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Biomedical subjects

M Sato

Publications and source records attributed to M Sato.

At least 379 records · Page 21Linked to original sources
PubMed2000

Myocardial protection by preconditioning of heart with losartan, an angiotensin II type 1-receptor blocker: implication of bradykinin-dependent and bradykinin-independent mechanisms.

BACKGROUND: Ischemic preconditioning (PC) represents a state-of-the-art technique for myocardial preservation. Although certain intracellular mediators have been shown to play a role in PC, the exact nature of the trigger for PC is not known. Our previous study demonstrated that intracellular bradykinin released from the heart during ischemia/reperfusion plays a role in myocardial preservation. This study was undertaken to further examine the mechanism of bradykinin-mediated PC. METHODS AND RESULTS: Since the bradykinin B(2) receptor is likely to provide cardioprotection by blocking angiotensin II formation, we determined the effects of an angiotensin II type 1 (AT(1)) receptor blocker, losartan, and a bradykinin B(2) receptor blocker, HOE 140, on myocardial protection. Isolated rat hearts were perfused initially by the Langendorff mode with Krebs-Henseleit buffer (KHB) for 15 minutes in the absence (control) or presence of losartan (4.5 micromol/L) and/or HOE 140 (10 micromol/L). After conversion to the working mode for 10 minutes (baseline), randomly assigned control and experimental hearts were subjected to 30 minutes of normothermic global ischemia followed by 2 hours of reperfusion. Myocardial function, infarct size, cardiomyocyte apoptosis, and amount of bradykinin/angiotensin released from the hearts were measured at baseline and during reperfusion while in the working mode. Significant postischemic ventricular recovery was demonstrated by improved developed pressure and aortic flow and reduced myocardial infarct size and apoptotic cell death with losartan, whereas the reverse was true for HOE 140. The functional recovery and infarct size-lowering ability of losartan were partially blocked and the antiapoptotic function of losartan was completely blocked by HOE 140. CONCLUSIONS: The results document that losartan reduced whereas HOE 140 increased myocardial ischemia/reperfusion injury by blocking AT(1) and bradykinin B(2) receptors, respectively, suggesting a role of the bradykinin B(2) receptor in PC. Losartan provided cardioprotection through both bradykinin-dependent and bradykinin-independent mechanisms.

Adrenergic beta-Antagonists↗
PubMed2000

Mechanism for bone invasion of oral cancer cells mediated by interleukin-6 in vitro and in vivo.

BACKGROUND: Osteoclastic bone resorption is an important step in bone invasion in several malignancies. Although interleukin (IL)-6 accelerates osteoclastic bone resorption, it remains unclear whether IL-6 may be involved in bone invasion of oral cancer. METHODS: The pit formation assay with calf femur-derived bone slices was performed to examine the bone-resorbing activity of osteoclasts and cancer cells. The chemotaxis activity of the culture media was analyzed by the use of Boyden chamber technique. Nude mice, which were inoculated with IL-6-producing oral cancer cells into masseter, were treated with anti-IL-6 neutralizing antibody, and mandibular-bone invasion of the cells was assessed. RESULTS: BHY, a bone-invasive oral cancer cell line, but not HNT, a noninvasive cell line, produced large amounts of IL-6. In a pit formation assay, addition of conditioned medium (CM) derived from BHY but not HNT increased osteoclastic bone resorption, and the effects were inhibited by anti-IL-6 antibody. BHY-secreted IL-6 showed significant chemotaxis activity for osteoclasts. Of note, CM from the cocultivation of osteoclasts and BHY markedly enhanced the cancer cell migration, and the chemotaxis activity was significantly reduced when anti-IL-6 antibody was added into the coculture and then CM were collected, but not when the antibody was added into the CM after they were collected. Furthermore, treatment with anti-IL-6 antibody almost completely inhibited mandibular bone invasion of BHY in nude mice. CONCLUSIONS: These results strongly suggest that IL-6 secreted by oral cancer cells plays a significant role in bone invasion.

