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Biomedical subjects

F Chevallier

Publications and source records attributed to F Chevallier.

At least 19 recordsLinked to original sources
PubMed1989

[Contribution of molecular biology to the prevention of cystic fibrosis. Experience in Lyon].

Enzymatic prenatal diagnosis of cystic fibrosis was performed in 113 amniotic fluids and DNA polymorphism was studied in 104 families, including 28 cases with prenatal material analysis. According to the results, the enzymatic diagnosis should be cautiously interpreted when the risk is less than 1/4. In these situations DNA analysis in the parents is very helpful to assess the reliability of enzymatic diagnosis.

Amniotic Fluid↗
PubMed1978

Diet and sterol biohydrogenation in the rat: occurrence of epicoprostanol.

The fecal sterols from rats fed several types of semipurified or commercial diets were analyzed by a combination of thin layer and gas liquid chromatography. In rats fed semipurified diets with lard, sucrose, and casein, increasing proportions of lard (0, 8, 20, 65%) enhanced the fecal coprostanol/coprostanol + cholesterol ratio (from 0.50 to 0.85). This ratio was reduced by replacing lard with triolein or a mixture of calcium oleate and linoleate (1:1) and did not change when trierucin was substituted. No coprostanol formation was observed in rats fed a diet with tripalmitin or tristearin. The addition of sodium hyodeoxycholate (0.5%) or cholestyramine (2%) to the basal diet was without effect on the coprostanol/coprostanol + cholesterol ratio in the feces. The addition of sodium taurocholate (0.2, 0.75, and 4%) strongly reduced coprostanol formation, while a chronic bile duct ligation led to an enhancement. Cholesterol feeding (0.05, 0.2, and 0.5% in the diet) slightly increased (from 51 to 66%) coprostanol formation. Trace amounts of epicoprostanol were generally found in the feces. However, in some cases a very high proportion (up to 60%) of this sterol was observed. Possible relationships between the presence of epicoprostanol and the nature of the diet are discussed.

Animals↗
PubMed1978

Daily elimination of fecal neutral sterols by humans.

A study was made of the daily elimination of fetal neutral sterols in 22 healthy subjects and the average proportions of the main sterols were established. These were cholesterol (9.5%), its main bacterial transformation products: coprostanol (65%) and coprostanone (less than 6%), cholestanol (less than 2%), delta7-cholestenol (less than 2%) and phytosterols (18%). Epicoprostanol, which indicates a secondary mean of bacterial degradation of cholesterol has been searched for systematically. In general, traces only are present but in one case it amounts to more than 8% of the neutral sterols. The bulk of neutral sterols eliminated daily is very variable for different subjects and also for a same subject, although the concentration of fecal sterols is relatively constant (6.37 +/- 0.36 mg of sterols/g of feces). For a given subject under controlled diet conditions, differences in fecal elimination of sterols can essentially be ascribed to irregularity of digestive transit.

Adult↗
PubMed1977

Effects of dietary fiber and salt mixtures on the cholesterol metabolism of rats.

The isotopic dilution method, which permits the in vivo measurements of the rates of the processes involved in cholesterol turnover, has been applied to rats fed a commercial stock diet or a basal semipurified diet in which either the nature and proportions of the source of dietary fiber or the salt mixture were changed. The cholesterolemia was about 100 mg/100 g in rats fed agar-agar, cellulose, bran or the stock diet. Pectin addition (5%) lowered significantly the plasma concentration of cholesterol (70 mg/100 g). Changes in the source of dietary fiber or salt mixture have moderate effects on the absorption coefficient of dietary cholesterol (range 58.2%-82%). In comparison to agar-agar, cellulose at 2.3% in the diet significantly lowered this coefficient, but larger amounts of cellulose (6.8% or 12.3%), or pectin (5%) were without effect, while bran addition (10%) tended to slightly decrease cholesterol absorption. Hence, high levels of cellulose in the diet increased the absorption coefficient in comparison to a low cellulose diet. A decrease of this coefficient was also observed when the calcium content of the diet was increased. Cholesterol biosynthesis and fecal excretion were inversely correlated to the absorption coefficient of dietary cholesterol in rats fed all of the semipurified diets indicating, as previously shown, that the intestine was the major source of biosynthesized cholesterol diverted into the plasma. However, feeding a commercial stock diet greatly increased the cholesterogenesis and the fecal elimination of bile acids, suggesting a high hepatic cholesterogenesis.

Animals↗
PubMed1977

[Unexpected demonstration of copper deficiency in the rat].

During many years, Wistar's rats were fed after weaning a semipurified diet containing 0.4 ppm copper and did not present clinical disorders of copper deficiency. Rats of same strain fed on the same diet, but housed in a new physical environment presented, a year later, specific signs of deficiency. A new salt-mixture raising the copper content of the diet to, 5.2 ppm made the deficiency signs diseapear and the rats growth come back to the initial rate. These results showed once again the important relations existing between the organism and its physical environment, the diet being just one of these elements. Rigorous breeding conditions, animal selection and modernisation of animal houses involve a specific feeding related to this new conditions particularly when semipurified diets are used for weaning rats.

