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N Koga

Publications and source records attributed to N Koga.

At least 55 records · Page 3Linked to original sources
PubMed1998

Reduction of ischemic brain injury by topical application of glial cell line-derived neurotrophic factor after permanent middle cerebral artery occlusion in rats.

BACKGROUND AND PURPOSE: Glial cell line-derived neurotrophic factor (GDNF) plays important roles in the survival and recovery of some mature neurons under pathological conditions. However, the effect of GDNF in ameliorating ischemic brain injury has not been well documented. Therefore, we investigated a possible effect of GDNF on the changes of infarct size, brain edema, DNA fragmentation, and immunoreactivities for caspases after permanent middle cerebral artery occlusion (MCAO) in rats. METHODS: For the estimation of ischemic brain injury, we calculated the infarct size of MCA region and also measured the brain water content as edema formation at 24 hours after the MCAO. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick labeling (TUNEL) staining was performed for the detection of DNA fragmentation. Immunoreactivities for caspase-1 (ICE), caspase-2 (Nedd-2), and caspase-3 (CPP32) were stained. RESULTS: Both infarct size and brain edema after permanent MCAO were significantly reduced by topical application of GDNF (48% and 30% decreases, P=0.01). TUNEL staining and immunoreactivities for caspases were markedly induced at 12 hours after permanent MCAO in the vehicle-treated animals. However, the spatial distribution of those immunohistochemically positive cells was dissociative in each caspase. Induction of TUNEL staining and immunoreactivities for caspases-1 and -3 was greatly reduced with GDNF treatment, whereas the reduction of caspase-2 staining was only minimum. CONCLUSIONS: These data suggest that the reduction of infarct size and brain edema by GDNF was greatly associated with the reduction of DNA fragmentation and apoptotic signals predominantly through caspases-1 and -3 cascades.

Administration, Topical↗
PubMed1998

Clinical significance of detecting p53 protein in Burkitt lymphoma and B-cell acute lymphoblastic leukemia using immunocytochemistry.

P53 protein expression in malignant cells of five patients with Burkitt lymphoma (BL) and from two patients with B-cell acute lymphoblastic leukemia (B-ALL) was examined with anti p53 protein monoclonal antibodies PAb1801, PAb240 and p53-D07 using an immunocytochemical technique. Four of the seven patients were positive. The distribution of positive staining within the cell was predominantly in the nucleus. The reactivity of PAb240 was weaker than that of the other antibodies. In addition, three of the four positive cases showed the same abnormal karyotype; translocation (8;14) (q24;q32). All of the four positive cases died due to relapse of their primary disease. The three negative cases did not show karyotypic abnormalities and are still alive and well. In conclusion, p53 immunostaining technique may be useful for predicting the clinical outcome of B-cell malignancy.

Adolescent↗
PubMed1997

Metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl (PCB153) in guinea pig.

1. The in vitro and in vivo metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl (PCB153) in guinea pig has been studied. 2. Seven metabolites were detected in the faeces of PCB153-treated animals and three were identical to those produced by dog liver microsomes. The detection of a metabolite where a chlorine atom was shifted from the 2- to 3-position strongly suggested the involvement of 2,3-arene oxide intermediate, and evidence for the concomitant formation of a 3,4-arene oxide intermediate was provided by identifying other two minor metabolites which were dechlorinated at the 4-position. 3. In vitro studies using liver microsomes from guinea pigs revealed that the 2,3-arene oxide and 3-hydroxylation pathways are the predominant metabolic routes compared with the 3,4-arene oxide pathway. Although the guinea pig is an another species that can metabolize PCB153 mainly to the 2,3-arene oxide intermediate, the rate of formation was only about one-tenth of the dog. 4. These results indicate that the ability to form this unusual 2,3-arene oxide intermediate may not be responsible for high excretion rate of this congener. Our data also suggest that the cytochrome P450-catalysed metabolism of PCB153 in the guinea pig and dog are similar, whereas for post-cytochrome P450 metabolism, the guinea pig resembles the rabbit.

Animals↗
PubMed1997

The retardation of progression, stabilization, and regression of coronary and carotid atherosclerosis by low-density lipoprotein apheresis in patients with familial hypercholesterolemia.

