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Biomedical subjects

C D Evans

Publications and source records attributed to C D Evans.

At least 55 records · Page 3Linked to original sources
PubMed1991

Assessment of the relative skin sensitizing potency of 3 biocides using the murine local lymph node assay.

The relative skin-sensitizing potency of 3 biocides, 5-chloro-2-methyl-4-isothiazolin-3-one (the major active ingredient in Kathon CG), 1,2-benzisothiazolin-3-one and 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, was assessed using the murine local lymph node assay. Potency was ranked according to the lowest dose of material which, following epicutaneous exposure, induced a significant proliferation of T lymphocytes in the draining lymph nodes. The results showed that 5-chloro-2-methyl-4-isothiazolin-3-one was able to induce proliferative activity at significantly lower dose levels than the other 2 biocides and that it may therefore be a more potent skin sensitizer.

Animals↗
PubMed1991

Some meanings of body and self in eating-disordered and comparison subjects.

A new repertory grid was used to compare a group of 27 eating-disordered women (EDS) with a group of 20 women of normal weight without eating disorders (NWC) on contrasts from theories which link abnormalities in the perception of body and self to the eating disorders. No evidence was found for greater polarization of either self or body images in the EDS. A negative connotation of the body at normal weight and overweight was specific to EDS, but the underweight body did not have a more positive connotation. Negative connotation of normal weight is shown to be more specific for EDS than is negative connotation of the overweight body. There was no evidence for specific implications of weight for sexuality nor for family pressures against sexuality or femininity in EDS although they did construe themselves as less sexual than the NWC.

Adult↗
PubMed1990

The lamin B receptor of the nuclear envelope inner membrane: a polytopic protein with eight potential transmembrane domains.

The lamin B receptor is a previously identified integral membrane protein in the nuclear envelope of turkey erythrocytes that associates with the nuclear intermediate filament protein lamin B (Worman, H. J., J. Yuan, G. Blobel, and S. D. Georgatos. 1988. Proc. Natl. Acad. Sci. USA. 85:8531-8534). In the present report, we use cell fractionation and antibodies against the lamin B receptor to localize it to an 8-M urea-extracted membrane fraction of chicken liver nuclei, supporting an inner nuclear membrane localization. We deduced the amino acid sequence of the chicken lamin B receptor from overlapping clones obtained by screening cDNA libraries with a probe generated by the polymerase chain reaction with primers based on the partial protein sequence of the isolated protein. The mature lamin B receptor has a calculated molecular mass of 73,375 D and eight segments of hydrophobic amino acids that could function as transmembrane domains as determined by hydropathy analysis. Preceding the first putative transmembrane segment is a highly charged 204-residue-long amino terminal region that contains two consensus sites for phosphorylation by protein kinase A. Since the lamin B receptor has been shown to be phosphorylated by protein kinase A in vitro and in vivo and this phosphorylation affects lamin B binding (Applebaum, J., G. Blobel, and S. D. Georgatos. 1990. J. Biol. Chem. 265:4181-4185), it is likely that this amino terminal region faces the nucleoplasm. The amino terminal region also contains three DNA-binding motifs that are found in gene regulatory proteins and histones, suggesting that the lamin B receptor may additionally play a role in gene regulation and/or chromatin organization.

Amino Acid Sequence↗
PubMed1989

Determination of 2-n-octadecylindole-5-carboxylic acid in human plasma by high-performance liquid chromatography.

A method is described for the determination of the novel hypocholesterolaemic drug, 2-n-octadecylindole-5-carboxylic acid (I) in plasma. A homologue of I is used as the internal standard. Methanol is added to the plasma sample in order to precipitate the plasma proteins, followed by centrifugation and removal of the supernatant. This is reduced to dryness by heating under oxygen-free nitrogen, prior to reconstitution in the chromatographic mobile phase. The solution is assayed by injection on to a 5 micron particle size ODS2 analytical column, protected by a disposable RP-18 packed guard column, using an isocratic mobile phase of acetonitrile-water-isopropyl alcohol-formic acid (75:275:150:2.5, v/v). Detection is by ultraviolet absorbance at 276 nm. At a flow-rate of 1.5 ml min-1 and ambient temperature, the retention time of the drug is 16 min, whilst that for the internal standard is 21 min. This method has been validated and successfully used to assay clinical trial plasma samples. Basic pharmacokinetic parameters are presented.

