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Biomedical subjects

S Biswas

Publications and source records attributed to S Biswas.

At least 19 recordsLinked to original sources

Effect of heat-shock on Plasmodium falciparum viability, growth and expression of the heat-shock protein 'PFHSP70-I' gene.

Cultures of the human malaria parasite Plasmodium falciparum were subjected to heat-shock for varying times and temperatures and then tested for their viability, growth and expression of heat-shock protein. Results show that the majority of parasites remained viable after heat-shock but their growth was affected. However, the expression of the heat-shock protein 'PFHSP70-I' gene was enhanced after heat-shock. We conclude that malarial parasites are able to survive in vivo during fever probably due to the overexpression of the heat-shock protein gene.

Animals

Sulfhydryl groups of Mimosa pudica tubulin implicated in colchicine binding and polymerization in vitro.

The important characteristic of novel Mimosa pudica tubulin is its ability to bind colchicine only when dithiothreitol is included in the isolation buffer, indicating the involvement of sulfhydryl groups in colchicine binding. Modification of sulfhydryl groups by a sulfhydryl modifying agent also affects the normal assembly of tubulin into microtubules, as revealed by electron microscopic and spectrophotometric studies. The number of free sulfhydryl groups present in tubulin protein responsible for both colchicine binding and polymerization has been found to be 4, distributed in alpha and beta subunits, and is distinctly different from the number reported for animal tubulin.

Binding Sites

Neuropeptide Y immunoreactivity in the spleen and thymus of normal rats and following adjuvant-induced arthritis.

Immunoreactive neuropeptide Y (irNPY) was detected by radioimmunoassay within the rat thymus and spleen. Total spleen and thymus irNPY contents in control animals were 77 +/- 3 ng and 23 +/- 1 ng respectively (means +/- S.E.M., n = 10). Total tissue contents of irNPY 14 days following bilateral adrenalectomy or induction of inflammatory arthritis were not significantly altered compared to controls. Most spleen irNPY coeluted with synthetic NPY after reversed-phase high-performance liquid chromatography, but two peaks of irNPY were detected in thymic extracts. This suggests that NPY may be differentially expressed in tissues of the immune system.

Animals

Plasmodium falciparum invades human red cells via a parasite produced glycosidase.

This report describes that P. falciparum produces a neuraminidase like activity on invasion into erythrocytes in culture on the basis of biochemical and immunological investigations. This activity in turn modifies the surface glycoprotein receptors of red cells and may be of help in the inhibition of further invasion by merozoites. The characterization of this enzyme activity may help elucidate the mechanism of cerebral malaria.

Animals

Reversal of chloroquine resistance with verapamil in P. berghei in vivo.

The effects of verapamil on the parasite susceptibility to chloroquine were examined in mice infected with chloroquine-sensitive and chloroquine-resistant lines of Plasmodium berghei. Verapamil in a dose of 10-50 mg/kg daily s.c. for 4 days did not affect the growth of both sensitive and resistant parasites. When verapamil in the same dose range was combined with 1.5 mg/kg chloroquine diphosphate, the chloroquine-sensitive parasites became more susceptible to chloroquine. Similarly, verapamil severely suppressed the growth of chloroquine-resistant parasites in combination with 3 mg/kg (base) of chloroquine, but the reversal of resistance was not complete. Thus, still higher doses of verapamil, which are not tolerated by the host, are required for the complete reversal of resistance.

Animals

Role of catecholamines in mediating messenger RNA and hormonal responses to stress.

The role of catecholamines in regulating the neuroendocrine stress response is controversial. We have investigated the effects of unilateral ventral noradrenergic bundle (VNAB) lesions on corticotrophin-releasing factor (CRF) and proenkephalin A mRNA responses in the parvocellular paraventricular nucleus (pPVN) to both physical and psychological stresses. We have also determined the effects of direct bilateral PVN lesions on CRF mRNA, plasma ACTH and corticosterone responses to psychological stress. 6-OHDA lesions whether to the VNAB or direct to the PVN did not result in any change in basal levels of CRF mRNA. Depletion of endogenous noradrenaline following unilateral lesions of the VNAB did not affect the CRF mRNA or the proenkephalin A mRNA response to stress. These data suggest that noradrenergic pathways are not involved in maintaining basal levels of CRF mRNA and that the noradrenergic input through the VNAB does not mediate the accumulation of CRF and proenkephalin A mRNAs in response to these stressors. Direct bilateral lesions to the PVN prevented the accumulation of CRF mRNA but not the ACTH and corticosterone responses to restraint stress. This suggests that monoamines are involved in the regulation of CRF mRNA through a mechanism independent of CRF-41 secretion.

Adrenocorticotropic Hormone

Neuropeptide Y and tyrosine hydroxylase mRNA levels in the locus coeruleus show similar increases after reserpine treatment.

