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Biomedical subjects

S Uchida

Publications and source records attributed to S Uchida.

At least 379 records · Page 21Linked to original sources
PubMed1991

Polarized secretion of endothelin-1 and big ET-1 in MDCK cells is inhibited by cell Na+ flux and disrupted by NH4Cl.

We recently found that TGF-beta increases ET-1 secretion in MDCK, a renal tubular cell line. The secretion of ET-1, by a confluent monolayer of MDCK cells grown on a filter, to the basolateral side of the epithelium was two times greater than that to the apical side. However, TGF-beta-increased ET-1 and big ET-1 secretion were exclusively released to the basolateral side. We investigated the mechanism of polarized secretion of ET-1 and big ET-1 in MDCK cells. After 24 h of incubation with 80 pM TGF-beta, basolateral secretion of both ET-1 and big ET-1 increased two to threefold without a significant increase on the apical side. TGF-beta-stimulated ET-1 and big ET-1 secretion in the basolateral bath were inhibited when 10 microM amiloride (Na+ channel blocker) or 1 microM ouabain (Na+, K(+)-ATPase inhibitor) was added for 3 h. Polarized secretion of ET-1 and big ET-1 was not affected. In contrast, 10 mM NH4Cl or 0.2 mM chloroquine (both lysosomal function inhibitors) reduced TGF-beta-stimulated ET-1 secretion in the basolateral bath whereas big ET-1 secretion in the apical bath increased two times. Thus, the polarity of big ET-1 secretion was reversed. In addition, the conversion rate from big ET-1 to ET-1 was significantly decreased from 80 to 55% by inhibiting lysosomal function. Prepro-ET-1 mRNAs 3 h after these perturbations were virtually unaltered. Our data show that ET-1 and big ET-1 secretion may be regulated by cell Na+ flux and that lysosomal functions may play some roles in the conversion of big ET-1 to mature ET-1 and in polarized secretion of big ET-1. Translational or posttranslational regulation may play an additional role in ET-1 secretion as well as the mRNA level.

Ammonium Chloride↗
PubMed1991

Role of increased alpha 1-adrenergic activity in cardiomyopathic Syrian hamster.

We investigated serial changes in myocardial norepinephrine content and myocardial adrenergic receptors during the development of cardiomyopathy in Syrian hamsters (Bio 14.6) and their age-matched healthy controls. We also examined phosphatidylinositide hydrolysis after alpha 1-adrenergic stimulation and the effects of alpha 1-blockade. We found that in the prehypertrophic stage, myocardial norepinephrine content and densities of alpha 1- and beta-adrenergic receptors were significantly higher in the cardiomyopathic hamsters than in the controls. However, in the early heart failure stage, beta-receptor density was 28% lower than that of the age-matched controls, although alpha 1-receptor density remained 55% higher. Norepinephrine-stimulated phosphatidylinositide hydrolysis in the cardiomyopathic hamster in the hypertrophic stage was twice that in the controls, indicating that the increase in alpha 1-adrenergic receptors is coupled with the intracellular signal transduction. Furthermore, selective alpha 1-adrenoceptor blockade by bunazosin in the cardiomyopathic hamsters from 70 to 170 days of age reduced myocardial hypertrophy and focal myocardial necrosis. Thus we conclude that increased alpha 1-adrenergic activity plays an important role in progression of cardiac hypertrophy is cardiomyopathic Syrian hamsters.

Adrenergic alpha-Antagonists↗
PubMed1991

Renal Na-myo-inositol cotransporter mRNA expression in Xenopus oocytes: regulation by hypertonicity.

