Search PubMed⌕ Search

Biomedical subjects

S Miwa

Publications and source records attributed to S Miwa.

At least 91 records · Page 5Linked to original sources
PubMed1997

An endothelial receptor for oxidized low-density lipoprotein.

Endothelial dysfunction or activation elicited by oxidatively modified low-density lipoprotein (Ox-LDL) has been implicated in the pathogenesis of atherosclerosis, characterized by intimal thickening and lipid deposition in the arteries. Ox-LDL and its lipid constituents impair endothelial production of nitric oxide, and induce the endothelial expression of leukocyte adhesion molecules and smooth-muscle growth factors, which may be involved in atherogenesis. Vascular endothelial cells in culture and in vivo internalize and degrade Ox-LDL through a putative receptor-mediated pathway that does not involve macrophage scavenger receptors. Here we report the molecular cloning, using expression cloning strategy, of an Ox-LDL receptor from vascular endothelial cells. The cloned receptor is a membrane protein that belongs structurally to the C-type lectin family, and is expressed in vivo in vascular endothelium and vascular-rich organs.

Amino Acid Sequence↗
PubMed1997

Salmon thyroid-stimulating hormone: isolation, characterization, and development of a radioimmunoassay.

Coho salmon (Oncorhynchus kisutch) thyroid-stimulating hormone (TSH) was isolated by ethanol extraction of pituitary glands from mature coho salmon. Extraction was followed by gel-filtration chromatography on Sephadex G-100 superfine, anion-exchange chromatography on a Whatman DE-52 column, and finally by reverse-phase high-performance liquid chromatography. Fractions were monitored for TSH content by a homologous in vivo bioassay and by immunoblots using anti-human TSH beta-subunit antisera. In vivo treatment of coho salmon parr with coho salmon TSH caused a dose-dependent increase in plasma thyroxine level similar to that induced by bovine TSH. The N-terminal sequence (25 residues) of the salmon TSH beta subunit has 56% sequence identity to that of human TSH beta subunit and is identical to the deduced amino acid sequence of trout TSH beta subunit. The N-terminal sequence (25 residues) of the salmon TSH alpha subunit is identical to gonadotropin alpha-II subunit. Molecular sizes of the alpha and beta subunits are 18,000 and 24,000 daltons, respectively, as estimated by SDS-PAGE. Antiserum generated against salmon TSH, which was preadsorbed with alpha subunit using an alpha-subunit affinity column, detected only salmon TSH beta subunit by immunoblot and specifically stained thyrotropin-producing cells of the pituitary gland. A homologous radioimmunoassay (RIA) was developed using purified salmon TSH standard, iodinated TSH beta subunit, and antiserum generated against salmon TSH. Cross-reactivities of GTH I, GTH II, GTH I beta and GTH II beta subunits, alpha subunit, growth hormone, prolactin, and somatolactin were less than 1%. Displacement curves for serial dilutions of plasma and pituitary extracts of various salmonid species, as well as coho salmon pituitary cell culture medium, were parallel to the coho salmon TSH standards. In contrast, plasma of hypophysectomized juvenile coho salmon and pituitary extracts of Pacific tomcod (Microgadus proximus) did not displace bound radiolabeled salmon TSH. Finally, in vivo injection of juvenile coho salmon with triiodothyronine decreased plasma TSH levels, whereas the goitrogen, methimazole, increased plasma TSH levels. Injection of gonadotropin-releasing hormone agonist did not alter plasma TSH. These data suggest that the RIA is specific for TSH and confirm a negative-feedback relationship between the thyroid hormones and TSH.

Amino Acid Sequence↗
PubMed1997

Effect of different methods of internal thoracic artery harvest on pulmonary function.

