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Biomedical subjects

S Whitehouse

Publications and source records attributed to S Whitehouse.

At least 37 records · Page 2Linked to original sources
PubMed1981

The prevalence of diabetes in the rural and urban Polynesian population of Western Samoa.

Rural-urban comparisons of diabetes prevalence were made in te Polynesian population of Western Samoa. The prevalence of diabetes in the urban population was almost three times that in the rural (10.1% versus 3.6%). While the urban male and female subjects were significantly more obese than their rural counterparts, the difference in prevalence rate could not be wholly explained on the basis. Diabetes prevalence was still approximately double in urban subjects when we compared the rural and urban populations after removing the differences in obesity and age. The results suggest that, apart from age and obesity, other factors, e.g., differences in diet, physical activity, or stress (or a combination of these), may participate in the rural to urban difference in diabetes prevalence.

Adult↗
PubMed1980

Blood pressure studies in two Pacific populations with varying degrees of modernisation.

The prevalence of hypertension and the change in blood pressure with age were investigated in a Polynesian population (Tuvalu), and in a Micronesian population (Nauru) in the South Pacific region. Hypertension was present in 27.2 percent of the Nauruans and 11.1 percent of the Tuvaluans. Both population groups also showed a rise in mean blood pressure with increasing age--a phenomenon apparently absent in traditional-living populations of the world but present in western societies.

Adolescent↗
PubMed1980

Electrocardiographic findings in a partly urbanised Polynesian population. The Funafuti survey.

Electrocardiographic changes defined as probable or suspect ischaemic heart disease and coded according to the Minnesota coding system, were found in 14 (10.3 percent) of 136 Funafutians surveyed. Of these abnormal electrocardiograms, nine were classified as "probable" ischaemia and five as "suspect" ischaemia. There was a higher prevalence of electrocardiographic ischaemia in the female population compared with the male population of Funafuti. This is consistent with the greater degree of obesity and higher prevalence of diabetes previously reported in females in this population.

Adolescent↗
PubMed1979

Possibility of shape conformers of the protein inhibitor of the cyclic adenosine monophosphate dependent protein kinase.

The heat-stable, protein inhibitor of the cyclic adenosine monophosphate (cAMP) dependent protein kinase [Walsh, D. A., Ashby, C. D., Gonzalez, C., Calkins, D., Fischer, E., & Krebs, E (1971a) J. Biol. Chem. 246, 1977-1985] has been purified to homogeneity from rabbit skeletal muscle by preparative electrophoresis. Employing a more sensitive assay system, we detected multiple charged forms of the inhibitor on diethylaminoethyl chromatography; the form that has been further characterized is the predominant species in skeletal muscle comprising greater than 70% of the total. The apparent molecular weight of the protein inhibitor, as determined by Sephadex G-75 gel exclusion chromatography, is 22 000 in initial cellular extracts and at all stages during the purification prior to the final purification step of preparative gel electrophoresis, after which the homogeneous protein exhibits a molecular weight of 11 000. These two forms are designated I and I', respectively. The I form migrates with an apparent molecular weight of 10 000 on nondenaturing gel electrophoresis and of 10 500-11 500 on sodium dodecyl sulfate (NaDodSO4) gel electrophoresis; the I' form migrates with an apparent molecular weight of 6500-8300 on NaDodSO4 electrophoresis and has a minimum molecular weight of 10 400 by amino acid analysis. Taking into account the anomalous behavior displayed by low molecular weight proteins with the various techniques employed, we suggest that the I and I' forms of the protein inhibitor may represent shape conformers.

Amino Acids↗
PubMed1979

Genetic susceptibility to diabetes mellitus: the distribution of properdin factor B (Bf) and glyoxalase (GLO) phenotypes.

