Nonlinear estimation of parameters in biphasic Arrhenius plots.

This paper presents a formal procedure for the statistical analysis of data on the thermotropic behavior of membrane-bound enzymes generated using the Arrhenius equation and compares the analysis to several alternatives. Data is modeled by a bent hyperbola. Nonlinear regression is used to obtain estimates and standard errors of the intersection of line segments, defined as the transition temperature, and slopes, defined as energies of activation of the enzyme reaction.

Polyunsaturated fatty acids and protection of newborn rats from oxygen toxicity.

To test whether polyunsaturated fatty acids (PUFA) might be associated with protection against oxygen toxicity in newborn experimental animals, we performed two series of experiments. In the first series, adult female rats were fed one of three diets--regular Rat Chow, a high-PUFA (safflower oil-based) diet, or a low-PUFA (palm oil-based) diet--for several weeks before and throughout pregnancy and lactation. Newborn offspring of the three diet groups had similar antioxidant enzyme activities and surfactant development.

Effect of chronic modification of diet fat and cholesterol during gestation on plasma hormones and hepatic enzyme activities in rat fetus.

Diet-induced elevation of cholesterol and corticosterone in pregnant rats had no effect on fetal plasma cholesterol or corticosterone, 3-hydroxy-3-methylglutaryl coenzyme A or hepatic reductase activities. The data suggest that increasing the maternal cholesterol pool has no effect on cholesterol transfer to, or metabolism in, the developing offspring, and that the late gestation fetus can maintain corticosterone levels appropriate to gestational age despite diet-induced elevations in the maternal plasma.

The fatty acid composition of Northern-Canadian marine and terrestrial mammals.

The low mortality from cardiovascular disease in Greenland Eskimos has been attributed to their consumption of diets rich in omega-3 fatty acids. These fatty acids are found in fish and marine mammal lipids. Whereas the fatty acid composition of several fish species has been documented, information is more limited on the mammals which feature significantly in the diets of many Arctic populations.

Effect of cholecystokinin-octapeptide on total parenteral nutrition-induced changes in hepatic bile secretion and composition in the rat.

These studies investigated the ability of twice-daily administration of cholecystokinin-octapeptide (CCK-8) to prevent changes in hepatic bile secretory function and bile composition resulting from total parenteral nutrition (TPN) in young, growing rats. Bile was collected from the common duct before and during i.v.

The activity of 3-hydroxy-3-methylglutaryl-CoA reductase and acyl-CoA: cholesterol acyltransferase in hepatic microsomes from male, female and pregnant rats. The effect of cholestyramine treatment and the relationship of enzyme activity to microsomal lipid composition.

The relationship of microsomal cholesterol and phospholipid fatty acid composition to the activities of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and acyl-CoA: cholesterol acyltransferase was investigated in male, female virgin and pregnant rats when hepatic cholesterogenesis was stimulated by cholestyramine. Cholestyramine increased HMG-CoA reductase activity in both sexes but had no effect on microsomal free cholesterol level or acyl-CoA: cholesterol acyltransferase activity. The data suggest that during cholestyramine treatment high rates of bile acid synthesis are supported by preferential channelling of cholesterol into this pathway, whilst the substrate pool and activity of acyl-CoA:cholesterol acyltransferase are maintained unaltered.

Effect of total parenteral nutrition with linoleic acid-rich emulsions on tissue omega 6 and omega 3 fatty acids in the rat.

The effect of total parenteral nutrition (TPN) with lipid emulsions containing ca. 48% 18:2 omega 6 plus 8% 18:3 omega 3 (Intralipid) or 76% 18:2 omega 6 plus 0.5% 18:3 omega 3 (Liposyn) on the fatty acid composition of liver and plasma triglyceride and phospholipid (PL) was studied in the rat.

The effect of total parenteral nutrition in the rat on a sub-group of enteroendocrine cells.

The effect of total parenteral nutrition (TPN) in rats on a number of enteroendocrine cells was investigated. The rats were given a continuous intravenous infusion of basal TPN solution for 7 days. Samples from duodenum, jejunum and ileum were collected, immunostained and the immunoreactive cells quantified using a computerised morphometrics system.

Hepatic transport of bile salt and bile composition following total parenteral nutrition with and without lipid emulsion in the rat.

