Biomedical subjects

M Yamaguchi

Publications and source records attributed to M Yamaguchi.

At least 397 records · Page 22Linked to original sources

PubMed1999

Z-line structural diversity in frog single muscle fiber in the passive state.

The structural changes of the Z-line between small square net (ss) and basket weave (bw) cross-sectional patterns were examined using intact single fibers and mechanically skinned fibers in the passive state to determine if the pattern is related to the sarcomere length (SL) and if the pattern undergoes a reversible transition in low- and high-osmotic medium. Frog single fibers were isolated from the anterior tibial muscle in Ringer's solution. Entirely or partially skinned single fibers were prepared in relaxing solution (also called low-osmotic medium). The high osmotic medium contained 10% polyvinylpyrrolidone (PVP) in relaxing solution. The sarcomere length (SL) of each fiber was measured directly by use of a laser beam or indirectly from electron micrographs with use of a correction factor. The ss and bw forms in cross sections were quantified by analysis of electron micrographs. The results show that the structural change of Z-line occurs around bw << 2.3-2.4 microns << ss (n = 25) and bw << 3.1-3.2 microns << ss (n = 13) in intact single fibers and skinned fibers, respectively. With the quick freeze-freeze substitution method, an intact single fiber with a SL of 2.35 microns showed almost 100% of ss form. The structural transition in cross section was also confirmed in four partially skinned fibers, where patterns went from mostly ss form (intact portion) to mostly bw form (skinned portion) at the SL between 2.40 to 3.20 microns. The reversibility of the change between ss and bw was proved by using low- and high-osmotic medium. The transition and reversion of cross-sectional patterns both occur in the passive state.

Animals↗

PubMed1999

Expression of calcium-binding protein regucalcin and microsomal Ca2+-ATPase regulation in rat brain: attenuation with increasing age.

The expression of calcium-binding protein regucalcin and its effect on the microsomal Ca2+-ATPase activity in rat brain tissues was investigated. The expression of regucalcin mRNA was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis in brain tissues using rat regucalcin-specific primers. Regucalcin concentration in the brain tissues was about 5 x 10(-9)) M as measured using enzyme-linked immunoadsorbent assay (ELISA), and this level was lowered with increasing age (50 weeks old). The presence of regucalcin (10(-9) to 10(-7) M) in the enzyme reaction mixture caused a significant decrease in Ca2+-ATPase activity in the brain microsomes of young rats (5 weeks old). Meanwhile, the enzyme activity was not significantly altered by the addition of calmodulin (1 or 50 microg/ml), calbindin (1 or 10 microg/ml), and S-100 A protein (5 or 25 microg/ml), which are other Ca2+-binding proteins in rat brain. The effect of regucalcin to inhibit microsomal Ca2+-ATPase activity was weakened in the brain of rats with increasing age (50 weeks old). The present study demonstrates that regucalcin is expressed in the brain, and that it can uniquely inhibit Ca2+-ATPase activity in the brain microsomes of rats. The findings suggest that regucalcin plays a role in the regulation of microsomal Ca2+-ATPase activity in rat brain tissues.

Aging↗

PubMed1999

Anabolic effect of daidzein on cortical bone in tissue culture: comparison with genistein effect.

The effect of daidzein on cortical bone in vitro was investigated. Femoral-diaphyseal tissues obtained from elderly female rats were cultured for 24 h in Dulbecco's modified Eagle's medium (high glucose, 4.5%) supplementation with antibiotics and bovine serum albumin. The experimental cultures contained 10(-7) to 10(-5) M daidzein. The presence of daidzein (10(-6) and 10(-5) M) caused a significant increase of alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in bone tissues. This effect was equal to that of genistein (10(-6) and 10(-5) M). Daidzein (10(-5) M) or genistein (10(-5) M)-induced increase of calcium content and alkaline phosphatase activity in bone tissues was completely prevented by cycloheximide (10(-6) M), an inhibitor of protein synthesis. Anabolic effect of daidzein and genistein on bone components was equal to that of 17beta-estradiol (10(-8) M). The effect of isoflavohoids was not enhanced by the addition of 17beta-estradiol. The combination of daidzein and genistein did not have an additive effect. These findings indicate that daidzein has an anabolic effect on bone metabolism in tissue culture in vitro, and that this effect is equal to genistein effect. Isoflavonoids may stimulate bone formation and mineralization.

