PubMed Health⌕ Search

Biomedical subjects

S Ohmori

Publications and source records attributed to S Ohmori.

At least 109 records · Page 6Linked to original sources
PubMed1998

Steroid hydroxylation by human fetal CYP3A7 and human NADPH-cytochrome P450 reductase coexpressed in insect cells using baculovirus.

Human fetal CYP3A7 and human NADPH-cytochrome P450 reductase were coexpressed in insect cells, TN-5, infected with a recombinant baculovirus carrying both cDNAs. The expression of reductase in TN-5 cells was shown to be sufficient for the CYP3A7 dependent 16 alpha-hydroxylation of dehydroepiandrosterone. However, the extra addition of cytochrome b5 and phospholipid was necessary to obtain a maximal activity of CYP3A7 catalyzing the reaction. CYP3A7 expressed in TN-5 cells was capable of metabolizing testosterone, cortisol and dehydroepiandrosterone 3-sulfate as well as dehydroepiandrosterone. The apparent Vmax for 6 beta-hydroxylations of testosterone was similar to that obtained for 6 beta-hydroxylation of cortisol (2.9 versus 2.5 nmol/nmolP450/min). In contrast, the apparent Vmax for 16 alpha-hydroxylation of dehydroepiandrosterone and its 3-sulfate were 20 and 2 times greater than those observed for steroid 6 beta-hydroxylations, respectively (67.5 and 5.8 versus 2.5-2.9 nmol/nmol P450/min). On the other hand, the apparent K(m) for 6 beta-hydroxylations of testosterone and cortisol were greater than those for 16 alpha-hydroxylations (120 and 860 versus 46-58 microM). Thus, CYP3A7 was active for steroid 6 beta-hydroxylations and 16 alpha-hydroxylations, but there were greater differences in Vmax/K(m) ratios between these reactions.

Animals↗
PubMed1998

Stimulation of cholesterol release from rabbit foam cells by the action of a new inhibitor for acyl CoA:cholesterol acyltransferase (ACAT), HL-004.

A new inhibitor of acyl CoA:cholesterol acyltransferase (ACAT), HL-004 [N-(2, 6-diisopropylphenyl)tetradecylthioacetamide], suppressed the synthesis of cholesterol [14C]oleate at 10(-9) approximately 10(-7) M in a concentration-dependent manner in both THP-1 cell-derived macrophages and foam cells prepared from aortic intima of rabbits fed a high cholesterol diet. Incorporation of [3H]cholesterol oleate-beta very low density lipoproteins was not inhibited by HL-004 at 10(-9) approximately 10(-7) M. Release of radioactivity from the cells loaded with [3H]cholesterol oleate-beta very low density lipoproteins was increased by the inhibition of ACAT activity with HL-004. HL-004 did not affect on acid and neutral cholesterol esterases. As a result, cholesterol ester content in foam cells decreased. These data suggested that HL-004 decreases cholesterol ester in foam cells by increasing the release of cholesterol and therefore might suppress atherosclerotic lesions.

Acetanilides↗
PubMed1997

A splicing variant of Steroid Receptor Coactivator-1 (SRC-1E): the major isoform of SRC-1 to mediate thyroid hormone action.

Steroid Receptor Coactivator-1 (SRC-1) interacts with nuclear receptors only when they are bound to the ligands and enhance the transactivation. We identified splicing variants encoding three isoforms, SRC-1, SRC-1(-Q), and SRC-1E, generated by alternative usage of an exon(s) and splicing acceptor sites. RT-PCR analysis showed that SRC-1E was more abundantly expressed than SRC-1 or SRC-1(-Q) at the mRNA level in all the cell lines tested. SRC-1E lacks 56 amino acids of SRC-1 and has unique 14 amino acids at the carboxyl terminus, while SRC-1(-Q) differs from SRC-1 by deletion of only one glutamine residue. Since the C-terminal domain of SRC-1 has been shown to be involved in the interaction with nuclear receptors, the enhancement of transactivation by these three isoforms was tested. SRC-1E enhanced thyroid hormone dependent transactivation of reporter gene expression more profoundly than SRC-1 or SRC-1(-Q). Taken together, it was suggested that SRC-1E is the major isoform of SRC-1 to mediate thyroid hormone action.

Amino Acid Sequence↗
PubMed1997

Determination of acetaldehyde in biological samples by gas chromatography with electron-capture detection.