The effect of total parenteral nutrition (TPN) on bile flow and composition and on hepatic bile acid transport maximum (Tm) and bile salt-independent bile flow (BSIF) was studied in the rat following seven days TPN containing 33% calories from Intralipid (IL) or Liposyn (LP) or 0% calories from lipid. All TPN regimes markedly reduced bile flow. In no case did TPN cause an increase in bile cholesterol concentration or saturation relative to bile acid and phospholipid.

The role of diet during development on the regulation of adult cholesterol homeostasis.

Atherosclerosis is believed to begin early in life and to develop over several decades. Elevated plasma cholesterol is a major contributing factor. Studies in animals have shown that manipulation of cholesterol metabolism during its development in pre- and early post-natal life can permanently alter cholesterol synthesis and catabolism to favour lower plasma cholesterol levels in the adult faced with a high dietary cholesterol intake.

The effect of total parenteral nutrition (TPN) on the enteroinsular axis in the rat.

The effect of 6 days of total parenteral nutrition (TPN) on the enteroinsular axis was studied in vivo and in vitro in the rat. During the TPN period, blood samples were taken from control and TPN animals to determine the comparative pattern of GIP release. Glucose, insulin and GIP responses to oral glucose (OGTT) were compared in TPN and control rats.

Serial measurement of plasma cholesterol and lecithin:cholesterol acyl transferase activity in adults receiving total parenteral nutrition.

The effect of total parenteral nutrition (TPN) containing approximately 800 ml Nutralipid daily on plasma cholesterol and lecithin:cholesterol acyl transferase (LCAT) activity was studied in 11 adult hospital patients. LCAT was assayed using an endogenous (S/N) and an artificial (ASA) substrate to differentiate between altered plasma substrate composition (which would influence the S/N method) and enzyme quantity (measured by the exogenous ASA method). Total cholesterol levels increased significantly during TPN, but generally remained within normal range.

Altered effect of 3% dietary cholestyramine on plasma lipids and biliary bile acid output in the pregnant rat.

The effects of a diet containing 3% (w/w) cholestyramine on plasma total, free, and high-density lipoprotein cholesterol and triglycerides and on bile flow and composition were compared between pregnant rats fed the resin from before mating until the twentieth day of gestation and virgin rats fed the resin for an equivalent length of time. Pregnant and virgin rats consuming a similar diet but not receiving cholestyramine were also studied. In the nonpregnant rat the usual response to cholestyramine was observed as a significantly elevated plasma high-density lipoprotein cholesterol level and biliary bile acid secretion.

Cholesterol oxidation and 7 alpha-hydroxylation during postnatal development of the rat.

The activity of rat hepatic cholesterol 7 alpha-hydroxylase is low in the suckling period and rises at weaning. The oxidation of intraperitoneally administered 26(-14)C-cholesterol to 14CO2 is also low in suckling rats and increases with age as does the radioactivity in the plasma. In contrast, propionic acid oxidation to CO2 is much more rapid, suggesting that the side chain cleavage of cholesterol is not a rate-limiting process.

Influence of maternal cholestyramine treatment on cholesterol and bile acid metabolism in adult offspring.

To reduce ileal reabsorption of bile acids and to deplete hepatic cholesterol pools, female rats were fed a diet containing 5% (wt/wt) cholestyramine from 4 days prior to mating. Control rats were fed the same diet without cholestyramine. In one group on day 20 of gestation diet-fed dams and their fetuses were investigated.

Cholesterol and bile acid synthesis during total parenteral nutrition with and without lipid emulsion in the rat.

The origin of excess plasma free cholesterol known to accumulate in plasma of patients or animals given total parenteral nutrition (TPN) with lipid emulsion was investigated. Rats were infused for 8 days with a specially formulated TPN solution plus either lipid emulsion (lipid-TPN) or an equicaloric volume of 25% dextrose (dextrose-TPN). Laboratory diet-fed controls were sham operated.

Does mitochondrial ATP synthesis decline as a function of change in the membrane environment with ageing.

Cardiac mitochondria isolated from rats fed purified diets of known lipid composition demonstrate a decline in the rates of oxidative phosphorylation, ATP synthesis and oligomycin sensitive ATPase activity as the animal ages. Transitions in these lipid-dependent functions of mitochondrial energy metabolism are concomitant with changes in the lipid environment of the mitochondrial membrane.