Chromatography, High Pressure Liquid↗
PubMed1989

Regulation of hepatic cholesterol ester hydrolase and acyl-coenzyme A:cholesterol acyltransferase in the rat.

Cholesterol exists within the hepatocyte as free cholesterol and cholesteryl ester. The proportion of intrahepatic cholesterol in the free or ester forms is governed in part by the rate of cholesteryl ester formation by acyl-coenzyme A:cholesterol acyltransferase (ACAT) and cholesteryl ester hydrolysis by neutral cholesterol ester (CE) hydrolase. In other cell types both ACAT and CE hydrolase activities are regulated in response to changes in the need for cellular free cholesterol. In rats, we performed a variety of experimental manipulations in order to vary the need for hepatic free cholesterol and to examine what effect, if any, this had on the enzymes that govern cholesteryl ester metabolism. Administration of a 20-mg bolus of lipoprotein cholesterol or a diet supplemented with 2% cholesterol resulted in an increase in microsomal cholesteryl ester content with little change in microsomal free cholesterol. This was accomplished by an increase in cholesteryl esterification as measured by ACAT but no change in CE hydrolase activity. An increased need for hepatic free cholesterol was experimentally induced by intravenous bile salt infusion or cholestyramine (3%) added to the diet. ACAT activity was decreased with both experimental manipulations compared to controls, while CE hydrolase activity did not change. Microsomal cholesteryl ester content decreased significantly with little change in microsomal free cholesterol content. Addition of exogenous liposomal cholesterol to liver microsomes from cholestyramine-fed and control rats resulted in a 784 +/- 38% increase in ACAT activity. Nevertheless, the decrease in ACAT activity with cholestyramine feeding was maintained. These studies allowed us to conclude that changes in hepatic free cholesterol needs are met in part by regulation of the rate of cholesterol esterification by ACAT without a change in the rate of cholesteryl ester hydrolysis by CE hydrolase.

Animals↗
PubMed1989

Lovastatin treatment inhibits sterol synthesis and induces HMG-CoA reductase activity in mononuclear leukocytes of normal subjects.

The mechanism by which competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase decrease serum cholesterol is incompletely understood. The few available data in humans suggest that chronic administration of the competitive inhibitor, lovastatin, decreases serum cholesterol with little or no change in total body sterol synthesis. To further define the effect of lovastatin on cholesterol synthesis in normal subjects, we investigated the effect of a single oral dose of lovastatin and a 4-week treatment period of lovastatin on mononuclear leukocyte (ML) sterol synthesis as a reflection of total body sterol synthesis. In parallel, we measured serum lipid profiles and HMG-CoA reductase activity in ML microsomes that had been washed free of lovastatin. ML sterol synthesis did not significantly decrease (23 +/- 5%, mean +/- SEM) at 3 h after a single 40-mg dose of lovastatin. With a single oral 80-mg dose, ML sterol synthesis decreased by 57 +/- 10% (P less than 0.05) and remained low for the subsequent 6 h. With both doses, total HMG-CoA reductase enzyme activity in microsomes prepared from harvested mononuclear leukocytes was induced 4.8-fold (P less than 0.01) over baseline values. Both the 20-mg bid dose and the 40-mg bid dose of lovastatin administered for a 4-week period decreased serum cholesterol by 25-34%. Lovastatin at 20 mg bid decreased ML sterol synthesis by 23 +/- 6% (P less than 0.02) and increased ML HMG-CoA reductase 3.8 times (P less than 0.001) the baseline values. Twenty four hours after stopping lovastatin, ML sterol synthesis and HMG-CoA reductase enzyme activity had returned to the baseline values. The higher dose of lovastatin (40 mg bid) decreased ML sterol synthesis by 16 +/- 3% (P less than 0.05) and induced HMG-CoA reductase to 53.7 times (P less than 0.01) the baseline value at 4 weeks. Stopping this higher dose effected a rebound in ML sterol synthesis to 140 +/- 11% of baseline (P less than 0.01), while HMG-CoA reductase remained 12.5 times baseline (P less than 0.01) over the next 3 days. No rebound in serum cholesterol was observed. From these data we conclude that in normal subjects lovastatin lowers serum cholesterol with only a modest effect on sterol synthesis. The effect of lovastatin on sterol synthesis in mononuclear leukocytes is tempered by an induction of HMG-CoA reductase enzyme quantity, balancing the enzyme inhibition by lovastatin.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Prolonged feeding of ethanol to the young growing guinea pig. III. Effect on the synthesis of the myocardial contractile proteins.

