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Biomedical subjects

A K Sharma

Publications and source records attributed to A K Sharma.

At least 181 records · Page 10Linked to original sources
PubMed1997

Analysis of quality assurance programmes for HIV screening in blood transfusion centres in Delhi.

The safety of blood transfusion has attained tremendous importance because of the problems posed by acquired immunodeficiency syndrome (AIDS) and other transfusion-transmissible diseases. While performing screening tests for human immunodeficiency virus (HIV) antibodies in donated blood is indispensable, it is also essential to introduce an effective quality assurance programme covering inspection of specimens, review of record-keeping, maintenance of equipment, and verification of results. We carried out an analysis of such quality assurance programmes during routine annual inspection of 11 blood transfusion centres in Delhi, India. The following parameters were studied: standardization of sample collection and handling; adherence to the recommended technical procedure; use of standard operating procedure; proper use of test reagents; laboratory record-keeping; proper handling of HIV-positive blood units; recording and communication of results; observation of safety guidelines; equipment quality control; and training of staff. A pretested closed-type questionnaire with a weighted scoring system was used for evaluation. Performance for each parameter was graded as follows: 76-100%, excellent; 51-75%, good; 26-50%, fair; and < 25%, poor. Centres were categorized according to the total score obtained for all parameters. Overall performance > 50% was considered satisfactory. Of the 11 centres, none was excellent overall, five were considered satisfactory, and six were unsatisfactory.

Blood Transfusion↗
PubMed1997

Interaction of muscle relaxant effect of gallamine with ethanol: in vivo mammalian model.

Ethanol produces alterations in muscular contraction and neuromuscular function both in vitro and in vivo in mammalian and amphibian tissues in dose dependent manner. It is not very well known whether gallamine, a commonly used muscle relaxant produces any interaction with ethanol. Hence in the present study, interactions of ethanol with gallamine are undertaken using rabbit head drop method. The latency time to produce head drop by gallamine in the absence and presence of ethanol (dose which produce ataxia) was insignificantly different (P > 0.05). It may be due to fact that ataxic dose may not be affecting neuromuscular transmission a significant manner. It, therefore, does not warrant to adjust the dose of gallamine in alcoholic persons.

Animals↗
PubMed1996

Effect of bitter melon (Momordica charantia) fruit juice on the hepatic cytochrome P450-dependent monooxygenases and glutathione S-transferases in streptozotocin-induced diabetic rats.

Bitter melon (Momordica charantia), commonly known as karela, has been reported to have hypoglycemic, antiviral, antidiabetic, and antitumor activities. In the present study, we have investigated the effects of oral feeding of karela fruit juice on the hepatic cytochrome P450 (CYP) and glutathione S-transferase (GST) drug-metabolizing enzymes in the streptozotocin (STZ)-induced diabetic rat. Hepatic CYP contents, ethoxycoumarin-O-deethylase (ECOD), ethoxyresorufin-O-deethylase (EROD), aniline hydroxylase (AH), and aminopyrene N-demethylase (APD) activities were measured in control, diabetic, and karela juice fed animals. Diabetic rats exhibited a 50-100% increase in AH and EROD activities that was reversed by karela juice feeding. In addition, a decrease (17-20%) in the activities of APD and ECOD was observed in diabetic rat liver. Feeding of karela juice to the diabetic animals brought the level of APD close to that of control animals, while ECOD was further reduced to 60% of the control value. The cytosolic glutathione concentration was decreased in diabetic rats, and karela juice feeding normalized the effect. However, an increase (of 20-30%) in the GST activity was observed in both diabetic and karela juice fed rats. Western immunoblot analysis of CYP and GST isozymes exhibited a differential response during diabetes. The expression of CYP1A1, 2B1, 2E1, 3A4, and 4A2 in diabetes, while a decrease in GST mu was observed. Our results suggest that the changes in hepatic phase I and phase II drug-metabolizing enzyme activities in the STZ-induced diabetic animals may be associated with the altered expression of different CYP and GST isozymes. In addition, we have also observed that karela does not always reverse the effects on drug-metabolizing enzymes in STZ-induced diabetes.

Animals↗
PubMed1996

Purification, crystallization and preliminary crystallographic analysis of mare lactoferrin.

Lactoferrin is an iron-binding glycoprotein with a molecular weight of 80 kDa. The protein has two iron binding sites. It has two structural lobes, each housing one Fe(3+) and the synergistic CO(3)(2-) ion. The protein was isolated from the colostrum/milk of mares maintained at National Research Centre on Equines, Hisar, India. The purified samples of the protein were crystallized using a microdialysis method. The protein was dialysed against low ionic strength buffer solution. Several crystal forms were obtained, out of which three were characterized which have cell dimensions as follows. Form I a = 79.8, b = 103.5, c = 112.0 A, space group P2(1)2(1)2(1), with one protein molecule per asymmetric unit and a solvent content of 57%. Form II a = 84.9, b = 99.7, c = 103.5 A, space group P2(1)2(1)2(1) with one molecule per asymmetric unit and a solvent content of 55%. Form III a = 151.0, b = 151.0, c = 240.6 A, space group P4(1)2(1)2 with three molecules in the asymmetric unit and a solvent content of 57%. The intensity data up to 3.8 A resolution for form I, 2.9 A resolution data for form II and 6 A resolution data for form III have been collected. Further calculations are in progress.

