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Biomedical subjects

M Hara

Publications and source records attributed to M Hara.

At least 235 records · Page 13Linked to original sources
PubMed1999

Mechanisms of tolerance induction after intrathymic islet injection: determination of the fate of alloreactive thymocytes.

BACKGROUND: Intrathymic (IT) administration of antigen when combined with peripheral T-cell depletion has been shown to induce operational tolerance in a wide range of experimental protocols. IT injection of pancreatic islets has been demonstrated not only to induce tolerance to alloantigen but also to prevent the development of autoimmune beta-cell destruction in models of type I diabetes. However, little is known about the mechanisms involved in tolerance induction after IT islet injection. METHODS AND RESULTS: A protocol for the induction of tolerance to fully allogeneic (C57BL/10; H2b) peripheral islet allografts was developed in CBA/Ca (H2k) recipients by the IT injection of allogeneic islets combined with depletion of peripheral CD4+ T cells. This protocol was based upon our own data and those of others showing that CD4+ T cells play a critical role in islet allograft rejection. Using this regimen, donor-type peripheral islet allografts survived indefinitely whereas third-party grafts were rejected. To determine the fate of alloreactive thymocytes that recognize donor major histocompatibility complex antigens via the direct pathway, T-cell receptor transgenic mice specific for the major histocompatibility complex class I molecule Kb (BM3 and DES) were used as recipients. IT injection of islets expressing the specific alloantigen Kb resulted in clonal deletion of alloreactive thymocytes in T-cell receptor transgenic recipients. No evidence of clonal inactivation in the residual peripheral alloreactive population was observed in this system. CONCLUSIONS: IT injection of allogeneic islets and concomitant CD4+ T-cell depletion is able to induce donor-specific unresponsiveness. One mechanism responsible for this unresponsiveness is the clonal deletion of thymocytes that recognize alloantigen via the direct pathway.

Animals↗
PubMed1999

Functional interaction between Oct-1 and retinoid X receptor.

The retinoid X receptor (RXR) is a member of the nuclear hormone receptor superfamily and heterodimerizes with a variety of other family members such as the thyroid hormone receptor (TR),1 retinoic acid receptor, vitamin D receptor, and peroxisome proliferator-activated receptor. Therefore, RXR is supposed to play a key role in a ligand-dependent regulation of gene transcription by nuclear receptors. In this study, we have identified the octamer-binding transcription factor-1 (Oct-1) as a novel interaction factor of RXR. In vitro pull-down assays using RXR deletion mutants showed that the interaction surfaces were located in the region encompassing the DNA binding domain (C domain) and the hinge domain (D domain) of RXR. We also showed that RXR interacted with the POU homeodomain but not with the POU-specific domain of Oct-1. Gel shift analysis revealed that Oct-1 reduced the binding of TR/RXR heterodimers to the thyroid hormone response element (TRE). In transient transfection assays using COS1 cells, Oct-1 repressed the T3-dependent transcriptional activity of TR/RXR heterodimers, consistent with in vitro DNA binding data; however, transcriptional activation by Gal4-TR(LBD) (LBD, ligand binding domain), which lacks its own DNA binding domain but retains responsiveness to T3, was not influenced by Oct-1. These results suggest that Oct-1 functionally interacts with RXR and negatively regulates the nuclear receptor signaling pathway by altering the DNA binding ability of the receptors.

Animals↗
PubMed1999

The visualization of T cell responses.

Transplanting allogeneic grafts is still significantly hampered by the rejection process, despite the use of powerful immunosuppressive agents. The T cell is recognized as playing a central role in the process of rejection, and it is believed that graft tolerance will ultimately be achieved by immunological manipulation of this cell (1, 2). As immunologists strive to define the role of the T cell in the fundamental processes of immunity and tolerance, new methods are emerging that will facilitate visualization of the T cells directly involved in the rejection response (3, 4). This overview addresses the visualization of T cell responses as made possible by these technological developments.

Humans↗
PubMed1999

Protein kinase C-beta activates tyrosinase by phosphorylating serine residues in its cytoplasmic domain.

