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Biomedical subjects

S Uchida

Publications and source records attributed to S Uchida.

At least 19 recordsLinked to original sources
PubMed1992

Detection of endothelin-1 mRNA by RT-PCR in isolated rat renal tubules.

A combination of reverse transcription and polymerase chain reaction was utilized to detect baseline endothelin-1 (ET-1) mRNA expressed in renal tubules dissected from rats. 5' and 3' primers were constructed according to human ET-1 genomic DNA. Rat ET-1 mRNA was found to be expressed only in cortical through medullary collecting ducts in addition to glomeruli. Sites for tubular synthesis of ET-1 corroborate well with major ET-1 binding sites along the nephron, indicating autocrine/paracrine role of ET-1 in the renal tubules and supporting a prevailing concept on such function of ET-1 in many differing tissues.

Animals↗
PubMed1992

Molecular cloning of the cDNA for an MDCK cell Na(+)- and Cl(-)-dependent taurine transporter that is regulated by hypertonicity.

Cells in the hypertonic renal medulla maintain their intracellular ion concentration at isotonic levels, despite much higher concentrations of extracellular electrolytes, by accumulating high concentrations of nonperturbing small organic solutes termed osmolytes. Taurine has been identified as a nonperturbing osmolyte in the renal medulla and Madin-Darby canine kidney (MDCK) cells. In hypertonic medium, the increased accumulation of taurine in MDCK cells is the result of increased activity of a Na(+)- and Cl(-)-dependent taurine transporter. We have isolated a cDNA encoding a Na(+)- and Cl(-)-dependent taurine transporter, whose sequence corresponds to a protein of 655 amino acids with significant amino acid sequence similarity to previously cloned Na(+)- and Cl(-)-dependent transporters, including the MDCK cell betaine/gamma-aminobutyric acid transporter and several brain neurotransmitter transporters. Northern hybridization indicates that mRNA for the taurine transporter is present in renal cortex and medulla, ileal mucosa, brain, liver, and heart. The abundance of mRNA for the taurine transporter is increased in MDCK cells cultured in hypertonic medium, suggesting that regulation of transport activity by medium hypertonicity occurs at the level of mRNA accumulation.

Amino Acid Sequence↗
PubMed1992

Cloning of the cDNa for a Na+/myo-inositol cotransporter, a hypertonicity stress protein.

Kidney medullary cells in situ, as well as kidney-derived Madin-Darby canine kidney (MDCK) cells accumulate nonperturbing, small organic solutes (osmolytes), including myo-inositol, when bathed in hypertonic media. Accumulation of osmolytes balances the osmolality of extracellular fluid without raising intracellular salts that would perturb cellular functions. In hypertonic media, increased myo-inositol accumulation is the result of increased activity of a Na+/myo-inositol cotransporter. We have isolated a cDNA encoding a Na+/myo-inositol cotransporter from MDCK cells using expression in Xenopus oocytes. The cDNA sequence predicts a protein of 718 amino acids with a significant amino acid sequence similarity to the Na+/D-glucose cotransporters of absorbing epithelia. Transporter mRNA is present in kidney and brain and is markedly induced in MDCK cells by medium hypertonicity, demonstrating that adaptation to hypertonic stress involves up-regulation of transporter mRNA accumulation.

Amino Acid Sequence↗
PubMed1992

Cloning of a Na(+)- and Cl(-)-dependent betaine transporter that is regulated by hypertonicity.

