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Biomedical subjects

S Hayashi

Publications and source records attributed to S Hayashi.

At least 235 records · Page 13Linked to original sources
PubMed2000

Cyclic AMP inhibited proliferation of human aortic vascular smooth muscle cells, accompanied by induction of p53 and p21.

Although cAMP is an important second messenger that plays a pivotal role in the regulation of platelet aggregation and dilatation of blood vessels, little is known about the action of cAMP on the growth of vascular smooth muscle cells (VSMCs). Thus, we initially studied the effects of cAMP accumulation by using various cAMP stimulants, including a phosphodiesterase type 3 inhibitor (cilostazol) on human aortic VSMC growth. Accumulation of cAMP inhibited the platelet-derived growth factor (PDGF)-stimulated VSMC growth in a dose-dependent manner (P<0.01), whereas PDGF significantly stimulated the growth of human VSMCs. Thus, we focused on the role of cell cycle regulatory genes, especially on a negative regulator, an anti-oncogene, p53. The protein of p53 was potentiated by cilostazol as well as forskolin and 8-bromo-cAMP, whereas PDGF decreased p53 expression. Upregulation of p53 protein by cAMP was further confirmed by the observation that the decrease in p21, a p53-inducible protein, by PDGF was significantly attenuated by cilostazol in a dose-dependent manner (P<0.01). These results revealed that accumulation of cAMP inhibited VSMC proliferation, which was at least in part due to an increase in p53-p21 expression. Because p53 and p21 have been reported to induce apoptosis, we examined apoptotic cells for cAMP accumulation. Incubation of VSMCs with cilostazol resulted in a significant increase in apoptotic cells in a dose-dependent manner compared with vehicle treatment as assessed by nuclear chromatic morphology (P<0.01); forskolin also stimulated apoptotic cells. Consistent with nuclear staining, DNA fragmentation in VSMCs treated with forskolin as well as 8-bromo-cAMP and cilostazol was significantly increased compared with DNA fragmentation in VSMCs treated with vehicle, whereas PDGF significantly decreased the rate of DNA fragmentation (P<0.01). Overall, these results demonstrated that cAMP inhibited the proliferation of human aortic VSMCs, accompanied by p53-p21-mediated apoptosis. Analogues of cAMP that have direct inhibitory effects on VSMC proliferation can be considered as potential antiproliferative drugs against VSMC growth.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

EGF receptor attenuates Dpp signaling and helps to distinguish the wing and leg cell fates in Drosophila.

Wing and leg precursors of Drosophila are recruited from a common pool of ectodermal cells expressing the homeobox gene Dll. Induction by Dpp promotes this cell fate decision toward the wing and proximal leg. We report here that the receptor tyrosine kinase EGFR antagonizes the wing-promoting function of Dpp and allows recruitment of leg precursor cells from uncommitted ectodermal cells. By monitoring the spatial distribution of cells responding to Dpp and EGFR, we show that nuclear transduction of the two signals peaks at different position along the dorsoventral axis when the fates of wing and leg discs are specified and that the balance of the two signals assessed within the nucleus determines the number of cells recruited to the wing. Differential activation of the two signals and the cross talk between them critically affect this cell fate choice.

Animals↗
PubMed2000

Control of tracheal tubulogenesis by Wingless signaling.

The tubular epithelium of the Drosophila tracheal system forms a network with a stereotyped pattern consisting of cells and branches with distinct identity. The tracheal primordium undergoes primary branching induced by the FGF homolog Branchless, differentiates cells with specialized functions such as fusion cells, which perform target recognition and adhesion during branch fusion, and extends branches toward specific targets. Specification of a unique identity for each primary branch is essential for directed migration, as a defect in either the EGFR or the Dpp pathway leads to a loss of branch identity and the misguidance of tracheal cell migration. Here, we investigate the role of Wingless signaling in the specification of cell and branch identity in the tracheal system. Wingless and its intracellular signal transducer, Armadillo, have multiple functions, including specifying the dorsal trunk through activation of Spalt expression and inducing differentiation of fusion cells in all fusion branches. Moreover, we show that Wingless signaling regulates Notch signaling by stimulating delta expression at the tip of primary branches. These activities of Wingless signaling together specify the shape of the dorsal trunk and other fusion branches.