A simple specific assay was developed for the determination of acetaldehyde in biological samples. Acetaldehyde was derivatized to 2,4-dinitrophenylhydrazone, which was determined by gas chromatography with electron-capture detection. The use of this detection method is an important device to which no one drew notice. This procedure was very simple and so sensitive that as little as 500 fmol of acetaldehyde could be measured in aqueous solution. The calibration curve of acetaldehyde was linear at least up to 40 microM. Its recoveries from human plasma and rat liver homogenate were 96.5 and 95.7%, respectively.

Acetaldehyde↗
PubMed1997

Cytochrome P450-dependent drug oxidation activities in liver microsomes of various animal species including rats, guinea pigs, dogs, monkeys, and humans.

Levels of cytochrome P450 (P450 or CYP) proteins immunoreactive to antibodies raised against human CYP1A2, 2A6, 2C9, 2E1, and 3A4, monkey CYP2B17, and rat CYP2D1 were determined in liver microsomes of rats, guinea pigs, dogs, monkeys, and humans. We also examined several drug oxidation activities catalyzed by liver microsomes of these animal species using eleven P450 substrates such as phenacetin, coumarin, pentoxyresorufin, phenytoin, S-mephenytoin, bufuralol, aniline, benzphetamine, ethylmorphine, erythromycin, and nifedipine; the activities were compared with the levels of individual P450 enzymes. Monkey liver P450 proteins were found to have relatively similar immunochemical properties by immunoblotting analysis to the human enzymes, which belong to the same P450 gene families. Mean catalytic activities (on basis of mg microsomal protein) of P450-dependent drug oxidations with eleven substrates were higher in liver microsomes of monkeys than of humans, except that humans showed much higher activities for aniline p-hydroxylation than those catalyzed by monkeys. However, when the catalytic activities of liver microsomes of monkeys and humans were compared on the basis of nmol of P450, both species gave relatively similar rates towards the oxidation of phenacetin, coumarin, pentoxyresorufin, phenytoin, mephenytoin, benzphetamine, ethylmorphine, erythromycin, and nifedipine, while the aniline p-hydroxylation was higher and bufuralol 1'-hydroxylation was lower in humans than monkeys. On the other hand, the immunochemical properties of P450 proteins and the activities of P450-dependent drug oxidation reactions in dogs, guinea pigs, and rats were somewhat different from those of monkeys and humans; the differences in these animal species varied with the P450 enzymes examined and the substrates used. The results presented in this study provide useful information towards species-related differences in susceptibilities of various animal species regarding actions and toxicities of drugs and xenobiotic chemicals.

Adrenergic beta-Antagonists↗
PubMed1997

Role of eicosanoids in alteration of membrane electrical properties in isolated mesenteric arteries of salt-loaded, Dahl salt-sensitive rats.

1. The role of eicosanoids in altered membrane electrical properties of Dahl salt-sensitive (DS) rats was investigated, by use of conventional microelectrodes technique, in isolated superior mesenteric arteries of DS rats and Dahl salt-resistant (DR) rats fed either a high or low salt diet. 2. The membrane was significantly depolarized in salt-loaded DS rats compared with the other three groups. In addition, the arteries of salt-loaded DS rats exhibited spontaneous electrical activity. 3. Spontaneous electrical activity in salt-loaded DS rats was inhibited by the following: indomethacin, a cyclo-oxygenase inhibitor; ONO-3708, a prostaglandin H2/thromboxane A2 receptor antagonist; OKY-046, a thromboxane A2 synthase inhibitor; nicardipine, a Ca(2+)-channel antagonist and by Ca(2+)-free solution. In addition, spontaneous electrical activity was enhanced by a thromboxane A2 analogue and by prostaglandin H2. Spontaneous electrical activity was unaffected by phentolamine, atropine and tetrodotoxin. 4. Membrane potential in arteries of salt-loaded DS rats was not affected by either indomethacin or ONO-3708. 5. Spontaneous contraction, sensitive to indomethacin, was present, and contractile sensitivity to high potassium solution was enhanced in arteries of salt-loaded DS rats. 6. These findings suggest that eicosanoid action, together with membrane depolarization, may lead to the activation of voltage-dependent Ca(2+)-channels, thereby causing spontaneous electrical activity in mesenteric arteries of salt-loaded DS rats. In addition, tension data suggest that these changes in membrane properties are related to enhanced contractile activities in salt-loaded DS rats. Mechanisms of depolarization remain to be determined.

Animals↗
PubMed1997

Association between hyperinsulinemia and intima-media thickness of the carotid artery in normotensive men.

