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Biomedical subjects

S A Cohen

Publications and source records attributed to S A Cohen.

At least 19 recordsLinked to original sources
PubMed1992

Age-related alterations of NMDA-receptor properties in the mouse forebrain: partial restoration by chronic phosphatidylserine treatment.

The effect of aging on the properties of N-methyl-D-aspartate (NMDA) receptors in the forebrain of female NMRI mice was investigated using the antagonist [3H]MK-801 as radioligand. Compared to young (3 months) mice, aged (20 months) mice showed changes of the properties of the NMDA receptor at three different levels: (1) the density was reduced by about 35%; (2) the efficacy of L-glutamate and glycine for stimulating specific [3H]MK-801 binding was enhanced, probably because more NMDA receptor-associated ion channels are closed under baseline conditions in the aged brain; (3) the affinity of L-glutamate and glycine to its binding sites at the NMDA receptor complex was also enhanced. Chronic treatment of aged mice with phosphatidylserine (20 mg/kg, i.p., once daily) for three weeks completely normalized enhanced efficacy and affinity of L-glutamate and glycine and elevated NMDA receptor density by approximately 25%. These findings are consistent with the assumptions that deficits of the NMDA receptor are one of the mechanisms of age-related cognitive impairment and that the beneficial effects of phosphatidylserine treatment on cognitive deficits of aged individuals might be partially due to the effects of this drug on age-related NMDA receptor deficits.

Aging↗
PubMed1992

n-butyrate reduces the expression of beta-galactoside alpha 2,6-sialyltransferase in Hep G2 cells.

n-Butyrate, a short chain fatty acid that is produced by colonic bacterial fermentation, is detectable in portal blood and induces differentiation in various human neoplastic cell lines. Earlier reports indicated approximately 20-fold induction in vitro by n-butyrate of the sialyltransferase that catalyzes terminal glycosylation of GM3 ganglioside in HeLa and colon cancer cells. We previously isolated a 1.3-kilobase cDNA for a human beta-galactoside alpha 2,6-sialyltransferase, for which N-linked glycoproteins are the acceptors. We report here that treatment of Hep G2 cells with 5 mM n-butyrate for 24 h reduced beta-galactoside alpha 2,6-sialyltransferase mRNA levels by approximately 90%. Reductions in mRNA level were followed by approximately 75 and approximately 90% reductions, respectively, in specific beta-galactoside alpha 2,6-sialyltransferase enzyme activity after treatment for 24 and 36 h with 5 mM n-butyrate. However, in contrast with earlier reports of enhanced ganglioside synthesis in response to n-butyrate treatment, incubation of Hep G2 cells with n-butyrate did not alter the ganglioside pattern as assessed by thin layer chromatography of lipids extracted from treated cells. Nuclear run-on reactions indicated that the rate of transcription of beta-galactoside, alpha 2,6-sialyltransferase was not altered by treatment with 5 mM n-butyrate for 24 h, but the effects of this treatment on cytoplasmic levels of beta-galactoside alpha 2,6-sialyltransferase mRNA were largely negated by co-treatment with actinomycin D or cycloheximide. Therefore, our results show that n-butyrate reduces expression of mature beta-galactoside alpha 2,6-sialyltransferase mRNA by post-transcriptional mechanisms.

Antigens, CD↗
PubMed1992

Hepatic metastasis alters the immune function of murine liver nonparenchymal cells.

To examine the effect of a single hepatic focus of metastatic colon tumor on the immune function of liver non-parenchymal cells (NPCs) from C57Bl/6 mice, we injected 2.5 x 10(5) liver-derived murine colon adenocarcinoma (LD-MCA-38) cells beneath the liver capsule. Three weeks following injection of the tumor cells, the immune function of the NPCs was studied. The NPCs from tumor-bearing mice exhibited increased cytotoxic and proliferative activity. The NPCs from tumor-bearing mice also contained a greater percentage of CD8+ and T-cell receptor gamma/delta+ liver-associated T lymphocytes. Levels of interleukin 6 and tumor necrosis factor were increased in the NPC supernatant, and interleukin 6 levels were increased in serum from tumor-bearing mice. We conclude that the presence of a single hepatic focus of metastatic tumor results in augmented immune function of murine liver NPCs.

Adenocarcinoma↗
PubMed1992

Interferon-alpha prevents endotoxin-induced mortality in mice.