Many hypertonic bacteria, plants, marine animals, and the mammalian renal medulla are protected from the deleterious effects of high intracellular concentrations of electrolytes by accumulating high concentrations of the nonperturbing osmolyte betaine. When kidney-derived Madin-Darby canine kidney (MDCK) cells are cultured in hypertonic medium, they accumulate betaine to 1,000 times its medium concentration. This results from induction by hypertonicity of high rates of betaine transport into cells. We have isolated a cDNA (BGT-1) encoding a renal betaine transporter by screening an MDCK cell cDNA library for expression of a betaine transporter in Xenopus oocytes. The cDNA encodes a single protein of 614 amino acids, with an estimated molecular weight of 69 kDa. The deduced amino acid sequence exhibits highly significant sequence and topographic similarity to brain gamma-amino-n-butyric acid (GABA) and noradrenaline transporters, suggesting that the renal BGT-1 is a member of the brain GABA/noradrenaline transporter gene family. Expression in oocytes indicates that the BGT-1 protein has both betaine and GABA transport activities that are Cl(-)- as well as Na(+)-dependent and functionally similar to betaine and GABA transport in MDCK cells. Northern hybridization indicates that transporter mRNA is localized to the kidney medulla and is induced in MDCK cells by hypertonicity.

Amino Acid Sequence↗
PubMed1992

Papillary fibroelastoma in the left ventricular outflow tract.

We report a case of a papillary fibroelastoma originating from the left ventricular endocardium in the outflow tract which was discovered by echocardiography in an asymptomatic patient. Two echocardiographic features were observed: (1) the tumor surface was smooth, and characteristic papillary formation was not detected; and (2) the outline of the mass was clearly defined as a dense echo, with the central, radiolucent, portion surrounded by a highly refractive linear echo at the level of the maximum diameter of the mass. The excised tumor was covered with a gelatinous substance that masked multiple papillae on the surface, but its echolucent center could not be explained by the pathology of the tumor which was solid centrally. Our case indicates that a papillary fibroelastoma may sometimes show echocardiographic findings similar to those of a myxoma, although other investigators have not noted the smooth surface and the echolucent center makes it indistinguishable from a myxoma. Thus, in some cases, it is difficult to distinguish papillary fibroelastoma from myxoma by echocardiography.

Connective Tissue↗
PubMed1992

Radioprotective effects of (-)-epigallocatechin 3-O-gallate (green-tea tannin) in mice.

Long-term administration of (-)-epigallocatechin 3-O-gallate (EGCG) to mice through drinking water prevented radiation-induced increase of lipid peroxides in liver and significantly prolonged life span after lethal whole-body X-irradiation. The result indicates validity of this green-tea component as an orally active radio-protector of very low toxicity.

Animals↗
PubMed1992

Effects of ifenprodil on the N-methyl-D-aspartate receptor ionophore complex in rat brain.

The effects of a cerebral anti-ischemic drug ifenprodil on the receptor ionophore complex of an N-methyl-D-aspartate (NMDA)-sensitive subclass of central excitatory amino acid receptors were examined using [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10- imine (MK-801) binding in rat brain synaptic membrane preparations as a biochemical measure. The binding in membrane preparations not extensively washed was markedly inhibited not only by competitive NMDA antagonists such as (+/-)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic, D-2-amino-5-phosphonovaleric and D-2-amino-7-phosphonoheptanoic acids, but also by competitive antagonists at the strychnine-insensitive glycine (Gly) site including 7-chlorokynurenic acid and 6,7-dichloroquinoxaline-2,3-dione. Among several proposed ligands for alpha-adrenergic receptors tested, ifenprodil most potently inhibited the binding in these membrane preparations due to a decrease in the density of the binding sites without significantly affecting the affinity. Ifenprodil also inhibited the binding of [3H]N-[1-(2-thienyl)cyclohexyl]piperidine as well as of [3H]MK-801 to open NMDA channels in a concentration-dependent manner at concentrations above 10 nM in membrane preparations extensively washed but not treated by a detergent, with a Hill coefficient of less than unity. Further treatment of extensively washed membrane preparations with a low concentration of Triton X-100 resulted in an almost complete abolition of [3H]MK-801 binding, and the binding was restored to the level found in membrane preparations not extensively washed following the addition of both L-glutamic acid (Glu) and Gly. Ifenprodil was effective in inhibiting [3H]MK-801 binding via reducing both initial association and dissociation rates in Triton-treated membrane preparations, irrespective of the presence of Glu and Gly added. The binding in Triton-treated membrane preparations was additionally potentiated by the polyamine spermidine in a concentration-dependent manner at concentrations above 10 microM in the presence of both Glu and Gly at maximally effective concentrations. Ifenprodil invariably diminished the abilities of these three stimulants to potentiate [3H]MK-801 binding at concentrations over 1 microM in a manner that the maximal responses each were reduced. These results suggest that ifenprodil does not interfere with the NMDA receptor complex as a specific isosteric antagonist at the polyamine domain in contrast to the prevailing view.

