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Biomedical subjects

H Yamamura

Publications and source records attributed to H Yamamura.

At least 55 records · Page 3Linked to original sources
PubMed2000

Activation of calpain precedes morphological alterations during hydrogen peroxide-induced apoptosis in neuronally differentiated mouse embryonal carcinoma P19 cell line.

In order to reveal neurodegeneration elicited by reactive oxygen intermediates (ROI), neuronally differentiated cells from mouse embryonal carcinoma P19 cell line were exposed to hydrogen peroxide (H2O2). Enhanced protein-phosphorylation on tyrosine residues was detectable within 5 min of exposure to H2O2, and gradual rises in intracellular free Ca2+ level and in calpain activity were observed. Furthermore, H2O2 stimulation of differentiated P19 cells for 24 h resulted in morphological alterations in somas as well as neurites. Also, within 6 h of H2O2 treatment DNA fragmentation has been detected. Taken together, these results suggest that oxidative stress induces degradation of cytoskeletal proteins presumably resulting from increased intracellular Ca2+ concentration and subsequent activation of calpain.

Animals↗
PubMed2000

l-Ephedrine is a major constituent of Mao-Bushi-Saishin-To, one of the formulas of Chinese medicine, which shows immediate inhibition after oral administration of passive cutaneous anaphylaxis in rats.

OBJECTIVE AND DESIGN: Whether Mao-Bushi-Saishin-To (MBST), one of the formulas of classical Chinese medicine, is effective on 48-h passive cutaneous anaphylaxis (PCA) in rats and which substance in the formula is responsible for its inhibitory action were examined. TREATMENT: In the studies on PCA, MBST (hot water extract of the whole herbal formula), extracts of Ephedra herb (Mao), l-ephedrine and other reference drugs were orally administered immediately or at various times before or 5 min after the antigen challenge. In the experiments on anaphylactic histamine release from rat peritoneal mast cells, l-ephedrine and d-pseudoephedrine were added at 10(-4)-10(-7) g/ml at 30, 10, 3 or 0 min before antigen provocation. RESULTS: The time course study indicated that MBST produced a prompt and long lasting inhibition of PCA. Among the constituents of Mao, l-ephedrine exerted this prompt inhibitory activity, but d-pseudoephedrine did not. Neither pseudoephedrine nor l-ephedrine prevented the anaphylactic histamine release from isolated peritoneal mast cells. CONCLUSIONS: It is strongly emphasised that the rapid suppression of PCA by orally administered l-ephedrine must be exerted by a mechanism distinct from that of suppression produced following gastrointestinal absorption of the drug, because the time required for the inhibition was extraordinarily short. However, direct inhibition of anaphylactic histamine release from isolated mast cells was excluded in this inhibition of PCA.

Animals↗
PubMed2000

Mouse Ror2 receptor tyrosine kinase is required for the heart development and limb formation.

BACKGROUND: A mouse receptor tyrosine kinase (RTK), mRor2, which belongs to the Ror-family of RTKs consisting of at least two structurally related members, is primarily expressed in the heart and nervous system during mouse development. To elucidate the function of mRor2, we generated mice with a mutated mRor2 locus. RESULTS: Mice with a homozygous mutation in mRor2 died just after birth, exhibiting dwarfism, severe cyanosis, and short limbs and tails. Whole-mount in situ hybridization analysis showed that mRor2 was expressed in the branchial arches, heart and limb/tailbuds, in addition to the developing nervous system. The mutants had cardiac septal defects, mainly a ventricular septal defect. In addition, an examination of the skeletal systems revealed that the mutants had shorter limbs, vertebrae and facial structure, with a particular defect in their distal portions, and that almost no calcification was observed in their distal limbs. Histological examination showed abnormalities in the chondrocytes. CONCLUSIONS: Our findings suggest that mRor2 plays essential roles in the development of the heart and in limb/tail formation, in particular cardiac septal formation and ossification of distal portions of limbs and tails.

Animals↗
PubMed2000

Effect of growth hormone on brain oedema caused by a cryogenic brain injury model in rats.

