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Biomedical subjects

R Cohen

Publications and source records attributed to R Cohen.

At least 469 records · Page 26Linked to original sources
PubMed1985

Diurnal administration of human growth hormone-releasing factor does not modify sleep and sleep-related growth hormone secretion in normal young men.

hGRF (iv 50 micrograms) was administered to 6 normal young adult males at 09.00 and 20.00 h on different days. Nocturnal GH secretion was monitored during polygraphic sleep recordings on both control nights and nights following hGRF administration. Sleep-related GH secretion and sleep parameters were not affected by diurnal hGRF administration.

Adult↗
PubMed1985

Serial changes in humoral and cellular immunity induced by prostaglandin E2 treatment of murine immune complex glomerulonephritis.

To examine the mechanism by which prostaglandin E2 (PGE2) inhibits the development of apoferritin (HAF)-induced immune complex glomerulonephritis (ICGN), weekly determinations of glomerular histologic conditions, blood urea nitrogen (BUN), total immunoglobulin levels, anti-HAF antibody, peripheral blood and splenic T cell subsets, and splenic suppressor cell activity were compared between mice receiving HAF and mice additionally treated with PGE2. PGE2 therapy prevented the development of glomerular hypercellularity and the increase in BUN concentration. Administration of PGE2 reduced anti-HAF IgG levels, but total IgM and IgG1, IgG2a, and IgG2b levels were unchanged. Mice receiving HAF alone demonstrated serial reductions in phenotypically identified peripheral blood pan-T cells and suppressor-cytotoxic T cells. PGE2-treated mice maintained normal levels of peripheral blood T cell subsets. Significant reductions in splenic total T cells and suppressor-cytotoxic cells occurred in mice receiving HAF as compared with normal mice. This reduction was offset by an increase in splenic B cells. PGE2 therapy prevented the decrease in splenic T cells at week 1, but not at week 4. Nonspecific suppressor cell activity, as measured by the ability of spleen cells from experimental mice to suppress a mixed lymphocyte reaction (MLR) or to suppress MLR-induced polyclonal IgG synthesis, was not different between the two groups. We conclude that prevention of HAF-ICGN by PGE2 is associated with a reduction in nephritogenic antibody production without an alteration in total immunoglobulin synthesis or the generation of nonspecific suppressor T cells. Changes in the percent of peripheral blood and splenic T cells and B cells may represent an effect of PGE2 on antigen-stimulated B cell proliferation.

Animals↗
PubMed1985

Lack of beta-adrenergic role for catecholamines in the development of hyperglycemia and ketonaemia following acute insulin withdrawal in type I diabetic patients.

In order to evaluate the role of beta-receptor mediated effects of catecholamines in the metabolic deterioration following insulin withdrawal in insulin-dependent diabetic patients we have measured in 5 patients metabolic substrate and hormone concentrations during a 6 hours arrest of insulin infusion, without or with a simultaneous infusion of propranolol. During insulin deprivation plasma epinephrine and norepinephrine increased slightly (from 107 +/- 10 ng/L to 173 +/- 6 ng/L and from 307 +/- 37 ng/L to 518 +/- 77/ng/L respectively (p less than 0.05), cortisol decreased physiologically, but growth hormone and glucagon were not significantly modified. Free insulin decreased progressively from 12.2 +/- 2.5 mU/L to 5.4 +/- 1.1 mU/L (p less than 0.01). Blood glucose and ketone bodies rose sharply before any significant change in catecholamine levels. Plasma free fatty acids and blood glycerol increased progressively and their rise appeared somewhat temporally related to the variations of catecholamine levels. The addition of propranolol to insulin deprivation did not modify the changes in hormone concentrations in spite of a slightly greater rise of epinephrine (from 78 +/- 4 ng/L to 179 +/- 7 ng/L, p less than 0.05) and norepinephrine (from 395 +/- 80 ng/L to 679 +/- 153 ng/L, p less than 0.05). The rises of glucose and ketone bodies were unaffected whereas the increases of free fatty acids and glycerol were slightly blunted. In conclusion, we have no evidence for a beta-adrenergic mediated role for catecholamines in the development of hyperglycaemia and ketonaemia in non-stressed insulin deprived diabetic patients, and only small evidence for a permissive effect on lipolysis.

