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Y Uezono

Publications and source records attributed to Y Uezono.

At least 55 records · Page 3Linked to original sources
PubMed1996

Adrenomedullin-sensitive receptors are preferentially expressed in cultured rat mesangial cells.

By using cultured rat mesangial cells, we compared the effects on cyclic nucleotide levels of adrenomedullin with those of the structurally related peptides, calcitonin gene-related peptide (CGRP) and amylin. Adrenomedullin potently increased cAMP levels 7-fold in a time- and concentration-dependent manner. Its EC50 was 3 x 10(-9) M. CGRP was less potent (2-fold) with an EC50 of 10(-7) M, and amylin had no effect on cAMP levels. All three peptides failed to increase cGMP levels. Treatment of cells with near maximal concentrations of adrenomedullin (10(-7) M) and CGRP (10(-6) M) had no additive effect on cAMP levels. Human adrenomedullin-(22-52)-NH2, a putative adrenomedullin receptor antagonist, inhibited the production of cAMP elicited by adrenomedullin (IC50: 7 x 10(-8) M) and CGRP (IC50: 5 x 10(-8) M). Human CGRP-(8-37), a CGRP receptor antagonist, conversely, reduced the cAMP elevation caused by these peptides with a lower potency (IC50: 10(-6) M for both peptides). This demonstrated that human adrenomedullin-(22-52)-NH2 was a more effective antagonist for adrenomedullin- and CGRP-specific receptors than human CGRP-(8-37). Results suggest that receptors sensitive to adrenomedullin are preferentially expressed in cultured rat mesangial cells. Immunohistochemical study showed almost no immunoreactive adrenomedullin and CGRP, if any, in the cells. Adrenomedullin may regulate mesangial function as either a paracrine or circulating hormone via a cAMP- but not a cGMP-dependent mechanism.

Adrenomedullin↗
PubMed1996

Proadrenomedullin N-terminal 20 peptide (PAMP) reduces inward currents and Ca2+ rises induced by nicotine in bovine adrenal medullary cells.

It has been recently reported that proadrenomedullin N-terminal 20 peptide (PAMP), which is secreted with adrenomedullin and catecholamines from the adrenal medulla, inhibits catecholamine release stimulated with nicotine. In the present study, to elucidate anticholinergic mechanisms of PAMP we employed the whole-cell patch-clamp and the intracellular Ca2+ imaging techniques in cultured bovine adrenal medullary cells. PAMP inhibited nicotinic currents and [Ca2+]i rises induced by nicotine in a dose-dependent manner (10(-9)-10(6) M). These inhibitions were selective, since PAMP alone did not induce any ionic currents, moreover it did not affect voltage-dependent Ba2+ currents or high K+ (50 mM)-induced [Ca2+]i rises. The onset of the inhibitory effect of PAMP (10(-6) M) was very rapid and reached a steady-state level within 10 sec. The effect of PAMP (10(-6) M) lasted for about 10-15 min. Desensitization process of the nicotinic current fitted to a single exponential function with a time constant of 6.4 +/- 0.3 sec. When PAMP (10(-6) M) simultaneously added with nicotine (10(-5) M), the desensitization process was facilitated and fitted to two exponentials with time constants of 0.46 +/- 0.08 and 2.5 +/- 0.8 sec. From the present results, the inhibition by PAMP of nicotinic currents which was well associated with that of nicotine induced [Ca2+]i rises leads to the attenuation of catecholamine release probably, at least in part, due to the facilitation of the desensitization process of the nicotinic currents.

Adrenal Medulla↗
PubMed1996

Purification and properties of extracellular glucosyltransferase from Streptococcus bovis.