We have previously shown that protein kinase C-beta (PKC-beta) is required for activation of tyrosinase (Park, H. Y., Russakovsky, V., Ohno, S., and Gilchrest, B. A. (1993) J. Biol. Chem. 268, 11742-11749), the rate-limiting enzyme in melanogenesis. We now examine its mechanism of activation in human melanocytes. In vivo phosphorylation experiments revealed that tyrosinase is phosphorylated through the PKC-dependent pathway and that introduction of PKC-beta into nonpigmented human melanoma cells lacking PKC-beta lead to the phosphorylation and activation of tyrosinase. Preincubation of intact melanosomes with purified active PKC-beta in vitro increased tyrosinase activity 3-fold. By immunoelectron microscopy, PKC-beta but not PKC-alpha was closely associated with tyrosinase on the outer surface of melanosomes. Western blot analysis confirmed the association of PKC-beta with melanosomes. Only the cytoplasmic (extra-melanosomal) domain of tyrosinase, which contains two serines but no threonines, was phosphorylated by the serine/threonine kinase PKC-beta. These two serines at positions 505 and 509 both are present in the C-terminal peptide generated by trypsin digestion of tyrosinase. Co-migration experiments comparing synthetic peptide standards of all three possible phosphorylated tryptic peptides, a diphosphopeptide and two monophosphopeptides, to tyrosinase-phosphorylated in intact melanocytes by PKC-beta and then subjected to trypsin digestion revealed that both serine residues are phosphorylated by PKC-beta. We conclude that PKC-beta activates tyrosinase directly by phosphorylating serine residues at positions 505 and 509 in the cytoplasmic domain of this melanosome-associated protein.

Animals↗
PubMed1999

Transient outward current, Ito1, is altered in cardiac memory.

BACKGROUND: Cardiac memory refers to an altered T-wave morphology induced by ventricular pacing or arrhythmias that persist for variable intervals after resumption of sinus rhythm. METHODS AND RESULTS: We induced long-term cardiac memory (LTM) in conscious dogs by pacing the ventricles at 120 bpm for 3 weeks. ECGs were recorded daily for 1 hour, during which time pacing was discontinued. At terminal study, the heart was removed and the electrophysiology of left ventricular epicardial myocytes was investigated. Control (C) and LTM ECG did not differ, except for T-wave amplitude, which decreased from 0.12+/-0.18 to -0.34+/-0.21 mV (+/-SEM, P<0.05), and T-wave vector, which shifted from -37+/-12 degrees to -143+/-4 degrees (P<0.05). Epicardial action potentials revealed loss of the notch and lengthening of duration at 20 days (both P<0.05). Calcium-insensitive transient outward current (Ito) was investigated by whole-cell patch clamp. No difference in capacitance was seen in C and LTM myocytes. Ito activated on membrane depolarization to -25+/-1 mV in C and -7+/-1 mV (P<0.05) in LTM myocytes, indicating a positive voltage shift of activation. Ito density was reduced in LTM myocytes, and a decreased mRNA level for Kv4.3 was observed. Recovery of Ito from inactivation was significantly prolonged: it was 531+/-80 ms (n=10) in LTM and 27+/-6 ms (n=9) in C (P<0.05) at -65 mV. CONCLUSIONS: Ito changes are associated with and can provide at least a partial explanation for action-potential and T-wave changes occurring with LTM.

4-Aminopyridine↗
PubMed1999

1,25-Dihydroxyvitamin D3 suppresses the expression of the VCAM-1 receptor, VLA-4 in human leukemic HL-60 cells.

Very late antigen-4 (VLA-4) is the complex with alpha4 and beta1 integrins, which is the receptors to fibronectin and VCAM-1. We evaluate the effect of 1,25(OH)2D3 on the expression of VLA-4 in human leukemic HL-60, U937 cells and human melanoma A375 cells. Flow cytometric analysis demonstrate that the expression of alpha4 integrin is negatively regulated in the cell lines we studied. The expression of beta1 integrin is also decreased in HL-60 and U937 cells. The mRNA expression of alpha4 integrin is significantly decreased by the treatment with 1,25(OH)2D3, whereas 1,25(OH)2D3 does not alter the expression of beta1 mRNA. The adhesion assay demonstrate that the number of adherent cells treated with 1, 25(OH)2D3 is significantly lower than that untreated on VCAM-1-coated wells. Because VCAM-1 is highly expressed in the endothelial cells, it is possible that 1,25(OH)2D3 prevents the attachment of the cells from the endothelial cells in vivo.

Antigens, CD↗
PubMed1999

Thiazolidinediones suppress endothelin-1 secretion from bovine vascular endothelial cells: a new possible role of PPARgamma on vascular endothelial function.

