The determination of total and ester cholesterol in whole blood, serum or plasma

Constituents of temporal gland secretion of the African elephant,Loxodonta africana

Temporal gland secretion (TGS), obtained from 15 different mature African elephants in Kruger National Park was analyzed for volatile constituents. Only five volatile components were present.p-Cresol was present in all samples, but phenol was found as an appreciable component of only one sample and as trace amounts in six others. Three sesquiterpenes were identified, the latter two being new natural products:E-farnesol, farnesol hydrate (3,7,11-trimethyl-2,10-dodecadien-1,7-diol), and farnesol dihydrate (3,7,11-trimethyl-2-dodecen-1,7,11-triol). These sesquiterpenes represent the first isolated from mammals. Ten samples of TGS, serum, and saliva were assayed for cholesterol, urea, and proteins including several enzymes.

Effects of prolonged, strenuous exercise on lipids and thyroxine in serum

Serum lipids and thyroxine were determined in 26 men participating in a 90-km cross-country ski race, before, immediately after, and on the following days. Serum cholesterol was unchanged immediately after the race, but then fell significantly and remained low during the observation period. During the race the fatty acid composition of serum free fatty acids changed towards the composition of ordinary adipose tissue. The compostiion of serum triglycerides showed similar but less pronouced changes. On the following days an increase in the arachidonic, and a decrease in the linoleic acid fraction of the total serum lipids were observed. Total thyroxine and free thyroxine in serum were significantly increased at the end of the race, but had returned to the pre-raced levels during the rest of the observation period. The observations correspond to the findings during acute, severe illness, and are compatible with the hypothesis that some of the changes in serum lipids following severe somatic stress are due to increased thyroid hormone activity.

Plasma vitellogenin of grouper (Epinephelus malabaricus): isolation and properties

Radiolabelled vitellogenin produced by juvenile grouper following injection of 3H-leucine, 32P-orthophosphate and estradiol-stimulation was purified by anion-exchange and gel filtration chromatography and characterized by electrophoresis and chemical analysis. The radiolabelled product was found to exist in two heterogeneous molecular weight forms by electrophoresis under nondenaturing conditions on polyacrylamide gel with M(r), of 260,000 and 525,000. It showed two protein monomers (M(r) 113,000 and 140,000) on electrophoresis under denaturing condition on a sodium dodecyl sulphate-polyacrylamide gel. The purified material contained 17.2% total lipid with 1.3% cholesterol and 2.1% triglycerides, 8-21 micrograms/mg protein total carbohydrate and 6.8 micrograms phosphate/mg protein; amino acid analysis showed a profile comparable to that found for vitellogenins isolated from the grouper, medaka, goldfish and rainbow trout. The study showed grouper vitellogenin to be a glycophospholipoprotein similar in composition to vitellogenins from other teleosts and demonstrated that vitellogenins can be induced in juveniles by injection with estradiol-17 beta.

Biochemical effects of Catha edulis, cathine and cathinone on adrenocortical functions

Catha edulis is a plant that grows in certain areas of East Africa and the Arab Peninsula. The stimulating properties of fresh material were described more than seven centuries ago and today the habit of inducing a state of euphoria and subjective well-being by chewing Catha edulis prevails among the inhabitants of these regions. Oral administration of this plant and its active constituents (cathine and cathione) on experimental animals might have stimulating effects on adrenocortical function. This was indicated by the significant decrease in adrenal cholesterol, ascorbic acid, glycogen, and the increase in adrenal phosphorylase activity. In addition, the level of urinary 17-hydroxycorticosteroids and plasma free fatty acids were increased.

Steady-state kinetics of ubiquinol-cytochrome c reductase in bovine heart submitochondrial particles: diffusional effects

