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Biomedical subjects

I Das

Publications and source records attributed to I Das.

At least 55 records · Page 3Linked to original sources
PubMed1996

Hypothalamic and plasma total nitrate/nitrite concentrations in spontaneously hypertensive rats.

Stable end-products of nitric oxide (NO) metabolism, nitrates and nitrites, were measured in hypothalamic extracts and plasma samples of Okamoto spontaneously hypertensive (SH) rats. The mean total nitrate/nitrite concentration was significantly lower in the hypothalami of SH rats compared with the normotensive Wistar Kyoto (WKY) control animals (P < 0.01). In contrast, their plasma concentrations were significantly higher (P < 0.05). These results indicate that the hypertensive state in SH rats is associated with a diminished production of hypothalamic NO, while the raised plasma nitrate/nitrite levels could reflect an increased compensatory endothelial NO synthase activity in these animals compared with the WKY controls.

Animals↗
PubMed1996

Steroid modulation of neuropeptide Y-induced luteinizing hormone releasing hormone release from median eminence fragments from male rats.

Neuropeptide Y (NPY) has been shown to stimulate hypothalamic release of luteinizing hormone-releasing hormone (LHRH) both in vitro and in vivo. In female rats, NPY facilitation of LHRH release is greatly augmented in advance of preovulatory LHRH surges, likely via the actions of ovarian steroids. However, the role of NPY in regulating LHRH release in male rats and the effects of testicular hormones on LHRH responses to NPY in males are not well understood. The objective of the present studies was to determine whether NPY stimulates LHRH release in vitro from hypothalamic tissue of male rats, and whether these effects could be modulated by testosterone (T). Mediobasal hypothalamic (MBH) or median eminence (ME) fragments from either sham-operated or castrated male rats (7 days) were placed in superfusion chambers and superfused with M199 for a 30-min baseline, 30-min challenge with NPY (10(-7)M), and a final 30-min challenge with 56 mM KCl. One-milliliter fractions were collected every 10 min and average LHRH release values over the 30-min periods were compared among groups. NPY (10(-7)M) produced a significant increase in LHRH release from the MBH and ME from intact animals. In contrast, the same dose of NPY did not stimulate LHRH release from tissues from castrated animals; only with a higher dose of NPY (10(-6)M) were the effects of NPY on LHRH release significant. Potassium challenge (56 mM KCl) significantly stimulated LHRH release from the ME of both intact and castrate male rats suggesting that all tissues were able to respond to a stimulus, and that castration did not alter the responsiveness of the LHRH neuron to a nonspecific secretagogue. To determine the extent to which T regulates the sensitivity of LHRH responses to NPY, male rats were castrated and implanted with T capsules that maintained either low (1.24 +/- 0.06 ng/ml) or high (2.17 +/- 0.31 ng/ml) physiological plasma levels of T. Treatment with the higher dose of T restored the ability of NPY to stimulate LHRH release from the ME tissues. These results demonstrate that NPY stimulates LHRH release from the hypothalamus in vitro, and that gonadal steroids, in this case T and/or its metabolites, modulate the responsiveness of the LHRH neuron to NPY. Based on these data from intact and castrate-derived tissues, it appears that steroids are necessary to maintain LHRH responsiveness to NPY receptor stimulation.

Animals↗
PubMed1996

Pyomyositis: an unusual infection due to staphylococcus aureus.

Pyomyositis is a primary pyogenic infection of skeletal muscle, leading to the formation of intramuscular abscesses. Although common in tropical climates, it is infrequent in temperate zones. We report a patient who developed the condition without travelling to tropical areas.

Climate↗
PubMed1995

Elevated platelet calcium mobilization and nitric oxide synthase activity may reflect abnormalities in schizophrenic brain.

