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M Shibuya

Publications and source records attributed to M Shibuya.

At least 163 records · Page 9Linked to original sources
PubMed1998

The mechanisms of hepatic sinusoidal endothelial cell regeneration: a possible communication system associated with vascular endothelial growth factor in liver cells.

Vascular endothelial growth factor (VEGF) has been shown to induce proliferation of sinusoidal endothelial cells in primary culture. To elucidate the mechanisms of sinusoidal endothelial cell regeneration in vivo, mRNA expression of VEGF and its receptors, flt-1 and KDR/flk-1, were studied in rat livers. Northern blot analysis revealed that VEGF-mRNA was expressed in hepatocytes immediately after isolation from normal rats. In contrast, non-parenchymal cells, including sinusoidal endothelial cells, expressed VEGF receptor-mRNA. Vascular endothelial growth factor-mRNA expression in hepatocytes was decreased during primary culture, but increased following a peak of DNA synthesis, induced by addition of epidermal growth factor or hepatocyte growth factor to the culture medium at 24 h of plating. In a 70% resected rat liver, VEGF-mRNA expression increased with a peak at 72 h after the operation, and mRNA expression of VEGF receptors between 72 and 168 h. In such a liver, mitosis was maximal in hepatocytes at 36 h and in sinusoidal endothelial cells at 96 h. Also, mRNA expression of both VEGF and its receptors was significantly increased in carbon tetrachloride-intoxicated rat liver compared with normal rat liver. Vascular endothelial growth factor expression was minimal in Kupffer cells isolated from normal rats, but marked in activated Kupffer cells and hepatic macrophages from the intoxicated rats. Vascular endothelial growth factor-mRNA expression was also increased in activated stellate cells from these rats and in the cells activated during primary culture compared with quiescent cells. We conclude that increased levels of VEGF expression in regenerating hepatocytes may contribute to the proliferation of sinusoidal endothelial cells in partially resected rat liver, probably through VEGF receptors up-regulated on the cells. Also, VEGF derived from activated Kupffer cells, hepatic macrophages and stellate cells may be involved in this proliferation in injured rat liver.

Animals↗
PubMed1998

[Concentrations of free form and complex form of prostate-specific antigen in serum of alpha 2 macroglobulin deficient patients with prostatic carcinoma].

Prostate-specific antigen (PSA) is present in blood in free form as well as in complex form with various protease inhibitors such as alpha 2 macroglobulin (alpha 2M) and alpha 1 antichymotrypsin (alpha 1 ACT). We had found that alpha 2M is deficient (below approximately 40 mg/dl) in some patients with prostatic carcinoma. Therefore, we investigated the levels of free and complex form of PSA in patients with prostatic disease and obtained the following results. The HPLC study showed that total (free plus complex) PSA level was much higher in the alpha 2M deficient patients with prostatic carcinoma stage D (n = 7, range 1,530-14,746 ng/ml, median value 6,800 ng/ml) than in the non-deficient patients with stage D (n = 16, range 121.6-4,210 ng/ml, median value 851 ng/ml). In the deficient patients, the complex of PSA with alpha 1 ACT increased extraordinarily while free PSA increased to only some extent. In the more severe cases of prostatic carcinoma, the ratio (complex/total PSA) was higher while the ratio (free/total PSA) was lower. The SDS-PAGE Western blotting showed that complex PSA increased extraordinarily and free PSA increased in sera of the deficient patients which was consistent with the HPLC results. Many bands appeared on the blotting at the positions smaller than alpha 2M molecule, which indicated that many fragments of alpha 2M were present in their sera. These bands were more intense than the bands with sera of controls or benign prostatic hypertrophy. The alpha 2M deficiency may be due to the rapid disappearance of the complex with PSA or any other prostate-originated proteases. The complex may undergo accelerated degradation or catabolism of alpha 2M.

Aged↗
PubMed1998

[Quantitative levels of serum amyloid A protein and other proteins in cerebrospinal fluid and serum of patients with meningitis].