Prolonged ingestion of ethanol may lead to a cardiomyopathy, and studies in the experimental animal have demonstrated alterations in protein metabolism. These changes include depression of protein synthesis with acetaldehyde in the acute experiment, in vitro, and after chronic ethanol ingestion in vivo. The present studies were initiated to see if the inhibition of protein synthesis following prolonged ethanol ingestion involved myocardial contractile proteins. Newly weaned guinea pigs, weighing 350 g, were placed on a regimen of normal laboratory diet with 10% ethanol in the drinking water. Calorie-matched controls, drinking dextromaltose in the water, were simultaneously run. After 40 weeks of ingesting 10% ethanol in the drinking water, hearts from growing guinea pigs were removed and synthesis of myocardial contractile proteins (myosin heavy chains, light chains (LC1, LC2), actin, and tropomyosin) assayed in vitro with 3H-labeled amino acids. With aging, there was a decrease in the rates of synthesis of all the contractile proteins. After 40 weeks of ethanol ingestion, the synthetic rates of myosin heavy and light chains and tropomyosin were the same as in calorie-matched controls, but the synthetic rate of actin was significantly decreased by 20% (p less than 0.01). This decrease in actin synthesis may be the first indication of ultimate inhibition of synthesis of all the contractile proteins which may lead to myofibrillar disorganization and vacuolization reported after chronic ethanol ingestion.

Animals↗
PubMed1985

Molecular properties of bovine interphotoreceptor retinol-binding protein.

Interphotoreceptor retinol-binding protein (IRBP) is a large retinol-carrying glycoprotein, located only in the interphotoreceptor (or subretinal) space of vertebrate eyes. It has recently been purified to apparent homogeneity. The present report presents its sedimentation, spectroscopic, and binding properties. The molecular weight of bovine IRBP, determined by sedimentation equilibrium, is 133,000. The sedimentation coefficient is 5.8S. The Stokes radius, 56 A, obtained from gel-filtration chromatography, is much larger than that expected for a globular protein of the same molecular weight. These results indicate that IRBP is asymmetric (it can modeled as a prolate ellipsoid of revolution with axial ratio of about 8:1) and explain the overestimates of molecular weight obtained in previous studies based on size-exclusion methods. The molar absorption coefficients for IRBP (at 280 nm) and for bound retinol are both unaffected by ligand dissociation. Fluorescence of the holoprotein displays neither fine structure nor energy transfer from tryptophan to bound retinol. Circular dichroism suggests a secondary structure containing approximately 15% alpha-helix and approximately 20% beta-structure, unchanged by the presence of ligand. The binding of retinol creates a positive, extrinsic Cotton effect at 330 nm, proportional to the amount of retinol bound. The apparent dissociation constant for all-trans-retinol is 1.3 X 10(-6) M. This relatively loose binding implies that, if required during the visual cycle, IRBP should be able to transfer its ligand to other binding proteins in the neural retina and retinal pigment epithelium.

Animals↗
PubMed1985

Ethanol and cardiac protein synthesis.