Adult↗
PubMed1984

Characterization of the association of Electrophorus electricus acetylcholinesterase with sphingomyelin liposomes. Relevance to collagen-sphingomyelin interactions.

Electrophorus electricus acetylcholinesterase is a large polymorphic enzyme. Its native forms 18 S, 14 S and 8.5 S possess a tail having a collagen-like structure. It was suggested that this tail is involved in the anchorage of the enzyme at the terminal of the synapse. Watkins et al. [1] showed that all forms of the enzyme having a collagen segment also bind to sphingomyelin liposomes with almost no binding to phosphatidylcholine (PC) liposomes. In agreement with the above results, the binding of acetylcholinesterase reported here was independent of the following liposomal parameters (a) curvature, (b) the physical state of the bilayer, (c) the gel to liquid crystalline phase transition of sphingomyelin, (d) stereospecificity of the sphingomyelin, (e) acyl chain of the sphingomyelin. The binding was reduced with increasing PC content in sphingomyelin vesicles. The binding has no effect on the bilayer integrity. The enzymatic activity can be released from the vesicles by incubation with collagenase. The association of the enzyme with the liposomes had minimal effect on its kinetic parameters (Km, Vmax). The only detectable effect was increasing enzyme stability at low enzyme concentration. This suggested that the binding of the enzyme to sphingomyelin liposomes reduced its surface denaturation. Such association was not unique to acetylcholinesterase since collagen showed similar behavior. Collagen binding to sphingomyelin liposomes was 5-10-times larger than to PC liposomes. The exact details of the interaction of collagen and collagen-like peptides with sphingomyelin bilayers are yet unknown although it differs from the well documented hydrophobic or electrostatic interactions [7]. This work proposes hydrogen bonding as a third mechanism which involves the interface region of sphingolipids molecules and the collagen or collagen-like tail of acetylcholinesterase. This binding is also of interest due to its correlation to the accumulation of sphingomyelin and collagen during aging and the development of atherosclerosis in blood vessels of mammals.

Acetylcholinesterase↗
PubMed1984

Reversible subacute ethylene glycol monomethyl ether toxicity associated with microfilm production: a case report.

The first reported case of a possible toxic effect of ethylene glycol monomethyl ether (EGME) exposure in the microfilm manufacturing industry is described. Reversible subjective central nervous system complaints and asymptomatic hematopoietic effects occurred following inhalation and skin exposure to EGME. Hematopoietic changes occurred at airborne levels which have been associated with reproductive and teratogenic effects in other studies. This finding leads to a recommendation for further research to determine whether or not hematopoietic medical surveillance can provide an indication of not only EGME hematopoietic effects but also an indication of sufficient EGME exposure to affect human reproduction and fetal development.

Adult↗
PubMed1984

Herpes simplex virus persistence in mouse neuroblastoma (C 1300) cell cultures: role of interferon.

The Mp strain of herpes simplex virus type 1 (HSV1) induced a persistent infection in the mouse C 1300 neuronal cell line (clone N 115). C 1300 cultures infected at an MOI of 0.01 or 0.001 survived the initial infection and continued to produce infectious virus and viral antigens for 185 days and 31 days, respectively. Viral antigens were not detected in cultures no longer producing infectious virus; these "cured" cultures had comparable susceptibility to reinfection with HSV as previously uninfected C 1300 cells. While significant amounts of interferon were produced by C 1300 cells when challenged with Newcastle Disease Virus (NDV) or when treated with poly I:C, HSV-induced interferon could not be detected in either the acutely or persistently infected cell lines. The persistent state was not significantly altered by the addition of 1,000 units/ml of murine interferon alpha plus beta (MuIFN alpha + beta), nor was it affected by the addition of antibody to MuIFN. It appears that IFN does not play an important role in the establishment and/or maintenance of viral persistence in this neuronal system.

Animals↗
PubMed1984

Preparation and characterization of well defined D-erythro sphingomyelins.