Serum amyloid A protein (SAA), a putative precursor of the AA protein which constitutes amyloid fibrils in secondary amyloidosis, is evaluated as a sensitive acute-phase reactant in serum. At present, SAA concentration in serum is determined by latex nephelometry, but this assay cannot detect SAA in the low concentration range lower than 10 ng/ml. We have developed a sensitive enzyme immunoassay (EIA) for determining low concentrations of SAA. The assay is reproducible, reliable and requires no pretreatment of specimen prior to assay. We measured levels of SAA by this EIA in both cerebrospinal fluid (CSF) and serum of patients with suspected meningitis, measured also levels of albumin, alpha 2 macroglobulin and C-reactive protein (CRP) to investigate if these protein levels are useful for differential diagnoses of meningitis and for indicators damage of blood-CSF barrier. The SAA reference value in CSF is 3.99 +/- 1.74 ng/ml (mean +/- SD for nonmeningitis patients). The CRP concentration in CSF in bacterial meningitis was much higher than in viral meningitis, but CRP in CSF was also high in bacterial infection other than meningitis. On the other hand, SAA concentration in CSF in these patients with any meningitis are significantly higher than the reference values of SAA (p < 0.001). However, the differences in SAA concentrations among the three types (bacterial, viral and mycotic meningitis) of meningitis were not significant.

Acute-Phase Proteins↗
PubMed1997

Tyrosine residues 239 and 240 of Shc are phosphatidylinositol 4,5-bisphosphate-dependent phosphorylation sites by c-Src.

In the previous study (Sato K.-I. et al. (1997) FEBS Lett. 410, 136-140), we showed that the phosphorylation of Shc protein by c-Src is dependent on the binding of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) to the PTB domain of Shc. In this study, we demonstrate that, in contrast to c-Src, v-Src and epidermal growth factor (EGF) receptor can phosphorylate Shc in a PtdIns(4,5)P2-independent manner and at different phosphorylation sites. To determine the phosphorylation sites in Shc, we used mutant Shc proteins in which tyrosine residues (Y) 317 and/or 239 and 240 were replaced by phenylalanine residues (F). We found that Y317F Shc but not Y239/240F or Y239/240/317F Shc was phosphorylated by c-Src. The reaction was PtdIns(4,5)P2-dependent and inhibited by the addition of PTB domain of Shc. On the other hand, v-Src and EGF receptor were able to phosphorylate both Y317F and Y239/240F but not Y239/240/317F Shc in a PtdIns(4,5)P2-independent manner. These results highlight the difference between c-Src and v-Src or EGF receptor and suggest that c-Src can phosphorylate predominantly on Tyr239/240 of Shc only when Shc PTB domain is bound to PtdIns(4,5)P2.

Adaptor Proteins, Signal Transducing↗
PubMed1997

The phosphorylated 1169-tyrosine containing region of flt-1 kinase (VEGFR-1) is a major binding site for PLCgamma.

Flt-1, a tyrosine kinase receptor for vascular endothelial growth factor (VEGF), plays important roles in the angiogenesis required for embryogenesis and in monocyte/macrophage migration. However, the signal transduction of Flt-1 is poorly understood due to its very weak tyrosine kinase activity. Therefore, we overexpressed Flt-1 in insect cells using the Baculovirus system in order to examine for autophosphorylation sites and association with adapter molecules such as phospholipase Cgamma-1 (PLCgamma). Tyr-1169 and Tyr-1213 on Flt-1 were found to be auto-phosphorylated, but only a phenylalanine mutant of Tyr-1169 strongly suppressed its association with PLCgamma. In Flt-1 overexpressing NIH3T3 cells, VEGF induced autophosphorylation of Flt-1, tyrosine-phosphorylation of PLCgamma and protein kinase C-dependent activation of MAP kinase. These results strongly suggest that Tyr-1169 on Flt-1 is a major binding site for PLCgamma and important for Flt-1 signal transduction within the cell.

Animals↗
PubMed1997

Effects of adrenomedullin on rat cerebral arterioles.

The effects of adrenomedullin on isolated rat intracerebral arterioles were investigated and compared with those of calcitonin gene-related peptide (CGRP) and amylin. Adrenomedullin produced dose-dependent vasodilation (maximum dilation 27.1 +/- 2.1% at 3 x 10(-7) M, median effective dose (EC50)) 1.6 x 10(-9) M). CGRP produced similar vasodilation (19.8 +/- 4.1%) at 10(-7) M with a lower EC50 of 2.8 x 10(-11) M. Amylin did not cause vasodilation at concentrations up to 10(-6) M. Adrenomedullin-induced vasodilation was significantly suppressed by CGRP-(8-37). These data suggest that adrenomedullin is a potent vasodilator for arterioles in the cerebral microcirculation that acts through CGRP receptors.