Adrenergic alpha-Antagonists↗
PubMed1992

Autocrine secretion of transforming growth factor-beta in cultured rat mesangial cells.

Transforming growth factor-beta (TGF-beta) recently has been shown to modulate mesangial cell growth and to stimulate mesangial matrix synthesis by mesangial cells. Here we examined whether mesangial cells expressed TGF-beta mRNA and secreted mature TGF-beta, and we investigated the role of TGF-beta in mesangial cell growth. Cultured rat mesangial cells expressed 2.5 kb TGF-beta mRNA, and removal of fetal calf serum (FCS) for two days decreased the TGF-beta mRNA level, which was then stimulated by re-addition of 17% FCS reaching the maximum at nine hours. 12-O-tetradecanoyl phorbol-13-acetate (TPA), one of the phorbol esters, markedly increased the mRNA level and reached the maximum at six or nine hours. Immunoblot analysis of the conditioned media using specific anti-TGF-beta 1 antibodies revealed single 12.5 kDa proteins, the size compatible with mature TGF-beta subunits. By means of bioassay using CCL-64 cell line, TGF-beta production rate by mesangial cells was estimated to be 22.1 +/- 6.5 (mean +/- SD) ng/10(6) cells/24 hours, 96% of which was in latent forms. Exogenously added TGF-beta inhibited mesangial cell growth at 10 pM or higher. Moreover, addition of anti-TGF-beta neutralizing antibodies augmented mesangial cell growth, indicating that the secreted TGF-beta actually exerted a growth-inhibitory action. In summary, mesangial cells produce and secrete substantial amounts of TGF-beta but mostly in latent forms, and the secreted TGF-beta may regulate mesangial cell growth and differentiation. We conclude that TGF-beta may function as an autocrine factor in mesangial cells.

Animals↗
PubMed1992

Beta (20-28 Hz) and delta (0.3-3 Hz) EEGs oscillate reciprocally across NREM and REM sleep.

Across-night oscillations of beta (20-28 Hz) and delta (0.3-3 Hz) electroencephalograms (EEGs) were examined with spectral analysis in 10 normal young adult subjects (Ss). In each S, power densities of beta were found to oscillate reciprocally with delta power density across both nonrapid eye movement (NREM) and rapid eye movement (REM) sleep. Linear correlation coefficients between log power density of delta vs. beta were significant (p less than 0.0001) for each S. An incidental observation was that beta power within REM was reliably lower in epochs with more eye movement activity. The reciprocal relationship between beta and delta holds implications for sleep physiology and supplements our earlier finding that sigma (12-15 Hz) oscillates reciprocally with delta within NREM sleep. These descriptions of the continuously varying EEG across sleep provide information not available when EEG measures are tabulated by discrete NREM periods and REM periods.

Adolescent↗
PubMed1992

Different natures of supersensitivity of adenylate cyclase stimulated by calcitonin gene-related peptide and isoproterenol in rat diaphragm after denervation and reserpine treatment.

