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Biomedical subjects

S Biswas

Publications and source records attributed to S Biswas.

At least 145 records · Page 8Linked to original sources
PubMed1996

Studies on prosthetic valve function--a transesophageal echocardiographic assessment.

Haemodynamic assessment was done by colour flow mapping and Doppler interrogation by both Transthoracic (TTE) and Transesophageal echocardiography (TEE) in 40 consecutive patients (mean age 36.6 +/- 12.35 years) with prosthetic valves. There were 30 cases of mitral (MVR) and 12 aortic (AVR) valve replacement. Major purpose of the study was to detect the sensitivity of TEE in detecting prosthetic valve malfunction particularly in comparison to TTE. Pannus was detected in 3 and 8 cases of MVR (p < 0.01) by TTE and TEE respectively; however, TEE was found to be of equal status in detecting pannus over AV (2 cases). Physiological regurgitation in MVR and AVR was detected in 13% and 25% by TTE and 20% and 33% by TEE respectively. Paravalvular leak was detected in 3 cases of MVR by TEE compared to only case by TTE. Though it is difficult to deduce any specific conclusion from this small number of patients, there is definite trend to higher sensitivity in detecting disorders with TEE specially for mitral prostheses.

Adult↗
PubMed1995

Receptor for myo-inositol trisphosphate from the microsomal fraction of Vigna radiata.

The microsomal fraction from mung-bean (Vigna radiata) hypocotyl was found to contain Ins (1,4,5)P3- and Ins(2,4,5)P3-binding activity. Preincubation of the microsomal fraction with thiol-containing reagents reduced specific InsP3 binding. A single class of binding site with a Kd value of 1.5 nM and Bmax. of 1.1 pmol/mg of protein was detected. Other myo-inositol phosphates exhibited little affinity for this protein. The binding protein was purified to homogeneity and the molecular mass of the native form recorded as 400 kDa. However, under denaturing conditions the molecular mass was 110 kDa, suggesting that the protein is a homotetramer. That this protein is associated with Ca2+ release was confirmed by including it in proteoliposomes and adding Ins(1,4,5)P3 or Ins(2,4,5)P3. The affinity of Ins(1,4,5)P3 is 3-fold higher than that of Ins(2,4,5)P3. The binding affinity of InsP3 is also reflected in the extent of Ca2+ released from the microsomal fraction. Heparin inhibits binding of InsP3 to the protein, the K1/2 being 0.26 microM. It is also shown that the protein acts as a receptor for InsP3 with characteristics of high affinity and low density.

Calcium↗
PubMed1995

Lack of natural killer cell augmentation in vitro by human interferon gamma in a subset of patients with systemic sclerosis.

Systemic sclerosis (SSc) is a generalized connective tissue disorder characterized by fibrosis of skin and various viscera. Natural killer (NK) cells are a subset of lymphocytes that can lyse targets without prior sensitization. Few studies have tried to assess NK cell function in patients with SSc. To evaluate NK cell cytotoxicity in patients with SSc and to see the extent of its augmentation in vitro by human interferon (hIFN) gamma in the clinical subset of limited and diffuse cutaneous diseases, we evaluated 27 patients with SSc and 22 age- and sex-matched controls by 51Cr release assay. Fifteen patients had limited cutaneous disease (mean disease duration 6.2 +/- 2.7 years) and 12 diffuse cutaneous disease (mean disease duration 5.7 +/- 2.4 years). Patients with limited SSc had significantly higher baseline NK cell function than controls (p < 0.05) and the augmentation following in vitro stimulation with hIFN gamma was negligible. Patients with diffuse SSc had lower baseline NK cell cytotoxicity than controls but this was not statistically significant. Augmentation with hIFN gamma in this group was comparable to controls. This study suggests that NK cells may have a role in the pathophysiology of this disease.

Adult↗
PubMed1995

In vitro antimalarial activity of monoterpenic fragment analogues of aplasmomycin.

Synthetic analogues of a monoterpenic fragment of aplasmomycin were tested for their antimalarial activity in Plasmodium falciparum culture in vitro. The antimalarial activities of these agents were evaluated in chloroquine sensitive strains. Parasite growth was inhibited in a dose dependent manner in the presence of the synthetic compounds (3-9).