Adrenomedullin↗
PubMed1997

The 230 kDa mature form of KDR/Flk-1 (VEGF receptor-2) activates the PLC-gamma pathway and partially induces mitotic signals in NIH3T3 fibroblasts.

KDR/Flk-1 tyrosine kinase, one of the two receptors for Vascular Endothelial Growth Factor (VEGF) has been shown to generate the major part of mitotic signals in endothelial cells, although the mechanisms are poorly understood. Here we examined the processing and signal transduction of KDR/Flk-1. Both in endothelial cells and in NIH3T3 cells expressing KDR/Flk-1, an immature form of KDR/Flk-1 with a molecular mass of about 150 kDa was glycosylated to create a 200 kDa intermediate, and after further glycosylation a mature 230 kDa was expressed on the cell surface. Only this 230 kDa form was rapidly and transiently phosphorylated on tyrosine residues in the presence of VEGF. As a major substrate of KDR/Flk-1, PLC-gamma was found to be rapidly tyrosine-phosphorylated and associated with KDR/Flk-1 both in endothelial cells and NIH3T3 cells. Interestingly, however, a prompt activation of MAP kinase and subsequent strong mitotic signaling were generated only in the endothelial cell background. Activation of MAP kinase in NIH3T3 cells overexpressing KDR/Flk-1 showed a slower response as maximum levels were only attained after 20 min compared to 5 min in sinusoidal endothelial cells. These results suggest that the KDR/Flk-1 utilizes cell type-specific signal transduction pathway(s) for MAP kinase activation and the mitotic response in endothelial cells.

3T3 Cells↗
PubMed1997

Vasodilator effects of C-type natriuretic peptide on cerebral arterioles in rats.

The vasodilator effects of C-type natriuretic peptide (CNP) were investigated in isolated rat cerebral arterioles. CNP caused dose-dependent vasodilation, maximally by 10.0 +/- 2.2% at 10(-6) M. The median effective concentration (EC50) was 5.2 x 10(-10) M. In contrast, atrial natriuretic peptide and B-type natriuretic peptide, other members of the natriuretic peptide family, produced little or no vasodilation. Pretreatment with methylene blue (10(-4) M) abolished CNP-induced vasodilation, whereas pretreatment with NG-monomethyl-L-arginine or indomethacin did not inhibit vasodilation. Thus, CNP is suggested to cause significant vasodilation in cerebral arterioles via a cyclic guanosine monophosphate-dependent mechanism.

Animals↗
PubMed1997

A new table-fixed soft tissue retractor for the anterior cervical spinal surgery.

Since surgeons sometimes encounter difficulty in keeping self- retaining soft tissue retractors in the proper position for anterior cervical spinal surgery, we have developed a new, simple soft tissue retractor system, which is fixed to the side rails of the operating table via retractor stands. All three joints of the retractor can be tightened simultaneously with a single handle. Each of two retractor blades can keep its position independent of the other thereby maintaining a well-exposed operative field for a long period of time. Fine adjustments of the blade position, after fixation of the retractors, is possible by sliding the head of the blade assembly along the axis of a ratchet mechanism. We have used these retractors in 43 surgical exposures, including 35 for anterior cervical fusion, 2 for posterior thoraco-lumbar decompression, and 6 for carotid endarterectomy. There have been no complications related to tissue damage.

Cervical Vertebrae↗
PubMed1997

Thromboxane A2 synthetase inhibitor failed to ameliorate the arterial narrowing during the chronic phase of cerebral vasospasm.

