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Biomedical subjects

I R Davies

Publications and source records attributed to I R Davies.

12 recordsLinked to original sources
PubMed2002

Monocyte and neutrophil adhesion molecule expression during acute hyperglycemia and after antioxidant treatment in type 2 diabetes and control patients.

OBJECTIVE: We hypothesized that acute hyperglycemia (an independent cardiovascular risk factor) increases the expression of proatherogenic leukocyte adhesion molecule in type 2 diabetes and controls and that the expression of these adhesion molecules would be antioxidant sensitive. METHODS AND RESULTS: Twenty-three type 2 diabetes patients and 13 control patients underwent two oral glucose tolerance tests 14 days apart and took placebo or 800 IU daily of oral alpha tocopherol between tests. Monocyte and neutrophil expression of adhesion molecules Mac-1, LFA-1 and 3, ICAM-1, and VLA-4 were measured at 0, 120, and 240 minutes by using laser flow cytometry. Baseline adhesion molecule expression did not differ between groups, but there was a rapid, highly significant increase (P<0.0001) in the intensity of monocyte Mac-1 expression after a glucose load in both groups. Alpha-tocopherol supplementation reduced only Mac-1 expression in the diabetes group (P=0.03). CONCLUSIONS: Acute glycemic excursions of any degree cause highly significant, rapid increases in monocyte Mac-1 expression in type 2 diabetes patients and controls. Mac-1 mediates leukocyte vascular infiltration and is prothrombotic. These data suggest a mechanism for the link between glycemic excursions and increased vascular event rates.

Acute Disease↗
PubMed2001

n-3 polyunsaturated fatty acid supplementation, monocyte adhesion molecule expression and pro-inflammatory mediators in Type 2 diabetes mellitus.

AIMS: To examine the effect of n-3 polyunsaturated fatty acid supplements on the monocyte surface expression of adhesion molecules involved in proatherogenic monocyte-endothelial interactions, and on pro-inflammatory mediators in Type 2 diabetes mellitus. METHODS: Twenty-nine subjects with Type 2 diabetes and 21 controls without diabetes were studied. Monocyte expression of leucocyte function-associated antigens 1 and 3, intercellular adhesion molecule-1, and the major histocompatibility complex class II molecule HLA-DR were measured using a laser flow cytometric method. Supplementation with 2.08 g n-3 fatty acids for 21 days was undertaken and measurements repeated. Plasma soluble adhesion molecule concentrations, plasminogen activator inhibitor-1 activity and antigen and pro-inflammatory mediators (cysteinyl leukotriene and monocyte leukotriene B4) were also measured. RESULTS: Groups did not differ in monocyte expression of adhesion molecules or HLA-DR, or in leukotriene production although plasma soluble adhesion molecule concentrations were higher in the diabetes groups (P<0.05). n-3 fatty acid supplementation influenced neither the expression of these molecules nor plasma soluble adhesion molecule concentrations or leukotriene production. CONCLUSIONS: This study does not support increased monocyte adhesion molecule expression or abnormal monocyte production of pro-inflammatory mediators as mechanisms for increased atherogenic risk in Type 2 diabetes. Cardioprotective actions of n-3 fatty acids may not be mediated through these mechanisms.

Blood Platelets↗
PubMed2001

Increased DNA oxidative susceptibility without increased plasma LDL oxidizability in Type II diabetes: effects of alpha-tocopherol supplementation.

In vivo supplementation studies of the antioxidant alpha-tocopherol in human Type II diabetes have used surrogate, rather than direct, markers of oxidative damage/antioxidant protection and have used higher doses of alpha-tocopherol than used in coronary secondary prevention trials. We tested the hypothesis that oral alpha-tocopherol in a dosage regimen used in secondary prevention trials would reduce directly observed oxidatively induced single-strand breaks in lymphocyte DNA in Type II diabetes. We studied 40 people with Type II diabetes and 30 controls in a randomized, double-blind, placebo-controlled trial of 400 i.u. of oral alpha-tocopherol daily for 8 weeks. Lymphocyte DNA single-strand breaks and low-density lipoprotein (LDL) particle size and oxidizability were measured at baseline, after 8 weeks, and after 4 weeks washout. Polymorphisms in the gene for the antioxidant enzyme paraoxonase-1 gene (position 192) were measured. The diabetics had increased DNA oxidative susceptibility (P=0.008), without increased LDL oxidative susceptibility. There was a direct relationship between DNA oxidative susceptibility and baseline plasma alpha-tocopherol in the diabetes group alone (r=0.421, r(2)=0.177 and P=0.023), but DNA and LDL oxidative susceptibility were not influenced by alpha-tocopherol supplementation in either group in this regimen. Paraoxonase-1 gene polymorphisms did not contribute to LDL or DNA oxidative susceptibility or response to alpha-tocopherol. Increased DNA oxidative susceptibility, therefore, can occur in Type II diabetes without increased LDL oxidative susceptibility, but alpha-tocopherol supplementation in this regimen has no influence on DNA or LDL oxidative susceptibility in Type II diabetes or controls. Polymorphisms in the paraoxonase gene (position 192) are not associated with differences in oxidative susceptibility or responses to alpha-tocopherol.