BACKGROUND: In several clinical studies, internal thoracic artery (ITA) grafting for myocardial revascularization has been identified as increasing the risk of postoperative pulmonary complications. This study was designed to determine whether the technique used to harvest the ITA has an effect on postoperative pulmonary function. METHODS: Seventy-nine consecutive patients undergoing coronary artery bypass grafting using the left ITA were compared with patients undergoing coronary artery bypass grafting using saphenous vein grafts only. Two methods of ITA harvesting were used: (1) incision of the endothoracic fascia dissected off the ITA as a skeletonized vessel (group 1, n = 33) and (2) mobilization of the ITA as a wide musculofascial pedicle (group 2, n = 46). Thirty-two patients underwent coronary artery bypass grafting using saphenous vein grafts only (group 3). Pulmonary function tests were performed between postoperative days 20 and 30. RESULTS: The postoperative values of forced vital capacity were reduced in patients in all groups (p < 0.0001). The ratios of postoperative to preoperative forced vital capacity were 84% in group 1, 77% in group 2, and 84% in group 3. The reduction in group 2 was significant compared with group 1 (p < 0.05) and group 3 (p < 0.05). CONCLUSIONS: Postoperative pulmonary dysfunction was significantly greater in patients who underwent wide musculofascial pedicle dissection of the ITA compared with skeletonization of the artery. Thus, of the two techniques, the latter may be the method of choice with regard to lowering the incidence of postoperative pulmonary dysfunction.

Case-Control Studies↗
PubMed1997

Effect of anti-intercellular adhesion molecule-1 and anti-leukocyte function associated antigen-1 monoclonal antibodies on rat-to-mouse cardiac xenograft rejection.

BACKGROUND: The interaction between intercellular adhesion molecule-1 (ICAM-1) and its ligand, leukocyte function associated antigen-1 (LFA-1), is especially relevant in allograft rejection. We have previously shown that the simultaneous blockade of ICAM-1 and LFA-1 by monoclonal antibodies (mAbs) results in specific immunologic tolerance to cardiac allograft in a mouse model. METHODS: We evaluated the roles of these adhesion molecules in xenograft rejection by using a rat-to-mouse concordant xenograft model to identify critical molecules for immunosuppression. RESULTS: Lewis rat hearts transplanted into C3H/He mice were rejected within 5 to 7 days without treatment. A significant prolongation of xenograft survival (mean survival time, 11.6 days) was observed after treatment with anti-rat ICAM-1 and anti-mouse LFA-1 mAbs, when compared with nontreated mice or mice treated with different combinations of mAbs. Graft survival was prolonged in mice treated with FK506 (1 mg/kg/day), anti-rat ICAM-1, and anti-mouse LFA-1 mAbs (mean survival time, 22.2 days), whereas the same dose of FK506 alone was not effective. The mixed lymphocyte reaction showed that a combination of mAbs against mouse LFA-1-rat ICAM-1 and rat LFA-1-mouse ICAM-1 significantly inhibited the proliferation of mouse responders to rat stimulators and rat responders to mouse stimulators, respectively. Infiltration of mouse CD4 positive, mouse CD8 positive, and mouse LFA-1 positive cells, as well as dense deposition of mouse immunoglobulin G (IgG), IgM, and up-regulation of rat ICAM-1, on the graft endothelial cells were demonstrated by immunopathologic analysis of the rejected hearts. Flow cytometric analysis with rat spleen cells demonstrated the presence of xenoreactive antibodies (mouse IgG and IgM) in the recipient's serum. This xenoreactive antibody production was delayed but not inhibited by treatment of the recipients with anti-rat ICAM-1 and anti-mouse LFA-1. CONCLUSIONS: Blockade of the donor side ICAM-1 and the recipient side LFA-1 is critical for immunosuppression with anti-ICAM-1-LFA-1 treatment. Humoral factors may be responsible for xenograft rejection that occurs even after inhibition of the cell-mediated immune response by anti-ICAM-1 and anti-LFA-1 mAbs.

Animals↗
PubMed1997

The involvement of a novel mechanism distinct from the thrombin receptor in the vasocontraction induced by trypsin.

