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A C Beynen

Publications and source records attributed to A C Beynen.

At least 217 records · Page 12Linked to original sources
PubMed1993

High protein intake raises apparent but not true magnesium absorption in rats.

Earlier studies with rats have shown that greater protein intake raises apparent magnesium absorption (ingested magnesium minus fecal magnesium). We addressed the question of whether high protein intake affects true magnesium absorption. Rats were fed either a normal (175 g casein/kg) or a high (525 g casein/kg) protein diet. Extra protein was added at the expense of the glucose component of the diet; the diets were balanced for magnesium, calcium and phosphorus. The high protein diet enhanced apparent magnesium absorption. True magnesium absorption, as measured with the use of oral and intraperitoneal administration of tracer doses of 28Mg, was found to be unaffected by high protein intake. Endogenous magnesium excretion in feces was significantly depressed in rats fed the high protein diet, which was associated with elevated urinary magnesium excretion. High protein intake reduced the amount of magnesium in whole ileal digesta but raised the amount and concentration of magnesium in the liquid phase. We conclude that improvement of apparent magnesium absorption in rats fed high protein diets is due to depressed fecal excretion of endogenous magnesium.

Animals↗
PubMed1993

Dietary cholesterol-induced down-regulation of intestinal 3-hydroxy-3-methylglutaryl coenzyme A reductase activity is diminished in rabbits with hyperresponse of serum cholesterol to dietary cholesterol.

Key enzymes of cholesterol metabolism were studied in two inbred strains of rabbits with hyper- or hyporesponse of serum cholesterol to dietary cholesterol. Baseline 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase activity in liver was similar in hypo- and hyperresponders, but that in intestine was twofold higher in the hyporesponders. The addition of cholesterol (3 g/kg) to the diet caused similar depression of hepatic HMG-CoA reductase activity in the two strains, whereas intestinal HMG-CoA reductase activity was significantly reduced in hyporesponders but not in hyperresponders. Cholesterol feeding induced higher free cholesterol concentrations in hepatic and intestinal microsomes of both hypo- and hyperresponders and higher activity of hepatic acyl-CoA:cholesterol acyltransferase (ACAT). Hepatic ACAT activity was significantly lower in cholesterol-fed hyperresponders than in hyporesponders, which may have contributed to the observed higher free cholesterol concentrations in hepatic microsomes of cholesterol-fed hyperresponders. Intestinal ACAT activity was similar in hypo- and hyperresponders; cholesterol feeding tended (P = 0.11) to elevate the activity of this enzyme. Hepatic cholesterol 7 alpha-hydroxylase activity was significantly higher in cholesterol-fed hyperresponders than in hyporesponders; it was slightly depressed after cholesterol loading in both rabbit strains.

Animals↗
PubMed1993

Long-term phosphorus restriction prevents corticomedullary nephrocalcinosis and sustains reproductive performance but delays bone mineralization in rats.

In a long-term experiment with three successive generations of rats, the influence of dietary phosphorus restriction (2 instead of 4 g phosphorus/kg diet) on nephrocalcinosis, reproduction and bone mineralization was studied. Nephrocalcinosis in female rats, as based on kidney calcium concentration and histological examination, was prevented by phosphorus restriction. The low phosphorus diet caused reduced femur concentrations of magnesium, calcium and phosphorus in rats of the first and second generation aged 4 to 12 wk. The low phosphorus diet resulted in lower plasma phosphorus concentrations. In the kidneys of female rats, immediately after lactation, a higher degree of tubular hyperplasia was seen after the low phosphorus diet was fed. Reproductive performance was not affected by phosphorus restriction. We conclude that 0.2% phosphorus in the diet prevents nephrocalcinosis in female rats while it sustains reproduction but delays bone mineralization.

Administration, Oral↗
PubMed1993

Dietary fructose vs. glucose stimulates nephrocalcinogenesis in female rats.

