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Y Shibasaki

Publications and source records attributed to Y Shibasaki.

At least 55 records · Page 3Linked to original sources
PubMed1999

Cellular roles in relapse processes of experimentally-moved rat molars.

This histological study was designed to clarify the relapse processes of rat molars following orthodontic tooth movement by the Waldo method. An elastic band was inserted between the upper first and second molars, and removed either 7 or 21 days later. The relapse processes of first molars were examined at 1 or 4 days after completing the 7-day-insertion and at 5 or 10 days after the end of the 21-day-insertion. At the end of the 7-day-insertion period, the mean interdental space was 158 microns, but decreased rapidly, reaching 44 microns by 1 day after removal, and 16 microns by day 4. In the periodontal ligament (PDL) compressed by elastic band insertion, partial hyalinization and/or mineralization occurred. The stretched PDL consisted of irregularly-distributed, thin principal fibres, approximately 2.4 microns in diameter. On days 1 and 4 after removal, osteoclasts, macrophage-like cells and fibroblast-like cells were localized around hyalinized tissues, but thick principal fibres, approximately 3.8 microns in diameter, were regularly distributed throughout the PDL proper. The mean interdental space after the 21-day-insertion was 536 microns, but this had decreased to 108 microns by day 5, and 71 microns by day 10. On day 5 after removal, numerous osteoclasts were evenly distributed in the compressed PDL, while thick principal fibres, approximately 3.5 microns, were present in the stretched PDL. These results suggest that, during relapse of experimentally-moved rat molars, (i) rapid remodelling of the PDL and surrounding alveolar bones is the main cause of tooth relapse and (ii) hyalinized and/or mineralized tissues occurred by compression are rapidly resorbed by osteoclasts, macrophage-like cells and fibroblast-like cells.

Alveolar Process↗
PubMed1999

Angiotensin II type 2 receptor overexpression activates the vascular kinin system and causes vasodilation.

Angiotensin II (Ang II) is a potent vasopressor peptide that interacts with 2 major receptor isoforms - AT1 and AT2. Although blood pressure is increased in AT2 knockout mice, the underlying mechanisms remain undefined because of the low levels of expression of AT2 in the vasculature. Here we overexpressed AT2 in vascular smooth muscle (VSM) cells in transgenic (TG) mice. Aortic AT1 was not affected by overexpression of AT2. Chronic infusion of Ang II into AT2-TG mice completely abolished the AT1-mediated pressor effect, which was blocked by inhibitors of bradykinin type 2 receptor (icatibant) and nitric oxide (NO) synthase (L-NAME). Aortic explants from TG mice showed greatly increased cGMP production and diminished Ang II-induced vascular constriction. Removal of endothelium or treatment with icatibant and L-NAME abolished these AT2-mediated effects. AT2 blocked the amiloride-sensitive Na(+)/H(+) exchanger, promoting intracellular acidosis in VSM cells and activating kininogenases. The resulting enhancement of aortic kinin formation in TG mice was not affected by removal of endothelium. Our results suggest that AT2 in aortic VSM cells stimulates the production of bradykinin, which stimulates the NO/cGMP system in a paracrine manner to promote vasodilation. Selective stimulation of AT2 in the presence of AT1 antagonists is predicted to have a beneficial clinical effect in controlling blood pressure.

Actins↗
PubMed1999

Differential kinetics of circulating angiotensin IV and II after treatment with angiotensin II type 1 receptor antagonist and their plasma levels in patients with chronic renal failure.

BACKGROUND: Angiotensin II (Ang II) C-terminal hexapeptide (referred to as Ang IV) possesses the characteristics of a real hormone with specific receptors and biological effects. Clinical application of Ang II type 1 receptor (AT1-R) antagonists cause an increase in plasma Ang II level, which may result in enhanced production of Ang IV. PATIENTS AND METHODS: In this study, we measured plasma Ang IV and Ang II levels in patients with chronic renal failure (CRF), and also examined the changes in Ang IV and Ang II levels after administration of an ATI-R antagonist. RESULTS: Ang II and Ang IV levels in CRF patients untreated with hemodialysis (n = 16) were 15.8+/-3.6 and 6.0+/-1.1 pg/ml, respectively, which did not differ significantly from Ang II (20.6+/-2.4) and Ang IV levels (8.6+/-1.1) in normal controls (n = 23). The ratio of Ang IV to Ang II was 38%, similar to that in the controls (41%). Ang II or Ang IV levels in CRF patients treated with hemodialysis (n = 12) were also similar to the control values. Ang IV levels had a significant correlation with Ang II levels (r = 0.59). When hypertensive patients were treated with an AT1-R antagonist candesartan for 7 days, Ang II and Ang IV levels were increased 5.5- and 4.1-fold relative to the control levels, respectively. Ang II levels 28 and 56 days after treatment were significantly lower than those 7 days after treatment, whereas Ang IV levels did not differ significantly from those 7 days after treatment. Similar differential kinetics in Ang II and Ang IV levels after long-term (90 days) treatment with an AT1-R antagonist was also confirmed in experiments using rats. Significant decrease in blood pressure continued during long-term treatment with an AT1-R antagonist. CONCLUSION: These findings demonstrated that plasma Ang IV levels in patients with CRF did not differ significantly from those in normal subjects, and that treatment with an AT1-R antagonist caused marked increases in both Ang II and Ang IV levels. In contrast, during long-term treatment plasma Ang II levels were more rapidly decreased than Ang IV levels, suggesting longer-lasting enhancement of the action of Ang IV rather than that of Ang II after treatment with an AT1-R antagonist.

