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Biomedical subjects

D A Hopkinson

Publications and source records attributed to D A Hopkinson.

At least 55 records · Page 3Linked to original sources
PubMed1987

Ahaptoglobinaemia in Melanesia: DNA and malarial antibody studies.

To assess the relative contributions of genetic and acquired factors, particularly malaria, to the high frequencies of ahaptoglobinaemia found in Melanesia we have performed DNA and malarial antibody studies in a population from Vanuatu. No gene deletion or rearrangement was found on gene mapping in any ahaptoglobinaemic individual and the frequencies of the Hp1 and Hp2 alleles in the ahaptoglobinaemic group were similar to controls. However, antibodies to Plasmodium falciparum were significantly elevated in the ahaptoglobinaemics. These data suggest that malaria rather than genetic factors is the major cause of ahaptoglobinaemia in Melanesia.

Adult↗
PubMed1987

Studies of genetic linkage between adult polycystic kidney disease and three markers on chromosome 16.

Adult polycystic kidney disease (APKD) is a common genetic disorder that is inherited as an autosomal dominant trait. Recent reports show that, in some families, the APKD gene shows close genetic linkage to two chromosome 16 specific genetic markers. We have been conducting a genetic linkage study using 29 polymorphic isoenzyme and antigenic markers in 184 members of 12 APKD families. We present here the results of linkage analysis using three of these markers which have also been reported to be located on chromosome 16: phosphoglycolate phosphatase (PGP), glutamate pyruvate transaminase (GPT), and haptoglobin (HP). The results show that APKD is closely linked to the PGP locus on the short arm of chromosome 16 (16p13----p12), which is consistent with the previously reported linkage both to PGP and to the alpha globin locus. The genetic distance between PGP and APKD shows a maximum likelihood value of the recombination fraction at zero with a lod score of 5 X 5. There is no evidence of linkage between APKD and either GPT or HP. The PGP polymorphism potentially provides a useful predictive test to complement the use of alpha globin probes in genetic counselling. These tests should provide an efficient means of primary screening of family members at risk, as well as introducing the possibility of prenatal diagnosis.

Alanine Transaminase↗
PubMed1987

Sensitive techniques for the detection of genetic variation in human isozymes.

The principal means by which genetic variation of enzyme proteins has been revealed is the physicochemical separation of isozymes in an electrical field followed by their specific detection. This approach is widely applicable to all types of species and almost every conceivable kind of tissue homogenate or protein secretion. In the human organism alone the products of more than 200 enzyme loci have been investigated by this means and more than 40 genetically determined human isozyme polymorphisms have been identified. Much of this progress has been achieved by the use of conventional gel electrophoresis methods and isozyme detection schemes that depend on enzyme-catalyzed conversion of substrate into chromogens or other types of visible product. However, the functional isozyme detection systems are often of limited sensitivity and are dependent on the good condition of the biological material under analysis and the retention of adequate enzyme activity. Also in some cases, especially where the final product of the detection reaction is not an insoluble compound, the staining may be so diffuse as to offset the high resolving power of the most effective protein separation methods such as isoelectric focusing in ultranarrow pH gradients. The recent development of alternative protein detection methods based on immunoblotting offers a new general approach to isozyme analysis and overcomes some of the limitations of isozyme detection by functional staining methods. The immunoblot methodology is applicable to proteins separated electrophoretically on denaturing gels and on native gels, including proteins separated by isoelectric focusing, and the fidelity of the high-resolution separation techniques appears to be preserved for most proteins by passive or electroblot transfer to nitro-cellulose filters. Furthermore this approach provides considerable flexibility in the sensitivity and the nature of the final reporter signal that is employed. For example, the reporter signal can be amplified by the use of appropriate intermediate reagents to provide a level of detection sensitivity for isozyme proteins which should, even with the present procedures, be far in excess of that which is obtained even by the best functional isozyme staining system. Also the use of an evanescent reporter system such as chemiluminescence may allow multiple analyses of the same immunoblot and hence examination of several different isozyme systems by sequentially using different primary antibodies.

Gene Amplification↗
PubMed1986

Two genetic markers closely linked to adult polycystic kidney disease on chromosome 16.

