Search PubMed⌕ Search

Biomedical subjects

Y Yazaki

Publications and source records attributed to Y Yazaki.

At least 739 records · Page 41Linked to original sources
PubMed1990

Abnormal calcium handling in vascular smooth muscle cells of spontaneously hypertensive rats.

We have developed a system for measuring the dynamic changes in the cytoplasmic free calcium concentration [( Ca2+]i) in single vascular smooth muscle cells (VSMC) that is highly sensitive and does not cause cellular damage. Marked increases in [Ca2+]i in response to stimulation with caffeine and angiotensin II occurred in some VSMC of 4-week-old spontaneously hypertensive rats (SHR), in which the blood pressure and basal [Ca2+]i levels are not yet elevated. In 8-week-old rats, the basal [Ca2+]i level in VSMC was higher in SHR than in Wistar-Kyoto rats. Although the effects of high blood pressure on [Ca2+]i in vivo were expected to disappear during the passage culture, the [Ca2+]i in the fifth-passage cells was similar to that in the primary cells. These results suggest that the maintenance of high [Ca2+]i levels in VSMC of SHR is genetically regulated and is one of the mechanisms of hypertension in this strain, and that abnormal calcium regulation in VSMC of SHR is expressed even before overt hypertension.

Angiotensin II↗
PubMed1990

Cytoplasmic calcium ion elevating factor(s) in spontaneously hypertensive rat serum.

We have attempted to characterize the as yet unspecified circulating factor(s) in spontaneously hypertensive rat (SHR) serum that elevate(s) the cytoplasmic calcium ion concentration in vascular smooth muscle cells (VSMC). We measured the cytoplasmic calcium ion concentration in cultured VSMC before and after incubation with serum from SHR or Wistar-Kyoto rats (WKY). Incubation with serum from overtly hypertensive 8-week-old SHR, but not with serum from 8-week-old WKY, significantly elevated the cytoplasmic calcium ion concentration in VSMC from 8-week-old WKY and 4-week-old SHR in a dose- and an incubation period-dependent manner, although no significant elevation occurred in VSMC from 4-week-old WKY. Neither the heat-immobilized nor the trypsinized 8-week-old SHR serum elevated the cytoplasmic calcium ion concentration. Ultrafiltration procedures indicated that the molecular weight of the factor should be 10,000-30,000 daltons. Incubation with serum from 4-week-old SHR or WKY did not elevate the cytoplasmic calcium ion concentration. These results strongly suggest that: (1) a cytoplasmic calcium ion concentration elevating factor exists in serum from 8-week-old SHR but not from 4-week-old SHR, or 4- or 8-week-old WKY; (2) this factor should be of a protein nature, with a molecular weight of 10,000-30,000 daltons; (3) responsiveness to the factor appears in VSMC at a younger age in SHR than in WKY; (4) the factor elevates the cytoplasmic calcium ion concentration to the level determined a priori not by the strain but by the age of the rats from which the VSMC originate; and (5) the a priori determined level increases with the age of the rats.

Animals↗
PubMed1990

Molecular cloning of gene sequences from rat heart rapidly responsive to pressure overload.

Although pressure overload induces cardiac hypertrophy and reexpression of contractile protein isogenes, the molecular mechanism of both is not well understood. We demonstrated the early change in the translational activity of specific cardiac messenger RNA by two-dimensional gel electrophoresis of in vitro translational products. A total of over 400 translational products were detected by fluorography, and the relative predominance of eight species was increased by pressure overload whereas that of two translational products was decreased. We cloned four pressure-overload-responsive complementary DNA clones, pPO-1, -4, -5, and -6, by differential dot blot hybridization. Two clones were increased from the early period after the imposition of pressure overload; the other two were decreased. The expression pattern of each complementary DNA clone in the pressure-overloaded hearts was similar to that in fetal hearts. Pressure overload also induced the additional messenger RNA, which hybridized with pPO-4. This mRNA was also recognized in fetal, neonatal, and adult spontaneously hypertensive rat hearts. The induction of this transcript by pressure overload was not suppressed but, rather, stimulated by cycloheximide. These results suggest that there are some genes that rapidly respond to pressure overload and that may play some role in the development of cardiac hypertrophy.

Acute Disease↗
PubMed1990

Messenger RNA levels of guanine nucleotide-binding proteins are reduced in the ventricle of cardiomyopathic hamsters.

