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T Nonaka

Publications and source records attributed to T Nonaka.

At least 91 records · Page 5Linked to original sources
PubMed1995

K+ self-exchange by the Na+ pump: regulation by P(i) and metabolic perturbations.

We have previously demonstrated that the Na(+)-K+ pump on the basolateral membrane of the rabbit cortical collecting duct can function in the K+/K+ exchange mode. Increasing intracellular phosphate in red blood cells inhibits the Na+ pump and increases K+/K+ exchange. We found that maneuvers designed to increase intracellular phosphate in collecting duct cells caused an increase in K+/K+ exchange. Subjecting the cells to a metabolic insult (cyanide) increased K+/K+ exchange by the pump as judged by its ouabain sensitivity and lack of electrogenic or conductive characteristics. The results demonstrate that the rate of K+/K+ exchange by the Na(+)-K+ pump can be altered by changes in intracellular phosphate over a range that is physiologically or pathologically achievable. The results also suggest a mechanism for inhibition of vectorial Na+ transport during metabolic stress.

Adenosine Diphosphate↗
PubMed1995

Observation of the internal configuration of rat incisor odontoblasts by scanning electron microscopy using the AODO method.

The internal configuration of rat incisor odontoblasts was studied mainly by scanning electron microscopy (SEM) using the AODO method (low concentration aldehyde prefixation, osmium tetroxide postfixation, dimethyl sulfoxide (DMSO) freeze-fracture, osmium tetroxide maceration). The present SEM findings were compared with the results obtained by conventional transmission electron microscopy (TEM) of epon-embedded specimens. The following results were obtained: 1) Functioning odontoblasts were characterized by a concentric, laminar rough endoplasmic reticulum (rER) with many long mitochondria interposed. 2) A network of tubular smooth endoplasmic reticulum (sER) was observed in the odontoblast process and distal portion of both functioning and resting odontoblasts. 3) The tubulo-vesicular elements which have been found to present a modified Golgi-GERL organelle with secretory and absorptive functions were demonstrated in both the functioning and resting odontoblasts. Structurally they consist of the sER network and strings of granules and vesicles. 4) Various types of cytoplasmic bodies, e.g., lysosomes, cytosomes and multivesicular bodies, related to the sER were also noted in both functioning and resting odontoblasts. 5) Microapocrine secretion of membranous vesicles of various sizes into the predentin and along the lateral branchings of odontoblast processes in the circumpulpal dentin was observed during the matrix apposition stage of the odontoblasts. The present morphological study revealed the three-dimensional configuration of the intra- and extra-cellular structures related to dentinogenesis by odontoblasts.

Aldehydes↗
PubMed1995

Effect of clenbuterol on sulfur dioxide-induced acute bronchitis in guinea pigs.

When guinea pigs were exposed to sulfur dioxide (SO2) gas (800 ppm, 2 h), they showed hyperresponsiveness to intravenously administered serotonin (5-hydroxytryptamine (5-HT)). This hyperresponsiveness continued for over 24 h after the exposure to the gas. The degeneration, desquamation of epithelium, and edema of the lamina propria of the trachea and bronchi were observed in animals after a 2-h exposure of SO2 histopathologically. These changes seemed to be the early phase of acute bronchitis. Then, we examined the effect of clenbuterol, a selective beta-2 adrenoceptor agonist, on the SO2-induced bronchial hyperresponsiveness in these animals. Orally administered clenbuterol (1-10 micrograms/kg) suppressed the hyperresponsiveness to 5-HT in a dose-dependent manner. These results suggest that clenbuterol might inhibit the hyperresponsiveness that accompanies acute bronchitis and that this agent may be useful for remission of broncho-spasm.

Acute Disease↗
PubMed1995

[A case report of the radical correction of a truncus arteriosus and peripheral pulmonary stenosis in association with Holt-Oram syndrome].