The long-term effects of low-density lipoprotein (LDL) apheresis (LA) on the progression and regression of atherosclerosis were evaluated by angiographic and pathological findings as well as ultrasonography based studies, and the clinical significance of the treatment was evaluated. We studied 11 patients with familial hypercholesterolemia (FH), 2 with homozygous FH and 9 with severe heterozygous FH who received combined LA and drug therapy for a mean of 7.7 years. During the treatment period, the mean time-averaged level of LDL cholesterol was 181+/-52 mg/dl. According to the coronary angiographic results, 3 patients showed regression, 6 patients showed progression, and 2 patients showed no change. Cardiac events occurred in 6 patients. We pathologically examined at autopsy the coronary arteries of 1 FH patient who had received long-term LA therapy before death. The results revealed the process of scarring of atheromatous plaque, suggesting pathological regression correlated with the angiographic regression shown in serial angiograms taken during LA treatment. It was further suggested that the formation of an eccentric thick end wall lesion rich in collagen fiber prevented atheromatous plaque from tearing off. However, the annual progression rate of the mean maximal intima-media thickness in the common carotid artery was 0.0002 mm/year in the LA group, which was significantly lower than the mean of 0.251 mm/year seen in the control group (drug therapy only group). In the patients with heterozygous FH (9 patients), the annual progression rate was lowered to 0.0023 mm/year, suggesting regression. The findings of the present study indicate that patients with severe FH refractory to drug treatment may benefit from more aggressive cholesterol lowering treatments such as LA combined with cholesterol lowering drug therapy. The progression of atherosclerosis may be prevented, plaque may be stabilized (regressed), and clinical events may be reduced as seen with patients with non-FH hypercholesterolemia.

Arteriosclerosis↗
PubMed1996

Hamster liver cytochrome P450 (CYP2A8) as a 4-hydroxylase for 2,5,2',5'-tetrachlorobiphenyl.

Metabolism of 2,5,2',5'-tetrachlorobiphenyl (TCB) was studied using liver microsomes of hamsters and two hamster P450 isoforms, CYP1A2 and 2A8. CYP2A8 catalyzed selectively 4-hydroxylation of 2,5,2',5-TCB at a rate of 21.7 pmol/min/nmol P450. In contrast, CYP1A2 showed no activity for hydroxylation of 2,5,2',5'-TCB. Immunological study revealed that rabbit antiserum against CYP2A8 almost completely inhibited the microsomal 4-hydroxylation but that against CYP1A2 did not. It was also shown that the induction pattern of CYP2A8 protein by P450 inducer was similar to that of the 4-hydroxylase activity in hamster liver microsomes. These results suggest that CYP2A8 plays a major role in the 4-hydroxylation of 2,5,2',5'-TCB in hamster liver.

Animals↗
PubMed1996

Involvement of cytochrome b5 in the metabolism of tetrachlorobiphenyls catalyzed by CYP2B1 and CYP1A1.

The role of cytochrome b5 in the cytochrome P450 (CYP)-dependent hydroxylation of tetrachlorobiphenyl (TCB) isomers was examined using a reconstituted mixed function oxygenase (MFO) system containing purified CYP2B1 or 1A1, and rat liver microsomes. Hydroxylations of 2,2',5,5'- and 3,3',4,4'-TCBs were catalyzed mainly by CYP2B1 and 1A1, respectively, in the reconstituted MFO system and those of 2,3',4',5- and 2,3',4,4'-TCBs were mediated by both cytochrome P450 systems. The activity toward 2,2',5,5'- and 2,3',4',5-TCB was significantly increased 6.5- and 5.5-fold, respectively, by addition of cytochrome b5 in the reconstituted MFO system containing of CYP2B1. Either hydroxylation activity toward 2,3',4,4'-TCB with the CYP2B1 system was very low or decreased by addition of cytochrome b5. These results suggest that the involvement of cytochrome b5 to the hydroxylation of TCBs is dependent on the TCB congener being metabolized, and the cytochrome P450 isoform involved in its metabolism.

Animals↗
PubMed1996

Impairment of the glycolytic system and actin in baker's yeast during frozen storage.

After frozen storage for 7 d, the viability and CO2 productivity of a conventional baker's yeast strain D greatly decreased. The viability of a freeze-tolerant strain, DFT, used for the frozen dough method slightly decreased after the same storage period, while the CO2 productivity greatly decreased. The CO2 productivity and DNase I inhibitory activity of actin of the cell-free extracts prepared immediately after thawing from 7-d frozen-stored cells markedly decreased in both strains. In DFT, however, the productivity and the inhibitory activity of the cell-free extract increased when the extract was prepared after incubation of the frozen-thawed cells at 30 degrees C. The increase in the inhibitory activity first occurred and then the increase in the CO2 productivity. Gel filtration patterns of actin and glycolytic enzymes were compared between cell-free extracts of both strains. Peaks of actin and activity peaks of hexokinase and pyruvate kinase decreased in the strain D after frozen storage, but only slightly in the strain DFT. After frozen storage, phosphofructokinase activity peak shifted to a lower molecular weight in strain D.