OBJECTIVES: To determine whether hyperinsulinemia is associated with early atherosclerosis in normotensive men of a work site population. DESIGN AND METHODS: Six hundred and seventeen subjects were screened from 8678 male transport workers for the further examination of cardiovascular disease and diabetes. Subjects aged less than 40 years, those with hypertension or diabetes, or both, and those being administered medications for hyperlipidemia were excluded. Finally, 164 normotensive, nondiabetic subjects were enrolled. The intima-media thickness (IMT) was measured by B-mode ultrasonography with a 7.5 MHz probe. Electrocardiography, a 75 g oral glucose-tolerance test (OGTT) and blood chemistry measurements were also performed. The sum of insulin values (sigmaIRI) and the ratio of the sum of insulin values to blood glucose levels (sigmaIRI/sigmaBG) in the 75 g OGTT were used as markers of hyperinsulinemia. RESULTS: The mean age of the subjects was 52 +/- 5 years (mean +/- SD). In a univariate analysis, IMT was associated with age, systolic blood pressure, body mass index, sigmaIRI, and sigmaIRI/sigmaBG. Multivariate analysis showed that age, total cholesterol, and sigmaIRI (or sigmaIRI/sigmaBG) were independent risk factors for IMT. CONCLUSIONS: These results suggest that, in addition to age and total cholesterol, hyperinsulinemia as assessed by an OGTT is associated with early atherosclerosis in normotensive, nondiabetic men of a work site population.

Arteriosclerosis↗
PubMed1997

Bioactivation of monocrotaline by P-450 3A in rat liver.

Monocrotaline (MCT) is bioactivated in liver cytochrome P-450s to MCT pyrrole (MCTP), which primarily injures the lung endothelium to result in the development of pulmonary hypertension (PH) in rats. However, whether there is a relation between the degree of PH and the activity of liver cytochrome P-450 to convert MCT to MCTP remains unclear. To examine the relation between these physiological and biochemical changes, we first measured the severity of MCT-induced (20 mg/kg) PH in male, female, castrated male, and phenobarbital (PB, liver P-450s inducer)-pretreated male rats. The degree of right ventricular hypertrophy was more severe in PB-pretreated male than in control male rats. It was also more severe in male than in either female or castrated male rats, suggesting that sex-specific P-450s could be involved in the metabolic pathways of MCT in the liver. Further to explore which of the isozymes (2A2, 2C11, and 3A) of P-450s in the liver is responsible for the bioactivation of MCT, we measured the rate of MCTP production in hepatic microsomes by a modified Mattock's method. Treatment of male rats with PB and pregnenolone 16alpha-carbonitrile (PCN), which is the specific inducer of P-450 3A, increased the rate of MCTP production, suggesting that P-450 3A may contribute to the conversion to pyrrole. Therefore we measured the amount of P-450 3A protein by immunoblotting and attempted to inhibit MCT metabolism by using antibodies to P-450 3A. P-450 3A was significantly induced by PCN (6.5-fold) and PB (4.6-fold) treatment and reduced by castration (0.38-fold). The amount of P-450 3A was closely correlated with the production of MCTP, and the conversion of MCT to MCTP was strongly inhibited by antibodies against P-450 3A. These results indicated that P-450 3A was predominantly responsible for the metabolism of MCT to MCTP in rat liver and suggested a tight linkage between the degree of PH and the activity of liver P-450 3A.

Animals↗
PubMed1997

Changes in urinary excretion of pyridinium cross-links during Spacelab-J.

In SLJ-1 we proposed to study three major objectives. They were; 1. hormonal changes associated with fluid and electrolyte metabolism, 2. the effect of space flight on the circadian rhythms of endocrine and metabolic systems, 3. the changes in the indices of the bone and muscle metabolism during space flight. In this report, the changes in the bone metabolism during Spacelab-J will be presented with a special emphasis on urinary excretion of pyridinium cross-links. Timed urine samples from three Japanese payload specialists were obtained for 3 days from May 19 to 21, 1991 (one year before the launch = L-1 year). Immediately before the launch (L-3 to L-0), urine samples were obtained from a payload specialist who was on board the Space Shuttle Endeavor (PS). During the inflight period (flight from September 3 to 10 in 1992), urine samples from the PS were collected by using Urine Monitoring System (UMS). After the landing, they were obtained from the PS for three days (R+0-R+2). Various parameters related to bone metabolism such as hydroxyproline, pyridinium cross-links and calcium were determined. It was noted that excretion of hydroxyproline decreased during the preflight periods when compared with that in the control L-1 year period. The average excretory rate during control period was 846.2 +/- 198.7 milligrams/hour (mean +/- SD), while those in the preflight 474.6 +/- 171.1 milligrams/hour, suggesting the diminished collagen intake during the preflight period. Average excretion rate of pyridinium cross-links during the first 4 mission days (MD0-MD3) was similar to that of preflight and control L-1 year period. However, it was significantly increased during the last 4 mission days (MD4-MD7). It returned to the preflight level during postflight days (R+0-R+2). Increased urinary excretion of calcium during the last 4 mission days were also observed. These results suggest that increase in bone resorption could occur during relatively short stay in microgravity.