The expression of guanine nucleotide-binding protein (G-protein) genes (Gs alpha, Go alpha, Gi alpha 1, Gi alpha 2, and Gi alpha 3) was examined in the ventricle of cardiomyopathic Syrian hamsters of the Bio14.6 strain (10-35 weeks old). Northern blot analysis of total cellular RNA revealed that all G-protein genes except Gi alpha 1 were expressed in the ventricle of Syrian hamsters. Gs alpha and Gi alpha 2 genes were abundantly expressed. The expression levels of the Gs alpha and Gi alpha 2 messenger RNAs in Bio14.6 ventricles were lower than the levels in ventricles of the F1B hamster strain; the abundance of Go alpha and Gi alpha 3 messenger RNAs did not change markedly. Moreover, the messenger RNA levels of Gs alpha and Gi alpha 2 decreased as the stage of cardiomyopathy progressed. Since G-proteins are linked to adenylate cyclase, these alterations of G-protein messenger RNA levels may be related to reduced contractility of cardiomyopathic heart.

Animals↗
PubMed1990

Expression of major histocompatibility complex class I antigen in murine ventricular myocytes infected with Coxsackievirus B3.

Evidence has accumulated that T cell-mediated autoimmunity plays an important role in the pathogenesis of viral myocarditis. T lymphocytes are known to recognize antigen-presenting cells, such as virus-infected cells, being restricted by syngeneic major histocompatibility complex (MHC) antigens. To clarify in more detail the immunological mechanisms involved, we induced acute viral myocarditis in C3H/He mouse ventricles with coxsackievirus B3 (CVB3) and examined, by immunofluorescence, the expression of MHC class I and II antigens, previously reported not to be expressed by normal cardiac myocytes. Furthermore, to confirm the expression of MHC class I (H-2Kk) antigens at the cellular level, we treated cultured cardiac myocytes with interferon gamma and examined the antigen expression by immunofluorescence and Northern blot hybridization, using an antisense RNA probe for MHC messenger RNA. Our observations demonstrated 1) CVB3-induced myocarditis resulted in the enhanced expression of MHC class I (H-2Kk) gene product on the surface of cardiac myocytes but low or undetectable levels of MHC class II or H-2Dk gene products, and moderate focal transient (days 5-7) expression of both MHC class I (Kk + Dk) region gene products and MHC class II antigens were induced on capillary endothelial cells; 2) murine fetal cardiac myocytes cultured in vitro in the presence of interferon gamma similarly were shown to express marked levels of MHC class I (H-2Kk) but low to undetectable levels of the H-2Dk gene product; however, weak to moderate MHC Class II antigens were expressed by these cultured myocytes; and 3) the expression of MHC antigens in cardiac myocytes was modulated at the transcriptional level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The myosin gene switching in human cardiac hypertrophy.

Cardiac hypertrophy is associated with qualitative as well as quantitative changes in myocardial cells. To analyze the molecular basis of isozymic transitions of cardiac myosins in response to pressure overload, we have constructed and characterized two types of myosin heavy chain (MHC) cDNA clones, specifying alpha- and beta-MHCs, and two types of myosin alkali light chain cDNA clones, complementary to atrial type (ALC1) and ventricular type (VLC1) mRNAs from a human fetal heart cDNA library. Using the S1 nuclease mapping procedure, we showed that the MCH isozymic transitions from alpha- to beta-MHC in the pressure overloaded atria are produced by changes in the relative level of alpha- and beta-MHC gene expression. In addition, we observed that the expression of VLC1 gene is also induced in the atria subjected to severe pressure overload. Thus, it appears that the increased expression of VLC1 gene, together with the isogene switch from alpha- to beta-MHC gene, may participate in the adaptation of myocardium to new functional requirement. Then, to get a better understanding of the genetic mechanisms involved in the regulation of isogene expression, we have isolated and sequenced genomic clone for VLC1 isoform. Sequence analysis has identified multiple potential cis regulatory elements within a 686-bp upstream region. This region includes 28-bp alternating purine/pyrimidine sequences and two segment exhibiting homology to consensus sequence proposed for viral and cellular enhancer elements. In particular, a comparison of the VLC1 upstream gene sequence with those available for several muscle-specific genes revealed that CC(A + T-rich)6GG elements and CATTCCT sequence are conserved. These results suggested that CArG box (-96 to -87) has an important role in the positive regulation of the VLC1 gene and this element may be involved in the co-regulation of VLC1 and cardiac alpha-actin genes.

Adaptation, Physiological↗
PubMed1990

Molecular mechanism of cardiac hypertrophy.

