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Biomedical subjects

A C Beynen

Publications and source records attributed to A C Beynen.

At least 307 records · Page 17Linked to original sources
PubMed1989

Nutrition and kidney calcification in rats.

Nephrocalcinosis is a 'spontaneous' disorder in rats which refers to the deposition of calcium salts in the kidney, preferably in the cortico-medullary region. Studies using defined, semi-purified diets have shown that low dietary concentrations of magnesium, high concentrations of calcium, high concentrations of phosphorus and low calcium: phosphorus ratios induce kidney calcification. Dietary phosphorus induced nephrocalcinosis in female rats is associated with increased kidney size and weight, tubular hyperplasia, fibrosis and increased excretion of albumin in urine. This suggests that nephrocalcinosis may impair kidney function. In rats fed different commercial diets the incidence of nephrocalcinosis can vary considerably. Differences in the degree of nephrocalcinosis in different experiments may negatively influence the comparability of experimental outcome, especially when this is affected by kidney function and structure. Experimental data are needed so that diets can be formulated that do not produce nephrocalcinosis without inducing other disorders.

Animal Nutritional Physiological Phenomena↗
PubMed1989

Objective clinical examination of poultry as illustrated by the comparison of chickens with different vitamin A status.

One day old pullets derived from marginally vitamin A deficient laying hens were fed diets containing either adequate or marginal amounts of vitamin A. At the age of 34 days, animals fed the diet low in vitamin A had group mean plasma concentrations of retinol which were one tenth the mean plasma concentrations of controls. When compared with their controls, the deficient animals displayed body weights which were on average 16% less. Of 20 pullets per dietary group one control animal and 9 deficient animals died by the age of 34 days. At the age of 29 days, control (n = 16) and deficient chickens (n = 11) were examined clinically by assigning scores to a number of parameters. Three assessors carried out the examination independently. The birds were presented for examination at random and their treatment groups were not disclosed to the assessors. Out of 26 parameters assessed quantitatively per individual animal, only three parameters discriminated between control and deficient chickens. Deficient animals grew poorly, had a hunched up posture and increased fluid content in faeces. Classical signs of chronic vitamin A deficiency in domestic fowl such as bone deformities, keratinization of the tongue and decreased transparency of the cornea were not observed.

Animals↗
PubMed1989

Clinical examination of weanling rats with early zinc deficiency.

In order to gain experience about the detection of adverse effects during a scientific procedure, we carried out a clinical examination of rats with zinc deficiency. In weanling rats fed a zinc-deficient diet (30 mumol zinc/kg) for 10 days, the mean tibial concentration of zinc was reduced by 53% and body weight gain by 73% when compared with rats fed a diet containing an adequate amount of zinc (150 mumol zinc/kg). In a small open field on day 9 of the experiment, the deficient rats more frequently displayed the posture standing upright with elevated heels. On day 10 of the experiment a clinical examination was carried out at random and 'blind' by three independent assessors. Out of 20 variables scored quantitatively on each individual animal, only body size differed between normal and deficient rats. Other classical signs of zinc deficiency, such as alopecia, dermatitis and diarrhoea, were not detected. It is concluded that in this rat model of zinc deficiency, no evidence for extreme discomfort can be demonstrated.

Animals↗
PubMed1989

Influence of dietary phosphorus restriction on calcium and phosphorus metabolism in rats.

The effect of dietary phosphorus (P) on calcium (Ca) and phosphorus metabolism was studied in young female rats. P levels in the semipurified diets ranged from 0.1 to 0.4% (w/w). A level of 0.4% P in the diet is recommended for rats. Kidney calcification was observed in rats fed the 0.4%-P diet whereas P restriction prevented this condition. Rats fed the diet containing 0.1% P, showed severe hypercalciuria, hypercalcemia, reduced growth and impaired bone mineralization. These effects did not occur when the diet contained 0.2 or 0.3% of P. This study suggests that in short-term studies P in the diet of female rats can be restricted to 0.2% so as to prevent nephrocalcinosis without affecting their development.

Animals↗
PubMed1989

Liver cholesterol concentrations in mice fed diets containing various sources of fat, carbohydrates or fiber.

Liver cholesterol concentrations were measured in mice after feeding for 30 days cholesterol-free, semipurified diets containing various sources of fat, carbohydrates or fiber. Olive oil produced significantly higher liver cholesterol concentrations than tallow, sunflowerseed oil and cocoa fat. In mice fed either fructose or sucrose liver cholesterol was significantly increased when compared with mice fed galactose or lactose. Dietary cellulose, when compared with pectin, did not influence liver cholesterol. The amount of fat in the diet, in the form of either corn oil or coconut fat, had no significant effect on liver cholesterol. It is concluded that the type of carbohydrate and fat in the diet are major determinants of liver cholesterol in mice.