In skeletal muscles, calcitonin gene-related peptide (CGRP) released from motor nerve terminals and humoral catecholamines stimulate adenylate cyclase (AC) and enhance muscle contraction. The effects of denervation and treatment with reserpine on twitch contraction and the AC system in rat diaphragm were investigated. The basal levels of twitch contraction and AC activity of the diaphragm of rats were both increased 2 weeks after phrenic nerve denervation but were not altered by treatment with reserpine. Reserpine treatment provoked supersensitivity of AC to isoproterenol, without affecting the response to CGRP. On the other hand, denervation decreased the activation of AC and enhancement of twitch contraction by CGRP, without affecting the responses to isoproterenol. These data suggest that denervation causes up-regulation of AC as a result of loss of CGRP release from nerve terminal and that depletion of catecholamines by reserpine treatment supersensitizes the responses at the beta-adrenoceptor level. Thus, nervous and humoral factors regulate the AC system in striated muscle by different mechanisms.

Adenylyl Cyclases↗
PubMed1992

Intestinal anisakiasis: US in diagnosis.

Eighteen consecutive patients with intestinal anisakiasis were studied with high-resolution ultrasound (US) and barium studies. US showed markedly thickened bowel loops associated with luminal narrowing, swelling of Kerckring folds, and decreased peristalsis. A small amount of ascitic fluid around the bowel loops was found, and cytologic examinations of the ascites revealed a dense infiltration of eosinophils. Barium studies demonstrated segmental mucosal edema of the small intestine: The most common site was the distal ileum, and the mean length of the edematous lesion was 19 cm. All patients underwent treatment of symptoms without laparotomy, and their symptoms disappeared by the eighth day after onset. Patients with acute abdominal symptoms should be asked about the intake of raw or undercooked fish. If the above US features are found, the diagnosis of intestinal anisakiasis must be seriously considered to avoid unnecessary surgical treatment.

Adult↗
PubMed1992

Different pathways for Ca2+ influx and intracellular release of Ca2+ mediated by muscarinic receptors in ileal longitudinal smooth muscle.

Muscarinic receptor-mediated elevations in intracellular Ca2+ concentration ([Ca2+]i) in the longitudinal smooth muscle of guinea pig ileum were studied by the use of fura-2 fluorescence. Dose-response analysis indicated a difference in the potencies of carbachol (CCh) to increase [Ca2+]i in the presence and absence of extracellular Ca2+. For the increase in [Ca2+]i due to Ca2+ release from intracellular stores in the absence of extracellular Ca2+, the ED50 value of CCh was 3 x 10(-5) M. On the other hand, in the presence of Ca2+, the ED50 value was 2.5 x 10(-7) M, indicating that a low concentration of CCh (less than 10(-7) M) caused influx of extracellular Ca2+ without Ca2+ release. Oxotremorine and pilocarpine induced Ca2+ influx, but were less potent inducers of Ca2+ release. CCh also stimulated the formation of inositol trisphosphates (IP3) with an ED50 value of (4.5 x 10(-5) M), which was similar to that for Ca2+ release from intracellular stores. Treatment of the smooth muscle with neomycin (1 mM), a phospholipase C inhibitor, abolished both CCh-induced IP3 formation and Ca2+ release from intracellular stores, but did not affect CCh-induced Ca2+ influx. These results suggest that the pathway for muscarinic stimulation of Ca2+ influx through plasma membranes is different from that for Ca2+ release from intracellular stores, which seems to be coupled with IP3 formation.

Animals↗
PubMed1991

Demonstration of platelet activating factor receptor in guinea pig kidney.

Distribution of platelet activating factor (PAF) receptor was examined in the guinea pig kidney. Northern blot analysis showed a single band electrophoresed just below the 28S rRNA, and the mRNA was richest in the cortex with lesser amounts in the outer and then inner medulla. Scatchard analysis of membrane fraction using [3H]WEB 2086, a specific PAF receptor antagonist, revealed a single binding site with Bmax of 522, 228, 58 fmol/mg protein for the cortex, outer medulla and inner medulla, respectively. Kd values were in the same order of magnitude (10(-8) M). These results indicate the presence of a single class of PAF receptor in the guinea pig kidney which is most abundant in the cortex.

