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Biomedical subjects

S Cohen

Publications and source records attributed to S Cohen.

At least 919 records · Page 51Linked to original sources
PubMed1980

Malaria vaccines?

Explore the source record for details and available documents.

Epitopes↗
PubMed1980

Continuous production of monoclonal rheumatoid factor by EBV-transformed lymphocytes.

Human B lymphocytes are immortalized by Epstein-Barr virus (EBV, ref. 1). The virus can be used to establish lymphoblastoid cell lines that produce and actively secrete specific antibodies. The original method, which we have used for various antigens is based on selection of the specific surface antigen receptor-positive lymphocytes from the peripheral blood lymphocytes of a donor who was previously sensitized to the corresponding antigen. Furthermore, by cloning the polyclonal anti-NNP cell line we have produced human monoclonal antibodies for the first time in vitro. About 5-20 microgram ml-1 stably produced specific antibody is obtained in the supernatant of the cell lines. This approach can be used for the in vitro production of monoclonal human autoimmune antibodies by EBV-immortalized lymphocytes from patients with autoimmune diseases. We demonstrate the continuous production in vitro of a monoclonal IgM and anti-IgG antibody (rheumatoid factor, r.f.) by a lymphoblastoid cell line established from a patient with rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1980

Identification of phosphotyrosine as a product of epidermal growth factor-activated protein kinase in A-431 cell membranes.

Epidermal growth factor (EGF)-enhanced protein kinase activity in plasma membrane preparations of A-431 human epidermoid carcinoma cells was shown to involve the phosphorylation of tyrosine residues. Phosphotyrosine was detected in both endogenous membrane proteins and in histone when added as an exogenous protein substrate. The major phosphorylated amino acid in partial acid hydrolysates of 32P-labeled A-431 membranes was identified as phosphotyrosine on the basis of its identical behavior to authentic phosphotyrosine on paper electrophoresis and thin layer chromatography; its 5-dimethylaminonaphthalene-1-sulfonyl (dansyl) derivative was indistinguishable from that of the authentic compound. Only traces, if any, of phosphoserine or phosphothreonine were detected. [32P]Phosphotyrosine was also detected in pronase digests of 32P-labeled membrane proteins. The EGF receptor . protein kinase complex, which was solubilized with Triton X-100 and purified by EGF affinity chromatography, was shown to phosphorylate tyrosine residues of the isolated membrane protein.

Carcinoma, Squamous Cell↗
PubMed1980

Pathogenesis of coffee-induced gastrointestinal symptoms.

Heartburn was the major gastrointestinal symptom associated with drinking coffee in 31 subjects. These symptomatic subjects had a diminished basal lower-esophageal-sphincter (LES) pressure, 8.3 +/- 1.1 mm Hg, as compared with the pressure in asymptomatic subjects, 19.4 +/- 1.3 mm Hg (P less than 0.01), in response to four separate doses of coffee. LES pressure increased in normal subjects but changed only minimally in the symptomatic group (P less than 0.01). Basal acid output was similar in both groups, but the maximal acid response to coffee was paradoxically greater in normal subjects, 20.9 +/- 3.6 meq per hour, than in the symptomatic group, 9.4 +/- 1.5 meq per hour (P less than 0.01). During coffee instillation into the stomach, 26 of 31 symptomatic subjects (83 per cent) had heartburn at the highest dosage. Cimetidine, but not placebo, reduced acid secretion and heartburn in response to coffee, suggesting that acid was required for the development of symptoms. These studies suggest that LES dysfunction and gastroesophageal reflux, rather than gastric hypersection, are responsible for the heartburn caused by coffee in certain susceptible persons.

Adult↗
PubMed1980

Epidermal growth factor-receptor-protein kinase interactions. Co-purification of receptor and epidermal growth factor-enhanced phosphorylation activity.

Membranes may be prepared from A-431 human epidermoid carcinoma cells which have the ability to bind 125I-labeled epidermal growth factor (EGF) in a specific manner and which, in the presence of EGF, catalyze the phosphorylation of a number of endogenous membrane proteins. The activation of the membrane associated protein kinase by EGF appears to be a reversible phenomenon. The membrane preparation may be solubilized by a number of nonionic detergents with the retention of both 125I-labeled EGF-binding activity and EGF-enhanced phosphorylation of specific membrane proteins. The solubilized membrane preparation may be purified by affinity chromatography using EGF covalently linked to Affi-Gel. The purified preparation retains both EGF-binding activity and EGF-enhanced phosphorylation activity. Analysis of the affinity-purified preparation by sodium dodecyl sulfate-gel electrophoresis indicates the presence of one major protein band of molecular weight 150,000 and several trace bands. The evidence suggests that the major 150,000 protein band is the receptor for EGF and is a substrate of the phosphorylation reaction. The co-purification of EGF-binding activity and EGF-stimulated phosphorylation activity suggests an inherent close relationship.

