Changes in lipids in liver and serum of rats fed a histidine-excess diet or cholesterol-supplemented diets

The influence of dietary excess (5%) L-histidine on serum and liver lipids was examined in rats. Feeding a histidine-excess diet for 3, 6, 14 or 30 days caused growth retardation, hepatomegaly and decreased liver lipids throughout the period of the experiment. Hypercholesterolemia was observed after feeding a histidine-excess diet for 6 days; then serum cholesterol continuously increased for 30 days. Serum triglyceride on day 30 in rats fed the histidine-excess diet showed a significant decrease compared to rats fed the basal diet. Serum phospholipids of rats fed the histidine-excess diet for 7 or 14 days showed a significant increase compared to rats fed the basal diet. When rats were fed a basal, histidine-excess or cholesterol-supplemented diet (0.5% and 1.0% cholesterol) for 6 days, the distribution of serum high density (HDL), low density (LDL) and very low density lipoprotein cholesterol in rats fed the histidine-excess diet was similar to that of rats fed the basal diet, whereas LDL-cholesterol increased and HDL-cholesterol decreased in rats fed the cholesterol-supplemented diet.

Demonstration of herpes simplex 1 virus antigen mouse brain after fixation

The effects of several fixatives and fixation periods on recovery of viral antigen by indirect immunofluorescence (IF) and indirect immunoperoxidase (IP) were examined in mouse brains infected with type-1 herpes simplex virus. In 10% formalin, the sensitivity of antigen detection by IF decreased after one month fixation and viral antigen was barely detectable after fixation for three months. But in 10% buffered formalin antigenicity was not lost after six months. Similar effects were obtained by IP; however, specimens fixed in 10% formalin for three and six months showed positive reactions. Viral antigen was detectable without enzyme digestion in paraffin materials fixed in Bouin's, Carnoy's and Dubosq-Brazil solutions, but when treated with proteolytic enzyme for three hours, antigen could not be detected by either IF or IP. Ten per cent buffered formalin, Bouin's or Dubosq-Brazil solutions are recommended as fixatives for retrospective immunohistochemical and histopathological studies of viral infection in autopsy and biopsy materials.

Comparative studies on the hypercholesterolaemia induced by excess dietary tyrosine or polychlorinated biphenyls in rats

1. The effects of dietary polychlorinated biphenyls (PCB) and excess tyrosine on serum and liver lipids, urinary ascorbic acid and catecholamines were compared in male Wistar rats. 2. Serum levels of cholesterol, urinary ascorbic acid, norepinephrine, epinephrine, dopamine and histamine were significantly increased in rats given either PCB or excess tyrosine. 3. The hypercholesterolaemia induced by PCB or excess tyrosine was blocked by the adrenergic alpha-blocker, phenoxybenzamine. 4. The present results suggest causal interrelations between the hypercholesterolaemia induced by dietary PCB or excess tyrosine and the secretion of catecholamines.

Inquiries into the structure-function relationship of ribonuclease T1 using chemically synthesized coding sequences

The genes for ribonuclease T1 and its site-specific mutants were chemically synthesized and introduced to Escherichia coli. All enzymes were fusion products produced by joining the synthetic gene at specific restriction sites to the synthetic gene for human growth hormone in a plasmid containing the E. coli trp promoter. The fusion protein from this plasmid contained 66% of the amino-terminal sequences of the human growth hormone, which were recognizable immunologically. RNase T1 or its mutants were cleaved from the fusion protein with cyanogen bromide. The synthetic RNase T1 endowed with the revised wild-type triad Gly-Ser-Pro, residues 71-73, was fully functional, readily hydrolyzing pGpC bonds, whereas a mutant enzyme having the originally reported, erroneous triad Pro-Gly-Ser was totally inactive. Various amino acid substitutions were also introduced to the guanosine recognition region comprised of residues 42-45, Tyr-Asn-Asn-Tyr. Substitution of either of the tyrosine residues noted above with phenylalanine had no dramatic effect on the enzyme's function. Replacement of asparagine-43 with arginine or alanine also caused only a small change in the hydrolyzing activity--a mutant enzyme maintained greater than 50% of the wild-type activity. In sharp contrast, when aspartic acid or alanine was substituted for asparagine-44, the activity was dramatically reduced to a few percent of the wild-type activity.