Animals↗
PubMed2000

Role of conserved histidine residues in D-aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6.

D-Aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6 (Alcaligenes A-6) was strongly inactivated by diethylpyrocarbonate (DEPC). An H67N mutant was barely active, with a kcat/Km 6.3 x 10(4) times lower than that of the recombinant wild-type enzyme, while the H67I mutant lost detectable activity. The H67N mutant had almost constant Km, but greatly decreased kcat. These results suggested that His67 is essential to the catalytic event. Both H69N and H69I mutants were overproduced in the insoluble fraction. The kcat/Km of H250N mutant was reduced by a factor of 2.5 x 10(4)-fold as compared with the wild-type enzyme. No significant difference between H251N mutant and wild-type enzymes in the Km and kcat was found. The Zn content of H250N mutant was nearly half of that of wild-type enzyme. These results suggest that the His250 residue might be essential to catalysis via Zn binding.

Alcaligenes↗
PubMed2000

Evolution of urate-degrading enzymes in animal peroxisomes.

The end product of purine metabolism varies from species to species. The degradation of purines to urate is common to all animal species, but the degradation of urate is much less complete in higher animals. The comparison of subcellular distribution, intraperoxisomal localization forms, molecular structures, and some other properties of urate-degrading enzymes (urate oxidase, allantoinase, and allantoicase) among animals is described. Liver urate oxidase (uricase) is located in the peroxisomes in all animals with urate oxidase. On the basis of the comparison of intraperoxisomal localization forms, mol wt, and solubility of liver urate oxidase among animals, it is suggested that amphibian urate oxidase is a transition form in the evolution of aquatic animals to land animals. Allantoinase and allantoicase are different proteins in fish liver, but the two enzymes form a complex in amphibian liver. The subcellular localization of allantoinase and allantoicase varies among fishes. Hepatic allantoinase is located both in the peroxisomes and in the cytosol in saltwater fishes, and only in the cytosol in freshwater fishes. Hepatic allantoicase is located on the outer surface of the peroxisomal membrane in the mackerel group and in the peroxisomal matrix in the sardine group. Amphibian hepatic allantoinase-allantoicase complex is probably located in the mitochondria. On the basis of previous data, changes of allantoinase and allantoicase in molecular structure and intracellular localization during animal evolution may be as follows: Fish liver allantoinase is a single peptide with a mol wt of 54,000, and is located both in the peroxisomes and in the cytosol, or only in the cytosol. Fish liver allantoicase consists of two identical subunits with a mol wt of 48,000, and is located in the peroxisomal matrix or on the outer surface of the peroxisomal membrane. The evolution of fishes to amphibia resulted in the dissociation of allantoicase into subunits, and in the association of allantoinase with the subunit of allantoicase. This amphibian enzyme was lost by further evolution.

Amidohydrolases↗
PubMed2000

Transient left ventricular aneurysm and hypertrophy accompanied by polymorphic ventricular tachycardia in a patient suspected of acute myocarditis.

A 75-year-old woman presented with recurrent ventricular tachycardia (VT) compatible with torsades de pointes (TdP) based on sinus bradycardia and QT prolongation. Previously she had received pirmenol, at a serum concentration within therapeutic range, for her paroxysmal atrial fibrillation. Emergent cardiac catheterization identified a ventricular aneurysm of the anteroapical and inferior wall along with angiographically normal coronary arteries. A right ventricular endomyocardial biopsy revealed postmyocarditic change. The left ventricular contraction improved after 5 weeks of conservative treatment. A follow-up echocardiogram revealed transient thickening of partial left ventricular wall consistent with the segment of the aneurysm. Several months later, almost all abnormal findings had improved except for sustained deep negative T waves in precordial leads. Acute myocarditis was primarily suspected as the cause of her clinical presentation.