Eight Streptococcus bovis strains were classified into 3 types on the basis of isoelectric point (pI) and molecular mass (M(r)) of extracellular glucosyltransferase. Strains ATCC 9809, 35034 and 43143 produced glucosyltransferase of pI 3.7 and M(r) 165 kDa; strains ATCC 15351, 27960 and 33317 produced glucosyltransferase of pI 4.1 and M(r) 140 kDa; strains ATCC 43085 and 43144 did not produce any glucosyltransferase. The glucosyltransferase form S. bovis 9809 was purified by Bio-Gel hydroxyapatite chromatography and DEAE-Toyopearl chromatography. The S. bovis 9809 glucosyltransferase was immunologically identical with the other 5 S. bovis glucosyltransferases and not related to mutants streptococcal glucosyltransferases. The specific activity, the optimum pH and the Km value for sucrose were 17.9 U/mg protein, 6.0 and 5.0 mM, respectively. The first 11 N-terminal amino acid residues of the glucosyltransferases were DETSAVTLTRE, and the region was hydrophilic. The glucosyltransferases from S. bovis 9809 and 3317 synthesized from sucrose 1, 6-alpha-D-glucan with 9 and 2 mol%, 1, 3, 6-alpha-branched glucose, respectively.

Amino Acid Sequence↗
PubMed1995

Adrenomedullin increases cyclic AMP more potently than CGRP and amylin in rat renal tubular basolateral membranes.

In rat renal tubular basolateral membranes, the potency to increase cAMP of adrenomedullin (AM), a novel vasorelaxant peptide originally isolated from human pheochromocytoma, was compared with those of calcitonin gene-related peptide (CGRP) and amylin. Although all three peptides raised cAMP in a time- and concentration-dependent manner with a 4-fold increase at 10(-6)-10(-5) M, the EC50 value (10(-9) M) of AM was 100-fold smaller than those of CGRP and amylin. CGRP[8-37], an antagonist for CGRP receptors, attenuated cAMP elevation induced by these peptides with the essentially similar concentration-inhibition curves. These results suggest that the receptors for AM, CGRP and amylin share a common structural homology, and that the receptors sensitive to AM are preferentially expressed in renal tubular basolateral membranes.

Adrenomedullin↗
PubMed1994

Pituitary adenylate cyclase-activating polypeptides (PACAPs) increase cAMP in rat cerebral microvessels.

Effect of PACAP on cAMP level in the rat cerebral microvessels was investigated. The cerebral microvessels were prepared from rat cerebral cortex by albumin flotation and glass beads filtration technique. When the microvessels were incubated with PACAP 27, PACAP 38 and VIP, cAMP in the microvessels was increased rapidly reaching a plateau value within 60 s. PACAP 27, PACAP 38 and VIP increased cAMP level in a dose-dependent manner with EC50 values of 4.7, 7.0 and 34 nM, respectively. These results suggest that PACAPs play a role in the regulation of the cerebral microvessel function.

Animals↗
PubMed1994

Stimulatory effect of IL-1 beta on catecholamine secretion from cultured bovine adrenal medullary cells.

We investigated the effect of recombinant human interleukin-1 beta (IL-1 beta) on catecholamine secretion from cultured bovine adrenal medullary cells. Treatment of cultured cells with IL-1 beta (10 ng/ml) for 24 hr caused an increase in accumulation of catecholamines in the cultured medium. The accumulation of catecholamines stimulated by IL-1 beta was observed in time (4-48 hr)- and concentration (3-30 ng/ml)-dependent manners. The stimulatory effect of IL-1 beta (10 ng/ml) was completely inhibited by recombinant human IL-1 receptor antagonist (1 microgram/ml). IL-1 beta had little effect on [3H]norepinephrine uptake to cultured cells. These results suggest that IL-1 beta stimulates catecholamine secretion through activation of IL-1 receptors in adrenal medullary cells.

