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Biomedical subjects

D Hewitt

Publications and source records attributed to D Hewitt.

At least 37 records · Page 2Linked to original sources
PubMed1988

Blood lead and blood pressure: analysis of cross-sectional and longitudinal data from Canada.

Analysis of data collected during the Canada Health Survey of 1978-1979 indicated a positive relationship between blood lead and blood pressure, but so weak that the range of lead-related variation among members of the general public was estimated to be at most 3.0 mm Hg of diastolic pressure. Even so, a blood lead level in excess of the median value of 10 micrograms/dL entailed a 37% higher risk of having diastolic pressure above 90 mm Hg. In a longitudinal study of lead foundry workers, an association was found between short-term changes in an individual's blood lead level and contemporary changes in diastolic pressure; this remained significant after allowance for age (or time) trends and for effects attributable to changes in body weight. Short-term changes in urinary cadmium levels were similarly predictive of diastolic pressure.

Adult↗
PubMed1986

Effect of maternal dietary exclusion on breast fed infants with eczema: two controlled studies.

Thirty seven breast fed infants with eczema were studied to see whether changes in their mothers' diets affected their skin condition. Nineteen mothers and babies took part in a double blind crossover trial of exclusion of egg and cows' milk, and 18 took part in open exclusion of 11 foods followed by double blind challenge to those mothers whose infants seemed to respond. Babies were examined at the beginning and end of each dietary period, and the extent and severity of the rash were given a numerical score. The eczema improved in six infants when their mothers avoided egg and cows' milk and worsened again when these were reintroduced. Two infants suffered gastrointestinal reactions after maternal ingestion of egg and cows' milk, one developing colitis. Maternal dietary exclusion seems to benefit some breast fed babies with eczema.

Animals↗
PubMed1986

Exchanges of water and certain water-soluble minerals during passage of digesta through the stomach compartments of young ruminating bovines.

1. Four ruminating bull calves were provided with cannulas in the rumen and abomasum and a sleeve sutured at the omosal-abomasal orifice that permitted digesta flowing from the omasum to be diverted and collected. 2. The calves were each given in turn a high-roughage (HR) and high-concentrate (HC) diet consisting mainly of dried grass and flaked maize in the proportions 3:2 and 1:2 by weight respectively. Water-soluble non-absorbable marker (polyethylene glycol) was also given and the diets were sometimes supplemented with magnesium sulphate. For each diet (HR(0), HR(Mg), HC(0), HC(Mg], collections were made from the rumen, reticulum, omasal outflow and abomasum, and flows of water, sodium, potassium and chloride calculated at these sites relative to intakes. 3. The general pattern of net exchange was similar for all the diets. Substantial additions of water and Na, a small addition of K and a small absorption of Cl occurred between mouth and reticulum. Substantial (approximately 40-60%) absorption of water and Na, a small absorption of K and considerable secretion of Cl occurred in the omasum. Quantitative comparisons indicated that addition of water and Na up to the reticulum, presumably in saliva, was significantly greater for the HR than the HC diets. Addition of Mg appeared to stimulate absorption of Na and water up to the reticulum for unknown reasons. Re-absorption of these components in the omasum varied for different calves and diets but appeared to be influenced primarily by a positive linear relation between amounts of digesta flowing into the omasum and amounts of water and Na absorbed from it. The proportion of water absorbed also increased with increasing entry rates of water. 4. Other findings showed that pH values rose slightly (about 0.2 pH units) but significantly in the reticulum compared with the rumen and that the value fell again by about the same amount during the passage of digesta through the omasum. Changes between omasal outflow and the abomasum were as expected, with marked additions of Cl, Na and water and a fall in pH.

Abomasum↗
PubMed1985

Magnesium and certain other elements and cardiovascular disease.

Cardiovascular disease (CVD) continues to be the major cause of mortality in developed countries. For the past two-and-a-half decades the inverse relationship between water hardness and CVD mortality has stimulated interest among epidemiologists, clinicians and experimental researchers. Much progress has been made in elucidating which element in the water may account for this situation. After reviewing those elements found to have a role in cardiovascular function the authors present the epidemiological evidence and its consistency with recent findings: aside from various trace elements emphasis is placed on magnesium which is recognized as having a vital role.