Pressure overload induces cardiac hypertrophy and reexpression of contractile protein isogenes. To ascertain the molecular mechanism of these events, we examined the expression of cellular oncogenes and the early change in the translational activity of specific cardiac mRNA by two-dimensional gel electrophoresis of in vitro translational products. Pressure overload increased the expression levels of c-fos, c-myc, and c-Ha-ras genes. The relative predominance of 8 species out of over 400 translational products was increased by pressure overload while that of 2 translational products was decreased. We cloned four pressure-overload-responsive cDNA clones by differential dot blot hybridization. The expression pattern of each cDNA clone in the pressure-overloaded hearts was similar to that in fetal hearts. To examine whether mechanical stimuli directly induce specific gene expression in the heart, we cultured rat neonatal cardiocytes in elastic silicone dishes and stretched these adherent cells. Myocytes stretching stimulated amino acid uptake and expression of the c-fos gene, which was blocked by protein kinase C inhibitors. These results suggest that there are some early responsive genes in cardiac hypertrophy and that mechanical loading directly stimulates gene expression possibly via protein kinase C activation.

Amino Acids↗
PubMed1990

[Reduction of myocardial infarct size by early intracoronary thrombolysis as assessed by serum cardiac myosin light chains and left ventricular function].

Cardiac myosin light chains are released from the infarcted myocardium soon after the onset of infarction, and the level of myosin light chains in the serum reflects infarct size, regardless of the presence of early coronary reperfusion. In this study, we used serum myosin light chains and assessed changes in left ventricular function to evaluate the effects of intracoronary thrombolysis on infarct size, with special reference to the interval between the onset of infarction and the time of reperfusion. Forty patients with acute myocardial infarction who underwent coronary angiography and intracoronary thrombolysis for the left anterior descending artery (LAD) early after the onset of infarction were categorized in four groups: in group A (n = 9) the LAD was already patent at the start of intracoronary thrombolysis, in group B (n = 12) antegrade flow in the LAD was achieved within three hours of the onset of symptoms, in group C (n = 10) antegrade flow was achieved later than three hours after the onset of symptoms, and in group D (n = 9) antegrade flow in the LAD was not achieved. The peak appearance time of creatine phosphokinase (CPK) in group D was significantly later than in the other groups. The total release of CPK in group C (3,119 +/- 414 IU/l) was greater than that in group A (1,332 +/- 346 IU/l) (p less than 0.01), but the total CPK release in group D (2,525 +/- 525 IU/l) was not statistically different from those of any other group. In all four groups myosin light chain I appeared in the serum from the first day on and reached their peak values between the third and fifth days. The peak values of myosin light chain I were 14.7 +/- 2.1 ng/ml for group A, 16.3 +/- 2.3 ng/ml for group B, 24.6 +/- 2.4 ng/ml for group C, and 25.1 +/- 1.8 ng/ml for group D. The peak myosin light chain levels in groups A and B were less than those in groups C and D. Twenty-nine of the 40 patients had no previous episodes of infarction, and these 29 patients were classified in two groups according to the Forrester's subset class on the first day: four of seven patients in group D were in subsets II, III or IV; whereas, the majority of patients in groups A, B and C were in subset I.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Vessels↗
PubMed1989

Developmentally regulated expression of vascular smooth muscle myosin heavy chain isoforms.

Two types of smooth muscle myosin heavy chain (MHC) isoforms, SM1 and SM2, were recently identified to have different carboxyl termini (Nagai, R., Kuro-o, M., Babij, P., and Periasamy, M. (1989) J. Biol. Chem. 264, 9734-9737). SM1 and SM2 are considered to be generated from a single gene through alternative RNA splicing. In this study we investigated expression of vascular MHC isoforms during development in rabbits at the mRNA, protein, and histological levels. In adults, all smooth muscle cells reacted with both anti-SM1 and anti-SM2 antibodies on immunofluorescence, suggesting the coexpression of SM1 and SM2 in a single cell. In fetal and perinatal rabbits, however, only anti-SM1 antibody consistently reacted with smooth muscles. Reactivity with anti-SM2 antibody was negative in the fetal and neonatal blood vessels and gradually increased during 30 days after birth. These developmental changes in SM1 and SM2 expression at the histological level coincided with mRNA expression of each MHC isoform as determined by S1 nuclease mapping, indicating that expression of SM1 and SM2 is controlled at the level of RNA splicing. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of myosin from fetal and perinatal aortas revealed the presence of large amount of SM2. Interestingly, fetal SM2 did not cross-react with our anti-SM2 antibody on immunoblotting. We conclude that expression of SM1 and SM2 are differentially regulated during development and that a third type of MHC isoform may exist in embryonic and perinatal vascular smooth muscles.

