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M J Powell

Publications and source records attributed to M J Powell.

16 recordsLinked to original sources
PubMed1992

Instrumental comparison for the determination of cadmium and lead in calcium supplements and other calcium-rich matrices.

Three brands of Ca supplement, a laboratory-reagent grade CaCO3 and a certified reference material (International Atomic Energy Agency H-5 Animal Bone) wee analysed for Cd and Pb by four different analytical techniques, viz., anodic stripping voltammetry inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry. The Pb levels measured by the four techniques in the bone powder were within the certified Pb level in this certified reference material. Similarly, no significant differences [p less than 0.05; analysis of variance (ANOVA)] were observed in samples with Pb concentrations greater than 1 microgram g-1. However, the Pb levels in the laboratory-reagent grade CaCO3 obtained by flame atomic absorption spectrometry (0.79 micrograms g-1) averaged about three times higher than those measured by the other three techniques (i.e., 0.25 micrograms g-1). Although no significant differences (p less than 0.05; ANOVA) in Cd levels were observed within any of the samples (intra-sample variability), the Cd concentration measured in the different Ca supplements (inter-sample variability) varied by three orders of magnitude (ranging from 0.07 to 3.59 micrograms g-1).

Analysis of Variance↗
PubMed1992

Prevalence of diabetes in different regional and religious south Asian communities in Coventry.

The prevalence of Type 2 (non-insulin-dependent) diabetes in different South Asian (Asian) communities was compared during the Coventry Diabetes Study, a cross-sectional house to house screening programme for diabetes. Screening was by capillary whole blood glucose measurement with oral glucose tolerance tests when concentrations were greater than or equal to 6.0 mmol l-1 within 2 h of a meal or greater than or equal to 5.0 mmol l-1 2 h or more after a meal and a random 10% of others. Of the 4395 resident Asians, 94% were represented by five communities: Punjabi Sikhs, Punjabi Hindus, Gujerati Moslems, Gujerati Hindus, and Pakistani Moslems. Response to screening was 77-89% and to glucose tolerance test was 59-79%. Differences in anthropometry, socioeconomic circumstances, and migratory patterns were found, but all groups had a higher prevalence of Type 2 diabetes than Europeans. Gujerati Moslems had the highest age-adjusted prevalence (per 1000) of Type 2 diabetes (males: 160 (95% CI 107-228), females: 204 (95% CI 144-283)) when compared with the other Asian groups (males: Punjabi Sikhs 89(72-110), Pakistani Moslems 91(67-120), Gujerati Hindus 84(57-120), Punjabi Hindu 113(74-171); females: Punjabi Sikhs 75(60-94), Pakistani Moslems 103(78-133), Gujerati Hindus 88(62-122), Punjabi Hindu 116(77-174)). That all the Asian groups had a high prevalence of diabetes, in spite of their known dietary, cultural, and socioeconomic differences, suggests that the Asian predisposition to Type 2 diabetes is inherited although environmental factors may be necessary for this to be expressed.

Adult↗
PubMed1991

The Coventry Diabetes Study: prevalence of diabetes and impaired glucose tolerance in Europids and Asians.