Alkaline Phosphatase↗

PubMed1999

Stimulatory effect of regucalcin on proteolytic activity in rat renal cortex cytosol: involvement of thiol proteases.

The effect of regucalcin, a calcium-binding protein, on neutral proteolytic activity in the cytosol of rat kidney cortex was investigated. Proteolytic activity was significantly increased in the presence of regucalcin (0.01-0.25 microM) in the enzyme reaction mixture. This increase was not significantly altered by the addition of CaCl, (0.01 and 1.0 mM) or EGTA (1.0 mM), indicating that the effect of regucalcin was independent on Ca2+. The effect of regucalcin to increase proteolytic activity was completely prevented in the presence of N-ethylmaleimide (5 mM), a modifying reagent of thiol groups. Proteolytic activity was clearly elevated by dithiothreitol (5 mM). This elevation was further enhanced by regucalcin (0.1 microM). Meanwhile, the stimulatory effect of regucalcin on proteolytic activity was not significantly altered in the presence of diisopropylfluorophosphate (2.5 mM), an inhibitor of serine proteases. Also, the regucalcin effect was not appreciably changed by the addition of EDTA (2.5 mM), a chelator of metal ions, indicating that it is not involved in metal-related proteases. These results demonstrate that regucalcin can increase proteolytic activity in the cytosol of rat kidney cortex. Regucalcin may activate thiol proteases independent on Ca2+.

Animals↗

PubMed1999

Binding of kidney nuclear proteins to the 5'-flanking region of the rat gene for Ca2+-binding protein regucalcin: involvement of Ca2+/calmodulin signaling.

Ca2+-binding protein regucalcin is expressed in the kidney cortex of rats, as assayed by Northern blot analysis. The existence of kidney nuclear factor which binds to the 5'-flanking region of the rat regucalcin gene was investigated. When nuclear extracts obtained from the kidney cortex of rats were used in gel mobility-shift assays, two protein-DNA complexes were uniquely formed with the DNA fragment containing the 5'-flanking region of the rat regucalcin gene. Competition gel shift experiments indicated the specific binding region of kidney cortex nuclear proteins in the 5'-flanking region of the rat regucalcin gene. The two nuclear protein-DNA complexes were formed with the same mobility in rat kidney cortex and liver, which possess detectable amounts of regucalcin mRNA in Northern blot analysis. The binding activities of nuclear factors from kidney cortex to the 5'-flanking region of the rat regucalcin gene were inhibited by a single intraperitoneal administration of trifluoperazine, an antagonist of calmodulin, to rats. The present study demonstrates that kidney cortex nuclear proteins specifically bind to the 5'-flanking region of the rat regucalcin gene, and that the binding activity may be partly mediated through the Ca2+/calmodulin-dependent process.

Animals↗

PubMed1999

Effect of anti-regucalcin antibody on neutral phosphatase activity in rat liver cytosol: involvement of endogenous regucalcin.

The effect of anti-regucalcin monoclonal antibody on neutral phoshatase activity in rat liver cytosol was investigated. Phosphotyrosine, phosphoserine, and phosphothreonine were used as the substrate toward phosphatase assay. Liver cytosolic phosphatase activity with three phosphoaminoacids was significantly increased in the presence of anti-regucalcin antibody (100 and 200 ng/ml) in the enzyme reaction mixture with calcium chloride (0.1 mM) or EGTA (1.0 mM). The effect of anti-regucalcin antibody was completely abolished in the presence of exogenous regucalcin (1.0 microM), indicating the involvement of endogenous regucalcin. The anti-regucalcin anti body- increased phosphatase activity was not significantly altered in the presence of trifluoperazine (20 microM), an antagonist of calmodulin, or akadaic acid ( 10 microM), an inhibitor of protein phosphatase, although these inhibitors caused a slight decrease in liver cytosolic phosphatase activity. The effect of endogenous regucalcin might be not related to calmodulin, and it was insensitive to okadaic acid. The present findings suggest that endogenous regucalcin is involved in the regulation of protein phasphatase in rat liver cytoplasm.