The effect of dietary fructose vs. glucose on kidney calcification (nephrocalcinosis) was studied in female rats. Fructose or glucose was incorporated into purified diets formulated either according to the nutrient requirements of rats or made nephrocalcinogenic by the addition of phosphorus (19.4 instead of 12.9 mmol/100 g diet) or by restriction of magnesium (0.8 instead of 1.6 mmol/100 g diet). Irrespective of the background composition of the diet, fructose consistently produced higher kidney calcium concentrations than did glucose. Fructose also raised kidney weight, expressed either as wet weight relative to body weight or as absolute dry weight; this greater kidney weight was not explained by the extra calcium. Fructose generally induced greater urinary concentrations of phosphorus and magnesium and lowered urinary pH compared with glucose. The greater urinary phosphorus concentrations in rats fed fructose may be responsible for the nephrocalcinogenic activity of this monosaccharide. Fructose stimulated the absorption of phosphorus and magnesium, which explains the higher concentrations of these minerals in the urine.

Administration, Oral↗
PubMed1993

Apathogenic, intestinal, segmented, filamentous bacteria stimulate the mucosal immune system of mice.

Segmented filamentous bacteria (SFBs) are apathogenic autochthonous bacteria in the murine small intestine that preferentially attach to Peyer's patch epithelium. SFBs have never been cultured in vitro. We have studied the effects of SFBs on the immune system of the host. Mice monoassociated with SFBs were compared with germ-free mice and with mice without SFBs but with a specific-pathogen-free (SPF) gut flora. SFBs versus no microbial flora raised the number of lymphoid cells in the lamina propria of the ileal and cecal mucosa, raised the number of immunoglobulin A (IgA)-secreting cells in the intestinal mucosa, produced elevated IgA titers in serum and intestinal secretions, and enhanced the concanavalin A-induced proliferative responses of mesenteric lymph node cells. The SPF flora had effects similar to but less pronounced than those mediated by SFBs. The results indicate that SFBs stimulate the mucosal immune system to a greater extent than do other autochthonous gut bacteria.

Animals↗
PubMed1993

Whisker trimming behaviour in A2G mice is not prevented by offering means of withdrawal from it.

In group-housed laboratory mice whisker trimming (removal of vibrissae) occurs occasionally, but in the A2G strain it is seen almost invariably. We have tested the hypothesis that whisker trimming in A2G mice is not prevented by offering the possibility to withdraw from it. Pairs of male or female mice showing absence of whiskers and/or absence of nasal fur were separated by placing in their cage either one or two wire screens with a 10 mm mesh. Unlike the single screen, the two screens, which were 10 mm apart from each other, excluded nose to mouth contact. After five weeks, whiskers had regrown in mice separated by the double screen, whereas in the pairs separated by the single screen whiskers remained in part absent. This suggests that 2 mice involved in whisker trimming, either actively or passively, co-operate in this behaviour.

Adaptation, Psychological↗
PubMed1993

Intestinal, segmented, filamentous bacteria in a wide range of vertebrate species.

Segmented, filamentous bacteria (SFBs) form a group of bacteria with similar morphology and are identified on the basis of their morphology only. The relationships of these organisms are unclear as the application of formal taxonomic criteria is impossible currently due to the lack of an in vitro technique to culture SFBs. The intestine of laboratory animals such as mice, rats, chickens, dogs, cats and pigs is known to harbour SFBs. To see whether this extends to other animal species, intestines from 18 vertebrate species, including man, were examined. SFBs were detected with light microscopy in the cat, dog, rhesus monkey, crab-eating macaque, domestic fowl, South African claw-footed toad, carp, man, laboratory mouse and rat, wood mouse, jackdaw and magpie. These results suggest that non-pathogenic SFBs are ubiquitous in the animal kingdom. Among apparently identical animals, there was considerable variation in the degree of SFB colonization. It is suggested that SFB colonization could serve as a criterion of standardization of laboratory animals.

Adult↗
PubMed1992

[Supplementary hay reduces fur chewing in rabbits].