Stereo-selective interaction of enantiomers of diniconazole, a fungicide, with purified P-450/14DM from yeast

R(-) isomer of diniconazole [S-3308L, (E)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-l-yl)-1-+ ++penten-3-ol], a newly developed fungicide strongly inhibited lanosterol 14 alpha-demethylation catalyzed by a yeast cytochrome P-450 (P-450/14DM). On the other hand, S(+) isomer of diniconazole was a weaker inhibitor for P-450/14DM. The R(-) isomer combined with both ferric and ferrous P-450/14DM and interfered binding of CO to the cytochrome. The S(+) isomer also interacted with both forms of P-450/14DM but the absorption spectra of the S(+)-diniconazole complexes were different from those of the R(-)-diniconazole complexes. Furthermore, S(+) isomer did not significantly interfere the binding of CO to P-450/14DM. These observations suggest that P-450/14DM discriminates enantiomers of diniconazole and the R(-) isomer is more favorably fit for the active site of the cytochrome.

Effects of excess dietary tyrosine or certain xenobiotics on the cholesterogenesis in rats

Comparison of the effects of excess dietary tyrosine, DDT, chlorobutanol (Chloretone) or butylated hydroxyanisole (BHA) on serum cholesterol, hepatic activities of the rate-limiting enzyme of cholesterol synthesis,3-hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.34) and in vivo rates of the hepatic cholesterol synthesis measured by 3H2O incorporation were investigated in rats. Serum cholesterol concentration was significantly higher in rats fed the DDT, chlorobutanol, BHA or excess tyrosine diets than in rats fed the control diet for 7 days. Serum cholesterol concentration remained higher compared to control rats when excess tyrosine was fed for 21 d. When rats were fed a basal diet after feeding a tyrosine excess diet for 2 wk, liver weight and serum cholesterol level returned to normal within 7 d. The incorporation of 3H2O into liver cholesterol and the activity of liver 3-hydroxy-3-methylglutaryl coenzyme A reductase were greater in rats fed excess tyrosine or certain xenobiotics than in control rats. Present results suggested that the increase in serum cholesterol concentration due to excess dietary tyrosine or certain xenobiotics is mainly attributable to the stimulation of liver cholesterol synthesis.

Evidence for the contribution of a sterol 14-reductase to the 14 alpha-demethylation of lanosterol by yeast

Lanosterol was converted to a 14-demethylated metabolite, 4,4-dimethylzymosterol by Saccharomyces cerevisiae microsomes. This metabolism was mediated by a cytochrome P-450 (P-450/14DM). However, a reconstituted system consisting of P-450/14DM and its reductase converted lanosterol to the 14-desaturated derivative of 4,4-dimethylzymosterol, 4,4-dimethyl-5 alpha-cholesta-8, 14,24-trien-3 beta-ol (trienol). When AY-9944 was added to the reaction system with the microsomes, the trienol was formed with corresponding decrease in 4,4-dimethylzymosterol. These observations indicate that the 14 alpha-demethylation of lanosterol by yeast microsomes occurs sequentially via the trienol. Reduction of the trienol to 4,4-dimethylzymosterol is mediated by an AY-9944-sensitive reductase.

Proliferating sites of Rickettsia tsutsugamushi in mice by different routes of inoculation evidenced with immunofluorescence

The sites of multiplication of Rickettsia tsutsugamushi in mice by different routes of inoculation were investigated by means of immunofluorescence. R. tsutsugamushi (Kato, Karp, Gilliam and Miyake strains) inoculated by intraperitoneal route multiplied significantly in mesothelial and inflammatory cells of the peritoneal cavity of DDD and BALB/c (nu/nu) mice. The rickettsial growth was not detected in parenchymal cells of the liver, spleen, kidneys and lymph nodes of DDD mice, but slightly observed in those cells of the nude mice. When inoculated by subcutaneous route, the rickettsial antigens were detected in small amount in the peritoneal mesothelial and inflammatory cells, whereas a marked proliferation of R. tsutsugamushi was demonstrated in liver cells, Kupffer cells, and endothelial cells of the sinus of spleen and lymph nodes. A specific antibody to Karp strain, administered intraperitoneally, prevented effectively rickettsial growth in the peritoneal cavity of BALB/c (nu/nu) mice challenged intraperitoneally, 6 hours later, with Miyake strain (Karp type) and the animals were infected after a long-term incubation period showing the findings of rickettsial localization similar to that in subcutaneously inoculated animals. This fact suggests a partial involvement of humoral immunity in resistance of mice against R. tsutsugamushi infection. The potential importance of these findings in experimental infection with R. tsutsugamushi was discussed.

