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Biomedical subjects

S Cohen

Publications and source records attributed to S Cohen.

At least 469 records · Page 26Linked to original sources
PubMed1991

Testicular plasmacytoma. A case report with immunohistochemical studies and literature review.

Plasmacytomas of the testes are extremely rare tumors, especially when occurring in the absence of a previous or concurrent diagnosis of multiple myeloma. We present a case of solitary testicular plasmacytoma in a 71-year-old man who had no clinical evidence of myeloma. Immunohistochemical stains showed monoclonal cytoplasmic production of IgA-kappa within tumor cells. A summary of the other reported cases of testicular plasmacytoma is presented. Plasmacytoma of the testes, while occasionally manifesting as a solitary, primary lesion, most likely is a precocious, highly unusual manifestation of systemic multiple myeloma.

Aged↗
PubMed1991

Low dose verapamil and nitroprusside distinguish tonic from cholinergic-induced contractions in in vivo feline lower esophageal sphincter.

Although in vitro studies suggest that cholinergic induced contractions and spontaneous tone are mediated by two different cellular pathways, this has not been shown in vivo. The purpose of this study was to distinguish these types of contractions in the feline lower esophageal sphincter (LES) through use of i.v. selective pharmacologic antagonists. Continuous infusion of the calcium channel antagonist verapamil (16-128 micrograms/kg/min) caused a dose-dependent inhibition of bethanechol induced and tonic pressure change. At 32.0 micrograms/kg/min, verapamil produced significantly greater inhibition of bethanechol induced contractions when compared with inhibition of basal LES tone (57.4 versus 4.8%, P less than .02, n = 5). Verapamil also caused a parallel decrease in LES spike activity associated with bethanechol induced contractions. In contrast, lower doses of nitroprusside (0.5 micrograms/kg/min) inhibited LES tone by over 50% (50.6 +/- 21.8%) yet had no significant effect (16.8 +/- 23.4%) on bethanechol induced contractions. Also, inhibition of basal LES tone correlated poorly with its effect on associated spike activity. It is concluded that in the in vivo feline LES, spike dependent cholinergic contractions can be distinguished from LES tone by the use of low dose verapamil and nitroprusside, respectively. This selective inhibition suggests that two cellular mechanisms mediate LES contractions and that these pathways can be distinguished pharmacologically in vivo.

Animals↗
PubMed1991

Chronicity of depressive episode in relation to antidepressant-placebo response.

Pooled data from three 6-week placebo-controlled, double-blind, phase III clinical trials, designed to assess the efficacy of newer antidepressants, were retrospectively analyzed to study the relationship between chronicity of presenting depressive episode and response to placebo, imipramine, and adinazolam. One hundred forty-six depressed outpatients met criteria for inclusion into this study; 80 received placebo treatment, 27 imipramine and 39 adinazolam treatment. Consistent with our hypothesis the response to placebo was low in subjects who were depressed for 1 year or longer (22.6%) as compared to a higher response rate (44.9%) among those who were not as chronically depressed. The response to imipramine and adinazolam was not related to the duration of presenting depressive episode. The implications of these findings are discussed.

Adult↗
PubMed1991

Increased caries prevalence in adolescents who immigrated from Ethiopia to Israel.

The prevalence of caries in adolescents who immigrated from Ethiopia increased rapidly, the longer their residence in Israel. A total of 159 newly immigrated adolescents, aged 11-19, who lived in small absorption institutions, as well as 52 Ethiopian adolescents and 173 Israeli-born adolescents living together in a larger institution, were examined. Caries was recorded using the DMFT index, which indicates caries experience. The mean caries prevalence (DMFT) of the newly immigrated Ethiopians was 0.49 and of those residing in Israel 12-24 months was 1.76. The caries rate was highest in the Israeli group (DMFT-10.0). The percentages of caries-free individuals were 10.0% for the Israelis, 58.8% for the Ethiopians who immigrated earlier and 81.8% for the newly immigrated. The abrupt change in dietary habits seems to have created a new high risk caries group. Caries preventive measures, the use of fluoride products, and patient education and motivation are urgently required.

