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Biomedical subjects

K Teraoka

Publications and source records attributed to K Teraoka.

At least 37 records · Page 2Linked to original sources
PubMed1997

Bending strength of synthetic OH-carbonated hydroxyapatite single crystals.

Although hydroxyapatite (HAP) is applied to medical implants because of its biocompatibility, no data on mechanical strength of HAP single crystals were yet available, partly due to the difficulty in obtaining sufficiently large single crystals. In the present study the bending strength of OH-carbonated hydroxyapatite (CHAP) single crystals containing carbonate of 0.09 CO2 wt % prepared hydrothermally was determined in three-point bending tests. The three-point bending tests were performed using a modified ultra micro-hardness tester with a span of 380 micrograms and a bending direction of <210>. The CHAP single crystals were broken in air, water, and air after immersion in alpha minimum essential medium (alpha MEM) + 10% fetal bovine serum (FBS) for 3 weeks. The average bending strength of the CHAP single crystals was 468 +/- 205, 361 +/- 199 and 501 +/- 212 MPa in air, water, and air after immersion in alpha MEM + 10% FBS, respectively. In all cases the maximum strength at each crystal thickness value decreased in inverse proportion to the thickness.

Animals↗
PubMed1997

Peptides derived from cardiovascular G-protein-coupled receptors induce morphological cardiomyopathic changes in immunized rabbits.

An experimental model of early-stage cardiomyopathy was created by immunizing rabbits for 1 year with synthetic peptides corresponding to the sequence of the second extracellular loop of either beta-adrenoceptors or M2-muscarinic receptors. Thirty male rabbits were used and divided into three groups: a control group (n = 10), a group immunized with the peptide corresponding to the beta-adrenoceptor (beta 1 group) (n = 10) and a group immunized with the peptide corresponding to the M2-muscarinic receptor (M2 group) (n = 10). If the sera from both groups of immunized rabbits high-titres of anti-peptide antibodies were found throughout the study period but not in the sera from control rabbits or in the preimmune sera of immunized rabbits. No significant cross-reaction with peptides other than those used for immunization was found. The myocardial receptor density of both immunized groups displayed a strong trend toward receptor up-regulation. This was significant in the beta 1 group but not in the M2 group. Both groups of immunized rabbits displayed significantly enlarged ventricles and thinner walls, as compared with the control group. However, in contrast to the beta 1 group, which showed enlarged cavities in both left and right ventricles, the M2 group was mainly affected in the right ventricles. Moreover, morphological examinations of the hearts of rabbits from both immunized groups demonstrated focal myofibrillar lysis, loss of myofilament, mitochondrial swelling and condensation, sarcoplasmic vacuolation, deposition of dense granules in the sarcoplasm and the myofibrils. One of the sex control rabbit hearts which were examined showed mild degenerative changes in the myocardium and scant mononuclear cell infiltration. However, when all the control rabbit hearts were examined by electron microscopy, no significant alterations were found. These results suggest that immunization by peptides, corresponding to the target sequences for anti-receptor autoantibodies in idiopathic dilated cardiomyopathy, induces morphological changes in the heart similar to those found in the human disease.

Amino Acid Sequence↗
PubMed1997

Possible involvement of intracellular Ca2+ in hyposmosis-evoked catecholamine release from adrenal chromaffin cells.

The influence of hyposmotic conditions on catecholamine release was studied using cultured adrenal chromaffin cells. Incubation of the cells in hyposmotic solution led to the enhancement of catecholamine release in a manner dependent on the reduction of osmolarity. Hyposmosis-evoked catecholamine release was similarly observed in the presence or absence of extracellular Ca2+, and was not significantly affected by organic and inorganic Ca2+ entry blockers. These results indicated that the hyposmosis-evoked release might be associated with a rise in the intracellular Ca2+ concentration. Further studies showed that neither ryanodine nor thapsigargin caused any significant effect on hyposmosis-evoked catecholamine release, whereas pretreatment of chromaffin cells with carbonyl cyanide m-chlorophenyl hydrazone significantly enhanced the hyposmosis-evoked release. Catecholamine release evoked by exposure to hyposmotic medium is therefore thought to be mediated through intracellular Ca2+, which may be mainly sequestered by the mitochondrial pools. Neither caffeine- nor inositol 1,4,5-trisphosphate-sensitive Ca2+ pools seems likely to be involved in hyposmosis-evoked catecholamine release, although the Ca2+ pools that contribute to the elevation of intracellular Ca2+ observed under hyposmotic conditions are not yet completely identified.

Adrenal Medulla↗
PubMed1997

[Distribution of Candida species and mutans streptococci related to oral conditions in elderly persons].

