Biomedical subjects

K Ohtani

Publications and source records attributed to K Ohtani.

At least 109 records · Page 6Linked to original sources

PubMed1996

Dammarane-type triterpenoid saponins from Bacopa monniera.

Three new dammarane-type triterpenoid saponins, bacopasaponins A, B and C, of biological interest have been isolated from the reputed Indian medicinal plant Bacopa monniera and identified as 3-O-alpha-L-arabinopyranosyl-20-O-alpha-L-arabinopyranosyl-+ ++jujubogenin, 3-O-[alpha-L-arabinofuranosyl (1--> 2)alpha-L-arabinopyranosyl]pseudojujubogenin and 3-O-[beta-D-glucopyranosyl (1 -->3)[alpha-L-arabinofuranosyl (1--> 2)]alpha-L-arabinopyranosyl]pseudojujubogenin by spectroscopic methods and some chemical transformations. The hitherto undetermined configurations at C-20 and C-22 of pseudojujubogenin were elucidated by phase-sensitive ROESY, and 1H and 13C signals of the saponins were assigned by DEPT, 1H-1H COSY, HSQC and HMBC techniques.

Carbohydrate Sequence↗

PubMed1996

Steroidal saponins from fruits of Tribulus terrestris.

Further studies on the constituents of the fruits of Tribulus terrestris led to the isolation of five new steroidal saponins (terrestrosin A-E), (25R,S)-5 alpha-spirostan-3 beta-ol-3 -O-beta-D-galactopyranosyl(1-2)-beta-D- glucopyranosyl(1-4)-beta-D-galactopyranoside, (25R,S)-5 alpha-spirostan-3 beta-ol-3-O-beta-D-glucopyranosyl(1-4)-[alpha-L- rhamnopyranosyl(1-2)]-beta-D-galactopyranoside, (25R,S)-5 alpha-spirostan-12-on-3 beta-ol-3-O-beta-D-galactopyranosyl (1-2)-beta-D-glucopyranosyl(1-4)-beta-D-galactopyranoside, hecogenin 3-O-beta-D-galactopyranosyl)1-2)-[beta-D- xylopyranosyl(1-3)]-beta-D-glucopyranosyl(1-4)-beta-D-galactopyranoside and (25R,S)-5 alpha-spirostane-2 alpha, 3 beta-diol-3- O-beta-D-galactopyranosyl(1-2)-beta-D-glucopyranosyl(1-4)-beta-D- galactopyranoside, together with five known steroidal saponins, desgalactotigonin, F-gitonin, desglucolanatigonin, gitonin and tigogenin 3-O-beta-D- xylopyranosyl)1-2)-[beta-D-xylopyranosyl)1-3)]-beta-D-glucopyranosyl)1-4 )- [alpha-L-rhamnopyranosyl(1-2)]-beta-D-galactopyranoside. The structures of the new saponins were elucidated on the basis of spectroscopic analyses, including two-dimensional NMR techniques, and chemical reactions.

Chromatography, High Pressure Liquid↗

PubMed1996

Bacopasaponin D--a pseudojujubogenin glycoside from Bacopa monniera.

A new dammarane-type pseudojujubogenin glycoside, bacopasaponin D, has been isolated from the reputed Indian medicinal plant Bacopa monniera and defined as 3-O-[alpha-L-arabinofuranosyl(I-->2)beta-D-glucopyranosyl]pseudojujub ogenin by spectroscopic methods and some chemical transformations. The 13C signals of the saponin were assigned by DEPT, 1H-1H COSY and HSQC techniques.

Carbohydrate Conformation↗

PubMed1996

Acarbose partially prevents the development of diabetes mellitus by multiple low-dose streptozotocin administration.

Prophylactic insulin treatment prevents the development of hyperglycemia in animal models of insulin-dependent diabetes mellitus. Acarbose is a new antidiabetic drug which improves hyperglycemia by inhibiting alpha-glucosidase. In the present study, we determined the preventive effect of acarbose against multiple low-dose streptozotocin (MLDSTZ)-induced diabetes mellitus. The male ICR mice were fed acarbose (40 mg/100 g) containing powdered chow before the start of STZ administration. The mice were sacrificed at 3 and 10 days after the final STZ injection. MLDSTZ decreased serum immunoreactive insulin (IRI) levels and increased plasma glucose levels. Acarbose administration tended to decrease plasma glucose and serum IRI levels were significantly reduced in vehicle-treated mice. Acarbose administration significantly attenuated the degree of inflammation and destruction in pancreatic islets after MLDSTZ administration. In conclusion, acarbose-induced attenuation of acute hyperglycemia following MLDSTZ partially prevents the severity of pancreatic islet damage.