Acute Disease↗
PubMed2000

Successful resection of intracardiac invasive thymoma with right ventricular inflow tract occlusion.

A 72-year-old man presenting with the superior vena cava syndrome and intracardiac mass was admitted to our hospital. The mass was resected and confirmed to be invasive thymoma. Three years later, he was re-admitted with recurrence into the intracardiac space without any changes in the anterior mediastinum mass. The mass occupied the right atrial cavity and protruded into the right ventricle, causing right ventricular inflow tract obstruction. He underwent re-operation and irradiation. His postoperative course was uneventful, and he has remained alive. Invasive thymoma with intracardiac extension is extremely rare.

Aged↗
PubMed2000

Malignant insulinoma which expressed a unique creatine kinase isoenzyme: clinical value of arterial embolization as a palliative therapy.

A 76-year-old man with hypoglycemic coma was diagnosed as malignant insulinoma with multiple hepatic metastases. Embolization was done for two-thirds of the hepatic mass and it rapidly lowered the serum immunoreactive insulin. He was discharged without medication and has been free from hypoglycemia. After the embolization, the serum creatine kinase (CK) level increased transiently although there was no evidence of myocardial infarction. On electrophoresis, the CK activity showed an abnormal peak, suggesting mitochondrial CK. CK release after embolization has been reported in only a few cases with endocrine tumors, which might indicate some relationship between active energy metabolism and mitochondrial CK.

Aged↗
PubMed2000

Current practice of management of bacteremic sepsis: a study in a tertiary care teaching hospital in Japan.

OBJECTIVE: To investigate how patients with bacteremic sepsis are managed in a tertiary care teaching hospital. PATIENTS AND METHODS: Prospective observational study on patients with bacteremic sepsis. Clinical and microbiological characteristics of bacteremic sepsis were analyzed in relation to prognosis. Severity of the illness was quantitatively analyzed by the APACHE (Acute Physiology, Age, Chronic Health Evaluation) III scoring system. Also investigated was how closely physicians paid attention to acute physiological alterations in patients. RESULTS: The 28-day mortalities in fifty hemodynamically stable patients and in twenty-three septic shock patients were 26% and 52%, respectively (p=0.028). Gram-positive organisms accounted for 54% of all organisms, with the mortality and incidence of septic shock being the same as with Gram-negative infections. The mean APACHE III score was 42.9 in survivors, and 76.5 in non-survivors (p < 0.001). Although serum levels of C-reactive protein and acute physiology score (APS) was significantly higher in non-survivors than in survivors, the correlation with APACHE III score was more prominent in APS. The number of vital signs recorded was 1.67 in physicians and 3.6 in nurses (p < 0.001). CONCLUSIONS: The present study proved that the APACHE III score accurately discriminates between survivors and non-survivors of patients with sepsis. By addressing the need for an objective evaluation of severity of illness, it strongly recommends that physicians should be made aware of physiologically defined sepsis and that they should pay closer attention to patients' physiological alterations to identify the development of sepsis in critically ill patients.

APACHE↗
PubMed2000

Effects of LTB4 receptor antagonist on myonephropathic metabolic syndrome: an experimental study.