The purpose of this investigation was to find the relationship between the occurrence of Candida species and mutans streptococci at 7 sites (saliva, tongue, mucosa, teeth, clasp, external, and mucosal denture surfaces) in the mouth of 97 elderly persons (males: 43, age: 76.4 +/- 6.7 years; females: 54, age: 75.0 +/- 6.6 years). Among the subjects, there were complete denture wearers (n = 20), partial denture wearers (n = 45), and non-denture wearers (n = 32). Candida species were more significantly (p < 0.001) predominant in complete and partial denture wearers (80% each) than in non-denture (18.8%) wearers. The presence of Candida was highest on the mucosal denture surfaces followed by clasp, tongue, and remaining teeth in that order. Positive correlation were significantly found between the CFU numbers of Candida species and mutans streptococci present on the external surfaces (p < 0.001), natural teeth (p < 0.001), clasp (p < 0.01), and saliva (p < 0.05). A negative correlation (r = -0.503; p < 0.001) was found between the number of teeth and the CFU numbers of Candida species. Moreover, the CFU numbers of both groups of microorganisms also increased in 80-year-old and over persons. Candida species were most predominantly found in persons with poor oral and denture cleanliness.

Age Factors↗
PubMed1996

Saikosaponin b2-induced apoptosis of cultured B16 melanoma cell line through down-regulation of PKC activity.

Saikosaponin (SS) b2 was found to inhibit the proliferation of B16 melanoma cells. To explore this mechanism, we employed flow cytometry to determine the distribution of DNA content. The cell cycle of B16 melanoma cells was accumulated in the G1 phase followed by induction of apoptosis. This suggests that SSb2-induced proliferation inhibition is caused by G1 phase accumulation and that apoptosis induction is G1-phase-accumulation dependent. Phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, did not interfere with the proliferation and did not induce apoptosis of B16 melanoma cells by itself. However, PMA significantly abolished these effects of SSb2 in including proliferation inhibition and apoptosis induction. Down-regulation of the PKC activity may be involved in the effect of SSb2.

Animals↗
PubMed1996

Inhibitory action of palytoxin on ascorbic acid transport into cultured bovine adrenal chromaffin cells.

The effect of palytoxin on the transport of ascorbic acid into cultured bovine adrenal chromaffin cells was examined by measuring the accumulation of radiolabeled ascorbic acid within cells. Ascorbic acid transport into these cells was inhibited by palytoxin in a concentration-dependent manner, and this inhibitory action of palytoxin was shown to be noncompetitive and irreversible. Neither the Na+/K+-pump activity in the intact cells nor the Na+,K+-adenosine 5'-triphosphatase activity in the plasma membranes was significantly influenced by this toxin at concentrations inhibiting ascorbic acid transport. In contrast to the effect of palytoxin on ascorbic acid transport, glucose transport into these cells was not significantly affected by this toxin. These findings indicate that palytoxin can inhibit ascorbic acid transport into adrenal chromaffin cells without affecting Na+,K+-adenosine 5'-triphosphatase activity in the plasma membranes. Furthermore, because palytoxin discriminated between ascorbic acid transport and glucose transport, the data provide new evidence that the transport of ascorbic acid and that of glucose may be mediated by different mechanisms in the adrenal medullary cell.

Acrylamides↗
PubMed1995

Dilated cardiomyopathy defines serum autoantibodies against G-protein-coupled cardiovascular receptors.

In order further to identify the prevalence of anti-receptor autoantibodies in the sera of patients with dilated cardiomyopathy (DCM), we attempted to detect autoantibodies against a series of G-protein-coupled cardiovascular receptors in a well-defined population of DCM patients from Japan. Peptides corresponding to the sequences of the second extracellular loops of the human beta 1 and beta 2 adrenoceptors, alpha 1 adrenoceptors, M2 muscarinic acetylcholine receptors and angiotensin II-1 (AT1) receptors were used as antigens in an enzyme immunoassay to screen the sera from patients with DCM (n = 28). Nine sera from patients with DCM (32%) and 2 sera from healthy subjects (9%) recognized the beta 1 adrenoceptor peptide. Ten sera from patients (36%) and 3 sera from healthy subjects (13%) recognized the M2 receptor peptide. Thirty-six per cent of the patients with autoantibody against the beta 1 adrenoceptor peptide. Ten sera from patients (36%) and 3 sera from healthy subjects (13%) recognized the M2 receptor peptide. Thirty-six per cent of the patients with autoantibody against the beta 1 adrenoceptor had autoantibody against the M2 receptor. However, no significantly high frequencies of autoantibodies against the beta 2 adrenoceptor, alpha 1 adrenoceptor and AT1 receptor were found in DCM patients. Our results demonstrate that a subgroup of patients with DCM have a specific spectrum of autoantibodies which are specifically directed against the second extracellular loops of the beta 1 adrenoceptors and M2 muscarinic receptors rather than other cardiovascular receptors.