In an attempt to establish the relative importance of diffusional and chemical control in the reactivity of the two of the two substrates, ubiquinol and cytochrome c, we have undertaken as extensive characterization of the steady-state kinetics of ubiquinol-cytochrome c reductase (EC 1.10.2.2) when present in open submitochondrial particles from bovine heart. The kinetic pattern follows a Ping Pong mechanism; contrary to the situation found with the isolated enzyme [Speck and Margoliash (1984) J. Biol. Chem. 259, 1064-1072, and confirmed in our laboratory], no substrate inhibition by oxidized cytochrome c was observed with the membrane-bound enzyme. Endogenous oxidized ubiquinone-10 is unable to exert product inhibition under the conditions employed. In the Ping Pong mechanism for this enzyme, the reaction scheme can be clearly divided into two parts, and the Kmin. (kcat./km) value for one substrate is independent of the rate constant for the second substrate. Both ubiquinol-1 and ubiquinol-2 can be used as electron donors reacting with the enzyme from within the lipid bilayer [Fato, Castelluccio, Palmer and Lenaz (1988) Biochim. Biophys. Acta 932, 216-222]; the kmin. values for ubiquinols, when calculated on the basis of their membranous concentrations, are significantly lower than the kmin. for cytochrome c. The temperature-dependence of the kinetic parameters was investigated by titrating each of the substrates under quasi-saturating concentrations of the second substrate. Arrhenius plots of Vmax. extrapolated from both cytochrome c and ubiquinol titrations were linear, when care was taken to verify the quasi-saturating concentrations of the fixed co-substrate. The Arrhenius plots for the kmin. values for both ubiquinol and cytochrome c were linear, but the activation energy was much higher for the former, particularly when calculated for ubiquinol dissolved in the lipid phase; the very low value of activation energy of the kmin. for cytochrome c is strong support for diffusion control being present in the reaction of cytochrome c with the membranous enzyme. In contrast to the soluble enzyme, ubiquinone titrations of submitochondrial particles at low cytochrome c concentrations deviated from hyperbolic behaviour. Changing the medium viscosity with either poly(ethylene glycol) or sucrose had a strong effect on the cytochrome c kmin., whereas the change in the ubiquinol kmin. was much smaller. From the viscosity studies the extent of diffusional control could be calculated, revealing that the reaction with cytochrome c was mostly diffusion-limited. The viscosity of the membrane was changed by incorporating cholesterol; no significant effect on the ubiquinol kmin. ascribable to diffusion control could be recognized.(ABSTRACT TRUNCATED AT 400 WORDS)

Studies of the spontaneous transfer of retinol from the retinol:retinol-binding protein complex to unilamellar liposomes

The transfer of retinol from its complex with the retinol-binding protein to cell surfaces was studied using unilamellar liposomes as a cell surface model. The transfer of retinol to liposomes at 37 degrees C was rapid and reached an apparent equilibrium within 60 min. The amount of retinol transferred to the liposomes at equilibrium was directly proportional to the starting concentration of retinol:retinol-binding protein over a wide range of retinol:retinol-binding protein concentrations and also directly proportional to the concentration of liposomal phospholipid in the system, when the concentration of retinol:retinol-binding protein was held constant. The transfer increased slightly with temperature. Transfer was increased by a factor of 1.8 at pH 4.5 compared to pH around 7. Prealbumin in amounts sufficient to complex all retinol:retinol-binding protein, decreased retinol transfer to liposomes indicating that prealbumin increases the affinity of retinol-binding protein for retinol. Addition of apo retinol-binding protein to the system decreased the transfer of retinol to liposomes considerably probably through competition with the liposomes for retinol. In similarly designed experiments delipidated bovine serum albumin competed much less with liposomes for retinol. The results show that spontaneous transfer of retinol from the retinol:retinol-binding protein complex to liposomal membranes occurs in vitro and suggests that a similar transfer may occur in vivo from retinol:retinol-binding protein to cell surface membranes.

Effects of cholesterol on the kinetics of mitochondrial ATPase

Enrichment of the inner mitochondrial membrane with cholesterol induces an increase in ATPase activity with a decrease in the Km for ATP. Cholesterol also abolishes the discontinuity normally found in the Arrhenius plot of ATPase activity. Since no change is detected in the rate of proton translocation through the ATPase membrane sector, it is concluded that cholesterol incorporation induces changes in the hydrolytic step of ATPase via a conformational change transmitted from the membrane sector to the catalytic sector F1.

