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Biomedical subjects

M Srivastava

Publications and source records attributed to M Srivastava.

At least 73 records · Page 4Linked to original sources
PubMed1997

Alcohol problems in a general hospital--a prevalence study.

The prevalence of problem drinking among medical and surgical in-patients in a general hospital was studied using the CAGE questionnaire. Almost a quarter (23.3%) of the in-patients had associated drinking problems which were more among medical than surgical in-patients. In a large majority of these patients, the associated problem drinking was not recognised by the treating medical professionals. Routine administration of instruments like CAGE which are brief and easy to use would contribute to the early detection and management of alcohol problems in the general hospital setting.

Alcoholism↗
PubMed1996

Detection and localization of synexin (Annexin VII) in Xenopus adult and embryonic tissues using an antibody to the Xenopus N-terminal PGQM repeat domain.

Synexin (Annexin VII) is a widely distributed member of the annexin gene family which forms calcium channels and drives calcium-dependent membrane fusion. In Xenopus laevis, different synexins contain two to six tandem repeats of the tetra amino acid sequence PGQM in the unique N-terminal, with a distribution specific to adult tissues and embryonic stages. Immunogold studies using the PGQM-specific polyclonal antibody showed that synexin is localized in adult muscle to myosin-rich A-bands, Z-bands, and T-tubules, and in other adult tissues to nuclei and mitochondria and other formed elements. In oocytes, synexin was also found associated with yolk granules. The PGQM tandem repeats could represent interaction sites for other proteins, and we therefore synthesized a synthetic peptide containing the maximum six tandem repeats [NH2-(PGQM)6-Y-COOH] to test this hypothesis. We found that the peptide alone could specifically bind and crosslink to different proteins in a tissue-specific manner. In liver, it bound to a single 35-kDa protein. In muscle, it bound to four proteins (35, 45, 48, and 116 kDa). Therefore, we conclude that the PGQM domain is accessible to specific antibodies and that the PGQM repeat is sufficiently ordered to unambiguously identify specific binding proteins in different Xenopus tissues.

Amino Acid Sequence↗
PubMed1996

Membrane fusion protein synexin (annexin VII) as a Ca2+/GTP sensor in exocytotic secretion.

Exocytotic membrane fusion and secretion are promoted by the concerted action of GTP and Ca2+, although the precise site(s) of action in the process are not presently known. However, the calcium-dependent membrane fusion reaction driven by synexin (annexin VII) is an in vitro model for this process, which we have now found to be further activated by GTP. The mechanism of fusion activation depends on the unique ability of synexin to bind and hydrolyze GTP in a calcium-dependent manner, both in vitro and in vivo in streptolysin O-permeabilized chromaffin cells. The required [Ca2+] for GTP binding by synexin is in the range of 50-200 microM, which is known to occur at exocytotic sites in chromaffin cells, neurons, and other cell types. Previous immunolocalization studies place synexin at exocytotic sites in chromaffin cells, and we conclude that synexin is an atypical G protein that may be responsible for both detecting and mediating the Ca2+/GTP signal for exocytotic membrane fusion.

Animals↗
PubMed1996

Novel isoforms of synexin in Xenopus laevis: multiple tandem PGQM repeats distinguish mRNAs in specific adult tissues and embryonic stages.

Synexin (annexin VII) is a calcium-dependent, phospholipid-binding and membrane fusion protein in the annexin gene family, which forms calcium channels and may play a role in exocytotic secretion. We report here the cloning and characterization of five novel isoforms of cDNAs encoding Xenopus synexin from brain, oocyte and stage 24 cDNA libraries. The most prevalent Xenopus synexin has 1976 bp of cDNA sequence, which contains a 1539 bp open reading frame of 512 amino acids encoding a 54 kDa protein. This Xenopus protein is 6 kDa larger than the previously reported human and mouse synexins with which it shares approx. 73% identity in the C-terminal region and approx. 44% identity in the N-terminal region. Further studies with PCR revealed the molecular basis of the substantial divergence in the Xenopus synexin's N-terminal domain. The domain equivalent to the mammalian tissue-specific cassette exon occurs at a different position and is variable in size and sequence. The most interesting observation relates to the occurrence of different forms of synexin due to the varying numbers of tandem PGQM repeats that are expressed differently in different adult tissues and embryonic stages. For these reasons we have labelled this set of unique isoforms annexin VIIb, referring to mammalian forms, which lack the PGQM tandem repeats, as annexin VIIa. In spite of these differences from annexin VIIa, the form of recombinant annexin VIIb with three PGQM repeats was found to be catalytically active. We interpret these results to indicate that the actual calcium and phospholipid binding sites are conserved in Xenopus, and that the variations observed between members of the synexin gene family in the regulatory domain clearly point towards the tissue- and stage-specific roles of individual members, possibly involving the exocytotic process.

