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Biomedical subjects

M S Patel

Publications and source records attributed to M S Patel.

At least 73 records · Page 4Linked to original sources
PubMed1995

Measles outbreak in western Sydney. Vaccine failure or failure to vaccinate?

OBJECTIVES: To determine the effectiveness of measles vaccine during a measles outbreak, and to assess whether age at vaccination was a risk factor for measles vaccine failure. DESIGN: A matched case-control study. SETTING: The five primary schools in western Sydney with the largest number of measles cases during the June to December 1993 outbreak. SUBJECTS: Seventy-nine children aged 5-9 years with an illness consistent with a clinical definition for measles. Two controls per case were selected from children in the same classroom. MAIN OUTCOME MEASURES: Estimated measles vaccine effectiveness by age of the child at vaccination and vaccination status: "unvaccinated"; "parental recall" (parents stated the child was vaccinated but no record could be found); and "record" (record including date of vaccination available). RESULTS: The estimated vaccine effectiveness was 94% (95% confidence interval [CI], 83%-98%) in the "record" group, and 81% (95% CI, 46%-93%) in the "parental recall" group. Vaccine effectiveness did not differ significantly with age at vaccination (under 12 months of age 96% [64%-99%]; 12-14 months 95% [81%-99%]; and 15 months and over 93% [80%-98%]). CONCLUSION: Vaccination records should be used to calculate a vaccine's effectiveness as parental recall may not be sufficiently accurate. The high vaccine effectiveness in the "record" group (94%) makes it unlikely that low vaccine effectiveness was the cause of the outbreak. More effort is needed to increase vaccine coverage to at least 95% in all population subgroups.

Age Factors↗
PubMed1995

Identification of the tryptophan residue in the thiamin pyrophosphate binding site of mammalian pyruvate dehydrogenase.

The pyruvate dehydrogenase (E1) component of the mammalian pyruvate dehydrogenase complex catalyzes the oxidative decarboxylation of pyruvate with the formation of an acetyl residue and reducing equivalents, which are transferred sequentially to the dihydrolipoyl acetyltransferase and dihydrolipoamide dehydrogenase components. To examine the role of tryptophanyl residue(s) in the active site of E1, the enzyme was modified with the tryptophan-specific reagent N-bromosuccinimide. Modification of 2 tryptophan residues/mol of bovine E1 (out of 12 in a tetramer alpha 2 beta 2) resulted in complete inactivation of the enzyme. The inactivation was prevented by preincubation with thiamin pyrophosphate (TPP), indicating that the modified tryptophan residue(s) is part of the active site of this enzyme. Fluorescence studies showed that thiamin pyrophosphate interacts with tryptophan residue(s) of E1. The magnetic circular dichroism (MCD) spectral intensity at approximately 292 nm was decreased by approximately 15% for E1 + TPP relative to the intensity for E1 alone. Because this MCD band is uniquely sensitive to and quantitative for tryptophan, the simplest interpretation is that 1 out of 6 tryptophan residues present in E1 (alpha beta dimer) interacts with TPP. The natural circular dichroism (CD) spectrum of E1 is dramatically altered upon binding TPP, with concomitant induction of optical activity at approximately 263 nm for the nonchiral TPP macrocycle. From CD studies, it is also inferred that loss of activity following N-bromosuccinimide treatment occurred without significant changes in the overall secondary structure of the protein. A single peptide was isolated by differential peptide mapping in the presence and absence of thiamin pyrophosphate following modification with N-bromosuccinimide. This peptide generated from human E1 was found to correspond to amino acid residues 116-143 in the deduced sequence of human E1 beta, suggesting that the tryptophan residue 135 in the beta subunit of human E1 functions in the active site of E1. The amino acid sequence surrounding this tryptophan residue are conserved in E1 beta from several species, suggesting that this region may constitute a structurally and/or functionally essential part of the enzyme.

Amino Acid Sequence↗
PubMed1995

Epidemic gonococcal conjunctivitis in central Australia.