We tested the hypothesis that loose grass hay as a supplement to a pelleted diet reduces fur chewing in rabbits. Weanling rabbits (n = 315) were given one of three diets ad libitum: a control, pelleted diet, the pelleted diet containing 20% (wt/wt) hay meal or the pelleted diet plus loose hay. Fur chewing was assessed indirectly by blind scoring of the extent of alopecia in live rabbits and the amount of gastric hair after slaughter. Rabbits given either loose hay or the diet pellets containing hay displayed significantly less alopecia on the back and sides than control rabbits did. Loose hay, but not the pellets containing hay, completely prevented the development of alopecia on the forehead. The provision of loose hay as supplement to the control diet pellets significantly reduced the amount of gastric hair, whereas inclusion of hay meal into the pellets had no effect. It is concluded that supplemental loose hay prevents rabbits from pulling off fur from the forehead of cage mates. This effect of hay might be related to satisfaction of a craving for nibbling.

Animal Feed↗
PubMed1992

Substrate specificity of purified rabbit liver esterase ES-1.

1. Substrate hydrolysis by two purified rabbit liver esterase-1 allozymes (ES-1A and ES-1B) was compared under conditions differing in substrate, pH and temperature. ES-1A and ES-1B activities had a similar pH and temperature dependency and similar thermal stability profile. 2. There were marked differences in specific activity of ES-1A and ES-1B. ES-1A hydrolysed procaine more rapidly than ES-1B, but was less active towards aspirin. The acetate and propionate esters of p-nitrophenyl were hydrolysed slower by ES-1A than by ES-1B. 3. The effect of substrate concentration on ES-1A activity did not comply with the Michaelis-Menten kinetics, which may be due to so-called substrate activation. 4. At identical substrate concentration, pH and temperature, selected artificial esters were better substrates for ES-1A than selected physiological substrates. Beta-Naphthyloctanoate was found to be a suitable substrate for ES-1A. 1,3-Dioctanoylglycerol was hydrolysed at a rate of only 2% of that of beta-naphthyloctanoate. 5. With methyl, p-nitrophenyl, beta-naphthyl and 4-methylumbelliferyl esters as substrates, ES-1A activity is influenced by length and structure of the acyl moiety. Likewise, ES-1A activity is influenced by the nature of the alkyl moiety of acetate esters. With acetate and methyl esters, branched chains when compared with unbranched chains reduced the esterase activity of ES-1A. Elongation of the acyl moiety up to four or five C atoms gradually raised the velocity of methyl, p-nitrophenyl, and 4-methylumbelliferyl ester hydrolysis by ES-1A. A similar pattern was found for the length of the alkyl moiety of acetate esters. 6. The high degree of similarity between the observed substrate specificity of rabbit ES-1A and that reported earlier for rat ES-10, suggests that these two esterases have a common evolutionary origin.

Animals↗
PubMed1992

Boiled coffee does not increase serum cholesterol in gerbils and hamsters.

In contrast to drip filter coffee, boiled coffee increases the serum cholesterol level in man. To identify the substance(s) responsible for this effect, it is necessary to find an animal model sensitive to boiled coffee. In this study, three groups of 20 male gerbils and three groups of six male hamsters were fed a control diet or a control diet supplemented with either freeze-dried boiled coffee or freeze-dried filtered coffee. At the end of the 5-week feeding period serum cholesterol levels were not different in either species fed the different diets. These results suggest that these animal species are not sensitive to boiled coffee, or that the cholesterol-raising factor in boiled coffee is lost during the process of freeze-drying.

Animals↗
PubMed1992

Low-density lipoprotein turnover in inbred strains of rabbits hypo- or hyperresponsive to dietary cholesterol.

In two inbred strains of rabbit with high or low response of plasma cholesterol to dietary cholesterol, low density lipoprotein (LDL) apolipoprotein (apoLDL) kinetics were determined with the use of a heterologous tracer isolated from a Watanabe heritable hyperlipidemic (WHHL) rabbit. On a diet without added cholesterol, the total clearance of apoLDL (which equals apoLDL production) did not differ significantly between rabbits of both strains. After the feeding of a diet containing 0.1% cholesterol for six weeks, plasma LDL cholesterol, plasma apoLDL and liver cholesterol concentrations rose significantly in the hyperresponsive but not in the hyporesponsive rabbits. Cholesterol feeding depressed the total fractional catabolic rate (FCR) of apoLDL in the hyper- but not in the hyporesponsive rabbits; this was attributed to a decrease of receptor-dependent FCR while receptor-independent FCR was similar in the two strains. On the diet containing cholesterol, the receptor-mediated absolute catabolic rate (ACR) of apoLDL did not differ between hyper- and hyporesponsive rabbits but receptor-independent ACR of apoLDL was higher in hyperresponders. It is concluded that the higher plasma apoLDL levels in hyperresponsive rabbits fed the 0.1% cholesterol diet are caused by a higher production of apoLDL and not by a lower flux of apoLDL through the receptor-mediated pathway.

