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Biomedical subjects

K Onodera

Publications and source records attributed to K Onodera.

At least 163 records · Page 9Linked to original sources
PubMed1995

The crystal structures of mutated 3-isopropylmalate dehydrogenase from Thermus thermophilus HB8 and their relationship to the thermostability of the enzyme.

The structures of two mutant forms (G240A and L246E/V249M) of 3-isopropylmalate dehydrogenase from Thermus thermophilus HB8 were studied by X-ray crystallography. In the case of G240A, the replacement of glycine by alanine at residue 240 was expected to decrease the thermostability as a result of abnormal contacts between the methyl group of alanine and the peptide chain. However, the normal van der Waals' contacts were achieved owing to a shift in a bundle of beta-strands that yielded a vacant space for the alanine residue. The extended hydrogen bonds within the beta-sheet are the major reason for the decreased thermostability of G240A. The mutations in L246E/V249M are located in an alpha-helix region which is involved in subunit-subunit contact via hydrophobic interaction. Loosening of the subunit-subunit contact owing to ionic repulsion was the major cause of the lower heat stability of L246E/V249M.

3-Isopropylmalate Dehydrogenase↗
PubMed1995

Protective effects of soy protein on the peroxidizability of lipoproteins in cerebrovascular diseases.

To study the mechanism of dyslipoproteinemia, lipoproteins [very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL)] were isolated from stroke patients and healthy persons by ultracentrifugation. Lipoproteins were dialyzed into copper dichloride solution to study the effects of soycreme administration on lipoprotein peroxidation. Blood was drawn from 15 patients with cerebral thrombosis who were not administered soycreme, 10 patients with cerebral thrombosis who were administered soycreme and 11 healthy persons. The lipoproteins were dialyzed into 5 mol/l copper dichloride solution for various lengths of time, and then lipid constituents in the lipoproteins were measured by thin-layer chromatography. After the dialysis, percentages of cholesteryl ester and triglyceride in various lipoproteins decreased significantly (P < 0.05 or 0.01) in both patient groups and in healthy persons. Spot X1 was found between triglyceride and free fatty acid on the thin-layer chromatography, and spot X2 was located between free fatty acid and free cholesterol after dialysis. Spots X1 and X2 reflect lipoprotein peroxidation. Percentages of these spots were higher in VLDL, LDL and HDL in the patient groups than in the healthy subjects. Soycreme administration suppressed the appearance of spots X1 and X2. Furthermore, blood cholesterol concentrations were reduced by the administration of soy protein. Thus, soy may be useful in the prevention and/or treatment of atherosclerosis.

Adult↗
PubMed1995

The crystal structure of thermostable mutants of chimeric 3-isopropylmalate dehydrogenase, 2T2M6T.

A chimeric 3-isopropylmalate dehydrogenase (IPMDH), 2T2M6T, was produced by replacing the amino acid sequences of the Thermus thermophilus enzyme with those of the Bacillus subtilis enzyme from residues 75 to 113. Decreased thermostability of the chimeric enzyme was recovered by either evolutionary engineering (I93L) or site-directed mutagenesis (S82R). The 3-D structures of the mutants have been determined by X-ray diffraction at 2.1 A resolution. Although S82R was refined routinely, I93L required the preliminary rigid-body refinement of each domain. The R-factors were reduced to 0.18 for both mutants. Removal of the unfavorable torsion angle at isoleucine 93 may have made I93L more thermostable than 2T2M6T. In the case of S82R, the replaced arginine residue contributed to the extra hydrogen bond with water molecules. The large replaced residue decreased the entropy of the solvent, which may have caused the improvement in enzyme thermostability. Denaturation by heating may be interpreted from these structural results.

3-Isopropylmalate Dehydrogenase↗
PubMed1995

Transformation of cultured human monocytes by peroxidized low-density lipoprotein.

To study the roles of peroxidized low-density lipoprotein (pox-LDL) during the formation of foam cells from human monocytes, monocytes isolated from normal human blood were incubated with RPMI alone, normal low-density lipoprotein (n-LDL) and copper pox-LDL. The concentrations of total cholesterol (TCH) and lipid peroxide in the human monocyte medium did not change significantly after incubation with RPMI medium alone or n-LDL, but those of TCH decreased slightly after incubation with pox-LDL for 24 h. Triglyceride (TG) concentrations in the culture medium of human monocytes decreased after incubation with all above substances. Ultrastructural studies showed that the monocytes changed to macrophages after incubation with RPMI alone or n-LDL and to foam cells after incubation with pox-LDL for 48 h. We conclude that TGs may be metabolized for ATP production by human monocytes. The energy may play a role in the transformation of monocytes to macrophages, and pox-LDL can induce transformation of monocyte-derived macrophages to foam cells.

