Search PubMed⌕ Search

Biomedical subjects

J B Whitfield

Publications and source records attributed to J B Whitfield.

At least 73 records · Page 4Linked to original sources
PubMed1985

Individual differences in plasma ALT, AST and GGT: contributions of genetic and environmental factors, including alcohol consumption.

The causes of individuality of the plasma enzymes alanine aminotransferase (ALT; EC 2.6.1.2), aspartate aminotransferase (AST; EC 2.6.1.1) and gamma-glutamyl transferase (GGT; EC 2.3.2.2) were investigated in a study of 206 pairs of twins. Between-person variance was greater in men than women, while within-person variation was similar in both sexes. Plasma ALT and AST levels were affected by genetic factors, while GGT was affected by some environmental factor shared by co-twins. In the men, alcohol intake had a significant but small effect on all three enzyme levels, and since alcohol consumption was highly heritable, this appeared as a genetic influence on enzyme activities. The major factors involved in the observed correlations between these enzymes were a non-shared environmental factor other than alcohol affecting ALT, AST and GGT, and a genetic factor affecting only ALT and AST.

Adolescent↗
PubMed1985

Can potentially infectious specimens containing hepatitis B virus be identified on the basis of their biochemical profile?

The potential infectivity of 1129 randomly selected plasma specimens was directly assayed by hepatitis B virus (HBV) DNA dot-hybridization. Presence or absence of HBV was then correlated with a biochemical profile of 20 common analytes obtained on these same specimens. We found that potentially infectious specimens could not be identified on the basis of any combination of simple biochemical tests; indeed, the infectious specimens were more "normal" in some tests of liver function than were the non-infectious specimens.

Blood Specimen Collection↗
PubMed1984

The effects of inheritance on constituents of plasma: a twin study on some biochemical variables.

Heritability and within-person repeatability of thirteen constituents of plasma were assessed in a study of 206 pairs of male and female twins. Repeat measurements were available on 44 pairs. For bilirubin, calcium, creatinine, phosphate and potassium, the individuality of these characteristics was genetic in origin. Total protein, albumin and globulin showed significant heritability but considerable variation between occasions, while bicarbonate, chloride, iron, sodium and urea showed mainly environmental effects.

Adolescent↗
PubMed1984

Blood pressure and chemistry: some correlations and apparent correlations.

The reported correlation between plasma calcium and blood pressure has been investigated in 412 young men and women. In this sample, it seemed to be due to a stronger correlation between blood pressure and plasma albumin. Blood pressures were also significantly correlated with plasma high-density lipoprotein in men and with plasma uric acid in women.

Adolescent↗
PubMed1984

Carboxyhemoglobin, cotinine, and thiocyanate assay compared for distinguishing smokers from non-smokers.

We compared cotinine, carboxyhemoglobin, and thiocyanate concentrations in blood sampled from 187 cigarette smokers and 181 non-smokers. All three differed significantly between smokers and non-smokers. Cotinine performed best as a test for assessing smoking status, with a sensitivity of 98% as compared with 94% for carboxyhemoglobin and 80% for thiocyanate, all at a specificity of 95%. These differences were statistically significant. Results by none of these three methods correlated well with number of cigarettes smoked per day.

Carboxyhemoglobin↗
PubMed1983

Plasma lipids in twins. Environmental and genetic influences.

A study on 205 pairs of male and females twins, aged from 18 to 34 years. showed significant heritabilities for total and high density lipoprotein cholesterol and for triglycerides. Significant effects of shared environment were also found for total and HDL cholesterol, possibly to a greater extent in women than in men. Triglycerides showed greater variance in men but a model specifying different sized environmental and genetic parameters in the two sexes gave a good fit and indicated that the factors influencing plasma triglycerides are the same in men and women although the effects they produce are scaled differently.

Adolescent↗
PubMed1983

Inheritance and alcohol as factors influencing plasma uric acid levels.

Variation in plasma uric acid levels in 206 pairs of male and female twins, aged from 18 to 34 years, was consistent with a simple model including only individual environmental and additive genetic effects and a heritability of h2 = 0.73. Individual environmental variation was estimated to be approximately the same as variation of individuals measured on two occasions. Correlations of DZ pairs were also consistent with sex-linked genetic effects. In men there was a significant genetic correlation with weekly alcohol consumption and as much as 18% of the variation in uric acid levels could be accounted for by genetic variation in alcohol consumption.

Adolescent↗
PubMed1983

Do the MN and Jk systems influence environmental variability in serum lipid levels?