Endotoxins, the lipopolysaccharide (LPS) moieties on the bacterial cell wall, cause many of the pathological features of Gram-negative septicemia. Tumor necrosis factor (TNF), primarily a product of monocyte/macrophages, has been shown to mediate many of the pathophysiological effects of endotoxin. Kupffer cells, the largest macrophage population in the body, release TNF when stimulated by LPS in vitro. A recombinant human hybrid interferon-alpha A/D (rIFN-alpha) markedly inhibited this LPS-elicited TNF production by Kupffer cells. The effects of rIFN-alpha were further tested in C57BL/6 mice receiving a lethal dose (400 micrograms/mouse) of LPS. All LPS-treated mice died within 2 days. Pretreatment with rIFN-alpha 1 h before LPS challenge improved the survival at 3 days to 22% (5/23, p < 0.04). In contrast, rIFN-alpha was more effective when administered 20 min after LPS injection, increasing the survival rate to 81% (13/16, p < 0.0001). TNF mRNA expression in the liver and spleen 50 min after LPS challenge, and plasma TNF 1.5 h after LPS were also reduced by either pretreatment or post-treatment with rIFN-alpha. Subsequently, experiments were carried out to test the efficacy of delayed rIFN-alpha treatment. A significant protective effect was still apparent when rIFN-alpha was administered 6, 10 and even 14 h (81%, 62% and 28% survival, respectively) after LPS challenge when serum TNF levels had already returned to near baseline. These experimental results suggest that rIFN-alpha might have a therapeutic potential for the prevention and treatment of the deleterious effects associated with endotoxemia besides mechanisms initially blocking TNF production.

Animals↗
PubMed1992

Genetic control of streptococcus-induced hepatic granulomatous lesions in mice.

Hepatic granulomatous lesions were induced in mice by a single intraperitoneal injection of 3 mg of disrupted Streptococcus pyogenes cell-wall material. Mice carrying the H-2b or H-2k haplotypes were highly susceptible to the induction and three weeks after the injection produced numerous granulomas. In contrast, mice of the H-2d haplotype were resistant and produced only a few hepatic granulomas. Resistance was inherited as a dominant trait and in the backcross generation segregated together with the H-2d phenotype. Testing of the H-2-recombinant mice indicated that the putative gene(s) determining resistance/susceptibility is located to the right of the S and to the left of the D region. This location corresponds to the recently described gene cluster consisting of tumor necrosis factor (TNF) and lymphotoxin genes and several BAT sequences. The known effect of TNF on granuloma formation in mice is consistent with a possible effect of TNF genes, and their variants, on S. pyogenes-inducibility of hepatic granulomas in mice.

Animals↗
PubMed1992

Localization of epitopes for antibodies that differentially label sodium sodium channels in skeletal muscle surface and T-tubular membranes.

We previously characterized two monoclonal antibodies, A/B2 and L/D3, that bind to the amino-terminus of the sodium channel but produce distinct immunocytochemical patterns in innervated adult skeletal muscle. Because these findings suggested the presence of several channel isoforms, we sought to define the epitopes for each antibody. Five peptides encompassing the amino-terminal 126 residues of the adult skeletal muscle sodium channel were synthesized and tested by radioimmunoassay against each antibody. Both monoclonals bound only to a peptide comprising residues 1-30 (I1-30). A nested set of peptides within this region was then synthesized and used to compete for antibody binding to I1-30. L/D3 binding was quantitatively inhibited by oligopeptides 1-30, 7-30, 13-30, and 19-30 but not 25-30, while binding of A/B2 was blocked only by the intact I1-30 peptide. This data implies that the epitope for L/D3 lies within residues 19-25 while the epitope for A/B2 is contained within residues 1-6. These tentative epitope localizations were confirmed using both proteolytic cleavage of I1-30 and immunoreactivity of a peptide corresponding to residues 1-12 with A/B2 but not L/D3. Therefore, epitopes for each monoclonal antibody are present in the SkM-1 sequence and are in close proximity in the amino-terminus of the protein. Their characteristic immunocytochemical labeling patterns may reflect differing accessibility of the epitopes in various membrane environments.

Amino Acid Sequence↗
PubMed1992

Augmentation of the immune response of the murine liver by levamisole.

Murine hepatic nonparenchymal cells (NPC) were studied following in vivo treatment with levamisole. This agent was found to increase the cytolytic action of these cells against YAC-1 and P815 target cells. An increase in the cytostatic activity against liver-derived murine colon adenocarcinoma 38 tumor cells was also observed. Treatment with levamisole also augmented the proliferation of the hepatic NPC. Supernatants generated by these cells contained an agent capable of stimulating the proliferation of bone marrow cells from the same mice. The effect of levamisole on different subsets of NPC derived from the liver in this model is discussed.