Effects of buthiobate, a fungicide, on cytochrome P-450 of rat liver microsomes

Effects of buthiobate (S-butyl S'-p-tert-butylbenzyl N-3-pyridyldithiocarbonimidate), a fungicide which inhibits lanosterol 14 alpha-demethylation catalyzed by a cytochrome P-450 (P-450 14DM) of yeast, on cytochrome P-450 of rat liver microsomes were studied. Buthiobate bound to limited forms of cytochrome P-450 in the microsomes with three different Kd values, 0.38, 1.56 and 13.6 microM. Buthiobate inhibited lanosterol 14 alpha-demethylase activity of the microsomes with a 50%-inhibition concentration of 0.4 microM. This concentration was comparable to the lowest Kd of buthiobate for the microsomal cytochrome P-450 and also to the 50%-inhibition concentration of the inhibitor for lanosterol 14 alpha-demethylation by yeast P-450 14DM. Buthiobate partially inhibited 7-ethoxycoumalin O-deethylase activity of the microsomes but inhibited neither benzphetamine N-demethylation nor p-nitroanisole O-demethylation. These observations suggest that cytochrome P-450s catalyzing drug oxidations are rather insensitive to buthiobate. These observations indicate that buthiobate is an unique inhibitor for hepatic microsomal cytochrome P-450 system, which inhibits cholesterol biosynthesis effectively but causes a little effect on drug oxidations.

Spectral properties of a novel cytochrome P-450 of a Saccharomyces cerevisiae mutant SG1. A cytochrome P-450 species having a nitrogenous ligand trans to thiolate

An altered cytochrome P-450 (SG1 P-450) was partially purified from Saccharomyces cerevisiae mutant SG1 which is defective in lanosterol 14 alpha-demethylation. Oxidized SG1 P-450 showed a Soret peak at 422 nm and the alpha peak was lower than the beta peak. This spectrum was considerably different from those of known low-spin P-450s, indicating a unique ligand structure of SG1 P-450. The absorption spectrum of ferric SG1 P-450 was superimposable on that of the imidazole complex of ferric P-450, suggesting the presence of a nitrogenous ligand such as histidine of the apoprotein at the 6th coordination position. SG1 P-450 was immunochemically indistinguishable from cytochrome P-450 of S. cerevisiae catalyzing lanosterol 14 alpha-demethylation (P-45014DM) but had no lanosterol 14 alpha-demethylase activity.

Yeast cytochrome P-450 catalyzing lanosterol 14 alpha-demethylation. I. Purification and spectral properties

A form of cytochrome P-450 catalyzing lanosterol 14 alpha-demethylation (tentatively called "P-450(14)DM") was purified from microsomes of semi-anaerobically grown cells of Saccharomyces cerevisiae to gel electrophoretic homogeneity. An apparent monomeric Mr = 58,000 was estimated for the purified cytochrome by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both optical and EPR spectra of oxidized P-450(14)DM are characteristic of low spin ferric heme proteins, and its reduced CO complex showed a Soret absorption peak at 447 nm. As in the case of hepatic microsomal cytochromes P-450, the ethyl isocyanide complex of reduced P-450(14)DM was in a pH-dependent equilibrium between two states having Soret peaks at 429 and 453 nm, the equilibrium being considerably shifted toward the 453-nm state. Oxidized P-450(14)DM was peculiar in that in its CD spectrum there was a negative shoulder at 425 nm and the 350- and 414-nm troughs possessed larger and relatively smaller [theta] values, respectively, than those reported for other low spin ferric cytochromes P-450. Lanosterol was the only compound which caused a Type I spectral change in oxidized P-450(14)DM. The lanosterol-induced low to high spin state change was, however, only slight even at saturating concentrations of the sterol, indicating that the lanosterol-P-450(14)DM adduct was in a spin state equilibrium.

Yeast cytochrome P-450 catalyzing lanosterol 14 alpha-demethylation. II. Lanosterol metabolism by purified P-450(14)DM and by intact microsomes