Animals↗
PubMed2000

Expression of the Varicella Zoster Virus Thymidine Kinase and Cytokines in Patients with Acute Retinal Necrosis Syndrome.

Purpose: Acute retinal necrosis (ARN) is caused by varicella zoster virus (VZV) infection. In this study, we investigated the activity of this virus and expressions of some cytokines.Patients and Methods: The expressionof VZV thymidine kinase and some cytokines were investigated by reverse transcriptase-polymerase chain reaction (RT-PCR) in 9 eyes of 8 patients with ARN.Results: Thymidine kinase expression was observed in all samples except one. Several cytokines, such as interferon (IFN) gamma, tumor necrosis factor (TNF)alpha, interleukin (IL)-1 beta, IL-6, and transforming growth factor (TGF)beta 1 were observed in the samples. Among these cytokines, a statistically significant expression of IFNgamma was observed in the samples of ARN, when compared to those of proliferative vitreoretinopathy (PVR) or other uveitis. The expression of IFNgamma also decreased during successive follow-ups.Conclusion: These cytokines may play an important role in the immune response in ARN.

Journal Article↗
PubMed2000

A fluorescent indicator for detecting protein-protein interactions in vivo based on protein splicing.

We describe a new method with general applicability for monitoring any protein-protein interaction in vivo. The principle is based on a protein splicing system, which involves a self-catalyzed excision of protein splicing elements, or inteins, from flanking polypeptide sequences, or exteins, leading to formation of a new protein in which the exteins are linked directly by a peptide bond. As the exteins, split N- and C-terminal halves of enhanced green fluorescent protein (EGFP) were used. When a single peptide consisting of an intein derived from Saccharomyces cerevisiae intervening the split EGFP was expressed in Escherichia coli, the two external regions of EGFP were ligated, thereby forming the EGFP corresponding fluorophore. Genetic alteration of the intein, which involved large deletion of the central region encoding 104 amino acids, was performed. In the expression of the residual N- and C-terminal intein fragments each fused to the split EGFP exteins, the splicing in trans did not proceed. However, upon coexpression of calmodulin and its target peptide M13, each connected to the N- and C-terminal inteins, fluorescence of EGFP was observed. These results demonstrate that interaction of calmodulin and M13 triggers the refolding of intein, which induces the protein splicing, thereby folding the ligated extein correctly for yielding the EGFP fluorophore. This method opens a new way not only to screen protein-protein interactions but also to visualize the interaction in vivo in transgenic animals.

Calmodulin↗
PubMed2000

Analysis of deletion mutations of the rpsL gene in the yeast Saccharomyces cerevisiae detected after long-term flight on the Russian space station Mir.

Using the yeast Saccharomyces cerevisiae on board the Russian space station Mir, we studied the effects of long-term space flight on mutation of the bacterial ribosomal protein L gene (rpsL) cloned in a yeast-Escherichia coli shuttle vector. The mutation frequencies of the cloned rpsL gene on the Mir and the ground (control) yeast samples were estimated by transformation of E. coli with the plasmid DNAs recovered from yeast and by assessment of the conversion of the rpsL wild-type phenotype (Sm(S)) to its mutant phenotype (Sm(R)). After a 40-day space flight, some part of space samples gave mutation frequencies two to three times higher than those of the ground samples. Nucleotide sequence analysis showed no apparent difference in point mutation rates between the space and the ground mutant samples. However, the greater part of the Mir mutant samples were found to have a total or large deletion in the rpsL sequence, suggesting that space radiation containing high-linear energy transfer (LET) might have caused deletion-type mutations.

Base Sequence↗
PubMed2000

Detection of localized methylmercury contamination by use of the mussel adductor muscle in Minamata Bay and Kagoshima Bay, Japan.