Animals↗
PubMed1992

Direct demonstration of engraftment of human peripheral blood leukocytes in SCID mice.

One of the major problems using man-mouse chimeras is still the difficulty to demonstrate unequivocally engraftment of human cells in murine tissues. Using supravital labelling of human leukocytes with the Hoechst dye H33342, it was possible to demonstrate directly their engraftment and to assess their distribution in the tissues of the severe combined immunodeficiency (SCID) mice. The human cells can be traced for a period of 4-5 weeks. In contrast to earlier reports, combined marker and labelled-cell studies suggest that T-cell surface marker CD3 with reported specificity for human lymphocytes are indeed found, also in man-mouse chimeras, only on human cells. The ratio of B and T cells of human origin changes significantly after transfer into SCID mice and differs among various SCID tissues. The simple staining procedure using the supravital nuclear dye H33342 opens new possibilities for the study of cellular interactions and host responses of the human immunoreactive cells in an increasingly well-characterized animal model.

Animals↗
PubMed1991

Analysis of protease-sensitive regions in the skeletal muscle sodium channel in vitro and implications for channel tertiary structure.

The tertiary structure of the rat skeletal muscle sodium channel was probed in vitro by determining regions of sensitivity to V-8 protease, trypsin, and chymotrypsin. Resultant channel fragments were identified with antibodies to defined sequences distributed along the primary structure. The temporal pattern of proteolysis was followed with channel protein in either detergent-phospholipid micelles or membrane fragments as well as with channel exposed to sodium dodecyl sulfate. Proteolysis in micelles and membranes occurred in discrete, reproducible steps that were similar in both systems. Although the size of intermediates varied slightly, their sequence of appearance was similar for all enzymes, suggesting that the observed pattern was determined by the relative accessibility of selected sites in the tertiary structure. No major change in channel organization appeared to occur after solubilization of membranes in nonionic detergents. Highly accessible sites in the native structure included the carboxyl terminus and the region linking the second and third internal repeat domains, while the amino terminus and the repeat domains themselves were relatively resistant to proteolysis unless the protein was denatured. Kinetically, interdomain II-III was the most readily cleaved; interdomains I-II and especially III-IV were less easily accessible. While domains I and IV appeared to remain intact throughout our experiments, limit fragments for epitopes associated with domains II and III suggest that cleavage eventually occurs at sites between the putative S5 and S6 helices in these domains.

Animals↗
PubMed1991

Isolation and characterization of a novel liver-derived immunoinhibitory factor.

Cytosolic extracts prepared from perfused whole liver or purified hepatocytes of C57BL/6 mice inhibited interleukin-2--and concanavalin A--induced spleen cell proliferation in vitro. In contrast, cytosolic extracts from purified nonparenchymal liver cells had no effect. Arginase and very-low-density lipoprotein were previously identified as two immuninhibitory substances present in liver cytosolic extracts. We demonstrated, however, that inhibitory activity remained after removal of very-low-density lipoprotein and arginase from liver cytosolic extract by repeated ultracentrifugation and gel filtration chromatography, respectively, suggesting the presence of another inhibitor. Further purification by anion-exchange chromatography and chromatofocusing led to the isolation of a novel liver-derived immunohibitory factor. This liver-derived immunoinhibitory factor is sensitive to pronase digestion and heat and acid treatment; it has an estimated isoelectric point of 8.25. The Mr of liver-derived immunoinhibitory factor is 28 kD as estimated from its migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which is identical under both reducing and nonreducing conditions, indicating a monomeric nature of this protein. Amino acid composition analysis discloses that liver-derived immunoinhibitory factor is relatively rich in glycine and proline residues. Interleukin-2--induced spleen cell proliferation in vitro is inhibited by ths liver-derived immunoinhibitory factor, with a 50% inhibitory dose of 1.4 nmol/L. Furthermore, the biological activity of the liver-derived immunoinhibitory factor is not confined to mouse spleen cells, since the growth of B16 mouse melanoma and H35 rat hepatoma cells is also inhibited. A comparison with other liver-derived immunoinhibitors reported previously supports our claim that the liver-derived immunoinhibitory factor is a novel inhibitory protein.

Animals↗
PubMed1991

Endogenous interferon alpha/beta produced by Kupffer cells inhibits interleukin-1, tumor necrosis factor alpha production and interleukin-2-induced activation of nonparenchymal liver cells.