Actins↗
PubMed1996

Role of cytochrome b5 in the oxidative metabolism of polychlorinated biphenyls catalyzed by cytochrome P450.

1. The role of cytochrome b5 in the cytochrome P450-dependent hydroxylation of tetrachlorobiphenyl (TCB) isomers was examined using a reconstituted system consisting of CYP2B1 and CYP1A1 and rat liver microsomes. 2. By addition of cytochrome b5 to the reconstituted system containing CYP2B1, the 3-hydroxylation of 2,5,2,'5'- and 2,5,3',4'-TCB was increased about six-fold, but the 3- and 5-hydroxylation of 2,4,3',4'-TCB was decreased by about 50% 3. All hydroxylations of 3 ,4,3',4'-,2,5, 3,4'- and 2,4,3',4'-TCBs were decreased by addition of cytochrome b5 to the reconstituted system containing CYPlA1. 4. In stoichiometry measurements, changes in NADPH oxidation and coupling efficiency by addition of cytochrome b5 was observed and these differed according to the position of chlorine atoms of TCBs and cytochrome P450 isoforms used in the systems.

Animals↗
PubMed1996

[Atherectomy in patients with arteriosclerosis obliterans: angiographic follow-up study of 186 lesions in 146 patients].

Atherectomy (ATE) is a new catheter-mediated technique for the removal of atheroma in patients with arteriosclerosis obliterans (ASO). ATE was performed using 7-10 Fr. Simpson Peripheral Athero Track catheters at 186 sites in 146 patients, whose lesions involved 49 common iliac arteries, 66 external iliac arteries, 68 femoral arteries and three other arteries. The initial success rate was 94.1%. The mean percent of the diameter stenosis was reduced from 79.0 +/- 1.2% (mean +/- SD) to 22.7 +/- 1.0%. There were two cases of perforation that required surgical treatment (1.1%). The complication rate was 4.4%. The 0.5-, 1-, 2- and 3-year patency rates were 87.6%, 79.6%, 62.5% and 62.5%, respectively. The rate of long-term patency in each segment of arterial lesions revealed that the patency rate in the common iliac artery was significantly higher than the rates in the external iliac artery (p < 0.05) and femoral artery (p < 0.01). The patency rates for long lesions (> or = 2.0 cm) and occluded lesions were significantly (p < 0.01) lower than those for short lesions (< 2.0 cm). Diabetic patients had a higher re-stenosis rate than nondiabetic patients (p < 0.05). In conclusion, ATE is an effective new method for the treatment of patients with ASO.

Aged↗
PubMed1995

Metabolism of highly persistent PCB congener, 2,4,5,2',4',5'-hexachlorobiphenyl, by human CYP2B6.

Metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl was studied with cDNA-expressed human P450 2B isoform, CYP2B6. 3-Hydroxy-2,4,5,2',4',5'-hexachlorobiphenyl was identified as a major metabolite, and the formation activity was compared with that of dog CYP2B11 and guinea pig P450GP-1. The activity of 3-hydroxylation was comparable with that of P450GP-1, but one-tenth of CYP2B11. These results indicate that P450 2B in humans as well as other animal species can metabolize 2,4,5,2',4',5'-hexachlorobiphenyl, and the reason why this PCB congener remained most abundantly in human bodies is discussed.

Animals↗
PubMed1995

Purification and characterization of a newly identified isoform of cytochrome P450 responsible for 3-hydroxylation of 2,5,2',5'-tetrachlorobiphenyl in hamster liver.