Animals↗

PubMed1999

Reoxygenation injury of human brain capillary endothelial cells.

1. Many studies have demonstrated that endothelial cells from several species can generate oxygen free radicals when subjected to anoxia and reoxygenation. However, due to the heterogeneity of the endothelium within different organs and species, the effects of superoxide dismutase (SOD), catalase, and allopurinol on reoxygenated cultured cells remain quite controversial. 2. This review outlines the possible sources of oxygen free radicals within brain endothelial cells. 3. We examine the aspects of the effects of SOD catalase and allopurinol on cultured human brain capillary endothelial cells upon reoxygenation. 4. Also, we introduce briefly a method of culturing human brain capillary endothelial cells and present our experimental results on the effects of SOD, catalase, and allopurinol in these cultured cells following anoxia and reoxygenation.

Animals↗

PubMed1999

Expression of calcium-binding protein regucalcin mRNA in the cloned rat hepatoma cells (H4-II-E) is stimulated through Ca2+ signaling factors: involvement of protein kinase C.

The expression of hepatic Ca2+-binding protein regucalcin in the cloned rat hepatoma cells (H4-II-E) was investigated. The change in regucalcin mRNA levels was analyzed by Northern blotting using rat liver regucalcin complementary DNA (0.9 kb of open reading frame). Regucalcin mRNA was expressed in H4-II-E hepatoma cells. This expression was clearly stimulated in the presence of serum (10% fetal bovine serum). Bay K 8644 (2. 5 x 10(-6) M), a Ca2+ channel agonist, significantly stimulated regucalcin mRNA expression in the absence or presence of 10% serum. Dibutyryl cyclic AMP (10(-3) M) did not have a stimulatory effect on the regucalcin mRNA expression. The presence of phorbol 12-myristate 13-acetate (PMA; 10(-6) M) or estrogen (10(-8) M) caused a significant increase in regucalcin mRNA levels in the hepatoma cells cultured in serum-free medium, while insulin (5 x 10(-9) M) or dexamethasone (10(-6) M) had no effect. Bay K 8644-stimulated regucalcin mRNA expression in the hepatoma cells was completely blocked in the presence of trifluoperazine (10(-5) M), an antagonist of calmodulin, or staurosporine (10(-7) M), an inhibitor of protein kinase C. The stimulatory effect of PMA was clearly inhibited in the presence of stauroporine. The present study demonstrates that regucalcin mRNA is expressed in the transformed H4-II-E hepatoma cells, and that the expression is stimulated through Ca2+-dependent signaling factors.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1999

Eosinophil chemotaxis by chemokines: a study by a simple photometric assay.

BACKGROUND: The effects of a panel of 15 chemokines on eosinophil chemotaxis were studied by a new photometric assay which is both less tedious and less laborious than the conventional manual counting methods. Approximately 40 chemokines have been identified to date, but there is little information on the eosinophil migration-inducing ability of chemokines other than CC chemokine receptor (CCR) 3 ligands. METHODS: Eosinophil migration was measured by the Boyden chamber technique with a 96-well multiwell chamber and polycarbonate membrane filter. Eosinophil migration was assessed by determination of the eosinophil peroxidase (EPO) activity, and photometric measurement was performed with a microtiter plate reader. RESULTS: The assay was sensitive enough to detect 200 eosinophils, and the time required was within 4 h. CCR3 ligands, i.e., regulated on activation normal T-cell expressed and secreted (RANTES), eotaxin, eotaxin-2, and monocyte chemoattractant protein (MCP)-3, induced significant migration, while other chemokines showed no significant migration-inducing ability. Although the chemotaxis induction by these chemokines was efficiently inhibited by anti-CCR3 mAb, anti-CCR1 mAb failed to show any inhibitory effects. CONCLUSIONS: The photometric assay is suitable for analyzing a large number of samples. CCR3 ligands are the most important chemokines inducing eosinophil chemotaxis; thus, CCR3 represents a possible therapeutic target for the treatment of allergic diseases.