Acute exposure of the heart to ethanol does not appear to alter the rate of young guinea pig cardiac protein synthesis when assayed in vitro. In contrast, the primary metabolite of ethanol, acetaldehyde, markedly diminishes synthesis despite its chronotropic and inotropic effects. On the other hand, after 11-13 weeks of ethanol-drinking during growth and maturation, the synthetic capacity of the working right ventricle was decreased when measured in vitro with normal perfusate. Assay of synthesis of the contractile proteins myosin heavy and light chains, actin and tropomyosin suggests a change in synthesis or pool size of actin reflected in an alteration of relative synthesis of this protein compared to that of heavy chains. The relative synthesis of the other proteins remained at control levels. When hearts from ethanol-drinking and matched control animals were perfused under conditions of severe ischemia, there was a profound fall in protein synthesis in all hearts, and ethanol did not enhance the inhibition of synthesis. However, the hearts from ethanol-drinking animals showed a more marked and significant impairment of maintaining ejection pressure with a marked increase in coronary resistance as the perfusion progressed. It is postulated that some impairment of protein metabolism may occur during prolonged ethanol exposure, which may influence the cardiac response of another induced stress, e.g., ischemia.

Acetaldehyde↗
PubMed1985

Proteins of the bovine interphotoreceptor matrix: retinoid binding and other functions.

Bovine interphotoreceptor matrix (IPM) is rich in protein, containing a limited and specific set of these macromolecules. The matrix proteins are synthesized by adjacent tissues (neural retina and pigment epithelium), but are not, themselves, major constituents of these tissues. Of possible functional importance are the presence of some lysosomal hydrolases and of glycoprotein components that foster the aggregation of RPE cells. The IPM contains also a unique retinoid-binding protein - IRBP, a large glycoprotein located only in the IPM. IRBP carries more all-trans-retinol in light- than in dark-adapted eyes; this finding, coupled with IRBP's strategic position, indicates that IRBP may be a shuttle for vitamin A in the visual cycle. Furthermore, IRBP may mediate exchange of retinal among opsin molecules in the dark. The molecular weight of bovine IRBP is 133,000; the molecular radius is 56A. These measurements show that IRBP is probably an elongated molecule. Retinol binds relatively loosely to IRBP (with dissociation constant 1.3 X 10(-6) M), implying that IRBP should be able to transfer its vitamin A to cellular retinoid carriers in the retina and RPE. The absorbance, fluorescence, and circular dichroic characteristics of IRBP are compared to those of other retinol-binding proteins.

Acetylglucosaminidase↗
PubMed1985

Some functional characteristics of purified bovine interphotoreceptor retinol-binding protein.

Interphotoreceptor retinol-binding protein (IRBP) is a unique retinol carrier: it is a large glycoprotein existing only in the interphotoreceptor matrix (IPM), which is the extracellular material situated between and behind the photoreceptors of the neural retina. IRBP from bovine and human eyes carries endogenous retinol, as evidenced by the protein's fluorescence on gel-filtration (Sephacryl S-300) chromatography and on native (non-SDS) pore-gradient polyacrylamide gel electrophoresis. Bovine IRBP's retinol-binding sites are at most one-third occupied in light-adapted eyes and much less in dark-adapted eyes; this bleach dependence is partially reversible and suggests a role in vitamin A transport during the visual cycle. IRBP can be saturated with exogenous all-trans retinol; one ligand molecule binds per protein molecule. IRBP can be isolated rapidly from IPM by affinity adsorption onto con A-Sepharose; this preparation is 94% pure and yields 0.33 mg or 2.4 nmol of IRBP per bovine eye. An apparently homogeneous preparation can be obtained by subsequent passage through a Sepharose 4B column. IRBP is located only in the IPM, which is harvested by isotonic washing of the retina. (In the absence of this rinse to prepare IPM, the protein is found loosely associated with the retina, although not as a cellular or membrane component.) As the thoroughness of the retinal washing procedure is increased, the yield of IPM proteins (including IRBP) goes up; however, the same set of proteins, in the same ratios, always is retrieved, indicating that retinal-cell components do not contaminate seriously the IPM.

Animals↗