Cell Differentiation↗
PubMed1995

[Hepatocellular transplantation in rats with congenital ascorbic acid deficiency].

The purpose of this study was to investigate suitable sites for hepatocyte transplantation in rats with congenital liver enzyme deficiency. Hepatocytes were isolated from ODS-(+)/+ rats, which are congenic to ODS-od/od rats and have hepatic L-gulonolactone oxidase. A total of 1 x 10(7), 1 x 10(7), and 2.5 x 10(6) hepatocytes were respectively transplanted into the peritoneal cavity, spleen, or portal vein of ODS-od/od rats, which are unable to synthesize ascorbic acid (AsA) due to lack of hepatic L-gulonolactone oxidase. After 4 days of oral pretreatment with 0.05% 2-acetylaminofluorene, recipients underwent 70% partial hepatectomy just before transplantation. AsA administration was discontinued at 6 weeks after transplantation. The symptom-free survival rate and the serum AsA level of recipient rats were determined at 6 weeks after discontinuing AsA administration. The symptom-free survival rate of untransplanted rats and recipient rats with intraperitoneal, intrasplenic and intraportal hepatocyte transplantation were 0%, 0%, 60%, and 100%, respectively. The serum AsA levels were 0.20 +/- 0.20 microgram/ml, 0.14 +/- 0.05 microgram/ml, 1.06 +/- 0.26 microgram/ml, and 1.58 +/- 0.61 microgram/ml, respectively. Intrasplenic or intraportal transplantation was able to cure ODS-od/od rats. A subsequent splenectomy study showed that hepatocytes reaching the liver via the splenic vein following intrasplenic hepatocyte transplantation played a major role in this experimental success.

Animals↗
PubMed1995

[Possible roles of brain histamine H3 receptors and the pharmacology of its ligands].

The discovery of the presynaptic histamine H3 receptors confirmed the idea that histamine is a neurotransmitter in the mammalian brain. The H3 receptors (autoreceptors) regulate the release and synthesis of histamine. The H3 receptors also modulate the other neurotransmitters (heteroreceptors). Subclasses of H3 antagonist binding sites were found in the brain (H3A and H3B). The regulation of noradrenaline release is reported to be mediated by H3A rather than H3B. The H3 binding site belongs to the class of receptors coupled to G-proteins. Besides the molecular data, this review focuses on the functional roles of H3 receptors in the brain and discusses the possible use of H3 ligands for neurobehavioral disorders. The pharmacological data of H3 ligands may provide clinical candidates for CNS disorders in which histamine plays important roles in mental and behavioral functions. Especially, H3 antagonists may be useful for CNS disorders such as narcolepsy, dementia, epilepsy, and obesity, while H3 agonists may provide for anxiety, insomnia, migraine. However, these suggestions are still preliminary and further clinical research is needed, although potent and safe novel H3 ligands are being developed.

Animals↗
PubMed1995

[Pneumonitis in a patient who inhaled a fibrinolysin-deoxyribonuclease mixture].

A 56-year-old man was transferred to our department from the department of oral surgery, with a high fever and a cough. He had inhaled a fibrinolysin-deoxyribonuclease mixture (Elase) to treat inflammation in the oral cavity after resection of an oral tumor. A chest X-ray film showed diffuse patchy shadows in both lung fields. Bronchoalveolar lavage fluid had an abnormally high number of lymphocytes and transbronchial lung biopsy revealed interstitial infiltration by lymphocytes and histiocytes, with granulomatous lesions. The patient was treated with steroids, and his clinical condition improved markedly. He accidentally inhaled the drug again, and the coughing and fever began again. The drug lymphocyte stimulation test was positive only for the fibrinolysin-deoxyribonuclease mixture. Based on these findings, we diagnosed pneumonitis induced by this fibrinolysin-deoxyribonuclease mixture. To our knowledge, this is the first reported case of pneumonitis caused by this fibrinolysin-doxyribonuclease mixture.

Administration, Inhalation↗
PubMed1995

Ameliorating effects of histidine on learning deficits in an elevated plus-maze test in mice and the contribution of cholinergic neuronal systems.