A one year and 6 months old female infant was admitted to our department for a radical correction of a truncus arteriosus (Collett-Edwards type II). She also had a peripheral pulmonary stenosis and Holt-Oram syndrome. Under a cardiopulmonary bypass with deep hypothermia, PFO was closed directly. First of all, the pulmonary arteries were dissected from the aorta, the defect of the aorta was closed directly and VSD was closed with Dacron fabric patch. The reconstruction of the pulmonary arteries were performed with valved conduit which consisted of Dacron graft and 14 mm Björk-Shily valve. The post-operative course was uneventful. Cardiac catheterization study, done 77 days after surgery, revealed 44 mmHg of pressure gradient between RV outflow tract and right PA. The patient was doing well and two years have passed since the surgery. She should be observed carefully at the out-patient clinic due to the mechanical valve and the presence of pressure gradient at RV outflow tract.

Blood Vessel Prosthesis↗
PubMed1995

Suppressive effect of clenbuterol on citric acid-induced cough reflex in guinea pigs.

We previously demonstrated that clenbuterol suppressed bronchial hyperresponsiveness in acute bronchitic models. However the effect of clenbuterol on the cough reflex, the main symptom of acute bronchitis, is not clear. The present study was thus undertaken to investigate the influence of clenbuterol on the cough reflex. Oral administration of clenbuterol (3 and 10 micrograms/kg) to guinea pigs markedly inhibited the increase in the respiratory resistance in response to 5-HT in a dose-dependent manner. At doses of 10 micrograms/kg and above, clenbuterol significantly inhibited the cough reflex induced by citric acid in guinea pigs. These doses are comparable with those causing broncho-dilation as described above, suggesting that the suppressive effect of clenbuterol on the cough reflex in guinea pigs may result from mainly its broncho-dilative action via stimulation of beta-2 adrenoceptors in airway smooth muscles however, other mechanisms cannot be ruled out. These results indicate that this agent may be useful for treatment of cough, the main symptom of acute bronchitis.

Airway Resistance↗
PubMed1994

Effects of alpha 2-plasmin inhibitor on plasminogen activation by staphylokinase/plasminogen complex.

Using a stable cross-linked SAK/plg complex, the effects of alpha 2-plasmin inhibitor on plasminogen activation by SAK were investigated. alpha 2-Plasmin inhibitor inhibited dose-dependently plasminogen activation by the SAK/plg complex. When FCB-2 or EACA was added to the reaction mixture of SAK/plg complex and alpha 2-plasmin inhibitor, the inhibitory activity of alpha 2-plasmin inhibitor was abolished and the enzymatic activity of the complexes was restored. alpha 2-Plasmin inhibitor inhibited the activity of the SK/plg complex, but neither FCB-2 nor EACA restored the plasminogen activator activity in the mixture of SK/plg complex and alpha 2-plasmin inhibitor. Using 125I-labeled SAK/plg complex or SK/plg complex, the reaction of the complex with alpha 2-plasmin inhibitor was analyzed. The SAK/plg complex produced a new complex with alpha 2-plasmin inhibitor. The formation of a new high molecular weight complex with alpha 2-plasmin inhibitor was abolished by both EACA or FCB-2. With regard to the SK/plg complex, neither EACA nor FCB-2 suppressed the complex formation with alpha 2-plasmin inhibitor. These findings indicate that the SAK/plg complex binds to fibrin, and that this complex expresses plasminogen activator activity without being affected by alpha 2-plasmin inhibitor.

Amino Acid Sequence↗
PubMed1994

Developing rat pineal cells manifest potential of neuronal differentiation in vitro.