Journal Article↗
PubMed1996

Identification of three physically and functionally distinct binding sites for C3b in human complement factor H by deletion mutagenesis.

Human complement factor H controls spontaneous activation of complement in plasma and appears to play a role in distinguishing host cells from activators of the alternative pathway of complement. In both mice and humans, the protein is composed of 20 homologous short consensus repeat (SCR) domains. The size of the protein suggests that portions of the structure outside the known C3b binding site (SCR 1-4) possess a significant biological role. We have expressed the full-length cDNA of factor H in the baculovirus system and have shown the recombinant protein to be fully active. Mutants of this full-length protein have now been prepared, purified, and examined for cofactor activity and binding to C3b and heparin. The results demonstrate (i) that factor H has at least three sites that bind C3b, (ii) that one of these sites is located in SCR domains 1-4, as has been shown by others, (iii) that a second site exists in the domain 6-10 region, (iv) that a third site resides in the SCR 16-20 region, and (v) that two heparin binding sites exist in factor H, one near SCR 13 and another in the SCR 6-10 region. Functional assays demonstrated that only the first C3b site located in SCR 1-4 expresses factor I cofactor activity. Mutant proteins lacking any one of the three C3b binding sites exhibited 6- to 8-fold reductions in affinity for C3b on sheep erythrocytes, indicating that all three sites contribute to the control of complement activation on erythrocytes. The identification of multiple functionally distinct sites on factor H clarifies many of the heretofore unexplainable behaviors of this protein, including the heterogeneous binding of factor H to surface-bound C3b, the effects of trypsin cleavage, and the differential control of complement activation on activators and nonactivators of the alternative pathway of complement.

Animals↗
PubMed1996

Leukemia inhibitory factor upregulates cytokine expression by a murine stromal cell line enabling the maintenance of highly enriched competitive repopulating stem cells.

Attempts to maintain or expand primitive hematopoietic stem cells in vitro without the concomitant loss of their differentiative and proliferative potential in vivo have largely been unsuccessful. To investigate this problem, we compared the ability of three cloned bone marrow (BM) stromal cell lines to support the growth of primitive Thy-1lo Sca-1+H-2Khi cells isolated by fluorescence-activated cell sorting from the BM of Ly-5.2 mice treated 1 day previously with 5-fluo- rouracil. Sorted cells were highly enriched in cobblestone area-forming cells (CAFC), but their frequency was dependent on the stromal cell lines used in this assay (1 per 45 cells on SyS-1; 1 per 97 cells on PA6). In the presence of recombinant leukemia inhibitory factor (LIF), CAFC cloning efficiency was increased to 1 per 8 cells on SyS-1 and 1 per 11 cells on PA6, thus showing the high clonogenicity of this primitive stem cell population. More primitive stem cells with competitive repopulating potential were measured by injecting the sorted cells into lethally irradiated Ly-5.1 mice together with 10(5) radioprotective Ly-5.1 BM cells whose long-term repopulating ability has been "compromised" by two previous cycles of marrow transplantation and regeneration. Donor-derived lymphocytes and granulocytes were detected in 66% of animals injected with 50 sorted cells. To quantitate the maintenance of competitive repopulating units (CRU) by stromal cells, sorted cells were transplanted at limiting dilution before and after being cultured for 2 weeks on adherent layers of SyS-1, PA6, or S17 cells. CRU represented 1 per 55 freshly sorted cells. CRU could be recovered from cocultures supported by all three stromal cell lines, but their numbers were approximately-sevenfold less than on day 0. In contrast, the addition of LIF to stromal cultures improved CRU survival by 2.5-fold on S17 and PA6 cells (approximately two-fold to threefold decline), and enabled their maintenance on SyS-1. LIF appeared to act indirectly, because alone it did not support the proliferation of Thy-1lo Sca-1+H-2Khi cells in stroma-free cultures. Polymerase chain reaction (RT-PCR) analysis revealed that Interleukin-1beta (IL-1 beta) IL-2, IL-6, granulocyte-colony stimulating factor, granulocyte macrophage-colony stimulating factor, transforming growth factors, LIF, and Steel Factor (SLF) mRNAs were upregulated in SyS-1 within 1 to 6 hours of LIF-stimulation. To determine if increased expression of SLF by LIF-stimulated SyS-1 cells could account for their capacity to support stem cells, sorted calls were cocultured on simian CV-E cells that were transfected with an expression vector encoding membrane-bound SLF, or supplemented with soluble SLF. In both cases, SLF synergized with IL-6 produced endogenously by CV-E cells enabling CAFC growth equivalent to that on LIF-stimulated SyS-1. CAFC development on LIF-stimulated SyS-1 could also be completely abrogated by an anti-SLF antibody. These data provide evidence for a role of LIF in the support of long-term repopulating stem cells by indirectly promoting cytokine expression by BM stroma. Furthermore, we have used quantitative assays to show a maintenance of CRU numbers, with retention of in vivo function following ex vivo culture.