Animals↗
PubMed1976

[Regulation of cholesterol levels in plasma and liver of adult rats].

The dynamics of cholesterol-system in the plasma is characterized by a parameter which is a linear function of the internal secretion of cholesterol. So, the level of plasma cholesterol from synthesis is a low as its flow is high. Moreover, the level of plasma cholesterol from diet is simultaneously proportional to the flow of cholesterol intestinal absorption and dependent on the dynamics controlled by the internal secretion. The laws of the cholesterolemia cumulate these partial laws. Similar relations concern the esterified cholesterol in the liver.

Animals↗
PubMed1976

Effects of the thyroid state on cholesterol metabolism in the rat.

An isotopic equilibrium method which permits the in vivo measurements of cholesterol turnover processes was applied to different groups of rats: (1) radiothyroidectomized, (2) low-iodine fed, and (3) L-thyroxin fed. Plasma cholesterol concentrations were enhanced after thyroidectomy and reduced by large dose of L-thyroxin. A low-iodine diet decreased plasma thyroxin level but did not affect plasma cholesterol. Thyroid levels in plasma modified the coefficient of intestinal absorption of cholesterol. After thyroidectomy or under conditions of reduced thyroxin formation this absorption coefficient was enhanced. The absorption coefficient of cholesterol was decreased in rats receiving 31 or 61.5 mug/day of L-thyroxin but was not changed in rats fed 110 mug/day L-thyroxin. The proportion of de novo biosynthetisized cholesterol eliminated into the feces (external secretion) was reduced while thyroxin levels were low. The fecal excretion of cholesterol and the in vitro exchange of cholesterol between erythrocytes and plasma were increased by L-thyroxin ingestion. The rate of cholesterol biosynthesis was decreased after thyroidectomy and enhanced by L-thyroxin feeding. In fact, changes in thyroid state modified indirectly the biosynthesis of cholesterol by its effects on metabolism and on the coefficient of intestinal absorption of cholesterol.

Animals↗
PubMed1976

Elongation of (omega-14C)oleic acid and (omega-14C)nervonic acid.

During feeding experiments with [omega-14C]oleic acid and [omega-14c]nervonic acid to adult rats, 14C-labelled C26, C28 and C30 fatty acids were recovered from the intestinal mucosa, liver, plasma, kidney and stools. The structures of these fatty acids were determined by g.l.c., radio-g.l.c. and mass spectrometry. The Schmidt and Ginger degradation methods indicated that most of the 14C found in these extra-long fatty acids remained in the omega position. These radioactive extra-long fatty acids were found mainly in the polar lipids of rats killed 3 or 15 h after being fed on labelled oleic acid or nervonic acid. Rats killed 63 h later yielded only traces of these extra-long fatty acids. When the rats were given antibiotics or received the same radioactive fatty acids by intravenous injection, the labelled extra-long fatty acids could not be detected in any of the tissues. We conclude that they were probably synthesized by elongation of oleic acid and nervonic acid by intestinal micro-organisms (probably yeasts) and then absorbed by the intestinal mucosa.

Animals↗
PubMed1976

In vivo study of free and esterified cholesterol turnover in various tissues of the rat.

Rats were infused for 3.5 to 10 hrs with either red cells or plasma previously labelled in vivo by [3H]-cholesterol. Cholesterol specific radioactivities were measured in plasma, HDL, LDL and VLDL, and various tissues. Red cell infusions led to a higher labelling of free than of esterified cholesterol in the plasma of infused rats. The opposite situation was observed following plasma infusion. Comparison of free and esterified cholesterol specific radioactivities in each tissue showed that esterified cholesterol was transferred from plasma to all the tissues, except the adrenals. Study of the ratios of cholesterol specific radioactivities from one experimental group to the other in each tissue, made it possible to demonstrate clearly the occurence of hydrolysis within all the studied tissues except 5 of them where its existence remains uncertain (lung, heart, kidney, tendon, muscle) and of esterification in 3 tissues (adrenal, liver lung). In addition, ratios of cholesterol radioactivities (free/ester) were found to be identical in plasma and in 4 tissues, where neither hydrolysis nor esterification were detected (heart, muscle, kidney, tendon). This finding is an argument in favor of a simultaneous transport of free and esterified cholesterol from plasma into these 4 tissues and suggests that the entire lipoprotein particles can penetrate these tissues, with no specificity of one special class. In adrenal, unlike all other tissues: 1) the turnover of esterified cholesterol was achieved mostly by hydrolysis and esterification in situ; 2) a preferential lipoprotein class (LDL) was responsible for the transport of free cholesterol from the plasma.

Adrenal Glands↗