Acarbose↗

PubMed1996

Taste-modifying triterpene glycosides from Staurogyne merguensis.

Five new oleanane-type triterpene glycosides named strogins 1-5 were isolated from leaves of Staurogyne merguensis. Their structures were determined on the basis of chemical and spectral evidence. After strogins 1, 2 and 4 were held in mouth, water elicited a sweet taste. On the other hand, strogins 3 and 5 had no activity. The structure-activity relationship is discussed.

Glycosides↗

PubMed1996

Characterization of a toxin-deficient Clostridium perfringens strain, KZ1340.

Clostridium perfringens KZ1340, previously classified as Clostridium plagarum, is an isolate from Antarctic soil, and was identified as an alpha-, theta-, and kappa-toxin non-producing variant. On Southern hybridization, the variant was found to be defective in the pfoA (theta-toxin) gene, but the plc (alpha-toxin) and colA (kappa-toxin) genes were present on the same EcoRI fragment as in the standard strain, NCTC8237. Northern analysis revealed that mature plc mRNA was transcribed in KZ1340 though less efficiently than in NCTC8237, while no mature colA mRNA was present in KZ1340. After transformation of the pfoA and plc genes into the KZ1340 via shuttle vector, pJIR418, the pfoA gene was successfully expressed but the plc gene was not efficiently expressed, suggesting that in KZ1340 there is negative regulation of plc gene expression. Toxin-deficient C. perfringens KZ1340 might be a suitable host for expression analysis of the pfoA gene and other clostridial virulence genes, if expressed efficiently, because it produces a small amount of extracellular toxins.

Bacterial Toxins↗

PubMed1996

The virR/virS locus regulates the transcription of genes encoding extracellular toxin production in Clostridium perfringens.

Extracellular toxin production in Clostridium perfringens is positively regulated by the two-component regulatory genes virR and virS. Northern (RNA) blots carried out with RNA preparations from the wild-type strain 13 and the isogenic virR and virS mutants TS133 and JIR4000 showed that the virR and virS genes composed an operon and were transcribed as a single 2.1-kb mRNA molecule. Primer extension analysis led to the identification of two promoters upstream of virR. Hybridization analysis of the mutants and their complemented derivatives showed that the virR/virS system positively regulated the production of alpha-toxin (or phospholipase C, theta-toxin (perfringolysin O), and kappa-toxin (collagenase) at the transcriptional level. However, the modes of regulation of these genes were shown to differ. The theta-toxin structural gene, pfoA, had both a major and a very minor promoter, with the major promoter being virR/virS dependent. The colA gene, which encodes the kappa-toxin, had two major promoters, only one of which was virR/virS-dependent. In contrast, the alpha-toxin structural gene, p1c, had only one promoter, which was shown to be partially regulated by the virR and virS genes. Comparative analysis of the virR/virS-dependent promoters did not reveal any common sequence motifs that could represent VirR-binding sites. It was concluded that either the virR/virS system modulates its effects via secondary regulatory genes that are specific for each toxin structural gene or the VirR protein does not have a single consensus binding sequence.

Bacterial Proteins↗

PubMed1996

Expression of the HsOrc1 gene, a human ORC1 homolog, is regulated by cell proliferation via the E2F transcription factor.

The initiation of DNA replication in Saccharomyces cerevisiae requires the action of a multisubunit complex of six proteins known as the origin recognition complex (ORC). The identification of higher eukaryotic homologs of several ORC components suggests a universal role for this complex in DNA replication. We now demonstrate that the expression of one of these homologs is regulated by cell proliferation. Expression of the human Orc1 gene (HsOrc1) is low in quiescent cells, and it is then dramatically induced upon stimulation of cell growth. In contrast, expression of the HsOrc2 gene does not appear to be similarly regulated. We have isolated the promoter that regulates HsOrc1 transcription, and we show that the promoter confers cell growth-dependent expression. We also demonstrate that the cell growth control is largely the consequence of E2F-dependent negative transcription control in quiescent cells. Activation of HsOrc1 transcription following growth stimulation requires G1 cyclin-dependent kinase activity, and forced E2F1 expression can bypass this requirement. These results thus provide a direct link between the initiation of DNA replication and the cell growth regulatory pathway involving G1 cyclin-dependent kinases, the Rb tumor suppressor, and E2F.