The Coventry Diabetes Study compared the prevalence of diabetes and impaired glucose tolerance in adult Asians and Europids in relation to age, sex and body mass index. The study involved a cross-sectional house to house screening for diabetes in the electoral ward of Foleshill, Coventry, a traditional area for migration into the city. Subjects with a high blood glucose and 10 per cent of others were referred for a 75 g oral glucose tolerance test. Of the 10,304 adult residents aged 20 years or above, 3529 (64 per cent) of 5508 Europids and 3692 (84 per cent) of 4395 Asians were either screened for diabetes or already diabetic and 719 (65 per cent) of 1114 Europids and 780 (72 per cent) of 1084 Asians invited to glucose tolerance test attended. Although the prevalence of insulin-dependent diabetes was similar, the age-adjusted prevalence of non-insulin-dependent diabetes was 3.2 per cent (95 per cent confidence interval (CI): 2.6-4.0) and 4.7 per cent (CI per cent 4.0-5.5) in Europid males and females but 12.4 per cent (CI 11.0-13.8) and 11.2 CI per cent (10.0-12.5) in Asian males and females giving prevalence ratios of 3.9 per cent (3.1-5.0) in males and 2.4 per cent (2.0-2.9) in females. These differences were not due to differences in body mass index. The prevalence of impaired glucose tolerance was also higher in Asians aged below 60 years, and in 65 per cent of Europids and 40 per cent of Asians non-insulin-dependent diabetes was previously undiagnosed. The non-insulin-dependent diabetes/impaired glucose tolerance ratio was significantly higher in Asians than Europids. Non-insulin-dependent diabetes in Asians differs from that in Europids. Besides the higher overall prevalence, there is a greater proportion of males, a lower proportion undiagnosed disease, a younger age at diagnosis and a greater proportion of abnormal glucose tolerance that is due to non-insulin-dependent diabetes.

Adult↗
PubMed1991

Electrochemiluminescence detection for development of immunoassays and DNA probe assays for clinical diagnostics.

Electrochemiluminescence (ECL) has been developed as a highly sensitive process in which reactive species are generated from stable precursors (i.e., the ECL-active label) at the surface of an electrode. This new technology has many distinct advantages over other detection systems: no radioisotopes are used; detection limits for label are extremely low (200 fmol/L); the dynamic range for label quantification extends over six orders of magnitude; the labels are extremely stable compared with those of most other chemiluminescent systems; the labels, small molecules (approximately 1000 Da), can be used to label haptens or large molecules, and multiple labels can be coupled to proteins or oligonucleotides without affecting immunoreactivity, solubility, or ability to hybridize; because the chemiluminescence is initiated electrochemically, selectivity of bound and unbound fractions can be based on the ability of labeled species to access the electrode surface, so that both separation and nonseparation assays can be set up; and measurement is simple and rapid, requiring only a few seconds. We illustrate ECL in nonseparation immunoassays for digoxin and thyrotropin and in separation immunoassays for carcinoembryonic antigen and alpha-fetoprotein. The application of ECL for detection of polymerase chain reaction products is described and exemplified by quantifying the HIV1 gag gene.

2,2'-Dipyridyl↗
PubMed1990

Isolation of a gene encoding a mitochondrial HSP70 protein from Schizosaccharomyces pombe.

We have isolated cDNA and genomic clones encoding a mitochondrial HSP70 protein from Schizosaccharomyces pombe. Nucleotide sequence analysis indicates that the encoded protein is homologous to the HSP70s of other organisms. The highest degree of amino acid conservation is with the proteins encoded by the Escherichia coli dnaK gene, the SSC1 gene of Saccharomyces cerevisiae and the MTP70 gene of Trypanosoma cruzi, the latter two having recently been shown to be located in the mitochondria. Western-blot analysis with immunoglobulin G raised against a peptide corresponding to the C terminus of the SSP1 protein indicates a 70-kDa protein which is associated with the mitochondria.

Amino Acid Sequence↗
PubMed1990

Site specificity of a catalytic vasoactive intestinal peptide antibody. An inhibitory vasoactive intestinal peptide subsequence distant from the scissile peptide bond.

Ten fragments of vasoactive intestinal peptide (VIP) were tested for reactivity with a human catalytic autoantibody that cleaves full-length VIP(1-28) at the Gln16-Met17 peptide bond. A large COOH-terminal subsequence, VIP(15-28), was bound by the autoantibody with high affinity (Ki 1.25 nM), suggesting that it is the antibody binding epitope. VIP(22-28), a short subsequence distant from the scissile bond, inhibited the binding (Ki 242 microM) and hydrolysis (Ki 260 microM) of full-length VIP by the catalytic autoantibody in a competitive fashion. The autoantibody did not show detectable binding of short VIP subsequences that encompass the scissile bond (VIP(15-21), VIP(11-17), and VIP(13-20]. These data show that residues 22-28, located four amino acids distant from the scissile bond, contribute in recognition of VIP by the catalytic autoantibody.