The pineal gland in mammals is an endocrine organ and generally does not exhibit neuronal characteristics. However, it is known that under culture conditions, cells from newborn rat pineals express properties characteristic of photoreceptors. Here, we studied the potential of rat pineal cells to differentiate into neuronal cell types using different neural markers. Three phenotype markers characteristic of nerve cells, i.e., intense GABA, neuron-specific antigen (HPC-1) and microtubule-associated protein 2 (MAP2) immunoreactivities, were detected in the pineal culture of newborn rats. Expression of the respective neuronal phenotypes appears to be controlled by different mechanisms; in the normal culture medium containing 5.4 mM KCl, numerous cells were stained intensely with anti-GABA antiserum, whereas only a few were stained intensely either with HPC-1 or MAP2 antibody. In a culture medium with a high concentration of KCl (35 mM), which may induce depolarization of nerve cells, numerous cells became strongly positive for HPC-1 or MAP2; both the cell bodies and the neuritic fibers were stained positively. Since cells intensely immunoreactive to GABA, HPC-1 or MAP2 were not found in intact pineals of the rat, the present results indicate that the neuronal potency of the rat pineal cells is expressed only in vitro and is suppressed in vivo, and that the potency is lost during postnatal development. Norepinephrine at 1 microM, which suppresses differentiation of rhodopsin immunoreactive cells, was ineffective in inducing phenotypic expression of neuronal properties in the present system, indicating that the mechanism of suppression of neuronal properties in the intact pineal may be different from the one for photoreceptors.

Animals↗
PubMed1994

Metabolic support of Na+ transport by the rabbit CCD: analysis of the use of equivalent current.

The role of metabolism in the support of ion transport by the cortical collecting duct (CCD) is being increasingly recognized as a complex process involving energy supply to the Na+/K+ pump and maintenance of cellular conductive pathways. In order to assess both of these processes, we measured the metabolic support of Na+ transport using transepithelial electrical measurements and, in some cases, simultaneous determination of lumen-to-bath Na+ flux. Analysis of the calculated equivalent current (Ieq), the product of the transepithelial voltage and conductance, showed a predicted (and a measured) discrepancy between this value and the magnitude of active Na+ transport. Under conditions of this study, the change in Ieq in a single tubule was a reasonable index of the change in Na+ transport. The majority of the support of Na+ transport appears to come from oxidative metabolism. Glucose supports transport better than the other substrates tested, but lactate, pyruvate, and some acids provide near maximal support. We found some conditions where large changes in Na+ transport occurred without significant changes in conductance. Conductance could also be altered without producing major changes in transport. These results demonstrate complex and possibly independent influences of metabolism in the regulation of Na+ transport and cell conductive pathways.

Acids↗
PubMed1994

pH profile of kinetic constants of RNase Rh from Rhizopus niveus and its mutant enzymes towards UpU, and possible mechanisms of RNase Rh.

In order to elucidate the mechanism of action of Rhizopus niveus RNase Rh, we investigated the pH profiles of the kinetic parameters of RNase RNAP Rh, a derivative of RNase Rh, and its mutant enzymes, i.e., RNase RNAP Rh H104F, RNase RNAP Rh E105Q, and RNase RNAP Rh D51N. Based on comparisons of their profiles we concluded that protonation of His104 is indispensable for the enzymatic activity and Glu105 accelerates the enzymatic activity, especially at acid pH centered at pH 3.5. Based on these data and the previous data on the chemical modification and enzymatic properties of other mutant enzymes, we propose the following as a possible mechanisms of RNase Rh action. (i) His109 participates in enzymatic action as a general base catalyst which removes the hydrogen of the 2'-OH of the ribose moiety. (ii) His46 participates in the reaction as a general acid catalyst which interacts with the 5'-oxygen atom of the scissile phosphodiester bond and becomes a proton donor to the departing nucleoside or nucleotide. (iii) His104 interacts with phosphate anion and its protonation is favorable for the enzymatic activity. (iv) Since the protonated form of Glu105 is more favorable for activity, we postulate two possible roles for Glu105: (a) its stabilizes the intermediate, and (b) it interacts with the oxygen atom of P = O and polarizes the phosphorus atom.

Dinucleoside Phosphates↗
PubMed1993

Effect of bone resorbing factors on u-PA and its specific receptor in osteosarcoma cell line.