Adult↗
PubMed2000

Perceptual learning of the detection of features in X-ray images: a functional role for improvements in adults' visual sensitivity?

Recent perceptual learning research has found long-term increases in the sensitivity of adults' perceptual systems. The authors examined whether such changes could partly explain improvement on tasks such as perception of medical X-ray images. Experiment 1 found experts' sensitivity to low-contrast dots in X-rays was better than novices'. Experiment 2 found a direction of luminance contrast-specific improvement in novices' detection of low-contrast dots in X-rays as a result of practice. Experiment 3 found a partly specific improvement in novices' detection of low-contrast features in real medical X-rays as a result of practice. Results suggest that experience enhances sensitivity to the critical dimensions of visual analysis for detecting abnormalities in X-ray images. Importantly, they demonstrate a real-world adaptive functional role for the long-term flexibility of sensory systems in adulthood.

Adult↗
PubMed1998

A developmental study of the acquisition of Russian colour terms.

We report a study of the acquisition of colour terms by Russian children which had two main aims: first, to test Berlin & Kay's (1969) theory of colour universals using acquisition order as a measure of basicness; and secondly, to see if the two BLUE terms of Russian are genuinely basic. Two hundred children aged from three to six-years-old were tested on three colour-tasks--colour term listing, colour term production and colour term comprehension. To a reasonable approximation, the order of colour term acquisition was in accord with Berlin & Kay's theory, but the data are also consistent with the weaker claim that primary terms tend to be learned before derived terms. On balance the data were consistent with Russian exceptionally, having an extra term for the BLUE region. But, the two BLUE terms--goluboj 'light blue' and sinij 'dark blue'--were confused more often than other pairs of terms even by the five- to six-year-old sample.

Child Language↗
PubMed1997

A cross-cultural study of colour grouping: evidence for weak linguistic relativity.

We report a cross-cultural study of colour grouping carried out as a test of the Sapir-Whorf hypothesis (linguistic relativity theory). Speakers of English, Russian and Setswana-languages that differ in their number of basic colour terms, and in how the blue-green region is categorized--were compared on a colour sorting task. Informants sorted a representative set of 65 colours into groups so that members of the groups looked similar to each other, with no restriction on the number of groups formed. If linguistic relativity theory is true, then there should be reliable differences between the three samples in the composition of the groups they formed associated with the differing positions of colour category boundaries in the languages. The most striking feature of the results, inconsistent with linguistic relativity theory, was the similarity amongst the patterns of choice of the three samples. However, there were also significant differences amongst the samples. Setswana speakers (who have a single basic term for BLUE or GREEN) were more likely to group BLUE colours with GREEN colours than either English or Russian speakers. But Russian speakers (who have two basic colour terms for BLUE) were no more likely than English speakers to group light and dark BLUE separately. In addition there were general structural differences in grouping among the samples: they differed in the level of consensus in grouping, the number of groups formed and in the distribution of the number of colours placed in a group. These structural differences may reflect differences in the availability and salience of the colour categories across the languages. Our data support perceptual universalism modulated by weaker linguistic effects.

Adult↗
PubMed1994

Tau-mutant hamster SCN clock neurones express a 20 h firing rate rhythm in vitro.

In vitro neurophysiological studies have demonstrated a circadian rhythm with a period of 24 h in spontaneous neuronal discharge frequency within the rodent suprachiasmatic nucleus (SCN) circadian clock. This report examines the 'circadian' firing rate rhythm in the SCN of the homozygous Tau-mutant Syrian hamster which expresses a short period behavioural rhythm. The spontaneous SCN neuronal firing rate patterns are similar to those observed in wild types. The Tau SCN firing rate rhythm displays a peak in neuronal activity occurring 5-6 h before the predicted onset of wheel-running activity, with a peak-to-peak period of 20 h. This period of the rhythm of spontaneous neuronal discharge within the Tau-mutant SCN parallels the behavioural free-running period of 20 h.

Action Potentials↗
PubMed1991

Energy values and energy balance in rats fed on supplements of guar gum or cellulose.