Aerospace Medicine↗
PubMed1997

Effect of estrogen on the development of disuse atrophy of bone and muscle induced by tail-supension in rats.

Rat tail-suspension induces disuse atrophy of muscles and bones in hindlimbs. In the present investigation we studied how ovariectomy and estrogen substitution affect the development of the disuse atrophy induced by suspension. Five-week old female Wistar rats were ovariectomized and divided into two groups. One group received intramuscular injection of estradiol dipropionate once a week (OVX-E2 group), and the other received a vehicle injection (OVX group). After the third injection, each group was further divided into two groups, tail-suspended and non-suspended. After 7 days of tail-suspension, a significant decrease in the wet weight of femurs and their Ca and Pi content was observed in the OVX group. However, no significant change in those parameters was observed in the E2 group. In both E2 and OVX groups, a significant decrease in the wet weight of soleus and gastrocnemius muscles was demonstrated after the suspension. This demonstrated that estrogen administration to ovariectomized rats prevents the development of disuse bone atrophy but not that of muscle atrophy, suggesting that estrogen plays important roles in bone remodeling.

Animals↗
PubMed1997

Effect of bisphosphonate administration on the excretion of stress hormones in tail-suspended rats.

We demonstrated that administration of a bisphosphonate, YH529, prevents the development of disuse atrophy of the hind limbs induced by tail-suspension in rats. Since tail suspension is accompanied by an increase in the secretion of stress hormones, we studied whether administration of bisphosphonate affects the secretion of stress hormones during that procedure. Tail suspension was carried out in a metabolic cage by connecting a wire inserted through tail bone to the ceiling of the cage. The control rat received the same treatment but was not suspended. YH529 or a vehicle (PBS=phosphate buffered saline) was administered daily starting 3 days before the commencement of tail suspension. Urine samples were collected before the wire was inserted (day 0), on the day of insertion (day 1) and 3, 5 and 7 days after. In the control rats receiving PBS, urinary excretion of corticosterone and epinephrine did not change throughout the 7-day experimental period. In the control rats receiving YH529, urinary excretion of corticosterone increased significantly on the day of tail-piercing and wiring but then returned to the prior level. This increase was not observed in the control group receiving PBS. In the tail suspended rats, excretion of corticosterone and epinephrine increased significantly in both PBS and YH529 groups, the highest level being observed on the first day of tail suspension. Although statistically not significant, corticosterone excretion on day 1 of tail suspension was higher in the YH529 groups than that in the PBS group. It is thus suggested that administration of YH529 causes an augmented response to stress load.

Animals↗
PubMed1997

Administration of bisphosphonate prevents disuse bone atrophy induced by tail suspension.

We recently demonstrated that osteopenia induced by rat tail-suspension was associated with an initial increase in bone resorption. To study the significance of the increase in early bone resorption for osteopenia, we investigated whether administration of YH529, a third-generation bisphosphonate, prevents the development of osteopenia as evidenced by increased wet weight of the femur, together with its calcium and phosphorus contents, when compared with those of tail-suspended rats treated with the vehicle alone. These results suggested that the initial increase in bone resorption plays an important role in the development of osteopenia induced by tail suspension.

Animals↗
PubMed1997

The inhibitory effect of TMK688, a novel anti-allergic drug having both 5-lipoxygenase inhibitory activity and anti-histamine activity, against bronchoconstriction, leukotriene production and inflammatory cell infiltration in sensitized guinea pigs.