Schizophrenia has a diverse nature of clinical symptoms and a number of hypotheses have been suggested to explain its aetiological basis. In this study we have examined two aspects of membrane function, receptor-activated calcium mobilization and calcium activated nitric oxide synthase activity in schizophrenic subjects. Thrombin induces mobilization of calcium ions from intracellular stores. The platelet response of drug naive schizophrenics was found to be significantly increased over a range of thrombin concentrations (0.01 to 0.60 U/ml) compared to control subjects. Possible involvement of nitric oxide (NO) in the aetiology of schizophrenia was investigated. NO has been functionally linked to both dopaminergic and glutamatergic systems both of which are strongly implicated in the biochemical pathology of schizophrenia. Nitric oxide synthase (NOS) activity was determined in platelets of controls, schizophrenic and panic disorder subjects. Enzyme activity was found to be significantly higher in platelets of drug naive schizophrenic subjects compared to controls, drug treated schizophrenics and panic disorder subjects. It is suggested that there is an imbalance of the calcium-induced L-arginine- nitric oxide pathway in platelets of schizophrenic subjects which may be modified by neuroleptic treatment. This imbalance may be mirrored in the central nervous system in particular at the NMDA receptor. It is possible that such a disturbance in the L-arginine-nitric oxide pathway may have pathological implications in the aetiology of schizophrenia.

Adult↗
PubMed1995

The inter-relationship between polyamines and the L-arginine nitric oxide pathway in the human placenta.

Nitric oxide (NO) and polyamines are both products of L-arginine metabolism. In placental villous tissue NO and polyamines have been shown to be synthesized although the physiological significance is not known. We have measured polyamine (putrescine, spermidine and spermine) concentrations and nitric oxide synthase activities (NOS) in first trimester and term placentae from normal and abnormal pregnancies, but no difference was observed in polyamine concentrations between normal term and placentae from growth-retarded and pre-eclamptic pregnancies. Significantly higher levels of polyamines were found in first trimester when compared to normal term placentae and there was a significant correlation between NOS activity and the cellular polyamine levels. Cultures of a trophoblast cell line, BeWo, have been used to study the interaction of added polyamines on NOS activity. Although there was a general tendency for all the polyamines to inhibit NOS activity only putrescine was able to significantly inhibit NO production by these cells. It is thought that the L-arginine-NO-polyamine pathway may have a physiological role during pregnancy.

Amino Acid Oxidoreductases↗
PubMed1995

Potent activation of nitric oxide synthase by garlic: a basis for its therapeutic applications.

Garlic (Allium sativum L.) is thought to have a variety of therapeutic applications including inhibition of platelet aggregation. Many of the therapeutic actions of garlic parallel the physiological effects of nitric oxide and may be explained by its ability to increase nitric oxide synthase activity intracellularly. Our studies showed that both water and alcoholic extracts of garlic are very potent inhibitors of platelet aggregation induced by epinephrine and ADP. Similar dilutions of garlic extract also activated nitric oxide synthase activity in isolated platelets in vitro. The same extract was also very effective in activating nitric oxide synthase activity in placental villous tissue. The addition of garlic extracts increased nitric oxide synthase activity in a dose-dependent manner. Nitrite levels in the supernatants of incubated placental villous tissue were similarly increased. Activation of calcium-dependent nitric oxide synthase and the subsequent production of nitric oxide is probably the most novel mechanism yet claimed by which garlic can exert its therapeutic properties.

Adenosine Diphosphate↗
PubMed1994

Elevated platelet phosphatidylinositol bisphosphate in mediated schizophrenics.

Levels of phosphatidyl inositol 4,5-bisphosphate (PIP2) have been measured in platelets from schizophrenic and healthy subjects by means of an immunoassay. Resting platelets from schizophrenic patients contained a significantly increased amount of PIP2 compared to controls. The agonist-stimulated hydrolysis of PIP2 in platelets from the schizophrenic group was also significantly greater than that in platelets from the control group. PIP2 plays an important role in cell signalling, and the observed abnormality may be reflected by an impairment in signal transduction via the inositol phospholipid pathway.

Adult↗