1. The vasocontracting effect of a serine protease trypsin and its mechanisms were investigated by monitoring the isometric tension in endothelium-denuded rings of rabbit thoracic aortae and its effects on intracellular free Ca2+ concentrations ([Ca2+]i) in dispersed rabbit vascular smooth muscle cells with a Ca2+ indicator fura-2. The actions of trypsin were compared with those of thrombin. 2. Both thrombin and trypsin reversibly contracted aortic rings without endothelium in a concentration-dependent manner. The vasocontraction induced by trypsin was well correlated with the protease activity of trypsin actually added to the tissue baths containing the aortic rings and was completely blocked by soybean trypsin inhibitor and phenylmethylsulphonyl fluoride (PMSF), a serine protease inhibitor. 3. The trypsin-induced contractions of the aortic rings were not the result of irreversible damage to vascular smooth muscle cells, since the contractile responses induced by noradrenaline or 30 mM KCl were unaffected by pretreatment with trypsin. 4. The contractions induced by either thrombin or trypsin were reduced to about 30% of control responses after removal of extracellular Ca2+, indicating that most of the contraction is dependent on extracellular Ca2+. By contrast, the contractions induced by either of the proteases were reduced by an antagonist of L-type voltage-operated Ca2+ channels, nifedipine, to about 70% of control responses, indicating that both nifedipine-sensitive and -resistant Ca2+ channels are involved in these contractions. 5. In the aortic rings precontracted by a maximally effective concentration of thrombin, the second application of thrombin virtually failed to induce contractions but trypsin could still induce contractions amounting to 10% of control values by it's protease activity. 6. After the first application of a maximal concentration of thrombin, the second application of thrombin could not induce an increase in [Ca2+]i, but an application of trypsin could still induce an increase in [Ca2+]i in dispersed rabbit vascular smooth muscle cells. 7. These data suggest that in addition to activation of a thrombin receptor, trypsin can contract rabbit aortae by a proteinase-activated receptor 2 or a novel mechanism.

Animals↗
PubMed1997

Inhibitory effect of nitrovasodilators and cyclic GMP on ET-1-activated Ca(2+)-permeable nonselective cation channel in rat aortic smooth muscle cells.

1. In single vascular smooth muscle cells (VSMCs) isolated from the aortae of male Wistar rats, we examined the effects of nitric oxide (NO) donors such as sodium nitroprusside (SNP) and S-nitroso-N-acetyl-DL-penicillamine (SNAP), and 8-bromo-guanosine-3':5'-cyclic monophosphate (8-bromo-cyclic GMP) on endothelin-1 (ET-1)-activated Ca(2+)-permeable nonselective cation channel by use of whole-cell recordings of patch-clamp technique and monitoring of intracellular free Ca(2+)-concentration ([Ca2+]i) with fura-2 real-time digital microfluorometry. 2. ET-1 evoked an initial transient peak and a subsequent sustained elevation in [Ca2+]i. After removal of extracellular Ca2+. ET-1 evoked only an initial transient peak without a sustained phase. Nifedipine (1 microM), a specific blocker of the L-type voltage-operated Ca2+ channel (VOC), reduced the sustained phase to about 40% of the control level. The remaining part of the sustained phase was abolished by 30 microM SK&F 96365, a blocker of nonselective cation channels. 3. The nifedipine-resistant sustained elevation in [Ca2+]i was abolished by 100 microM SNP, 10 microM SNAP and 300 microM 8-bromo-cyclic GMP. Neither SNP, SNAP nor 8-bromo-cyclic GMP significantly affected the basal level of [Ca2+]i. 4. In a VSMC clamped at a holding potential of -60 mV with K+ in the pipette solution replaced by Cs+, application of 10(-8) M ET-1 induced an inward current with an increase in baseline fluctuation. With fluctuation analysis, unit conductance of the ET-1-induced current was calculated to be about 21 pS. The ET-1-induced current was linearly related to the membrane potentials with its reversal potential of -5.5 mV. 5. The ET-1-induced current was reversibly and completely inhibited by 30 microM SK&F 96365 or 500 microM Cd2+. The current inhibited by SK&F 96365 or Cd2+ was linearly related to membrane potential with a reversal potential of about -5 mV. 6. The ET-1-induced current was reversibly and completely inhibited by 100 microM SNP, 10 microM SNAP and 300 microM 8-bromo-cyclic GMP. The current inhibited by SNP, SNAP or 8-bromo-cyclic GMP showed linear voltage-dependence and reversed at about -5 mV. 7. In a bath solution in which all cations were replaced by 30 mM Ca2+ and 100 mM nonpermeant cation N-methyl-D-glucamine (NMDG), ET-1 evoked a current with a reversal potential of -11 mV, from which PCa2+/Pcs1 was calculated to be 2.1. This Ca2+ current was also abolished by 100 microM SNP, 10 microM SNAP and 300 microM 8-bromo-cyclic GMP. The current inhibited by SNP, SNAP or 8-bromo-cyclic GMP showed linear voltage-dependence and reversed at about -11 mV. 8. These results taken together indicate that NO through a cyclic GMP signalling pathway inhibits ET-1-activated Ca(2+)-permeable nonselective cation channels, thereby suppressing the sustained increase in [Ca2+]i. Thus, the present study indicates that this Ca(2+)-permeable nonselective cation channel is an important target for nitrovasodilators.