BACKGROUND: TMK688 is being developed as an anti-allergic drug having both 5-lipoxygenase inhibitory activity and anti-histamine activity. METHOD: We compared the inhibition of the late asthmatic responses by TMK688 with that by other anti-allergic agents in actively sensitized guinea pigs, and examined the relationship between 5-lipoxygenase inhibition and the late asthmatic responses. RESULTS: At 1-3.2 mg/kg, TMK688 inhibited the increases in respiratory resistance, leukotriene (LT) B4 and C4 production in the lungs and eosinophil infiltration into the alveoli during the late asthmatic response, whereas the effects tended to lessen at the dose of 10 mg/kg. These effects are thought to be caused by the 5-lipoxygenase inhibitory activity of TMK688 because Azelastine, an anti-allergic drug having potent antihistamine activity, exhibited no effect. ONO-1078, a peptide LT antagonist, inhibited the late-phase bronchoconstriction at a dose of 100 mg/kg p.o., but not the increase in the infiltration of inflammatory cells into the alveoli, suggesting that the late-phase bronchoconstriction is induced, in part, by peptide LTs, i.e. LT C4, D4 and E4 and that the inflammatory cell infiltration may be caused by LTB4. TMK688 inhibited the immediate bronchoconstriction dose-dependently, and the effect was significant at a dose of 10 mg/kg orally. Since Azelastine, Ketotifen and Oxatomide suppressed the bronchoconstriction at far lower doses than did TMK688, the inhibitory effect was mainly caused by its antihistamine activity. CONCLUSIONS: TMK688 appears to be a novel anti-allergic drug having inhibitory effects on both the bronchoconstriction and the infiltration of inflammatory cells during late asthmatic responses.

Animals↗
PubMed1997

Nucleotide sequence of pi class glutathione S-transferase in human fetal liver.

The GST Fpi and GST Ppi, pi class glutathione S-transferase (GST), were purified from human fetal livers and placentas, respectively. Both GST enzymes were indistinguishable each other in their subunit molecular weights, immunochemical properties and substrate specificities. Three clones (pFGP-1, pFGP-2 and pFGP-3) coding for the pi class GST purified from fetal livers were isolated from a human fetal liver cDNA library. The full-length clone encodes a polypeptide comprising 210 amino acid including the initiator methionine. All of these cDNA clones were nearly identical to a human placental cDNA clone, pGpi 2. The pFGP-1 cDNA had only a single base transition accompanied by an amino acid transition in the coding region, at position 313. The pFGP-2 and pFGP-3 cDNAs were also nearly identical to pGpi 2 cDNA, having only a single silent C-->T transition in the coding region, at position 555.

Amino Acid Sequence↗
PubMed1996

Effects of age on levels of cysteine, glutathione and related enzyme activities in livers of mice and rats and an attempt to replenish hepatic glutathione level of mouse with cysteine derivatives.

There was a large statistically significant decrease in the hepatic level of cysteine and glutathione (GSH) in 24 month-old mice compared to young mice, while, cystine and glutathione disulfide (GSSG) contents in the liver did not differ between young and old mice. Activities of cystathionine gamma-lyase and beta-synthase in mouse liver of the 24 month-old group were significantly decreased. In rats, the hepatic levels of cysteine, cystine, GSH and GSSG exhibited no statistically significant change during aging to 30 month. As the rats matured, total hepatic activities of both cystathionine gamma-lyase and beta-synthase increased with maximum levels at 24 months of age and decreased to the same level found in 5 week old for the former and to 22% of that in 5 week old for the latter. Intraperitoneal administration of diethyl maleate to mice led to depletion of hepatic GSH. When N-acetylcysteine and a thiazolidine derivative were intravenously injected after diethyl maleate administration, the hepatic GSH level of mice was restored to the normal level.

Acetylcysteine↗
PubMed1996

Molecular cloning of a novel thyroid hormone-responsive gene, ZAKI-4, in human skin fibroblasts.

Utilizing a method called "differential display of mRNAs by means of polymerase chain reaction", the cDNA fragment of a thyroid hormone-responsive gene ZAKI-4 was cloned from cultured human skin fibroblasts. Northern blot analysis revealed that there were two ZAKI-4 mRNA species (3.4 and 1.4 kilobases (kb)), and they were up-regulated by a physiological concentration of triiodothyronine (T3). This T3 effect was abolished by the treatment with cycloheximide, indicating the possibility that gene ZAKI-4 is regulated by T3 in an indirect fashion, through an intermediate product of T3, rather directly by T3 itself. No effect of T3 on ZAKI-4 mRNA stability suggested that T3 induces the mRNA at the transcriptional level. Rapid amplification of cDNA ends confirmed the presence of two mRNA species. ZAKI-4 mRNA was detected in heart, brain, liver, and skeletal muscle but not in placenta, lung, kidney and pancreas. In skin fibroblasts and skeletal muscle, 3.4-kb mRNA was the major species, whereas 1.4-kb mRNA was dominant in heart, brain, and liver. The sequence analysis suggested that the two mRNA species arise from alternative polyadenylation and code a single protein of 192 amino acids. No homologous protein sequence was found in a data base. Elucidation of the function of ZAKI-4 gene product will provide new insights into an important role of T3 in various organs.

Adolescent↗