains are related to the plasma membrane and approximately 2/3 have been internalized. Under these conditions the internalized grains are almost exclusively related to lysosomal structures. When 125I-EGF associates with the cells for 2 hr at 4 degrees or 2 min at 37 degrees, 34% of grains localize to coated regions of the membrane. These coated regions make up less than 2% of the membrane surface. These data directly confirm kinetic studies and suggest that saturable binding of EGF is followed by adsorptive pinocytosis and cellular degradation of the ligand and possibly its cell surface receptor.

Autoradiography↗
PubMed1978

Visualization by fluorescence of the binding and internalization of epidermal growth factor in human carcinoma cells A-431.

The binding and internalization of epidermal growth factor (EGF) in human epithelioid carcinoma cells (A-431), which have approximately 2.6 X 10(6) receptors per cell, has been followed with 125I-labeled EGF and by fluorescence microscopy. We have prepared a fluorescent derivative of EGF that is biologically active and retains substantial binding affinity for cell receptors. After binding of this derivative to cells at 6 degrees, the cellular borders were prominently stained and the fluorescence on the remainder of the membrane was uniform. Upon warming of these cells to 37 degrees for 10 min, the surface fluorescence diminished and randomly distributed endocytotic vesicles appeared in the cytoplasm. After 20 min at 37 degrees these fluorescent vesicles formed a perinuclear ring. The binding of EGF to the surface of these cells was also visualized by immunofluorescence using rabbit antibodies to EGF and rhodamine-labeled goat anti-rabbit antibodies. We did not detect large fluorescent clusters or cap formation in these experiments. These data provide direct confirmation of the previous biochemical data that suggested that cell membrane-bound EGF is rapidly internalized.

Biological Transport↗
PubMed1978

The pharmacology of alcohol.

The metabolic breakdown of ingested alcohol is specific for each person. Blood alcohol concentration after a given dose of alcohol depends on many factors, including the degree of tolerance developed by daily drinking. Metabolic alterations in the CNS, liver, gastrointestinal tract, endocrine system, and skin produced by acute and chronic alcohol consumption can result in a variety of disorders.

Alcoholism↗
PubMed1978

Narcotism: dimensions of the problem.

It is evident that the indirect indicators that are used to provide some estimate of heroin use trends are susceptible to distortion by variables having little to do with total heroin use. A panel of indicators, employed together, moving in the same direction, are seen as the best information available, and confidence can be placed in their implications. We have witnessed a rapid increase in the use of heroin in the decade that began in 1960. From 1970 to 1973 a decrease occurred followed by an increase in prevalence that lasted about two years. Since 1975 there appears to have been a levelling off or even a slight decrease in heroin use with a shift of higher use patterns to the West Coast. These changes are the result of many factors on both the demand and the supply sides of the equation. There is reason to believe that the curve could slope sharply upward again if substantial efforts are not made to control the quantity of available heroin, to prevent the recruitment of new users and to treat those now overinvolved with the drug. However, heroin prevalence rates will not recede to the pre-1960 level in the foreseeable future, and immediate goals include lowering them even more.

Adolescent↗
PubMed1978

Infections due to gentamicin-resistant Staphylococcus aureus strain in a nursery for neonatal infants.

An apparently homogeneous strain of Staphylococcus aureus resistant to gentamicin (Gmr), kanamycin, tobramycin, and sisomicin, but susceptible to amikacin and netilmicin, caused multiple infections in neonatal infants in a special care nursery. Nasal cultures revealed a high rate of carriage of the Gmr staphylococcus in infants without clinical infection. Segregating patients according to a modified cohort system and use of careful aseptic techniques led to apparent elimination of the Gmr strain. The resistance to aminoglycosides in this strain was mediated by an aminoglycoside 6'-N-acetyltransferase and a gentamicin phosphotransferase. Genetic determinants for these enzymes were borne on a circular covalently closed plasmid of approximately 11 megadaltons. These resistance determinants closely resemble those found in isolates of S. aureus that have caused nosocomial infections in patients in Europe.

Gentamicins↗
PubMed1978

Inhibition of lower esophageal sphincter circular muscle by female sex hormones.

To determine the effect of estrogenic and progesteronic activity on lower esophageal sphincter (LES) circular muscle, studies were performed on 20 adult opossums. Does-response curves on circular smooth muscle strips from the LES were constructed for gastrin and acetylcholine alone, and with 17beta-estradiol and/or progesterone added. Each female hormone significantly decreased the maximal LES muscle responses to gastrin and acetylcholine. A combination of 17beta-estradiol and progesterone abolished the response to gastrin. In contrast, the male sex hormone, dihydrotestosterone, had no effect. In conclusion, administration of estrogen and progesteron, but not dihydrotestosterone, in vitro reduced LES muscle responses to gastrin and acetylcholine. These studies suggest that the female sex hormones can alter LES function and potentially may be of importance in the pathogenesis of heartburn of pregnancy.

Acetylcholine↗
PubMed1978

Effect of thoracic vagotomy and vagal stimulation on esophageal function.

The purpose of this study was to determine the effect of thoracic vagotomy and thoracic vagal stimulation upon esophageal peristalsis and lower esophageal sphincter (LES) function in the opossum. The thoracic portion of the vagus nerve was sectioned in the upper or lower thorax. Bilateral, but not unilateral, thoracic vagotomy above the level of the heart abolished peristalsis and LES relaxation in response to swallowing or cervical vagal electrical stimulation. Thoracic vagotomy at the level of the ventricle or below did not alter either peristalsis or LES relaxation during swallowing or cervical vagal stimulation. Secondary peristalsis and its associated LES relaxation was unaltered by thoracic vagotomy at any level. Electrical stimulation of the distal end of the upper thoracic vagus elicited both peristalsis and LES relaxation. Electrical stimulation of the distal end of the lower thoracic vagus elicited both peristalsis and LES relaxation. Electrical stimulation of the distal end of the lower thoracic vagus, as well as stimulation of the vagal branches to the terminal esophagus, gave only LES relaxation. These studies suggest that: a) the major extrinsic vagal innervation mediating primary peristalsis terminates in the upper portion of the esophagus, whereas the vagal innervation mediating LES relaxation responses are present throughout the length of the esophagus; and b) secondary peristalsis and its associated LES relaxation occurs independent of extrinsic vagal innervation.

Animals↗