Adolescent↗
PubMed1990

Synergistic interactions between tumor necrosis factor and inhibitors of DNA topoisomerase I and II.

TNF is a pleiotropic cytokine that mediates diverse cellular responses, including cytotoxicity, cytostasis, proliferation, differentiation, and the expression of specific genes. Many of these processes require the activity of DNA topoisomerases I and II. We have investigated the interactions of TNF with inhibitors of both topoisomerases in 16-h assays using the murine L929 and human ME-180 cell lines, which undergo a cytotoxic TNF response. Camptothecin, a specific inhibitor of topoisomerase I, enhanced TNF cytotoxicity 150-fold against both cell lines. The topoisomerase II inhibitors VM-26 and VP-16, which stabilize covalent DNA-topoisomerase intermediates, greatly enhance TNF cytotoxicity against both cell lines. The most effective, VM-26, can lower the TNF LD50 to femtomolar levels. In contrast, the topoisomerase II inhibitors novobiocin and coumermycin, which bind to the enzyme ATPase site, protect L929 cells from TNF cytotoxicity but enhance TNF cytotoxicity in ME-180 cells. The large changes in TNF sensitivity induced by drug concentrations that by themselves show no effect, and the opposing synergistic effects of inhibitors with different inhibitory mechanisms (in L929 cells), suggest the active involvement of topoisomerases in TNF-mediated cytotoxicity. The correlation of cytotoxic synergy with the stabilization of DNA strand breaks indicates that DNA damage may play a significant role in TNF-mediated cytotoxicity.

Aminocoumarins↗
PubMed1990

A merozoite receptor protein from Plasmodium knowlesi is highly conserved and distributed throughout Plasmodium.

The 66-kDa merozoite surface antigen (PK66) of Plasmodium knowlesi, a simian malaria, possesses vaccine-related properties that are thought to originate from a receptor-like role in parasite invasion of erythrocytes. We report the complete sequence of PK66 which allowed the demonstration that highly conserved analogues exist throughout Plasmodium including a recently reported gene from P. falciparum (Peterson, M. G., Marshall, V. M., Smythe, J. A., Crewther, P. E., Lew, A., Silva, A., Anders, R. F., and Kemp, D. J. (1989) Mol. Cell. Biol. 9, 3151-3155). These analogues are highly promising vaccination candidates. The distribution of PK66 changes after schizont rupture in a coordinate manner associated with merozoite invasion. The protein is concentrated at the apical end prior to rupture, following which it can distribute itself entirely across the surface of the free merozoite. During invasion, immunofluorescence studies suggest that, PK66 is excluded from the erythrocyte at, and behind, the invasion interface.

Amino Acid Sequence↗
PubMed1990

The epidermal growth factor precursor isolated from murine kidney membranes. Chemical characterization and biological properties.

To understand the biology and the biochemistry of the epidermal growth factor (EGF) precursor in normal tissues we partially purified the EGF precursor from mouse kidney. The precursor was purified by affinity chromatography, using wheat germ lectin and antibodies to murine EGF. The EGF precursor is a glycosylated integral membrane protein of apparent molecular mass of 140-150 kDa. The solubilized EGF precursor is biologically active as evidenced by its ability to compete with 125I-labeled EGF for binding to the EGF receptor in intact fibroblasts and its ability to stimulate the growth of cells dependent on EGF for growth. The EGF precursor from mouse kidney can be proteolytically processed by the EGF-associated arginine esterase into a smaller fragment (97 kDa) that retains both immunologic sensitivity to EGF antiserum and biological activity. Extensive digestion of the EGF precursor with pepsin liberates a biologically and immunologically active protein of approximately the size of mature EGF.