Animals↗
PubMed1996

Solution conformation of tuftsin.

Conformation of chemically synthesized tetrapeptide tuftsin, an important immunomodulator, with the sequence Thr-Lys-Pro-Arg-OH has been studied in aqueous solution as well as in a number of organic solvents viz. trifluoroethanol (TFE), methanol and dioxane by circular dichroism (CD) spectroscopy which reveals preferential occurrence of mixture of random coil and beta-turns, that has already been predicted as bioactive conformation of this peptide.

Circular Dichroism↗
PubMed1996

Cell-mediated immune responses of lambs to experimental infection with bovine respiratory syncytial virus.

Primary infection of lambs with bovine respiratory syncytial virus (RSV) was characterised by the presence of virus-specific cytotoxic cells in the peripheral blood as early as 5 days post-infection. These effector cells lysed virus-infected autologous targets in a self-restricted manner. Depletion techniques revealed that cytotoxic activity was largely due to OvCD8+ cells. Neutrophils obtained from experimentally infected lambs 5 to 10 days post-inoculation exhibited significant cytotoxic activity in the presence of bovine RSV-specific antiserum. During the same period there was a significant lymphoproliferative response to live or inactivated bovine RSV. Lymphoproliferative and cytotoxic activity coincided with the clearance of the virus from nasal secretions.

Animals↗
PubMed1996

Antigens of bovine respiratory syncytial virus in peripheral blood lymphocytes of experimentally infected lambs.

Eight lambs were experimentally infected with bovine respiratory syncytial virus (RSV) and the distribution of viral antigen in lymphocyte subpopulations studied by flow cytometry. Experimental infection with bovine RSV was characterised by significant changes in lymphocyte subpopulations. Infection was followed by a significant (P <0.001) reduction in the number of cells expressing the OvCD5 epitope (T cells), due to a fall in the number of cells expressing the OvCD4 epitope (helper) and those expressing the OvWC1 epitope (gamma/delta) 3-7 days post-inoculation. There was a significant increase in the number of OvCD5+ cells expressing the OvCD8 epitope (cytotoxic/suppressor) later. Flow cytometric analysis with bovine RSV-specific monoclonal antibodies revealed that viral antigens were present in all lymphocyte subpopulations but the main targets were T cells in general and OvCD4+ cells in particular. Challenge of primed lambs with bovine RSV had similar effects over a shorter period, followed by significant rises in the number of OvCD45+ (B) cells and OvCD5+ (T cells). Viral antigens were also present in lymphocytes subsets following challenge.

Animals↗
PubMed1996

Immune responses of lambs to the fusion (F) glycoprotein of bovine respiratory syncytial virus expressed on insect cells infected with a recombinant baculovirus.

A group of lambs was immunized with the F protein of bovine respiratory syncytial virus expressed in a baculovirus (Bac-F) and their humoral and cellular immune responses to bovine RSV studied before and after challenge with infectious bovine RSV. Immunization with Bac-F resulted in significant humoral immune responses as measured by virus neutralization and cellular immune responses as measured by lympho-proliferation against inactivated bovine RSV and specific cytotoxicity against autologous targets. Challenge infection with bovine RSV was characterized by significant anamnestic responses in Bac-F immunized lambs and virus shedding in nasal secretions was significantly lower in Bac-F immunized lambs than in control lambs.

Animals↗
PubMed1996

Replication of bovine respiratory syncytial virus in ovine peripheral blood lymphocytes and monocytes in vitro.

Adherent and non-adherent mononuclear cells obtained from the peripheral blood of normal lambs supported the replication of bovine respiratory syncytial virus in vitro. Sequential treatment of monocytes with phorbol ester acetate (PMA) enhanced their ability to support viral replication. After exposure in vitro for 24 h, viral antigens were present in 47 +/- 4.5% of monocytes and 32 +/- 3% of lymphocytes. Treatment of monocytes with PMA resulted in the increase of the proportion of cells expressing viral antigen and in the titre of infectious virus.

Animals↗
PubMed1996

Clinical profile of stroke in relation to glycaemic status of patients.

Present study was undertaken in fifty consecutive patients of acute stroke to assess the role of glycemic status on clinical profile of stroke. Majority of patients (76%) were in age group of 41-70 years. The patients were classified into four groups: euglycemics (33), known diabetics (8), newly diagnosed diabetics (6) and stress hyperglycemics (3). Diabetics as well as stress hyperglycemics had higher prevalence of larger sized severe haemorrhagic stroke with poor outcome and there was positive correlation between them.

Acute Disease↗