Amino Acid Sequence↗
PubMed1990

Expression and secretion of aequorin as a chimeric antibody by means of a mammalian expression vector.

A fusion protein has been expressed from the relevant genes in mammalian cells consisting of the photoprotein aequorin and an anti-4-hydroxy-3-nitrophenacetyl antibody gene. This chimeric antibody has allowed the development of a sensitive luminescent immunoassay. Initially the cDNA of the photoprotein aequorin from Aequorea victoria was cloned and expressed in Escherichia coli. The gene was expressed as apoaequorin and, by using luciferin isolated from Renilla reniformis, its activity was found essentially identical to native aequorin. The aequorin gene was subcloned into a mammalian expression vector to produce a fusion protein directing secretion of apoaequorin; the aequorin gene was fused to the 3' terminus of an immunoglobulin heavy-chain gene that directed expression of an anti-4-hydroxy-3-nitrophenacetyl antibody. The gene fusion contained the variable region, the constant region domain 1, and part of domain 2 for the IgG2b mouse immunoglobulin, followed by the aequorin gene. Transfection of the chimeric gene into a cell line expressing the complementary lambda 1 light chain, J558L, allowed recovery of a chimeric antibody with binding specificity for the 4-hydroxy-3-nitrophenacetyl group and the related 4-hydroxy-3-iodo-5-nitrophenacetyl hapten. The Ca2(+)-dependent bioluminescent activity of aequorin was also recovered.

Aequorin↗
PubMed1989

Catalytic hydrolysis of vasoactive intestinal peptide by human autoantibody.

Vasoactive intestinal peptide (VIP) labeled with 125I, [Tyr10-125I]VIP, can be hydrolyzed by immunoglobulin G (IgG) purified from a human subject, as judged by trichloroacetic acid precipitation and reversed-phase high-performance liquid chromatography (HPLC). The hydrolytic activity was precipitated by antibody to human IgG, it was bound by immobilized protein G and showed a molecular mass close to 150 kilodaltons by gel filtration chromatography, properties similar to those of authentic IgG. The Fab fragment, prepared from IgG by papain treatment, retained the VIP hydrolytic activity of the IgG. Peptide fragments produced by treatment of VIP with the antibody fraction were purified by reversed-phase HPLC and identified by fast atom bombardment-mass spectrometry and peptide sequencing. The scissile bond in VIP deduced from these experiments was Gln16-Met17. The antibody concentration (73.4 fmol per milligram of IgG) and the Kd (0.4 nM) were computed from analysis of VIP binding under conditions that did not result in peptide hydrolysis. Analysis of the antibody-mediated VIP hydrolysis at varying concentrations of substrate suggested conformity with Michaelis-Menton kinetics (Km). The values for Km (37.9 X 10(-9) M) and the turnover number kcat (15.6 min-1) suggested relatively tight VIP binding and a moderate catalytic efficiency of the antibody.

Amino Acid Sequence↗
PubMed1989

Prevalence of diabetes in a predominantly Asian community: preliminary findings of the Coventry diabetes study.

To assess the prevalence of both diagnosed and undiagnosed diabetes mellitus in an area of predominantly Asian population the Coventry diabetes study is carrying out house to house screening for diabetes in people aged 20 and over in Foleshill, Coventry. In the first five of 12 areas to be studied 2130 of 2283 Asian (93.3%) and 1242 of 1710 white subjects (72.6%) aged 20-79 agreed to be screened. The prevalence of diabetes adjusted to 1987 demographic estimates was 11.2% in Asian men and 8.9% in Asian women whereas it was 2.8% in white men and 4.3% in white women. The excess of diabetes in Asian subjects was predominantly of non-insulin-dependent diabetes, and no significant differences in body mass were found to account for the higher prevalence. Diabetes had not been diagnosed previously in at least 26% of the white and 30% of the Asian diabetics screened, and it is estimated that in this community the condition remains undiagnosed in 42% of white and 40% of Asian diabetics.