Adrenal Medulla↗
PubMed1994

Glucose, fructose, mannose and/or glucose-1-phosphate-releasing activity stains for glycosidases and glycosyltransferases in gels after isoelectric focusing.

beta-Fructofuranosidase, alpha-glucosidase, beta-glucosidase, alpha-mannosidase, beta-mannosidase, sucrose phosphorylase, glucosyltransferase and fructosyltransferase were separated by isoelectric focusing and sensitively detected to be slightly diffuse and insoluble spots in thin-layer gels, supported by a glass plate, by release of monosugars or a sugar phosphate, followed by conversion to glucose-6-phosphate (G6P) and then by reduction of NADP+ to NADPH, terminated by the formation of reduced Nitroblue Tetrazolium (NBT). Approximately 1-10 mU of enzyme was focused and the gel, after washing with a buffer, was partially dried and directly stained by uniformly spreading on the gel surface a staining medium containing sucrose or nitrophenyl glycosides as substrates, intermediary enzymes such as hexokinase, mutase and/or isomerase, NADP+, ATP, Mg+, phenazine methosulfate (PMS) and NBT. Specific staining procedures for each of these activities, on sucrose or on the glycosides as substrates, and staining procedures for multiple activities are described, with the conditions necessary for optimal development.

Fructose↗
PubMed1993

Receptors that couple to 2 classes of G proteins increase cAMP and activate CFTR expressed in Xenopus oocytes.

The cystic fibrosis transmembrane conductance regulator (CFTR), a Cl- channel activated by phosphorylation, was expressed in Xenopus oocytes along with various combinations of several other components of the cAMP signalling pathway. Activation of the coexpressed beta 2 adrenergic receptor increased cAMP and led to CFTR activation. The activation of CFTR (1) requires only short (15 s) exposure to isoproterenol, (2) occurs for agonist concentrations 100-1000 fold lower than those that produce cAMP increases detectable by a radioimmunoassay, (3) requires injection of only 5 pg of receptor cRNA per oocyte, and (4) can be increased further by coexpression of cRNA for adenylyl cyclase type II or III or for Gs alpha. In addition, CFTR activation and cAMP increases by beta 2 activation were enhanced by activation of the coexpressed 5HT1A receptor, which is thought to couple to Gi. The additional activation by the 5HT1A receptor was enhanced by coexpression of adenylyl cyclase type II but not with type III and may proceed via the beta gamma subunits of a G protein. The sensitivity of the assay system is also demonstrated by responses to vasoactive intestinal peptide and to pituitary adenylate cyclase-activating polypeptide in oocytes injected with cerebral cortex mRNA.

Adenylyl Cyclases↗
PubMed1992

Veratridine causes the Ca(2+)-dependent increase in diacylglycerol formation and translocation of protein kinase C to membranes in cultured bovine adrenal medullary cells.

Our previous studies suggested that protein kinase C is involved in the veratridine (an activator of voltage-dependent Na+ channels)-induced phosphorylation and activation of tyrosine hydroxylase as well as the synthesis of catecholamines in adrenal medulla (Uezono et al. 1989). In the present study, we investigated whether treatment of cultured bovine adrenal medullary cells with veratridine causes the accumulation of diacylglycerol, a physiological activator of protein kinase C and the translocation of protein kinase C from cytosol to membrane, a process required for protein kinase C activation. Veratridine (100 mumol/l) increased diacylglycerol level about 2.2 fold in a monophasic manner, with peaking at 5 min and declining toward the basal level within 20 min. Veratridine also increased membrane protein kinase C from 15.6% to 26.9% of total protein kinase C in a time-course similar to that of diacylglycerol accumulation. Both stimulatory effects of veratridine were inhibited by tetrodotoxin and not observed in Ca(2+)-free, EGTA-containing medium. Amiloride, an inhibitor of Na+/Ca2+ and Na+/H+ exchange, did not alter veratridine-induced events. These results suggest that veratridine-induced Ca2+ influx contributes to the accumulation of diacylglycerol and the activation of protein kinase C in adrenal medullary cells.

Adrenal Medulla↗
PubMed1992

Cooperative modulation of voltage-dependent sodium channels by brevetoxin and classical neurotoxins in cultured bovine adrenal medullary cells.