Antibodies, Monoclonal↗

PubMed1999

Crystal structure of transhydrogenase domain III at 1.2 A resolution.

The nicotinamide nucleotide transhydrogenases (TH) of mitochondria and bacteria are membrane-intercalated proton pumps that transduce substrate binding energy and protonmotive force via protein conformational changes. In mitochondria, TH utilizes protonmotive force to promote direct hydride ion transfer from NADH to NADP, which are bound at the distinct extramembranous domains I and III, respectively. Domain II is the membrane-intercalated domain and contains the enzyme's proton channel. This paper describes the crystal structure of the NADP(H) binding domain III of bovine TH at 1.2 A resolution. The structure reveals that NADP is bound in a manner inverted from that previously observed for nucleotide binding folds. The non-classical binding mode exposes the NADP(H) nicotinamide ring for direct contact with NAD(H) in domain I, in accord with biochemical data. The surface of domain III surrounding the exposed nicotinamide is comprised of conserved residues presumed to form the interface with domain I during hydride ion transfer. Further, an adjacent region contains a number of acidic residues, forming a surface with negative electrostatic potential which may interact with extramembranous loops of domain II. Together, the distinctive surface features allow mechanistic considerations regarding the NADP(H)-promoted conformation changes that are involved in the interactions of domain III with domains I and II for hydride ion transfer and proton translocation.

Amino Acid Motifs↗

PubMed1999

Metallothionein expression correlates with metastatic and proliferative potential in squamous cell carcinoma of the oesophagus.

The goal of this study is to clarify whether the expression of metallothionein (MT) could affect the prognosis and the metastatic potential of squamous cell carcinoma (SCC) of the oesophagus. In paraffin-embedded specimens resected from 57 patients, MT mRNA and protein expressions were detected by in situ hybridization and immunohistochemistry respectively. The expression of MT was evaluated in respect of clinicopathologic variables and patients' survival. MT mRNA expression was significantly associated with the proportion of lymph node metastasis (71% in MT mRNA-positive tumours vs 42% in MT mRNA-negative tumours; P = 0.0343) and that of distant metastasis (29% in MT mRNA-positive tumours vs 5% in MT mRNA-negative tumours; P = 0.0452). In respect of MT protein expression, the frequency of distant metastasis was more common in MT-positive tumours than in MT-negative tumours (30% in MT-positive tumours vs 8% in MT-negative tumours; P = 0.0446). The survival rate of the patients with MT protein-negative tumours was significantly better than that of the patients with MT protein-positive tumours (P = 0.0340). There was a positive correlation between the expression of MT protein and that of proliferating cell nuclear antigen (P = 0.0018). Therefore, we conclude that MT expression, both at the mRNA and protein levels, may be a potential marker predicting metastatic and proliferative activities of oesophageal SCC.

Aged↗

PubMed1999

De novo CD5-positive diffuse large B-cell lymphoma: clinical characteristics and therapeutic outcome.

To determine the clinical significance of CD5 expression in diffuse large B-cell lymphoma (DLBL) without a clinical history of low-grade B-cell lymphoma, we have reviewed the clinical features and therapeutic outcome of 25 patients with de novo CD5-positive DLBL, and compared the results with those of 87 patients with CD5-negative DLBL and 22 patients with mantle cell lymphoma (MCL). The patients with de novo CD5-positive DLBL had clinical characteristics of elderly onset (median age 63, range 37-91), and female predominance (male/female 10/15). 21 (84%) of these patients had extranodal involvement at presentation, with great variation in the sites. In comparison with the patients with CD5-negative DLBL, the treatment outcome for the patients with de novo CD5-positive DLBL was very poor with frequent relapse. The failure-free survival curve was almost identical to that of patients with MCL, showing that standard chemotherapy for DLBL was not effective for most of the patients with de novo CD5-positive DLBL. These findings suggest that de novo CD5-positive DLBL forms a distinct subgroup of DLBL.