This study investigated the effect of bone resorbing factors on the pericellular fibrinolytic system of osteosarcoma NY cells. Parathyroid hormone (PTH), prostaglandin E2, (PGE2) or tumor necrosis factor alpha (TNF-alpha) enhanced the secretion of urokinase-type plasminogen activator (u-PA) antigen and suppressed the secretion of plasminogen activator inhibitor-1 (PAI-1) antigen to the conditioned medium. The former two factors also increased u-PA antigen in the cell surface. Transforming growth factor beta (TGF-beta) enhanced u-PA antigen, but its activity was suppressed due to the increased secretion of PAI-1. The binding assay of [125I]DFP-u-PA to NY cells revealed the presence of a single class of binding sites with a Kd of 5.51 nM and Bmax of 0.92 x 10(5) binding sites/cell. PTH or PGE2 increased Bmax 1.4-fold and enhanced the u-PA receptor (u-PAR) mRNA level 1.4-fold or 2.4-fold, respectively. However, TGF-beta did not alter either the Kd or u-PAR mRNA level. Thus, pericellular fibrinolytic activity by u-PA/u-PAR and PAI-1 is modulated by bone resorbing factors.

Bone Resorption↗
PubMed1993

Crystal structure of ribonuclease Ms (as a ribonuclease T1 homologue) complexed with a guanylyl-3',5'-cytidine analogue.

A ribonuclease T1 homologue, ribonuclease Ms (RNase Ms) from Aspergillus saitoi, has been crystallized as a complex with a substrate analogue GfpC where the 2'-hydroxyl (2'-OH) group of guanosine in guanylyl-3',5'-cytidine (GpC) is replaced by the 2'-fluorine (2'-F) atom to prevent transesterification. The crystal structure of the complex was solved at 1.8-A resolution to a final R-factor of 0.204. The role of His92 (RNase T1 numbering) as the general acid catalyst was confirmed. Of the two alternative candidates for a general base to abstract a proton from the 2'-OH group, His40 and Glu58 were found close to the 2'-F atom, making the decision between the two groups difficult. We then superposed the active site of the RNase Ms/GfpC complex with that of pancreatic ribonuclease S (RNase S) complexed with a substrate analogue UpcA, a phosphonate analogue of uridylyl-3',5'-adenosine (UpA), and found that His12 and His119 of RNase A almost exactly coincided with Glu58 and His92, respectively, of RNase Ms. Similar superposition with a prokaryotic microbial ribonuclease, RNase St [Nakamura, K. T., Iwahashi, K., Yamamoto, Y., Iitaka, Y., Yoshida, N., & Mitsui, Y. (1982) Nature 299, 564-566], also indicated Glu58 as a general base. Thus the present comparative geometrical studies consistently favor, albeit indirectly, the traditional as well as the most recent notion [Steyaert, J., Hallenga, K., Wyns, L., & Stanssens, P. (1990) Biochemistry 29, 9064-9072] that Glu58, rather than His40, must be the general base catalyst in the intact enzymes of the RNase T1 family.

Amino Acid Sequence↗
PubMed1993

Hepatitis C virus plus- and minus- strand RNA in hepatocellular carcinoma and adjoining nontumorous liver.

The presence of hepatitis C virus (HCV) RNA in serum and liver tissue was examined in seven patients with hepatocellular carcinoma (HCC), using the reverse transcriptase-polymerase chain reaction method with primers for the 5'-noncoding region. Plus-strand HCV-RNA was detected in the serum and liver tissue (both cancerous and noncancerous tissue) of all five patients who were positive for anti-HCV antibodies (C100-3 and P22) and was not detected in both of two patients who were negative for anti-HCV antibodies. Minus-strand HCV-RNA was only detected in the liver tissue (cancerous and noncancerous portion) of the five anti-HCV antibody-positive patients. The relative liver tissue content of minus-strand HCV-RNA ranged from 1 to 100 time less than that of plus strand HCV-RNA in cancerous and noncancerous tissue in each patient, respectively. There was no similar tendency in the HCV-RNA content between the cancerous and noncancerous portions of the liver in each patient. These results suggest that HCV exists and replicates in HCC tissue and may have some role in the development of HCC.

Alcoholism↗
PubMed1993

The capacity of central and peripheral catecholaminergic neurons to innervate the pineal organ and cerebral cortex of the rat: in vitro immunohistochemical observations.