We investigated the effects of histidine on scopolamine-induced learning deficits in the elevated plus-maze test in mice. In this test, transfer latency, the time mice took to move from the open arm to the enclosed arm, was used as an index of learning and memory. Intraperitoneal administration of scopolamine (0.5 mg/kg) prolonged the transfer latency on day 2 as compared with that in the saline-treated group. Histidine loading (500, 800 and 1600 mg/kg) reversed the prolongation of the transfer latency induced by scopolamine. This ameliorating effect of histidine was abolished by alpha-fluoromethylhistidine, an inhibitor of histidine decarboxylase, suggesting that histidine itself has no such ameliorating effect. Moreover, the ameliorating effect of histidine was antagonized by a histamine H1-receptor antagonist, pyrilamine, but not by zolantidine, a histamine H2-receptor antagonist. Thus, histamine, a decarboxylated product of histidine, elicited an ameliorating effect on scopolamine-induced learning deficit via histamine H1 receptors in mice. In the biochemical study, histidine significantly decreased acetylcholine (ACh) levels in the cerebral cortex and diencephalon of mice, and also significantly decreased them in the midbrain at a dose of 500 mg/kg. Histidine significantly increased and decreased levels of metabolites of noradrenaline and serotonin, respectively, in the brains of mice. Levels of dopamine and its metabolites were not very affected by histidine in the brains of mice. These findings clearly indicate that there is a close relationship between histaminergic and cholinergic system in the brain, and that histamine may play certain important roles in learning and memory.

Acetylcholine↗
PubMed1995

AQ-0145, a newly developed histamine H3 antagonist, decreased seizure susceptibility of electrically induced convulsions in mice.

We studied the effect of AQ-0145, a newly developed histamine H3-receptor antagonist, on electrically induced convulsions in mice. AQ-0145 significantly decreased the durations of each convulsive phase. The anticonvulsant effect of AQ-0145 was antagonized by mepyramine (pyrilamine) and ketotifen, centrally acting histamine H1-receptor antagonists. Thus, the blockade by histamine H1 antagonists of the AQ-0145-induced decrease in seizure susceptibility indicated that histamine released by AQ-0145 from the histaminergic nerve terminals interacts with the histamine H1 receptors of postsynaptic neurons. These findings fully support the hypothesis that the central histaminergic neuronal system is involved in the inhibition of seizures. It is suggested that the neuropharmacological data on histamine H3 ligands may provide clinical candidates for the CNS disorders in which histamine plays important roles in mental and behavioral functions. In this study, it was suggested that AQ-0145 was a new clinical candidate of H3 ligands.

Adamantane↗
PubMed1995

Effects of thioperamide on the cholinergic system and the step-through passive avoidance test in mice.

We investigated the effects of thioperamide, a histamine H3-receptor antagonist, on a scopolamine-induced learning deficit in the step-through passive avoidance test in mice, and on contents of acetylcholine and choline in the brain. In a behavioral study, thioperamide (20 mg/kg) alone slightly ameliorated scopolamine-induced learning deficit, and pretreatment with zolantidine, a histamine H2-receptor antagonist, significantly enhanced the ameliorating effect of thioperamide. This enhanced ameliorating effect of thioperamide was antagonized by pyrilamine, a histamine H1-receptor antagonist and (R)-alpha-methylhistamine, a histamine H3-receptor agonist, suggesting that thioperamide showed the ameliorating effect via histamine H3 receptors and/or histamine H1 receptors. In the biochemical study, thioperamide (20 mg/kg) in combination with zolantidine (20 mg/kg) significantly increased contents of choline in most of brain regions. These findings suggest that there is a close relationship between histaminergic and cholinergic systems in the brain, and that the histaminergic system may play certain important roles in learning and memory.

Acetylcholine↗
PubMed1994

Neurite outgrowth of PC12 cells is suppressed by wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase.

The effects of wortmannin (WT), an inhibitor of phosphatidylinositol (PI) 3-kinase, on differentiation of PC12 cells were analyzed. WT inhibited PI 3-kinase activity of PC12 cells at a concentration of 10(-7) M in vivo and in vitro. Transient inhibition of PI 3-kinase activity at the time of nerve growth factor stimulation had no effect on activation of the ras protein or neurite formation by the cells. However, continuous inhibition of PI 3-kinase blocked differentiation at the step just before neurite formation. When WT was applied to cells growing neurites, elongation of the neurites was stopped at that step. These results suggest that PI 3-kinase may be involved in neurite elongation.

Androstadienes↗
PubMed1994

Clobenpropit (VUF-9153), a new histamine H3 receptor antagonist, inhibits electrically induced convulsions in mice.

The effect of clobenpropit (VUF-9153), a new histamine H3 receptor antagonist, on electrically induced convulsions was studied in mice. Clobenpropit significantly and dose dependently decreased the duration of each convulsive phase. Its anticonvulsant effects were prevented by pretreatment with (R)-alpha-methylhistamine and imetit (VUF-8325), histamine H3 receptor agonists. These findings suggest that the effect of clobenpropit on electrically induced convulsions is due to an increase in endogenous histamine release in the brain, which is consistent with biochemical results that clobenpropit increased brain histidine decarboxylase activity dose dependently. The anticonvulsive effect of clobenpropit was antagonized by mepyramine, a histamine H1 receptor antagonist, but not by zolantidine, a histamine H2 receptor antagonist, indicating that histamine released by the anticonvulsant effect of clobenpropit interacts with histamine H1 receptors of postsynaptic neurons. The present findings of the effect of clobenpropit on electrically induced convulsions are fully consistent with those of thioperamide as described previously (Yokoyama et al., 1993, Eur. J. Pharmacol. 234, 129), supporting the hypothesis that the central histaminergic neuron system is involved in the inhibition of seizures.

