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Biomedical subjects

J Sakurai

Publications and source records attributed to J Sakurai.

At least 55 records · Page 3Linked to original sources
PubMed1995

Lethal and dermonecrotic activities of Clostridium perfringens lota toxin: biological activities induced by cooperation of two nonlinked components.

The effect of separate injections of two components of Clostridium perfringens iota toxin, designated Ia and Ib components, on the biological activities of the toxin was investigated. The intravenous injection of one component within 120 min after the injection of the other component killed mice. The activity of iota toxin was abolished by anti-Ia or anti-Ib antiserum. On the other hand, when Ib component was intravenously administered to mice given anti-Ia antiserum within 120 min after the intravenous injection of Ia component, the lethal activity was completely neutralized, but when Ia component was injected into mice that were given anti-Ib antiserum over 5 min after the injection of Ib component, the activity was not neutralized. The separate injections of Ia and Ib components in skin of guinea pigs indicated dermonecrosis at the injection site of Ib components, but not at the site of Ia components. Furthermore, when one component was intradermally injected in guinea pigs and then the other intraperitoneally, the dermonecrotic activity of the toxin was observed at the intradermal injection site of Ib component, but not at that of Ia component. From the data, it appears that the lethal and dermonecrotic activities of iota toxin are initiated by the binding of Ib component to specific sites on tissues.

ADP Ribose Transferases↗
PubMed1995

Protective effect of thromboxane synthetase inhibitor on hypertensive renal damage in Dahl salt-sensitive rats.

1. The effects of OKY-046, a specific thromboxane (TX) synthetase inhibitor, on blood pressure, urinary excretion of TX and its release from blood platelets and renal papilla, and pathological change of glomeruli were evaluated in Dahl salt-sensitive rats. 2. Average daily intakes of OKY-046-treated rats were 0.93 mg/kg (low dose), 9.8 mg/kg (moderate dose), and 88 mg/kg (high dose). 3. Systolic blood pressure tended to decrease by 6.3, 11.4, and 10.9% in three OKY-treated groups. 4. OKY-046 suppressed the release of TX from platelets in a dose-dependent fashion. Both TX in urine and released from renal papilla decreased in OKY-treated groups with moderate and high dose. OKY-046 resulted no change in urinary excretion or release from renal papilla of prostaglandin E2 or 6-keto-prostaglandin F1alpha. 5. Glomerular sclerosis score decreased significantly in both groups treated with moderate and high doses of OKY-046. 6. An inhibition of renal TX synthesis by TX synthetase inhibitor has a protective effect on the development of hypertensive renal damage with minor antihypertensive effect in Dahl salt-sensitive rats.

Animals↗
PubMed1995

Site-directed mutagenesis of histidine residues in Clostridium perfringens alpha-toxin.

Mutagenesis of H-68 or -148 in Clostridium perfringens alpha-toxin resulted in complete loss of hemolytic, phospholipase C, sphingomyelinase, and lethal activities of the toxin. These activities of the variant toxin at H-126 or -136 decreased by approximately 100-fold of the activities of the wild-type toxin. Mutation at H-46, -207, -212, or -241 showed no effect on the biological activities, indicating that these residues are not essential for these activities. The variant toxin at H-11 was not detected in culture supernatant and in cells of the transformant carrying the variant toxin gene. Wild-type toxin and the variant toxin at H-148 bound to erythrocytes in the presence of Ca2+; however, the variant toxins at H-68, -126, and -136 did not. Co2+ and Mn2+ ions stimulated binding of the variant toxin at H-68, -126, and -136 to membranes in the presence of Ca2+ and caused an increase in hemolytic activity. Wild-type toxin and the variant toxins at H-68, -126, and -136 contained two zinc atoms in the molecule. Wild-type toxin inactivated by EDTA contained two zinc atoms. These results suggest that wild-type toxin contains two tightly bound zinc atoms which are not coordinated to H-68, -126, and -136. The variant toxin at H-148 possessed only one zinc atom. Wild-type toxin and the variant toxin at H-148 showed [65Zn]2+ binding, but the variant toxins at H-68, -126, and -136 did not. Furthermore, [65Zn]2+ binding to wild-type toxin was competitively inhibited by unlabeled Zn2+, Co2+, and Mn2+. These results suggest that H-68, -126, and -136 residues bind an exchangeable and labile metal which is important for binding to membranes and that H-148 tightly binds one zinc atom which is essential for the active site of alpha-toxin.