The distribution of phenotypes controlled by two loci on chromosome 6 has been studied in a series of 239 patients with type 1 (insulin-dependent) and 297 patients with type 2 (non-insulin-dependent) diabetes mellitus. At the properdin factor B (Bf) locus there is a significant increase in the frequency of the BfSu and BfF1 alleles for type 1 patients, and the combined inc;rease in frequency of BfS1 and BfF1 in those patients is highly significant. The relative risk for F1 is 6.2 and for F1 and S1 combined is 5.3. These results confirm the association with F1 reported recently by Raum and co-workers in Boston. The two rare alleles BfS1 and BfF1 are in significant negative disequilibrium with HLA B8. For the glyoxalase (GLO) locus there is a slight but nonsignificant increase in the frequency of the GLO2 allele, but a significant disturbance in the distribution of the GLO phenotypes for type 2 patients. These results for the GLO alleles may be due to stratification in our series of type 2 patients. Further studies are in progress to test this hypothesis.

Alleles↗
PubMed1979

Ethnic variability in the plasma insulin response to oral glucose in Polynesian and Micronesian subjects.

The pattern of insulin response to oral glucose over a wide range of glucose tolerance has been studied in two separate ethnic groups--Polynesians and Micronesians. Fasting insulin concentrations were relatively unchanged over the entire range of glucose tolerance in both populations, irrespective of whether comparable lean or obese samples of both groups were studied. The patterns of 2-h plasma insulins were similar over the whole range of glucose tolerance in Polynesians and Micronesians. However, in the comparisons of all subjects, or lean or obese groups of these populations, the plasma insulin concentrations of the Micronesians were both consistently and significantly higher. As the data analysis was arranged to take into account groups with identical 2-h plasma glucose concentrations and comparable degrees of obesity, the differences cannot be attributed to differences in the glucose levels or in obesity. In the presence of similar fasting insulin concentrations, these findings imply an ethnic variability in the pancreatic beta-cell response to oral glucose.

Adolescent↗
PubMed1978

High prevalence of hyperuricaemia and gout in an urbanised Micronesian population.

The prevalence of hyperuricaemia and gout was investigated in the Micronesian inhabitants of the highly urbanised central Pacific island of Nauru. Sixty-four per cent of men and 60% of women aged 20 years and over had hyperuricaemia--the highest prevalence rates yet reported for a population. The hyperuricaemia in men was accompanied by a high prevalence of clinical gout (6.9%). While the hyperuricaemia is probably genetic, the high prevalence of gout may be related to the environmental change from the traditional island style of living to one of almost complete Westernisation.

Adult↗
PubMed1978

Bimodality of fasting and two-hour glucose tolerance distributions in a Micronesian population.

While frequency distributions of glucose concentrations in Caucasian populations are unimodal, bimodality has been described in the Pima Indians, a population with an extremely high prevalence of diabetes. Venous plasma glucose concentrations at fasting and after a 75-gm. oral glucose load were determined in 596 Nauruans, a Micronesian population with a diabetes prevalence of the same order as the Pima Indians. In both sexes and in subjects 10 to 19 years, the frequency distributions of the logarithms of the fasting and two-hour glucose values were clearly unimodal. In most sex and age groups of 20 years and older, the frequency distributions of fasting and two-hour glucose values were bimodal and consistent with a model of two overlapping Gaussian distributions. This population is characterized by marked obesity. However, there was no significant difference in the degree of obesity between subjects in the first and second curves of the bimodal distribution. This makes it unlikely that the bimodality is a consequence of the marked obesity seen in both the Pima and Nauru populations. The data show that among Nauruans, as with the Pimas, the frequency distribution of glucose concentrations can be used to separate the population into normal and hyperglycemic groups.

Adolescent↗
PubMed1978

The effect of rigor mortis on the passage of erythrocytes and fluid through the myocardium of isolated dog hearts.