Canine renal cells in culture (MDCK cells) accumulate organic osmolytes, including myo-inositol (MI), in response to hypertonic stress. When medium tonicity is increased, intracellular concentration of MI rises because hypertonicity elicits increased uptake of MI via Na-MI cotransporter(s). To study the mechanism for this increase in cotransporter activity, poly(A)+ RNA isolated from MDCK cells maintained in hypertonic or isotonic medium was injected into Xenopus oocytes, and Na-dependent MI uptake was measured 3-5 days later. Poly(A)+ RNA from hypertonic cells induced clear expression of the cotransporter. In contrast, oocytes injected with poly(A)+ RNA isolated from MDCK cells maintained in isotonic medium exhibited cotransporter activity like oocytes injected with water. Upon size fractionation of RNA, peak activity appeared in a fraction that contained poly(A)+ RNA with median size of approximately 4 kilobases. Na-dependent MI uptake by poly(A)+ RNA-injected oocytes was inhibited by both phlorizin and phloretin. We suggest that hypertonicity-induced upregulation of the Na-MI cotransporter involves an increase in mRNA and synthesis of cotransporter protein(s).

Animals↗
PubMed1991

Myo-inositol and betaine transporters regulated by tonicity are basolateral in MDCK cells.

Myo-inositol and glycinebetaine are compatible osmolytes accumulated in the renal medulla and in MDCK cells cultured in hypertonic media. Both osmolytes are taken up by MDCK cells on Na-coupled transporters. The maximal velocity (Vmax) of both cotransporters is increased by culture in hypertonic medium. When hypertonic MDCK cells are shifted to isotonic medium there is a large transient efflux of osmolytes. To determine the polarity of the cotransporters and the transient efflux, we grew MDCK cells on a porous support to assay transport separately at their apical and basolateral surfaces. In hypertonic cells, basolateral uptake of both osmolytes was 1) more than 10-fold apical uptake, 2) greater than 96% Na dependent, 3) 25- (myo-inositol) and 16-fold (glycinebetaine) uptake in isotonic cells, reaching a maximum 24 h after the switch to hypertonic medium. When medium osmolarity was decreased from hypertonic to isotonic, myo-inositol uptake reversed to the isotonic level within 1 day; glycinebetaine uptake decreased more slowly. When medium osmolarity was decreased from hypertonic to isotonic, there was a large transient increase in basolateral efflux of both osmolytes.

Animals↗
PubMed1991

Endothelin 1 increases cell calcium in mouse collecting tubule cells.

Effects of endothelin 1 (ET-1) on intracellular free calcium concentration ([Ca2+]i) were examined in superfused single-nephron segments dissected from mouse kidney. ET-1, 10(-9) to 10(-6) M, caused a biphasic increase in [Ca2+]i consisting of an initial rapid rise followed by a second more sustained elevation in [Ca2+]i in cortical collecting tubules (CCT), outer medullary CT (OMCT), and inner medullary CT (IMCT). The magnitude of the response was dose dependent and was greater in CCT than in OMCT or IMCT. Additional studies using CCT revealed that Ca2+ removal from the superfusate resulted in attenuation of the second phase of [Ca2+]i with approximately 50% reduction in the height of the initial [Ca2+]i peak in response to 10(-6) M ET-1. Ca2+ channel blocker nicardipine had little effect on ET-1-evoked changes in [Ca2+]i. BAY K 8644 and high superfusate K+ also did not affect [Ca2+]i. Addition of ET-1 and arginine vasopressin (AVP), 10(-6) M each, showed the presence of homologous desensitization but the absence of heterologous desensitization in [Ca2+]i changes. There was no additive effect of ET-1 and AVP on [Ca2+]i when they were added together. These data show that ET-1 evokes a biphasic increase in [Ca2+]i of collecting tubules and suggest that the initial peak of the ET-1-evoked rise in [Ca2+]i is largely due to cell Ca2+ release and that the second sustained rise in [Ca2+]i is largely due to increased Ca2+ influx. Data also suggest that ET-1 and AVP may act in the collecting tubules through different receptors.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Disturbance of learning and memory by the alkylation of muscarinic acetylcholine receptors by propylbenzilylcholine mustard.

The effects of blockade of muscarinic acetylcholine receptors (mAChR) in rat cerebral cortex on learning and memory were studied by the use of passive and active avoidance tests. Injection of propylbenzilylcholine mustard (PrBCM) into frontal, parietal and occipital cortex decreased mAChR dose dependently, as assessed by 3H-quinuclidinylbenzilate binding studies. Bilateral injection of PrBCM into frontal and/or parietal but not occipital cortex impaired passive avoidance learning. The results suggest that intact muscarinic neurotransmission is important for registration and recall, but not retention phases of the learning and memory process. Alkylation of mAChR by PrBCM also caused impairment in the performance of active avoidance task.

