Biological effects of vinyl chloride: an experimental study. (9/1604)

Plasma activities of alkaline phosphatase, (AP), transaminases and total lactate dehydrogenase (LDH) with isoenzymes were determined in mice inhaling 50 and 550 ppm vinyl chloride (VC). The animals were also autopsied and the tissue pathology was studies. The total LDH activity was elevanted in both dose groups along with a shift to cathodic enzymes. AP was increased in animals exposed to 500 ppm and transaminases were not at all changed. Enzyme changes occurred after the appearance of tumors. Alveologenic adenomas occurred in all animals at the higher dosage and in about half of the animals inhaling the lower dose. Subperitoneal and subcutaneous hemangiosarcomas were frequent in both dose groups; but especially among 50 ppm animals. Only one animal had a hemangiosarcoma of the liver. No liver fibrosis was seen. All primary subperitoneal and subcutaneous tumors were located in fat tissue. Telangiectasis was observed in two animals in the 500 ppm series. The importance of blood vessel changes in the toxicology of vinyl chloride is discussed.  (+info)

Anaerobic oxidations of cysteate: degradation via L-cysteate:2-oxoglutarate aminotransferase in Paracoccus pantotrophus. (10/1604)

Anoxic, fresh-water enrichment cultures to oxidize different organosulfonates were set up with nitrate, ferric iron or sulfate as electron acceptors. Pure cultures were easily obtained with two naturally occurring sulfonates, cysteate (2-amino-3-sulfopropionate) and taurine (2-aminoethanesulfonate), under nitrate-reducing conditions. These two sulfonates were also oxidized during reduction of iron(III), though isolation of pure cultures was not successful. One nitrate-reducing cysteate-oxidizing bacterium, strain NKNCYSA, was studied in detail. It was identified as Paracoccus pantotrophus. Eighteen sulfonates were tested, and the organism degraded cysteate, taurine, isethionate (2-hydroxyethanesulfonate), sulfoacetate or 3-aminopropanesulfonate with concomitant reduction of nitrate, presumably to molecular nitrogen. The carbon skeleton of these substrates was converted to cell material and, presumably, CO2. The amino group was released as ammonia and the sulfono moiety was recovered as sulfate. Cell-free extracts of P. pantotrophus NKNCYSA contained constitutive L-cysteate:2-oxoglutarate aminotransferase (EC 2.6.1.-) and glutamate dehydrogenase (EC 1.4.1.4). Taurine:pyruvate aminotransferase, in contrast, was inducible.  (+info)

Regulation of enzyme synthesis in the arginine biosynthetic pathway of Pseudomonas aeruginosa. (11/1604)

In Pseudomonas aeruginosa the synthesis of only two out of eight arginine biosynthetic enzymes tested was regulated. Comparisons were made between the specific activities of these enzymes in bacteria grown on arginine or on its precursor, glutamate. N2-Acetylornithine 5-aminotransferase (ACOAT), an enzyme involved in both the biosynthesis and catabolism of arginine, was induced about 14-fold during growth of the organism on arginine as the only carbon and nitrogen source, and the anabolic ornithine carbamoyltransferase (aOTC), a strictly biosynthetic enzyme, was repressed 18-fold. Addition of various carbon sources to the arginine medium led to repression of ACOAT and to derepression of aOTC. Fructose, which supported only slow growth of P. aeruginosa, had a weak regulatory effect on the synthesis of the two arginine enzymes while citrate, a good carbon source for this organism, had a strong effect. The repression of ACOAT by citrate was not relieved by adding cyclic AMP to the medium. Under a variety of growth conditions leading to different enzyme activities, a linear relationship between the reciprocal of the specific activity of ACOAT and the specific activity of aOTC was observed. This inverse regulation of the formation of the two enzymes suggested that a single regulatory system governs their synthesis. Such a view was supported by the isolation of citrate-resistant regulatory mutants which constitutively formed ACOAT at the induced level and aOTC at the repressed level.  (+info)

Effect of N-terminal alpha-helix formation on the dimerization and intracellular targeting of alanine:glyoxylate aminotransferase. (12/1604)

The unparalleled peroxisome-to-mitochondrion mistargeting of alanine:glyoxylate aminotransferase (AGT) in the hereditary disease primary hyperoxaluria type 1 is caused by the combined presence of a common Pro11 --> Leu polymorphism and a disease-specific Gly170 --> Arg mutation. The Pro11 --> Leu replacement generates a functionally weak N-terminal mitochondrial targeting sequence (MTS), the efficiency of which is increased by the additional presence of the Gly170 --> Arg replacement. AGT dimerization is inhibited in the combined presence of both replacements but not when each is present separately. In this paper we have attempted to identify the structural determinants of AGT dimerization and mitochondrial mistargeting. Unlike most MTSs, the polymorphic MTS of AGT has little tendency to adopt an alpha-helical conformation in vitro. Nevertheless, it is able to target efficiently a monomeric green fluorescent (GFP) fusion protein, but not dimeric AGT, to mitochondria in transfected COS-1 cells. Increasing the propensity of this MTS to fold into an alpha-helix, by making a double Pro11 --> Leu + Pro10 --> Leu replacement, enabled it to target both GFP and AGT efficiently to mitochondria. The double Pro11 --> Leu + Pro10 --> Leu replacement retarded AGT dimerization in vitro as did the disease-causing double Pro11 --> Leu + Gly170 --> Arg replacement. These data suggest that N-terminal alpha-helix formation is more important for maintaining AGT in a conformation (i. e. monomeric) compatible with mitochondrial import than it is for the provision of mitochondrial targeting information. The parallel effects of the Pro10 --> Leu and Gly170 --> Arg replacements on the dimerization and intracellular targeting of polymorphic AGT (containing the Pro11 --> Leu replacement) raise the possibility that they might achieve their effects by the same mechanism.  (+info)