The aims of this study were to determine the involvement of leukocytes in reperfusion injury following acute arterial occlusion and to evaluate the effect of the leukotriene B4 (LTB4), which is a chemical mediator of inflammation, receptor antagonist. We examined the usefulness of LTB4 receptor antagonist, ONO-4057, as a preventative drug for myonephropathic metabolic syndrome (MNMS). The experimental leg ischemic model was developed using Wistar strain rats. The rats were divided into 4 groups. In Group R3, the infra-renal abdominal aorta was clamped for 3 hrs and the right femoral muscle tissue was cut to block the development of a collateral artery. In Group R6, the infra-renal abdominal aorta was clamped for 6 hrs and the right femoral muscle tissue was cut. In Group C, the controls, there was no clamping of the abdominal aorta and the right femoral muscle tissue was cut. In Group M, the medicated group, rats were pretreated with an LTB4 receptor antagonist, ONO-4057, just before reperfusion. Blood serum interleukin-1 (IL-1), interleukin-8 (IL-8), creatine phosphokinase (CPK), and aldolase were measured and compared in each of those 4 groups. We also examined the intercellular adhesion molecule-1 (ICAM-1) expression in various organs (liver, heart and kidney) by immunohistochemistry. We found that IL-1 beta levels were low in all groups. CPK, aldolase and IL-8 levels after reperfusion in Group R6 significantly high compared with the levels in Group C (P < 0.03 about CPK, P < 0.05 about aldolase, and P < 0.05 about IL-8). The levels of CPK, aldolase, and IL-8 in Group M were significantly lower than those in Group R6 (P < 0.02 about CPK, P < 0.04 about aldolase, and P < 0.03 about IL-8). We determined immunohistochemically that the expression of ICAM-1 was positive on endothelial cells at the coronary artery and the small vein in Group R6 and that the expression of ICAM-1 was negative on endothelial cells in Group C. Those data suggested that ICAM-1 may play an important role in the progression of reperfusion injury, and the adhesion of neutrophilic leukocytes on endothelial cells may play a significant role in MNMS. LTB4 receptor antagonist may be useful for preventing reperfusion injury following acute aortic occlusion.

Acidosis↗
PubMed2000

A new type of matrix vesicles is found in fetal bovine tracheal cartilage.

Using 4-month-old fetal bovine tissue, the properties of the tibia epiphyseal cartilage matrix vesicles, a type of endochondral ossification tissue, were compared with those from tracheal cartilage. The matrix vesicle fractions, obtained by collagenase digestion and differential centrifugation, were subjected to sucrose-density-gradient centrifugation. Alkaline phosphatase activity, protease activity, and lacatate dehydrogenase activity were assayed for the marker enzyme of the matrix vesicles. Matrix vesicles containing alkaline phosphatase, metalloprotease, and lacatate dehydrogenase were found in the tibia epiphyseal cartilage at a density of 1.11 g/ml. In surprising contrast, we also found matrix vesicle-like vesicles with a high density of 1.24 g/ml in the tracheal cartilage. These also contained alkaline phosphatase and lactate dehydrogenase, but not metalloprotease. The electrophoretic profiles of the lactate dehydrogenase isoenzymes from the matrix vesicle and matrix vesicle-like vesicles were identical with those of chondrocyte cytosolic lactate dehydrogenase. Aldolase, aspartate: 2-oxoglutarate aminotransferase, alanine: 2-oxoglutarate aminotransferase, glucose-6-phosphatase, glutamate dehydrogenase, catalase, and cytosolic enzymes except for lactate dehydrogenase were not detected in these vesicles. These results suggest the presence of a mechanism for specific uptake of cytosolic lactate dehydrogenase in both vesicles. In this study, a new type of matrix vesicles without protease was found in the tracheal cartilage, a kind of permanent cartilage, but not in the tibia epiphyseal cartilage, which is replaced by bone tissue.