We examined the effect of troglitazone on immunoreactive endothelin-1 (ET-1) secretion from cultured bovine vascular endothelial cells (bVECs). Insulin (10(-9)-10(-7) M) stimulated ET-1 secretion in a dose-dependent fashion without any kinetic change. Troglitazone (1-20 microM) dose-dependently inhibited both spontaneous and insulin-stimulated ET-1 secretion. This inhibitory effect of troglitazone was associated with reduced ET-1 mRNA levels. Addition of indomethacin (100 microM) or Nw-nitro-l-arginine methyl ester (1 mM) and downregulation of protein kinase C by prolonged pretreatment of the cells with a phorbol ester, 12-O-tetradecanoylphorbol 13-acetate, did not affect the inhibitory effect of troglitazone at concentrations up to 10 microM. Troglitazone did not change the intracellular Ca2+ concentration stimulated by angiotensin II (10 microM). Other PPARgamma ligands, pioglitazone (1-10 microM) and 15-deoxy-delta 12, 14-prostaglandin J2 (1-10 microM), but not a PPARalpha ligand, bezafibrate (1-10 microM), dose-dependently suppressed spontaneous ET-1 secretion from bVECs. These results, taken together, suggest that troglitazone inhibits ET-1 mRNA expression and secretion in bVECs possibly through activation of PPARgamma. This inhibition may contribute to the hypotensive effect of troglitazone in insulin-resistant subjects.

Animals↗
PubMed1999

Continuous monitoring of cerebrospinal fluid acid-base balance and oxygen metabolism in patients with severe head injury: pathophysiology and treatments for cerebral acidosis and ischemia.

INTRODUCTION: Continuous monitoring of cerebral acid-base balance and oxygen metabolism has been introduced in neurointensive care settings. The hypothesis of this study utilizing multimodal neuromonitoring modalities is that hyperventilation and hypothermia improve cerebral acidosis through prevention of cerebral ischemia aggravation in patients with severe head injury. PATIENTS AND METHODS: Continuous monitoring of cerebrospinal fluid (CSF) pH, PCO2, HCO3-, base excess (BE), PO2, SO2, temperature, lactate and pyruvate (La and Py) measurements were conducted in 8 patients with severe head injury. Temperature-corrected CSF parameters were correlated with those in the jugular blood including oxygen saturation (SjO2), regional oxygen saturation (rSO2), intracranial pressure (ICP) and cerebral perfusion pressure (CPP), jugular blood temperature (Tjb), and endtidal PCO2 (PetCO2). Therapeutic significance of hyperventilation and hypothermia was evaluated. RESULTS: 1) CSF acidosis was observed in all cases (minimum pH 6.59-7.17) due to increased CSF PCO2 and/or decreased CSF HCO3- and tended to associate with abnormal ICP and/or CPP or ischemic episodes indicated by CSF PO2 and SO2, rSO2, and/or SjO2 during monitoring. 2) It was more obvious in CSF than in jugular blood that increased PCO2, La and Py, and/or decreased HCO3- resulted in decreased BE and pH. 3) Decreased CSF PO2 and SO2 only correlated with severe CSF acidosis. 4) Hyperventilation: Decreased PetCO2 did not always closely correlate with CSF PCO2 decrease and CSFpH increase. 5) Hypothermia: There were negative correlations of Tjb with CSF pH and SO2 in all cases, though correlation coefficients were not always high. CONCLUSIONS: CSF acidosis caused by increased CSF PCO2, La and Py, and/or decreased HCO3- tended to associate with abnormal ICP and CPP, and desaturation indicated by CSF SO2, rSO2, and/or SjO2. Hypothermia rather than hyperventilation tends to improve cerebral acidosis and ischemia.

Acidosis↗
PubMed1999

H2-blocker modulates heart rate variability.

The use of H2-blockers in the treatment of patients with peptic ulcer has become popular. However, this treatment has adverse cardiovascular effects. The aim of this study was to investigate proarrhythmic rhythm and autonomic nervous activity by analyzing heart rate variability in patients treated with omeprazole, ranitidine, and plaunotol. Nineteen patients (mean age 67.5 +/- 2.7 years) with active gastric ulcer were treated with omeprazole (20 mg/day) for 8 weeks, then ranitidine (300 mg/day) for the next 4 months, and finally plaunotol (240 mg/day). At each stage of the treatment, Holter electrocardiography was performed, and heart rate variability and arrhythmias analyzed. Heart rate variability yielded power in the low- (0.04-0.15 Hz) and high-frequency components (0.15-0.4 Hz). Although both ranitidine and omeprazole induced little change in cardiac rhythm, the high-frequency power was higher (10.3 +/- 0.8 vs 8.6 +/- 0.6 ms, P < 0.05) and the ratio of low-to-high frequency power was lower (1.41 +/-0.10 vs 1.59 +/- 0.09. P < 0.05) during ranitidine than during plaunotol treatment. Cosinor analysis of heart rate variability revealed a decreased amplitude of low-frequency power during omeprazole compared with during ranitidine and plaunotol treatment. Ranitidine modulated high-frequency power which may be related to the adverse cardiovascular effects of H2-blocker.

