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Biomedical subjects

W H Elliott

Publications and source records attributed to W H Elliott.

At least 55 records · Page 3Linked to original sources
PubMed1980

Evidence that in chick embryos destruction of hepatic microsomal cytochrome P-450 haem is a general mechanism of induction of delta-aminolaevulinate synthase by porphyria-causing drugs.

A variety of prophyrinogenic compounds were tested for their effect in ovo on chick-embryo liver microsomal cytochrome P-450 haem concentration and mitochondrial delta-aminolaevulinate synthase activity. With all drugs tested, there was a 30--50% decrease in cytochrome P-450 haem concentration within 1 h of treatment, and this was closely followed by an increase in delta-aminolaevulinate synthase activity. The relationship was independent of the extent of enzyme induction and is consistent with the proposal that drug-mediated destruction of cytochrome P-450 haem is the primary mechanism of induction of delta-aminolaevulinate synthase. After induction, synthesis of delta-aminolaevulinate synthase could be maintained by inhibiting further haem synthesis. These studies suggest that induction of porphyria is a combination of two distinct processes: (a) induction of delta-aminolaevulinate synthase synthesis by destruction of cytochrome P-450 haem and consequent depletion of cellular free haem; (b) maintenance of continued delta-aminolaevulinate synthase synthesis by preventing replenishment of cellular haem either by inhibiting haem synthesis and/or by promoting continuous removal of newly synthesized haem.

5-Aminolevulinate Synthetase↗
PubMed1980

Haem control in experimental porphyria. The effect of haemin on the induction of delta-aminolaevulinate synthase in isolated chick-embryo liver cells.

2-Allyl-2-isopropylacetamide-mediated induction of hepatic porphyria was studied in isolated chick-embryo liver cells. Increased delta-aminolaevulinate synthase activity occurred within 1h of induction and continued to increase for 8h. Protoporphyrins synthesized during this time accumulated to a concentration 10-fold greater than that in the control. Removal of 2-allyl-2-isopropylacetamide from the cells by washing at 3h immediately inhibited further increases in delta-aminolaevulinate synthase synthesis. However substitution of 2-allyl-2-isopropylacetamide at 3h by deferoxamine methane-sulphonate, an inhibitor of haem synthesis, allowed continued delta-aminolaevulinate synthase induction at an unaltered rate, even though this agent did not, by itself, induce enzyme synthesis. Exogenously added haemin was shown completely to inhibit 2-allyl-2-isopropylacetamide-mediated delta-aminolaevulinate synthase induction at concentrations as low as 20nm, a value that is less than the reported physiological one. The duration of inhibition was dependent on the concentration of added haemin and was followed by a period of delta-aminolaevulinate synthase synthesis at a rate similar to that of the control. These data are consistent with the hypothesis that delta-aminolaevulinate synthase synthesis is regulated by the concentration of intracellular haem and that induction is initiated by 2-allyl-2-isopropylacetamide-mediated destruction of haem. Induction of delta-aminolaevulinate synthase was shown to be dependent on both RNA and protein synthesis, and a study of the comparative effects of cordycepin, cycloheximide and haem has shown that, at haemin concentrations up to 50nm, the inhibition of delta-aminolaevulinate synthase synthesis followed kinetics similar to the effect of cordycepin, with no synergism between cordycepin and 50nm-haemin. However, at a haemin concentration of 2mum, the inhibition of delta-aminolaevulinate synthase synthesis followed similar kinetics to the effect of cycloheximide. These data demonstrate the control of delta-aminolaevulinate synthase synthesis by low concentrations of haemin and suggests that the primary effect of haemin is at the level of transcription.

5-Aminolevulinate Synthetase↗
PubMed1980

Identification of sterols and bile acids by computerized gas chromatography-mass spectrometry.

In mass spectrometry, sterols and bile acids from fragment ions characteristic of certain steroid structures. After separation of derivatized sterols or bile acids by the gas chromatograph and fragmentation in the mass spectrometer, data collected by the computer can be collated to provide a reconstructed gas chromatogram and a series of fragment ion current chromatograms in which the relative abundances of characteristic fragment ions are plotted vs time or scan number. Intensities of these fragment ions will be greatest and hence coincide with peak elution of unidentified sterols or bile acids. The use of known amounts of labeled appropriate sterols of bile acids permits quantitation of the identified sterol or bile acid.

Bile Acids and Salts↗
PubMed1980

Synthesis of delta-aminolaevulinate synthase in vitro using hepatic mRNA from chick embryos with induced porphyria.