The effect of normal and artificially induced rigor mortis on the vascular passage of erythrocytes and fluid through isolated dog hearts was studied. Increased rigidity of 6-mm thick transmural sections through the centre of the posterior papillary muscle was used as an indication of rigor. The perfusibility of the myocardium was tested by injecting 10 ml of 1% sodium fluorescein in Hanks solution into the circumflex branch of the left coronary artery. In prerigor hearts (20 minute incubation) fluorescein perfused the myocardium evenly whether or not it was preceded by an injection of 10 ml of heparinized dog blood. Rigor mortis developed in all hearts after 90 minutes incubation or within 20 minutes of perfusing the heart with 50 ml of 5 mM iodoacetate in Hanks solution. Fluorescein injected into hearts in rigor did not enter the posterior papillary muscle and adjacent subendocardium whether or not it was preceded by heparinized blood. Thus the vascular occlusion caused by rigor in the dog heart appears to be so effective that it prevents flow into the subendocardium of small soluble ions such as fluorescein.

Animals↗
PubMed1976

Regulation of pyruvate dehydrogenase in rat heart. Mechanism of regulation of proportions of dephosphorylated and phosphorylated enzyme by oxidation of fatty acids and ketone bodies and of effects of diabetes: role of coenzyme A, acetyl-coenzyme A and reduced and oxidized nicotinamide-adenine dinucleotide.

The proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart was decreased by alloxan-diabetes or by perfusion with media containing acetate, n-octanoate or palmitate. The total activity of the dehydrogenase was unchanged. 2. Pyruvate (5 or 25mM) or dichloroacetate (1mM) increased the proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart, presumably by inhibiting the pyruvate dehydrogenase kinase reaction. Alloxan-diabetes markedly decreased the proportion of active dehydrogenase in hearts perfused with pyruvate or dichloroacetate. 3. The total activity of pyruvate dehydrogenase in mitochondria prepared from rat heart was unchanged by diabetes. Incubation of mitochondria with 2-oxo-glutarate plus malate increased ATP and NADH concentrations and decreased the proportion of active pyruvate dehydrogenase. The decrease in active dehydrogenase was somewhat greater in mitochondria prepared from hearts of diabetic rats than in those from hearts of non-diabetic rats. Pyruvate (0.1-10 mM) or dichloroacetate (4-50 muM) increased the proportion of active dehydrogenase in isolated mitochondria presumably by inhibition of the pyruvate dehydrogenase kinase reaction. They were much less effective in mitochondria from the hearts of diabetic rats than in those of non-diabetic rats. 4. The matrix water space was increased in preparations of mitochondria from hearts of diabetic rats. Dichloroacetate was concentrated in the matrix water of mitochondria of non-diabetic rats (approx. 16-fold at 10 muM); mitochondria from hearts of diabetic rats concentrated dichloroacetate less effectively. 5. The pyruvate dehydrogenase phosphate phosphatase activity of rat hearts and of rat heart mitochondria (approx. 1-2 munit/unit of pyruvate dehydrogenase) was not affected by diabetes. 6. The rate of oxidation of [1-14C]pyruvate by rat heart mitochondria (6.85 nmol/min per mg of protein with 50 muM-pyruvate) was approx. 46% of the Vmax. value of extracted pyruvate dehydrogenase (active form). Palmitoyl-L-carnitine, which increased the ratio of [acetyl-CoA]/[CoA] 16-fold, inhibited oxidation of pyruvate by about 90% without changing the proportion of active pyruvate dehydrogenase.

Acetates↗
PubMed1975

Regulation of mammalian pyruvate dehydrogenase.

In mammalian tissues, two types of regulation of the pyruvate dehydrogenase complex have been described: end product inhibition by acetyl CoA and NADH: and the interconversion of an inactive phosphorylated form and an active nonphosphorylated form by an ATP requiring kinase and a specific phosphatase. This article is largely concerned with the latter type of regulation of the complex in adipose tissue by insulin (and other hormones) and in heart muscle by lipid fuels. Effectors of the two interconverting enzymes include pyruvate and ADP which inhibit the kinase, acetoin which activates the kinase and Ca2+ and Mg2+ which both activate the phosphatase and inhibit the kinase. Evidence is presented that all components of the pyruvate dehydrogenase complex including the phosphatase and kinase are located within the inner mitochondrial membrane. Direct measurements of the matrix concentration of substrates and effectors is not possible by techniques presently available. This is the key problem in the identification of the mechansims involved in the alterations in pyruvate dehydrogenase activity observed in adipose tissue and muscle. A number of indirect approaches have been used and these are reviewed. Most hopeful is the recent finding in this laboratory that in both adipose tissue and heart muscle, differences in activity of pyruvate dehydrogenase in the intact tissue persist during preparation and subsequent incubation of mitochondria.

