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Biomedical subjects

D Samuel

Publications and source records attributed to D Samuel.

At least 235 records · Page 13Linked to original sources
PubMed1988

Exercise inhibits reproductive quiescence induced by exogenous melatonin in hamsters.

Voluntary exercise inhibits the reproductive regression associated with a short photoperiod in male or female hamsters. The question addressed by the present study was whether exercise would also attenuate the reproductive regression associated with injection of exogenous melatonin. In male hamsters exercise inhibited the testicular regression, decline in gonadotropin secretion, and reduction in testosterone release associated with two daily injections (15 micrograms) of melatonin in pinealectomized hamsters on long days. After the reproductive system of the sedentary melatonin group had regressed, one-half of these hamsters were placed in cages with exercise wheels. Access to the exercise wheels stimulated testicular recrudescence and restored gonadotropin secretion to levels found in vehicle-injected hamsters. Sedentary female hamsters injected with melatonin tended to go into a state of constant diestrus associated with daily afternoon increases in serum luteinizing hormone, whereas most exercising hamsters injected with melatonin generally continued having regular estrous cycles with proestrus luteinizing-hormone surges. The ability of exercise to inhibit the effect of exogenous melatonin in pinealectomized hamsters suggests that exercise acts, at least in part, by mechanisms other than altering melatonin secretion.

Animals↗
PubMed1988

The stimulation of IgM rheumatoid factor from human B lymphocytes by rheumatoid arthritis complement-activating immune complexes.

Immune complexes from rheumatoid arthritis (RA IC) and Hodgkin's disease (HD IC) sera were separated on an anti-C3g affinity column and their ability to stimulate the production of IgM and IgM RF by normal and RA B lymphocytes tested in a culture system in vitro. RA IC stimulated IgM production of which up to 91.3% had IgM RF activity. HD IC were incapable of stimulating the production of IgM and IgM RF. The stimulation of IgM and IgM RF production by RA IC required de novo protein synthesis. Both RA IC and HD IC were capable of significantly inhibiting (from 47.6 to 72.0%) pokeweed mitogen (PWM)-induced and goat F(ab)2 antihuman mu-induced B lymphocyte proliferation. Thus it is proposed that IC present in human pathological sera may regulate immunoglobulin production by an effect on B lymphocyte proliferation while some may, in addition, be capable of inducing IgM RF production from such cells.

Antigen-Antibody Complex↗
PubMed1988

Liver transplantation for protoporphyria. Evidence for the predominant role of the erythropoietic tissue in protoporphyrin overproduction.

Protoporphyria is an inherited disorder of heme biosynthesis characterized by an overproduction of protoporphyrin in the erythropoietic and hepatic tissues, the relative contribution of which in the metabolic disorder has not been directly quantitated. Excess protoporphyrin is eliminated solely by the liver into the bile and feces. We describe the case of a patient with protoporphyria complicated by severe cirrhosis in whom liver transplantation was performed and resulted in almost complete disappearance of skin photosensitivity manifestations and reduction in the level of protoporphyrin in erythrocytes. However, the level of protoporphyrin in feces was not markedly different before and after liver transplantation, which suggests that overproduction of protoporphyrin was unchanged. These findings are consistent with the view that the diseased liver and ensuing low hepatic clearance of protoporphyrin contributed to accumulation of protoporphyrin in the body and that, at least in this patient, the role of the hepatic tissue in the overproduction of protoporphyrin was small in comparison with that of the erythropoietic tissue.

Adult↗
PubMed1988

[Cirrhosis and biliary lithiasis in France: a postmortem study].

The prevalence of cholelithiasis was estimated in 434 cirrhotic patients and 1582 non cirrhotic patients necropsied at Hôpital Beaujon from 1976 to 1984. The overall prevalence of cholelithiasis was significantly higher in cirrhotic than in non cirrhotic patients, 26.3 p. 100 and 20.3 p. 100, respectively. The prevalence of cholelithiasis was higher in cirrhotic than in non cirrhotic patients, whether male or female and at any age, except in women over 60 years and in men over 80 years; in these groups, the prevalence of cholelithiasis in non cirrhotic patients was especially high and therefore did not significantly differ from that in cirrhotic patients. The cause of cirrhosis did not significantly influence the prevalence of cholelithiasis; however, although the number of studied patients was small, the prevalence of cholelithiasis seemed to be particularly high in primary biliary cirrhosis. The prevalence of cholecystectomy was lower in cirrhotic than in non cirrhotic patients, which suggests that cholelithiasis might be less often symptomatic and/or less often complicated in the former than in the latter.

Adult↗
PubMed1987

The occurrence of 2'-5' oligoadenylates in Escherichia coli.