Polyadenylated mRNA was isolated from chick embryo liver following induction of hepatic porphyria. The RNA was translated in vitro using a wheat germ cell-free system and delta-aminolaevulinate synthase was identified in the translation products by indirect immunoprecipitation. The enzyme was not apparent in the translation products of polyadenylated RNA from non-induced livers. The molecular weight of delta-aminolaevulinate synthase synthesized in vitro was 70000 and the protein was estimated to represent up to 5% of total products synthesised in vitro. These data demonstrate for the first time that induction of chick embryo liver delta-aminolaevulinate synthase activity in hepatic porphyria correlates with a large increase in the translational capacity of isolated polyadenylated RNA for this enzyme and, together with preliminary cDNA . RNA hybridization studies, indicate that an increase in the level of delta-aminolaevulinic synthase mRNA is responsible.

5-Aminolevulinate Synthetase↗
PubMed1979

Serologic profile of exotic deer at Point Reyes National Seashore.

Serotests were conducted on axis (Axis axis) and fallow (Dama dama) deer at Point Reyes National Seashore to determine their status with respect to nine diseases enzootic to the native black-tailed deer (Odocoileus hemionus columbianus) or to resident dairy cattle. In the exotic deer, the proportion of animals that were seropositive included: anaplasmosis, 35%; bluetongue, 48%; brucellosis, 0%; bovine viral diarrhea, 2%; infectious bovine rhinotracheitis, 3%; leptospirosis, 7%; parainfluenza-3, 49%; toxoplasmosis, 8%; and Q fever, 51%. The prevalence of antibodies among a small sample of the black-tailed deer included anaplasmosis, 100%; toxoplasmosis, 29%; and Q fever, 57%. The antibody prevalences in a sample of dairy cattle in the area included anaplasmosis, 19%; toxoplasmosis, 8%; and Q fever, 100%.

Animals↗
PubMed1979

Bile acids. LIX. Purification of 5 alpha-anhydrocyprinol by preparative high-performance liquid chromatography.

26,27-Oxido-5 alpha-cholestane-3 alpha,7 alpha,12 alpha-triol can be obtained in a homogeneous state in gram quantities by passing it through one PrepPak-500/Silica cartridge mounted in a Waters Assoc. preparative liquid chromatograph. The elution solvent was methanol-chloroform (1:14). The isolated material was analyzed for purity by several chromatographic means and by elemental analysis, and was finally characterized by the usual spectroscopic means. Gas-liquid chromatography of its trimethylsilyl ether indicated the formation of a tetrakis-trimethylsilyl-26-chloro derivative, in addition to the expected tris-trimethylsilylated substance. The structure of the former compound is deduced from the fragmentation and isotope abundance in its mass spectrum and from chemical principles.

Animals↗
PubMed1979

Competitive inhibitors of rabbit hepatic microsomal 12 alpha-steroid hydroxylase.

Rabbit hepatic microsomal 12 alpha-steroid hydroxylase which is stable to storage at -70 degrees C in the pellet form was assayed for activity with [5 alpha,6 alpha-3H2]cholestane-3 alpha,7 alpha-diol solubilized with Tween 80 since methanol was incapable of maintaining the sterol in aqueous solution. Under optimized conditions in phosphate buffer, pH 7.4, containing nicotinamide, magnesium chloride, and NADPH, the enzyme conversion appeared linear for the initial 10 min. The rate of hydroxylation was proportional to protein concentration up to 4 mg/ml. Apparent Km and Vmax were 71 microM and 323 pmol of product/mg of protein/min. Based on the known structural requirements of the enzyme system, competitive inhibitors were prepared with the C-12 position derivatized as an alkene, hydroxyl, or oxo functional group. A Dixon plot revealed that 5 alpha-cholest-11-ene-3 alpha,7 alpha,26-triol was the best inhibitor with an apparent Ki of 26 microM.

Animals↗
PubMed1978

Proteinase-sensitive release of enzymes from pancreatic microsomal fraction.

Suspensions of rat pancreatic microsomal fraction release alpha-amylase and ribonuclease on incubation at 37 degrees C, but not at 2 degrees C. The release is abolished by proteolytic enzymes. Ribonuclease associated with the microsomal fraction is protected from subtilisin BPN' attack, but is sensitive after release.

Animals↗
PubMed1978

Bile acids. LIV--mass spectra of conjugated bile acids.

The electron impact mass spectra of conjugated bile acids, their 5alpha-analogs and methyl esters of glyco conjugates were determined by direct insertion into the ion source and their fragmentation patterns were found to be basically similar to those of methyl esters of the free bile acids. The conjugates are additionally characterized by a significant loss of [NH2CH2CO2H] from the glycine moiety and [CH2 = CHSO3 H] from the taurine group. Several 5 alpha- and 5 beta-isomers can be differentiated, but no general pattern of recognition is discernable. Field desorption mass spectra contain [M + Na]+ and [m + Na]2+ ions.

Bile Acids and Salts↗
PubMed1978

Bile acids LVII. Analysis of bile acids by high pressure liquid chromatography and mass spectrometry.