Effect of cholestyramine administration during pregnancy in the rat.

The effect of administration of cholestyramine on plasma cholesterol level and hepatic cholesterol and bile acid synthesis was investigated in pregnant and nonpregnant rats. Rates of cholesterol and bile acid synthesis were reduced by pregnancy in both control and cholestyramine-treated rats. Administration of cholestyramine throughout gestation and pregnancy failed either to lower plasma cholesterol level or to increase bile acid synthesis, while cholesterol synthesis was only moderately stimulated.

Possible biotin deficiency in adults receiving long-term total parenteral nutrition.

Two adult patients receiving total parenteral nutrition on a long-term home basis presented with severe loss of hair. Both patients had extensive gut resection, consumed no biotin orally and received no biotin parenterally. Supplementation with Berroca-C, one ampule containing 200 micrograms biotin per day resulted in gradual regrowth of healthy hair.

Mitochondrial-membrane polar-head-group composition is influenced by diet fat.

Male Sprague-Dawley rats were fed diets containing 20% (w/w) soya-bean oil, high-erucic acid rapeseed oil or low-erucic acid rapeseed oil for 0, 12 or 23 days. The type of fat present in the diet had no effect on the total phospholipid content of heart mitochondria (micrograms/mg of protein) but did influence the phospholipid class distribution. Rats fed high-erucic acid rapeseed oil for 12 or 23 days had significantly higher mitochondrial phosphatidylcholine content than rats fed soya-bean oil.

Dynamic modulation of mitochondrial membrane physical properties and ATPase activity by diet lipid.

A longitudinal cross-over feeding design was used to investigate the relationship of dietary lipid composition to the membrane lipid environment and activity of mitochondrial ATPase in vivo. Rats were fed a polyunsaturated fatty-acid-rich oil (soya-bean oil) for 12 days, crossed-over to a monounsaturated fatty-acid-rich oil (rapeseed oil) for the next 11 days, then returned to soya-bean oil for 11 more days. Additional rats were fed either soya-bean oil or rapeseed oil throughout.

Dynamic modulation of mitochondrial inner-membrane lipids in rat heart by dietary fat.

A novel longitudinal feeding design was used to investigate the controlling influence of dietary fatty acids on the dynamic incorporation of fatty-acyl chains into phosphatidylcholine, phosphatidylethanolamine and cardiolipin in inner membrane of cardiac mitochondria. Rats were fed a polyunsaturated-fatty-acid-rich oil (soya-bean oil) for 12 days, crossed-over to a monounsaturated-fatty-acid-rich oil (rapeseed oil) for the next 11 days, then returned to soya-bean oil for 11 more days. Additional rats were fed either soya-bean oil or rapeseed oil only throughout.

Effect of strain, sex and duration of feeding on plasma fatty acids of rats fed various dietary oils.

Experiments were conducted to determine if regression of cardiac lipidosis and strain or sex differences in susceptibility to cardiopathological change induced by rapeseed oils are coincident with physiological differences in fatty acid substrates supplied to the heart. Plasma fatty acid composition was determined in male Sprague-Dawley rats after 7 or 28 days and in female Sprague-Dawley and male Chester-Beatty rats after 28 days of feeding high or low erucic acid rapeseed oils, soybean oil or peanut oil. After 28 days, C14:0 and C18:1 fell and C20:4 increased as a percent of total fatty acid in all animals irrespective of oil fed, suggesting that changes in plasma fatty acids normally occur with development.

Effects of high and low erucic acid rapeseed oils on energy metabolism and mitochondrial function of the chick.

Duplicate experiments were conducted to compare energy utilization, growth, cardiac mitochondrial oxidative phosphoryl,tion, and mitochondrial membrane fatty acid composition of chicks fed diets containing 20 parts of high erucic acid rapeseed oil (HER), low erucic acid rapeseed oil (LER) or sunflower seed oil (SFO) for 24 days. Chicks fed diets containing HER deposited less fat and utilized energy less efficiently (kcal gained/kcal consumed) than chicks fed diets containing either LER or SFO. Energetic efficiency and fat deposition of chicks pair-fed diets containing LER were significantly lower than for chicks fed diets containing SFO.