Animals↗
PubMed1980

Inhibition of postprandial colonic motility after ingestion of an amino acid mixture.

Previous studies suggested that the ingestion of a mixture of amino acids inhibited the fat-stimulated increase in colonic motility. This study determine the effect of the ingestion of an amino acid mixture on the postprandial distal colonic spike potential (SP) response to a standard 1000-calorie meal in normal subjects and in patients with the irritable bowel syndrome. The distal colonic response was measured following a standard meal with and without the preadministration of a protein hydrolysate solution. After the meal, normal subjects had their maximum response within the first 30-min postprandial period (41.0 +/- 6.3 SP/30 min). Spike activity returned to fasting activity by 60 min. Most patients with irritable bowel syndrome did not have a significant early postprandial distal colonic spike response (P > 0.05), but all patients had a large late increase in spike activity occurring 60-90 min postprandially (50.0 +/- 5.0 SP/30 min) (P < 0.001). Ingestion of the protein hydrolysate solution prior to the meal resulted in suppression of the early colonic spike response in normal subjects (P < 0.01) and the late colonic spike response in the irritable bowel patients (P < 0.01). This study suggests that amino acids can modulate postprandial colonic motility and that dietary alteration may be beneficial in the irritable bowel syndrome.

Amino Acids↗
PubMed1980

Ureaplasma urealyticum (T-mycoplasma) infection: does it have a role in male infertility?

Ureplasma urealyticum (T-mycoplasma) has been related to male infertility by some observers. To assess further this question 150 couples who presented for fertility had semen and cervical mucus cultures for mycoplasma. Positive cultures were obtained from 69 couples. There were no significant differences in the semen analyses among patients with positive or negative cultures. The presence of mycoplasma in the semen is probably the result of contamination at the time of ejaculation. Routine investigation for the presence of mycoplasma in subfertile men is unjustified. The routine use of broad-spectrum antibiotics in subfertile patients with positive mycoplasma culture is unnecessary.

Cervix Mucus↗
PubMed1980

Identity and interspecific transfer of gentamicin-resistance plasmids in Staphylococcus aureus and Staphylococcus epidermidis.

The hypothesis that emergence of gentamicin-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis in a neonatal special care nursery was the result of transfer of a single plasmid between these two species was examined. In experiments with mixtures of staphylococci, either in mixed cultures or on human skin, isolates of S. aureus and S. epidermidis transferred their gentamicin-resistance plasmids both intra- and interspecifically. By electron microscopy, the molecular masses of the plasmids from S. aureus and S. epidermidis were the same, 12.2 +/- 0.36 (standard deviation) and 12.3 +/- 0.56 megadaltons, respectively. Restriction endonuclease analysis of the plasmids from five isolates of S. aureus and two isolates of S. epidermidis, with use of the enzymes HaeIII, EcoRI, XbaI, and HindIII, showed no differences in the digestion patterns of the seven gentamicin-resistance plasmids. The results supported the hypothesis that plasmid transfer between S. aureus and S. epidermidis occurs in nature.

Conjugation, Genetic↗
PubMed1980

Temperature dependency for maintenance of transformation in mouse cells transformed by simian virus 40 tsA mutants.

Mouse embryo fibroblasts and 3T3 cells were transformed by wild-type, tsB4, tsA7, tsA58, and tsA209 simian virus 40. Clones of transformants were generated both in soft agar and in liquid medium by focus formation and at both high and relatively low multiplicities of infection. All transformants were assayed for three phenotypes of transformation: (i) the ability to form highly multinucleated cells in cytochalasin B-supplemented medium, i.e., uncontrolled nuclear division; (ii) the capacity to continue DNA synthesis at increasing cell density; and (iii) the ability to form colonies in soft agar. The great majority of mouse embryo fibroblast transformants generated with tsA mutant virus were temperature sensitive for transformation in all three assays, regardless of the input multiplicity or whether they were generated in liquid medium or soft agar. These transformants exhibited a normal or near-normal phenotype at the nonpermissive temperature of 40 degrees C. All but one of the transformants which appeared transformed at both temperatures were in the A209 group. In contrast to mouse embryo fibroblasts, transformants generated with 3T3 cells and tsA virus were often not temperature sensitive, exhibiting the transformation phenotypes at both temperatures. This phenomenon was more often observed when 3T3 transformants were generated in soft agar. These results, along with other published data, suggest that uncontrolled nuclear division and uncontrolled DNA synthesis are a function of the simian virus 40 A gene. Finally, with the 3T3 transformants, there was often discordance in the expression of transformation among the three phenotypes. Some tsA transformants were temperature sensitive in one of two assays but were transformed at both 33 and 40 degrees C in the remaining assay(s). Other transformants exhibited a normal cytochalasin B response at either temperature but were temperature sensitive in the other assays.

Animals↗