OBJECTIVES: To describe an epidemic of gonococcal conjunctivitis in central Australian Aboriginal children, the responsible phenotypes of Neisseria gonorrhoeae, factors facilitating spread and treatment efficacy. DESIGN: Prospective study of patients with laboratory confirmed or clinical gonococcal conjunctivitis diagnosed from January to July 1991. SETTING: The Alice Springs and Barkly Tablelands Health Districts of the Northern Territory, the Anangu Pitjantjatjara Lands of South Australia and the Ngaanyatjarra Homelands of Western Australia. METHODS: Cases were identified from surveillance data and laboratory notifications, and by active case finding. A community survey explored risk factors. MAIN OUTCOME MEASURES: Age-specific attack rates, auxotype/serovar characterisation of isolates, and clinical response to single dose treatment. RESULTS: We identified 432 cases. The highest attack rate was in the 0-4 year age group (86 per 1000), and the risk of conjunctivitis decreased with age. The odds ratio of secondary infection in household compared with community contacts was 14.5 (P < 0.002; 95% CI, 1.8-120.0). Disease was less common in children with clean faces and hands. The outbreak occurred after unseasonable rains and large community gatherings. Isolates were predominantly IA serovars, less common among central Australian serovars. CONCLUSIONS: The trigger for nonsexually transmitted gonococcal conjunctivitis epidemics remains obscure. Age is a significant risk factor and social and ecological factors may also contribute. Active case finding within affected households and treatment with a suitable penicillin is effective in stopping transmission.

Acute Disease↗
PubMed1995

Characterization of the promoter regulatory region of the human pyruvate dehydrogenase beta gene.

A genomic clone (19 kb) harboring the intron-exon sequences and the promoter-regulatory region of the E1 beta gene of human pyruvate dehydrogenase complex was isolated by screening a placental genomic library. The nucleotide sequence of the promoter region (1245 bp) showed 18 differences (including mismatches, insertions, and deletions) as compared to the published sequence [Koike et al. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 5594-5597]. The E1 beta promoter lacked a TATA box homology but contained initiator sequences (two) and Sp1 sites (three) which are frequently found in TATA-less promoters. The DNase I footprinting pattern of the promoter region with crude rat liver nuclear extracts showed at least seven regions of protein binding and nuclease protection (P1-P7). The DNase I protected regions contained consensus nucleotide sequences recognized by GATA-1, Sp1, IgNF-A, Lva, bicoid Q9, NF-kB, HNF-5, H4TF-1, WAP5, and ADH transription factors. Transient expression of chloramphenicol acetyltransferase (CAT) suggested the possible presence of negative elements located within the sequence from -2316 to -930, whereas deletion constructs containing -929 to +32 and -98 to +32 DNA sequences showed approximately 7- and 20-fold increases in CAT activity over the basal CAT activity. Additional studies indicated the presence of an orientation-dependent cis element (or elements) within the region from -282 to -397 that acts as an enhancer or a repressor upon a heterologous thymidine kinase promoter.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1995

Overexpression and characterization of human tetrameric pyruvate dehydrogenase and its individual subunits.

Pyruvate dehydrogenase (E1), an alpha 2 beta 2 tetramer, is the first component of the pyruvate dehydrogenase complex which catalyzes a two-step oxidative decarboxylation of pyruvic acid. To overexpress human E1 and its subunits individually, cDNAs for the mature forms of human E1 alpha and E1 beta were subcloned either individually or together into a plasmid pQE-9 and expressed in Escherichia coli M15. A polyhistidine extension was added at the NH2-termini of the recombinant E1 alpha and E1 beta for the rapid purification of the proteins by Ni-nitrilotriacetic-agarose chromatography. The polyhistidine extension on either E1 alpha or E1 beta subunit did not affect the activity of the recombinant tetrameric E1. Highly purified recombinant human E1 catalyzed the partial reactions of the oxidative and nonoxidative conversion of pyruvic acid with the same efficiency as E1 purified from bovine kidney. Recombinant human E1 interacted with thiamin pyrophosphate by forming a charge transfer complex band at 330 nm that changed during the catalytic cycle. Recombinant human E1 was phosphorylated by E1-kinase (with concomitant inactivation) by incorporating nearly three phosphoryl groups per mole of E1. When expressed individually, E1 alpha and E1 beta subunits lacked any catalytic activity in the oxidative or nonoxidative reactions. Spectral studies demonstrated that there was no thiamin pyrophosphate binding to either recombinant E1 alpha or E1 beta subunit. The E1 alpha subunit retained the ability to be phosphorylated; however, the incorporation of phosphoryl groups into recombinant E1 alpha alone was only about 12% of that observed with the tetrameric E1. These findings show that both subunits are required for formation of the active center and catalysis.