Animals↗
PubMed1995

Humoral immune responses to the Plasmodium falciparum antigen Pf155 RESA in adults with differential clinical conditions from an Indian zone where malaria is endemic.

Ring infected erythrocyte surface antigen of Plasmodium falciparum (Pf155/RESA) has been considered as a vaccine candidate. However, the relative immunogenicity of this antigen has not been studied in Indian populations. Pf155/RESA was investigated for its immunogenicity by studying humoral immune responses against Pf155/RESA and Pf155/RESA derived peptides (P1, P2 representing immunodominant epitopes from the 3' and P3 from the 5' repeat regions) by erythrocyte membrane immunofluorescence (EMIF) assay and by enzyme linked immunosorbent assay (ELISA) in P. falciparum primed donors living in hyperendemic malarious areas (Orissa State, India) where P. falciparum infections are highly prevalent. Subjects of different clinical status namely acute (A), clinically immune (CI) and acute with history of repeated P. falciparum infections (R) were included in this study. All the donors were seropositive against the crude antigen. There was considerable variation in the responses among the donors. While humoral responses in the plasmas against the P2 peptide (EENV)4 were significantly higher in magnitude and in frequency in the CI donors than in the A donors, no positive response was seen in the R donors. The responses to the peptides P1 (EENVEHDA)2 and P3 (DDEHVEEPTVA)2 were poor both in the A and in the CI groups. Whereas, most of the R donors were seropositive against the P3. The present results indicate that Pf155/RESA contains B cell epitopes which were recognized differently by the immune system of individuals living in malaria-hyperendemic areas of India who have been primed by natural infection. Our studies also suggest that in order to investigate the possible functional role of a given antigen, study of immune responses against the antigen in donors of different clinical status may be useful.

Adult↗
PubMed1995

Application of simple peptide ELISA for stratification of malaria endemicity.

A serological investigation was conducted in north India to determine malaria endemicity based on the antibody levels against a nonapeptide RI (EENVEHDA-Cys) from the P. falciparum antigen Pf 155/RESA. P. falciparum sonicated crude antigen was also used in the study. Subjects of all age groups from various strata of malaria endemicity were included in this study. A total of 4273 finger prick blood samples from 49 villages of five districts were collected during January to March 1991 which is a non-transmission season and the antibody levels were estimated by ELISA. Although a good correlation was found between the antibody titre to the RI peptide and that to the crude antigen, the most consistent results were obtained with the RI peptide. When compared with the annual parasite index (API) values, an established method for defining malaria endemicity, mean anti-RI antibody titres obtained from several villages within a single zone correlated (r = 0.94, p = 0.023) with mean API value of the area. Thus, our results suggest that by using the RI peptide as antigen in seroepidemiology, it is possible to stratify malaria endemicity. We didn't distinguish between endemicity of Pv and Pf since each area experiences cycle of transmission of P. vivax followed by P. falciparum and our sera were from individuals having no fever.

Animals↗
PubMed1994

Enhanced expression of Plasmodium falciparum heat shock protein PFHSP70-I at higher temperatures and parasite survival.

The effect of various body temperatures, encountered during malaria fever, on the synthesis of Plasmodium falciparum heat-shock protein called PFHSP70-I and parasite growth rates among five different isolates are described. The results show that after the exposure of parasites at 39 degrees C for 30 min the amount of PFHSP70-I in all five isolates increased markedly and significantly, whereas parasite growth rates and the amount of total blood stage antigens remained almost unaffected. This indicates that the PFHSP70-I gene responds to heat-shock by producing higher amounts of PFHSP70-I protein, presumably to protect the parasite from being killed during malaria fever.

Animals↗
PubMed1994

Ectopic vasopressin expression in MMTV-Wnt-1 transgenic mice modifies mammary tumor differentiation and pathology.