Animals↗
PubMed1991

Expression of Madin-Darby canine kidney cell Na(+)-and Cl(-)-dependent taurine transporter in Xenopus laevis oocytes.

Expression of a Madin-Darby canine kidney (MDCK) cell taurine transporter was examined in Xenopus oocytes that had been injected with poly(A)+ RNA extracted from MDCK cells. Compared with water-injected oocytes, injection of total poly(A)+ RNA resulted in an increase in Na(+)-dependent taurine uptake which was directly related to the amount of RNA injected. The magnitude of expression in poly(A)+ RNA-injected oocytes was 5-10-fold higher than that of water-injected oocytes. Since the Vmax of taurine uptake in MDCK cells is increased by culture in hypertonic medium, we compared oocyte taurine uptake after injection with poly(A)+ RNA from MDCK cells cultured in hypertonic medium with uptake in oocytes injected with poly(A)+ RNA from hypertonic cells elicited twice the taurine uptake elicited by poly(A)+ RNA from isotonic cells. The transporter expressed in oocytes was like that in MDCK cells: it was completely dependent on external sodium and was also anion dependent (Cl- greater than or equal to Br- greater than SCN- much greater than gluconate-). Other beta-amino acids, beta-alanine and hypotaurine, inhibited taurine uptake, but L-alanine and 2-(methylamino) isobutyric acid did not. The apparent Km of the transporter was 7.0 microM. After size fractionation on a sucrose density gradient, poly(A)+ RNA encoding for the MDCK taurine transporter was found in the fraction whose average size was 4.4 kilobases.

Animals↗
PubMed1991

Augmentation of antitumor effect on syngeneic murine solid tumors by an interleukin 2 slow delivery system, the IL-2 mini-pellet.

We evaluated the antitumor effect of an interleukin 2 (IL-2) slow delivery system, the IL-2 mini-pellet, in two murine solid tumor models, and also investigated the enhancement of its therapeutic effect by serial administration. The IL-2 mini-pellet contains 1 x 10(6) units of IL-2 and releases it slowly in vivo. In our experiment, the IL-2 mini-pellet was administered subcutaneously near the tumor site in combination with the intravenous injection of lymphokine-activated killer (LAK) cells. When this regimen was given on days 8 and 11 after the subcutaneous inoculation of Meth A fibrosarcoma into BALB/c mice, tumor growth was significantly inhibited (p less than 0.05) compared to tumor growth in untreated controls. Moreover, the IL-2 mini-pellet alone was also effective in inhibiting tumor growth. In another experiment, MH134 hepatoma was inoculated into C3H/He mice. Both administration of the IL-2 mini-pellet alone and in combination with LAK cells resulted in complete tumor regression in four of five mice. In a third experiment, serial administration of the IL-2 mini-pellet at 3- or 5-day intervals prolonged the suppression of Meth A fibrosarcoma growth in BALB/c mice. These results suggested that the IL-2 mini-pellet could be applied to cancer immunotherapy and that its antitumor effect could be prolonged by serial administration.

Animals↗
PubMed1991

Sigma (12-15 Hz) and delta (0.3-3 Hz) EEG oscillate reciprocally within NREM sleep.

Sleep EEG in the sigma and delta frequency bands was subjected to spectral analysis in 8 normal young adults. In each subject, power density of sigma and delta oscillated reciprocally during NREM sleep, confirming an observation made initially with period/amplitude analysis. In REM sleep, power density for both frequency bands was at its lowest levels. Correlation coefficients between power density of delta vs. 1/sigma for all artifact-free 20-s epochs of NREM sleep/night were highly significant for each subject. These results show that cyclic oscillation of EEG within sleep is not limited to delta frequencies. The reciprocal relation of sigma to delta holds implications for the EEG mechanisms of NREM sleep. This dynamic pattern may also prove useful for sleep stage scoring and for a finer empirical analysis of sleep in psychiatric and neurological disorders.

Activity Cycles↗