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Biomedical subjects

C H Chou

Publications and source records attributed to C H Chou.

107 records · Page 6Linked to original sources
PubMed1976

Basis of microheterogeneity of myelin basic protein.

The basic protein of bovine central nervous system myelin contains a single polypeptide chain of 170 amino acids. Multiple components of basic protein have been observed on disc gel electrophoresis and ion exchange chromatography at alkaline pH, but the basis of the microheterogeneity has not been established. In the present study myelin basic protein from bovine spinal cord was chromatographed on carboxymethylcellulose at pH 10.4 in glycine buffer/2 M urea. Three major peaks were obtained, identified as components 4, 5, and 6 in the oder of their elution from the column by a linear salt gradient. The amino acid compositions of tryptic peptides from components 4 and 6 were identical and the COOH-terminal sequence, Ala-Arg-Arg, was intact for all three components. Component 4 was found to differ from component 6 by partial phosphorylation of threonine 98 and serine 165. This modification was estimated to account for 50% of component 4. Component 5 differed from component 6 by partial deamidation of glutamine residues 103 and 147, which accounted for 80% of this component. These modified glutamine residues were also present in component 4 and constituted another 15% of this component. It was considered that component 6 was the native, unmodified species of basic protein and that component 4 differed by a net negative charge of 2, and component 5 by a net negative charge of.1 as a result of these modifications. The nonrandom nature of the modifications suggested the involvement of specific enzymes.

Amino Acids↗
PubMed1975

The immune response against an encephalitogenic fragment of guinea pig basic protein in the Lewis and Brown Norway strains or rat.

Lewis rats which have Ir-EAE gene develop EAE after challenge with either GPBP or GPEF, a 42-residue fragment. BN rats which lack the Ir gene do not develop EAE after challenge with these proteins. The immune response against GPEF was compared in these two strains of rats. It was found that Le rats produce small amounts of antibody and a cell-mediated immune response against GPEF; in contrast BN rats did neither. These findings support the concept that the Ir-EAE gene exerts its effect by controlling the immune response against GPEF.

Animals↗
PubMed1972

Thiolester substrates for transamidating enzymes: studies on fibrinoligase.

Esters of thiocholine were shown to inhibit the crosslinking of fibrin clots by the transamidating enzyme, fibrinoligase (thrombin-activated fibrin-stabilizing factor or activated Factor XIII). Inhibition depended on the nature of the acylating group with the phenylpropionyl, phenylbutyryl, and trans-cinnamoyl esters being most effective of the compounds tested so far. Use of the thiolesters made it possible for the first time to study the reactions of fibrinoligase in fully synthetic substrate systems. Enzyme-catalyzed acyl-group transfers from the thiol-esters to a fluorescent amine [N-(5-aminopentyl) - 5 - dimethylamino - 1 - naphthalenesulfonamide] could be readily demonstrated and measured.Trans-cinnamoylthiocholine reacted with fibrinoligase in a totally calcium-dependent manner in the absence of any added amine, thus providing the first evidence for an esterolytic pathway for this enzyme. Spectral qualities, as well as appreciable extent of solubility in water, would seem to make trans-cinnamoylthiocholine a specially suitable substrate for further studies.

Acylation↗
PubMedDate not supplied

Effect of modulated glucose uptake on high-level recombinant protein production in a dense Escherichia coli culture.

Methyl alpha-glucoside (alpha-MG) is a metabolically inert glucose analog sharing the same phosphotransferase system with glucose. The potential of using this compound, which acts as a nontoxic competitive inhibitor, to modulate glucose uptake and subsequently reduce the acetate accumulation rate was investigated. In a complex medium, no significant effect on the growth rate was observed when the alpha-MG to glucose ratio was low. The effect of alpha-MG supplementation on the production of a model recombinant protein, CadA-beta-galactosidase, under the regulation of a pH-inducible promoter in a batch culture was also examined. It was observed that the amount of acetate accumulation was drastically reduced in the presence of alpha-MG. More importantly, recombinant protein productivity was significantly improved. A very high volumetric productivity of approximately 1.6 g/L recombinant protein in a dense culture with an OD600 of 35 was obtained in a simple batch fermentation. Even at this high cell density, the specific protein productivity was maintained at a high level and was estimated to account for about 40% of the total cellular protein.

Bacterial Proteins↗
PubMedDate not supplied

Health effects classification and its role in the derivation of minimal risk levels: neurological effects.

The agency for Toxic Substances and Disease Registry (ATSDR) uses substance-specific minimal risk levels (MRLs) to assist in evaluating public health risks associated with exposure to hazardous substances. By definition, "MRLs are estimates of daily human exposure to a chemical that are likely to be without an appreciable risk of adverse noncancer health effects over a specified duration of exposure." MRLs serve as screening levels for health assessors to identify contaminants and potential health effects that may be of concern for population living near hazardous waste sites and chemical releases. MRLs for each substance are derived for acute (1-14 days), intermediate (15-364 days), and chronic (365 days and longer) exposure durations, and for the oral and inhalation routes of exposure. The MRLs are derived from data compiled from a current comprehensive literature search and are presented in ATSDR's toxicological profile for that substance. In this paper we outline ATSDR's guidance for evaluating the neurological end point as discussed in the agency's toxicological profiles. Ranking neurological effects into less serious and serious categories and applying this procedure to the derivation of health guidance values or MRLs are also described. Specific examples of ATSDR MRLs based on neurological effects are presented.

Cholinesterase Inhibitors↗
PubMedDate not supplied

Relationship between lipophilicity and hepatic dispersion and distribution for a homologous series of barbiturates in the isolated perfused in situ rat liver.

The hepatic disposition kinetics of a homologous series of 5-n-alkyl-5-ethyl barbituric acids (methyl, ethyl, propyl, butyl, and pentyl) were determined using a single-pass perfused in situ rat liver preparation. The perfusion experiments were conducted using protein-free Krebs bicarbonate medium, delivered at a constant flow of 15 ml/min. Each barbiturate was injected separately into the portal vein as a rapid bolus (25 micrograms/50 microliters) at appropriate intervals in a random order. The venous outflow concentrations of the barbiturates were determined by HPLC. A nonlinear least squares program was used to fit the axial dispersion model of hepatic elimination to the outflow profiles. With increasing length of the alkyl chain, there was a significant increase in the volume of distribution in the liver (0.85 +/- 0.12 ml/g for methyl and 4.87 +/- 1.27 ml/g for pentyl), which led to an increased organ mean transit time (35 +/- 2.4 sec for methyl and 223 +/- 32.8 sec for pentyl). The increased volume of distribution may have arisen from greater binding to intracellular proteins and/or greater partitioning into lipophilic components of hepatic tissue. The dispersion numbers of this homologous series, a measurement of relative axial spreading, were similar (0.28-0.39), despite the wide range of log P values (0.02-2.23) among them. The similarity between the dispersion number for each barbiturate and that for reference markers (erythrocytes, albumin, and water) suggests that the relative axial spreading of these barbiturates is determined primarily by the heterogeneity of the hepatic vasculatory system.

Animals↗