In the hamster liver, 2,5,2',5'-tetrachlorobiphenyl (TCB) is metabolized to 3-hydroxy- and 4-hydroxy-2,5,2',5'-TCB to a similar extent, and formation of the former metabolite is stimulated by phenobarbital pretreatment of the animals, while that of the latter metabolite is stimulated by 3-methylcholanthrene pretreatment. In the present study, we identified a new isoform (designated P450HPB-1) of cytochrome P450 which proved to be phenobarbital-inducible and responsible for 3-hydroxylation of this TCB isomer. This isoform was purified from liver microsomes of phenobarbital-treated hamsters and characterized. P450HPB-1 has a molecular mass of 50 kDa, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the absorption maxima of the oxidized form at 417 nm and of the reduced CO-complex form at 450 nm. The sequence of 28 amino acids of P450HPB-1 at the amino-terminal has a 68% similarity with those of rat P450 2B1 and mouse P450 2b10, 57% similarity with that of guinea pig P450GP-1, and 54% similarity with that of guinea pig P450GP-1, and 54% similarity with those of rabbit P450 2B4 and dog P450 2B11. P450HPB-1 in the reconstituted system catalyzed the 3- but not 4-hydroxylation of 2,5,2',5'-TCB, at a rate of 19.0 pmol/min/nmol P450. The isoform also has high catalytic activity for 17-oxidation of testosterone but low activity for the N-demethylation of benzphetamine and 16 alpha- and 16 beta-hydroxylations of testosterone. In microsomal metabolism of 2,5,2',5'-TCB, rabbit antiserum against P450HPB-1 almost completely inhibited 3- but not 4-hydroxylation. Immunoblot analysis of hamster liver microsomes revealed that P450HPB-1 was constitutive and phenobarbital-inducible but was decreased by pretreatment with 3-methylcholanthrene or 3,4,5,3',4'-pentachlorobiphenyl. These results suggest that P450HPB-1 belongs in the P450 2B subfamily and apparently plays a major role in the 3-hydroxylation of 2,5,2',5'-TCB, in hamster liver.

Amino Acid Sequence↗
PubMed1995

Effect of cytochrome P450 inducers on liver microsomal metabolism of tetrachlorobiphenyls in rats, guinea pigs and hamsters.

Effect of cytochrome P450 (P450) inducers on liver microsomal metabolism of 3,4,3',4'-, 3,5,3',5'- and 2,5,2', 5'-tetrachlorobiphenyl (TCB) was studied using male Wistar rats, male Hartley guinea pigs and male Golden syrian hamsters. In metabolism of 3,4,3'4'- and 3,5,3',5'-TCB, liver microsomes from 3-methylcholanthrene (MC)- or 3,4,5,3',4'-pentachlorobiphenyl (PenCB)-treated hamsters showed hydroxylase activities for both TCB isomers, although the activities were much less than those of rats. In contrast, liver microsomes form untreated and phenobarbital (PB)-, MC- or PenCB-treated guinea pigs showed no hydroxylase activity. In 2,5,2',5'-TCB metabolism, 3-hydroxylase activity was observed in untreated guinea pigs and hamsters, but not in untreated rats. The activity pigs was induced by PB treatment in all three species, at rates of 324, 19 and 20 pmol/min/mg protein in rats, guinea and hamsters, respectively. This activity was not enhanced by treatment with either MC or PenCB. Only in hamsters was 4-hydroxylated metabolite formed in all microsomes used in addition to the 3-hydroxylated one, and the formation was accelerated 2.0-, 2.7- and 4.8-fold by treatment with PB, MC and PenCB, respectively. These results suggest that different P450 isoforms in hamster liver microsomes are involved in 3- and 4-hydroxylation of 2,5,2',5'-TCB. Thus, there are species differences in the basal ability to hydroxylate TCB isomers, and in the extent of effect of P450 inducers on the metabolism of these isomers among the three species.

Animals↗
PubMed1995

Reduced coronary vasodilation in patients with familial hypercholesterolemia following intracoronary injection of isosorbide dinitrate.

To clarify the relationship between the dilatation of angiographically non-stenotic coronary artery segments in response to isosorbide dinitrate (ISDN), and serum lipids, 5 coronary segments in 7 patients with familial hypercholesterolemia (FH) and 43 patients with non-familial hypercholesterolemia (non-FH), who had either 1- or 2-vessel coronary heart disease, were investigated. The serum total cholesterol level was significantly greater in FH than in non-FH. Before and after the direct intracoronary injection of ISDN, coronary diameter was measured by a computer-assisted coronary angiography analysis system. The order of the dilative responses in coronary segments in non-FH patients (segments: #5 > #11 > #6 > #13 > #7) was exactly the same as the order of their original diameters, while the ratio of the increase in diameter (after/before ISDN injection) did not differ among any of the segments (mean: 1.08-fold increase). In the non-FH group, no correlation was found between the serum total cholesterol, triglyceride, low-density lipoprotein-cholesterol, or high-density lipoprotein-cholesterol, and the ratio of the coronary diameter after and before injection of ISDN. Moreover, hypercholesterolemia in non-FH did not affect the coronary dilative response to ISDN injection. In the FH group, although the original diameter of each segment did not differ from that in the non-FH group, the ratio of the diameter after and before injection of ISDN was significantly smaller in FH than in non-FH (p < 0.01). These results suggest that a non-stenotic coronary artery in FH has a lower capacity for vasodilation in response to ISDN. Although hypercholesterolemia was excluded as a factor which may suppress the capacity for coronary dilation in non-FH, spontaneous hypercholesterolemia in FH may affect medial smooth muscle functions of the coronary artery.