Several high pressure liquid chromatographic methods for the separation of conjugated and free bile acids are presented. A mixture of synthetic conjugated bile acids has been separated by reverse-phase systems consisting of either a Waters Associated' "fatty-acid analysis" or a muBondapak/C18 column eluted with a mixture of 2-propanol/potassium phosphage buffer (pH 2.5 or 7.0). The major conjugated bile acids present in the gallbladder bile of obese subjects have been analyzed each in less than 30 min and quantitated with a U.V. detector set at 193 nm. Some of the 5 alpha- and 5 beta-isomers of conjugated bile salts could be resolved in straight-phase systems on Corasil II or muPorasil columns. Mass spectra of the conjugated bile acids obtained by electron impact were characteristics of the type of amino acid attached to the side chain, and the number of hydroxyl substituents on the nucleus. Most of the isomers could readily be differentiated by the relative intensities of the fragment ions.

Amino Acids↗
PubMed1978

Bile acids LVIII. Bile acids and colorectal cancer.

Significant correlations have been reported by epidemiologists between the mortality from colorectal cancer in various populations and the consumption of meat or lipids by these populations. These have directed considerable attention to possible relationships between diet and the occurrence of this neoplasm. We have carried out studies of the composition of bile from rats as influenced by diets of varying lipid content. Two cannulas were surgically implanted to form an externalized bile duct through which bile was drained from the common duct and returned to the duodenum. Small aliquots were analyzed for total bile acids by enzymatic assay and for individual bile acids by high-pressure liquid chromatography, gas chromatography and gas chromatography-mass spectometry. Animals consuming diets highest in lipid content provided bile with the greatest amounts of bile acids. The primary bile acids, taurocholic, taurochenodeoxychilic, and tauro alpha- and beta-muricholic acids made up more than 99% of the 3 alph-hydroxy bile acids and were found in approximate molar ratio of 2:1:1. Either complete drainage of bile without return to the duodenum, or biliary tract obstruction had pronounced influence on the rate of secretion of bile and its composition.

Animal Feed↗
PubMed1978

Membrane phospholipid asymmetry in Bacillus amyloliquefaciens.

The phospholipid distribution in the membrane of Bacillus amyloliquefaciens was studied by using phospholipase C (B. cereus), phospholipase A2 (Crotalus), and the nonpenetrating chemical probe trinitrobenzenesulfonic acid. After treatment of intact protoplasts of B. amyloliquefaciens with either phospholipase, about 70% of total membrane phospholipid was hydrolyzed; specifically, about 90, 90, and 30% of phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin, respectively. Under these conditions, protoplasts remained intact and sealed. However, when protoplasts that were permeabilized by cold-shock treatment were incubated with either of the phospholipases, up to 80% of cardiolipin was hydrolyzed and phosphatidylglycerol and phosphatidylethanolamine were hydrolyzed virtually to completion. In intact cells, 92% of the phosphatidylethanolamine could be labeled with trinitrobenzenesulfonic acid under conditions in which the reagent did not penetrate the membrane to any significant extent. These results indicate that 70% of total phospholipid of this bacillus exists in the outer half of the bilayer. The distribution of phosphatidylethanolamine in this bilayer is highly asymmetric with it being located predominantly in the outer half. The results with phospholipases suggest that the distributions of cardiolipin and phosphatidylglycerol are also asymmetric but independent confirmation of this is required.

Bacillus↗
PubMed1978

Effect of growth temperature on membrane fatty acid composition and susceptibility to cold shock of Bacillus amyloliquefaciens.

We investigated the fatty acid composition of the membrane of Bacillus amyloliquefaciens grown at different temperatures. A decrease in growth temperature was accompanied by an increase in the ratio of branched- to straight-chain fatty acids and a marked increase in the level of unsaturation of branched-chain fatty acids. When cells of this organism grown at 30 degrees C were cold shocked, viability and ability to secrete extracellular protease were lost. Growth of this organism at lower temperatures or addition of Tween 80 to cells caused the critical temperature zone for cold shocking to be lowered significantly. These results suggest a direct correlation between membrane fluidity and the susceptibility to cold shock.

Bacillus↗
PubMed1978

Modulation of an apparent mRNA pool for extracellular protease in Bacillus amyloliquefaciens.

Late-log-phase cells of Bacillus amyloliquefaciens have the unusual capacity to produce extracellular protease for over 60 min in the presence of rifampin or actinomycin D at levels which strongly inhibit incorporation of amino acids into cellular protein. If cells are incubated in the presence of high levels of amino acids for 75 min this capacity is exhausted, but it is retained if the incubation is carried out in low levels of amino acids. Transfer of exhausted cells from high to low concentrations of amino acids results in a progressive recovery of the capacity for rifampin-actinomycin-insensitive protease production. The results seem best explained on the basis of the accumulation of a reserve pool of mRNA for extracellular protease. Measurement of the apparent mRNA pool size over 12 h shows a cyclical rise and fall, and these changes correlate with a periodic variation of the rate of protease production. A working hypothesis is presented to account for these observations in terms of a novel control situation over protease mRNA transcription.

Amino Acids↗