Animals↗
PubMed1990

Binding of porphyrin to human serum albumin. Structure-activity relationships.

The equilibrium binding of hydroxyethyl vinyl deuteroporphyrin (HVD) and of irreversible porphyrin aggregates to human serum albumin was studied at the molecular level. This protein may function as an endogenous drug carrier for porphyrins in photodynamic therapy of tumours. HVD-protein binding studies revealed two types of binding sites, which are attributed to the two HVD isomers. The binding constant for the high-affinity isomer, 2.1 (+/- 0.3) x 10(8) M-1, is similar to that previously determined for protoporphyrin. At the same time the binding constant for the lower-affinity HVD isomer, 1.8(+/- 0.3) x 10(6) M-1, is similar to that previously determined for haematoporphyrin. Irreversible porphyrin aggregates were purified from the haematoporphyrin derivative and from Photofrin and are defined by spectral and chromatographic data. Gel-exclusion studies indicate that the dominant size of these aggregates is ten porphyrin monomeric units. The protein-binding constant of these aggregates is 1.7(+/- 0.2) x 10(5) M-1, with four binding sites per protein molecule. The distinction between the HVD isomers along the porphyrin-protein affinity sequence gives insight into the relationship of porphyrin structure to porphyrin-albumin binding. On the basis of this study an evaluation of human serum albumin as an endogenous carrier for porphyrins (at various aggregation states) in photodynamic therapy of tumours is presented.

Binding Sites↗
PubMed1990

Vasopressinergic innervation of the mouse suprachiasmatic nucleus: an immuno-electron microscopic analysis.

Attempts are being made to unravel the local circuitry of the suprachiasmatic nucleus, with a view toward eventually correlating specific neuronal systems with circadian events. Hence, the vasopressinergic innervation of this nucleus in the laboratory mouse has been analyzed immunocytochemically at the light and electron microscopical levels. Monoclonal antineurophysin and polyclonal antivasopressin were used on aldehyde-fixed brains. Serial vibratome sections of the appropriate forebrain region were prepared for pre-embedding immunoperoxidase staining and/or postembedding immunogold labeling. Immunoreactive somata, processes, varicosities, and synaptic terminals were found throughout the suprachiasmatic nucleus, their ratio and density varying at different locations. The predominant type of vasopressinergic soma was ovoid to rounded (7-10 microns), containing secretory granules (85-120 nm), a large proportion of which were immunoreactive. Axon terminals, both nonimmunoreactive and immunoreactive, impinged upon vasopressinergic somata and processes, often displaying synaptic specializations. Vasopressinergic terminals, containing secretory granules and microvesicles, were found throughout the nucleus, particularly within the dorsomedial neuropil. These labeled terminals varied in size (0.4-3.4 microns 2) and shape, ranging from compact boutons to pleomorphic profiles, some deeply indented by postsynaptic spines, either dendritic or somatic. Approximately 65% of the vasopressin-containing terminals were axodendritic and 30% axosomatic; about 5% appeared to be axoaxonic. At least a quarter of all vasopressinergic synaptic terminals were axospinous. Other forms of interneuronal contact involving vasopressinergic elements (somata, dendrites) included extensive membrane to membrane appositional sites, and multiple puncta adhaerentia. The versatility of interconnections between vasopressin-containing neurons in the mouse suprachiasmatic nucleus suggests a highly active and coordinated network, which contributes substantially to local intranuclear circuitry. In addition, a dense efferent vasopressinergic output is directed dorsally towards the periventricular hypothalamus, where direct associations may be established with diverse hypothalamic neuroendocrine systems.

Animals↗
PubMed1990

Central catecholaminergic dysfunction and behavioural disorders following hypoxia in adult rats.