Although growth hormone (GH) is a potential agent to counteract the catabolic response to general and head injuries, the complications of GH treatment have been little studied. To evaluate the safety of GH in head trauma patients, it was investigated whether GH affects brain oedema caused by brain injury, using a rat freeze-injury model. Male Wistar rats (n = 28) were divided into four groups according to the substance injected (GH vs. saline) and whether brain was injured or not. GH (0.8 IU/kg) or saline was injected subcutaneously every 24 hours. In the injury groups, immediately before the first injection of GH, an aluminum rod cooled to -50 degrees C was placed on the right parietal region for 4 minutes, under anaesthesia. At 96 hours after the insult, brain and skeletal muscle were excised and their water content was measured, by drying. Freeze injury of the brain caused an increase in water content in skeletal muscle. GH injection augmented this oedema in skeletal muscle. Freeze injury of the brain also caused an increase in water content in the injured and non-injured hemispheres of brain and cerebellum. GH administration did not exacerbate brain oedema caused by brain injury in this model.

Animals↗
PubMed2000

Purification of a 72-kDa protein-tyrosine kinase from rat liver and its identification as Syk: involvement of Syk in signaling events of hepatocytes.

Syk protein-tyrosine kinase (PTK) has been implicated in a variety of hematopoietic cell responses including immunoreceptor signaling. However, so far, there has been no evidence of the expression of Syk or Syk-related PTK in non-hematopoietic tissues. In this study, we have purified from blood cell-depleted rat liver a 72-kDa cytoplasmic PTK which shows cross-reactivity with anti-Syk antibody. Partial amino acid sequence analysis revealed that this 72-kDa PTK is identical to Syk. Immunohistochemical and RT-PCR analyses demonstrated that Syk is expressed in human hepatocytes and two rat liver-derived cell lines, JTC-27 and RLC-16. Furthermore, Syk is significantly tyrosine-phosphorylated in response to angiotensin II in JTC-27 cells, and angiotensin II-induced MAP kinase activation is blocked by the treatment of cells with a Syk-selective inhibitor, piceatannol. These results suggest that Syk plays an important role in signaling events of hepatocytes, such as signaling steps leading to MAP kinase activation by G-protein-coupled receptors. This is the first report of the expression of Syk in non-hematopoietic tissue.

Amino Acid Sequence↗
PubMed2000

Distinctive functions of Syk N-terminal and C-terminal SH2 domains in the signaling cascade elicited by oxidative stress in B cells.

Syk plays a crucial role in the transduction of oxidative stress signaling. In this paper, we investigated the roles of Src homology 2 (SH2) domains of Syk in oxidative stress signaling, using Syk-negative DT40 cells expressing the N- or C-terminal SH2 domain mutant [mSH2(N) or mSH2(C)] of Syk. Tyrosine phosphorylation of Syk in cells expressing mSH2(N) Syk after H(2)O(2) treatment was higher than that in cells expressing wild-type Syk or mSH2(C) Syk. The tyrosine phosphorylation of wild-type Syk and mSH2(C) Syk, but not that of mSH2(N), was sensitive to PP2, a specific inhibitor of Src-family protein-tyrosine kinase. In oxidative stress, the C-terminal SH2 domain of Syk was demonstrated to be required for induction of tyrosine phosphorylation of cellular proteins, phospholipase C (PLC)-gamma2 phosphorylation, inositol 1,4, 5-triphosphate (IP(3)) generation, Ca(2)(+) release from intracellular stores, and c-Jun N-terminal kinase activation. In contrast, in mSH2(N) Syk-expressing cells, tyrosine phosphorylation of intracellular proteins including PLC-gamma2 was markedly induced in oxidative stress. The enhanced phosphorylation of mSH2(N) Syk and PLC-gamma2, however, did not link to Ca(2)(+) mobilization from intracellular pools and IP(3) generation. Thus, the N- and C-terminal SH2 domains of Syk possess distinctive functions in oxidative stress signaling.

Animals↗
PubMed2000

Conserved smooth muscle contractility and blood pressure increase in response to high-salt diet in mice lacking the beta3 subunit of the voltage-dependent calcium channel.