A simple semisynthetic procedure for the preparation of various D-erythro sphingomyelins (SPMs), differing in their acyl chains, is described. They were prepared by one-step condensation of the desired free fatty acid with sphingosyl phosphorylcholine (SPC) using dicyclohexylcarbodiimide. The D-erythro SPMs were obtained in high purity, high yields and resemble bovine brain SPM in their chromatographic behavior, infrared, circular dichroism (CD) and proton NMR (PMR) spectra as well as in their rate of hydrolysis by Staphylococcus aureus sphingomyelinase. Multilamellar vesicles can be prepared from the semisynthetic SPMs. Their thermotropic behavior is dependent mainly on the acyl chain though it is also affected by the heterogeneity of the sphingosine base composition. Intact sealed small unilamellar vesicles (SUV) cannot be prepared from a single semisynthetic saturated SPM but can be prepared from their mixtures. This acylation procedure can also be applied for preparing simple neutral glycosphingolipids. The sphingolipids prepared by this method can be used to study metabolism, enzymology and physicochemical properties of D-erythro well defined simple sphingolipids.

Animals↗
PubMed1984

Reduction of increased levels of blood glycerol and ketone bodies by propranolol in human hyperthyroidism: role of the fall of the triiodothyronine level.

Hyperthyroid patients in the postabsorptive state have elevated levels of blood glycerol and ketone bodies (KB): this is believed to be due to increased lipolysis and ketogenesis. These increased glycerol and KB levels return toward normal after oral propranolol administration. In order to investigate the mechanism of action of propranolol in hyperthyroid patients, we compared the effects of the oral administration of propranolol with those of timolol, propylthiouracil (PTU), and a placebo. The placebo had no effect. The free thyroxine index, immunoreactive insulin level and glucagon level were not modified by propranolol, timolol, or PTU. Propranolol decreased the pulse rate (P less than 0.01) and the levels of serum triiodothyronine (T3; P less than 0.05), blood glycerol (P less than 0.01), and KB (P less than 0.01). Like propranolol, timolol decreased the pulse rate (P less than 0.01) but had no effect on the T3, glycerol, or KB levels. Propylthiouracil did not modify the pulse rate, but like propranolol, it decreased the T3 (P less than 0.05), glycerol (P less than 0.01) and KB (P less than 0.01) levels. These results suggest that the metabolic actions of propranolol are not caused by its hemodynamic effects nor its beta-blocking properties but are mediated by the decrease of the T3 level.

Adolescent↗
PubMed1984

Regulation of somatostatin secretion in man: study of the role of free fatty acids and ketone bodies.

We have investigated in normal subjects the possible role of plasma free fatty acids (FFA) and blood ketone bodies (KB) in the regulation of human somatostatin secretion. Heparin injected during the intravenous infusion of a fat emulsion raised FFA levels acutely from 0.4 +/- 0.1 to near 3 mmol/L. Plasma somatostatin-like immunoreactivity (SLI) rose from a mean (+/- SEM) basal value of 9.2 +/- 1.0 ng Eq S14/L to 20.0 +/- 6.0 ng Eq S14/L (P less than 0.05). Plasma immunoreactive insulin (IRI) level was unchanged and glucagon (IRG) concentration decreased from 156 +/- 20 to 107 +/- 2 ng/L (P less than 0.05). During this test, there was a rise not only in FFA but also in plasma triglycerides (TG) and in blood glycerol and KB levels. The infusion of a fat emulsion alone increased triglyceride and glycerol levels to a similar extent but induced also a mild rise of FFA (0.37 +/- 0.05 to 1.13 +/- 0.5 mmol/L, P less than 0.01), KB (78 +/- 12 to 360 +/- 45 mumol/L, P less than 0.01), and SLI (14.8 +/- 4.6 to 23.8 +/- 7.1 ng Eq S14/L, P less than 0.05). The induction by DL-Na-3-hydroxybutyrate infusion of a rise of KB was associated with a decrease of FFA (P less than 0.05) and SLI (P less than 0.05) without modification of IRI or IRG levels. Phentolamine infusion did not modify the SLI or glucagon response to acute elevations of FFA, whereas propranolol suppressed the increase of SLI without preventing the concomitant decrease of IRG.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1984

Fallopian tubal mucosal damage induced experimentally by Escherichia coli in the rabbit. A scanning electron microscopic study.