We have previously reported liver-specific interferon (IFN) alpha/beta production by murine Kupffer cells that was not observed with other tissue macrophages incubated in the absence of stimulators such as IFN gamma or lipopolysaccharide (LPS). Consequently, while interleukin-2 (IL-2) alone induced pronounced lymphokine-activated killer (LAK) activity from splenocytes, combination of anti-IFN alpha/beta antibody with IL-2 was required to generate significant LAK activity from nonparenchymal liver cells. This endogenous IFN alpha/beta production by Kupffer cells was not induced by LPS because (a) addition of polymyxin B did not abolish the positive effects of anti-IFN alpha/beta antibody on nonparenchymal liver cells, and (b) similar results were obtained when comparing the responses of LPS-responsive C3HeB/FeJ and LPS-hyporesponsive C3H/HeJ mice. The possibility of hepatotropic infection was also ruled out in that anti-IFN alpha/beta antibody enhanced hepatic but not splenic LAK cell induction in vitro in both conventional and germ-free C3H/HeN mice. IFN alpha/beta played an autoregulatory role by down-regulating the production of IL-1 and tumor necrosis factor alpha by Kupffer cells. However, the augmenting effect of anti-IFN alpha/beta antibody on LAK induction from non-parenchymal liver cells was not mediated through an increase in the level of either IL-1 or TNF alpha, as specific antisera against either cytokine did not abrogate this positive effect. Finally, flow-cytometry analysis showed that IFN alpha/beta significantly diminished the expression of IL-2 receptor alpha chain, indicating an inhibition of LAK cell generation at a relatively early stage of induction.

Animals↗
PubMed1991

Quantitative topics in research on aging.

The origins of the present series of articles on quantitative topics in aging research are presented. Specific articles are described, the purposes and goals of the quantitative series are set forth, and the relationship of this body of knowledge to the scientific status of the area of aging research is discussed.

Aging↗
PubMed1991

Immunology of inflammatory bowel disease: summary of the proceedings of the Subcommittee on Immunosuppressive Use in IBD.

As outlined, scanty data exist with regard to immunologic therapy in children with IBD despite the fact that the pediatric population affords a unique opportunity for clinical evaluation. Children are less affected by modifying conditions such as smoking, alcohol ingestion, and the long-term use of medications, and because of their specific needs for ponderal and linear growth, children might benefit most from immunological therapy that has been proven to be steroid sparing. Therefore, clinical trials to evaluate the efficacy of 6-MP and/or azathioprine in growing children with Crohn's disease would appear to provide a fruitful avenue for collaborative research. Efforts to organize a multicenter evaluation of these agents have been initiated. The studies are crucial in evaluating the efficacy and safety of immunosuppressive therapy in the pediatric population with IBD.

Aminosalicylic Acids↗
PubMed1990

Role of asialo-GM1 positive liver cells from athymic nude or polyinosinic-polycytidylic acid-treated mice in suppressing colon-derived experimental hepatic metastasis.

Liver-derived (LD) murine colon adenocarcinoma MCA-38 cells injected into the ileocolic vein (ICV) of C57BL/6 mice developed distinct hepatic foci within 14-21 days and survived for an average of 19-35 days. In contrast, C57BL/6-nu/nu mice given injections of LD-MCA cells by the same route did not develop hepatic lesions. Furthermore, 111In-labeled LD-MCA-38 tumor cells were rapidly taken up by the liver of conventional mice within 1 h and 73% of the radioactivity remained after 24 h. However, about 60% of the 111In-labeled LD-MCA-38 tumor cells were cleared from the liver of nude mice after 24 h. Nonparenchymal liver cells isolated from untreated conventional mice displayed little cytotoxicity against freshly excised 51Cr-labeled LD-MCA-38 cells but did lyse the standard natural killer target, YAC-1 tumor cells, in 4 h chromium release assays. On the other hand, nonparenchymal liver cells but not spleen cells from nude mice were cytotoxic to 51CR-labeled LD-MCA-38 in vitro. The nonparenchymal liver cell population responsible for tumor killing was phenotypically nonadherent and asialo-GM1 (AsGM1) positive. C57BL/6 mice treated with polyinosinic-polycytidylic acid [poly(IC)] also displayed cytotoxic activity against LD-MCA-38 tumor cells in vitro. Furthermore, poly(IC) treatment of mice 1-8 days after tumor inoculation suppressed the number of hepatic foci and also significantly increased the life span of tumor-bearing mice. Treatment of athymic nude mice or poly(IC)-treated conventional mice with anti-AsGM1 induced significant numbers of foci and significantly decreased the life span of MCA-38-bearing mice suggesting that AsGM1-positive cells in the liver of these mice may inhibit tumor growth in vivo. In conclusion, the host defense system of the liver from athymic nude or poly(IC)-treated mice possess AsGM1-positive cells that can suppress tumor implantation or tumor growth in the early stages of metastasis in liver.