Adult↗
PubMed1995

Molecular analysis of growth inhibition caused by overexpression of the biotin operon in Escherichia coli.

Constitutive overexpression of the biotin operon (type 9 mutation) in a multicopy plasmid resulted in growth inhibition in Escherichia coli. Deletion analysis of the biotin operon indicated that overexpression of the bioB gene alone, the product of which is believed to catalyze the conversion of dethiobiotin to biotin, is sufficient for growth inhibition. This growth inhibition was still observed when the wild-type bioB gene was replaced by several mutant-type bioB genes derived from biotin auxotrophs that have base-pair substitutions creating amino acid substitutions in the bioB gene product. However, the modification of Ala 143 and Gly 99 of the bioB gene product resulted in recovery from growth inhibition. These results suggest that this phenotype of growth inhibition by overexpression of the bioB gene in E. coli is independent of the biotin-forming activity itself, but is caused by some function involving a specific conformation of the bioB gene product.

Amino Acid Sequence↗
PubMed1995

Treatment of homozygous and double heterozygous familial hypercholesterolemic children with LDL-apheresis.

Within the framework of a seven-year clinical experience on treatment of severe hyperlipoproteinemia with/without associated coronary heart disease, with therapeutic plasmapheresis (APO B-100-containing lipoprotein-apheresis), we focused the present report on two young patients aged 7 and 11 years, respectively. The older patient is a boy treated since 1990 by plasma-exchange, cascade filtration-low density lipoprotein apheresis (LDL-apheresis), and dextrane sulphate-LDL apheresis. Over the treatment period the patient was submitted to three consecutive coronary angiographies. The second is a girl first submitted to a coronary angiography and then treated with dextrane sulphate-LDL apheresis. Up to now, a total of one-hundred therapeutic plasmaphereses have been performed. The interval of treatment was of fifteen days, and a volume of 2-3000 ml of plasma was processed at each session. The systems used were the following: DIDECO Vivacell BT 798-A, DIDECO Vivacell BT 798-A + BT 803, DIDECO BT 985 (Dideco, Mirandola, Italy), KANEKA MA-01 (Kanegafuchi, Osaka, Japan). Mean (SD) plasma apo B-100-containing major lipoprotein-LDL, Lp(a)-levels during treatment, are reported below: [table: see text] The treatment was very well tolerated. Rare, moderate hypotensive events occurred. Nevertheless, all procedures were regularly completed. A mild hypochromic anemia, regressed using drug treatment, was observed in the boy. Along with the improvement of plasma atherogenic profile, a regression of skin xanthomas and unchanged favourable coronary angiograms, were obtained in the above mentioned patient.

Apolipoproteins A↗
PubMed1994

Flavodoxin is required for conversion of dethiobiotin to biotin in Escherichia coli.

We have reported [Ifuku, O., Kishimoto, J., Haze, S., Yanagi, M. & Fukushima, S. (1992) Biosci. Biotechnol. Biochem. 56, 1780-1785] the enzymic conversion of dethiobiotin to biotin (catalyzed by the enzyme encoded by bioB) in cell-free extract of Escherichia coli which had been genetically engineered for high bioB expression. An unidentified protein(s) in addition to the bioB gene product is obligatory for this reaction. We have found that this protein was precipitated from the cell-free extract with poly(ethyleneimine), and we have purified it to homogeneity by a procedure which includes ammonium sulfate fractionation, DEAE-cellulose chromatography, gel filtration, and Mono Q chromatography. The apparent molecular mass of the purified protein was estimated to be about 21 kDa by SDS/PAGE. The N-terminal amino acid sequence of the purified protein was identical with that of E. coli flavodoxin. We conclude that flavodoxin is required for conversion of dethiobiotin to biotin in E. coli. Studies with purified flavodoxin and the fraction containing the bioB gene product suggested that protein(s) in addition to the bioB gene product and flavodoxin is also obligatory for the reaction.

Amino Acid Sequence↗