Pelvic inflammatory disease is the main cause of infertility due to a tubal factor. The importance of Gramnegative bacteria as major infecting organisms in pelvic inflammatory disease has been recently recognized. The predominant facultative pathogen found in tuboperitoneal fluid from women with salpingitis are coliform bacteria. This study describes an animal model for E. coli mediated tubal mucosa damage. E. coli (10(5)-10(9) bacteria 1 ml) was injected into the right Fallopian tube of sixty rabbits; the left tube injected with culture medium, served as a control. The luminal surface of the oviducts was examined by scanning electron microscope at various intervals after the injection. The degree of damage was found to be dose-dependent and maximal seven days after innoculation. The injury comprised of large areas of deciliation, severely shortened cilia, swollen and adherent throughout their entire length and disappearance of microvilli from the secretory cells. A process of regeneration began two weeks after the innoculation and was completed eight weeks later. Fertility studies carried out after completion of regeneration showed no difference in the ratio of corpora lutea/gestational sacs between the treated and control sides of individual pregnant animals. This model sheds light on the pathogenesis of tubal surface injury by E. coli and suggests that the major effects described are mediated through the endotoxin liberated from the cell wall of these bacteria and that, therefore, antibiotic treatment has no effect on the magnitude of injury. Endosalpingeal regeneration correlates well in this animal model with normal fertility suggesting that morphologic integrity of the surface epithelium may be a good criterion in assessing the reproductive capacity of the fallopian tube.

Animals↗
PubMed1984

Purification and characterization of the serotype c antigen from Actinobacillus actinomycetemcomitans.

The serotype c antigen from Actinobacillus actinomycetemcomitans was purified with fractional ethanol precipitation of cell-free culture supernatant, sequential ion-exchange chromatography, and gel filtration chromatography. The preparation obtained demonstrated a single precipitin line in immunodiffusion, immunoelectrophoresis, and crossed immunoelectrophoresis when rabbit antisera to serotype c whole bacterial cells were used. No immunological reaction was detected with antisera to serotype c lipopolysaccharide, indicating that lipopolysaccharide was not present in the preparation. The serotype c antigen was composed of 95% carbohydrate, 2% protein, and 3.1% phosphate. Gas chromatographic analysis of the antigen obtained from growth in either complex or chemically defined media revealed that the carbohydrate constituent was composed of 84 to 90.1% mannose, 4.8 to 16% glucose, 1.9% N-acetylglucosamine, 1.4% fucose, and 0.2% galactose. The present data suggest that A. actinomycetemcomitans serotype c antigen is predominantly a mannose-containing carbohydrate suggestive of a mannan.

Actinobacillus↗
PubMed1984

An in vitro gallium-67 lung index for the evaluation of sarcoidosis.

In the evaluation of the active alveolitis of pulmonary sarcoidosis, both the proportional lymphocyte count obtained by bronchoalveolar lavage and state of activation of the alveolar macrophage by gallium scanning are required. We injected 6 mCi (200 MBq) of 67Ga intravenously on 24 occasions in 13 patients with biopsy-proved sarcoidosis. Forty-eight hours later, patients were scanned with a rectilinear scanner and the generated scintigrams were evaluated using the NIH index. Seventy-two hours after injection, bronchoalveolar lavage was performed, and venous blood was sampled. The harvested lavage fluid was analyzed for absolute and proportional cell counts, and radioactivity was measured in blood and BAL fluid. An in vitro 67Ga index was generated and expressed as counts/100,000 alveolar macrophages/ml blood (mean, 0.0146 +/- 0.0087 SD). There was a significant relationship between the in vitro index and proportional lymphocyte BAL counts (r = 0.79; p less than 0.002) that was comparable to that obtained using the NIH index (r = 0.74; p less than 0.005). These data suggest that the in vitro index might offer a more objective assessment of 67Ga uptake by the lung, but this would require validation against clinical parameters in a prospective study.

Adult↗