Animals↗
PubMed1989

Hemodynamic shear stress stimulates endothelin production by cultured endothelial cells.

We have examined the effect of shear stress on the production of endothelin by cultured porcine endothelial cells. Low shear stress stimulated the expression of endothelin mRNA in polygonal endothelial cells with a peak time of 2 to 4 hours and also increased the release of immunoreactive endothelin into the culture medium. The expression of endothelin mRNA in the ellipsoidal endothelial cells under higher shear stress was not different from that of the control level. Our results suggest a possible role for hemodynamic shear stress in the regulation of endothelin production in vascular endothelial cells.

Animals↗
PubMed1989

Transforming growth factor-beta stimulates the expression of endothelin mRNA by vascular endothelial cells.

Endothelin is a potent vasoconstrictor peptide produced by vascular endothelial cells. Incubation of the serum-deprived confluent porcine aortic endothelial cells with 10-300 pM TGF-beta 1, resulted in a several fold increase in endothelin mRNA levels with a peak time of 2 h. An enzyme-linked immunosorbent assay revealed that the levels of endothelin in endothelial cell conditioned media was also increased by TGF-beta 1. These results suggest that TGF-beta 1, secreted by activated platelets, is involved not only in wound healing, but in the regulation of local vascular tone by stimulating endothelin production in the endothelial cells.

Animals↗
PubMed1989

Molecular adaptation to pressure overload in human and rat hearts.

The process of enlargement of the heart due to overload involves a significant reconstitution of the organ including myocytes and intracellular constituents. We demonstrated the distribution of two types of cardiac myosin heavy chains (HC alpha and HC beta) in the human heart using monoclonal antibodies. The ventricle comprised mainly HC beta which has low ATPase activity, whereas the atrium was predominantly composed of HC alpha which has high ATPase activity. We also demonstrated isozymic transition of HC alpha to HC beta in the human atrium and ventricle by hemodynamic overload, regarded as a compensatory mechanism to meet an increased demand in work. To examine the molecular mechanism for the expression of these HCs, we have isolated human HC alpha and HC beta cDNA clones from a fetal heart cDNA library. Comparison of the nucleotide and amino acid sequences deduced from the DNA between these cDNA clones showed 91 and 96% homology, respectively. Using HC alpha and HC beta gene-specific sequences, we demonstrated that the transition of HC alpha to HC beta in the overloaded human heart was induced by the expression of HC beta-gene. To determine the role of cellular oncogenes in the process of cardiac growth and hypertrophy, we examined the expression pattern of eight cellular oncogenes during the developmental stage and pressure-overloaded hypertrophy of the rat heart by Northern blot analysis. c-fos, c-myc and c-Ha-ras were expressed in the heart in response to pressure overload and in a stage-specific manner, suggesting that these cellular oncogenes participate in the normal developmental process and hypertrophy of the heart. We also cloned the genes of which expression level was rapidly changed by pressure overload by differential hybridization technique. Our results suggest that clone 4 may be involved in the molecular mechanism for the development of cardiac hypertrophy due to overload.

Adaptation, Physiological↗
PubMed1989

Effect of long-term treatment with beta-blocker on cardiac hypertrophy in SHR.

Recent studies suggest that beta-blocker treatment may attenuate cardiac hypertrophy induced by pressure overload in the spontaneously hypertensive rat (SHR), but the effect of this therapy on the reconstitution of the intracellular constituents in the heart that occurs during the development of cardiac hypertrophy has not been examined. In this study, we investigated the effect of chronic administration of carteolol (4 mg/kg/day p.o.) or propranolol (20 mg/kg/day p.o.), beta-blockers with distinct modes of action, on the composition of cardiac myosin isozymes and histological findings as well as heart weight. Therapeutic periods were 4, 12 or 30 weeks. Though blood pressure was not significantly reduced, the development of cardiac hypertrophy was suppressed as evidenced by left ventricular weight in both groups of carteolol- and propranolol-treated SHR for all therapeutic periods. Again, beta-blocker treatment for 12 weeks alleviated myocardial degeneration and reactive fibrosis which were observed in all cases of age-matched untreated SHR. However the extent of the transition of cardiac myosin isozymes from V1 to V2 or V3 were essentially the same among all groups including untreated SHR. These results indicate that chronic administration of beta-blockers attenuates the development of cardiac hypertrophy and degeneration without affecting the transition of myosin isozymes which is thought to be a kind of biochemical adaptation of the myocardium to overload.

Adrenergic beta-Antagonists↗