Biomedical subjects

M van Schaik

Publications and source records attributed to M van Schaik.

4 recordsLinked to original sources

PubMed1990

Relationship between the calcium-to-protein ratio in milk and the urinary calcium excretion in healthy adults--a controlled crossover study.

Over the years, doubts have arisen concerning the use of milk as a calcium source in the prevention of osteoporosis, particularly because of potential offsetting effects of protein and phosphorus. Thus, a new milk product with a higher calcium content and lower contents of protein, phosphorus, and energy was developed. A controlled crossover study was done to determine the way in which substitution of the new milk product (860 mL) for normal milk (1000 mL) in the diet of healthy adults affected the urinary excretion of calcium and hydroxyproline. Short-term consumption of the product significantly lowered 24-h urinary calcium excretion by approximately 0.65 +/- 0.19 mmol/d (means +/- SEM, p less than 0.001). The ratio of fasting urinary hydroxyproline to creatinine did not decrease, indicating no significant reduction of bone resorption in our subjects. Elderly people in particular might benefit from the new product because it reduces their calcium loss as well as their intake of protein, phosphorus, energy, and liquid volume.

Adult↗

PubMed1990

Milk: does it affect blood pressure? A controlled intervention study.

In a double-blind trial, the effect on blood pressure of supplementation of normal milk (1180 mg Ca2+, 1650 mg K+ and 110 mg Mg2+ d-1) vs. 'mineral-poor' milk (95 mg Ca2+, 580 mg K+ and 10 mg Mg2+ d-1) was studied. Young healthy normotensive female students consumed one of the two supplements while on a low calcium diet (less than 500 mg Ca2+ d-1) for a period of 6 weeks. In both the normal milk- and 'mineral-poor' milk-supplemented groups systolic blood pressure decreased slightly. However, this decrease was persistently greater in the milk-supplemented group. The individual mean systolic blood pressure change during normal milk treatment (-4.1%) was significantly greater (P = 0.03) than that during 'mineral-poor' milk treatment (-1.3%). An effect of normal milk supplementation on diastolic blood pressure could not be demonstrated. The results of the present study indicate a small hypotensive effect of milk consumption, which is attributable to its content of essential minerals.

Adult↗

PubMed1989

Reconstitution of an endosome-lysosome interaction in a cell-free system.

A cell-free model for the transfer of endocytosed material to lysosomes is described. Rat liver late endosomes, loaded in vivo with radiolabeled ligand by intravenous injection shortly before killing the animal, showed a specific interaction with lysosomes when incubated at 37 degrees C in the presence of cytosol and an ATP regenerating system. The location of the ligand, generally asialofetuin, was analyzed by isopycnic centrifugation on Nycodenz gradients. Appearance of radiolabel in the lysosomal position on such gradients was maximal after approximately 30 min at 37 degrees C and required the provision of undamaged cytosol, lysosomes, and an ATP regenerating system. It could not be accounted for by nonspecific bulk aggregation of membranes. Transfer occurred only from late endosomes; radiolabel in early endosomes was unaffected. Digestion of the asialofetuin, as shown by the appearance of TCA-soluble radioactivity, occurred on incubation at 37 degrees C and was increased by the provision of an ATP regenerating system.

Animals↗

PubMed1979

Effect of bran and cellulose on lipid metabolism in obese female Zucker rats.

The effects on lipid metabolism of bran and cellulose added to a low-cholesterol purified diet were studied in female obese Zucker rats. The obese Zucker rat was chosen for the experiment because of its sensitivity to dietary changes with regard to lipid metabolism. Cellulos, as well as bran, had an effect on lipid metabolism, which is expressed as an increase in the excretion of fecal bile acid and cholesterol and, in the case of bran feeding, as a decrease in liver cholesterol level and an increase of fecal fat excretion. The increased excretion rate of cholesterol and bile acids did not result in a reduction of the plasma cholesterol levels, which suggests a compensatory mechanism in the form of either an increase of hepatic cholesterol synthesis and/or changes within the body cholesterol pools. The increased excretion of fecal fat that occurred when bran was added to the diet, is not likely to influence cholesterol metabolism, since fecal fat excretion only appeared to form a small percentage of the total fat intake. Bran as well as cellulose caused a significant increase in fecal wet weight and a decrease in transit time. Though both cellulose and bran are capable of binding bile acid, cholesterol and/or fat, the intestinal transit time and the fecal bulk might also be a cause of increased steroid excretion. The fact that our results are inconsistent with those of some investigations described in the literature but in agreement with the findings of other workers, again stresses the primary need for a better chemical characterization of the various fiber sources.

Animals↗