Animals↗
PubMed1997

Physiological role of Ca2+-permeable nonselective cation channel in endothelin-1-induced contraction of rabbit aorta.

We previously showed a role for a nonselective cation channel (NSCC) in the ETA-dependent action of endothelin-1 in mouse fibroblast and rabbit aortic smooth-muscle cell. To clarify the physiological significance of NSCCs in endothelin-1 (ET-1)-induced vasocontraction, we examined the effects of NSCC blockers such as mefenamic acid and SK&F 96365 on the contractions of deendothelialized rabbit aortic rings induced by a low (10[-10] M) or high (10[-8] M) concentration of ET-1. Mefenamic acid (< or =10[-3] M) had little effect on the contraction induced by 45 x 10(-3) M K+ or 1 x 10(-6) M Bay K-8644 in combination with 15 x 10(-3) M K+, indicating that it does not affect voltage-operated calcium channels (VOCs) and contractile mechanisms. The contraction by a low concentration of ET-1 was abolished after removal of extracellular Ca2+, but it was reduced only to 50% by a maximally effective concentration (10[-5] M) of nifedipine, an inhibitor of L-type VOCs (L-VOC). Mefenamic acid and SK&F 96365 inhibited the ET-1-induced contraction with 50% inhibitory concentration (IC50) values of 10(-4) M and 2 x 10(-5) M, respectively, and abolished it at 10(-3) M and 10(-4) M. By contrast, nifedipine, mefenamic acid, or SK&F 96365 had little effect on the contraction by a high concentration of ET-1. The contraction induced by a low or high concentration of ET-1 was abolished by an ETA antagonist, BQ-123, but not by an ETB antagonist, BQ-788. These results demonstrate that the contraction induced by ET-1 is totally mediated exclusively by ETA, but that Ca2+ entry through NSCCs in addition to L-VOCs plays an important role in contractions induced by low concentrations of ET-1, whereas it plays only a minor role in contractions induced by high concentrations of ET-1.

Animals↗
PubMed1997

Primary cardiac chondrosarcoma--a case report.

We report a case of chondrosarcoma of the heart that was managed surgically. As chondrosarcoma of cardiac origin is extremely rare, this case is described with a brief comment.

Chondrosarcoma↗
PubMed1997

[A case of scheduled mitral valve replacement for mitral regurgitation caused by papillary muscle rupture after acute myocardial infarction].

Mitral regurgitation caused by papillary muscle rupture after acute myocardial infarction has poor prognosis, and it is the usual course for such cases in cardiogenic shock to be performed early mitral valve replacement. However, we recently experienced a case of successful scheduled mitral valve replacement for mitral regurgitation caused by rupture of the posterior papillary muscle after acute inferior myocardial infarction. The patient was a 63-year-old woman who admitted to a hospital with back pain and dyspnea and was diagnosed as pulmonary edema due to mitral regurgitation after acute myocardial infarction. She was treated with dopamine and diuretic agents effectively, but not weaned from these drugs. Then, she was transferred to our hospital. At the admission, she was in the NYHA class II due to mitral regurgitation and inferior myocardial infarction with papillary muscle rupture revealed by transesophageal echocardiography. Cardiac catheterization demonstrated total occlusion of the proximal right coronary artery (segment #2) and mitral regurgitation in Sellers III. The patient underwent a successful scheduled mitral valve replacement with SJM 27M concomitant with coronary artery bypass grafting 47 days after the onset of acute mitral regurgitation. There are few reports that successful surgical treatment for papillary muscle rupture was done more than 4 weeks after the onset of mitral regurgitation in Japan.

Female↗
PubMed1997

[Surgical treatment of infective endocarditis associated with cerebral mycotic aneurysm].