Amino Acid Sequence↗
PubMed1996

Transient renal impairment in acute intracerebral haemorrhage.

Transient impairment of renal function was found in 30 of 78 patients with acute intracerebral haemorrhage (ICH). Patients with a history of renal disease, dehydration, nephrotoxic drugs or septicaemia were excluded. In the 1st week, the mean serum creatinine level was 3.4 (range 1.7-7.7) mg/dl, which returned to normal in 2-4 weeks. Employing multivariate stepdown logistic regression analysis, Glasgow Coma Scale score and pulse pressure were found to be significantly related to renal impairment manifesting with a raised serum creatinine level, whereas pupillary asymmetry was of borderline significance. An acute rise in intracranial pressure following ICH may result in sympathetic overactivity, which may account for the renal impairment observed in our patients.

Acute Disease↗
PubMed1996

A study of prognostic predictors of supratentorial haematomas.

The prognosis of supratentorial haematomas is based on clinical signs and radiological features. The role of evoked potentials has not been evaluated systematically. In a prospective study of supratentorial haemorrhage a number of clinical (17), radiological (3) and evoked potential (2) parameters were evaluated employing univariate logistic regression analysis in 69 patients and multivariate logistic regression stepdown analysis in 51 patients. The outcome was graded on the basis of the Barthel index (BI) score at 3 months as good (BI > or = 12) or poor (death or BI < 12) recovery. Employing univariate analysis the significant prognostic variables were Glasgow Coma Scale, Canadian Neurological Scale, tendon reflex, associated medical complications, urinary incontinence, ventricular extension of the haematoma and motor evoked potentials. Using multivariate logistic regression analysis the best set of parameters in relation to outcome included Glasgow Coma Scale (P < 0.05), Canadian Neurological Scale (P < 0.05), tendon reflex (P < 0.1), ventricular extent (P < 0.01) and motor evoked potentials (P < 0.05). From this study it is concluded that, in addition to clinical and radiological parameters, motor evoked potentials also have an important role in predicting outcome.

Adolescent↗
PubMed1996

Prognosis of tuberculous meningitis: a multivariate analysis.

Twenty-six clinical, laboratory and CT scan features in 49 patients with tuberculous meningitis (TBM) were analysed to identify the parameters of prognostic significance. Employing univariate analysis, seven variables were found to correlate with three month outcome; these variables included the stage of TBM on admission, focal weakness, Glasgow coma scale (GCS), incontinence, infarction, hydrocephalus and shunt surgery. Analysing all 26 variables, a conditional logistic regression model was derived. In this model stage of TBM, age, focal weakness, cranial nerve palsy and hydrocephalus were found to be contributing to the three month outcome of TBM patients as assessed by the Barthel index.

Adolescent↗
PubMed1996

Xenopus cytochrome b561: molecular confirmation of a general five transmembrane structure and developmental regulation at the gastrula stage.

Cytochrome b561 transports electrons by a novel transmembrane vectoral pathway. Using the human cytochrome b561 cDNA probe, the Xenopus cytochrome b561 cDNA has been isolated and sequenced. A specific ATG was unambiguously identified because the Xenopus sequence has a stop codon 7 amino acids upstream from the initiation site ATG. The 741-bp open reading frame encodes a 247-amino-acid protein. The position of the initiating ATG site in Xenopus cytochrome b561 is consistent with the first ATG site in human and mouse proteins, and with the second of two ATG sites in the bovine protein. This result indicates that a five transmembrane domain model best represents the conformation of cytochrome b561 in membranes. Cytochrome b561 plays a fundamental role in the physiology of all neuroendocrine tissues, and the results presented here show that Xenopus cytochrome b561 mRNA is specific to neuroendocrine tissues and is developmentally regulated at the gastrula stage.