Alkylation↗
PubMed1991

Taurine behaves as an osmolyte in Madin-Darby canine kidney cells. Protection by polarized, regulated transport of taurine.

Using a clonal growth assay, we demonstrated that taurine, a nonperturbing osmolyte accumulated in kidney medulla, brain, and some other tissues of hypertonic experimental animals can function as a nonperturbing osmolyte in Madin-Darby canine kidney (MDCK) cells. The taurine content of hypertonic MDCK cells is twice that of isotonic MDCK cells (isotonic 160 nmol/mg protein; hypertonic 320 nmol/mg protein). Therefore we studied taurine transport in MDCK cells grown on porous supports and then studied the effect of hypertonicity which is known to elicit increased uptake of some other nonperturbing osmolytes by MDCK cells. Basal uptake exceeded apical uptake, with Km and Vmax of 56 microM and 933 pmol/min.mg protein on the basal surface and 10 microM and 50 pmol/min.mg protein on the apical surface. On both surfaces, virtually all taurine uptake was Na+ and Cl- dependent. 24 h after cells were shifted to hypertonic medium (500 mosmol/kg), taurine uptake doubled on the basolateral surface without change on the apical surface. The response to hypertonicity was the result of an increase in Vmax without change in Km. There was no change in taurine efflux when cells were shifted from isotonic to hypertonic medium. When cells adapted to hypertonic medium were shifted to isotonic medium, a large transient basolateral efflux of taurine occurred within 10 min. We conclude that taurine can function as a nonperturbing osmolyte in MDCK cells and that tonicity-regulated taurine transport is a basolateral function in MDCK cells.

Animals↗
PubMed1991

Interaction between adenosine and beta-adrenoceptors.

Interaction between adenosine and isoproterenol (ISP) on myocardial inotropic action was studied in open-chest dog hearts. The local myocardial force and the left ventricular (LV) dP/dt were measured as indices of myocardial contractility. Isoproterenol [ISP, 9.47 microM (2 micrograms/ml)] was infused into the left circumflex coronary artery at rates of 0.05 ml/min (low dose ISP) or 0.2 ml/min (high dose ISP). Two mM adenosine or 0.5 mM N6-phenylisopropyl-adenosine (PIA) were infused into the coronary artery at rates of 0.2 (4 x 10(-7) mol/min), 0.5 (1 x 10(-6) mol/min) and 10 ml/min (2 x 10(-5) mol/min) in the presence of either a low or a high dose of ISP. Adenosine infusion at a rate of 0.2 ml/min did not modify myocardial contractility in the presence of the both doses of ISP. The larger doses of adenosine, 0.5 ml/min and 10 ml/min, decreased myocardial-developed tension and LVmax dP/dt dose-dependently. However, the dose of adenosine which affected myocardial contractility was inphysiologically high in comparison with the concentration in the ischemic myocardium. PIA, a potent agonist of adenosine A1-receptor, attenuated an increase in myocardial contractility in a dose-dependent manner which was caused by intracoronary ISP infusion. This indicates that A1-adenosine receptors exist, but a functional adenosine-catecholamine antagonism does not play a significant role in the canine left ventricle.

Adenosine↗
PubMed1991

[Serum concentration of hyaluronic acid in healthy populations and patients with rheumatoid arthritis--relationship to clinical disease activity of RA].