Aged↗
PubMed1998

Angiotensin II type 2 receptor is upregulated in human heart with interstitial fibrosis, and cardiac fibroblasts are the major cell type for its expression.

The expression pattern of angiotensin (Ang) II type 2 receptor (AT2-R) in the remodeling process of human left ventricles (LVs) remains poorly defined. We analyzed its expression at protein, mRNA, and cellular levels using autopsy, biopsy, or operation LV samples from patients with failing hearts caused by acute (AMI) or old (OMI) myocardial infarction and idiopathic dilated cardiomyopathy (DCM) and also examined functional biochemical responses of failing hearts to Ang II. In autopsy samples from the nonfailing heart group, the ratio of AT1-R and AT2-R was 59% and 41%, respectively. The expression of AT2-R was markedly increased in DCM hearts at protein (3.5-fold) and mRNA (3.1-fold) levels compared with AMI or OMI. AT1-R protein and mRNA levels in AMI hearts showed 1.5- and 2.1-fold increases, respectively, whereas in OMI and DCM hearts, AT1-R expression was significantly downregulated. AT1-R-mediated response in inositol phosphate production was significantly attenuated in LV homogenate from failing hearts compared with nonfailing hearts. AT2-R sites were highly localized in the interstitial region in either nonfailing or failing heart, whereas AT1-R was evenly distributed over myocardium at lower densities. Mitogen-activated protein kinase (MAPK) activation by Ang II was significantly decreased in fibroblast compartment from the failing hearts, and pretreatment with AT2-R antagonist caused an additional significant increase in Ang II-induced MAPK activity (36%). Cardiac hypertrophy suggested by atrial and brain natriuretic peptide levels was comparably increased in OMI and DCM, whereas accumulation of matrix proteins such as collagen type 1 and fibronectin was much more prominent in DCM than in OMI. These findings demonstrate that (1) AT2-R expression is upregulated in failing hearts, and fibroblasts present in the interstitial regions are the major cell type responsible for its expression, (2) AT2-R present in the fibroblasts exerts an inhibitory effect on Ang II-induced mitogen signals, and (3) AT1-R in atrial and LV tissues was downregulated during chronic heart failure, and AT1-R-mediated functional biochemical responsiveness was decreased in the failing hearts. Thus, the expression level of AT2-R is likely determined by the extent of interstitial fibrosis associated with heart failure, and the expression and function of AT1-R and AT2-R are differentially regulated in failing human hearts.

Adult↗
PubMed1998

Type I phosphatidylinositol-4-phosphate 5-kinases synthesize the novel lipids phosphatidylinositol 3,5-bisphosphate and phosphatidylinositol 5-phosphate.