Animals↗
PubMed1994

The differential effects of histamine receptor antagonists on morphine- and U-50,488H-induced antinociception in the mouse.

The effects of thioperamide, an H3 antagonist, and histamine H1 and H2 antagonists (s.c.) on morphine (s.c. or i.c.v.)- and U-50,488H (i.c.v.)-induced antinociception in male ddY mice were examined using the hot-plate (55 degrees C) test. Thioperamide significantly inhibited morphine-induced antinociception, but not U-50,488H-induced antinociception. The suppressive effect of thioperamide on morphine-induced antinociception was reversed by the H1 antagonist pyrilamine, but not by the H2 antagonist zolantidine. On the other hand, pyrilamine significantly potentiated the antinociception induced by morphine, but not that induced by U-50,488H. Zolantidine significantly inhibited morphine-induced antinociception in a dose-dependent manner, but not U-50,488H-induced antinociception. Both astemizole, an H1 antagonist, and ranitidine, an H2 antagonist, which are known to barely cross the blood brain barrier, did not affect morphine-induced antinociception. These results suggest that morphine-induced antinociception may be potentiated by activation of H2 receptors and suppressed by activation of H1 receptors in the brain. Furthermore, neuronal histamine release induced by thioperamide may suppress morphine-induced antinociception through H1 receptors.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1994

2-Thiazolylethylamine, a selective histamine H1 agonist, decreases seizure susceptibility in mice.

The effects of intracerebroventricular (ICV) administration of histamine and its selective agonists on electrically and pentylenetetrazole-induced convulsions in mice were studied. The ICV administration of histamine decreased seizure susceptibility on electrically and pentylenetetrazole-induced convulsions significantly and dose-dependently. The inhibitory effects of histamine were well antagonized by centrally acting histamine H1 antagonists such as pyrilamine (or mepyramine) and ketotifen, but not by a peripherally acting histamine H1 antagonist, astemizole, or a centrally acting H2 antagonist, zolantidine. The ICV administration of 2-thiazolylethylamine, a selective histamine H1 agonist, also decreased seizure susceptibility, which could be antagonized by centrally acting histamine H1 antagonists, whereas dimaprit, a selective histamine H2 agonist, did not affect seizure susceptibility. These findings strengthened the idea that the central histaminergic neuron system plays an inhibitory role in convulsions.

Animals↗
PubMed1994

The orientation of primary cilia during the wound response in 3Y1 cells.

The behavior of the primary cilia of 3Y1 cells in the interphase was investigated by indirect immunofluorescence microscopy and transmission electron microscopy, using an antibody for tubulin. At 4.5 h after scraping a part of a confluent cell sheet, the primary cilia of cells facing the wound were located predominantly forward of the nucleus on the wounded side, and were oriented in the direction of the leading lamellae. Cytoplasmic microtubules (MTs), emanating from around the base of the cilia, were well developed in the leading lamellae on the wounded side. On the other hand, in the cells of an unperturbed area away from the wounded edge, the primary cilia remained randomly distributed near the nucleus. The position and a certain well-defined orientation of a pair of centrioles seem to play an important role for the development of cytoplasmic MTs, and consequently the orientation of the centrioles is controlled by the primary cilia.

Animals↗
PubMed1994

Three-dimensional structures of chimeric enzymes between Bacillus subtilis and Thermus thermophilus 3-isopropylmalate dehydrogenases.

The 3-D structures of two chimeric enzymes (4M6T and 2T2M6T) between the Bacillus subtilis and Thermus thermophilus 3-isopropylmalate dehydrogenases were analysed by X-ray diffraction in order to investigate their different thermostabilities. The structure of 2T2M6T was determined by the difference Fourier method and that of 4M6T by rigid body refinement, as based on the structure of the T. thermophilus enzyme. These structures were refined stereochemically to an R-factor of 0.193 at 2.5 A resolution for 4M6T and to an R-factor of 0.195 at 2.2 A resolution for 2T2M6T. The 3-D structures of 4M6T and 2T2M6T were very close to the structure of the T. thermophilus enzyme, conspicuous differences being at the molecular surface. In particular, 2T2M6T having a larger reduction in thermostability was more closely related to the T. thermophilus enzyme. However, their correlations between C alpha-atom displacements and the root squares of the temperature factors were significantly different from each other.

3-Isopropylmalate Dehydrogenase↗