To determine the pathogenetic mechanism underlying the maintenance of arterial narrowing during the chronic phase of cerebral vasospasm caused by subarachnoid hemorrhage (SAH), we examined the effect of ozagrel, a thromboxane A2 (TXA2) synthetase inhibitor, on chronic vasospasm in a canine two-hemorrhage model in comparison with that of fasudil, an inhibitor of protein kinases. The magnitude of the vasospasm was determined angiographically. On SAH day 7, a vasospasm was observed in every dog. Intraarterial or intravenous administration of ozagrel (3 mg/kg/30 min) did not reverse the vasospasm but tended to increase bleeding. In contrast, intraarterial administration of fasudil (3 mg/kg/30 min) significantly reversed the vasospasm. These findings suggest that: 1) TXA2 does not participate in the maintenance of chronic vasospasm after SAH; and 2) the protein kinases, particularly myosin-light chain kinase and protein kinase C, are involved in the pathogenesis of arterial narrowing during the chronic phase of cerebral vasospasm.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1997

Increased expression of vascular endothelial growth factor in human hepatocellular carcinoma.

BACKGROUND/AIMS: Angiogenesis is critical for the development and progression of solid tumors. The purpose of this study was to evaluate the possible role of vascular endothelial growth factor (which is considered to be one of the most important factors involved in tumor-associated angiogenesis), in human hepatocellular carcinoma. METHODS: Vascular endothelial growth factor gene and protein expression were analyzed by means of Northern hybridization and immunohistochemical methods in 5 hepatocellular carcinoma cell lines. Secretion of vascular endothelial growth factor was evaluated by immunoblotting of conditioned medium of these hepatocellular carcinoma cells. Further, we compared the level of vascular endothelial growth factor expression in hepatocellular carcinoma tissues along with that in surrounding tumor-free tissues obtained from 20 patients. We also analyzed mRNA expression of Flt-1, one of the vascular endothelial growth factor specific high-affinity receptors, in hepatocellular carcinoma cell lines. RESULTS: Northern hybridization analysis and immunohistochemistry revealed that all cultured hepatocellular carcinoma cells exhibited a high level of vascular endothelial growth factor mRNA. In addition, vascular endothelial growth factor secretion by Hep G2, one of the hepatocellular carcinoma cell lines, was shown by Western blot. In vivo, we observed vascular endothelial growth factor expression in both hepatocellular carcinoma and non-hepatocellular carcinoma tissues. However, in 12 of 20 cases, vascular endothelial growth factor mRNA levels were significantly up-regulated in hepatocellular carcinoma tissues. In the majority of cases (10 out of 12 cases) with abundant tumor vascularity, vascular endothelial growth factor mRNA up-regulation in hepatocellular carcinoma tissues was observed. We failed to detect Flt-1 mRNA expression in hepatocellular carcinoma cells. CONCLUSIONS: This study suggests that the possibility that hepatocellular carcinoma cells overexpress the vascular endothelial growth factor gene and protein. These findings support the hypothesis that vascular endothelial growth factor is one of the important factors involved in the angiogenesis of hepatocellular carcinoma, and may even be involved in the development and/or progression of hepatocellular carcinoma itself.

Adolescent↗
PubMed1997

Intravenous infusion of adrenomedullin and increase in regional cerebral blood flow and prevention of ischemic brain injury after middle cerebral artery occlusion in rats.

The intravenous infusion of rat adrenomedullin, at concentrations ranging from 0.1 to 1.0 microgram/kg/min, for 60 min increased the regional cerebral blood flow (rCBF) in a dose-dependent manner in rats. rCBF was measured using a laser Doppler flowmetry device placed on the surface of the parietal cortex. The increase in rCBF induced by 1.0 microgram/kg/min of adrenomedullin was up to 145 +/- 10.8% of controls at 60 min (n = 5, p < 0.001). These concentrations of adrenomedullin did not affect systemic blood pressure or other physiologic parameters, including pH, PaCO2, PaO2, hemoglobin, and blood glucose. Repeated infusion of 1.0 microgram/kg/min of adrenomedullin at 2-h intervals caused tachyphylaxis (n = 5, p < 0.01). Rat adrenomedullin (1.0 microgram/kg/min) demonstrated a more potent effect than the same dose of human adrenomedullin. The C-terminal fragment of human adrenomedullin (0.5 and 5.0 micrograms/kg/min), adrenomedullin22-52, which did not affect rCBF alone, inhibited the effect of rat adrenomedullin (0.5 microgram/kg/min) as a receptor antagonist in a dose-dependent manner. In a model of middle cerebral artery (MCA) occlusion in spontaneously hypertensive rats, pre- and postinfusion of 1.0 microgram/kg/min of adrenomedullin suppressed the reduction in rCBF following MCA occlusion (control, 29 +/- 15.1%; adrenomedullin group, 45 +/- 14.4%; not significant) and decreased the volume of ischemic brain injury (control, 288 +/- 35 mm3; adrenomedullin group, 232 +/- 35 mm3; p < 0.05). These results suggest that adrenomedullin increases rCBF and prevents ischemic brain injury, partly by increasing the collateral circulation.