A reconstituted monooxygenase system containing a form of cytochrome P-450, termed P-450(14)DM, and NADPH-cytochrome P-450 reductase, both purified from yeast microsomes, catalyzed the conversion of lanosterol (4,4,14 alpha-trimethyl-5 alpha-cholesta-8,24-dien-3 beta-01) to a sterol metabolite in the presence of NADPH and molecular oxygen. This conversion did not occur anaerobically or when either P-450(14)DM, the reductase, or NADPH was omitted from the system. In both free and trimethylsilylated forms, this metabolite showed a relative retention time (relative to lanosterol) of 1.10 in gas chromatography on OV-17 columns. Comparison of its mass spectrum and retention time with those of lanosterol and 4,4-dimethylzymosterol (4,4-dimethyl-5 alpha-cholesta-8,24-dien-3 beta-ol) indicated that the metabolite was 4,4-dimethyl-5 alpha-cholesta-8,14,24-trien-3 beta-ol. Upon aerobic incubation of microsomes from semianaerobically grown yeast cells in the presence of NADPH and cyanide, endogenous lanosterol was converted to 4,4-dimethylzymosterol. This metabolism was inhibited by CO, metyrapone, SKF-525A, and antibodies to P-450(14)DM. It is concluded that in yeast microsomes lanosterol is 14 alpha-demethylated by a P-450(14)DM-containing monooxygenase system to give rise to 4,4-dimethyl-5 alpha-cholesta-8,14,24-trien-3 beta-ol, which is then reduced to 4,4-dimethylzymosterol by an NADPH-linked reductase.

Detection of viral antigens in formalin-fixed specimens by enzyme treatment

Enzyme treatment (protease or trypsin) was applied to formalin-fixed paraffin-embedded materials and virus-infected cultured cells to detect viral antigens by immunofluorescence. The viral antigens were demonstrated in several organs of autopsy or biopsy cases of which diagnoses had been established by immunofluorescence or virus isolation using frozen materials, or suspected on the basis of serology and/or histopathological findings. These included herpes simplex, varicella-zoster, cytomegalo, subacute sclerosing panencephalitis, progressive multifocal leukoencephalopathy, Japanese B encephalitis, measles, acute hemorrhagic conjunctivitis, Lassa and Korean hemorrhagic fever. Antigen could be recovered also in virus-infected cells (herpes simplex, measles, Lassa, Ebola, Marburg, Rift Valley, Congo and Korean Hemorrhagic fever) by enzyme treatment after periods of formalin fixation of four weeks and storage of three months. In herpes simplex virus-infected mouse brain, antigen was detected after fixation for three months in formalin.

Effects on liver and serum lipids of dietary supplements of methionine and excess lysine given to previously-starved rats

The addition of lysine hydrochloride (50 g/kg) to a diet supplemented with methionine (3 g/kg) had no effect on liver lipids when rats (Wistar and Sprague-Dawley) were fed ad lib. for 14 d. However, refeeding a diet supplemented with methionine and excess lysine hydrochloride to previously-starved rats (Wistar) for 6, 7 or 9 d, but not 3 or 4 d, resulted in liver lipid accumulation, mainly triglycerides, which was prevented by the addition of arginine, citrulline, ornithine, adenine, allopurinol or maize oil, but not by guanine, cytosine, thymine or uracil. The addition of lysine hydrochloride to a methionine-supplemented diet resulted in reduced serum triglyceride levels after refeeding for 3 or 4 d and reduced serum cholesterol levels after refeeding for 3, 4 or 6 d. Serum lipids were unaffected by refeeding the diets for 7 or 9 d. Since hepatic lipid accumulation was preceded by the decline in the level of serum triglycerides, one of the factors responsible for lipid accumulation in the liver might be reduced transport of triglycerides from the liver into the blood. When adenine and allopurinol were added to the diet supplemented with methionine and lysine hydrochloride refed for 4 d, there was an increase in serum triglycerides. However, when this diet was refed for 7 d, with the addition of arginine, citrulline, guanine, pyrimidine bases, allopurinol or maize oil, no effects on serum cholesterol and triglyceride levels were observed.

Two species of cytochrome P-450 involved in ergosterol biosynthesis of yeast

Discrimination of cytochrome P-450 involved in delta 22-desaturation of ergosta-5,7-dien-3 beta-o1 (P-450(22)-DS) from that involved in lanosterol 14 alpha-demethylation (P-450(14)-DM) in ergosterol biosynthesis was investigated with microsomes of several strains of Saccharomyces cerevisiae. In mutant N22 which is partially defective in the delta 22-desaturation, the 14 alpha-demethylation was not blocked. In contrast, mutant SG1 which is known to lack the 14 alpha-demethylation showed a significant activity of the delta 22-desaturation. The delta 22-desaturation activity was markedly increased upon aerobic adaptation of yeast cells but the 14 alpha-demethylation was not affected. Buthiobate, a specific inhibitor of P-450(14)-DM, and rabbit antibodies against P-450(14)-DM did not inhibit the delta 22-desaturation activity at all. It is evident from the obtained observations that these phenomena are not explainable in terms of NADPH-cytochrome P-450 reductase. These results indicate that P-450(22)-DS is different from P-450(14)-DM in molecular species.