The effects of Ptychodiscus brevis toxin (PbTx-3) on 22Na influx, 45Ca influx and catecholamine secretion were examined in cultured bovine adrenal medullary cells and compared with the effects of classical neurotoxins. PbTx-3 alone had no effects, but greatly enhanced veratridine (30 microM)-induced Na influx, Ca influx and secretion, with a EC50 of 30, 25 and 23 nM, respectively. PbTx-3 (1 microM) reduced EC50 values of veratridine approximately 3-fold and increased the maximal responses caused by saturating concentration (300 microM) of veratridine approximately 1.3 fold. alpha- and beta-Scorpion venom shifted the concentration-response curves of veratridine to the left without altering maximal responses. PbTx-3 in combination with either alpha- or beta-scorpion venom showed only additive effects on Na influx, but augmented veratridine (30 microM)-induced Na influx to a greater extent than PbTx-3, alpha- or beta-scorpion venom alone. Na influx due to these toxins was abolished by 1 microM saxitoxin. Our results suggest that Na channels in adrenal medullary cells have neurotoxin receptors for brevetoxin that allosterically stimulate Na influx initiated by veratridine, leading to increased Ca influx and catecholamine secretion. Allosteric interactions do not exist between brevetoxin and alpha-scorpion venom, or between brevetoxin and beta-scorpion venom, but once Na channels are gated by veratridine, these toxins cooperatively augment Na influx.

Adrenal Medulla↗
PubMed1991

Protein kinase C in human pheochromocytoma.

Subtypes of protein kinase C were analyzed in adrenal and extra-adrenal pheochromocytoma of humans. Almost all protein kinase C of the adrenal tumor was type III, while the enzyme of the extra-adrenal tumor was separated into two major fractions corresponding to type II and type III by hydroxyapatite column chromatography. The extra-adrenal tumor but not the adrenal tumor spontaneously produced neurite-like processes when the cells were cultured in vitro. These results suggest that the high proportion of type II enzyme may reflect neuron-directed differentiation in human pheochromocytoma.

Adrenal Gland Neoplasms↗
PubMed1991

Stimulatory effects of brain natriuretic peptide on cyclic GMP accumulation and tyrosine hydroxylase activity in cultured bovine adrenal medullary cells.

We studied the effect of brain natriuretic peptide (BNP) on the accumulation of cyclic GMP and the phosphorylation and activity of tyrosine hydroxylase, compared with that of atrial natriuretic peptide (ANP), in cultured bovine adrenal medullary cells. 1. BNP as well as ANP increased cellular cyclic GMP accumulation in a concentration-dependent manner (10-1000 nmol/l). BNP (1 mumol/l) and ANP (1 mumol/l) produced a 60-fold and 30-fold increase in cyclic GMP accumulation, respectively. 2. The stimulatory effects of BNP and ANP on cyclic GMP accumulation were observed even when Ca2+ or Na+ was removed from the incubation medium. 3. 12-O-Tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C, inhibited the stimulatory effect of BNP on cyclic GMP accumulation in a concentration-dependent manner (1-100 nmol/l). Furthermore, the BNP-induced accumulation of cyclic GMP was attenuated by forskolin (1 mumol/l), an activator of adenylate cyclase. 4. BNP (1 mumol/l) and ANP (1 mumol/l) caused a significant increase in phosphorylation and activity of tyrosine hydroxylase in the cells. 5. In digitonin-permeabilized cells, cyclic GMP (1-100 mumol/l) activated tyrosine hydroxylase in the presence of ATP and Mg2+. These results suggest that BNP stimulates the accumulation of cyclic GMP in a manner similar to that of ANP. The increased accumulation of cyclic GMP by these peptides may be negatively modulated by protein kinase C and cyclic AMP and may cause the phosphorylation and activation of tyrosine hydroxylase in cultured bovine adrenal medullary cells.

Adrenal Medulla↗
PubMed1991

Effect of food on the bioavailability of cyclandelate from commercial capsules.