Adrenomedullin↗
PubMed1997

Vasodilator effects on canine basilar artery induced by intracisternal interleukin-1 beta.

The effect of interleukin-1 beta (IL-1 beta) on a cerebral artery was investigated in anesthetized dogs. Intracisternal administration of IL-1 beta (0.03 and 0.3 micrograms) dilated the canine basilar artery in a dose-dependent manner, without affecting systemic blood pressure or heart rate. The increase in diameter induced by 0.3 micrograms of IL-1 beta was 28.4% +/- 13.4% of control at 2 hours and was inhibited by 30 micrograms of the IL-1 beta receptor antagonist, zinc protoporphyrin (4.5% +/- 13.5%, P < 0.05). Interleukin-1 beta did not affect the concentration of nitric oxide metabolites in CSF. However, there was an increase in the concentration of eicosanoids in CSF, and the elevation of 6-keto-PGF1 alpha paralleled the vasodilation. Pretreatment with 30 micrograms of the selective inducible cyclooxygenase (COX-2) inhibitor NS-398 also inhibited the IL-1 beta-induced vasodilation significantly (5.9% +/- 9.4% at 2 hours, P < 0.01). Western blot analysis revealed the expression of a 68-kD COX-2-like protein in basilar artery extracts. These findings suggest that the IL-1 beta-induced vasodilator effect is linked to the prostaglandin cascade, predominantly to prostaglandin I2, by induction of COX-2, but not to the stimulation of nitric oxide metabolism.

Animals↗
PubMed1997

A comparative study of intracranial aneurysm clips: closing and opening forces and physical endurance.

OBJECTIVE: The closing and opening forces of various types of intracranial aneurysm clips were measured, and the physical endurance of the clips was evaluated. METHODS: Straight, bayonet, angled, fenestrated, and temporary Sugita and Yasargil clips were tested by measuring the forces exerted by the blades as they were opened in wider increments and at various points along their length by a specially designed clip tester. Closing forces after repeated openings, continuous opening, or multiple sterilization procedures also were measured. RESULTS: The opening forces of Yasargil clips increased linearly and more sharply as the blades were opened wider than those of Sugita clips. Only Sugita clips showed significant differences between the opening and closing forces (hysteresis). Closing forces of all of the tested clips were according to a hyperbolic curve. Straight clips showed a sharper rise in closing forces than those of bayonet, angled, or fenestrated clips. A relatively weak closing force at the tip of Yasargil long clips and a strong closing force at the base of temporary clips were unexpected findings. The closing force decreased by only 3 to 7% after 500 openings and did not decrease after continuous opening for 17 hours or 100 sterilization procedures. CONCLUSION: Our study showed that the closing forces differed depending not only on the distance of the point of measurement from the clip spring but also on the shapes of the clip blades. Repeated opening or sterilization of the clips did not significantly decrease the closing forces of the aneurysm clips.

Biomechanical Phenomena↗
PubMed1997

Surgical treatment for pediatric moyamoya disease: use of the superficial temporal artery for both areas supplied by the anterior and middle cerebral arteries.