Adult↗

PubMed1999

Kinase-independent activity of Cdc2/cyclin A prevents the S phase in the Drosophila cell cycle.

BACKGROUND: The Cdc2-dependent inhibition of S phase is required in G2 for the correct ordering of the S and M phases in yeasts and Drosophila. This function of Cdc2 has been ascribed to its ability to phosphorylate replication factors to prevent the assembly of a preinitiation complex at the origin of replication. Whether this is the sole mechanism of S phase inhibition by Cdc2 in higher metazoans is not known because the pleiotropic functions of this essential cell cycle regulator make genetic analysis difficult. RESULTS: We show that Cdc2 co-expressed with Cyclin A inhibits the S phase in Drosophila salivary glands and diploid abdominal histoblasts. A kinase defective mutant of Cdc2 failed to promote mitosis, but was still able to inhibit the S phase with the same efficiency as the wild-type protein. In addition, Cdc2 and Cyclin A cooperatively inhibit transcriptional activation by the essential S phase regulator E2F. Cdc2 binds to E2F in vitro, and post-transcriptionally promotes its accumulation in vivo. Furthermore, the inhibitory effect of Cdc2 on S phase is overridden by E2F. CONCLUSION: The inhibition of S phase by Cdc2 is achieved in part by a kinase-independent mechanism, which is likely to be mediated by the inhibition of E2F.

Abdomen↗

PubMed1999

Morphometric analysis of collagen: a comparative study in cow and pig skins.

Light and electron microscopic studies were conducted on dermis samples taken from different regions of adult cows and pigs to determine whether there is a correlation between subfibrillar architecture and collagen fibril diameter in dermis tissue. Dermis thicknesses, collagen fibril diameters, subfibrillar architecture diameters, and angles of the helical arrangement of subfibrillar architectures were measured in all dermis samples. The results showed that the differences between subfibrillar architecture diameters in dermis samples from different regions of the same species were not significant and that the diameters of subfibrillar architectures in dermis samples were similar (22-28 nm) in the two species (cow and pig) examined in this study. These findings therefore suggest that the collagen fibril diameter depends on the number of subfibrillar architectures in each fibril.

Animals↗

PubMed1999

Morphological and histochemical analysis of a case of superficial digital flexor tendon injury in the horse.

This report compares the morphology and the concentrations of glycos-aminoglycans (GAGs) in an injured superficial digital flexor tendon (SDFT) of a horse with those of a normal tendon. An injured 6-year-old male Thoroughbred exhibited heat and swelling around the SDFT of the right forelimb. On histopathological examination, exuberant granulation was observed in the affected tendon, with activated tenocytes, angiogenesis, haemorrhage, and infiltration of small numbers of leucocytes. The collagen fibres were loosely packed and irregularly arranged. The diameter of control collagen fibrils was 20-360 nm and that of affected collagen fibrils 20-240 nm. In the analysis of GAGs in the matrix, hyaluronic acid (HA), dermatan sulphate (DS), and chondroitin sulphate (CS) were found to be major components in both control and affected tendons. Increases in DS in the affected tendon were striking. Our observations suggest that fibrillogenesis was activated by increases in DS and decreases in HA and CS. It is also assumed that absence of collagen fibrils of normal thickness and in a parallel arrangement reflected the morphological and biochemical characteristics of fibrillogenesis in the injured tendon. If the inflammatory features of an injured tendon could be altered, it might return eventually to its normal structure.

Animals↗

PubMed1999

The effects of kallidinogenase on choroidal blood flow in a hypertensive rabbit model.