A transgenic mouse model has been developed to test the involvement of ectopic neuropeptide production as a secondary factor in cancer. Mice bearing a mouse mammary tumor virus-vasopressin (MMTV-VP) fusion transgene synthesized authentic vasopressin in mammary ducts and alveoli, but this had no effect on mammary gland development and growth. Mice bearing the MMTV-VP transgene were then mated with mice bearing the MMTV-Wnt-1 transgene to produce bitransgenic animals. Two types of mammary tumor develop in MMTV-Wnt-1 mice; type A mammary adenocarcinomas are uniform with fine acinar structure composed of small epithelial cells arranged to form round cavities and elongated tubules, while adenocarcinoma type B tumors have acinar areas, cystic spaces filled with blood or fluid, intracystic papillary projections, and cords as well as sheets of cells. Compared to the MMTV-Wnt-1 mice, the bitransgenic animals developed proportionally less type B tumors. Further, type B mammary adenocarcinomas from bitransgenic mice exhibited increased proliferation and growth, as judged by mitotic index and argyrophilic nucleolar organizer region counts, compared to type B tumors from MMTV-Wnt-1 mice. These data provide evidence that ectopic neuropeptide production can modulate the development of tumors in vivo.

Adenocarcinoma↗
PubMed1994

A novel protein accumulated during maturation of the pods of the plant Impatiens balsamina.

A high molecular weight protein has been isolated as a major polypeptide comprising 85% of the total extractable proteins in the fruit pericarp of the plant Impatiens balsamina. The protein has been purified to homogeneity following fractionation of the crude cell supernatant with ammonium sulphate, chromatography on Sepharose 4B and Sephacryl-S-300. This protein appeared to be a homo-tetramer consisting of subunits, Mr 75 K. Amino acid analysis showed the presence of more acidic amino acids, with an isoelectric point 5.8. The interaction of this protein with filamentous actin, both from rabbit muscle and Mung bean embryo was monitored by transmission electron microscopy, light scattering analysis, viscometry and sedimentation assay. This protein inhibited appreciably the polymerization of G-actin to F-actin.

Actins↗
PubMed1994

Myo-inositol trisphosphate-mediated calcium release from internal stores of Entamoeba histolytica.

Calcium mobilisation from internal stores of the parasitic protozoan Entamoeba histolytica was studied by fluorescence measurements of the calcium indicator quin 2 and 45Ca2+ incorporation studies in saponin-permeabilised amoebae. Prior energy-dependent calcium sequestration was found to be necessary for subsequent release of calcium by inositol 1,4,5-trisphosphate (Ins(1,4,5)P3). Both Ins(1,4,5)P3 and inositol 2,4,5-trisphosphate (Ins(2,4,5)P3) could release calcium equally well from permeabilised E. histolytica with similar EC50 (concentration which produced half maximal release) values for calcium release. Ins(1,4,5)P3-mediated calcium release occurred from a vesicular store, was sensitive to prior treatment by heparin and was attenuated by prior addition of a lower concentration of Ins(1,4,5)P3. cAMP failed to influence inositol trisphosphate induced calcium release, indicating the absence of control mechanisms through cAMP-dependent phosphorylation. GTP neither induced calcium release nor could potentiate inositol trisphosphate mediated calcium mobilisation. A saturating concentration of Ins(1,4,5)P3 could release 50% of radiolabelled calcium sequestered by energy-dependent mechanisms in E. histolytica. The energy-dependent calcium sequestration was inhibited by vanadate and the calcium antagonist Diltiazem but not by dicyclohexylcarbodiimide (DCCD), suggesting the involvement of an endoplasmic reticulum-like structure in calcium storage. Binding studies showed specific association of [3H]Ins(1,4,5)P3 to crude membrane fractions of E. histolytica, which was significantly inhibited by heparin in a dose-dependent manner. IC50 (concentration which produced half-maximal inhibition) values for displacement of radiolabelled Ins(1,4,5)P3 binding by unlabelled Ins(1,4,5)P3 and Ins(2,4,5)P3 were estimated to be 0.99 microM for both isomers. Our results suggested that Ins(1,4,5)P3-mediated calcium release from internal stores of E. histolytica most probably occurred in an inositol trisphosphate receptor-dependent manner.

Animals↗
PubMed1994

Role of central catecholamines in the modulation of corticotrophin-releasing factor mRNA during adjuvant-induced arthritis in the rat.