OBJECTIVE: To revascularize ischemic territories of both the anterior cerebral artery (ACA) and the middle cerebral artery (MCA), a simple and effective combined bypass operation was performed in 36 pediatric patients with moyamoya disease during the past 8 years. METHODS: The branches of the superficial temporal artery (STA) were used to revascularize the ACA and MCA territories. In children older than 5 years, the parietal branch of the STA was usually used for an end to side anastomosis with a cortical branch of the MCA. In children who were younger than 5 years, the parietal branch of the STA was used for an encephaloduroarteriosynangiosis instead of a direct anastomosis. Encephaloduroarteriosynangiosis, using the proximal part of the intact frontal branch of the STA, and encephalomyosynangiosis, using the temporal muscle, were also performed in all patients to stimulate spontaneous anastomosis. In addition, bilateral frontal burr holes were made in all patients to induce vascularization of the ACA territories from the distal part of the intact frontal branch of the STA. The first operation was performed on the dominant side, then a similar procedure was performed on the opposite side after an interval of at least 3 months. RESULTS: Postoperative clinical symptoms and the findings from magnetic resonance imaging, magnetic resonance angiography, angiography, and electroencephalography demonstrated improvement in all patients. CONCLUSION: These results suggest that the placement of bilateral burr holes (while leaving the frontal branch of the STA intact), in addition to the STA-MCA anastomosis, encephaloduroarteriosynangiosis, and encephalomyosynangiosis, is very effective in vascularizing the ischemic ACA and MCA territories in pediatric patients with moyamoya disease.

Adolescent↗
PubMed1997

Nitric oxide metabolites in the cisternal cerebral spinal fluid of patients with subarachnoid hemorrhage.

OBJECTIVE: To investigate nitric oxide (NO) metabolism after subarachnoid hemorrhage (SAH). METHODS: We measured the concentrations of the NO metabolites, nitrite and nitrate, in cerebrospinal fluid (CSF) obtained from the cisternal drainage of patients with SAH. Studies were performed for 31 patients who had undergone surgical obliteration of bleeding aneurysms within 3 days of their hemorrhage. The concentrations of nitrite and nitrate in the CSF were measured for 14 days using a nitrate/nitrite kit and samples that were obtained on a daily basis from the cisternal drainage. RESULTS: Compared with the control values in the CSF (2.6 +/- 0.4 mumol/L, n = 14) obtained from patients with hemifacial spasm, trigeminal neuralgia, or nonruptured aneurysms, the concentrations of nitrite and nitrate in the CSF were significantly elevated in the acute stage of SAH and remained elevated. The concentration of NO metabolites may correlate with the amount of bleeding, inasmuch as the values in patients in Fisher Group 3 (n = 25) were higher than those in patients in Fisher Group 2 (n = 6). The concentration of nitrate was higher than that of nitrite, suggesting that NO in the subarachnoid space is mainly absorbed by hemoglobin and degraded to nitrate. No differences were demonstrated in patients treated with high doses of methylprednisolone (n = 17) compared with those treated with usual-dose steroids (n = 14). Steroids are known to prevent the formation of inducible NO synthase mediated by inflammatory cytokines. CONCLUSION: NO metabolism in the brain is stimulated after SAH. Nitrate is the dominant NO metabolite in CSF after SAH. The involvement of inducible NO synthase in the pathophysiology of NO metabolism after SAH was not clearly suggested based on the present data.

Adult↗
PubMed1997

Characterization of the extracellular domain in vascular endothelial growth factor receptor-1 (Flt-1 tyrosine kinase).

Flt-1 tyrosine kinase, vascular endothelial growth factor (VEGF) receptor-1, binds VEGF and a new VEGF-related ligand, placenta growth factor, but KDR/Flk-1 (VEGF receptor-2) binds only VEGF. To characterize the functional regions in the Flt-1 extracellular domain such as the ligand binding region and the dimer formation of the receptor, we constructed a series of mutants of the Flt-1 extracellular domain as soluble forms in a baculovirus system. We found that a region carrying the N-terminal 1st to 3rd immunoglobulin (Ig)-like domains of Flt-1 binds both ligands with high affinity. However, for dimer formation of soluble Flt-1, a region further downstream in the Flt-1 extracellular domain was required. Mutant Flt-1 receptors expressed in COS cells confirmed the requirement of the 4th to 7th Ig region for the activation of Flt-1 tyrosine kinase. Soluble Flt-1 carrying the N-terminal 1st to 3rd Ig region suppressed VEGF-dependent endothelial proliferation in vitro to the same level as the larger forms of soluble Flt-1, suggesting that the binding of one soluble Flt-1 molecule to one subunit of the VEGF homodimer may be sufficient to block the VEGF activity.

Animals↗