In five experiments where guar gum (GG) or Solka-floc cellulose (SF) supplemented a semi-synthetic diet (100 g/kg) for male Wistar rats at 21 degrees, it was found that GG acutely depressed both ad lib. and meal-fed food intakes by 40-50%. The effect was temporary, with the GG having no effects on food intake in the longer term. Dietary energy balance over 28 d with animals fed on equal amounts of a basal ration showed partial digestible energy values, calculated from the intake and faecal loss of energy, for the supplements which averaged 0 kJ/g SF and 10 kJ/g GG, so that GG contributed substantial amounts of absorbable energy. Despite this additional energy from GG, there was very often no additional gain of body fat. Rather, in some experiments, fat deposition was actually decreased by supplementation with GG. GG is inferred to have a putative thermogenic effect which is often greater than the energy it supplies. This effect occurred to a greater extent in circumstances associated with a higher 'energy status', indicated by higher efficiencies of conversion of gross dietary energy to retained body energy, higher fat:lean tissue deposition ratios and the occurrence of larger deposits at the epididymal fat pad site. There was some evidence that deposition at this site was more extensively affected by GG than deposition of fat in the body as a whole. Possible implications of the present findings are discussed.

Animals↗
PubMed1990

Energy balance and energy values of alpha-amylase (EC 3.2.1.1)-resistant maize and pea (Pisum sativum) starches in the rat.

Apparent and partial digestible energy values for alpha-amylase (EC 3.2.1.1)-resistant, retrograde starches, isolated from cooked maize and pea starches (RMS and RPS respectively), were determined in male Wistar rats (about 180 g) during a 28-29 d balance period with ten animals per treatment. The starches were provided as supplements (100 g/kg diet) to a semi-synthetic basal diet (B), and their effects on the apparent digestibilities of nitrogen and fat, and on gains of live weight, fat and lean tissue were examined. Diet B alone was the control; sucrose (Su) and Solka-floc cellulose (SFC) were also examined for reference. Apparent digestibilities for Su, SFC, RMS and RPS were 1.0, 0.16, 0.98 and 0.89 respectively. Whereas the apparent digestibilities of gross energy, N and fat in the diet were unaffected by supplementation with Su, each was decreased by supplementation with SFC, RMS and RPS. Partial digestible energy values calculated from the intakes and faecal losses of energy in the basal and supplemented diets were 15, 12.4 and 0.8 kJ/g for RMS, RPS and SFC respectively. These values were smaller than corresponding apparent digestible energy values calculated from the apparent digestibility of the supplement and its gross energy value. Only the Su and starch supplements increased the intake of apparent digestible energy and the gain of live weight. Both starches and Su increased total energy (and fat) deposition to almost similar extents. It is concluded that the resistant starches contribute significant dietary energy, enhance growth and elevate fat deposition to extents almost similar to Su.

Animal Feed↗
PubMed1987

Food energy values of dietary fibre components and decreased deposition of body fat.

The effects of guar gum (GG) and solka floc cellulose (SF) on food intake, stomach emptying and body fat deposition in rats were assessed together with their food energy values. Voluntary food intake in meal-fed rats (ca 100 g, male Wistar kept at 21C) was depressed initially by 40 per cent on adding 10 g GG to 100 g fibre free (FF) semisynthetic diet. This effect was not sustained, intake doubling within 15 d. Similar effects were not observed with SF. In pair-fed animals neither GG nor SF affected the rate of stomach emptying after 28 days. Digestible energy (DE) intake per rat over the 28 days was GG diet = 4616, SF diet = 4410, FF diet = 4373 kJ but body fat was lower in GG (25%) and SF (16%) fed rats than in FF fed rats. The calculated DE values of the fibre components were 10.1 kJ/g GG and 1.5 kJ/g SF (sem 1 kJ/g). After including body fat into the equations for metabolizable energy, the energy values were -7.1 kJ/g GG and -4.8 kJ/g SF (sem 2 kJ/g). This is equivalent to an increased energy expenditure of 17.2 kJ/g GG and 6.3 kJ/g SF. For GG an increased intestinal mucosal mass and cell turnover explains part of the apparent increase in energy demand. Our overall conclusion is that under certain circumstances and with regard to fat deposition some fibre components can be attributed negative energy values.

Adipose Tissue↗
PubMedDate not supplied

Digestible energy value of gums in the rat--data on gum arabic.

Male Wistar rats were fed a defined formula diet free from non-starch polysaccharides and either containing no additive or supplemented with gum arabic or cellulose or starch. Food and faeces were analysed by bomb calorimetry both to assess the effect of these substances on the apparent digestibility of dietary gross energy and to ascribe digestible energy values to the supplements. The former was not affected by starch and was decreased more by cellulose than by gum arabic. The energy values obtained were 17.4 +/- 0.4 kJ/g starch, 1.7 +/- 0.6 kJ/g cellulose and 14.7 +/- 0.5 kJ/g gum arabic. The latter is consistent with the high apparent digestibility of gum arabic in vivo and casts doubt on the validity of growth assay procedures that suggest a near-zero energy value for gum arabic.

Animals↗