Acetates↗
PubMed1975

Histidines and renal function.

The results of endogenous renal clearances of 3-methylhistidine and histidine in twelve patients with normal and decreased renal functions are reported. Differences in the renal handling of the amino acids have been established. 3-methylhistidine showed a hyperbolic relationship between serum concentration and inulin clearance: histidine a linear relationship. The percentage tubular reabsorption of 3-methylhistidine was found to be about half that of histidine. The possible use of the measurement of serum 3-methylhistidine concentration as an index of renal insufficiency is discussed.

Adult↗
PubMed1974

Mechanism of activation of pyruvate dehydrogenase by dichloroacetate and other halogenated carboxylic acids.

1. Monochloroacetate, dichloroacetate, trichloroacetate, difluoroacetate, 2-chloropropionate, 2,2'-dichloropropionate and 3-chloropropionate were inhibitors of pig heart pyruvate dehydrogenase kinase. Dichloroacetate was also shown to inhibit rat heart pyruvate dehydrogenase kinase. The inhibition was mainly non-competitive with respect to ATP. The concentration required for 50% inhibition was approx. 100mum for the three chloroacetates, difluoroacetate and 2-chloropropionate and 2,2'-dichloropropionate. Dichloroacetamide was not inhibitory. 2. Dichloroacetate had no significant effect on the activity of pyruvate dehydrogenase phosphate phosphatase when this was maximally activated by Ca(2+) and Mg(2+). 3. Dichloroacetate did not increase the catalytic activity of purified pig heart pyruvate dehydrogenase. 4. Dichloroacetate, difluoroacetate, 2-chloropropionate and 2,2'-dichloropropionate increased the proportion of the active (dephosphorylated) form of pyruvate dehydrogenase in rat heart mitochondria with 2-oxoglutarate and malate as respiratory substrates. Similar effects of dichloroacetate were shown with kidney and fat-cell mitochondria. Glyoxylate, monochloroacetate and dichloroacetamide were inactive. 5. Dichloroacetate increased the proportion of active pyruvate dehydrogenase in the perfused rat heart, isolated rat diaphragm and rat epididymal fat-pads. Difluoroacetate and dichloroacetamide were also active in the perfused heart, but glyoxylate, monochloroacetate and trichloroacetate were inactive. 6. Injection of dichloroacetate into rats starved overnight led within 60 min to activation of pyruvate dehydrogenase in extracts from heart, psoas muscle, adipose tissue, kidney and liver. The blood concentration of lactate fell within 15 min to reach a minimum after 60 min. The blood concentration of glucose fell after 90 min and reached a minimum after 120 min. There was no significant change in plasma glycerol concentration. 7. In epididymal fatpads dichloroacetate inhibited incorporation of (14)C from [U-(14)C]glucose, [U-(14)C]fructose and from [U-(14)C]lactate into CO(2) and glyceride fatty acid. 8. It is concluded that the inhibition of pyruvate dehydrogenase kinase by dichloroacetate may account for the activation of pyruvate dehydrogenase and pyruvate oxidation which it induces in isolated rat heart and diaphragm muscles, subject to certain assumptions as to the distribution of dichloroacetate across the plasma membrane and the mitochondrial membrane. 9. It is suggested that activation of pyruvate dehydrogenase by dichloroacetate could contribute to its hypoglycaemic effect by interruption of the Cori and alanine cycles. 10. It is suggested that the inhibitory effect of dichloroacetate on fatty acid synthesis in adipose tissue may involve an additional effect or effects of the compound.

Acetamides↗