The kynurenine metabolic pathway in the eye: studies on 3-hydroxykynurenine, a putative cataractogenic compound. (13/1604)

The rabbit lens has an elevated content of 3-hydroxykynurenine (30HKYN) in spite of a very low activity of the enzymes leading to its synthesis. The iris/ciliary body, on the contrary, has very high activity of 30HKYN synthesizing enzymes but a content of 30HKYN lower than that of the lens. These observations suggest that 30HKYN is formed in the iris/ ciliary body, released into the aqueous humor and then taken up into the lens where it may be used for the synthesis of UV filtering products. An excessive accumulation of 30HKYN in the lens has been associated with cataract formation. We found that available selective inhibitors of kynurenine hydroxylase reduced 30HKYN synthesis in both the lens and the iris/ciliary body.  (+info)

Efficacy and changes of the nonstructural 5A GENE by prolonged interferon therapy for patients with hepatitis C virus genotype 1b and a high level of serum HCV-RNA. (14/1604)

OBJECT: The aim of this study was to examine the efficacy and the changes of amino acid sequences of the interferon sensitivity-determining region (ISDR) by prolonged interferon (IFN) treatment in patients who have serum hepatitis C virus (HCV)-genotype 1b and a high level of serum HCV-RNA. METHODS: Inclusion criteria were biopsy-proven chronic hepatitis, positive HCV-RNA, and an abnormal serum aminotransferase level. Twenty-five patients received 6 MU of natural IFN-alpha daily for 8 weeks, followed by three times weekly for 40 weeks (1,056 MU). One patient was withdrawn from the study due to IFN side effects. Therefore, the remaining 24 patients (group 1) were studied the efficacy of IFN administration and changes of ISDR. As a control, 22 patients (group 2) treated with natural IFN-alpha for 24 weeks for the same period were studied retrospectively. Patients were defined as complete responders (CR) if serum HCV-RNA levels were negative for 6 months after IFN therapy. RESULTS: According to this criterion, CR was 25% (6/24) in group 1 and 9.1% (2/22) in group 2. The normalization rates of alanine aminotransferease (ALT) for six months after termination of IFN was 41% (10/24) in group 1 and 18.2% (4/22) in group 2. Regarding the changes of ISDR in patients with no CR, the change rates of ISDR were 16.7% (3/18) in group 1 and 10% (2/20) in group 2. CONCLUSION: We concluded that prolonged IFN therapy was effective for patients with HCV-genotype 1b and a high level of serum HCV-RNA.  (+info)

Prevalence and characterization of hepatitis C virus in hemodialysis patients. (15/1604)

OBJECT: Chronic hepatitis C virus (HCV) infection is common in hemodialysis (HD) patients. In the present study, the prevalence and properties of HCV in HD patients were analyzed. METHODS AND RESULTS: Of 125 HD patients, 34 (27%) were positive for antibody to HCV, and HCV-RNA was detected in 23 (68%) of the 34 patients using reverse transcription polymerase chain reaction. The HCV-RNA sequence analysis did not identify the alterations specific to HD patients with HCV, although one patient had a variant virus containing the deletion of the core gene sequence. When serial changes in the levels of HCV-RNA were evaluated in 15 patients by a branched DNA assay, the values decreased immediately after HD procedure, but returned to the baseline values 2 days after the procedure. CONCLUSION: These results indicate that HCV in HD patients is replication-competent, although a transient reduction in the levels of HCV-RNA occurs during HD.  (+info)

Involvement of branched-chain amino acid aminotransferase (Bcat1/Eca39) in apoptosis. (16/1604)

The branched-chain amino acid aminotransferase, Bcat1/Eca39, catalyzes the first step of branched-chain amino acid catabolism. Bcat1/Eca39 was originally isolated from a c-myc-induced tumor and was proven to be a direct target for c-Myc regulation. The gene is highly conserved in evolution and disruption of its yeast homolog affects cell growth. To assess the role of Bcat1/Eca39 in mammalian cells, we overexpressed Bcat1/Eca39 in murine cells and studied effects on cell growth. Overexpression of Bcat1/Eca39 had no apparent effect on the proliferation of cells grown with high serum concentrations, but under serum deprivation conditions, led to a decrease in cell viability. Cell death under these conditions displayed apoptotic features. The branched-chain keto acid, alpha-ketoisocaproate, a metabolite of leucine catabolism produced by BCAT1/ECA39, was previously found to inhibit cell growth. We show that alpha-ketoisocaproate can induce rapid apoptotic cell death. This observation suggests that the growth inhibitory effect of BCAT1/ECA39 and its apoptosis promoting effect may be mediated by the levels of the products of BCAT1/ECA39 activity, namely, branched-chain keto acids.  (+info)