Bacillus subtilis↗
PubMed1994

Roles of the carboxy-terminal region of Clostridium perfringens alpha toxin.

Treatment of Clostridium perfringens alpha toxin with aminopeptidase resulted in no effect on various activities of the toxin. Aminopeptidase did not hydrolyze the native toxin or the toxin treated with urea in the presence of EDTA. Treatment with carboxypeptidase for 30 min resulted in a 75% decrease in these activities. Incubation of the native toxin with carboxypeptidase for 30 min released approximately 15 amino acids from the C-terminus of the toxin. The biological activities of a mutant toxin lacking 20 C-terminal residues of the toxin (AT1-350) showed about 59-87% of the activity of native toxin. The mutant toxin showed partial antigenic identity with the native toxin. These data suggest that the C-terminal domain contributes to maintaining the active form of the toxin.

Aminopeptidases↗
PubMed1994

Elevated expression of the Cyp1a2 gene in the presence of nicotinamide by adult mouse hepatocytes in primary culture.

Effects of nicotinamide on expression of Cyp1a1 and Cyp1a2 genes were investigated in adult C57BL/6NCrj mouse hepatocytes in primary culture. The cells were cultivated for up to 8 days as monolayers or spheroids (multicellular aggregates), respectively, on collagen-coated or noncoated dishes. CYP1A1 mRNA was prominently induced after exposure to 3-methylcholanthrene (MCA) throughout the observation period with either type of culture. In monolayer-cultured cells, substantial induction of CYP1A2 mRNA by MCA was observed only at day 1 of cultivation, followed by a decrease to very low levels thereafter. In contrast, prominent elevation of both mRNA species in spheroid culture was observed throughout the 8-day experimental period. In the presence of nicotinamide, the decrease in expression of CYP1A2 mRNA in monolayer-cultured hepatocytes was restored concentration-dependently and at 10 mM nicotinamide the induced amounts were equivalent to those observed in spheroid cells. Nicotinamide also elevated CYP1A2 mRNA expression in spheroid culture, but in both cases induction of CYP1A1 mRNA decreased. Constitutive expression of CYP1A2 mRNA in monolayer culture rapidly decreased with increasing culture period, but addition of nicotinamide likewise inhibited the decrease. Nicotinamide also restored considerable expression of CYP1A2 mRNA when not present from the start of cultivation, but added 24 h before. Activities of aryl hydrocarbon hydroxylase (AHH) and acetanilide-4-hydroxylase (AAH) were elevated with either type of culture after treatment with MCA and the presence of nicotinamide further increased the AAH, resulting in an increment in the activity ratio of AAH vs AHH. Intracellular contents of NAD were considerably elevated by addition of nicotinamide. However, isonicotinamide, which is not converted to NAD in the cell, also elevated CYP1A2 mRNA expression prominently. Furthermore, NAD contents in spheroid culture were not higher than those in monolayer culture. These observations indicate that the presence of nicotinamide in the medium restores constitutive and inducible expression of Cyp1a2 gene, independent of NAD, and thus the compound is useful for studying the underlying mechanism of regulation of this gene in adult mouse hepatocytes in monolayer culture.

Animals↗
PubMed1994

Regulation of Clostridium perfringens alpha-toxin-activated phospholipase C in rabbit erythrocyte membranes.

The rapid phosphatidic acid (PA) formation induced by Clostridium perfringens alpha-toxin was stimulated by AlF4- in rabbit erythrocyte membranes. GTP[gamma S] [guanosine 5'-O-(3-thiotriphosphate)] stimulated the rapid 1,2-diacylglycerol formation and inositol 1,4,5-trisphosphate release induced by the toxin. On the other hand, treatment of erythrocyte lysates with phorbol 12-myristate 13-acetate (PMA) resulted in inhibition of toxin-induced PA production, and long-term PMA or 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) treatment of the lysates led to stimulation of PA formation. Furthermore, treatment of erythrocytes with the toxin caused an increase of protein kinase C activity in membrane fractions. The results suggest that toxin-induced PA formation is mediated by endogenous phospholipase C regulated through GTP-binding protein and protein kinase C in rabbit erythrocytes.