Voltage-dependent calcium channels are crucially important for calcium influx and the following smooth muscle contraction. Beta subunits of these channels are known to modify calcium currents through pore-forming alpha subunits. Among the four reported independent beta subunits, the beta3 subunit is expressed in smooth muscle cells and thought to compose L-type calcium channels in the tissue. To determine the role of the beta3 subunit in the cardiovascular system, we have analyzed beta3-null mice. Electrophysiological examinations proved the existence of dihydropyridine (DHP)-sensitive. L-type calcium channels in the smooth muscle cells. Beta3-null mice show no apparent changes in smooth muscle contraction and sensitivity to DHP, and normal blood pressure when they are raised on a normal diet, but the 13 subunit deficient mice show elevated blood pressure in response to a high-salt diet, with significant reductions in plasma catecholamine concentrations. Our finding strongly suggests a close relationship between voltage-dependent channels and high blood pressure.

Animals↗
PubMed2000

Reproducible biphasic cutaneous edema induced by topical and repeated application of antigen in sensitized mice.

An allergic dermatitis model was developed by repeated sensitization and challenge with antigen (ovalbumin, OA) over 7 months in mice. ddY mice were sensitized by i.p. injection of OA adsorbed on Al(OH)3 (1 microg OA/2 mg Al(OH)3/animal) once every 3 weeks. Antigen challenge was conducted by injection of OA solution (0.1, 1 and 10 microg/site) into the skin of the hind paw instep 10 d after the respective sensitizations. At the 1st challenge, all the 3 groups showed an immediate edematous response with the peak at 30 min or 1 h after the challenge. The group challenged with the highest dose (10 microg/site) of the antigen developed a clear late-phase edema, which was observed at the 2nd challenge, increasing until the 3rd challenge, reaching a plateau at further challenges. On the other hand, such late phase edema scarcely developed in the group challenged with the lowest dose (0.1 microg/site) of the antigen. The amount of circulating specific IgE antibody increased following repeated sensitizations and challenges in all groups, but there were no significant differences in the levels among them. Mepyramine suppressed the early edema by approximately 50%, yet the late phase edema was unaffected. In conclusion, using Al(OH)3+antigen for sensitization and an appropriate amount of antigen for challenge, reproducible biphasic edematous responses were observed long-term without desensitization. This model may be classified as an acute allergic dermatitis and can be useful for quantitatively evaluating the effects of anti-allergic drugs.

Animals↗
PubMed1999

A novel role for H-Ras in the regulation of very late antigen-4 integrin and VCAM-1 via c-Myc-dependent and -independent mechanisms.

Despite extensive studies on the crucial functions of Ras and c-Myc in cellular proliferation and transformation, their roles in regulating cell adhesion are not yet fully understood. Involvement of Ras in modulating integrin activity by inside-out signaling has been recently reported. However, in contrast to R-Ras, H-Ras was found to exhibit a suppressive effect. Here we show that ectopic expression of a constitutively active H-Rasv12, but not c-Myc alone, in a hemopoietic cell line induces activation of very late Ag-4 (VLA-4, alpha4beta1) integrin without changing its surface expression. Intriguingly, coexpression of H-Rasv12 and c-Myc in these cells results in not only the activation of VLA-4, but also the induction of expression of VCAM-1, the counterreceptor for VLA-4, thereby mediating a marked homotypic cell aggregation. In addition, H-Rasv12-induced VLA-4 activation appears to be partly down-regulated by coexpression with c-Myc. Our results represent an unprecedented example demonstrating a novel role for H-Rasv12 in the regulation of cell adhesion via c-Myc-independent and -dependent mechanisms.

Adjuvants, Immunologic↗
PubMed1999

Involvement of receptor aggregation and reactive oxygen species in osmotic stress-induced Syk activation in B cells.

Syk has been shown to be activated by osmotic stress, however, the mechanisms involved are largely unknown. In this study, we demonstrated that cell shrinkage, rather than osmolarity, was responsible for osmotic stress-induced Syk activation. Osmotic stress-induced Syk activation depended partly upon aggregation of surface receptors. Moreover, intracellular reactive oxygen species were involved in mediating osmotic stress-induced Syk activation, with osmotic stress-induced Syk activation being inhibited by the pretreatment of cells with N-acetyl-cysteine and reduced glutathione. When cells were treated with the combination of sodium chloride and hydrogen peroxide, there was a synergistic activation of Syk. In conclusion, osmotic stress-induced Syk activation required suramin-inhibitable surface receptor aggregation and accumulation of intracellular reactive oxygen species.

Acetylcysteine↗
PubMed1999

Nanomolar concentrations of neuropeptides induce histamine release from peritoneal mast cells of a substrain of Wistar rats.

