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Biomedical subjects

D A Hopkinson

Publications and source records attributed to D A Hopkinson.

At least 109 records · Page 6Linked to original sources
PubMed1978

Developmental changes in the protein profiles of human cardiac and skeletal muscle.

1. The use of SDS electrophoresis as a tool for the analysis of development processes in man has been evaluated. 2. The protein profiles of cardiac and skeletal muscle from foetal (10--24 weeks gestation) infant and adult specimens have been analysed and striking developmental changes were found which involved all the major proteins. 3. Before 20 weeks gestation the soluble protein profile of skeletal muscle appears to consist largely of extracellular proteins. 4. Myoglobin was found in foetal cardiac muscle from 20 weeks gestation but was not demonstrable in foetal (greater than 24 weeks) skeletal muscle. Foetal and adult myoglobin were indistinguishable. 5. A limited survey of the protein patterns of brain, liver and kidney was carried out. In general these tissues show less developmental change than skeletal or cardiac muscle.

Adult↗
PubMed1977

Detection after electrophoresis of enzymes involved in ammonia metabolism using L-glutamate dehydrogenase as a linking enzyme.

The use of L-glutamate dehydrogenase (GLUD) as a reagent in staining mixtures to detect the isozymes of enzymes which catalyze the production of ammonia has been investigated. Methods have been devised for the electrophoresis and detection, using GLUD, of seven enzymes: cytidine deaminase, adenosine deaminase, adenosine monophosphate deaminase, arginase, argininosuccinase, D-amino acid oxidase, and D-aspartate oxidase. GLUD-linked staining methods appear to be sensitive, specific, and of general application.

AMP Deaminase↗
PubMed1977

Polymorphism and the subunit structure of enzymes: a contribution to the neutralist-selectionist controversy.

The occurrence of polymorphism in a series of 87 different loci coding for enzyme structure in human populations has been related to the size and the number of subunits in the corresponding enzymes. Polymorphic and nonpolymorphic enzymes did not differ on average in subunit size. However, multimeric enzymes showed a significantly lower incidence of polymorphism than didmonomeric enzymes. A particularly low incidence of polymorphism was noted among multimeric enzymes in which interlocus molecular hybrids occur. The findings are discussed in terms of the "neutralist" and "selectionist" hypotheses of polymorphism.

Enzymes↗
PubMed1977

The distribution of subunit sizes of soluble proteins in human tissues.

1. The distribution of subunit sizes of soluble proteins in human tissues has been examined by the technique of gel filtration chromatography followed by SDS polyacrylamide gel electrophoresis. 2. Up to 101 different polypeptides were identified. These appear to represent primarily the substituent polypeptides of easily solubilized 'non-enzyme' proteins. 3. The subunit sizes ranged between 7000 and 270000 and the distribution was continuous unimodal and skewed. The mean size was estimated at 54 600+/-42 900. 4. The distribution of subunit sizes and the overall mean were found to be similar to those reported for easily solubilized human enzymes and other vertebrate proteins. These results suggest that the average structural gene coding such polypeptides consists of about 1400 base pairs.

Electrophoresis, Disc↗
PubMed1977

An interpretation of human diaphorase isozymes in terms of three gene loci DIA1, DIA2 and DIA3.

NADH and NADPH diaphorase isozymes have been studied in human tissues. Evidence from rare heterozygotes suggests that the red cell and main tissue forms of NADH diaphorase are products of the same locus DIA1. NADPH-dependent diaphorase appears to be the product of a second locus DIA2. A third locus, DIA3, codes for the polymorphic sperm diaphorase. The products of this locus are also found in foetal tissues including placenta and adult brain and gonads. The products of these three loci may be distinguished by their substrate specificity, thermostability and molecular size.

Adolescent↗
PubMed1977

The genetic and biochemical properties of the D-amino acid oxidases in human tissues.

1. Two distinct forms of oxidases catalysing the oxidative deamidation of D-alpha-amino acids have been identified in human tissues: D-amino acid oxidase (DAMOX) and D-aspartate oxidase (DASOX). 2. The enzymes differ in their electrophoretic properties, tissue distribution, binding with flavine adenine denucleotide, heat stability, molecular size and possibly in subunit structure. 3. Neither enzyme exhibits genetic polymorphism in European populations, but a rare electrophoretic variant phenotype (DASOX 2-1) was identified which suggests that the DASOX locus is autosomal and independent of the DAMOX locus.

Amino Acid Oxidoreductases↗
PubMed1976

The occurrence of Hb E Saskatoon in Scotland.

The finding of several examples of Hb E Saskatoon in the Orkney Islands, in Edinburgh and in individuals of Scottish descent in Canada but nowhere else, suggests that the original mutation occurred in Scotland, perhaps in the Orkneys.

Genetics, Population↗
PubMed1976

Purification and properties of an esterase B4 from human liver.

A butyryl esterase, designated B4, has been purified from human liver and some of its properties described. The activity of this enzyme comprises 0.48% of the total butyryl esterase activity found in human liver. Esterase B4 has been distinguished from other butyryl esterases by its preference for the esters of the fluorogenic compounds 4-methyl umbilliferone and fluorescein over naphthyl esters as substrates. Other distinguishing features of this esterase include a relatively high pI (pH 8.7) A monomeric structure of low molecular weight (20 000) and high solubility in solutions of ammonium sulphate.

Amino Acids↗
PubMed1976

The distributions of subunit numbers and subunit sizes of enzymes: a study of the products of 100 human gene loci.

1. A tabulation of subunit numbers and subunit sizes of a series of enzymes which have been studied electrophoretically in man is presented. The series of subunit numbers cover the isozyme products of 100 distinct gene loci. For 99 of these, estimates of subunit size are given. 2. The distribution of subunit numbers in the whole series is as follows: monomers, 28; dimers, 43; trimers, 4; tetramers, 24; octamers, 1. 3. The subunit sizes range from 13,000 to 116,000. The average subunit size for the whole series is close to 45,800. This corresponds to an average polypeptide chain length of about 425 amino acids. 4. No significant differences were found between the average subunit sizes for the separate classes of enzyme with different subunit numbers. 5. The enzymes were categorized in six different types according to the classification of the International Enzyme Commission. It was found that the oxido-reductases differed from the other types (transferases, hydrolases, lyases, isomerases, ligases) in showing a much greater proportion of multimeric enzymes. Only 1 out of 24 oxido-reductases appeared to be a monomer, whereas in the other enzyme types approximately one-third of the enzymes considered appeared to be monomers. No significant differences in subunit size were found between the various enzyme types. 6. It was found that, in general, where two or more separate gene loci are concerned in determining sets of isozymes with the same or very similar enzyme characteristics, there is a close correlation in subunit size and in most, though not all, cases the subunit numbers are the same.

Chromosome Mapping↗