PURPOSE: The purpose of the present study was to investigate the effects of kallidinogenase on chorioretinal circulatory disorder, on the basis of chorioretinal blood flow and fundus findings, in a renal hypertensive rabbit model. METHODS: In a renal hypertensive rabbit model produced according to Goldblatt's method, chorioretinal blood flow was continuously measured by noncontact laser Doppler flowmetry (LDF). Ophthalmography was conducted before and 30 minutes after drug administration. RESULTS: Measurement by LDF revealed 16% reduction in chorioretinal blood flow in the hypertension group compared with the control group. The administration of kallidinogenase dose-dependently increased chorioretinal blood flow in both groups, the hypertension group being more sensitive to kallidinogenase than the control group. In contrast, none of the controls (vinpocetine and DL-alpha-tocopherol nicotinate) exerted effects on chorioretinal blood flow in the hypertension group. Fundus examination demonstrated narrowing of the choroidal arterioles following an increase in blood pressure, and expansion of the arterioles following the administration of kallidinogenase. CONCLUSION: Kallidinogenase was shown to improve ophthalmic circulation by increasing chorioretinal blood flow in renal hypertensive rabbits.

Animals↗

PubMed1999

Phylogenetic analyses of proton-translocating transhydrogenases.

The proton-translocating nicotinamide nucleotide transhydrogenases (TH) provide a simple model for understanding chemically coupled transmembrane proton translocation. To further our understanding of TH structure-function relationships, we have identified all sequenced homologous of these vectorial enzymes and have conducted sequence comparison studies. The NAD-binding domains of TH are homologous to bacterial alanine dehydrogenases (ADH) and eukaryotic saccharopine dehydrogenases (SDH) as well as N5(carboxyethyl)-L-ornithine synthase of Lactococcus lactis and dipicolinate synthase of Bacillus subtilis. A multiple alignment, a phylogenetic tree, and two signature sequences for this family, designated the TH-ADH-SDH or TAS superfamily, have been derived. Additionally, the TH family has been characterized. Phylogenetic analyses suggested that these proteins have evolved without inter-system shuffling. However, interdomain splicing-fusion events have occurred during the evolution of several of these systems. Analyses of the multiple alignment for the TH family revealed that domain conservation occurs in the order: NADP-binding domain (domain III) > NAD-binding domain (domain I) > proton-translocating transmembrane domain (domain II). A topologic model for the proton-translocating transmembrane domain consistent with published data is presented, and a possible involvement of specific transmembrane alpha-helical segments in channel formation is suggested.

Amino Acid Oxidoreductases↗

PubMed1999

Th1-derived cytokine IFN-gamma is a potent inhibitor of eotaxin synthesis in vitro.

Eotaxin potentially plays an integral role in tissue eosinophilia. Inasmuch as Th2-derived cytokine IL-4 has been shown to stimulate eotaxin generation, we investigated here the effect of Th1-derived cytokine IFN-gamma on human eotaxin production. IFN-gamma but not -alpha or -beta potently inhibited tumor necrosis factor (TNF)-alpha-induced eotaxin generation by dermal fibroblasts. The inhibitory effect was unique to eotaxin, because production of IL-8 or monocyte chemoattractant protein (MCP)-1 protein was not affected by the treatment with IFN-gamma. Furthermore, the suppressive effect of IFN-gamma was not cell-type or stimulus specific. The level of eotaxin mRNA increased within 2 h after activation with TNF-alpha and continued to increase up to 72 h. IFN-gamma did not inhibit, but rather augmented the TNF-alpha-induced accumulation of mRNA in the early phase ( approximately 6 h). However, in the later phase, IFN-gamma completely prevented the subsequent elevation of eotaxin mRNA and sustained it at low levels. Although the protective effect of IFN-gamma against allergic inflammation has been assumed to result from its sole regulation of the proliferation of Th2-type T lymphocytes, these results imply that IFN-gamma can also directly act on stromal cells to inhibit eotaxin production and consequently intervene in eosinophil recruitment.

Chemokine CCL11↗