Adult↗
PubMed1995

The important role of PKC in controlling polyploidy formation in cultured fibrosarcoma cell line.

Induction of polyploidization by colcemid in cultured fibrosarcoma cells (Meth-A cells) was examined. Activators of protein kinase C (PKC), phorbol 12-myristate 13-acetate (PMA) and ATP, inhibited colcemid-induced polyploidization, but not colcemid-induced cell proliferation cessation. These findings suggest that a down-regulation of PKC activity results in checkpoint "dysfunction" which induces polyploidization and that inhibition of polyploidization induction by PMA and ATP is not a result of the inhibition of colcemid-induced depolymerization of tubulin.

Adenosine Triphosphate↗
PubMed1994

Potentiation of K252a, a protein kinase inhibitor-induced polyploidization by cAMP in cultured fibrosarcoma cell line.

We found that K252a, a potent inhibitor of protein kinases (PK), induced DNA re-replication of Meth-A cells, i.e., DNA synthesis at a higher DNA ploidy without undergoing cytokinesis (polyploidization). The K252a-induced polyploidization was inhibited by phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, suggesting that the polyploidization is caused through inhibition of PKC. By contrast, the polyploidization was potentiated by adenosine 3':5'-cyclic monophosphate (cAMP), a cAMP-dependent protein kinase (PKA) activator. These findings suggest that the cAMP-dependent signaling pathway and diacylglycerol (DAG)-dependent signaling pathway play an important role in regulating the induction of polyploidization in Meth-A cells, through a possible "cross-talk" between the two pathways.

Adenosine Triphosphate↗
PubMed1994

Apoptosis by demecolcine in V79 cells.

Demecolcine (Colcemid), an inhibitor of spindle fiber formation in M phase, induced apoptosis in V79 cells. At a concentration of 0.01 microgram/ml demecolcine, V79 cells proliferated exponentially as well as controls, although temporal M phase accumulation occurred 6 h after the addition of demecolcine. At 0.1 microgram/ml, the cells became hyperploid after remaining in the M phase for some time. Apoptosis occurred in V79 cells exposed to demecolcine at a concentration of 0.03 microgram/ml. Apoptosis was defined as the appearance of a sub-G1 peak in DNA histograms and a ladder pattern of fragmented DNA in gelelectrophoresis.

Animals↗
PubMed1994

Erythrocyte Na+/K(+)-ATPase and membrane and serum lipid profiles: as related to alcohol, body mass index and blood pressure.

Erythrocyte Na+/K(+)-pump activities have been measured in hypertensives, alcohol consumers and obese persons, but the results have been variously reported as decreased, increased or unchanged. We analyzed the relationships between erythrocyte Na+/K(+)-ATPase activities and the membrane and serum lipid profiles in 83 middle-aged men, to clarify the reasons for these inconsistencies. Increases in erythrocyte Na+/K(+)-ATPase activity related closely to decreases in cholesterol to phospholipid (C/P) ratio of the erythrocyte membrane. Decreases in the C/P ratio in turn related closely to elevations of serum triglycerides (TG) with increasing body mass index, and weakly to the volume of alcohol consumed. Thus, erythrocyte Na+/K(+)-ATPase activities depend largely on the membrane and serum lipid profiles as related to body weight and alcohol consumption, and which may be a cause of the previous conflicting findings. Erythrocyte Na+/K(+)-ATPase showed a positive association with blood pressure, independently of age, body mass index and serum gamma-glutamyl transpeptidase levels. Although the biological link of elevated erythrocyte Na+/K(+)-ATPase with the rise in blood pressure remains unclear, it may be a reflection of hyperinsulinemia in the subjects with a higher blood pressure due to overweight or excessive alcohol consumption.

Adult↗
PubMed1994

Lack of relationship between gamma-glutamyl transpeptidase and tyrosine transport in cultured bovine adrenal chromaffin cells.

Effect of gamma-glutamyl transpeptidase (GGTP) inhibitor acivicin on tyrosine transport was investigated in cultured bovine adrenal chromaffin cells. Tyrosine transport into the cells was inhibited by acivicin at the low concentration range. This drug also caused the inhibition of GGTP in the cell lysates, but the concentration required for the inhibition of the enzyme was evidently different from that producing the inhibition of tyrosine transport into the cells. In addition, tyrosine transport was not affected by a GGTP activator hippurate even at the high concentration. These results seem to provide the evidence that GGTP may not be involved in the transport of tyrosine into the adrenal chromaffin cell.

Adrenal Glands↗