Wistar male rats, 3-4 months old, were made to breathe for 6 h a sub-lethal hypoxic atmosphere consisting of 8% oxygen and 92% nitrogen. Following this treatment, these rats were subjected to a series of behavioral and biochemical tests starting 30 days and ending at about 180 days after the hypoxic insult. an age-matched control group was subjected to the same series of tests. The following findings were made at the time interval indicated, relative to controls: (1) At 30-35 days, diurnal (3 h) and nocturnal (12 h) locomotor activities decreased by about 25%. (2) At 40-45 days, amphetamine in the dose range of 0.25-1 mg/kg proved less effective in eliciting an increase in motor activity and stereotypic behavior. (3) At about 50 days, apomorphine in the dose range 0.25-0.5 mg/kg caused an increase in stereotypic behavior. (4) At 60-65 days, alpha-methyl-p-tyrosine at the dose of 50 mg/kg caused a more pronounced hypoactive syndrome and a slower rate of recovery of motor activity. (5) At 75-90 days, performance in the active avoidance test was inferior to that of controls. (6) At 180 days, and one hour after a dose of 200 mg/kg alpha-methyl-p-tyrosine, the turnover rates of hippocampal norepinephrine and caudate-putamen dopamine were much below control. One may tentatively conclude that one of the effects of hypoxia in adult rats is a lesion producing long-term behavioral disorders which are partly ascribed to dopaminergic and, possibly noradrenergic, dysfunction.

Age Factors↗
PubMed1990

Health effects of long-term solvent exposure among women in blue-collar occupations.

The relationship of solvent exposure to self-reported neurologic and somatic symptoms as well as neuropsychological performance was examined in a sample of 567 female blue collar workers who were members of the International Brotherhood of Electrical Workers (IBEW). Structured interviews were conducted at IBEW offices. Five solvent exposure categories were derived--never exposed, exposed prior to but not during the past year, exposed during the past year but not currently, currently exposed less than 50% of the time, and currently exposed more than 50% of the time. No differences among the groups on neuropsychological performance were found. On the other hand, heightened exposure was significantly related to depression, severe headaches, light-headedness, room spinning, appetite difficulties, funny taste in mouth, weakness/fatigue, rashes, and abdominal pain after controlling for the effects of seven risk factors (age, smoking, moderate-heavy alcohol consumption, severe obesity, history of physician-diagnosed chronic illness, working in a clean room, and exposure to other chemicals). These findings are consistent with Scandinavian studies of solvent-exposed male workers and point to the need for careful prospective research.

Adult↗
PubMed1990

Morphologic changes in human carcinoma cells (A-431) stimulated by epidermal growth factor: effect of cholesterol and low-density lipoproteins on the ruffling response.

Stimulation of A-431 carcinoma cells with epidermal growth factor (EGF) causes dramatic morphologic responses including ruffling, rounding, and bulk-phase pinocytosis. In attempts to explore the mechanisms responsible for changes in plasmalemma topography, we have investigated the effects of exogenous sterols thought to alter membrane fluidity. Light and scanning electron microscopy revealed a time- and concentration-dependent inhibition of ruffling (greater than 90%) by cholesterol. This effect could be duplicated by preincubation of the cells with comparable levels of low-density lipoproteins (LDL). EGF-stimulated bulk-phase endocytosis also is inhibited by treatment with cholesterol. No alteration of EGF binding, kinase stimulation, or internalization was detected in cells incubated in cholesterol-enriched medium (175 micrograms/ml in 0.5% ethanol), nor did cholesterol or LDL have any effect on EGF-stimulated rounding. Morphometry of electron micrographs from cholesterol-treated cells revealed a selective depletion of interdigitating lateral surface membrane that normally appears to be recruited to generate apical ruffles. Thus, the sterol inhibition of ruffling may be due to redistribution of plasmalemma rather than to changes in membrane viscosity. Together with previous observations, these data suggest that EGF-stimulated ruffling and bulk-phase pinocytosis are related phenomena, whereas EGF-stimulated cell rounding is an independent process.

Carcinoma, Squamous Cell↗