Base Sequence↗

PubMed1996

Cytotoxicity of 7-ketocholesterol toward cultured rat hepatocytes and the effect of vitamin E.

The effects of 7-ketocholesterol on rat hepatocytes prepared by collagenase perfusion were examined. The viability of cells incubated with 100 microM 7-ketocholesterol was significantly lower than those with cholesterol, although the LDH activity in the cultured medium remained unchanged during the incubation. Hepatocytes treated with 7-ketocholesterol produced large amounts of .NO and O2- in the early stage of incubation. Treatment of the hepatocytes with Carboxy-PTIO, which selectively scavenged .NO, or with L-NMMA, an inhibitor of .NO synthase, increased the cell viability. The addition of 7-ketocholesterol to the culture medium tended to increase the ratio of total sterol to phospholipid of the hepatocytes in a time-dependent manner without changing the content of phospholipid. No lipid peroxidation or oxidation of the cellular SH groups, protein SH and glutathione, was apparent. Vitamin E added 1 h before the addition of 7-ketocholesterol prevented the hepatocytes from cell death by suppressing the incorporation of 7-ketocholesterol into the hepatocytes and by scavenging O2-.

Animals↗

PubMed1996

Pioglitazone hydrochloride stimulates insulin secretion in HIT-T 15 cells by inducing Ca2+ influx.

Pioglitazone hydrochloride (AD-4833), one of the thiazolidinedione analogs, is a new anti-diabetic agent which improves peripheral insulin resistance in diabetic patients. We determined the direct effect of AD-4833 on insulin secretion in HIT-T 15 cells. The effects of AD-4833 (10(-7) M to 10(-5) M) on insulin secretion were examined in 3 and 7 mM glucose-containing F-12 K media. The addition of 10(-5) M AD-4833 significantly increased insulin secretion in both media, but its stimulatory effect was more potent in the medium containing 7 mM glucose. The addition of 10(-5) M AD-4833 caused an immediate, significant increase in cytosolic free Ca2+ concentration ([Ca2+]i). Nifedipine at all concentrations from 10 to 1000 nM significantly attenuated insulin secretion by 10(-5) M AD-4833. In addition, 10(-5) M AD-4833 failed to stimulate insulin secretion in the CA(2+)-free Kreb's-Ringer bicarbonate buffer. These data indicated that AD-4833 stimulates in vitro insulin secretion in HIT-T 15 cells, perhaps by inducing Ca2+ influx.

Animals↗

PubMed1996

Disseminated nontuberculous mycobacteriosis caused by mycobacterium kansasii in a patient with myelodysplastic syndrome.

A 38-year-old man with pancytopenia due to myelodysplastic syndrome exhibited persistent pyrexia and mediastinal lymphadenopathy. A biopsy specimen of the lymph nodes showed diffuse infiltration of epitheloid cells, including acid-fast bacilli identified as Mycobacterium kansasii. Cultures from gastric lavage and stool yielded M. kansasii, and granulomas were found in the bone marrow. A diagnosis of disseminated nontuberculous mycobacteriosis (DNTM) was established. The patient's condition improved after treatment with isoniazid, rifampicin, ethambutol and granulocyte colony-stimulating factor. Although DNTM due to M. kansasii is rare in Japan, it should be recognized as a possible cause of opportunistic infections.

Adult↗

PubMed1996

15 alpha-hydroxylation of a bile acid analogue, sodium 3 alpha,7 alpha-dihydroxy-25,26-bishomo-5 beta-cholane-26-sulfonate in the hamster.