Inositol phospholipids regulate a variety of cellular processes including proliferation, survival, vesicular trafficking, and cytoskeletal organization. Recently, two novel phosphoinositides, phosphatidylinositol-3,5-bisphosphate (PtdIns-3,5-P2) and phosphatidylinositol- 5-phosphate (PtdIns-5-P), have been shown to exist in cells. PtdIns-3,5-P2, which is regulated by osmotic stress, appears to be synthesized by phosphorylation of PtdIns-3-P at the D-5 position. No evidence yet exists for how PtdIns-5-P is produced in cells. Understanding the regulation of synthesis of these molecules will be important for identifying their function in cellular signaling. To determine the pathway by which PtdIns-3,5-P2 and Ptd-Ins-5-P might be synthesized, we tested the ability of the recently cloned type I PtdIns-4-P 5-kinases (PIP5Ks) alpha and beta to phosphorylate PtdIns-3-P and PtdIns at the D-5 position of the inositol ring. We found that the type I PIP5Ks phosphorylate PtdIns-3-P to form PtdIns-3,5-P2. The identity of the PtdIns-3,5-P2 product was determined by anion exchange high performance liquid chromatography analysis and periodate treatment. PtdIns-3,4-P2 and PtdIns-3,4,5-P3 were also produced from PtdIns-3-P phosphorylation by both isoforms. When expressed in mammalian cells, PIP5K Ialpha and PIP5K Ibeta differed in their ability to synthesize PtdIns-3,5-P2 relative to PtdIns-3,4-P2. We also found that the type I PIP5Ks phosphorylate PtdIns to produce PtdIns-5-P and phosphorylate PtdIns-3,4-P2 to produce PtdIns-3,4,5-P3. Our findings suggest that type I PIP5Ks synthesize the novel phospholipids PtdIns-3,5-P2 and PtdIns-5-P. The ability of PIP5Ks to produce multiple signaling molecules indicates that they may participate in a variety of cellular processes.

Animals↗
PubMed1998

Type I phosphatidylinositol-4-phosphate 5-kinases. Cloning of the third isoform and deletion/substitution analysis of members of this novel lipid kinase family.

Type I phosphatidylinositol 4-phosphate (PtdIns(4)P) 5-kinases (PIP5K) catalyze the synthesis of phosphatidylinositol 4, 5-bisphosphate, an essential lipid molecule in various cellular processes. Here, we report the cloning of the third member (PIP5Kgamma) and the characterization of members of the type I PIP5K family. Type I PIP5Kgamma has two alternative splicing forms, migrating at 87 and 90 kDa on SDS-polyacrylamide gel electrophoresis. The amino acid sequence of the central portion of this isoform shows approximately 80% identity with those of the alpha and beta isoforms. Northern blot analysis revealed that the gamma isoform is highly expressed in the brain, lung, and kidneys. Among three isoforms, the beta isoform has the greatest Vmax value for the PtdIns(4)P kinase activity and the gamma isoform is most markedly stimulated by phosphatidic acid. By analyzing deletion mutants of the three isoforms, the minimal kinase core sequence of these isoforms were determined as an approximately 380-amino acid region. In addition, carboxyl-terminal regions of the beta and gamma isoforms were found to confer the greatest Vmax value and the highest phosphatidic acid sensitivity, respectively. It was also discovered that lysine 138 in the putative ATP binding motif of the alpha isoform is essential for the PtdIns(4)P kinase activity. As was the case with the alpha isoform reported previously (Shibasaki, Y., Ishihara, H., Kizuki, N., Asano, T., Oka, Y., Yazaki, Y. (1997) J. Biol. Chem. 272, 7578-7581), overexpression of either the beta or the gamma isoform induced an increase in short actin fibers and a decrease in actin stress fibers in COS7 cells. Surprisingly, a kinase-deficient substitution mutant also induced an abnormal actin polymerization, suggesting a role of PIP5Ks via structural interactions with other molecules.

Amino Acid Sequence↗
PubMed1998

The NIK protein kinase and C17orf1 genes: chromosomal mapping, gene structures and mutational screening in frontotemporal dementia and parkinsonism linked to chromosome 17.

Full exon-intron structures are presented for the NIK serine/threonine protein kinase gene and a novel gene termed C17orf1. By in situ hybridisation and radiation hybrid mapping, a cosmid (cDD-Z) that contains regions of both of these genes has been localised between markers D17S800 and D17S791 at chromosome 17q21. The two genes are thus positional candidates for the mutant locus underlying frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), a disease for which NIK is also a good biological candidate. Using exon-intron maps, a genomic DNA sequencing based mutation screen has been performed for the NIK and C17orf1 genes in a chromosome 17-linked FTDP-17 pedigree. Two silent single-base variations were detected in C17orf1. No alterations were restricted to DNA samples from patients, thus excluding the C17orf1 and NIK genes as likely sites of mutation FTDP-17.

Carrier Proteins↗
PubMed1998

Changes in osteoblast phenotype during differentiation of enzymatically isolated rat calvaria cells.