Based on our previous finding that the concentrations of total mercury in mussel adductor muscle approximated those of methylmercury, we compared concentrations of total mercury in the adductor muscle of the mussel Mytilus galloprovincialis, collected from four sites around Minamata City from 1993 to 1995 and four sites in Kagoshima Bay from 1997 to 1998, to assess the level of localized methylmercury contamination. Though the input of mercury from the chemical plant had stopped by around 1970, concentrations of total mercury in the mussel adductor muscle were higher at two sites (26-121 ng/g, n = 135) near the main fallout of wastewater from the chemical plant in Minamata Bay than at the other sites, i.e. two sites 1-5 km from the former sites in Minamata City (6-28 ng/g, n = 52), and all sites in Kagoshima Bay (2-30 ng/g, n = 287). The localized methylmercury contamination around the chemical plant in Minamata Bay was documented also by our sensitive analysis of mercury concentrations in seawater and sediment samples. The survey of concentrations of total mercury in the mussel adductor muscle seems to be useful for monitoring the methylmercury contamination in coastal areas.

Animals↗
PubMed2000

Homeobox gene Hex is essential for onset of mouse embryonic liver development and differentiation of the monocyte lineage.

Disruption of the mouse Hex gene resulted in embryonic lethality around embryonic age (E) 10.5, due to no substantial liver formation. Expression of albumin was detectable in heterozygous (Hex(+/-)) but not in homozygous (Hex(-/-)) [corrected] embryos at E8.5. Instead of liver bud formation at E9.5, a liver-like capsule structure was observed in Hex(-/-) [corrected] embryos. In Hex(-/-) [corrected] mutant liver, we found no hepatocytes but no signs of apoptotic cell death in the area. Expression of transcription factors involved in hepatocyte differentiation, hepatocyte nuclear factor (Hnf)3beta, Hnf6, Hnf4alpha and Hnf1alpha, were restricted to the capsule and internal matrix-like structure in the mutant liver and expression of a subset of these factors were reduced. Hematopoiesis of monocytes was impaired in mutant embryos while erythroid lineage was unaffected. These results indicate that Hex plays an essential role in progenitor cells which commit to the hepatic endoderm and in the hematopoietic differentiation of the monocyte lineage.

Albumins↗
PubMed2000

Molecular cloning of ring finger protein 21 (RNF21)/interferon-responsive finger protein (ifp1), which possesses two RING-B box-coiled coil domains in tandem.

We have cloned the full length of a novel cDNA, named ring finger protein 21 (RNF21), composed of the RING finger-B box-coiled coil (RBCC) domain and the B30.2 domain, which are characteristic of the RBCC-B30.2 family. As a structural feature, the RNF21 cDNA possessed at least three kinds of isoforms, due to alternative splicing, consisting of the long form with the RBCC-RBCC-B30.2 domain, the medium form with the RBCC-B30.2 domain, and the short form with only the RBCC domain. Moreover, respective transcripts corresponding to the three isoforms were detected in various human organs by reverse transcription-PCR and Northern blot analyses. Interestingly, the medium form of the RNF21 mRNA expressed most predominantly was dramatically up-regulated within 8-16 h by interferon stimulation of HeLa cells. These findings suggest that RNF21 is a downstream gene that may mediate interferon's biological action.

Alternative Splicing↗
PubMed2000

Screening of the Men1 gene and discovery of germ-line and somatic mutations in apparently sporadic parathyroid tumors.