Animals↗
PubMed1989

Responsiveness to dietary cholesterol in the domestic fowl is not related to the degree of body fatness.

The hypothesis that chickens of a lean rather than a fat line are hyperresponsive to dietary cholesterol was tested. Birds of the fat line showed higher initial plasma total cholesterol levels. The addition of 1% (w/w) of cholesterol to the diet significantly increased plasma cholesterol concentrations but there was no difference in response between the two lines. Dietary cholesterol increased liver cholesterol in both lines, the effect being more pronounced in birds of the lean line. It is concluded that the responsiveness of plasma cholesterol to dietary cholesterol in chickens is not related to the degree of body fatness.

Adipose Tissue↗
PubMed1989

Transportation of rats affects behaviour of non-transported rats in the absence of physical contact (preliminary communication).

We have studied the effect of transportation stress in one rat on the behaviour of another, non-transported rat in the absence of physical contact. For this purpose an open box consisting of two adjacent small fields was used. Rats were placed in these fields and their behaviour was assessed. The control measurement involved pairs of non-transported rats and the experimental pairs consisted of a transported and a non-transported rat. The non-transported rats of the experimental pairs displayed significantly increased activities of sniffing when compared with the non-transported rats of the control pairs. It is suggested that stressed animals can influence the behaviour of nearby animals.

Animals↗
PubMed1989

Hardness of diet pellets and growth of pre-weaned mice: separation of direct effects on the young and indirect effects mediated by the lactating females.

The effect of pellet hardness on growth of pre-weaned mice was studied with the use of a specially constructed cage so that lactating females and their young could be fed separately. Diet pellets with identical ingredient composition but hardness of either 20 or 40 kp were prepared. Growth of the young not supplemented with feed was markedly depressed by the feeding of the 40-kp diet to the mothers, when compared with the 20-kp diet. If the young of mothers fed the 40-kp diet had free access to diet pellets with hardness of either 20 or 40 kp, their growth performance improved. When the breeding females were fed the 20-kp diet, feed supplementation of the young did not affect their body weight. This study suggests that the observed effect of diet pellet hardness on body weight of pre-weaned mice is mediated in part through the mothers. Free access to feed was found to stimulate growth of pre-weaned mice only if the mothers were fed extremely hard diet pellets.

Animal Feed↗
PubMed1989

Identification and clinical examination of jaundiced rats.

Rats with or without spontaneously occurring jaundice were clinically examined. Jaundiced rats had five-fold higher serum bilirubin concentrations than control animals. About 90% of serum bilirubin in the jaundiced animals was in conjugated form. Control and jaundiced rats did not differ with respect to clinical signs such as alertness, stance, hair coat, position of eyes, discharge from eyes and nose, and cleanliness of anal orifice. While examined individually, jaundiced rats could not be identified readily on the basis of a yellow colour of sole of feet, nose, ears and tail. When kept together with control rats, jaundiced rats could be selected reasonably well. Urines of jaundiced rats had a more intense yellow colour than urines of control animals. Rats with jaundice were significantly more active in a small open field test than control rats.

Animals↗
PubMed1989

Dietary animal proteins and cholesterol metabolism in rats.

The effects on cholesterol metabolism in rats of diets containing various animal proteins or soy protein were studied. The animal proteins tested were casein, whey protein, fish protein, hemoglobin, plasma proteins, ovalbumin, egg-yolk protein, beef protein and chicken-meat protein. The semi-purified diets were isonitrogenous and balanced for residual fat and cholesterol in the protein preparations. The nature of the dietary protein had no effect on serum cholesterol concentration. Group mean liver cholesterol concentration was increased and fecal excretion of bile acids was decreased by all animal proteins when compared with soy protein. This study suggests that carefully balancing diets for components other than protein in the protein preparations prevents protein effects on serum cholesterol in rats but not on liver cholesterol and bile acid excretion.

Animals↗
PubMed1989

Hardness of diet pellets and its influence on growth of pre-weaned and weaned mice.