Osteoblasts enzymatically isolated from newborn rat calvariae show various phenotypes including formation of mineralized bone nodules in culture. We investigated the temporal changes in osteoblast phenotype in these cells up to day 20 in culture. These cells formed unmineralized nodules by day 5. Mineralization was observed at the center of nodules by day 10, and nodules became larger on day 15. The nodules were surrounded by numerous alkaline phosphatase (ALP)-positive cells. ALP activity gradually increased by day 20. Parathyroid hormone (PTH) responsiveness increased with time in culture. Osteoblasts produced no osteocalcin by day 10, but its synthesis was detected from day 15. These cells expressed substantial levels of ALP and PTH/PTHrP receptor mRNAs as early as day 5 in culture, but very weak expression of osteocalcin mRNA on day 5. The levels of expression of these transcripts increased with time in culture. In situ hybridization demonstrated that PTH/PTHrP receptor and osteocalcin mRNAs were strongly expressed in nodules, but the former appeared much earlier than the latter. BMP-2 and BMP-4 mRNAs also appeared in the cells forming nodules. Immunohistochemical analysis demonstrated that cells expressing either BMP-2/4 or their receptors (BMPR-IA, BMPR-IB, and BMPR-II) preferentially appeared in nodules. These observations suggested that BMPs play an important role in the formation of mineralized bone nodules in an autocrine and/or paracrine fashion in these cells. The present study confirmed that osteoblasts enzymatically isolated from newborn rat calvariae are a useful tool for studying the differentiation process of osteoblasts.

Alkaline Phosphatase↗
PubMed1998

A long-range restriction map across 3 Mb of the chromosome 11 breakpoint region of a translocation linked to schizophrenia: localization of the breakpoint and the search for neighbouring genes.

A balanced t(1;11)(q42.1;q14.3) translocation segregates with schizophrenia and related mental illness in a single large Scottish pedigree. We have constructed a long-range restriction map covering at least 3 Mb of the chromosome 11 breakpoint region and conducted searches for genes whose expression could be altered by the translocation, resulting in schizophrenia. Novel transcribed sequences of unknown function clustered around putative CpG islands, located approximately 500 kb and 700 kb above the breakpoint, represent the only evidence to date for expressed genes within the mapped region.

Cells, Cultured↗
PubMed1998

Tissue-specific expression of human angiotensin II AT1 and AT2 receptors and cellular localization of subtype mRNAs in adult human renal cortex using in situ hybridization.

All studies analyzing the localization of angiotensin II (Ang II) receptors in the human kidney have been performed at the protein level using 125I-Ang II as a probe. In this study, cellular localizations of Ang II type l (AT1-R) and type 2 (AT2-R) receptor mRNAs in the adult human renal cortex were examined for the first time using in situ hybridization, and their expression patterns determined by RNase protection assay were compared with those in other human tissues. In the human renal cortex obtained from tumor-free portions in renal cell carcinoma, AT1-R mRNA levels were about 8- to 10-fold higher than AT2-R mRNA levels. Human liver and aorta predominantly expressed AT1-R mRNA, while human right atrium contained both AT1-R and AT2-R mRNAs. Ligand-binding assays revealed that the total Ang II receptor number in the human renal cortex was 16.0 +/- 3.3 fmol/mg protein, similar to that in liver (17.7 +/- 5. 8) but significantly higher than in right atrium (11.6 +/- 3.2) and aorta (5.6 +/- 2.7). Relative distribution ratios of AT1-R and AT2-R numbers in the renal cortex and right atrium were 82/17 and 56/42%, respectively. In situ hybridization study indicated that strongest AT1-R mRNA signals were located in interlobular arteries and tubulointerstitial fibrous regions surrounding interlobular arteries and glomeruli, followed in decreasing order by glomeruli and cortical tubules. Expression of AT2-R mRNA was highly localized in interlobular arteries. Cells present in tubulointerstitial regions were positive for vimentin and collagen type 1, indicating that the majority of the cells present in the regions are fibroblasts. Presence of strong AT1-R mRNA signals in the tubulointerstitial fibrous regions surrounding arteries and glomeruli and the expression of AT2-R mRNA in the interlobular artery were the first evidence, suggesting a pharmacological framework for the differential effects of Ang II receptor subtype mediated renal function in the adult human kidney.

Adult↗
PubMed1998

Role of calcium-sensitive tyrosine kinase Pyk2/CAKbeta/RAFTK in angiotensin II induced Ras/ERK signaling.