We experienced two cases of infective endocarditis associated with cerebral mycotic aneurysm. Case 1: 58 year-old man underwent emergency aortic and mitral valve replacement due to active infective endocarditis and congestive heart failure diagnosed by transesophageal echocardiography. After the operation, he did not wake up and his bilateral pupils were dilated. Computed tomography demonstrated massive intracranial hemorrhage and severe brain edema. He died from multiple organ failure 22th postoperative day. Rupture of cerebral mycotic aneurysm was strongly suspected. Case 2: 56 year-old man was admitted with severe headache and high grade fever. Computed tomography demonstrated intracranial hemorrhage. Cerebral mycotic aneurysm was detected at left distal middle cerebral artery by cerebral angiography. Infective endocarditis and mitral regurgitation were also diagnosed by echocardiography. He underwent cerebral mycotic aneurysmectomy after intensive antibiotics therapy, followed by successful mitral valve replacement. We review the literatures and discuss the problems of surgical management of infective endocarditis with cerebral mycotic aneurysm.

Aneurysm, Infected↗
PubMed1996

Molecular analysis of glucose phosphate isomerase deficiency associated with hereditary hemolytic anemia.

We report here two new cases of glucose phosphate isomerase (GPI) deficiency associated with hemolytic anemia and present the results of molecular analysis of the five Japanese GPI variants. A Japanese girl (GPI Fukuoka) had an episode of prolonged neonatal jaundice and at 3 years of age was admitted due to acute hemolytic crisis occurring with upper respiratory tract infection. Red blood cell (RBC) GPI activity was decreased to 11.8% of normal and the reduced glutathione (GSH) level of RBCs was slightly decreased. A 54-year-old Japanese man (GPI Iwate) was hospitalized due to chronic active hepatitis, and compensated hemolysis was noted. RBC GPI activity of the proband was decreased to 18.8%, and the GSH content was about half of the normal mean value. Sequencing of the reticulocyte GPIcDNA showed homozygous missense mutations 1028CAG-->CGG (343Gln-->Arg), 14ACC-->A7C (5Thr-->lle), 671ACG-->A7G (224Thr-->Met), and 1615GAC-->AAC (539Asp-->Asn) in GPI Narita, GPI Matsumoto, GPI Iwate, and GPI Fukuoka, respectively. We also identified GPI Kinki as a compound heterozygote of 1124ACA-->AGA(375Thr-->Arg)/ 1615GAC-->AAC(539Asp-->Asn). Our findings, together with the previous results of other investigators, showed that the GPI gene mutations so far identified were heterogeneous, although most GPI variants had common biochemical characteristics such as heat instability and normal kinetics. Several amino acid substitutions were identified in the proximity of the catalytically important amino acid residues such as Ser/Asp 159/160, Asp341, and Lys518, which have been identified in the structural analysis of the pig GPI. The molecular characterization of human GPI variants, therefore, may provide new insights into the genotype-phenotype correlation of GPI deficiency as well as the structure-function relationship of this enzyme.

Anemia, Hemolytic↗
PubMed1996

Stimulating effect of 6R-tetrahydrobiopterin on Ca2+ channels in neurons of rat dorsal motor nucleus of the vagus.

We have recently found that 6R-tetrahydrobiopterin (6R-BH4), a natural cofactor for aromatic L-amino acid hydroxylases and nitric oxide synthase, enhances dopamine release. Here, using a slice patch method, we examined the effect of 6R-BH4 on Ca2+ channels in neurons of rat dorsal motor nucleus of the vagus, where dopaminergic neurons are densely located. 6R-BH4 enhanced N-type Ca2+ channel currents, whereas 6S-BH4, a diastereoisomer of 6R-BH4, had little effect. Neither sodium nitroprusside, a nitric oxide generator, nor L-DOPA, a product of tyrosine hydroxylation, mimicked the effect of 6R-BH4. These findings suggest that 6R-BH4 enhances N-type Ca2+ channel currents in stereospecifically and independently of its cofactor activities as observed in its dopamine releasing action, and raise possibility that 6R-BH4 enhances dopamine release by activating Ca2+ channels.

Animals↗
PubMed1996

Three cases of hereditary nonspherocytic hemolytic anemia associated with red blood cell glutathione deficiency.