Significant heterogeneity in the distribution of within pair variances of serum total cholesterol, HDL cholesterol, non HDL cholesterol and triglyceride levels has been found in one or both of two samples of MZ twins. We have found some support for the observation of Magnus et al. (1981) that M- pairs have greater environmental variability in cholesterol levels than M+ pairs and weaker evidence that Jka+ pairs are more variable than Jka- pairs. However, these effects appear to be more striking on triglyceride levels. The low power of the variance ratio test is advanced as a possible reason for the inconsistencies in these findings.

Adolescent↗
PubMed1983

Determinants of variation in plasma alkaline phosphatase activity: a twin study.

Plasma alkaline phosphatase activity has been measured in 204 pairs of twins aged 18-34. Estimated genetic variance was the same in men and women, after exclusion of the youngest men, but environmental variance was greater in men so that the heritability was .90 +/- .02 in the women and .71 +/- .05 in the 19-34-year-old men. About 15% of the genetic variance was associated with the ABO blood group polymorphism, which is known to affect intestinal alkaline phosphatase. Differences in plasma alkaline phosphatase activity between normal people may be mainly due to genetically determined proportions of isoenzymes of differing stability.

ABO Blood-Group System↗
PubMed1981

A multivariate assessment of alcohol consumption.

Subjects attending a large, multiphasic health screening centre in Sydney, Australia estimated their alcohol consumption and specimens of their blood were analysed. The most useful univariate estimates of alcohol consumption were erythrocyte mean corpuscular volume and plasma aspartate-aminotransferase, gamma-glutamyl-transpeptidase, triglycerides and uric acid. The most statistically significant of these tests have been combined to form a multivariate predictor of alcohol intake which is more successful in identifying heavy-drinkers than single tests. To describe this population further, and to aid comparisons between populations, information about non-drinkers has also been provided.

Alcoholism↗
PubMed1981

Effect of drinking on correlations between biochemical variables.

Several clinical laboratory tests correlate with alcohol consumption, for example, the plasma activities of gamma-glutamyl transpeptidase (GGT) and aspartate aminotransferase (AST), the concentrations of triglycerides (TG) and uric acid (UA) and the erythrocyte mean corpuscular volume (MCV). The correlations of these test results with each other have been studied in a population of men attending a multiphasic health-screening centre. The patterns of correlation were of two types: those between the pairs of variables GGT/TG/UA, TG/AST, and TG/UA were all unchanged as the level of alcohol consumption increased; the pairs of variables GGT/MCV, UA/AST, AST/MCV, UA/MCV, and GGT/AST all became more highly correlated as the level of alcohol consumption increased.

Adolescent↗
PubMed1980

The effects of diphenylhydantoin on the relationship between high-density lipoprotein cholesterol and several biochemical assays.

Correlations have been calculated between high-density lipoprotein cholesterol and total plasma cholesterol, albumin, gamma-glutamyl transpeptidase, aspartate aminotransferase, alkaline phosphatase, triglyceride, urea, creatinine and uric acid for diphenylhydantoin (DPH) users and for subjects attending a multiphasic health screening centre. For women DPH users, high-density lipoprotein levels correlated significantly with gamma glutamyl transpeptidase, cholesterol and alkaline phosphatase. These correlations were significantly different from those found for male DPH users and from subjects attending the health screening centre. In male DPH users, high-density lipoprotein cholesterol correlates negatively with urea and uric acid levels, a relationship which is found neither in women DPH users nor in the health screening centre population.

Adolescent↗
PubMed1979

An enzymic and centrifugal method for estimating high-density lipoprotein cholesterol.

Enzymic measurement of high-density lipoprotein cholesterol with a centrifugal analyzer is described. We used polyethylene glycol (Mr 6000), final concentration 100 g/L, to precipitate low-density and very-low-density lipoproteins, thereby eliminating the difficulties of the commonly used heparin/Mn2+ precipitation method and facilitating the use of ethylenediaminetetraacetate-stabilized plasma. As measured by rocket immunoelectrophoresis, this final concentration of polyethylene glycol completely precipitates beta-lipoproteins, leaving the alpha-lipoproteins in solution. Between-run reproducibility (CV) was 3.6%, within-run reproducibility (CV) 0.8%. Reagent costs currently are $US 0.13 per test and large numbers of samples can be handled conveniently. Normal ranges were compiled for 539 men and 444 women. The high-density lipoprotein cholesterol for men was 1.20 +/- 0.31 (SD) mmol/L and for women 1.52 +/- 0.38 (SD) mmol/L.

Adult↗