Amino Acid Sequence↗
PubMed1995

Genomic structure and expression of the human gene encoding cytochrome b561, an integral protein of the chromaffin granule membrane.

Cytochrome b561 is an electron transfer protein unique to neuroendocrine secretory vesicles. The Southern blot hybridization shows that it is a single copy gene highly conserved throughout phylogeny. The transcription unit spans approximately 11 kilobases, and heterologous transcription sites are located 404 bases 5' to the translation initiation codon. The sequence of the 5'-flanking region is GC-rich and lacks a typical TATA box at the usual position. However, it has a CAAT sequence at -132 and potential recognition sequences for several transcription factors including SP1, GR-PR-MMTV, AP4, gERE, JCV repeat, AP2, and NF-kappa B. Each of the five transmembrane segments are encoded by five consecutive exons. This corroborates the five-transmembrane model proposed for human, mouse, and Xenopus rather than six proposed for bovine. The cytochrome was found to be highly expressed in colon cancer cell lines, T cell lymphomas, and K-562 cell lines. However, in B-cell lymphomas such as Burkitt's and Daudi, the cytochrome b561 expression was completely shut down. The results in this report are the first to demonstrate the structural organization and regulatory sequences of the cytochrome b561 gene encoding an integral membrane protein of neuroendocrine storage vesicles of neurotransmitters and peptide hormones. Unexpected results on cytochrome b561 expression in cells of lymphocytic origin and its complex regulation in tumor cells provide new insights into cytochrome b561 gene regulation.

Animals↗
PubMed1995

Immunodominant RNA recognition motifs of human nucleolin/C23.

Nucleolin/C23 is a nucleolar phosphoprotein implicated in the synthesis, processing and transport of ribosomal RNA and gene transcription. Auto-antibodies to human nucleolin/C23 have been reported in patients with systemic lupus erythematosus and other systemic autoimmune disorders. To identify immunodominant regions in nucleolin/C23, deletion fragments of nucleolin/C23 were fused in frame with the glutathione S-transferase gene. Seven monoclonal anti-nucleolin/C23 antibodies were used to determine the immunoreactivity of the bacterially expressed fusion proteins. Two sets of immunogenic regions at amino acids 314-389 and 387-461 were identified; each contained overlapping discontinuous epitopes and a centrally located RNA recognition motif. An auto-immune serum from a patient with systemic lupus erythematosus patient was found to contain antibodies against human nucleolin/C23 which recognized amino acids 387-461 of nucleolin/C23.

Amino Acid Sequence↗
PubMed1995

Cinnamon bark oil, a potent fungitoxicant against fungi causing respiratory tract mycoses.

Cinnamic aldehyde has been identified as the active fungitoxic constituent of cinnamon (Cinnamomum zeylanicum) bark oil. The fungitoxic properties of the vapours of the oil/active constituent against fungi involved in respiratory tract mycoses, i.e., Aspergillus niger, A. fumigatus, A. nidulans A. flavus, Candida albicans, C. tropicalis, C. pseudotropicalis, and Histoplasma capsulatum, were determined in vitro as minimum inhibitory concentration (MIC), minimum lethal concentration (MLC), inoculum density sustained, and exposure duration for fungicidal action at MIC and higher doses, as well as effect of incubation temperatures on fungitoxicity. It is concluded that these inhalable vapours appear to approach the ideal chemotherapy for respiratory tract mycoses.

Cinnamomum zeylanicum↗
PubMed1995

Pregnancy induced hypertension and antithrombin-III.

This study was undertaken to determine the coagulation profile of women with pregnancy induced hypertension and to evaluate the changes in the level of AT-III in pre-eclampsia and eclampsia and its correlation with severity of disease in order to evaluate if it can be used as a marker for severity of PIH. 119 women with PIH in the third trimester of pregnancy constituted the study group. Age and parity matched 25 normal pregnant and 25 non-pregnant women were taken as control group. No significant difference between the coagulation profile of non-pregnant and normal pregnant women was seen. There is evidence of consumption coagulopathy in PIH patients and AT-III activity shows a gradual and almost linear reduction in various groups ranging from normal pregnant women to eclampsia. Reduction in AT-III activity has positive correlation with PIH and it can be a useful marker for severity of PIH.

Antithrombin III↗
PubMed1994

Human cytochrome b561: a revised hypothesis for conformation in membranes which reconciles sequence and functional information.