Substance P causes histamine release from rat peritoneal mast cells probably through direct activation of a specific G protein at micromolar concentrations. We found that peritoneal mast cells of a substrain of Wistar rats (Std:Wistar) responds to nanomolar concentrations of substance P by releasing histamine in a concentration-dependent manner. In addition, potent histamine release from peritoneal mast cells of the substrain rats was also induced by neurokinin A in a concentration-dependent fashion. Histamine release induced by low concentrations of substance P was significantly blocked by a tachykinin NK1 receptor antagonist, CP-96345 [(2S,3S)-cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1-aza bicyclo[2.2.2]octan-3-amine dihydrochloride], whereas that induced by concentrations as high as 10 microM appeared resistant to the antagonist. The concentration-histamine release curve for neurokinin A was parallel-shifted to the right by the drug. A tachykinin NK2 receptor antagonist, SR-48968 [(S)-N-methyl-N[4-(4-acetylamino-4-phenyl piperadino)-2-(3,4-dichlorophenyl)butyl]benzamide], did not influence release stimulated by substance P and neurokinin A. On the other hand, peritoneal mast cells of Sprague-Dawley and other Wistar rats did not respond to neurokinin A. At over 1 microM but not at nanomolar concentrations, substance P caused modest histamine release from peritoneal mast cells of these rats. The results suggest that neurokinin A and nanomolar, but not micromolar concentrations of substance P stimulate tachykinin NK receptors on the peritoneal mast cells of Std:Wistar rat to release histamine.

Animals↗
PubMed1999

Cross-linking of the B cell receptor induces activation of phospholipase D through Syk, Btk and phospholipase C-gamma2.

Phospholipase D (PLD) has been proposed to play a key role in the signal transduction of cellular responses to various extracellular signals. Herein we provide biochemical and genetic evidence that cross-linking of the B cell receptor (BCR) induces rapid activation of PLD through a Syk-, Btk- and phospholipase C (PLC)-gamma2-dependent pathway in DT40 cells. Activation of PLD upon BCR engagement is completely blocked in Syk- or Btk-deficient cells, but unaffected in Lyn-deficient cells. Furthermore, in PLC-gamma2-deficient cells, BCR engagement failed to activate PLD. These results demonstrate that Syk, Btk and PLC-gamma2 are essential for BCR-induced PLD activation.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1999

Subzero nonfreezing storage of isolated rat hepatocytes in University of Wisconsin solution.

BACKGROUND: Various cryopreservation techniques have been investigated to elongate preservation time, however, most have failed to be clinically induced because of damage due to ice crystal formation. Subzero nonfreezing conditions could theoretically reduce organ metabolism without damage due to ice crystal formation. We evaluated the superiority of subzero nonfreezing storage compared with conventional hypothermic storage using isolated rat hepatocytes stored in University of Wisconsin (UW) solution without cryoprotectants. METHODS: Hepatocytes of Wistar rats isolated by collagenase digestion were suspended in UW solution and divided into the following three groups: subzero nonfreezing group (-4 degrees C), zero nonfreezing group (0 degrees C), and control group (4 degrees C). They were stored for 48 hr at the temperatures indicated. After 24 and 48 hr of storage, we carried out a trypan blue exclusion test and a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and measured lactate dehydrogenase release, lactic acid, ATP content, and the ability of hepatocytes to synthesize urea. After 48 hr of storage, morphological differences between the control group and the subzero nonfreezing group were investigated by scanning and transmission electron microscopy. RESULTS: Significant improvements of the trypan blue exclusion test and ATP contents in the subzero nonfreezing group were observed. Lactic acid production was also significantly suppressed in the subzero nonfreezing group compared with that in the control group. The MTT assay value was significantly better at -4 degrees C than at 4 degrees C. The rate of urea synthesis at -4 degrees C was higher than that at 4 degrees C. Electron microscopy revealed that subzero nonfreezing delayed the lethal bleb-forming process of stored hepatocytes, which was followed by mitochondrial swelling, compared with the control group. CONCLUSIONS: Subzero nonfreezing storage (-4 degrees C) in UW solution could provide better preservability for isolated rat hepatocytes with protection against hypoxic cell injury compared with conventional hypothermic storage (4 degrees C).