Base Sequence↗
PubMed1995

Solvation of platinum anti-cancer drugs in methanol-water mixtures.

Solubilities and transfer chemical potentials of carboplatin, cisplatin, iproplatin, and several related platinum complexes have been determined in methanol-water mixtures. The range of solvation behaviour is discussed in relation to possible oral administration of complexes of this type.

Antineoplastic Agents↗
PubMed1995

Epstein-Barr virus replication studies and their application to vector design.

Vectors containing elements of the Epstein-Barr virus genome are used primarily to maintain cloned DNA inserts as plasmids in mammalian cells. However, Epstein-Bar-virus-based vectors have also been valuable tools in the hands of those studying the life cycle of Epstein-Barr virus. In this article, we discuss those characteristics of Epstein-Barr virus and its life cycle that have been used in vector construction and describe methods that are particularly applicable to the use of Epstein-Barr-virus-based vectors.

DNA Replication↗
PubMed1995

Dihydrolipoamide dehydrogenase: activity assays.

We have described the most commonly used assay procedures determination of the DHLipDH activities from prokaryotic and eukaryotic cells. We have also described the procedures for the preparation of tissue extracts to determine the enzymatic activity. We have briefly alluded to the problems inherent in these assay procedures and suggested some precautions for using the assays to determine DHLipDH activity. We have also included a statement about the purification procedures and described some of the properties of this enzyme, which might help the reader in planning studies. We have, by no means, attempted to be comprehensive in this regard; therefore, the reader should consult the appropriate references (and references therein).

Animals↗
PubMed1995

Gene regulation and genetic defects in the pyruvate dehydrogenase complex.

The mammalian pyruvate dehydrogenase complex (PDC) is subject to both short-term (product inhibition and covalent modification) and long-term (increases in total activity and protein mass) regulation mediated by dietary and hormonal treatments. Recent advances in the isolation and characterization of the complementary DNAs as well as genes encoding several components of mammalian PDC have facilitated studies concerning long-term regulation of PDC. Analyses of the promoter-regulatory regions of the two human PDC genes show characteristics of both facultative and housekeeping gene promoters, indicating complex transcriptional regulation. Deficiency of PDC activity causes a wide range of neurological disabilities. A spectrum of genetic defects in PDC components has been reported; however, the most frequent defects are associated with the pyruvate dehydrogenase component. Heterogeneity in pyruvate dehydrogenase deficiency has been shown to occur at both protein and messenger RNA levels, and several mutations in pyruvate dehydrogenase have been identified. Dietary treatments such as ketogenic diets and vitamin supplements as well as dichloroacetate treatment have been utilized to treat PDC deficiency, but their efficacy requires further evaluation.

Gene Expression Regulation, Enzymologic↗
PubMed1995

Mammalian alpha-keto acid dehydrogenase complexes: gene regulation and genetic defects.