Hyperparathyroidism is the first manifestation in a majority of multiple endocrine neoplasia (MEN1) patients. To discriminate between sporadic and hereditary parathyroid tumors and characterize MEN1 somatic mutations, we examined MEN1 gene mutations in patients who had undergone surgery for sporadic parathyroid tumors. DNA was extracted from fresh frozen parathyroid tumor specimens from 112 patients as well as from peripheral blood leukocytes from 64 of the 112 patients. Sequence analysis was performed to examine exons 2-10 of the MEN1 gene for mutations. Loss of heterozygosity (LOH) was also examined by an analysis of codon 418 and 541, which lie within a polymorphic region of MEN1. Somatic MEN1 mutations were found in 25 of the 112 patients (22%). Two patients had two point mutations (508del33 and Y341X and 363insT and 1767delT, respectively). A total of 27 mutations were characterized, 20 of which have not been reported previously. There were 7 nonsense mutations, 10 frameshift mutations, 2 splice site deletions, 5 missense mutations, and 3 in-frame mutations. Nineteen mutations (70%) predicted truncation of the menin protein. Germ-line MEN1 mutations were found in 3 of 64 patients (5%) who had no family history of endocrine tumors associated with MEN1, and these patients were identified as MEN1 gene probands. LOH at the MEN1 locus was detected in three parathyroid tumors showing germ-line mutation. LOH was significantly frequent in parathyroid tumors with somatic MEN1 mutations (15 of 22 tumors, 68%) but not in those without germ-line or somatic MEN1 mutations (14 of 51 tumors, 28%; P = 0.0011). Our findings suggest that alterations of both alleles of the MEN1 gene may be associated not only with endocrine tumors of affected MEN1 patients but also with sporadic parathyroid tumors. Germ-line MEN1 gene analysis can distinguish heritable from nonheritable parathyroid tumors, and MEN1 gene evaluation of patients with apparently sporadic parathyroid tumor is recommended before parathyroid surgery.

Adult↗
PubMed2000

Sphingosylphosphorylcholine induces Ca(2+)-sensitization of vascular smooth muscle contraction: possible involvement of rho-kinase.

Sphingosylphosphorylcholine (SPC), a sphingolipid, concentration-dependently (1-50 microM) induced contraction and slight elevation of the cytosolic Ca(2+) concentration ([Ca(2+)](i)) in smooth muscle of the pig coronary artery, the result being a marked increase in the force/[Ca(2+)](i) ratio. In alpha-toxin- or beta-escin-permeabilized, but not Triton X-100-permeabilized, vascular strips, SPC induced contraction at constant [Ca(2+)](i) (pCa 6.3) in the absence of GTP, whereas a G-protein-coupled receptor agonist, histamine, required the presence of GTP to induce the contraction. The Rho-kinase blocker, Y-27632 (10 microM) abolished the SPC-induced Ca(2+)-sensitization, without affecting the Ca(2+)-induced contraction. These results suggest that SPC induces Ca(2+)-sensitization of force in vascular smooth muscle, presumably through the activation of Rho-kinase (or a related kinase).

Amides↗
PubMed2000

TNF-alpha stimulation of MCP-1 expression is mediated by the Akt/PKB signal transduction pathway in vascular endothelial cells.

MCP-1 is expressed in a variety of cell types including vascular endothelial cells following induction by different stimuli such as tumor necrosis factor (TNF)-alpha. Although TNF-alpha stimulates MCP-1 expression and secretion, the mechanism by which TNF-alpha stimulates expression of the MCP-1 gene is not known. In this study, we examine the involvement of the phosphatidylinositol-3-OH kinase (PI3-kinase)-Akt/PKB pathway. Exposure of human umbilical vein endothelial cells (HUVECs) to TNF-alpha elicited the rapid phosphorylation of Akt/PKB. In HUVECs, wortmannin, a PI3-kinase inhibitor, inhibits TNF-alpha-mediated MCP-1 secretion at a dose-dependent manner. Constitutively active form of Akt/PKB induces transcription of the MCP-1 gene, and cotransfection of dominant negative Akt/PKB suppressed the activation of the MCP-1 promoter induced by TNF-alpha. These findings show that Akt/PKB participates in the TNF-alpha induction of MCP-1 gene transcription in endothelial cells.

Androstadienes↗
PubMed2000

Molecular cloning of testis-abundant finger Protein/Ring finger protein 23 (RNF23), a novel RING-B box-coiled coil-B30.2 protein on the class I region of the human MHC.

We have identified a genomic DNA fragment, using the PCR method with degenerate oligonucleotide primers which contain the conserved sequence of the RING finger domain. Using the DNA fragment as a probe, a novel cDNA was cloned from human and mouse testis. The cDNA had a domain structure of the typical RING-B box-coiled coil (RBCC)-B30.2 domain and therefore was named testis-abundant finger protein (tfp). Indeed, the transcript was highly expressed in the testis, although it was also found ubiquitously in various organs by Northern blot analysis. The tfp gene was mapped at the class I region of the human MHC (major histocompatibility complex), within which some known RBCC-B30.2 proteins such as RFP, RFB30/HERF1, AFP, and HZF had been localized. These findings demonstrate that several RBCC-B30.2 proteins including tfp, which are non-HLA proteins, are clustered within the class I region of the human MHC.