Influence of cholesterol and prostaglandin E1 on the molecular organization of phospholipids in the erythrocyte membrane. A fluorescent polarization study with lipid-specific probes

Anthryl-labeled fluorescent probes closely mimicking phosphatidylcholine and sphingomyelin were applied to study the state of these phospholipids in the rabbit erythrocyte membrane. At normal cholesterol levels both probes exhibited higher fluorescence polarization values in the membranes than in phospholipid vesicles of similar lipid composition, indicating a decreased fluidity of the probe environment in erythrocyte ghosts. In ghosts prepared from normal erythrocytes no evidence of lateral separation of phosphatidylcholine and sphingomyelin was found. At higher cholesterol levels, however, these lipids appear to segregate. Probably the effect of cholesterol on the erythrocyte membrane lipids involves lipid-protein interactions. At physiological concentrations, prostaglandin E1 only weakly affects the state of phosphatidylcholine and sphingomyelin in erythrocyte membranes. Cholesterol enrichment amplifies the effect of prostaglandin E1. Although the prostaglandin E1-induced changes depended much upon whether the ghosts were enriched with cholesterol in vitro or in vivo, with both types of ghosts effects of prostaglandin E1 were seen at extremely low effector concentrations that may have presented a few molecules of prostaglandin per ghost. The structural and functional significance of these findings is discussed.

Induction, isolation and a characterization of the lipid content of plasma vitellogenin from two Salmo species: rainbow trout (Salmo gairdneri) and sea trout (Salmo trutta)

Vitellogenin synthesis is induced in juvenile rainbow trout (Salmo gairdneri) and juvenile sea trout (Salmo trutta) by estradiol-17 beta. A purification procedure for vitellogenin from trout plasma by precipitation with MgCl2-EDTA and subsequent anion exchange chromatography on DEAE-Sephacel is described. The total lipid contents of purified rainbow trout and sea trout vitellogenins are 18 and 19%, respectively. Approximately 2/3 of the lipids are phospholipids, while the remainder consists of triglycerides and cholesterol. Phosphorus determinations on delipidated vitellogenin yield a phosphorus content of 0.63% in rainbow trout and 0.58% in sea trout vitellogenin. Native (dimeric) vitellogenins from rainbow trout and sea trout both have an apparent molecular weight of 440,000, when estimated by gel filtration on Sepharose 6B.

Serum lipids during treatment with glucose-insulin-potassium in myocardial infarction

Total cholesterol, phospholipids, and triglycerides in serum were studied during myocardial infarction in a patient group treated with glucose, insulin and potassium (GIK), and a conventionally treated group. There was no difference in the typical changes of cholesterol and phospholipids between the groups, but the GIK-treated group had a late rise in triglycerides.

The influence of cholesterol incorporation and removal on lipid-bilayer viscosity and electron transfer in rat-liver microsomes

The incorporation and removal of cholesterol from rat liver microsomes was used as a methodical approach to investigate the molecular organization of microsomal redox-chains. It was shown that the incorporation of cholesterol in microsomes increases and removal of cholesterol decreases lipid bilayer viscosity as indicated from the rate of fluorescent probe-pyrene eximerisation in cholesterol-enriched and cholesterol-depleted microsomes. The increase of membrane viscosity slows down the initial rates and decreases the rate constants of cytochrome b5 reduction by NAD(P)H, whereas the decrease of membrane viscosity enhances the initial rates and increases the rate constants of these reactions. The rates of cytochrome P450 reduction by reduced pyridine nucleotides do not depend on the viscosity of lipid bilayer. The incorporation and removal of cholesterol from microsomes was not followed by any essential changes in the rates of dimethylaniline N-demethylation, aniline p-hydroxylation, p-nitroanisole O-demethylation, oxygen consumption, oxidation of NADH and NADPH. Thus the reduction of cytochrome b5 by NADH and NADPH is the diffusion-dependent reaction in the redox-chains of microsomes only.

A study of the plasma lipoproteins and the tissue lipids of the migrating lamprey, Mordacia mordax

Sea lampreys, Mordacia mordax, were collected in spring from the Yarra River, Victoria, during their upstream spawning migration, to study the lipid composition in their tissues and plasma and their lipid transport system. Plasma lipoproteins were isolated by preparative ultracentrifugation and their chemical compositions were analyzed. The major classes of lipoproteins were found to be similar to those of man and higher animals. Lipids from the muscle and liver were analyzed for fatty acids. The striking feature of the lipids in the migrating lamprey is the presence of very high levels of cholesterol in both plasma and muscle. The possible metabolic roles of cholesterol have been discussed.