Adenocarcinoma↗
PubMed1990

Suppression of hepatic lymphokine-activated killer cell induction by murine Kupffer cells and hepatocytes.

Murine lymphokine-activated-killer cell activity was readily induced by culturing spleen cells with 10 U/ml of interleukin-2 for 4 days. In contrast, very little activity was generated under the same culture conditions when nonparenchymal liver cells were used as the responding cells. It was concluded that Kupffer cells produced prostaglandin and interferon alpha/beta, which suppressed lymphokine-activated-killer induction because (a) induction of lymphokine-activated-killer activity from nonparenchymal liver cells was observed in the presence of indomethacin and anti-interferon alpha/beta antibody; (b) when adherent nonparenchymal liver cells, primarily Kupffer cells, were removed, lymphokine-activated-killer activity could be obtained with interleukin-2 alone; (c) coculture of Kupffer cells with nonadherent nonparenchymal liver cells in a two-chambered system inhibited lymphokine-activated killer cell induction in a dose-dependent manner; (d) exogenous prostaglandin E2 and interferon alpha/beta added at the start of culture inhibited interleukin-2-induced cytotoxicity and proliferation, whereas the other major prostaglandin species in the liver, prostaglandin D2, had little effect. These findings are distinctive with Kupffer cells because splenic macrophages did not exert such inhibition in parallel experiments. Moreover, the supernatant collected from the 24-hr culture of nonparenchymal liver cells contained greater than 20-fold more prostaglandin E2 and interferon alpha/beta than that from culture of spleen cells. In subsequent in vivo experiments, when interleukin-2 was given intraperitoneally to mice, the combination of indomethacin and anti-interferon alpha/beta antibody significantly enhanced lymphokine-activated-killer activity recovered from the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Indomethacin modulation of adriamycin-induced effects on multiple cytolytic effector functions.

The anticancer agent, Adriamycin (ADM), in addition to being a potent cytotoxic drug has been shown to be an effective immunomodulator. This study was undertaken to determine whether ADM-induced changes in the production of prostaglandins (particularly PGE2) are involved in ADM-associated modifications of selected host defenses. Spleen cells from normal or ADM-treated (5 mg/kg; day -5) C57BL/6 mice were assessed for the following activities: fresh (day 0) and cultured natural killer (NK), cytotoxic T lymphocyte, lymphokine-activated killer (LAK), Fc-dependent phagocytosis and tumoricidal macrophage. All activities were assessed with and without the addition of indomethacin, an inhibitor of the first step of the cyclo-oxygenase pathway of prostaglandin synthesis. Depending on culture conditions, the cytotoxic T lymphocyte and splenic tumoricidal macrophage activities were either unaffected or were augmented by ADM treatment of the spleen donor mice or by addition of indomethacin to the culture, and these effects were apparently independent of one another. In contrast, ADM treatment generally resulted in reduced NK and LAK activities relative to control and elevated Fc-dependent phagocytosis. The addition of indomethacin to the culture effectively reversed these effects. Furthermore, spleen cells from ADM-treated mice were found to produce twice the amount of PGE2 in culture compared to cells from untreated mice. Finally, the direct addition of PGE2 to NK cultures resulted in a dose-dependent inhibition of NK activity and the dose required was comparable to the amount of PGE2 produced by cultured spleen cells from ADM-treated mice. Taken together, these results indicate that at least some of the immunomodulatory effects of ADM are an indirect result of ADM-induced changes in PGE2 production.

Animals↗
PubMed1990

Prospective two-year followup of recombinant interferon-gamma in rheumatoid arthritis.

Seventy patients with rheumatoid arthritis (RA) completing a 12-week multicenter double blind trial comparing recombinant human interferon-gamma (r-IFN-gamma) with placebo were enrolled in a longterm prospective protocol evaluating r-IFN-gamma in RA. Forty (57%) patients after 1 year and 26 (37%) patients after 2 years continued the drug with sustained clinical benefit. Over 2 years, r-IFN-gamma was discontinued in 44 patients (lack of efficacy--25, withdrawn consent--7, noncompliant--4, suspected adverse drug reactions--2, concurrent illness--6). Two years of treatment with r-IFN-gamma were well tolerated with sustained clinical benefit in some patients with few significant adverse drug reactions.

Arthritis, Rheumatoid↗