Adult↗
PubMed1985

Nutritional value of yogurt.

Yogurt, made from fortified skim milk by conventional methods using Streptococcus thermophilus and Lactobacillus bulgaricus, was used in studies of the effect of fermentation on nutritional value of milk. In all experiments, the product was compared with the uninoculated base milk. The concentration of most vitamins was less in yogurt than in milk and was most noticeably so for biotin which was 60% less. The effect on folic acid content was inconsistent. In nutritional experiments with rats, high values for true digestibility, biological value and net protein utilization were obtained for both yogurt and its base milk, only minor differences being apparent between the two materials. In growth tests with rats, yogurt was not found to be consistently superior to the base milk when the milk was subjected to a double heat treatment to reduce bacterial contamination. Yogurt did not confer a nutritional advantage on fresh milk in this respect.

Animals↗
PubMed1985

Nutritional availability of methionine, lysine and tryptophan in fish meals, as assessed with biological, microbiological and dye-binding assay procedures.

In vitro assay procedures were applied in the measurement of available amino acids in a selection of fish meals representing good- and poor-quality product. Results were assessed by comparing them with results from chick-growth assays. Available methionine and tryptophan were assayed microbiologically with Streptococcus zymogenes, after predigestion of the test samples with papain or pronase. Results for methionine were correlated with chick-growth assays (r 0.86 for papain, 0.91 for pronase; P less than 0.01). Compared with the chick assays, papain tended to give lower, and pronase higher, results. Finer milling of the test samples did not influence the pronase values. Results for available tryptophan were also correlated with chick-growth assays (r 0.95 for papain, 0.96 for pronase; P less than 0.001). Compared with the chick values, papain gave markedly lower results and pronase marginally higher ones. Finer milling of the test samples increased the papain values by about 50% but had no effect with pronase. Available lysine was assayed microbiologically with Tetrahymena pyriformis and with a dye-binding procedure (DBL). The results correlated with the chick-growth assays (r 0.99 for DBL, P less than 0.001; 0.85 for Tetrahymena, P less than 0.01) but both methods overrated the poorer-quality samples. True nitrogen digestibilities and amino acid digestibilities were determined with chickens by the 'ileal analysis' procedure: the amino acid digestibilities were significantly higher and similar to the corresponding availabilities as measured in chick-growth assays. Ball milling a poor-quality fish meal caused a marked fall in its N digestibility, whereas similar treatment of a good-quality meal caused a slight increase. An explanation for this finding is proposed. Strep. zymogenes assays following pronase digestion of the test samples gave precise and acceptably accurate measures of the biologically available methionine and tryptophan in the test samples. For available lysine, Tetrahymena and DBL values for the poorer-quality samples were notably higher than the chick-growth assay; possible reasons for this are discussed. The ileal analysis procedure underestimated true N digestibility.

Animals↗
PubMed1984

The Collaborative Lipid Research Clinics Program Family Study: detection of major genes influencing lipid levels by examination of heterogeneity of familial variances.

Age, sex-adjusted, and transformed lipid and lipoprotein data on over 1,200 white North American sibships in the Collaborative Lipid Research Clinics Family Study were analyzed for possible major genes causing high or low levels of these traits. The sibships were stratified on the basis of parents' trait values, and within-sibship variance in the high (or low) families was compared to that in the normal families via an F-test. The null hypothesis of multifactorial transmission was strongly rejected for low LDL, low total cholesterol, and high HDL families. An analysis of spouse-pair variance gave similar results. This may reflect the presence of dominant genes for hyperalpha- and hypobetalipoproteinemia. There was weaker evidence for single genes causing hyperbetalipoproteinemia. There was no evidence for major genes influencing triglyceride levels. Methodological issues with significant bearing on these results and those of other studies are discussed.

Biometry↗
PubMed1984

The effect of yoghurt on some components of the gut microflora and on the metabolism of lactose in the rat.