In situ hybridisation histochemistry was used to study the effect of intra-peritoneal reserpine administration on messenger RNA (mRNA) levels in the locus coeruleus (LC) of the rat. 48h after injection, levels of mRNA encoding tyrosine hydroxylase (TH) and neuropeptide Y (NPY) in the LC increased to approximately 250% of control values (p less than 0.05). The level of beta-tubulin mRNA was unaffected by reserpine administration. The similar and selective increase in TH and NPY mRNA in the LC following reserpine administration suggests that NPY may play a role in the neurotransmitter function of this catecholaminergic nucleus.

Animals

Substance P and substance K in the rat hypothalamus following monosodium glutamate lesions of the arcuate nucleus.

Adult rats treated neonatally with monosodium glutamate (MSG) exhibit lesions in the arcuate nucleus of the hypothalamus. Following MSG lesioning, dopamine content in median eminence/arcuate nucleus (ME/AN) tissue extracts declined by 60-70%. Substance P (SP) content as determined by radioimmunoassay was significantly decreased in the paraventricular nucleus (PVN) (531 +/- 30 pg, mean +/- SEM) compared to controls (871 +/- 110 pg) but was unchanged in ME/AN extracts. Substance K (SK) content decreased to 257 +/- 20 pg in the PVN of lesioned animals compared to controls (367 +/- 31 pg) and the ME/AN content of SK was also significantly decreased (236 +/- 36 pg compared to control levels of 619 +/- 65 pg). The CRF-41 content of the PVN and ME/AN was unchanged by MSG lesioning, indicating that these areas are not affected by MSG. The partial depletion of SP and SK in the PVN following MSG treatment provides evidence that at least some of the neurokinin content of the PVN may originate in cell bodies of the arcuate nucleus. However, the lack of response of ME/AN SP to MSG treatment may suggest that the arcuate nucleus is not the major source of SP in the median eminence.

Animals

Fructose and hormone levels in semen: their correlations with sperm counts and motility.

Levels of fructose, growth hormone (GH), prolactin (HPr), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and 5alpha-dihydrotestosterone (DHT) were determined in semen. The samples were obtained from patients attending an infertility clinic and separated into four groups according to the number of spermatozoa. Levels of HPr, LH, and FSH showed significant positive correlations with sperm counts. Significant differences in fructose and hormone levels were found between various groups. Expressed as concentrations of hormones or fructose per milliliter of semen, none of the hormones showed a significant negative correlation with sperm motility whereas fructose showed a significant negative correlation. Expressed as amounts per ejaculate of semen, only prolactin showed a significant positive correlation with sperm motility. The significance of these findings is discussed.

Cell Count

Graft interposition splenocaval shunt for total or selective decompression of portal hypertension.

A new operation for selective or total decompression of the portal venous system in cases of intrahepatic portal hypertension is described. It involves interposition of a large-caliber Dacron graft between the splenic vein and the inferior vena cava. The graft-interposition splenocaval shunt is performed readily and quickly, satisfying the variable hemodynamic needs of patients with portal hypertension. It can be either selective (S-SCS) or total (T-SCS) from the beginning, or a T-SCS may be converted subsequently to a S-SCS should surgically induced hepatic decompensation supervene. It is less demanding technically than distal splenorenal shunt (D-SRS). The S-SCS conserves portal venous perfusion of the liver, preserves hepatocellular function and architecture at the preoperative levels, avoids precipitation of postshunt portal-systemic encephalopathy, and decompresses gastric-esophageal varices with prevention of further variceal bleeding even better than D-SRS. One hundred percent graft patency has been obtained, and the surgical results have been superior to those following portacaval shunt in patients with large liver blood flow and relative benignity of the liver disease, be it cirrhosis or noncirrhotic portal fibrosis. In patients with advanced cirrhosis, variceal bleeding, and small liver blood flows, T-SCS would be indicated. Patients of this category obtained inferior surgical results and had operative deaths (16.7%) following S-SCS. The concept of the operation has merits and deserves further evaluation.

Adolescent

Inhibition of puerperal lactation. A double blind study of bromocriptine and placebo.

Bromocriptine and placebo were randomly allocated for three weeks to 52 postpartum patients requiring lactation suppression. Bromocriptine significantly lowered plasma prolactin levels and suppressed breast milk, breast pain and engorgement quicker than placebo. No side-effects were noted and rebound lactation did not occur. Menstruation appeared to re-start sooner when Bromocriptine was given.

Bromocriptine

Prolactin in amniotic fluid: its correlation with maternal plasma prolactin.

Prolactin concentrations in amniotic fluid from 319 women with normal pregnancies and 29 women with complicated pregnancies were determined by radioimmunoassay. Prolactin levels varied from 36 ng/ml to 1800 ng/ml mean +/- S.D. = 408 +/- 297) in the normal pregnancy group but showed no definite pattern of rise or fall during pregnancy. No difference in levels was found in complicated pregnancies. Prolactin concentrations in the plasma from 203 of these women were also assayed. The levels in the amniotic fluid were about 9 fold higher than those in the plasma. There was no significant correlation between amniotic fluid and plasma levels of prolactin.

Amniotic Fluid