A rapid and sensitive assay for determination of cholesterol in membrane lipid extracts

A commercially available enzymatic assay (Boehringer Monotest) was modified to allow a rapid and sensitive determination of cholesterol in membrane lipid extracts. This was achieved by adding 0.5% Triton X-100 to the reagent solution. The detergent did not interfere with the assay. The relationship between the amount of cholesterol per assay and the absorbance at 500 nm was linear up to 100 micrograms. The recovery in the assay was better than 95%. The assay was applied to the determination of cholesterol in erythrocyte membrane lipid extracts.

The non-covalent binding of benzo[a]pyrene and its hydroxylated metabolites to intracellular proteins and lipid bilayers

The non-covalent interactions of benzo[a]pyrene (BP) and several of its hydroxylated metabolites with ligandin, aminoazodye-binding protein A (Z-protein, fatty acid binding protein) and lecithin bilayers have been studied by equilibrium dialysis, an adsorption technique and fluorescence spectroscopy. Binding affinities expressed as v/c (where v = moles of BP or BP metabolite bound per mole of protein or lipid and c = unbound concentration), were measured at concentrations sufficiently low that there was no self-association of the unbound compounds as judged by their fluorescence characteristics. 3-Hydroxybenzo[a]pyrene (BP-3-phenol), 4,5-dihydro-4,5-dihydroxybenzo[a]pyrene (BP-4,5-dihydrodiol) and 7,8-dihydro-7,8-dihydroxybenzo[a]pyrene (BP-7,8-dihydrodiol) bind more strongly (v/c = 10(5)-5 x 10(5) l x mol-1) to all three binders than does BP itself (v/c = 10(4)-7 x 10(4) l x mol-1). 9,10-Dihydro-9,10-dihydroxybenzo[a]pyrene (BP-9,10-dihydrodiol) binds to ligandin with an affinity similar to those of the other BP metabolites studied here, but binds much less strongly to both protein A and lecithin (v/c = 10(4) and 3 x 10(4) x mol-1, respectively). The low affinity of BP-9,10-dihydrodiol for lecithin would account for earlier findings that on incubation of BP with isolated rat hepatocytes, this metabolite egressed from the cells to the extracellular medium much more readily than either BP-4,5-dihydrodiol or BP-7,8-dihydrodiol. Calculations based on these results suggest that within hepatocytes BP and its metabolites, including BP-9,10-dihydrodiol, will be found almost exclusively associated (> 98%) with lipid membranes.

Is propylene glycol an inert substance?

The effect of 30 day administration of undiluted propylene glycol (1,2-propanediol, PG) on plasma and liver lipids was studied in adult male Sprague-Dawley rats. When compared with the control group no significant difference was observed in plasma concentration of total phospholipids, cholesterol, triglycerides and free fatty acids, and in liver concentration of phospholipids, triglycerides and gangliosides. Liver total cholesterol was moderately, but significantly, increased.

Contribution of the platelet factor V content to platelet factor 3 activity

The procoagulant activity obtained from bovine thrombocytes has been compared to that of lipids isolated from platelets, with and without the addition of purified bovine factor V. A one-stage assay, which consisted of delipidated bovine plasma containing RVV-activated factor X, was used to assess the activity. At low lipid concentrations no difference in coagulant activity was found between sonicated vesicles of extracted platelet lipid and lysed platelets. At higher lipid concentrations, however, the extracted lipids were found to be less active than lysed platelets. Determination of factor V in suspensions of gel-filtered platelets demonstrated that suspensions containing 2 X 10(9) platelets per ml possessed about 1% of the factor V activity present in a normal bovine plasma pool. Platelet lysis by sonication produced a five-fold increase in factor V activity. Addition of factor V to sonicated vesicles of extracted platelet lipid, so as to produce an identical factor V activity per amount of lipid as found in lysed platelets, decreased the clotting time only in the higher lipid concentration range. A further three-fold increase in the amount of factor V added to the lipid vesicles made the coagulant properties of the lipid vesicles indistinguishable from those of lysed platelets over the whole range of phospholipid concentrations tested. When the conditions of the test were changed by diminishing the concentration of factor Xa in the substrate plasma, the difference between lysed platelets and extracted platelet lipid disappeared completely. It is concluded that the higher coagulant activity of lysed platelets, as compared to that of extracted platelet lipid, can be ascribed to platelet factor V activity. Therefore there is no compelling necessity to postulate the existence of a specific procoagulant factor in the platelet other than factor V or phospholipids.