Feeding yoghurt or base milk (from which the yoghurt was prepared by fermentation) to rats increased the counts of coliforms in the gut whereas the counts of lactobacilli were reduced by yoghurt but not by the base milk. Lactobacillus bulgaricus survived in the guts of gnotobiotic and conventional rats when yoghurt was fed continuously. Streptococcus thermophilus also survived in gnotobiotic rats but its ability to survive in conventional rats could not be examined. Both organisms failed to colonise the gut when a small inoculum of yoghurt was administered orally to germfree rats maintained on the stock diet. Streptococcus thermophilus but not Lact. bulgaricus grew in the rat diet when tested in vitro. Two enzyme systems (beta-galactosidase and lactase) were studied using, respectively, o-nitrophenyl-beta-D-galactopyranoside (ONPG) and lactose as the test substrates. Enzyme levels estimated with both substrates increased in the gut contents when rats were fed yoghurt but an increase was only found with ONPG in the intestinal mucosa fraction. The bacterial origin of all this increased activity is discussed. The other lactose-containing diets did not affect enzyme activity to the same degree. Feeding yoghurt changed the lactobacillus flora from one which was predominantly heterofermentative (Lact. reuteri ) to one which was predominantly homofermentative (Lact. salivarius).

Animals↗
PubMed1983

The influence of the gut microflora on protein synthesis in liver and jejunal mucosa in chicks.

Protein synthesis in liver and jejunal mucosa was measured in 19-d-old germ-free (GF) and conventional (CV) chicks fed on a semi-purified casein-gelatin (SCG) diet using a massive-dose single injection of [U-14C]phenylalanine. The effect of subsequent feeding for 9 d either a nitrogen-free (NF) diet or an NF diet supplemented with L-methionine (5 g/kg) and L-arginine hydrochloride (2 g/kg) (MA diet) was investigated in both types of chick. In the liver, apart from the amount of DNA, the values for wet weight, protein, RNA, fractional synthesis rate (FSR) and the amount of protein synthesized were reduced after feeding the NF diet and, to a lesser extent, the MA diet. Except that the total amount of liver DNA was higher in the CV chicks than in their GF counterparts (P less than 0.01), no environmental effect was significant. When expressed on a unit body-weight basis, liver weight, protein, RNA and DNA were significantly higher in the CV than in the GF chicks. In the jejunal mucosa, the values for wet weight, protein and RNA tended to be reduced after the NF treatment but increased after the MA treatment. Mucosal DNA and the amount of protein synthesized (microgram/mm per d) were significantly reduced after the NF diet but were less affected after the MA diet. Mucosal protein FSR and the amount of protein synthesized per mg RNA were significantly reduced after both dietary treatments. No difference was found among dietary treatments in the amount of protein synthesized per mg DNA in jejunal mucosa. Mucosal DNA was significantly higher in the CV chicks and the reverse was true for mucosal protein: DNA. It was suggested that the increased protein synthesis in jejunal mucosa and possibly in liver on supplementation of an NF diet with methionine and arginine would partly, if not completely, account for the N-sparing effect of these amino acids. Although the protein: DNA value was smaller in CV chicks, the FSR and the amount of protein synthesized tended to be higher than in their GF counterparts irrespective of nutritional status. This might imply that protein degradation rate is greater in the CV state.

Animals↗
PubMed1983

Factors affecting the capture of dietary nitrogen by micro-organisms in the forestomachs of the young steer. Experiments with [15N]urea.