The genetic locus for autosomal dominant adult polycystic kidney disease was recently assigned to chromosome 16 by the finding of genetic linkage to the alpha globin gene cluster. Further study showed that the phosphoglycolate phosphatase locus is also closely linked to both the locus for adult polycystic kidney disease and the alpha globin gene cluster. These findings have important implications for the prenatal and presymptomatic diagnosis of adult polycystic kidney disease and for a better understanding of its pathogenesis.

Adolescent↗
PubMed1986

Human biochemical genetics of enzyme proteins in the new age of molecular genetics.

Advances in protein biochemistry and immunology have had a major impact on the biochemical and genetical analysis of human proteins and have had applications in the analysis of the primary defects in metabolic disorders, as well as in cDNA cloning. The development and expansion of somatic cell genetic techniques has complemented conventional population and family study genetic methods. A large number of mammalian proteins undergo complex processing to achieve the synthesis of the biologically active protein. Much of this processing is under genetic control. Elucidation of these complexities requires a combination of biochemical, immunological and genetical approaches to determine the nature of the events involved.

Alleles↗
PubMed1986

Chlorpropamide-alcohol flush reaction and isoenzyme profiles of alcohol dehydrogenase and aldehyde dehydrogenase.

To investigate the enzymatic basis of the chlorpropamide-alcohol flush reaction (CPAF) we compared the isoenzyme profiles of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) from liver biopsies, and of ALDH alone from erythrocytes and leucocytes, in CPAF-positive and CPAF-negative subjects. No differences were seen in ADH or ALDH phenotypes, or in the relative activities of the isoenzymes, between the two groups before chlorpropamide was given; in particular, no subjects showed the 'null' ALDH phenotype that is associated with the alcohol flush reaction in oriental subjects. There was a significant decrease in erythrocyte ALDH activity after 7 days' treatment with chlorpropamide in CPAF-positive individuals but no such difference was seen in CPAF-negative subjects. These results indicate that CPAF has a different enzymatic basis from the alcohol flush reaction of oriental subjects and suggest that in CPAF-positive subjects erythrocyte ALDH may be particularly susceptible to inhibition by chlorpropamide.

Alcohol Dehydrogenase↗
PubMed1986

A population genetic survey of the haptoglobin polymorphism in Melanesians by DNA analysis.

We have determined the haptoglobin (Hp) genotypes of 831 Melanesians from Vanuatu, Papua New Guinea, and New Caledonia by Southern blot analysis of DNA extracted from umbilical cord and peripheral blood samples. There was complete agreement between these genotypes and the protein phenotype in cases where both were determined, and genotyping was possible in cases where no serum haptoglobins were measurable. Subtyping of Hp1 alleles using restriction enzymes showed that Melanesians, like Mongoloids and Australian Aboriginals, have only the Hp1S allele. Three cases of Hp Johnson were found in Vanuatu, and further restriction mapping supported a partial gene triplication model for the structure of this variant. We also report a new common BclI restriction enzyme polymorphism upstream of the Hp1 gene. The advantages of using DNA for haptoglobin typing are discussed.

Alleles↗
PubMed1985

The human glutathione S-transferases: developmental aspects of the GST1, GST2, and GST3 loci.

The expression of the GST1, GST2, and GST3 loci in fetal, neonatal, and infant tissues has been studied using starch gel electrophoresis and chromatofocusing. Each locus demonstrated developmental changes in expression, some of which were specific to a single tissue while others occurred in several tissues. GST1 was not usually expressed in any of the tissues studied before 30 weeks of gestation but steadily increased thereafter until adult levels were reached in late infancy. In neonates and older infants the frequencies of the GST1*0, GST1*1, and GST1*2 alleles were 0.79, 0.07, and 0.14, respectively. GST2 was always expressed in liver and adrenal but was only weakly expressed in spleen, cardiac muscle, and diaphragm. In kidney this locus was not usually expressed until nearly 1 year after birth. The GST3 isoenzymes were present in all fetal, neonatal, and infant tissues, although their expression in liver decreased after 30 weeks of gestation. Other isoenzymes with fast anodal mobilities were also identified in several tissues; these are believed to be GST3 isoenzymes that have undergone posttranslational modification rather than products of the putative GST4 locus. No specifically fetal isoenzymes were detected.