The isolation and analysis of the luminal plasma membrane of calf urinary bladder epithelium

The luminal plasma membrane of calf urinary bladder epithelium (urothelium) has been isolated by a method designed to preserve enzymic activity as well as structural integrity. The yield was about 80 micrograms per calf bladder. Low levels of 5' nucleotidase, Mg2+-ATPase and (Na+ + K+)-ATPase activities were found in the luminal membrane fraction. Cerebroside was the major lipid present and dodecyl sulphate gel electrophoresis revealed a complex protein and glycoprotein composition in the whole membrane. A membrane fraction consisting of only the plaque areas was shown to have a simpler protein composition with major polypeptides of apparent Mr 12 000 and 22 000. These may associate to form a 30 000 apparent Mr complex which could represent the individual 'particles' of the dodecameric subunits seen by electron microscopy in the plaque regions.

Effect of ascorbic acid on oxygen consumption, glycolysis and lipid metabolism of diabetic rat testis. Ascorbic acid and diabetes, I

Alloxan diabetes caused a marked stimulation of endogenous oxygen uptake by rat testis tissues. However, the oxygen uptake in the presence of added glucose or pyruvate as substrate was significantly reduced. The ability of the testis tissues to utilize these substrates and to produce lactate was significantly inhibited in the diabetic animals. Alloxan diabetes also increased the levels of cholesterol, cholesterol esters, non-esterified fatty acids, triglycerides and phospholipids in rat testis tissues. Treatment of the diabetic rats with ascorbic acid caused more or less a normalization of all the parameters tested.

Differential solubilization of proteins, phospholipids, free and esterified cholesterol of rat liver cellular membranes by sodium deoxycholate

1. Smooth microsomes, Golgi-rich fractions, and light and heavy plasmalemmal subfractions from rat liver were isolated and their purity assessed using enzymic, chemical and morphological criteria. 2. Membranes were prepared by Tris-EDTA washing combined with sonication treatment of the different subcellular fractions. 3. Washed membranes were submitted to differential solubilization with 0.26% sodium deoxycholate. When the deoxycholate/phospholipid molar ratio (R) is raised, all the membranes showed a maximum protein solubilization occurring at R approximately equal TO 2. The higher the membrane neutral lipid to phospholipid molar ratio is, the lower the solubilized protein plateau lies. 4. Phospholipids are solubilized in slightly greater amounts than proteins and their solubilization is complete at R equals 14-16. 5. For R smaller than 2, sterols are solubilized in slightly greater amounts than phospholipids. At maximum protein solubilization, cholesterol and cholesterol esters completely differ in their behaviour. The whole membrane cholesterol goes into solution for R equals 14-16 while the solubilization of esterified cholesterol is never complete. The higher the protein plateau is, the lower the cholesterol esters solubilization curve asymptote lies.

Macrophage plasma membranes. I. Isolation and studies on protein components

Plasma membranes have been isolated from pure populations of rabbit alveolar macrophages which were swollen in water, fixed briefly with glutaraldehyde, disrupted by Dounce homogenization, and separated by sucrose gradient centrifugation. The recovered membranes exhibited good structural preservation and enzymatic activity; both morphologic and biochemical evidence indicated a high degree of purity (>90%) of the membrane preparation. Interiorized plasma membranes were also prepared without exposure to glutaraldehyde from phagocytic vacuoles recovered from alveolar macrophages which had ingested large numbers of polystyrene spheres. These membranes were contaminated with lysosomal constituents, but they were nevertheless of value for comparison to the "pure" membranes isolated by the glutaraldehyde procedure. Acrylamide gel electrophoresis of the solubilized plasma membranes and phagolysosomal membranes revealed similar protein patterns, with seven to nine individual components ranging in molecular weight from 70,000 to 140,000. The two most rapidly migrating components gave positive reactions for lipid as well as protein. A band containing carbohydrate was detected near the origin of the plasma membrane gels. Antisera were made by injecting guinea pigs with the purified rabbit alveolar macrophage plasma membranes. Gel diffusion and immunoelectrophoretic study of these antisera established the presence of rabbit immunoglobulin G and of one or two other antigenic constituents in the membrane preparation.