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Biomedical subjects

M Marais

Publications and source records attributed to M Marais.

8 recordsLinked to original sources
PubMed2001

A study of the litter loadings in urban drainage systems--methodology and objectives.

The recently completed report on "The removal of urban litter from stormwater conduits and streams" (by Armitage et al.) notes that little data is available on the nature and quantity of litter that finds its way into the stormwater drainage systems. The Council for Scientific and Industrial Research (CSIR) estimated in 1991 that 780,000 tonnes of waste a year was entering the drainage systems of South Africa, representing a potential removal cost in excess of two billion rand. There is thus a considerable need for finding ways to reduce litter loadings through better catchment management. Although suggestions have been made as to how this might be achieved, there is very little scientifically verified data from anywhere in the world to show that any of these proposed methods would be effective in South Africa. Only through an improved knowledge of the litter loadings in South African urban drainage systems can appropriate strategies to reduce litter loadings be arrived at. This improved knowledge is one of the twin objectives of the Water Research Commission Project No. K5/1051 entitled "The reduction of urban litter in drainage systems through integrated catchment management." Under this project a three-year monitoring programme has been instituted in nine catchments covering a range of different land uses, socio-economic levels and densities in the Cape Metropolitan Area. This paper focuses on the methodology behind the monitoring programme and the objectives it is hoped to achieve.

Cities↗
PubMed1999

Effects of a prudent diet containing either lean beef and mutton or fish and skinless chicken on the plasma lipoproteins and fatty acid composition of triacylglycerol and cholesteryl ester of hypercholesterolemic subjects.

In this two-phase crossover study, 39 hypercholesterolemic subjects followed a prudent diet with either lean red meat or fish and skinless chicken (treatment groups), and 13 subjects (reference group) followed their habitual diet. Fasting blood samples were analyzed for plasma total cholesterol, triacylglycerol (TAG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein one- and two-cholesterol, apolipoprotein-B, very low density lipoprotein cholesterol, and very low density lipoprotein TAG, and fatty acid composition of plasma TAG and cholesteryl ester (CE). Body mass and blood pressure were determined. Seven-day dietary records were kept once at baseline and twice during the treatment periods. Significant differences were observed in dietary intake between the baseline and treatment diets and between the two treatment diets. HDL-C (P < 0.05) and diastolic blood pressure (P < 0.01) were higher in patients on the red meat diet than in those on the chicken-fish diet. No other significant differences in lipoproteins were observed between the effects of the two treatment diets. The linoleic acid (%), eicosapentaenoic acid (%), and the eicosapentaenoic acid/arachidonic acid ratios in TAG and CE were higher (P < 0.01) in subjects on the chicken-fish diet than in those on the red meat diet. In conclusion, this study showed that the effect of two lipid-lowering diets containing either lean red meat or skinless chicken and fish on the atherogenic lipoproteins did not differ significantly. A prudent diet with skinless chicken and fish, however, had a more favorable effect on the fatty acid composition of the plasma TAG and the CE than did the lean red meat diet.

Journal Article↗
PubMed1998

Plasma and red blood cell total phospholipid fatty acid status of nonpregnant female Vervet monkeys (Cercopithecus aethiops) on a high carbohydrate maintenance diet.

Nonhuman primates are of interest as models of human physiology to study the effect of multiple pregnancies on birth weight. Reference plasma and red blood cell (RBC) total phospholipids fatty acids were established in nonpregnant breeding female Vervet monkeys. Twenty-three clinically healthy nonpregnant Vervet monkeys (Cercopithecus aethiops), contained in a controlled closed environment and consuming a high carbohydrate diet (68 E%) that contained 20 E% fat and 12 E% protein were sampled for blood during a cross-sectional study. A low intake of omega3 fatty acids was reflected by a high omega6/omega3 ratio (66:1) of the diet. Inverse relations were seen between plasma and RBC total phospholipid fatty acids, 18:2omega6, 20:3omega6, and 20:4omega6, which suggested selective incorporation in membranes. Low levels of 20:5omega3 and 22:6omega3 of plasma and RBC total phospholipids render Vervet monkeys as ideal subjects to study the effect of omega3 fatty acid supplementation on pregnancy outcomes.

Animals↗
PubMed1992

Changes in plasma lipoprotein levels during a hiking expedition in South America.

Eleven males participated in a hiking expedition over a period of 6 weeks during which they walked an average of 15 km per day, resting days included. The participants completed a seven-day estimated dietary record before and during the expedition. Their habitual dietary intake before the expedition was typical of a Western diet. During the expedition most animal products, with the exception of canned fish, were excluded from the diet. The dietary intake of fat and carbohydrate changed from 36.9% and 40.6% to 14.0% and 76.4% respectively. Cholesterol intake dropped from 557 mg to 92 mg. Mean plasma total cholesterol (TC) decreased from 190.9 mg/100 ml to 142.0 mg/100 ml. These changes were mainly due to changes in low density lipoprotein cholesterol (LDL-C). Although high density lipoprotein cholesterol (HDL-C) did not change, the ratio of HDL-C to TC increased significantly. It can be concluded that drastic dietary changes, together with increased physical activity and weight loss resulted in major plasma lipoprotein changes. The expected fall in HDL-C due to a high carbohydrate diet was counteracted by the increased physical activity and weight loss.

Adult↗
PubMed1988

Low density lipoprotein kinetics in African Green monkeys showing variable cholesterolaemic responses to diets realistic for westernised people.

African Green (vervet) monkeys were fed either an atherogenic Western diet (WD), a prudent diet (PD), or a high carbohydrate diet (HCD) for various lengths of time. Monkeys differed greatly in their response to the WD, and a strong negative correlation was observed between the fractional catabolic rates (FCR) of low density lipoprotein (LDL) and the total plasma cholesterol concentrations (r = -0.83 P = 0.0029). Similarly the individual synthetic rates (SR) of LDL plotted against the total plasma cholesterol concentrations showed a correlation coefficient of r = 0.94 P = 0.01 for WD animals. There was no correlation for PD or HCD animals for either SR or FCR and the total plasma cholesterol concentrations. The aortic lesion scores correlated with the SRs (r = 0.66 P = 0.040) but not with the FCRs. LDL turnover was also studied using 125I-labelled native LDL and methylated 131I-labelled LDL in African Green monkeys showing high or low cholesterolaemic response to an atherogenic Western diet. Measurements after 4 weeks and again after 6 months on the diet showed a decrease in both total and non-receptor mediated clearance of LDL. Receptor-mediated catabolism was significantly lowered in the hyperresponding group (P = 0.0011) and not in the hyporesponding group with a resultant significant difference between the two groups being P = 0.0355 after 6 months. Non-receptor mediated catabolism of LDL was similarly affected in that there was no significant difference between the two groups at 4 weeks but the clearance of methylated LDL was markedly lowered at 6 months, for the hyporesponding group P = 0.0003 and for the hyperresponding group P = 0.0184. Furthermore the hyperresponding group was depressed to a significantly greater extent when compared to the hyporesponding group (P = 0.0241).

Animals↗