Animals↗
PubMed1994

Cardiac pheochromocytoma. A case report and review of the literature.

A case of intrapericardial pheochromocytoma which secreted predominantly norepinephrine is reported. A tumor at the posterior wall of the left atrium was demonstrated by computed tomographic and magnetic resonance imaging scan. Tumor blush arising from the left circumflex branch was visualized by coronary angiography. The tumor (4 x 3.5 x 2 cm) was resected with adherent atrial wall and the defect reconstructed with the patients own pericardium under general anesthesia with artificial cardiopulmonary bypass. His subsequent postoperative recovery was uneventful. At the time of discharge, 8 weeks after operation, his blood pressure and plasma norepinephrine remained normal. The value of magnetic resonance imaging scan for the topographic diagnosis of cardiac pheochromocytoma is emphasized.

Adult↗
PubMed1993

Effect of drugs acting on the central nervous system on the lethality in mice of Clostridium perfringens epsilon toxin.

Lethal activity of Clostridium perfringens epsilon toxin was significantly reduced by the prior administration of barbiturates. Phenothiazine derivatives such as chlorpromazine and trifluoperazine and butyrophenone derivatives such as haloperidol and spiperone delayed the lethal effects in mice. Reserpine completely protected mice against the toxin when 10 mg/kg of the drug was administered 24 hr before the injection of the toxin, but did not protect when the same dose of the drug was given within 60 min before the injection of the toxin. Diazepam, apomorphine and gamma-butyrolactone also resulted in a significant increase in the time to death after the toxin. On the other hand, atropine, diphenhydramine, chlorpheniramine and verapamil provided no protection against the toxin. The administration of the toxin resulted in a significant decrease of dopamine levels in the brain, but no effect on levels of epinephrine and norepinephrine. The data suggest that drugs which directly or indirectly inhibit release and receptors of dopamine may lessen the lethal effects of epsilon toxin in mice.

4-Butyrolactone↗
PubMed1993

Age dependence of O6-methylguanine-DNA methyltransferase activity and its depletion after carcinogen treatment in the teleost medaka (Oryzias latipes).

O6-Methylguanine-DNA methyltransferase (O6-MT) is considered to play an important role in the repair of DNA lesions induced by alkylating carcinogens in a wide range of animals. The activity of O6-MT was compared in liver extracts from the teleost medaka (Oryzias latipes) at various ages (3-5 years old) reared under natural conditions. O6-MT activity decreased significantly with advancing age. When medaka were exposed continuously to the alkylating agent methylazoxymethanol (MAM) acetate at levels of 0.1, 0.15 and 0.3 ppm in water, O6-MT activity was markedly reduced from days 1 to 7, with a slight increase thereafter. Furthermore, when fish were exposed to MAM acetate at levels of 1-2 ppm for 1 h and then maintained in normal tap water, O6-MT activity remained suppressed for 2 weeks, followed by a partial recovery.

Aging↗
PubMed1993

Effect of Clostridium perfringens epsilon toxin on rat isolated aorta.

The effect of Clostridium perfringens epsilon toxin on rat isolated aorta was investigated. The toxin caused contraction of the isolated aorta in a dose-dependent manner. The toxin induced no contraction of the isolated aorta in low-Na medium and of the tissue stored at 4 C for 7 days. However, tetrodotoxin (TTX) had no effect on the toxin-induced contraction. The toxin-induced contraction was significantly inhibited by phentolamine and prazosin, but did not by atropine, mecamylamine, chlorpheniramine and methysergide. These data suggest that the toxin-caused contraction is mediated through nervous system in rat isolated aorta.

Animals↗
PubMed1993

Cell-density-dependent expression of Cyp1a2 gene in monolayer-cultured adult mouse hepatocytes.