The bioavailability of five capsules of cyclandelate that are commercially available in Japan was determined in ten healthy volunteers by measuring mandelic acid (a main metabolite of cyclandelate) excreted in the urine. Bioinequivalence among the five capsules was demonstrated. The relative cumulative excretion of mandelic acid of the most poorly bioavailable capsule was 38% of the most highly bioavailable capsule. The effect of food on the bioavailability of these two capsules was investigated by use of two different kinds of food, one containing fat and one containing high carbohydrates but very low fat. The bioavailability of the two capsules was increased when subjects consumed both types of food before drug administration, although there was a greater effect on bioavailability with food containing fat. This suggests that the absorption of cyclandelate was incomplete in fasting subjects, even from the capsule with the highest bioavailability. Bioinequivalence between the two capsules remained after postprandial drug administration.

Administration, Oral↗
PubMed1991

Bioavailability of cyclandelate from capsules in beagle dogs and dissolution rate: correlations with bioavailability in humans.

The bioavailability in beagle dogs and the dissolution rates of cyclandelate from five capsule preparations commercially available in Japan were measured. One of the capsules that showed an extremely low bioavailability in humans also showed the lowest bioavailability in beagle dogs, although the difference in bioavailability with the highest preparation was smaller than in humans. A significant correlation was obtained between the results of the studies in humans and beagles. However, the power of the test using beagles was extremely low in comparison with that in the human study. Food enhanced the bioavailability of cyclandelate from the capsules having the highest and lowest bioavailability in the fasted state in beagles as observed in the human study previously. The bioinequivalence of the cyclandelate capsules detected in the fasted state disappeared in the fed state in the beagle dog study, while the bioinequivalence still remained in the non-fasted state in human subjects. Thus bioequivalence testing in the fed state led to different results in both species. The most poorly bioavailable capsule in both species in the fasted state showed a slow dissolution rate by several dissolution methods with moderate stirring. In order to obtain a good correlation with in vivo bioavailability, a large volume of test solution and addition of Tween 80 were required. Extensive growth of whiskers (needle-like crystals) was observed in the entire capsule mass having the lowest bioavailability.

Animals↗
PubMed1990

Protein kinase C subtypes in tissues derived from neural crest.

Subtypes of protein kinase C were determined in tissues derived from neural crest. The bovine adrenal medulla and rat superior cervical ganglia contained type III enzyme as the major subtype with a small amount of type II enzyme. In PC12 cells, treated with or without nerve growth factor, type III was the major subtype but a minor peak which is distinct from types II and III was observed. These results show that the type III enzyme is prevalent in various differentiation stages of neural crest and suggest that the enzyme relevant to the regulation of catecholamine synthesis and release in these cells is type III.

Adrenal Gland Neoplasms↗
PubMed1990

Conotoxin GIIIA: selective inhibition of 22Na influx via voltage-dependent Na channels in adrenal medullary cells.

Conotoxin GIIIA and GIIIB from the marine snail Conus geographus have been reported to inhibit voltage-dependent Na channels in skeletal muscle and postganglionic sympathetic neuron, but have no effect on Na channels in brain, giant axon and heart. In eel electroplax, conotoxins were also shown to share the common binding sites with saxitoxin (see review Gray et al. 1988). In bovine adrenal medullary cells, conotoxin GIIIA inhibited veratridine-induced influx of 22Na, 45Ca and secretion of catecholamines with an IC50 of 6 mumols/l while saxitoxin suppressed veratridine-induced responses with an IC50 of 6.3 nmol/l. [3H]Saxitoxin binding to the cells was inhibited by unlabeled saxitoxin with an IC50 of 5.1 nmol/l, but was slightly reduced by 10 mumols/l conotoxin GIIIA. Conotoxin GIIIA, at 10 mumols/l, did not alter carbachol-induced influx of 22Na, 45CA and secretion of catecholamines as well as high K-induced 45Ca influx and catecholamine secretion. These results indicate that conotoxin GIIIA, at concentrations 950 fold higher than saxitoxin, inhibits Na influx via voltage-dependent Na channels, but has no effect on the nicotinic receptor-ion channel complex or the voltage-dependent Ca channels. Conotoxin GIIIA seems to bind at the sites which are distinct from saxitoxin, but are functionally linked to the voltage-dependent Na channels. Conotoxins may be useful for the classification of Na channels in excitable cell membranes.

Adrenal Medulla↗