The development of adjuvant-induced arthritis in the rat is associated with an activation of the hypothalamo-pituitary-adrenal axis. In the Piebald-Viral-Glaxo strain of rat there is however a paradoxical decrease in corticotrophin-releasing factor (CRF) mRNA in the hypothalamic paraventricular nucleus (PVN) and a decrease in CRF-41 peptide release into the hypophysial portal blood with increasing severity of disease. In the present study we have investigated the role of endogenous catecholamines within the PVN as possible inhibitory factors acting on CRF neurons during adjuvant-induced arthritis. Noradrenaline (NA) concentrations were approximately doubled in the PVN of arthritic animals. Depletion of endogenous catecholamines following direct 6-OHDA lesions of the PVN resulted in a significant depletion in PVN NA. The increase in NA observed in arthritic animals appears to have a protective role since depletion of NA increased the severity of the disease. Neither the increase in circulating levels of corticosterone nor the decrease in CRF mRNA in the PVN were prevented following NA depletion. Our results suggest that modification of central neurotransmitter systems are able to influence the severity of adjuvant-induced arthritis.

Animals↗
PubMed1994

Post lumbar puncture discitis and vertebral collapse.

Discitis and vertebral collapse are rare but serious complications of lumbar puncture. Clinical profile, management and course of post lumbar puncture discitis in five patients is presented. Such a complication should be kept in mind whenever any invasive procedure is carried out on the spine.

Adult↗
PubMed1994

Expression of chorionic gonadotrophin in human pituitary adenomas.

In addition to the classical anterior pituitary hormones, many human pituitary adenomas express hormone genes ectopically. Expression of glycoprotein hormone alpha-subunit and, less commonly, free luteinizing hormone beta (LH-beta) or follicle-stimulating hormone beta is characteristic of endocrinologically inactive adenomas, a subgroup thought to be derived predominantly from the gonadotroph line. Thyrotrophin beta expression in these tumours is unusual, and specific chorionic gonadotrophin beta (CG-beta) expression, identified using oligonucleotide probes that reliably distinguish LH-beta and CG-beta in situ, is not well described. Using in situ hybridization histochemistry with a CG-beta transcript-specific oligonucleotide probe and a non-specific LH/CG-beta oligonucleotide and riboprobe, we have demonstrated specific CG-beta expression in two of 35 random pituitary adenomas; LH-beta expression occurred in a further eight adenomas. Unlike prolactin, growth hormone and proopiomelanocortin, which are transcribed in the vast majority of cells in their respective hormone-positive tumour subtypes, the pattern of LH/CG-beta was typically a scattering of single or small clusters of hormone-positive cells in a predominantly LH/CG-beta-negative tumour. Finally, although bona fide CG-beta expression in human pituitary adenomas does occur, it is only at an incidence similar to that described for carcinomas of other tissues.

Adenoma↗
PubMed1994

A mechanistic approach into a diabetic serum factor-mediated release of beta-glucuronidase in normal neutrophils.

The possible mechanism of diabetic serum factor (DSF)-mediated lysosomal degranulation has been investigated. It was observed that pertussis toxin, sodium fluoride and vanadate could significantly inhibit DSF-mediated beta-glucuronidase release, whereas atropine exhibited only a partial blockage against DSF. Since DSF can generate toxic free radicals, various free radical quenchers were tested in order to evaluate their contributions. Superoxide dismutase was found to be the most effective in inhibiting lysosomal release as compared to catalase and peroxidase. The mixtures of all the enzymes failed to exhibit any additive effect. Interaction of DSF with heparin, insulin and Con A revealed that heparin can completely block DSF-mediated lysosomal release. The implications of the observations are discussed.

Adult↗
PubMed1994

Plausible involvement of extralysosomal proteinase in derangement of leucocytic Ca2+/Mg2+ ATPase in diabetes.

Translocation of calcium activated neutral proteinase from cytosol to plasma membrane, concurrently with decrease in the activity of membrane bound Ca2+/Mg2+ ATPase has been detected in diabetic polymorphonuclear leucocytes. Plausible involvement of the extralysosomal proteinase in the derangement of the Ca2+/Mg2+ ATPase is indicated by non restoration of the enzyme activity on treatment with activators such as trypsin or calmodulin and enhanced membrane translocation of the proteinase observed with concomitant decrease in the activity of Ca2+/Mg2+ ATPase in normal neutrophils on insult with diabetic serum factor.

Adult↗