The metabolism of 3 alpha,7 alpha-dihydroxy-25,26-bishomo-5 beta-cholane-26-sulfonate (bishomoCDC-sul), the sulfonate analogue of bishomochenodeoxycholic acid, and its effect on biliary bile acid composition were studied during chronic administration in the hamster. After oral administration of radiolabeled bishomoCDC-sul, more than 80% of the radioactivity was excreted into the feces within 7 days, both as the unchanged sulfonate (38.5%) and two more polar metabolites (50.0% and 11.5%). The half time of the fecal excretion was 1.6 days. In gallbladder bile, the unchanged sulfonate and its major metabolite accounted for 19.1% and 19.8% of total bile acids, respectively. In another experiment, hamsters were fed bishomoCDC-sul with antibiotics to evaluate the site of biotransformation. Even when the number of intestinal microorganisms was greatly reduced, the same three metabolites were found in the feces: bishomoCDC-sul (44.0%) and the two polar metabolites (30.8% and 25.1%). The major metabolite was isolated from feces of the hamsters fed bishomoCDC-sul without antibiotics. Its chemical structure was identified by mass spectrometry and nuclear magnetic resonance spectroscopy as the 15 alpha-hydroxylated derivative, namely sodium 3 alpha,7 alpha,15 alpha-trihydroxy-25,26-bishomo-5 beta-cholane-26-sulfonate. These results indicate that after oral administration, the sulfonate analogue of bishomochenodeoxycholic acid underwent enterohepatic circulation like a natural bile acid and was transformed, in part, into the 15 alpha-hydroxylated derivative and another more polar metabolite in the liver of hamsters. There was no evidence that bishomoCDC-sul was dehydroxylated to a lithocholic acid analogue during enterohepatic cycling.

Animals↗

PubMed1996

[Computed tomography and magnetic resonance imaging of the brain in congenital rubella syndrome].

Nine children with congenital rubella syndrome were examined with respect to the relation between clinical symptoms and the findings of computed tomography (CT, 9/9 cases) and magnetic resonance imaging (MRI, 7/9 cases). All patients had deafness, and three had relatively severe sequelae in the central nervous system (CNS), such as mental retardation (MR), cerebral palsy (CP) or microcephaly. In four patients, dilatation of the lateral ventricles was found by CT; in four patients, low-density areas were noted in the periventricular white matter and/or the subcortical white matter; one patient showed a spotty calcified area in the lenticula. No abnormal findings were found by CT in other three patients. MRI in seven children demonstrated areas of prolonged T1 and T2 relaxation times in the white matter in all of them. In relation to clinical symptoms, five patients without dilatation of the lateral ventricles had no sequelae except deafness. On the other hand, in four patients with dilation of the lateral ventricles, three had MR, CP or microcephaly. This study showed that there was a close relation between the ventricular dilatation and sequelae with in CNS, whereas abnormal intensity areas in the white matter found by MRI were not related well to the sequelae of CNS.

Brain↗

PubMed1996

[Appearance of cytoplasmic processes of megakaryocytes in the peripheral blood in a Munchausen syndrome with factitious anemia].

Many cytoplasmic processes of megakaryocytes were seen in a 45-year-old male patient of Munchausen syndrome with sustained severe anemia due to repeated self-blood drawing. He had a past history of repeated infection and removal of skin-graft transplanted for giant congenital melanocytic nevus due to self-infliction (later confessed by the patient). On the admission, he presented with high fever (39 approximately 40 degrees C) and severe sustained anemia refractory to repeated blood transfusions. Any specific clinical data indicating bleeding or hemolysis were not found. Self-blood drawing was discovered by a nurse on his 27th hospital day. Syringes and needles for blooddrawing were also found. He recovered from anemia under intensive watching without any specific treatment. He confessed that the high fever was artificial. It was of interest that cytoplasmic processes of megakaryocytes were seen in the peripheral blood film until he recovered from anemia for one month. The serum level of erythropoietin was elevated (1540 mU/ml), but not significantly was that of thrombopoietin (1.54 fmol/ml). This case was considered to be valuable to understand the mechanism of platelet-production by megakaryocytes at persistent bleeding.

Anemia↗

PubMed1995

Regulation of the cyclin E gene by transcription factor E2F1.

