Biomedical subjects

S Ohmori

Publications and source records attributed to S Ohmori.

At least 163 records · Page 9Linked to original sources

PubMed1994

Involvement of a cytochrome P4502D subfamily in human liver microsomal bunitrolol 4-hydroxylation.

The oxidative metabolism of bunitrolol, an adrenergic beta-receptor antagonist was examined in human liver microsomes fortified with an NADPH-generating system. The microsomal fractions (n = 11) showed bunitrolol 4-hydroxylase activities, which correlated well with CYP2D6 contents (correlation coefficient, r = 0.854), debrisoquine 4-hydroxylase (r = 0.953) and imipramine 2-hydroxylase (r = 0.976) activities. On the other hand, the bunitrolol 4-hydroxylase activity showed relatively poor correlations with CYP3A4 content (r = 0.552) and testosterone 6 beta-hydroxylase activity (r = 0.668). The bunitrolol 4-hydroxylase activity was significantly inhibited by quinidine, a selective inhibitor for CYP2D6. Polyclonal antibodies raised against rat liver microsomal cytochrome P450BTL, which is thought to belong to the CYP2D subfamily, effectively inhibited bunitrolol 4-hydroxylation. In contrast, polyclonal antibodies raised against human liver microsomal CYP3A4 did not show any inhibitory effect on the activity. These results suggest that CYP2D6 is involved in the bunitrolol 4-hydroxylase activity in human liver microsomes.

Adolescent↗

PubMed1994

Pharmacologically active components from a Peruvian medicinal plant, huira-huira (Culcitium canescens H. & B.).

The methanol extract of Huira-Huira (Culcitium canescens) showed analgesic effects in acetic acid-induced writhing and tail pressure tests, and it also produced potent prolongation of hypnosis induced by pentobarbital. The latter activity was used as an isolation-guide to determine the active components which were identified as dehydrocacalohastine, cacalohastine and cacalonol.

Analgesics↗

PubMed1994

[Mortality from major causes of death and its risk factors in the elderly--26-year follow-up study in Hisayama].

The authors studied mortality from major causes of death and risk factors in the elderly in a long-term prospective survey conducted in a Japanese suburban community, Hisayama. In the baseline survey in 1961, we scrutinized 1658 residents of the town aged 40 years or older accounting for 92% of the total population in this age range. Of those, 591 residents (245 men and 346 women) aged 60 years or older, who were free from major cardiovascular disease, were selected for the present study. They were followed-up for 26 years from 1961 to 1987. The average age was 67 years for men and 70 years for women, being significantly higher for women than for men. During the follow-up period, 529 subjects (89.5%) died, and 448 were autopsied (autopsy rate 84.7%). The all-cause mortality (per 1,000 person-years) after adjustment for age was 89.9 for men and 56.7 for women, the former being significantly higher than the latter (p < 0.01). The age-adjusted mortality from cerebrovascular disease was estimated to be 21.4 for men and 9.9 for women, i.e. 8.9 and 8.8 from heart disease, and 19.9 and 10.6 from neoplasm, and 18.1 and 12.2 from-pneumonia, respectively. There was significant sex difference in mortality from cerebrovascular disease, neoplasm and pneumonia (p < 0.01) but not from heart disease (p > 0.1). Multiple Cox's proportional hazards regression analysis showed systolic blood pressure and male sex to be significant risk factors for death by cerebrovascular disease. Systolic blood pressure was also a predictor for death by heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1994

Adrenocortical response to tail-suspension in young and old rats.

