Biomedical subjects
Publications and source records attributed to Y Kono.
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Hydroxylamine is a strong inhibitor of the Mn-catalase of Lactobacillus plantarum in the presence of hydrogen peroxide [Kono, Y., and Fridovich, I. (1983) J. Biol. Chem. 258, 13646-13648]. In the presence of CuCl2 the Mn-catalase was rapidly inactivated by hydroxylamine without the addition of hydrogen peroxide. FeSO4 and MnCl2 were approximately 10% and 4% as effective as was CuCl2. Under anaerobic conditions, the inactivation did not occur. The chelating agents such as EDTA and histidine completely prevent the inactivation. These results indicate that the hydrogen peroxide produced during the autooxidation of hydroxylamine catalyzed by CuCl2 participates in the CuCl2-dependent inactivation by hydroxylamine.
Acute bracken fern toxicity in a calf was reproduced with ptaquiloside, a norsesquiterpene glucoside, isolated from the boiling water extract of bracken fern. Ptaquiloside was dissolved in 500 ml of saline and administered by drench at increasing dosages for six days out of every seven for the following periods: 400 mg/day for 24 days, 800 mg/day for 14 days and 1600 mg/day for four days. Neutrophilic granulocytes began to decrease markedly around 50 days after the start of the experiment, and granulocytopenia continued for a further 35 days until the autopsy, despite the discontinuance of ptaquiloside administration. Thrombocytes showed a relatively slow depression and reached 1 X 10(5)/mm3 at the lowest level. The calf was autopsied 86 days after the start of administration of ptaquiloside. Sternal bone marrow was found to be mostly replaced with fat marrow and only small foci of erythropoietic cells and a small number of megakaryocytes remained.
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The Mn-catalase of Lactobacillus plantarum was inactivated when exposed to NH2OH plus H2O2, an effect which was not reversed by dialysis. N-Methylhydroxylamine was approximately 1% as effective as was NH2OH, while O-methylhydroxylamine was not detectably active in this regard. Approximately 40% of the lost activity could be restored by dithionite or by O-2, whereas other reductants such as ethanol, ascorbate, or nitrite were without effect. Oxidants such as persulfate and ferricyanide also failed to reactivate the enzyme. The active enzyme was inactivated, to an apparent limit of 50%, by an enzymic or photochemical flux of O-2 and this was entirely prevented by superoxide dismutase. The catalytic cycle of the enzyme is thought to involve the trivalent and pentavalent forms of the active site Mn; while inactivation by H2O2 + NH2OH appears to be due to conversion to the quadrivalent state. Partial bleaching of the enzyme by H2O2 and the nearly complete bleaching caused by NH2OH + H2O2 are in accord with this interpretation. The enzyme was unaffected by 2.0 mM EDTA, thiourea, o-phenanthroline, alpha, alpha'-dipyridyl, 8-hydroxyquinoline, diethyldithiocarbamate, thiourea, hydrazine, phenylhydrazine, isoniazid, semicarbazide, sulfite, nitrite, or sulfide, all at pH 7.0.
The nonheme, or pseudo, catalase of Lactobacillus plantarum has been purified to homogeneity. This enzyme is pink in concentrated solutions and has a molecular weight of 172,000 +/- 4,000. It is composed of six noncovalently associated subunits of molecular weight 28,300 +/- 600. This pseudocatalase contains 1.12 +/- 0.37 atoms of manganese per subunit. Fe, Co, Cu, and Zn, if present at all, were at less than 0.1 atom per subunit. At pH 7.0 and at 25 degrees C the Km for H2O2 is 250 mM and the turnover number at Vm was 3.9 x 10(5) mol of H2O2 per mol of enzyme per s. The optical spectrum of pseudocatalase is similar to that of the manganese superoxide dismutase and indicates the presence of Mn(III) in the resting enzyme. Pseudocatalase does not exhibit superoxide dismutase activity nor does the manganese-containing superoxide dismutase exhibit catalase activity. This pseudocatalase is stable to freezing and thawing and lost only 40% of its activity when heated to 80 degrees C for 5 min. Strains of L. plantarum which contain pseudocatalase did not accumulate H2O2 in the growth medium.
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Five foetuses at varying stages of gestation were recovered from cows showing clinical signs of infection with bovine leukaemia virus (BLV). No pathological changes were found in the foetuses although BLV was isolated from 2 of these foetuses. No antibody to BLV could be detected by virus-neutralisation or immunodiffusion (ID) techniques in these two foetuses, although neutralising antibody alone was detected in one of the other 3 foetuses which were all negative for virus.
It previously had been proposed that the host-selective toxin of Helminthosporium maydis race T consists of a series of unusual linear (C(35) to C(45))polyketols, of equal toxicity on a weight or molar (10(-8)-10(-9)) basis. Previous laboratory synthesis of T-toxin analogs was limited to shorter (C(15) to C(26)) versions which possessed the requisite specificity for susceptible corn (Zea mays) but were less toxic on a weight or molar (10(-6)-10(-7)) basis. In the present study, a C(41) analog with four beta-ketol units spaced by CH(2) bridges as in native toxin has been synthesized. On a weight or molar basis, it is as effective as native toxin or its purified components in stimulating NADH oxidation of mitochondria from susceptible corn, thus providing firm evidence for the correctness of the proposed structures of T-toxin. Additional support derives from the observation that C(24) and C(26) analogs with -(CH(2))(4)- and -(CH(2))(6)- bridges between ketol groups are not as effective in stimulating NADH oxidation as are C(23) and C(25) analogs with the -(CH(2))(3)- and -(CH(2))(5)- bridges of native T-toxin.It was calculated that a single molecule of the C(41) analog is at least 300 times more effective in stimulating mitochondrial oxidation than a molecule of the C(23) or C(25) analogs. This emphasizes the importance of chain length for toxicity, perhaps through perturbation of membrane functions of mitochondria and/or chloroplasts.
A strain of Lactobacillus plantarum which was unable to produce manganese (Mn)catalase (ATCC 8014) grew somewhat more rapidly and to a slightly higher plateau density than did an Mn catalase-positive strain (ATCC 14421), and this was the case during aerobic or anaerobic growth. However, when maintenance of viability was measured during the stationary phase of the growth cycle, the advantage provided by Mn catalase was obvious. Thus, the viability of ATCC 14431 was undiminished over 21 h of aerobic incubation, during the stationary phase, whereas that of ATCC 8014 decreased by seven orders of magnitude. Addition of catalase to the medium or growth in the presence of hemin, which allows catalase synthesis, protected ATCC 8014 against this loss of viability. Suppression of Mn catalase within ATCC 14431 by treatment with NH2OH caused the cells to lose viability when exposed to 4 mM H2O2.
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A modified syncytium-induction inhibition test which is more sensitive than the immunodiffusion test, was developed using rabbit complement. In this test, fetal lamb kidney cells continuously infected with bovine leukemia virus were used as effector cells, and the CC81 cat cells transformed with murine sarcoma virus, were used as indicator cells. The syncytium-induction inhibition effect of anti-bovine leukemia virus serum was enhanced significantly by the addition of rabbit complement. The syncytium-induction inhibition titers had a statistically significant correlation with the immunodiffusion titers and were four to 64 times higher than immunodiffusion titers. In 12 experimentally infected cattle, the syncytium-induction inhibition test detected the antibodies earlier than the immunodiffusion test and continuously detected them when immunodiffusion antibody changed to negative. In the 81 sera from naturally infected herds, 35 (43.2%) were positive by the immunodiffusion test and 55 (67.9%) by the syncytium-induction inhibition test.
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