Three unrelated Japanese patients with chronic nonspherocytic hemolytic anemia wer found to have marked deficiency of red blood cell (RBC) reduced glutathoine (GSH) (4.4%, 13.1%, and 6.9% of normal, respectively). A panel of RBC enzyme assays showed that one patient had decreased glutathione synthetase activity and the other two were moderately deficient in gamma-glutamylcystine synthetase. Some family members of each patient showed mild deficiency of the respective enzymes. RBCs of these patients also showed a decreased level of glutathione-S-transferase as in previously described GSH-deficient cases. Hemolytic anemia was their only manifestation, and neither 5-oxoprolinemia nor 5-oxoprolinuria, which are usually associated with to generalized type of glutathione synthetase deficiency, was noted in our patients.

Adolescent↗
PubMed1996

Molecular basis of erythroenzymopathies associated with hereditary hemolytic anemia: tabulation of mutant enzymes.

Molecular abnormalities of erythroenzymopathies associated with hereditary hemolytic anemia have been determined by means of molecular biology. Pyruvate kinase (PK) deficiency is the most common and well-characterized enzyme deficiency in the glycolytic pathway, and it causes hereditary hemolytic anemia. To date, 47 gene mutations have been identified. We identified one base deletion, one splicing mutation, and six distinct missense mutations in 12 unrelated families with a homozygous PK deficiency. Mutations located near the substrate or fructose-1,6- diphosphate binding site may change the conformation of the active site, resulting in a drastic loss of activity and severe clinical symptoms. Glucose-6-phosphate dehydrogenase (G6PD)deficiency is the most common metabolic disorder, and it is associated with chronic hemolytic anemia and/or drug- or infection-induced acute hemolytic attack. An estimated 400 million people are affected worldwide. The mutations responsible for about 78 variants have been determined. Some have polymorphic frequencies in different populations. Most variants are produced by one or two nucleotide substitutions. Molecular studies have disclosed that most of the class 1 G6PD variants associated with chronic hemolysis have the mutations surrounding either the substrate or the NADP binding site. Among rare enzymopathies, missense mutations have been determined in deficiencies of glucosephosphate isomerase, (TPI), phosphoglycerate kinase, and adenylate kinase. Compound heterozygosity with missense mutation and base deletion has been determined in deficiencies of hexokinase and diphosphoglyceromutase. Compound heterozygosity with missense and nonsense mutations has been identified in TPI deficiency. One base junction mutations resulting in abnormally spliced PFK-M mRNA have been identified in homozygous PFK deficiency. An exception is hemolytic anemia due to increased adenosine deaminase activity. The basic abnormality appears to result from the overproduction of a structurally normal enzyme.

Anemia, Hemolytic↗
PubMed1996

Endothelin-1-induced mitogenic responses of Chinese hamster ovary cells expressing human endothelinA: the role of a wortmannin-sensitive signaling pathway.

In the current study, endothelin-1 (ET-1) worked as a mitogen on Chinese hamster ovary cells stably expressing human endothelinA; when applied to serum-deprived cells, ET-1 caused dose-dependent increase in [3H]thymidine incorporation and cell proliferation. No synergism was observed between the effect of ET-1 and that of insulin-like growth factor-1/basic fibroblast growth factor. Both the inhibition of intracellular Ca2+ response by phospholipase C inhibitor U73122 and the down-regulation of protein kinase C (PKC) by pretreatment with phorbol 12-myristate-13-acetate (PMA) partially blocked the ET-1-induced mitogenic responses. Wortmannin, a phosphatidylinositol-3-kinase inhibitor, caused dose-dependent inhibition of the ET-1-induced mitogenic responses in both PMA-treated and -untreated cells. Wortmannin also inhibited ET-1-induced increase in phosphatidylinositol trisphosphate formation and activation of mitogen-activated protein kinase (MAPK), whereas it failed to inhibit PMA-induced activation of MAPK. In accordance with its effect on MAPK activation, wortmannin inhibited ET-1-induced activation of Raf-B, whereas it failed to inhibit the effect of PMA. These results suggested the role of a Ca2+/PKC-independent, wortmannin-sensitive signaling pathway that linked ETA and MAPK cascade in the mitogenic signaling activated by ETA.

Amino Acid Sequence↗