Adult↗
PubMed1989

Characterization of a chimeric aequorin molecule expressed in myeloma cells.

We have constructed a chimeric aequorin consisting of a fragment of the anti-NP immunoglobulin gene fused to the aequorin gene. Expression in a myeloma cell line has produced a Fab'-like molecule that has the ability to bind NIP specifically and generate bioluminescent activity. It takes approximately 8 h at 4 degrees C in the presence of 2-mercaptoethanol and coelenterazine to regenerate luminescent activity. While the flash kinetics of this recombinant molecule are similar to native aequorin, its quantum efficiency is ten times lower. Preliminary studies have been conducted to ascertain its usefulness for immunoassays. We have shown for this chimeric aequorin 7 x 10(-19) moles can be detected in solution, also it can be used in a solid-phase assay and is stably stored at -70 degrees C for at least 2 months.

Aequorin↗
PubMed1985

Microbody-like organelles as taxonomic markers among Oomycetes.

Zoospores of Oomycetes contain a variety of microbody-like organelles with highly structured matrices. Although in general their function is unknown, the appearance of similar organelles in related taxa suggests the ultrastructural differences could be used as taxonomic characters. This study surveys microbody-like organelles of oomycetous zoospores to determine if this is an additional criterion by which the phylogeny of these fungi can be evaluated. In zoospores of the order Saprolegniales, kinetosome-associated organelles (K-bodies) are found which typically consist of tubular and/or granular matrices. K-bodies are not found associated with kinetosomes in zoospores of the Peronosporales, but microbodies containing tubules, and in some genera marginal plates, are located near the kinetosomes, along the groove, and in other peripheral areas. K-bodies have been reported in only one member of the order Lagenidiales. These K-bodies lack a granular matrix, but contain a single curved plate from which tubules arise, forming a cone. In the one genus of the Leptomitales examined, a similar K-body contains a plate and scattered tubules. Organisms with similar microbody-like organelles are probably more closely related than those with different types of microbody-like organelles. The presence of an organelle resembling K-bodies in zoospores of an alga in the Tribophyceae supports the phylogenetic association between algae and Oomycetes. A complete survey of Oomycete genera may well reveal intermediates between the structurally different types of microbody-like organelles, allowing the reconstruction of the phylogenetic history of an organelle.

Biological Evolution↗
PubMed1978

Phylogenetic implications of the microbody-lipid globule complex in zoosporic fungi.

Chytridiomycetous fungal zoospores contain a unique and intricate association of organelles, the 'microbody-lipid globule complex' (MLC). The spatial arrangement of organelles in the MLC appears important in the utilization of lipid globules for energy, but in addition, the structural association of organelles in the MLC reveals phylogenetic trends within this diverse group of organisms. Variations in the structure of the MLC correlate well with current phylogenetic concepts of aquatic fungi, yet suggest new relationships among these posteriorly uniflagellate zoospores. Based upon the organization of organelles in the MLC, 4 basic patterns of MLCs can be recognized, and these correspond to the 4 orders of Chytridiomycetes. The MLC in its simplest form consists of a microbody appressed to the edge of a lipid globule. In more highly organized MLCs, mitochondria subtend the microbody and a cisterna surmounts one side of the lipid globule. The organization and structure is still more complex in other MLCs where ER is elaborated into a tubular network of membranes or where small microbodies or mitochondria fuse into 'giant' organelles. The structural organization of the MLC provides an additional criterion by which the phylogeny of awuatic fungi can be evaluated.

Fungi↗