Cytochrome b561 is a major transmembrane protein of catecholamine and neuropeptide secretory vesicles. In this report, we describe the cloning and properties of a full-length cDNA encoding human neuroendocrine cytochrome b561 from a human caudate cDNA library and a human peripheral blood genomic library. The human cDNA contains two major transcription start sites and only one translation start site that codes for an apocytochrome b561, which is 22 amino acid residues smaller than the previously deduced amino acid sequence from bovine cDNA. This smaller version of cytochrome b561 may contain only five transmembrane segments rather than the previously proposed six segments. The new model is in agreement with our previous results on transmembrane topology of the gene product. Northern-blot analysis shows an expanded tissue distribution of cytochrome mRNA expression where previous immunological assays were negative. These results support the hypothesis that cytochrome b561 is a marker for peptidergic and adrenergic tissues.

Amino Acid Sequence↗
PubMed1994

Analysis of the tumor suppressor gene p53 in xeroderma pigmentosum fibroblasts.

Genetic risk factor(s) for skin cancers have been described in patients with xeroderma pigmentosum (XP). The tumor suppressor gene, p53, is one of the most frequently mutated genes found in human tumors. To evaluate the role of XP-related genetic defects in the p53 gene, skin fibroblast cell lines derived from XP donors were analysed for mutations in exons 5-9 (the regions of gene highly susceptible for mutations) by single-strand conformation polymorphism (SSCP) and nucleotide sequencing. Of the five XP-derived fibroblasts (complementation group A) and two control fibroblast cell lines, only one XP cell line showed an aberrant SSCP banding pattern in the region of the p53 gene (comprising the 7th exon and neighbouring intronic sequences). Nucleotide sequencing of this region confirmed a mutation in the 7th intron adjacent to the 7th exon, which did not affect the RNA splice site. These results suggest that constitutional/germ-line mutations in the p53 gene may not play a role in the occurrence of skin carcinomas in XP patients.

Base Sequence↗
PubMed1994

Genomic organization and chromosomal localization of the mouse synexin gene.

We have isolated and characterized the gene encoding mouse synexin, which consists of 14 exons and spans approximately 30 kbp of genomic DNA. The protein's unique N-terminal domain is encoded by six exons, and the C-terminal tetrad repeat, the site of the membrane-fusion and ion-channel domain, is encoded by seven exons. The first exon encodes the 5'-untranslated region. Analysis of synexin-gene expression in different mouse tissues shows that mRNA with exon 6 is only present in brain, heart and skeletal muscle. mRNA lacking exon 6 is expressed in all tissues we have examined. The initiation site for transcription was determined by primer-extension analysis and S1 nuclease mapping. Sequence analysis of the 1.3 kb 5'-flanking region revealed that the promoter has a TATA box located at position -25 and a number of potential promoter and regulatory elements. A CCAAT motif was not observed but CCATT is located in an appropriate position for the CCAAT motif upstream from the transcription-initiation start site. In addition, the 5'-flanking region contains two sets of palindromic sequences. Finally, we have determined that the functional synexin gene (Anx7) is located on mouse chromosome 14 and that a pseudogene (Anx7-ps1) is located on chromosome 10.

3T3 Cells↗
PubMed1994

Divergent structure of the human synexin (annexin VII) gene and assignment to chromosome 10.

The human synexin (annexin VII) gene occurs as a single copy at chromosome 10q21.1-21.2 and substantially deviates in size and in the location of splice junctions from the other two well-characterized members of the annexin gene family, lipocortin I (annexin I) and calpactin I (annexin II). The synexin gene contains 14 exons, including an alternatively spliced cassette exon, and spans approximately 34 kb of DNA. Only five of the fourteen splice junctions are conserved compared to other annexins, and the differences are particularly pronounced in the exons that encode the C-terminal third and fourth conserved repeats in the gene product. Although parallels between exons and protein domains were not apparent, we did observe clustering of splice junctions corresponding to either the unique N-terminal domain or the conserved C-terminal tetrad repeat domain, which is common to all annexins. Furthermore, a complete analysis of the 5' flanking region of the annexin VII gene revealed an entirely different set of cis-acting and enhancer elements compared to other annexin genes. We conclude that the annexin VII gene may have arisen by a divergence from the evolutionary pathway taken by both annexins I and II.

Amino Acid Sequence↗