Animals↗
PubMed1992

Liver and plasma copper concentrations in rats fed diets containing various proteins.

The question was addressed whether the type of dietary protein influences copper (Cu) concentrations in liver and plasma of rats. For this purpose, weanling female rats were fed diets containing as the sole source of protein either soybean protein, casein, amino acid mixtures simulating soybean protein or casein, lactalbumin, ovalbumin, or herring meal. The diets were balanced for residual Cu in the protein preparations. The type of protein and the composition of the amino acid mixture did not differentially influence liver Cu concentrations. Liver Cu was significantly lowered after feeding the amino acid mixtures when compared with the intact proteins. Plasma Cu concentrations were not affected by the type of protein in the diet.

Amino Acids↗
PubMed1992

Dietary iron loading does not influence biliary iron excretion in rats.

The effect of dietary iron loading on biliary iron excretion was investigated with male Wistar rats aged 6 wk. The rats were fed purified diets with either 174 or 1740 mg FeSO4. 7H2O/kg diet and demineralized water for 6 wk. Blood haemoglobin, hematocrit, and iron concentrations in kidney and heart were not affected and iron concentrations in liver, spleen, and tibia were significantly raised after feeding the high-iron diet. The high-iron diet did not raise biliary iron excretion, suggesting that biliary iron excretion does not play an important role in regulating iron metabolism in rat after dietary iron loading.

Animals↗
PubMed1992

Impaired iron status in rats as induced by copper deficiency.

The hypothesis was tested that marginal copper deficiency affects iron status. Copper restriction (1 vs 5 mg Cu/kg diet) significantly lowered iron concentrations and transferrin saturation in plasma and reduced blood hemoglobin, hematocrit, and iron concentrations in tibia and femur, but raised iron concentrations in liver. Marginal copper deficiency did not affect feed intake and bodyweight gain.

Animals↗
PubMed1992

Iron status in rats fed a purified diet without vitamin A.

The effect of vitamin A deficiency on iron status was investigated in rats. After 28 d of feeding either low or high vitamin A diets (0 vs 4000 IU of vitamin A per kg feed), the final body weight was slightly but significantly lowered by the low vitamin A diet. Plasma retinol concentrations were decreased in rats fed diets low in vitamin A. Marginal vitamin A deficiency produced slightly, but significantly lower blood hemoglobin concentrations; it did not clearly affect hematocrit. The concentration of iron in liver was significantly higher when diets low in vitamin A were fed while significantly lower levels were observed in femur.

Animals↗
PubMed1992

High intakes of tin lower iron status in rats.

The effects of relatively low (1, 10, and 50 mg/kg) and high (100 and 200 mg/kg) dietary concentrations of tin (added as stannous chloride) on iron status of rats were determined. After feeding the diets for 28 d, feed intake and body weights were not significantly affected. Iron concentrations in plasma, spleen, and tibia as well as percentage transferrin saturation were decreased in rats fed the diets supplemented with 100 or 200 mg tin/kg. In rats fed the diet containing 200 mg tin/kg, group mean hemoglobin, hematocrit, and red blood cell count were slightly lowered but total iron binding capacity was not affected. Iron status was not influenced by dietary tin concentrations lower than 100 mg/kg. If these results can be extrapolated to humans, then it may be concluded that tin concentrations in the human diet, which range from 2 to 76 mg/kg dry diet, do not influence iron status in humans.

Animals↗
PubMed1992

Dietary fructose vs glucose does not influence iron status in rats.

The effect of dietary fructose vs glucose on iron status was studied in rats. Female rats were fed for 4 wk diets containing either fructose or glucose (709.4 g monosaccharide/kg). Fructose vs glucose lowered iron concentrations in liver, kidney, and heart, but did not alter absolute iron contents.

Animals↗