Recent application of the tools of molecular biology has provided insight with respect to the structure, regulation, and defects of the genes encoding the PDC and the BCKADC. cDNAs for the alpha-KGDC have only recently been cloned. Evidence for long-term regulation of the expression of the subunits of the PDC and the BCKADC has been obtained. Detailed analyses of the promoter-regulatory regions of the genes encoding the individual subunits of these complexes have provided leads as to molecular mechanisms involved. Evidence for coordinated regulation of expression of the subunits of the complexes has been obtained under some conditions but not others. Except for the PDC E1 alpha (X) promoter, the other promoters of the genes encoding PDC and BCKADC components are TATA-less with characteristics of housekeeping genes. Most cases of PDC deficiency, which produces lactic acidosis, are caused by defects in the coding region of the E1 alpha subunit. In contrast, gene defects that cause maple syrup urine disease are more heterogeneous, involving errors in any one of the subunits of the BCKADC. Alpha-KGDC deficiency has been reported but specific mutations have not been identified. Future work is expected to include detailed studies of the genes encoding the protein kinases and phosphatases that specifically regulate the PDC and the BCKADC by covalent modification.

Animals↗
PubMed1995

High mortality from renal disease and infection in Aboriginal central Australians with diabetes.

Few studies have examined the consequences of the high prevalence of diabetes in Aboriginal communities. We aimed to determine the rates and causes of mortality in all Aboriginal central Australians with diagnosed diabetes, identified by a previous study (n =374). Cohort members were followed from 1 January 1984, or the date of diagnosis (to 31 December 1986), to 31 December 1991 or death. Death certificates, medical notes and autopsy reports were examined for cause of death. There were 130 deaths in 2280.7 person-years of follow-up. Standardised mortality ratios for Aboriginal people with diabetes, compared to the Northern Territory Aboriginal population, were 209 (95 per cent confidence interval (CI) 158 to 273) for men and 169 (CI 129 to 218) for women. The difference in ratios for men and women was not statistically significant when adjusted for age (P = 0.2). The eight-year survival rates for men and women diagnosed between 1984 and 1986 were 55.8 per cent (CI 32.6 to 73.7) for men and 80.3 per cent (CI 64.8 to 89.5) for women. Renal disease was the direct cause of death in 22.3 per cent. Infection accounted for 20.8 per cent of deaths and ischaemic heart disease for 13.8 per cent. Forty-four per cent of death certificates made no mention of diabetes. Diabetes confers an additional risk of death on a population whose mortality is already markedly worse than that of other Australians. Unlike Western diabetic populations, infections and renal disease were more common causes of death than macrovascular disease. Diabetes amplifies the effect of the community prevalence of infection and renal disease.

Adolescent↗
PubMed1995

Persistence of metabolic consequences in the progeny of rats fed a HC formula in their early postnatal life.

First-generation (1-) male and female rat pups were either reared artificially on a high-carbohydrate (HC) or a high-fat (HF) formula or nursed by mother (MF) from day 4 and weaned onto a stock diet on day 24. 1-HC rats compared with sex-matched control rats (1-HF and 1-MF) were hyperinsulinemic and mildly obese by day 60. We investigated the effect of maternal hyperinsulinemia on the second generation (2-) by intragroup breeding. The 2-HC male and female rats were hyperinsulinemic on day 45, had significantly increased growth rate from approximately day 60 onward, and became obese as evidenced by increased adipose tissue mass due to hypertrophy on day 100. The lipogenic capacity of liver and adipose tissues was significantly higher in the 2-HC than in control rats. Thus the metabolic changes that occurred in the first-generation rats fed a HC formula during early postnatal life not only persisted into their adult life but were also passed on to the next generation.

Adipose Tissue↗
PubMed1995

Neonatal rat dietary carbohydrate affects pancreatic islet insulin secretion in adults and progeny.

Neonatal rat pups were artificially reared on isocaloric diets high in carbohydrate (HC) or high in fat (HF) or were naturally reared on mother's milk (MF). The HC adult rats were hyperinsulinemic, normoglycemic, and obese. This study investigates pancreatic islet insulin release (IR) of the adult first-generation (1-) diet-regulated animals and their second-generation (2-) progeny. Male rat 1-HC islets had higher basal IR than either 1-MF or 1-HF control groups. In addition, glucose (17 mM) failed to increase IR above basal values in 1-HC islets, whereas it stimulated IR in 1-MF and 1-HF islets. Similar secretory responses were evoked by 2-ketoisocaproic acid (2-KIC). Female rat 1-MF and 1-HF islets also had higher glucose-stimulated IR compared with 1-HC islets. Male rat 2-HC islets had higher basal IR and reduced sensitivity to glucose and 2-KIC compared with 2-MF islets, which coincided with hyperinsulinemia. Glyceraldehyde-3-phosphate dehydrogenase activity in 1-HC and 2-HC islets was higher than in MF islets. These data suggest that basal IR is higher in islets isolated from animals reared as neonates on a diet high in carbohydrate. Alterations in beta-cell metabolism and secretion probably contribute to the hyperinsulinemia, reduced glucose sensitivity, and glucose intolerance characteristic of this rat model.