Alkaline Phosphatase↗
PubMed2000

Telomere dynamics and genetic instability in disease progression of chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is characterized by a Philadelphia (Ph) translocation creating a novel BCR-ABL oncoprotein, and CML patients have a chronic phase for several years followed by an intractable blast cell proliferation, called blast transformation. In the blast phase, more than 60% of patients show additional cytogenetic changes, e. g., double Ph, +8, i(17q). In this review, we would like to address genetic changes, including genome instability, cytogenetic changes, and telomere dynamics that relate to karyotypic instability. In the chronic phase, approximately 60% of CML patients show reduced telomere length without highly elevated telomerase activity or microsatellite alterations, indicating that telomere reduction may be linked to cell replication. Therefore, the Ph translocation might be a first event to immortalize cell proliferation. In the blast phase, 50% of CML patients have high levels of elevated telomerase activity and the same number of patients had microsatellite changes. Of note is that most patients with telomerase up-regulation in the blast phase had additional cytogenetic changes and >60% of them showed microsatellite changes at least at one locus. In contrast, most patients without telomerase activity did not show microsatellite changes. These findings may indicate that telomerase up-regulation in the blast phase of CML patients is closely associated with microsatellite changes (representative of genome instability), while blast cells in the remaining patients (30%) maintain their proliferative capability without microsatellite changes and telomerase up-regulation. This further suggests that there is also an unknown mechanism for genome stability without the process of telomerase up-regulation in some patients with CML in blast crisis.

Cell Transformation, Neoplastic↗
PubMed2000

The CD9 molecule on stromal cells.

Numerous functions have been attributed to CD9 and other members of the transmembrane 4 (TM4) superfamily. CD9 is thought to be involved in cell proliferation, differentiation, motility and survival. It may also function as part of toxin and virus receptor complexes. Although much remains to be learned about molecular mechanisms, the molecule associates with several integrins, small G proteins, MHC class II molecules and other TM4 superfamily proteins on a given cell surface membrane. Here, we briefly discuss the CD9 displayed on stromal cells that support hematopoiesis and the potential importance of this molecule to osteoclast differentiation.

Amino Acid Sequence↗
PubMed2000

[Regulation of ER(estrogen receptor) gene expression in the genesis and development of breast cancer].

We studied the regulation of ER alpha gene expression in terms of transcriptional regulation and DNA-methylation in human breast cancer. In cancer, levels of ER alpha mRNA transcribed from a distal promoter (promoter B) remarkably correlated to the protein levels. The binding protein(ERBF-1) of an important cis-element, which we identified, was exclusively expressed in the cells expressing ER alpha, indicating its important role in the enhanced expression of ER alpha in breast cancer. Furthermore, loss of ER alpha expression is the most important event in development of breast cancer. We found that methylation of two promoters of ER alpha was inversely associated with the gene expression in human breast cancer. Specifically, methylation of promoter B suppressed ER alpha expression, and demethylating treatment recovered it. Both methylation of ER alpha gene and modification of transcription by certain trans-acting factors are important for the regulation of ER alpha expression during breast carcinogenesis.

Breast Neoplasms↗
PubMed2000

[A case of isolated fourth ventricle in the early postoperative period of subarachnoid hemorrhage].

An adult case of isolated fourth ventricle which developed in the early postoperative period of SAH is reported. A 72-year-old male with Hunt & Kosnik Grade 4 subarachnoid hemorrhage (SAH) underwent emergent neck-clipping of an anterior communicating artery aneurysm along with setting of external ventricular drainage (EVD) and cisternal drainage (CD). The lamina terminalis (LT) was opened. Preoperative study had showed diffuse SAH with intraventricular hemorrhage (IVH), and mild dilatation of the whole ventricular system on CT scan (Fisher Group 4). Twelve hours after surgery, both of the drainages were opened with the pressure setting of 20 cm H2O for EVD and 10 cm H2O for CD. Although his neurological state had been improving, 2 hours after the opening of the drainages he suddenly fell into respiratory arrest and coma, when 20 ml of CFS through CD was drained. On CT scan, isolated fourth ventricle was recognized. The patient died on the ninth postoperative day. In case of severe SAH with diffuse IVH, we should be careful when setting the pressure of EVD or CD with the LT opened, because of the possibility of occlusion of the fourth ventricle outlet and aqueduct, that results in fourth ventricle isolation.

Aged↗