For a period of at least 2 weeks before an experimental collection each of four young steers received total daily intakes consisting of approximately (g/kg) 600 straw and 400 concentrates with the nitrogen provided mainly as urea and in which the main energy source was starch (tapioca) for diet 1 and glucose for diet 2. Concentrates were given twice daily at about 09.00 and 17.00 hours, straw at 17.00 hours only. The value for the ratio, rumen-degradable N: metabolisable energy (g/MJ) in the daily intake was estimated to be approximately 1.2. On the day that an experimental collection was to be made the urea normally given in the feed at 09.00 hours was labelled with 15N. This urea and sometimes the appropriate energy source were added either as a single dose (SD) at 09.00 hours or in three equally-divided doses (DD) at 09.00, 11.00 and 13.00 hours. Treatments, given in a Latin-square design, were: (A), starch (SD) + urea (SD); (B), starch (SD) + urea (DD); (C), glucose (SD) + urea (DD); (D), glucose (DD) + urea (DD). Doses of polyethylene glycol (PEG) and 144Ce (as cerous chloride) were given as markers with the urea. After these doses were given, samples of abomasal and duodenal digesta were taken periodically for 72 h. It appeared that virtually all the PEG had left the rumen by this time and mean recovery of 144Ce relative to PEG was approximately 90%. From recoveries of non-ammonia-15N (microbial 15N) at the abomasum, estimated relative to PEG, values for mean fractional efficiencies of conversion of urea-N to microbial-N were calculated to be 0.59, 0.59, 0.40 and 0.41 for treatments A, B, C and D respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Abomasum↗
PubMed1982

The inheritance of sinking-pre-beta lipoprotein and its relation to the Lp(a) antigen.

We have investigated the genetics of plasma sinking-pre-beta lipoprotein (sp beta) as determined by the method of Breckenridge and Maguire, using several approaches: (i) a population study, (ii) a twin study and (iii) the use of family data. In addition, by the use of split samples, the sp beta level as determined by us was correlated with Lp(a) typing carried out in Oslo by Dr. Kåre Berg. Although the sp beta level is a continuous character, the results clearly showed it to be to a considerable extent under the control of the major autosomal gene pair constituted by the alleles Lpa and Lp, which mainly control the production of the Lp(a) antigen, Lpa being dominant. In our data the boundary between the LpLp and LpaLp genotypes appeared to fall between the sp beta 2 and 3 mg% levels, while that between LpaLp and LpaLpa was in the 15 mg% region. These boundaries, which were inferred from both typing and population statistics, received good confirmation from the family data. It appears that some 88% of the variation in sp beta level is directly ascribed to segregation of Lpa and Lp. On the basis of the twin study and other data, we conclude that the residual observed variation in sp beta is almost entirely ascribed to analytical error of determination and polygenic effects, the influence of environment being negligible. The heritability is close to 100%.

Antigens↗
PubMed1980

Plasma lipoprotein levels and the prevalence of hyperlipoproteinemia in a Canadian working population.

The lipids and lipoproteins - cholesterol (C), triglyceride (TG) and high-density, low-density, very-low-density and sinking pre-beta-lipoprotein cholesterol (HDL-C, LDL-C, VLDL-C and SPB-C) - in plasma samples from 1620 fasting white adults and children from the Toronto-Hamilton area were analysed. The mean concentration of HDL-C was about 45 mg/dl in men and about 60 mg/dl in women, and the levels were constant throughout adult life in both sexes. Boys had higher mean HDL-C levels than men, but girls had lower mean HDL-C levels than women. Mean LDL-C levels, like total C levels, increased with age, from about 87 mg/dl in boys to 136 mg/dl in men, and from about 91 mg/dl in girls to 145 mg/dl in women. The mean levels of VLDL-C followed the TG patterns for age and sex, rising from about 7 mg/dl in boys to 26 mg/dl in men, and from about 11 mg/dl in girls to 19 mg/dl in women. SPB-C was detectable visually in 39% of the population and with the aid of densitometry in 54%; the levels were not related to age, sex or oral contraceptive use, and the median level was 3 mg/dl.Prevalence estimates of hyperlipoproteinemia showed that type IV was the most common, and it was found more than three times as often in men as in women. This was in part due to the customary use of plasma TG cut-off points that do not reflect the large difference in TG levels between males and females. Type IIA hyperlipoproteinemia was found in about 2% of the adults and type IIb in a further 1%. Types I, III and V were all rare. The prevalence of types II and IV hyperlipoproteinemia was four times greater in women using oral contraceptives than in nonusers in the same age range.

Adolescent↗