Amino Acid Sequence↗
PubMed2000

Absolute stereochemistry of amphidinolides G and H.

[structure: see text] Absolute stereochemistry of amphidinolides G (1) and H (2), potent cytotoxic 27- and 26-membered macrolides, respectively, isolated from a marine dinoflagellate Amphidinium sp., was determined by X-ray diffraction analysis, synthesis of a degradation product (3) of 2, and interconversion between 1 and 2.

Animals↗
PubMed2000

Global warming in the twenty-first century: an alternative scenario.

A common view is that the current global warming rate will continue or accelerate. But we argue that rapid warming in recent decades has been driven mainly by non-CO(2) greenhouse gases (GHGs), such as chlorofluorocarbons, CH(4), and N(2)O, not by the products of fossil fuel burning, CO(2) and aerosols, the positive and negative climate forcings of which are partially offsetting. The growth rate of non-CO(2) GHGs has declined in the past decade. If sources of CH(4) and O(3) precursors were reduced in the future, the change in climate forcing by non-CO(2) GHGs in the next 50 years could be near zero. Combined with a reduction of black carbon emissions and plausible success in slowing CO(2) emissions, this reduction of non-CO(2) GHGs could lead to a decline in the rate of global warming, reducing the danger of dramatic climate change. Such a focus on air pollution has practical benefits that unite the interests of developed and developing countries. However, assessment of ongoing and future climate change requires composition-specific long-term global monitoring of aerosol properties.

Aerosols↗
PubMed2000

Involvement of Rho-kinase-mediated phosphorylation of myosin light chain in enhancement of cerebral vasospasm.

Subarachnoid hemorrhage (SAH) often induces a long-term narrowing of the cerebral artery called cerebral vasospasm. Myosin light chain (MLC) in the spastic basilar artery was reported previously to be phosphorylated by Ca(2+)/calmodulin-dependent MLC kinase. Because Rho-kinase, which is activated by the small GTPase Rho, phosphorylates not only MLC but also myosin phosphatase at its myosin-binding subunit (MBS), thus inactivating myosin phosphatase, we examined whether Rho-kinase is involved in the development of vasospasm. Cerebral vasospasm was produced in the canine basilar artery by a 2-hemorrhage method, and vasocontractions were induced by topical application of 80 mmol/L KCl or 0.5 micromol/L serotonin to the canine basilar artery exposed transclivally. The phosphorylation of MLC in the basilar artery was increased concurrently with an enhancement in the intensity of vasospasm with the passage of time after SAH. In addition, Rho-kinase in the basilar artery was activated concurrently with an increase in the phosphorylation of MBS at Ser854 in vasospasm. The Rho-kinase activation levels in vasospasm on days 0 and 2 were comparable to those in KCl- and serotonin-induced sustained vasocontraction, respectively, and those in vasospasm on day 7 were markedly high. The topical application of Y-27632, a specific inhibitor of Rho-kinase, to the exposed spastic basilar artery on day 7 induced a dose-dependent dilation, and the intensities of vasospasm and the phosphorylation of MBS and MLC were simultaneously decreased by 10 micromol/L Y-27632, although the decrease in MBS phosphorylation was more marked than the decrease in MLC phosphorylation. These results indicate that the activation of Rho-kinase and the phosphorylation of MLC and MBS occur concomitantly during vasospasm induced by SAH and suggest that Rho-kinase is involved in the enhancement of cerebral vasospasm in addition to Ca(2+)/calmodulin-dependent MLC kinase by increasing the phosphorylation of MLC directly or indirectly as a result of the inhibition of myosin phosphatase by its phosphorylation.

Amides↗