A variety of results point to the transcription factor E2F as a critical determinant of the G1/S-phase transition during the cell cycle in mammalian cells, serving to activate the transcription of a group of genes that encode proteins necessary for DNA replication. In addition, E2F activity appears to be directly regulated by the action of retinoblastoma protein (RB) and RB-related proteins and indirectly regulated through the action of G1 cyclins and associated kinases. We now show that the accumulation of G1 cyclins is regulated by E2F1. E2F binding sites are found in both the cyclin E and cyclin D1 promoters, both promoters are activated by E2F gene products, and at least for cyclin E, the E2F sites contribute to cell cycle-dependent control. Most important, the endogenous cyclin E gene is activated following expression of the E2F1 product encoded by a recombinant adenovirus vector. These results suggest the involvement of E2F1 and cyclin E in an autoregulatory loop that governs the accumulation of critical activities affecting the progression of cells through G1.

Animals↗

PubMed1995

E2F-1 accumulation bypasses a G1 arrest resulting from the inhibition of G1 cyclin-dependent kinase activity.

Numerous experiments have defined a critical role for the G1 cyclins and associated kinases in allowing a normal progression of cells from a quiescent state, through G1, and into S phase. We now demonstrate that G1 cyclin-dependent kinase activity is critical for the accumulation of E2F activity late in G1. Moreover, E2F-1 overexpression can overcome a G1 arrest caused by the inhibition of G1 cyclin-dependent kinase activity, consistent with E2F activation being an important consequence of the action of G1 cyclins. E2F-1 also overcomes a G1 block caused by gamma irradiation and leads to an apparent complete replication of the cellular genome and entry into mitosis. This E2F-1-mediated induction of S phase and mitosis is not accompanied by the rise in either cyclin D-associated kinase activity or cdk2 activity that is normally observed during the G1 phase of the cell cycle. We conclude that one key function for G1 cyclin-dependent kinase activity is the activation of E2F-1, that the accumulation of E2F activity may be sufficient to allow initiation and completion of S phase, but that additional events, including G1 cyclin kinase activity, are likely necessary for a normal proliferative event.

Blotting, Western↗

PubMed1995

Kinetic studies on the interaction of nonlabeled antagonists with the angiotensin II receptor.

Angiotensin AT1 receptor antagonists are divided into two types, surmountable and insurmountable, based on the way they inhibit angiotensin II-induced vasoconstriction. To elucidate what causes the difference, we studied how antagonists associate with and dissociate from AT1 receptor sites in rat liver membranes. Three antagonists, 6-propyl-7-oxo-4[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-4,7- dihydropyrazolo[1,5-a]pyrimidine-3-carboxylic acid (SRL1080227), 2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H- benzimidazole-7-carboxylic acid (CV-11974) and 2-butyl-3-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-3H-imidazo- [4,5-b]pyridine (FK739), showed competitive antagonism when they were added simultaneously with [125I]angiotensin II, but CV11974 and SRL1080227 showed apparently noncompetitive antagonism when membranes were preincubated with each antagonist. The longer the preincubation time with CV11974 or SRL1080227 was, the more effectively the antagonist inhibited [125I]angiotensin II binding, while the inhibition by FK739 did not change with the preincubation time. To estimate their dissociation rate from the receptor binding site, we studied [125I]angiotensin II binding to membranes which had been preincubated with each antagonist and washed twice. Membranes pretreated with FK739 completely recovered the ability to bind [125I]angiotensin II with a period of 60 min, while membranes preincubated with CV11974 did not read this level of recovery. [125I]angiotensin II binding to membranes preincubated with SRL1080227 increased gradually, but did not reach the control level during the experiment. The kinetic properties of SRL1080227, CV11974 and FK739 were consistent with their characteristic modes in inhibiting angiotensin II-induced contraction of isolated rabbit aorta and decreasing blood pressure of spontaneously hypertensive rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin Receptor Antagonists↗

PubMed1995

Interleukin-1 inhibits keratan sulfate production by rabbit chondrocytes: possible role of prostaglandin E2.

We investigated the importance of prostaglandin E2 (PGE2) release in interleukin-1 (IL-1)-induced inhibition of aggrecan synthesis by chondrocytes. Keratan sulfate (KS) production was measured in parallel with PGE2 release in chondrocytes. IL-1 inhibited KS production and stimulated PGE2 release. In the presence of PGE2, there was a dose-dependent decrease in baseline KS production. Indomethacin and dexamethasone partially blocked the IL-1-induced PGE2 release while KS production recovered. Our results suggest that IL-1 inhibits KS production, in part, by stimulating the release of PGE2.

Animals↗