Expression of Cyp1a1 and Cyp1a2 genes was investigated in adult C57BL/6NCrj mouse hepatocytes for up to 5 days after transfer to monolayer culture. CYP1A1 mRNA was substantially induced by treatment with 3-methylcholanthrene during the observation period, independently of the seeded cell density. However, expression of CYP1A2 mRNA was dependent on cell density and was higher in cells cultivated at lower density. With increasing culture period the expression was decreased, so that only negligible levels were evident by day 5, and reduced expression of constitutive and induced CYP-1A2 mRNA became apparent earlier in more densely seeded cells. This was not related to differences in numbers of inducer molecules per cell. While mouse hepatocytes incorporated tritium-labeled thymidine under the given culture conditions, induction of expression of the two Cyp1a genes did not show any direct relationship with DNA synthesizing activity. These observations suggest some role for Cyp1a2 during changes in physiological state.

Animals↗
PubMed1993

Activation of Cyp1a1 and Cyp1a2 genes in adult mouse hepatocytes in primary culture.

Expression of Cyp1a1 and Cyp1a2 genes was investigated in adult C57BL/6NCrj mouse hepatocytes in primary culture for up to 5 days. When the cells were cultivated as monolayers on collagen-coated dishes, CYP1A1 mRNA species were prominently induced after treatment with 3-methylcholanthrene (MCA) throughout the observation period. Substantial induction of CYP1A2 mRNA by MCA was also observed at day 1 of cultivation, followed by a decrease to very low levels thereafter. In contrast, when cultivated on non-coated dishes, the hepatocytes formed multicellular aggregates (spheroids) and prominent induction of both mRNA species was found for up to 5 days. Constitutive expression of CYP1A2 mRNA in spheroid culture was maintained throughout the observation period, whereas that in monolayer culture decreased rapidly. The time-course of the induced CYP1A2 mRNA amounts after the treatment with MCA or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) followed the same pattern as that of CYP1A1 mRNA. Expressed amounts of CYP1A1 or CYP1A2 mRNA in spheroid culture were higher than or similar to the levels in the case of in vivo production, respectively. Induction of both mRNA species was also observed in hepatocytes from nonresponsive DBA/2NCrj mouse in spheroid culture, but the expressed amount after MCA treatment was far smaller than for C57BL/6NCrj cells, despite equivalent expression in the two strains after TCDD. Activities of aryl hydrocarbon hydroxylase (AHH) and acetanilide 4-hydroxylase (AAH) were elevated with either type of cultivation after treatment with MCA or TCDD. Ratios of AAH to AHH were not changed between the two cultures after 24 h treatment. However, the ratios in spheroid culture after 48 h treatment increased, whereas they did not change in monolayer culture. The present observations indicate that the spheroid culture is more suitable than the monolayer system for studying the mechanism of Cyp1a2 gene expression in adult mouse hepatocytes.

Animals↗
PubMed1993

Evidence for coupling of Clostridium perfringens alpha-toxin-induced hemolysis to stimulated phosphatidic acid formation in rabbit erythrocytes.

When rabbit erythrocytes were exposed to low concentrations of Clostridium perfringens alpha-toxin, hot-cold hemolysis was observed. The toxin induced production of phosphatidic acid (PA) in a dose-dependent manner when incubated with erythrocytes at 37 degrees C. When erythrocyte membranes were incubated with the toxin and [gamma-32P]ATP in the presence or absence of ethanol, [32P]PA formation was maximal within 30 s, then sharply decreased, and began again after 5 min of incubation. Ethanol had no effect on the early appearance (at approximately 5 min) of PA formation induced by the toxin but significantly inhibited formation of PA over 10 min of incubation. Treatment of erythrocyte membranes with alpha-toxin resulted in the biphasic formation of 1,2-diacylglycerol and PA as well as an increase of inositol-1,4,5-trisphosphate (IP3) and decrease of phosphatidylinositol-4,5-bisphosphate (PIP2) within 30 s. Neomycin inhibited the toxin-induced increase in turbidity of egg yolk suspensions but did not inhibit the toxin-induced hemolysis of intact erythrocytes. On the other hand, neomycin inhibited the toxin-induced hemolysis of saponin-treated erythrocytes. In addition, neomycin inhibited PA formation induced by the toxin in erythrocyte membranes. IP3 was released by incubation of PIP2 with erythrocyte membranes but not by incubation of PIP2 with the toxin. The toxin stimulated the membrane-induced release of IP3 from PIP2. These data suggest that the toxin-induced hemolysis is dependent on the action of phospholipase C in erythrocyte membranes.