In cardiac fibroblasts, angiotensin II (Ang II) induced a rapid increase in extracellular signal regulated kinase (ERK) activity in a pertussis toxin insensitive manner. This ERK activation was abolished by the Gq-associated phospholipase C inhibitor U73122 but was insensitive to protein kinase C (PKC) inhibitors or PKC downregulation by phorbol ester. Intracellular Ca2+ chelation by BAPTA-AM or TMB-8 abolished Ang II induced ERK activation, whereas treatment with EGTA or nifedipine did not affect it. Ca2+ ionophore A23187 also induced a rapid increase in ERK activity to an extent similar to that of Ang II stimulation. Calmodulin inhibitors (W7 and calmidazolium) and tyrosine kinase inhibitors (genistein and ST638) completely blocked ERK activation by Ang II and A23187. Both Ang II and A23187 caused a rapid increase in the binding of GTP to p21(Ras), which was nearly abolished by genistein and calmidazolium. Transfection with the dominant negative mutant of Ras and the Ras inhibitor manumycin completely inhibited Ang II induced ERK activation. It was also found for the first time that cardiac fibroblasts abundantly expressed Ca2+-sensitive tyrosine kinase Pyk2/CAKbeta/RAFTK and that Ang II markedly induced its activation in a Ca2+/calmodulin-sensitive manner. Overexpression of the dominant negative mutant of Pyk2 significantly attenuated Ang II or A23187-induced ERK activities (36% and 38% inhibition compared with that in mock-transfected cells, respectively) and ERK tyrosine phosphorylation levels, as well as an increase in the binding of GTP to p21(Ras). These findings demonstrate that in cardiac fibroblasts, Ang II induced Ras/ERK activation is dominantly regulated by Gq-coupled Ca2+/calmodulin signaling and that Pyk2 plays an important role in the signal transmission for efficient activation of the Ang II induced Ras/ERK pathway.

Angiotensin II↗
PubMed1998

Sexual dimorphism in the tooth crown dimensions of the second deciduous and first permanent molars of Taiwan Chinese.

Sexual dimorphism in the crown components in the second deciduous molar (dm2) and the first permanent molar (M1) of the dental casts taken from Chinese living in Kaohsiung (Taiwan) was investigated. Mesiodistal and buccolingual crown diameters, and 4 main-cusp sizes in the maxillary molars and mesiodistal diameters of the trigonid and talonid in the mandibular molars were measured using a digital caliper (0.01 mm). Percentage sexual differences were calculated. With the exception of trigonid mesiodistal diameters, the mean values of males were larger than females. In both of dm2 and M1 the mean values of the trigonid mesiodistal diameters were slightly larger in females than in males, but the differences were not significant. Percentage sexual dimorphism was smaller in the mesiodistal diameters than in the buccolingual in both dm2 and M1. The crown components showed larger sexual difference in dm2 than in M1, while in the maxilla the external crown size showed larger sexual difference in M1 than in dm2. The buccal cusps showed larger sexual difference than the lingual in the maxillary molars and the talonid showed larger sexual difference than the trigonid in the mandibular. Sexual dimorphism of dm2 and M1 in their crown components displayed similar pattern, although the different degree was noted. This result is thought to relate to the fact these molars belong to the first dentition embryologically.

China↗
PubMed1997

Co-localization of glucokinase with actin filaments.

A portion of glucokinase appeared to be co-localized with actin filaments in the cytoplasm of cultured rat hepatocytes incubated with 25 mM glucose. When liver- or islet-type glucokinase was transiently expressed in COS-7 cells, the expressed glucokinase was also co-localized with actin filaments in the cytoplasm of these transfected cells. Although co-localization of glucokinase with actin filaments was not clearly demonstrated in the pancreatic beta-cell line MIN6, islet glucokinase was found to be present in both the nucleus and the cytoplasm, though predominantly in the nucleus. These findings suggest that subcellular localization of glucokinase, including co-localization with actin filaments, may have an important physiological role in metabolic regulation.

Actins↗
PubMed1997

Massive actin polymerization induced by phosphatidylinositol-4-phosphate 5-kinase in vivo.

The Rho family GTP-binding proteins have been known to mediate extracellular signals to the actin cytoskeleton. Although several Rho interacting proteins have been found, downstream signals have yet to be determined. Many actin-binding proteins are known to be regulated by phosphatidylinositol 4,5-bisphosphate in vitro. Rho has been shown to enhance the activity of phosphatidylinositol-4-phosphate 5-kinase (PI4P5K), the phosphatidylinositol 4,5-bisphosphate synthesizing enzyme. Recently we isolated several isoforms of type I PI4P5K. Here we report that PI4P5K Ialpha induces massive actin polymerization resembling "pine needles" in COS-7 cells in vivo. When truncated from the C terminus to amino acid 308 of PI4P5K Ialpha, both kinase activity and actin polymerizing activity were lost. Although the dominant negative form of Rho, RhoN19, alone decreased actin fibers, those induced by PI4P5K were not affected by the coexpression of RhoN19. These results suggest that PI4P5K is located downstream from Rho and mediates signals for actin polymerization through its phosphatidylinositol-4-phosphate 5-kinase activity.

Actins↗