Adenosine↗
PubMed1999

Optical resolution and absolute configuration of N-benzyloxycarbonyl-alpha-alkoxyglycines

Optical resolution of racemic N-benzyloxycarbonyl-protected alpha-alkoxyglycines, (+/-)-Cbz-Gly(OR)-OH (R = Et and Pr(i)), was achieved by means of fractional crystallization of diastereomeric salts with (+)-(1S,2S)-2-amino-1-phenyl-1,3-propanediol or diastereomeric esters of (+)- or (-)-menthol. The D- and L-configurations were assigned to the (+)- and (-)-Cbz-Gly(OR)-OH, respectively, based on L-enantioselective enzymatic hydrolysis of (+/-)-Cbz-Gly(OR)-OR' (R = Me, Et, and Pr(i); R' = CH(2)CF(3) and Me) using porcine pancreatic lipase and papain. Chiroptical properties and HPLC retention times of D- and L-Gly(OR)-residue (R = Me and Pr(i))-containing peptides were compared in relation to their configurational assignments. Copyright 1999 Wiley-Liss, Inc.

Journal Article↗
PubMed1999

Morbidity and mortality of hospitalized patients after the 1995 Hanshin-Awaji earthquake.

The objective of this study was to provide an overview of the morbidity and mortality of hospitalized patients during the Hanshin-Awaji earthquake. Medical records of 6,107 patients admitted to 95 hospitals (48 affected hospitals within the disaster area and 47 back-up hospitals in the surrounding area) during the initial 15 days after the earthquake were analyzed retrospectively. Patient census data, diagnoses, dispositions, and prognoses were considered. A total of 2,718 patients with earthquake-related injuries were admitted to the 95 hospitals included in our survey, including 372 patients with crush syndrome and 2,346 with other injuries. There were 3,389 patients admitted with illnesses. Seventy-five percent of the injured were hospitalized during the first 3 days. In contrast, the number of patients with illnesses continued to increase over the entire 15-day period after the earthquake. The mortality rates were 13.4% (50/372), 5.5% (128/2,346), and 10.3% (349/3,389) associated with crush syndrome, other injuries, and illness, respectively. The overall mortality rate was 8.6% (527/6,107 patients). Morbidity as well as mortality rates increased with age in patients with both injuries and illnesses. In the initial 15-day period, there was an unprecedented number of patients suffering from trauma, and they converged upon the affected hospitals. Subsequently an increased incidence of illness was observed. This survey underscores the need for adequate disaster response in such an urban situation.

Adolescent↗
PubMed1999

Preparation and properties of novel gramicidin S analogs possessing a tri-, tetra- or pentamethylene bridge between ornithine side chains.

Gramicidin S (GS) analogs in which the Ndelta atoms of the two Orn side chains are linked by an oligomethylene bridge [-(CH2)n-; n=3-5] were prepared via the bis(p-nitrobenzenesulfonyl) derivative [Orn(NBS)2,2']GS. For comparison the nonbridged secondary amino group-containing analog [Orn(Me)2,2']GS was also prepared. 1H NMR and CD spectral analysis indicated that these analogs adopt the same beta-sheet conformation as GS. The antimicrobial activities of these analogs were very similar, but were slightly dependent on the bridge chain length, the trimethylene-bridged analog being the most potent.

Anti-Bacterial Agents↗
PubMed1999

Convenient preparation of [Orn(Tfa)2]- and [Orn(Boc)2, Orn(Tfa)2]gramicidin S, versatile unsymmetrically protected derivatives of gramicidin S.

Treatment of gramicidin S (GS) with trifluoroacetic anhydride afforded a derivative in which only one of the two Orn side chains was trifluoroacetylated in 72% yield, furnishing the first efficient method for the preparation of a monoprotected derivative of GS. The mono(Tfa) derivative [Orn(Tfa)2']GS was treated with di-tert-butyl dicarbonate to yield dually protected derivative [Orn(Boc)2,Orn(Tfa)2']GS from which another monoprotected derivative [Orn(Boc)2]GS was prepared in high yield. These unsymmetrically protected GS derivatives are versatile starting materials for the preparation of various other GS derivatives. As an example of application of the unsymmetrically protected derivatives, a dimeric GS derivative was prepared via a singly p-nitrobenzenesulfonyl(NBS)-activated derivative [Orn(Boc)2,Orn(NBS)2']GS.

Amino Acid Sequence↗