We recently showed that increased glucocorticoid secretion aggravates disuse atrophy when induced by skeletal unloading. Disuse atrophy in the elderly is becoming a serious problem in many developed countries. In this study we attempted to examine how aging affects the glucocorticoid response to skeletal unloading. Three groups of rats (aged 5 weeks, 12 months and 18 months) were subjected to 7 days of hind limb unloading by tail-suspension. Urinary excretion of corticosterone over a 24-hr period were monitored every other day. Corticosterone excretion in the control group of 5-week-old rats was initially 87.4 +/- 12.8 ng/day and did not change throughout the experiment. Tail-suspension experiments yielded a significant increase (more than 3 fold) in excretion on days 1 and 3 of the suspension before returning to control levels. In the 12-month-old rats, a marked increase in the basal corticosterone level was observed in the control rats throughout the experiment, while the increase by tail-suspension was attenuated with a transient, significant increase on day 5. In 18-month-old rats, a further increase in the basal level was observed in the control group, although excretions tended to increase steadily from day 1 to day 3 and remained high until day 7. Urinary excretion of corticosterone among the 18-month-old suspension group was similar to those observed in the control group. These results indicate that the younger (5-week-old) rats adapted the stress load caused either by tail-suspension or manipulation alone faster than the older rats did (12 or 18 months old). The observation that basal corticosterone excretion increases with age suggests, alterations in the hypothalamic-pituitary-adrenal axis among the aged rats which might aggravates disuse atrophy induced by skeletal unloading.

Adaptation, Physiological↗

PubMed1994

Changes in serum 1,25-dihydroxyvitamin D3 and mRNAs for osteocalcin and alkaline phosphatase in femur unloaded by tail suspension in rats.

To elucidate the mechanism involved in the development of disuse atrophy of bone by skeletal unloading, changes in osteocalcin and alkaline phosphatase mRNAs, markers for bone formation, were studied in the hind limb bones of tail-suspended rats. Tail suspension for 8 and 14 days resulted in a significant decrease in osteocalcin mRNA in the femur when compared with age-matched non-suspended controls. Serum 1,25-dihydroxyvitamin D3 decreased to 60% of the control level after 8 days of skeletal unloading but regained almost normal levels over the next 7 days. Since it is known that vitamin D3 up regulates and glucocorticoid down regulates transcription of the osteocalcin gene, the endocrine response evoked by tail suspension may have aggravated the disuse atrophy caused by skeletal unloading in this study.

Alkaline Phosphatase↗

PubMed1994

Hyperinsulinaemia and blood pressure in a general Japanese population: the Hisayama Study.

OBJECTIVES: To study the relationship between serum insulin and blood pressure, as well as the prevalence of hypertension according to the insulin level in a general Japanese population. DESIGN: In 1988 a cross-sectional community survey was conducted among Hisayama residents aged 40-79 years. METHODS: A total of 1073 males and 1407 females (72.5 and 80.5% of the total population, respectively) underwent comprehensive investigation, including a 75-g oral glucose-tolerance test. Fasting and 2-h serum insulin levels were measured by radioimmunoassay. RESULTS: The sum of the fasting and 2-h postloading insulin levels was significantly correlated with the systolic blood pressure (SBP; r = 0.18 and 0.26 for males and females, respectively) and the diastolic blood pressure (DBP; r = 0.24 and 0.19, respectively) in the subjects not receiving antihypertensive drugs. In multiple regression analysis the correlation with blood pressure remained significant in both sexes even after controlling for age, body mass index, alcohol intake, smoking, a family history of hypertension, serum total cholesterol and fasting plasma glucose. The age- and sex-adjusted prevalence of hypertension (SBP > or = 160 mmHg or DBP > or = 95 mmHg, or both, or receiving drug treatment) increased significantly with an increase in the sum of fasting and 2-h postload insulin levels in both the non-obese subjects (body mass index < 25 kg/m2) and the obese subjects (body mass index > or = 25 kg/m2). Multiple logistic regression showed that the sum of fasting and 2-h postload insulin levels was a significant factor with an independent relationship to hypertension, even after taking the other risk factors into account. CONCLUSION: The present study suggests that hyperinsulinaemia is related to hypertension in a general Japanese population.

Adult↗

PubMed1994

Crossover comparison of the effects of enalapril and captopril on potassium homeostasis in patients with mild hypertension.