With the sandwich binding protein assay utilizing hyaluronic acid binding protein, we measured serum concentration of hyaluronic acid in 458 healthy persons, 71 patients with rheumatoid arthritis (RA) and 51 patients with various rheumatic diseases such as osteoarthritis (OA), progressive systemic sclerosis (PSS), systemic lupus erythematosus (SLE) and gout. The mean concentration +/- standard deviation (SD) of healthy persons whose age ranged 2 to 92 years old was 38.5 +/- 35.7ng/ml, and those with over 50 years old had apparently higher concentrations (51.9 +/- 40.5ng/ml) than those with below 50 of age (20.6 +/- 14.8ng/ml). When the upper limit of normal range was set up at 130 ng/ml, abnormal percentages were 62.0% (44/71) in RA, 0% (0/18) in OA, 6.3% (1/16) in PSS, 18.2% (2/11) in SLE and 0% (0/6) in gout. Patients who apparently had arthritis but not RA revealed normal or near to the upper limit in serum hyaluronic acid compared to RA patients having the mean +/- SD of 351.4 +/- 463.7ng/ml. When patients with RA were classified into stage I to IV with X ray of bone destruction, patients with more advanced X ray stage showed significantly higher serum concentrations of hyaluronic acid. Similarly, patients with lower activity of daily living revealed significantly higher serum concentrations of hyaluronic acid. In addition, serum hyaluronic acid level did correlate to concentration of serum CRP and sialic acid. Lansbury's index, strength of grip, joint score and erythrocyte sedimentation rate, but did not to duration of morning stiffness and titer of rheumatoid factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Arthritis, Rheumatoid↗
PubMed1990

Application of an interleukin 2 slow delivery system to the immunotherapy of established murine colon 26 adenocarcinoma liver metastases.

We evaluated the antitumor effect of an interleukin 2 (IL-2) slow delivery system, the IL-2 minipellet, using a murine hepatic metastasis model. The IL-2 minipellet consists of atelocollagen derived from natural bovine skin together with 1 x 10(6) units of recombinant IL-2. Administration of the IL-2 minipellet was performed into the spleens of BALB/c mice after translocation of the spleens to the s.c. position. Administration produced detectable serum IL-2 levels for 72 h. The IL-2 minipellet was evaluated for its efficacy against hepatic metastases from colon 26 adenocarcinoma in the BALB/c mice. Both the administration of the IL-2 minipellet alone and its combination with the injection of 5 x 10(7) lymphokine-activated killer cells resulted in significant reductions of the number of metastatic nodules. Moreover, increased survival of mice bearing colon 26 adenocarcinoma was noted in these two treatment groups. To investigate the mechanism of the IL-2 minipellet activity, we tested the lytic potential of splenocytes obtained after administration of the IL-2 minipellet in a 51Cr release assay. Cytotoxicity against YAC-1 cells and colon 26 cells was significantly augmented on Day 2 after minipellet administration. These results demonstrated that local administration of the IL-2 minipellet into the hepatic circulation was extremely effective against metastatic liver cancer.

Adenocarcinoma↗
PubMed1990

Disappearance in high-K+ medium of receptor-mediated inhibition of adenylate cyclase in guinea-pig cortical slices.

The muscarinic acetylcholine receptor-mediated inhibition of adenylate cyclase was studied in slices of guinea-pig cerebral cortex under normal and depolarizing conditions. Carbachol (1 mM) inhibited basal and isoproterenol (50 microM)-stimulated cyclic AMP (cAMP) accumulation by 20% and 25%, respectively, in normal Krebs-Ringer bicarbonate buffer solution (KRB). High-K+ medium (42 mM K+) increased cAMP accumulation to 330% of the basal level and abolished the inhibitory effect of carbachol. It also abolished the effect of morphine, an agonist of opioid receptors. Low-Ca2+ KRB or the presence of the Ca2+ channel blocker nifedipine, counteracted the effect of high K+ and restored the inhibitory effect of carbachol on the cAMP level. Pretreatment of slices with W-7 or trifluoperazine, two calmodulin antagonists, had the same effect as low Ca2+ or nifedipine on high-K(+)-stimulated cAMP accumulation and caused reappearance of the inhibitory effects of carbachol and morphine. On the contrary, H-7, an inhibitor of protein kinase C, and neomycin, an inhibitor of phospholipase C, had no significant effect on high-K(+)-induced phenomena and did not restore the effect of carbachol. These data suggest that the Ca2(+)-calmodulin system activated by membrane depolarization regulates the cAMP level directly and also by affecting the receptor-mediated process in nerve cells.

Acetylcholinesterase↗