The locus coeruleus (LC) or superior cervical ganglion (SCG) of neonatal rats were co-cultured either with the pineal organ or cerebral cortex (CX) to investigate the innervating capacity of central and peripheral catecholamine neurons under these experimental conditions. After 2 weeks of co-culturing, cultures were fixed for tyrosine hydroxylase (TH) immunohistochemistry to examine the distribution of catecholamine neurons and their fibers. Glial fibrillary acidic protein and fibronectin immunohistochemistry was performed to determine the cell types proliferating around the explants. In LC/CX co-cultures, numerous astrocytes spread between the two explants, and TH-immunoreactive neurites were generally seen to invade CX explants. In contrast, neurite extension from LC to pineal explants occurred only when a glial cell sheet grew between the two explants, and when the pineal explants were not surrounded by a tight fibronectin-positive cell layer. Neurites of the SCG usually invaded both CX and pineal explants, regardless of the existence of glial or non-glial cell layer. These results indicate that central and peripheral catecholamine neurites have the potential of invading both the cortex and pineal, although they are distributed only in particular regions of the intact brain. The distribution of LC neurites, however, seems to be profoundly affected by the cell types spreading around the explants; glial cells appear to support LC neurite extension, whereas non-glial cells appear to inhibit it.

Animals↗
PubMed1993

Present status of autoimmune hepatitis in Japan.

The clinical and biochemical features of patients with autoimmune hepatitis (AIH) in Japan during the 15-year period, 1975 to 1990, were evaluated by a nationwide survey using a questionnaire prepared by the Intractable Diseases Study Group organized by the Ministry of Health and Welfare. Data on a total of 866 cases with AIH were collected and analyzed, and of these, 632 cases underwent follow-up study. AIH was predominant in females, with a male:female ratio of approximately 2:19. Biochemical investigation on the occasion of the first examination showed abnormalities of liver function tests, including increased serum total bilirubin, transaminase activity and gamma-globulin levels. The main complications of autoimmune diseases were rheumatoid arthritis, Sjögren's syndrome and chronic thyroiditis. All patients with complications were female. Of 253 AIH patients, 50 were positive for anti-C100-3 antibody. ICG clearance and platelet count, which are stigmata of liver cirrhosis, were the main factors of prognostic importance in AIH. Therefore, early diagnosis prior to the development of liver cirrhosis is important to improve the prognosis of AIH.

Autoimmune Diseases↗
PubMed1993

Regulation of scu-PA secretion and u-PA receptor expression in osteoblast-like cells.

The production of proteolytic enzymes by osteoblasts is considered important for initiating osteoclastic bone resorption. Using the established cell line NY as an example of osteoblast-like cells, the effect of intracellular cyclic AMP (cAMP) and protein kinase C (PKC) on plasminogen activator secretion and its specific binding to the cells were investigated. HT-1080 cells were used as the control. NY cells predominantly secrete single-chain urokinase-type plasminogen activator (scu-PA) and some two-chain u-PA. Both scu-PA and u-PA were present in the cell surface and cell lysate of NY cells, and their distribution in HT-1080 cells was quite similar to that of NY cells. Exposing cells to phorbol myristate acetate (PMA) or dibutyryl cyclic AMP (db cAMP) enhanced the secretion of scu-PA and two-chain u-PA, whereas 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7) decreased scu-PA secretion, indicating that it is enhanced by protein kinase C (PKC) as well as by cAMP in NY cells. On the other hand, in HT-1080 cells, PMA decreased the level of two-chain u-PA secretion into the conditioned medium. The binding assay of 125I-DFP-u-PA to NY cells revealed the presence of a single class of binding sites with a Kd of 2.23 nM and Bmax of 0.82 x 10(6) binding sites/cell. PMA however, altered neither the Kd nor the Bmax. Dibutyryl cAMP increased the Bmax 1.9 fold. Thus, NY cells secrete u-PA and express specific binding sites on the cell surface, which are modulated by cAMP and PKC.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic AMP↗