The use of a highly specific radioimmunoassay and of HPLC permitted us to confirm the occurrence of 2'-5' oligoadenylates [p chi (A2'p5')nA] in several strains of Escherichia coli. Cellular concentrations of 2'-5' oligoadenylates ranged from 50 nM to 300 nM. The mixture of 2'-5' oligoadenylates consisted primarily of pppA2'p5'A, pA2'p5'A,A2'p5'Ap and A2'p5'A under normal conditions of growth. None of them activated RNase L. Infection of the bacteria with the single-stranded DNA phage M13 or induction of a heat-inducible, non-lytic mutant of phage lambda led to a significant increase in the total pool of 2'-5' oligoadenylates, paralleling the progressive inhibition of growth. Likewise, the inhibition of protein synthesis with chloramphenicol stimulated the accumulation of 2'-5' oligoadenylates. Furthermore, the inhibition of bacterial growth by either phage or by chloramphenicol brought about a change in the composition of the 2'-5' oligoadenylate pool; 5'-phosphorylated 2'-5' oligoadenylates accumulated and became the major components. The findings indicate a parallelism between the effects of viral infection on the synthesis of 2'-5' oligoadenylates in eukaryotes and similar effects subsequent to phage growth in the bacterium E. coli.

Adenine Nucleotides↗
PubMed1987

AL721, a novel membrane fluidizer.

AL721, which is a novel lipid mixture extracted from egg yolks, is believed to be a therapeutic pharmacologic agent. AL721 interacts with membranes of various types of cells with a common mode of action. AL721 modifies cellular membrane composition and fluidity through passive extraction and/or exchange of cholesterol. Physiologically diminished cell function due to rigidification of its membrane is reversible both in vitro and in vivo by AL721. Fluidization of aged membranes with AL721 has been shown to restore brain serotonin receptor function both in vitro and in vivo. AL721 can also successfully restore deficient immune responsiveness of lymphocytes to mitogen stimulation in aged subjects. Drug tolerance to morphine and ethanol develops upon elevation of the viscosity of neuronal cell membranes in order to counteract the fluidization effect of the drug. Treatment of rigidified cellular membranes with AL721 in vivo can markedly reduce withdrawal symptoms. The virucidal effect of AL721 on the human immunodeficiency virus is believed to operate by lowering of viral membrane cholesterol thus interfering with the binding of the viral antigen to the host cell. Non-toxicity of AL721 is clearly demonstrated in animal and human safety studies.

Aged↗
PubMed1987

Emergency liver transplantation for fulminant hepatitis.

Orthotopic liver transplantation was done in 17 patients with fulminant hepatitis. The cause of the liver disease was infection with hepatitis B virus, or co-infection with hepatitis B virus and hepatitis D virus, or infection with hepatitis A virus in 6 patients; drug hepatotoxicity in 5; and indeterminate in 6. Grafts from incompatible blood groups, steatotic grafts, or reduced-size grafts were used in 5, 4, and 4 patients, respectively. Of the 17 patients, 5 died: 2 of early liver failure due to the poor quality of the graft, 1 presumably of accidentally transmitted acute infection with the human immunodeficiency virus, and 2 of decerebration occurring during or immediately after surgery. The 12 other patients were alive 2 to 15 months after transplantation.

Acute Disease↗
PubMed1987

[Immunologic surveillance of liver transplant patients using monoclonal antibodies against lymphocyte subpopulations].

A precise immunological surveillance of liver graft recipients can allow the adaptation to each patient of an adequate immuno-suppressive treatment. In 11 liver-transplanted patients (7 primitive biliary cirrhoses, 2 post-hepatic cirrhoses, one bile duct atresia with one antitrypsin deficit) different lymphocyte subpopulations were tested before transplantation and at days 3, 5, 7, 15, 30, 60 and 120 after grafting using OKT3, OKT4, OKT8 (Orthoclone, France). In 6 patients presenting one or more rejections, the (T4+):(T8+) lymphocyte ratio was significantly increased during the days preceding rejection. In all cases, the (T4+):(T8+) ratio increase was linked to a (T4+) helper lymphocyte augmentation. In the 6 patients who did not present any rejection, the (T4+):(T8+) ratio did not increase at long term. A decrease of the (T4+):(T8+) ratio, along with an augmentation of (T8+) lymphocytes, was noticed at long term in patients free of chronic rejection. The evolution of T lymphocyte populations, followed using monoclonal antibodies and mainly the (T4+):(T8+) ratio, can provide a test for rejection predictability of for the prognosis of tolerance to liver allografts.

Antibodies, Monoclonal↗