The effects of two types of angiotensin converting enzyme (ACE) inhibitors, enalapril (long-acting) and captopril (short-acting), on serum electrolytes and circadian rhythm of urinary electrolyte excretions were compared in relation to aldosterone status in patients with essential hypertension and normal renal function. Enalapril (5 mg once daily) and captopril (12.5 mg t.i.d.) were administered to 11 patients for 1 week each in a crossover fashion. Blood sampling in the early morning and 4-hour split urinary sampling for 24 hours were performed on the last day of control and each treatment periods. Enalapril and captopril significantly reduced blood pressure to similar levels. Enalapril but not captopril significantly inhibited plasma aldosterone concentration and urinary aldosterone excretion. Neither drug apparently altered serum or urinary Na levels. Both drugs significantly decreased urinary K excretion (p < 0.05, control: 44 +/- 4 mEq/day, captopril: 39 +/- 2 mEq/day, enalapril: 39 +/- 2 mEq/day; mean +/- SEM), but did not significantly alter serum K level (control: 4.1 +/- 0.1 mEq/l, captopril 4.2 +/- 0.2 mEq/l, enalapril 4.3 +/- 0.1 mEq/l). The circadian rhythm (acrophase) of urinary K excretion was not affected by either drug, while the amplitude was decreased by both, as assessed by the cosinor method. In summary, although enalapril caused more sustained inhibition of aldosterone secretion compared with captopril, both drugs showed similar effects on the K homeostasis in patients with mild essential hypertension.

Aldosterone↗

PubMed1994

[A ruptured peripheral, superior cerebellar artery aneurysm: a case report and a review of the literature as to surgical approaches].

The authors described the case of a normotensive 40-year-old female with severe headache and vomiting. Neurological findings on admission to our hospital revealed no deficits, but plain CT findings indicated subarachnoid hemorrhage in the ambient, supracerebellar, quadrigeminal, and right lateral pontine cisterns. Left vertebral angiograms made through a transfemoral catheter revealed a saccular aneurysm (6 x 4mm) arising from the medical hemispheric branch of the right superior cerebellar artery (SCA). On the 34th day after onset of her symptoms, the aneurysm was successfully clipped by using an infratentorial supracerebellar approach. She was discharged with no deficits. Based on our experience and a review of the literature, a peripheral SCA aneurysm is best clipped by using one of the following surgical approaches: (1) a subtemporal transtentorial approach for an aneurysm arising from the anterior or lateral pontomesencephalic segment, (2) a subtemporal or occipital transtentorial approach for an aneurysm arising from the cerebellomesencephalic segment or the proximal cortical branch, or (3) an infratentorial supracerebellar approach for an aneurysm arising from the distal cortical branch.

Adult↗

PubMed1993

Expression of human cytochrome P450 enzymes in yeast and bacteria and relevance to studies on catalytic specificity.

Heterologous expression systems can be utilized to great advantage in the study of cytochrome P450 (P450) and other enzymes involved in the biotransformation of drugs and other xenobiotics. The list of studies made possible with the technology includes discernment of catalytic specificity, elucidation of structure-activity relationships, and various biophysical measurements. There are advantages and disadvantages to each of the vector systems and choices must be made on the basis of needs. Yeast expression systems were used to establish that different P450 2C enzymes are involved in the hydroxylations of tolbutamide and (S)-mephenytion. P450 3A4 was also expressed in yeast and its very broad catalytic specificity was confirmed. Recently, it has been possible to express P450 3A4 as well as other human and animal P450s in bacteria after slight modification of their 5'-coding sequences.

Amino Acid Sequence↗

PubMed1993

Expression of modified human cytochrome P450 3A4 in Escherichia coli and purification and reconstitution of the enzyme.