Aged↗
PubMed1999

The effects of cardiopulmonary bypass on postoperative oxygen metabolism.

The relationships between oxygen delivery (DO2), oxygen consumption (VO2), and the extraction rate (ER = VO2/DO2 x 100) in patients undergoing cardiopulmonary bypass (CPB) may differ from the normal physiologic state due to the oxygen debt acquired during CPB. Blood gas analysis and hemodynamic parameters were repeatedly measured for the determination of DO2 and VO2 in 40 patients undergoing CPB, every 8 h during the first 48 h postoperatively. As a control, 20 patients who had suffered acute myocardial infarction (AMI) were also studied using the same protocol. In the CPB group, a regression analysis showed that VO2 was significantly dependent on DO2, even within the physiologic range of DO2 (>500 ml/min per m2); VO2 = 121.4 + 0.0844 x DO2 (r = 0.254, P = 0.023). Conversely, in the AMI group, no such supply-dependent consumption was observed within the same range of DO2. At an ER of 30%, which is the optimal value in general, the DO2 of the CPB group was 575 ml/min per m2 and that of the AMI group was 493 ml/min per m2. All these results suggest that patients undergoing CPB need a much higher oxygen supply to recover from the oxygen debt acquired during open heart surgery.

Aged↗
PubMed1999

Nonfunctioning islet cell carcinoma of the pancreas: an evaluation of seven patients who underwent resection followed by long-term survival.

Islet cell carcinoma of the pancreas is a rare, indolent malignancy associated with a higher resectability rate and better survival than ductal carcinoma. This retrospective study presents the results of surgical treatment for nonfunctioning islet cell carcinoma of the pancreas in seven patients diagnosed and treated at Kurume University Hospital. There were two men and five women, with an average age of 54 years. Of the five tumors, four were located in the head of the pancreas, and the other three tumors were located in the body or tail of the pancreas. Epigastric pain was frequently the primary clinical symptom. By the time of diagnosis, four of the patients had regional disease, one of whom had lymph node and liver metastases, and one, liver metastases. Another patients was found to have lymph node metastases intraoperatively. Only one of the patients died of recurrent cancer, 21 years after the original operation. All of the patients who had liver metastases at the time of initial surgical treatment are now living at home. Thus, we conclude that nonfunctioning islet cell carcinomas are slow-growing tumors with a good prognosis if the main tumors and metastatic lesions are removed.

Adult↗
PubMed1999

Nesidioblastosis with hyperinsulinemic hypoglycemia in adults: report of two cases.

We report herein the cases of two women, aged 34 years and 39 years, respectively, found to have hyperinsulinemic hypoglycemia after presenting with a history of episodes of temporary loss of consciousness, nausea, and fainting. Under the suspected diagnosis of insulinoma, localization procedures were carried out, but no tumor was found. In both patients, a definite gradient in insulin concentration was found in the pancreas by percutaneous transhepatic or intraoperative portal venous sampling, and a misdiagnosis of insulinoma of the pancreatic body was made. During exploratory laparotomy no tumor was palpable in the pancreas, and intraoperative ultrasonography showed no low echoic mass in the pancreas. A distal pancreatectomy was performed in both patients, and histopathological examination of the resected specimens revealed graded slight hyperplasia of the islet cells.

Adult↗
PubMed1999

Left atrial myxoma associated with acute myocardial infarction.

We describe a patient with left atrial myxoma associated with acute myocardial infarction. Since hemodynamics were impaired even with the support of an intra-aortic balloon pump, the patient underwent removal of the tumor concomitant with coronary artery bypass grafting to the right coronary artery on the fifth day from infarction onset. In circumstances of life-threatening of myxoma associated with acute myocardial infarction, removal of myxoma with coronary artery bypass should be performed in an acute phase of myocardial infarction.

Aged↗
PubMed1999

Preparation of High Yields of Algal Protoplasts Using Buccal Juice of Sea Hare and Commercial Cellulase.

; Buccal juice of the sea hare Aplysia juliana was found to degrade algal polysaccharides. The optimal enzyme composition for protoplast preparation from Undaria pinnatifida was protein at 48 µg/ml buccal juice from sea hare, 10 mg/ml cellulase Onozuka-RS, 0.4 M NaCl, 0.8 M sorbitol, 2 mg/ml dextran sulfate sodium salt, and 1 µl/ml 2-mercaptoethanol in 10 mM MES buffer (pH 6.0). Protoplasts of Eisenia bicyclis, Endarachne binghamiae (Phaeophyta), and Ulva pertusa (Chlorophyta) could also be prepared in a similar manner. Yields of these protoplasts were about 10(7) cells per gram of fresh weight alga.

Journal Article↗