Animals↗
PubMed1993

Molecular genetic analysis of beta-toxin of Clostridium perfringens reveals sequence homology with alpha-toxin, gamma-toxin, and leukocidin of Staphylococcus aureus.

Oligonucleotide probes designed on the basis of the N-terminal sequence of Clostridium perfringens beta-toxin were used to isolate the encoding gene (cpb). The nucleotide sequence of cpb was determined, and on the basis of DNA hybridization experiments it was shown that the gene is found only in type B and C strains of C. perfringens. The deduced amino acid sequence of the beta-toxin revealed homology with the alpha-toxin, gamma-toxin, and leukocidin of Staphylococcus aureus. The beta-toxin purified from C. perfringens appeared to exist in monomeric and multimeric forms. Recombinant beta-toxin, produced in Escherichia coli, appeared to be mainly in the multimeric form.

Amino Acid Sequence↗
PubMed1993

[A case of acute postinfarction mitral regurgitation and cardiogenic shock caused by a total rupture of the papillary muscle].

We report a case of mitral regurgitation caused by a total rupture of the posterior papillary muscle that had occurred after acute myocardial infarction. A 72-year-old woman was transferred to our hospital for cardiogenic shock. Echocardiogram revealed massive mitral regurgitation and prolapse of posterior mitral leaflet presumably due to a rupture of a papillary muscle. Cardiac catheterization demonstrated a total occlusion in the segment 2 of the right coronary artery. She had developed progressively increasing heart failure even though the patient had received a successful PTCA for a total occlusion of the right coronary artery. She underwent an emergency mitral valve replacement with preservation of the posterior leaflet using a SJM prosthetic valve. Intraoperative findings were confirmative of total rupture of the posterior papillary muscle. A postoperative course was uneventful. This case is the seventh case which has been reported as the successful operation of a total rupture of the papillary muscle in Japan.

Aged↗
PubMed1992

Altered regulation of Cyp1a-1 gene expression during cultivation of mouse hepatocytes in primary culture.

Alterations in Cyp1a-1 gene expression in adult C57BL/6 mouse hepatocytes were followed after transferring them to primary culture during the initial 5 days. Changing the medium to a fresh one was associated with considerable amounts of Cyp1a-1 gene mRNA with a peak at around 6 hr after the medium change, followed by a decrease to negligible levels 24 hr later. Treatment of hepatocytes with cycloheximide increased the medium change-associated mRNA expression, the levels being equivalent to those observed after treatment with 3.2-25.6 nM 3-methylcholanthrene plus cycloheximide. With increasing length of culture period, cycloheximide-aided enhancement of the medium change-associated mRNA transcription increased. Although the chemical alone did not induce Cyp1a-1 gene transcripts in hepatocytes at day 1 or 2 of cultivation, for which medium had been changed 24 hr previously, prominent induction of transcripts was evident at later periods, the levels being elevated in accordance with length of time in culture. To examine whether or not the mRNA transcribed under these culture conditions was translatable, the cells were treated with actinomycin D after washing out the cycloheximide, in order to inhibit degradation of the generated mRNA (Nemoto N and Sakurai J, Carcinogenesis 12: 2115-2121, 1991). After these procedures significant elevation of aryl hydrocarbon hydroxylase activity was observed in hepatocytes, the rise being well correlated with elevated levels of mRNA transcripts. The observations suggest that the Cyp1a-1 gene might be expressed at low levels during the initial phase of cultivation of mouse hepatocytes in primary culture. Whether this expression might be essential for mouse hepatocytes to adapt to culture conditions is unclear. The findings do suggest, however, that superinducibility of the gene expression after cycloheximide treatment might be a result of a regulatory mechanism operating after adaptation to culture.

Animals↗