A full-length human cytochrome P450 (P450) 3A4 cDNA clone and four derivatives in which the N-terminus was modified were inserted into a pCW vector and used to transform Escherichia coli DH5 alpha cells. Little expression was seen with the native sequence; the highest level of expression (range of 40-110 membrane-bound nmol P450 liter-1) was achieved with a construct (NF14) in which residues 3-12 were deleted. In all of the constructs P450 was found primarily in the membranes. The modified P450 3A4 (construct NF14) showed typical P450 hemoprotein spectra. The protein was purified to electrophoretic homogeneity in a five-step procedure [nominally 23 nmol P450 (mg protein)-1]. For most purposes it was found to be more practical to purify the modified P450 3A4 to approximately 70% homogeneity [nominally 15 nmol P450 (mg protein)-1] in a simple two-step process. The modified P450 3A4 (NF14) or P450 3A4 purified from human liver could be mixed with rabbit liver NADPH-P450 reductase to achieve catalytic activities nearly as high as those found in human liver microsomes (on a nmol P450 basis), but the optimal reconstitution conditions included not only a mixture of phosphatidylserine, L-alpha-dilauroyl- and L-alpha-dioleoyl-sn-glycero-3-phosphocholines, cholate, and cytochrome b5 suggested by others but also glutathione during the preincubation. Several other thiols were found not to substitute in this role. Good catalytic activity was seen for nifedipine oxidation, testosterone 6 beta-hydroxylation, and the 8,9-epoxidation and 3 alpha-hydroxylation of aflatoxin B1, reactions previously ascribed to the enzyme. These procedures provide a relatively convenient and reliable means of producing, purifying, and reconstituting a catalytically active and useful derivative of P450 3A4, a human P450 enzyme that has many roles in the oxidation of drugs and other xenobiotic chemicals.

Amino Acid Sequence↗

PubMed1993

Differential role in lipid peroxidation between rat P450 1A1 and P450 1A2.

The role of cytochrome P450 (P450) in lipid peroxidation induced by NADPH or peroxide was investigated in a reconstituted system. When cumene hydroperoxide, t-butyl hydroperoxide and hydrogen peroxide were used as initiators, the rates of malondialdehyde (MDA) formation were much higher in a reconstituted system containing P450 1A1 than those observed in a reconstituted system containing P450 1A2. In contrast to peroxide-induced lipid peroxidation, P450 1A2 catalysed NADPH-induced lipid peroxidation more effectively than did P450 1A1 regardless of the presence of ADP-Fe(NO3)3. Carbon monoxide inhibited NADPH-induced formation of MDA in a reconstituted system containing P450 1A2, but not P450 1A1. In addition, superoxide dismutase (SOD) was an effective inhibitor in a NADPH-induced lipid peroxidation system catalysed by P450 1A2 but not by P450 1A1. These results suggest that a peroxide-induced reaction might proceed readily with P450 1A1, whereas P450 1A2 mainly functions in NADPH-induced lipid peroxidation via generation of an active oxygen species. It is furthermore indicated that the difference in the effect of SOD in NADPH-induced lipid peroxidation depends on the P450 used.

Animals↗

PubMed1993

Involvement of CYP2D6 in oxidative metabolism of cinnarizine and flunarizine in human liver microsomes.

Oxidative metabolism of cinnarizine (CZ) and its fluorine derivative flunarizine (FZ), both of which are selective calcium entry blockers, was examined in human liver microsomes. The ring-hydroxylations and the N-desalkylations constituted primary metabolic pathways in microsomal metabolism of CZ and FZ. Among these pathways, the ring-hydroxylase (p-hydroxylation) activities at the cinnamyl moiety of both drugs were highly correlated with debrisoquine 4-hydroxylase activity and CYP2D6 content. Quinidine, a selective inhibitor of CYP2D6, suppressed the ring-hydroxylase activities of CZ and FZ. These results suggest that CYP2D6 is involved in the ring-hydroxylation of the cinnamyl moiety of both CZ and FZ in human liver microsomes.

Biotransformation↗

PubMed1993

Cystathionine gamma-lyase of Saccharomyces cerevisiae: structural gene and cystathionine gamma-synthase activity.