The hardness of 3 commercial diet pellets for laboratory rats and mice was studied. Hardness was measured as the force (kp) required to crush a diet pellet. Between-batch variation, expressed as coefficient of variation, ranged between 12 and 70%. In one type of diet hardness of the pellets varied between 4 and 50 kp. Hardness did not change during storage for a period of 8 weeks. To investigate the effect of hardness on growth performance of young mice experimental diets were prepared with identical ingredient composition but with hardness of either 15 or 45 kp. Female mice provided with hard pellets (45 kp) were not able to raise their litters. Feeding the experimental diet as 15 kp pellets resulted in a slightly retarded growth when compared with the experimental diet in the form of meal. Weaned mice were fed with the experimental diet in 4 different forms: meal, 15 kp, 45-kp and ground 45-kp pellets. Male mice, unlike females, fed the 45-kp diet grew slower than their counterparts fed the other diet forms. It is concluded that batches of extremely hard pellets may be occasionally delivered, and that such diets have undesirable effects on performance of young mice.

Animal Feed↗
PubMed1989

Lipid and carbohydrate metabolism in cholestyramine-fed rats.

In rats fed semipurified diets, increasing amounts of dietary cholestyramine counteracted the effects of dietary cholesterol on plasma and liver cholesterol concentrations. These effects were associated with increasing rates of fecal bile acid excretion. Cholestyramine caused an increase in plasma triglyceride concentrations, and increased the ratio of triglycerides to cholesterol in plasma. The anion resin did not influence plasma glucose concentrations and blood concentration of acetoacetate, beta-hydroxybutyrate and lactate. Thus cholestyramine specifically affects cholesterol metabolism and plasma triglyceride concentrations without influencing other metabolites of fatty acid and carbohydrate metabolism.

Animals↗
PubMed1988

Influence of dietary carnitine on lipid and carbohydrate metabolism in rats.

Dietary saturated fatty acids, when compared with polyunsaturated fatty acids, increase plasma triglyceride and cholesterol concentrations, possibly because saturated fatty acids are preferentially converted into triglycerides. Carnitine is known to stimulate the oxidation of fatty acids and the formation of ketone bodies, and thus divert fatty acids from the pathway of esterification and triglyceride synthesis. In rats fed semipurified diets, we tested the hypothesis that carnitine counteracts the increase in plasma cholesterol and triglycerides seen after the feeding of saturated fatty acids. Indeed, saturated fatty acids in the form of coconut fat were found to increase plasma triglyceride and cholesterol concentrations when compared with polyunsaturated fatty acids fed as corn oil. The addition of carnitine to the diet (1%, w/w) did not affect this differential fat effect. Thus the hypothesis would be disproved. However, it cannot be excluded that the experimental conditions were improper, so as to demonstrate an interaction between dietary carnitine and saturated fatty acids: dietary carnitine per se did not influence the blood concentration of ketone bodies.

3-Hydroxybutyric Acid↗
PubMed1988

Comparison of rats with mice concerning the response of lipid metabolism to dietary fats.

Rats and mice were compared regarding their responses to cholesterol-free or high-cholesterol diets containing either corn oil or coconut fat. In rats fed a cholesterol-free diet, but not in the mice, corn oil caused an increase in serum and liver cholesterol when compared with coconut fat. Corn oil reduced serum triglycerides and increased fecal excretion of neutral steroids in the rats, whereas these variables were not affected in the mice. Fecal bile acid excretion was reduced in mice but not altered in rats. When the diets contained 1% (w/w) of cholesterol, the rats and mice responded rather similar to corn oil. This study suggests that the response to dietary fats can be species-dependent in some respects.

Animals↗
PubMed1988

Influence of dietary calcium:phosphorus ratio on mineral excretion and nephrocalcinosis in female rats.

The effects of dietary calcium (Ca) concentration and calcium: phosphorus (Ca:P) ratio on mineral balance and nephrocalcinosis were studied in female rats. In the first experiment there were two dietary Ca concentrations (0.25 and 0.50%, wt/wt) at two different Ca:P ratios (0.6 and 1.3). In the second experiment the diets were formulated to contain 0.40% P and either 0.13, 0.25, 0.50 or 0.75% Ca. The diets contained 0.03% magnesium (Mg). The fecal outputs of Ca, P and Mg were lower (P less than 0.01) after feeding low Ca diets than after feeding high Ca diets. Urinary excretion of P decreased with increasing dietary Ca and increased with increasing P intake. In rats fed the 0.25% Ca diets whole-body retentions of Ca and P were lower than in the rats fed 0.50% Ca. Both increases in dietary Ca from 0.13 to 0.50% and P from 0.20 to 0.40% elevated Ca and P content of kidneys as well as the degree of nephrocalcinosis. However, after feeding the highest Ca concentration (0.75%) nephrocalcinosis was essentially absent while kidney concentrations of Ca and P were relatively low. When compared with 0.50% Ca in the diet, 0.75% Ca increased group mean whole-body retention of Ca but lowered that of P. In individual rats the degree of nephrocalcinosis and the concentrations of minerals in kidney were positively correlated.

Animals↗