Aging↗
PubMed1994

Primary amino acid sequence and structure of human pyruvate carboxylase.

Pyruvate carboxylase (PC) (pyruvate:carbon dioxide ligase (ADP-forming), EC 6.4.1.1.), a nuclear-encoded mitochondrial enzyme, catalyzes the conversion of pyruvate to oxaloacetate. We have isolated and characterized cDNAs spanning the entire coding region of human PC. The sequence of human PC has an open reading frame of 3537 nucleotides which encodes for a polypeptide with a length of 1178 amino acids. The identity of the cDNA as PC is confirmed by comparison to PC cDNAs of other species and sequenced peptide fragments of mammalian PC. The M(r) of the full length precursor protein is 129,576 and that of the mature apoprotein is 127,370. RNA blot analysis from a variety of human tissues demonstrates that the highest level of PC mRNA is found in liver corresponding to this tissue's high level of PC activity. Based on homology with other biotin-containing proteins, the ATP, pyruvate, and biotin-binding sites can be identified. One of two patients with documented PC deficiency was found to be missing PC mRNA, further confirming the identity of this cDNA.

Amino Acid Sequence↗
PubMed1994

Chronic hypoxia impairs the differentiation of 3T3-L1 fibroblast in culture: role of sustained protein kinase C activation.

The effect of hypoxia on 3T3-L1 cell differentiation was examined in confluent cultures incubated with differentiation medium (DM) followed by incubation in growth medium (GM). Control cultures remained in GM throughout the incubation period. Eight days after the incubation, cells were assessed either for changes in morphology by staining with Oil Red O/hematoxylin or harvested to measure protein kinase C activity. Morphological examination of stained cells showed almost complete differentiation of normoxic cells to adipocytes when exposed to DM. By contrast hypoxia caused a dramatic inhibition of differentiation under similar media conditions with only 34 +/- 4% of cells accumulating fat deposits. Cultures sustained in GM under normoxic or hypoxic conditions were devoid of any fat deposits, reflecting an undifferentiated phenotype. Normoxic cells exposed to DM exhibited a significantly lower membrane to cytosolic ratio of protein kinase C in comparison with cells maintained in GM, which is consistent with differentiated and undifferentiated phenotypes, respectively. In comparison with normoxic cells incubated in DM, cells exposed to hypoxia under similar media conditions exhibited a significantly higher membrane to cytosolic ratio of protein kinase C, indicating sustained activation of the enzyme. In addition, cells in differentiation medium exposed to hypoxia in the presence of the protein kinase C inhibitors staurosporine or H7 exhibited a significant increase in the number of fat accumulating cells when compared with hypoxic controls. These studies indicate that chronic hypoxia impairs the differentiation of 3T3-L1 cells to adipocytes in association with the sustained activation of protein kinase C, which appears to play a role in mediating this process.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Solubilities and solvation of aluminum(III), iron(III), and indium(III) 8-hydroxyquinolinates in methanol/water mixtures.

Solubilities are reported for aluminum, indium, and iron(III) complexes of 8-hydroxyquinoline and its 5-nitro, 5-sulfonato, and 7-iodo-5-sulfonato derivatives in water, methanol, and water/methanol mixtures, at 298.2 K. Transfer chemical potentials for the respective complexes have been derived from these data, and their trends are discussed in terms of solvation of the complexes by water and methanol.

Aluminum↗