Purification of Saccharomyces cerevisiae cystathionine gamma-lyase (gamma-CTLase) was hampered by the presence of a protein migrating very close to it in various types of column chromatography. The enzyme and the contaminant were nevertheless separated by polyacrylamide gel electrophoresis. N-terminal amino acid sequence analysis indicated that they are coded for by CYS3 (CYI1) and MET17 (MET25), respectively, leading to the conclusion that CYS3 is the structural gene for gamma-CTLase and that the contaminant is O-acetylserine/O-acetylhomoserine sulfhydrylase (OAS/OAH SHLase). Based on these findings, we purified gamma-CTLase by the following strategy: (1) extraction of OAS/OAH SHLase from a CYS3-disrupted strain; (2) preparation of antiserum against it; (3) identification of a strain devoid of the OAS/OAH SHLase protein using this antiserum; and (4) extraction of gamma-CTLase from this strain. Purified gamma-CTLase had cystathionine gamma-synthase (gamma-CTSase) activity if O-succinylhomoserine, but not O-acetylhomoserine, was used as substrate. From this notion we discuss the evolutional relationship between S. cerevisiae gamma-CTLase and Escherichia coli gamma-CTSase.

Amino Acid Sequence↗

PubMed1993

Purification and characterization of two forms of hepatic microsomal cytochrome P450 from untreated cynomolgus monkeys.

Two forms of cytochrome P450, referred to as P450 CMLb and P450 CMLc, were purified and characterized from hepatic microsomes of untreated cynomolgus monkeys (Macaca irus). The final preparations were apparently homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The minimum molecular weights of P450 CMLb and P450 CMLc estimated from the mobilities on the gel were 48 and 50 kDa, respectively. The N-terminal amino acid sequences of P450 CMLb and P450 CMLc (first 13 residues) were identical, respectively, with those of P450 FI isolated from baboons and P450 MK-2, which has been characterized as a P450 3A enzyme in cynomolgus monkeys. P450 CMLb showed coumarin 7-hydroxylation and 7-ethoxycoumarin O-deethylation activities. This P450 enzyme reacted with anti-P450 2A6 antibody and acts as a coumarin 7-hydroxylase in hepatic microsomes. On the basis of these results P450 CMLb was classified into the 2A subfamily. P450 CMLb is expressed constitutively as one of the minor forms of P450 in liver microsomes of untreated cynomolgus monkeys and is inducible by phenobarbital. P450 CMLc reacted with anti-P450 3A4 antibody and hydroxylated testosterone at the 6 beta-position. The testosterone 6 beta-hydroxylation activities in hepatic microsomes of cynomolgus monkeys, common squirrel monkeys, and humans were strongly inhibited by the anti-P450 CMLc antibody. These results demonstrate that this P450 enzyme is in the P450 3A subfamily.

Amino Acid Sequence↗

PubMed1993

Prevalence of type 2 (non-insulin-dependent) diabetes mellitus and impaired glucose tolerance in the Japanese general population: the Hisayama Study.

We determined the population-based prevalence of diabetes mellitus in members of the Japanese community, Hisayama aged 40-79 years old by a 75-g oral glucose tolerance test. The basic population used to calculate diabetic prevalence was 1,077 men (72.8% of the whole population in the same age range) and 1,413 women (80.8%) including ten diabetic patients on insulin therapy. In addition, we compared the prevalence of history of diabetes which was acquired by interview or questionnaire, between participants and non-participants in the 75-g oral glucose tolerance test, but they were not statistically different. The age-adjusted prevalence of diabetes to world population was 12.7% for men and 8.4% for women, and that of impaired glucose tolerance was 19.6% for men and 18.4% for women. These figures were much higher than those previously reported from several Japanese communities. The results obtained from the present study could reveal true prevalence of diabetes among the Japanese population. In addition, the reasons for the increasing prevalence of diabetes among the recent Japanese population are also discussed.