Chromatography↗
PubMed1985

Chromosome assignment, biochemical and immunological studies on a human aldehyde dehydrogenase, ALDH3.

The biochemical properties of ALDH isozymes have been examined in human tissues and one set, designated ALDH3, has been studied in detail. These components occur at highest levels in lung and stomach, but were not expressed in fetal tissues, or in blood, hair roots and fibroblasts. The ALDH3 isozymes show optimal activity with benzaldehyde and can use either NAD or NADP as cofactor. Antiserum against a partially purified ALDH3, from stomach, selectively precipitates this isozyme from human tissues and selectively recognizes an homologous component in the rat. Human and rodent ALDH3 were not immunoprecipitated by anti-ALDH1 or anti-ALDH2 antisera. High levels of expression were found in human-rodent hybrids, constructed using rat hepatoma cells, and these hybrids were used to assign the human ALDH3 gene to chromosome 17.

Aldehyde Dehydrogenase↗
PubMed1985

Isolation of a cDNA clone for the human muscle specific carbonic anhydrase, CAIII.

The molecular cloning of cDNA for the human muscle specific carbonic anhydrase CAIII is described. The recombinant was isolated from a human muscle cDNA library prepared in the expression vector lambda gt11, and was characterized by hybridization selection and immunoprecipitation. A comparison of insert cDNA and mRNA sizes suggests that the cDNA is full length and includes extensive untranslated sequences. Preliminary sequence data have confirmed the authenticity of this clone and Southern blotting of human and rodent DNA indicates that it will be a useful probe in the analysis of somatic cell hybrids.

Animals↗
PubMed1985

Analysis of genetic variation in two human thyroxine-binding plasma proteins by immunodetection after isoelectric focusing.

An immunological method for the detection of two thyroxine-binding plasma proteins, thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA), following polyacrylamide gel isoelectric focusing is described. Both proteins show complex electrophoretic patterns, attributable to post-translational glycosylation, which are affected by unfavourable conditions of sample storage. No genetic variants of TBG or TBPA were encountered in a study of N. European individuals (n = 50). The X-linked TBG polymorphism, previously detected using a radiolabelled ligand binding technique in Pacific Islanders, was, however, demonstrable by our new immunological method in a previously untested population (n = 139) from the island of Maewo in Vanuatu.

Gene Frequency↗
PubMed1984

Immunological and biochemical characterization of the human alcohol dehydrogenase chi-ADH isozyme.

The recently identified chi-ADH isozyme was purified from human liver and used to raise immune sera. The chi form of ADH showed no structural resemblance to the ADH1, ADH2 and ADH3 (class I) or ADH4 (class II) isozymes, as judged by its immunological properties. chi-ADH was found in most human tissues including fetal specimens of 16 weeks gestational age and showed a preference for long chain primary alcohols with a double bond in the beta position. We conclude that the locus, designated ADH5, encoding the chi isozyme has a separate evolutionary origin from the other ADH genes.

Adult↗
PubMed1984

The human glutathione S-transferases: studies on the tissue distribution and genetic variation of the GST1, GST2 and GST3 isozymes.

Three sets of isozymes of glutathione-S-transferase (GST) have been identified in human tissues. They differ in their tissue distribution, incidence of genetic variation, susceptibility to inactivation by N-ethylmaleimide and in their electrophoretic mobilities. The GST1 isozymes exhibit four phenotypes, including a common 'null' phenotype attributable to different combinations of three autosomal alleles GST1 1, GST1 2 and GST1 0 of frequency 0.13, 0.23 and 0.64, respectively, in the European population. The genetic polymorphism of GST1 is easily demonstrable in adult liver, kidney, adrenal and stomach but the isozymes are only weakly expressed in skeletal and cardiac muscle and not at all in fetal liver, fibroblasts, erythrocytes, lymphocytes and platelets. The GST2 isozymes also exhibit variant patterns but these are probably due to post-synthetic modification rather than allelic variation. The GST2 isozymes are not detectable in erythrocytes, platelets, cultured fibroblasts or lymphocytoid cells but are found in many other tissues, including fetal liver. GST3 isozymes were found as relatively strong components in every tissue examined except adult liver, with slight tissue to tissue variability in electrophoretic mobility.

Adrenal Glands↗