Adult↗

PubMed1993

MDS-macrophage derived inhibitory activity on myelopoiesis of MDS abnormal clones.

We studied the effect of myelodysplastic syndrome (MDS)-derived adherent cells on colony formation of granulocyte-macrophage progenitors (CFU-GM) in both normal and MDS bone marrow cells. MDS-adherent cells suppressed the growth of normal CFU-GM colony formation. Antibodies against ferritin almost totally neutralized the haematopoietic inhibitory activity. Antibody against gamma-interferon (gamma-IFN) did not have such effect. By cytogenetic analysis using G-staining method, MDS-derived CFU-GM colony showed abnormal clones. MDS have been recognized to be a mosaic of normal and abnormal clones. MDS-macrophages suppressed the growth of progenitor cells derived from normal clones by soluble factors, but did not suppress the growth of those from abnormal clones. It is suggested that progenitor cells derived from abnormal clones are freed from the negative myelopoietic regulator that may be related to the progress of leukaemia.

Adult↗

PubMed1993

Age-related changes in endothelium-dependent hyperpolarization in the rat mesenteric artery.

This study was designed to determine the age-related changes in the endothelium-dependent hyperpolarization to acetylcholine (ACh) and its contribution to relaxation in the isolated mesenteric artery from normotensive and hypertensive rats. Membrane potentials and contractions were recorded in arteries from male Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) that were 5-6 wk old (young), 6-8 mo old (adult), and 20-26 mo old (aged). Endothelium-dependent hyperpolarizations produced by ACh, applied both at the resting state of the membrane and under conditions of depolarization with norepinephrine (10(-5) M), were markedly impaired in aged WKY rats, adult SHR, and aged SHR. Endothelium-dependent relaxations to ACh in arterial rings precontracted with 10(-5) M norepinephrine were also impaired in aged WKY rats, adult SHR, and aged SHR even in the presence of indomethacin. Furthermore, in these rats, N omega-nitro-L-arginine, an inhibitor of nitric oxide formation, showed potent inhibitory effects on the relaxations, whereas the 20 mM high K+ solution that reduces hyperpolarization had less pronounced effects. Hyperpolarizations and relaxations to cromakalim (10(-5) M), a K(+)-channel opener, were on the whole preserved in aged rats. It would thus appear that the endothelium-dependent hyperpolarization to ACh is reduced with aging as well as by hypertension, and this would, in part, account for the impaired relaxation to ACh in arteries of both aged rats and hypertensive rats.

Acetylcholine↗

PubMed1993

Inhibitory effects of S-(1,2-dicarboxyethyl)glutathione on collagen-induced platelet aggregation; enhancements of cyclic AMP level and adenylate cyclase activity in platelets by S-(1,2-dicarboxyethyl)glutathione.

S-(1,2-Dicarboxyethyl)glutathione (DCE-GS) in addition to being present in the liver, lens, and heart, also inhibited platelet aggregation. To clarify these inhibitory effects, the role of DCE-GS in the release of ATP and serotonin from platelets was studied, as was thromoboxane A2 formation, cyclic AMP level and adenylate cyclase activity in human platelets. The results are as follows: DCE-GS at a concentration of 1.3 mM inhibited ATP and serotonin release from platelets induced by collagen, by 77.4 +/- 4.3 and 78.7 +/- 6.3%, respectively. At 1.5 mM DCE-GS also inhibited the formation of thromboxane B2 by 79.6 +/- 4.1%. Incubation of human platelet rich plasma with 2 mM of DCE-GS for 10 min increased the cyclic AMP level and the activity of adenylate cyclase by 204 +/- 28 and 211 +/- 11.7%, respectively. These results suggest that the inhibitory effect of DCE-GS on the platelet aggregation induced by collagen is due to an increase in the cyclic AMP level in platelets, which in turn may be due to enhancement of the activity of adenylate cyclase.

Adenosine Triphosphate↗