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T Nagao

Publications and source records attributed to T Nagao.

At least 19 recordsLinked to original sources
PubMed1999

Nonspecific effects of the pharmacological probes commonly used to analyze signal transduction in rabbit parietal cells.

In order to examine some possibly misleading conclusions of the pharmacological analysis of the signal transduction pathways of gastric acid secretion, we evaluated various agents including inhibitors of protein kinase C, cyclic AMP-dependent protein kinase, phospholipase C, phospholipase A2, lipoxygenase, casein kinase, calmodulin, myosin light chain kinase, tyrosine kinase, anion exchanger, and protein phosphatase; and activators of protein kinase C. Among them, the cyclic AMP-dependent protein kinase inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinylsulfonamide (H-89), the phospholipase A2 inhibitor 2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid (ONO-RS-082), three myosin light chain kinase inhibitors (1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-7), 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9), and wortmannin), the anion exchanger inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), the phospholipase C inhibitor neomycin, and most known calmodulin antagonists strongly inhibited [14C]aminopyrine accumulation, an indicator of acid secretion, in isolated rabbit gastric glands stimulated by N6,2'-O-dibutyryl-cyclic AMP. ONO-RS-082, calmidazolium, and DIDS inhibited H+,K+-ATPase. Most of the chemicals with antisecretory activity showed protonophore-like activity in gastric microsomes as well as in the mitochondria. It is concluded that H-89, ONO-RS-082, ML-7, ML-9, neomycin, and all calmodulin antagonists tested so far should not be used as tools to analyze gastric acid secretion.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1999

[Pharmacological evaluation of the development candidate].

In recent years, drugs developed in Japan are used internationally in other countries. The pharmaceutical pre-clinical phase in critical in the drug developing cycle. Pharmacologists contribute to finding the leading compounds and evaluate the right compound for clinical trial. The selection of the right compound for development will save both time and money. In the pharmacological evaluation of a development candidate, in vivo animal studies that can assure the clinician that the drug is both effective and safe are usually required. Studies on the mechanism of action of the drug and how the drug works in the diseased state becomes important since a known target molecule usually serves as the basis for the development of a new drug.

Animals↗
PubMed1998

C-terminal peptide of fusarium heterosporum lipase is necessary for its increasing thermostability.

Saccharomyces cerevisiae bearing a lipase cDNA from Fusarium heterosporum produced two lipases, A and B. Lipase B was significantly more stable to temperature than lipase A, but their optimum temperatures were similar. Lipase B was composed of one polypeptide (301 amino acids), and lipase A was composed of two polypeptides (275 and 26 amino acids) generated by the cleavage between Arg275 and Asp276 with a trypsin-like protease. It was suggested that the C-terminal peptide (26 amino acids) tightened the lipase structure when bound to the catalytic domain (275 amino acids) through a peptide bond. The tight structure was loosened by cleavage of the C-terminal peptide, even though the peptide interacted noncovalently with the catalytic domain, possibly through charged amino acids, in which it is rich. Deletion of the C-terminal peptide greatly decreased the lipase production by the recombinant S. cerevisiae, although its transcriptional level was the same as that of cells carrying the wild-type gene. These facts suggested that the C-terminal peptide affected the lipase production in the post-transcriptional step.

Amino Acid Sequence↗
PubMed1998

Translocation of HSP27 to cytoskeleton by repetitive hypoxia-reoxygenation in the rat myoblast cell line, H9c2.

We investigated the possible changes in the distribution of HSP27 after a brief hypoxia-reoxygenation stress in the rat myoblast cell line, H9c2, as a model of ischemic preconditioning. Cells were exposed to 4 cycles of 5 min. of hypoxia and 5 min. of reoxygenation. In the normoxic condition, HSP27 was exclusively found in the cytosolic fraction. After the hypoxia-reoxygenation cycle, HSP27 redistributed to the cytoskeletal fraction, which was blocked by 10 microM SB 203580, a specific inhibitor of p38 MAP kinase. Cells treated with the repetitive hypoxia-reoxygenation developed resistance against cell death induced by hypoxia for 24 hours. The changes in localization of HSP27 found in the present study may reflect the mechanism of preconditioning in the cardiac myocyte.

Animals↗
PubMed1998

Functional interaction between benzothiazepine- and dihydropyridine binding sites of cardiac L-type Ca2+ channels.

We have previously shown, in a radioligand binding study with single ventricular myocytes, that benzothiazepine and dihydropyridine binding sites interact with each other. To further examine whether this interaction between the two binding sites is reflected in the function of L-type Ca2+ channels, the blocking action of diltiazem, nitrendipine, and the combination of these two drugs on L-type Ca2+ channel currents was investigated using baby hamster kidney cells expressing the alpha 1C, alpha 2/delta, beta and gamma subunits of the Ca2+ channel. The effects of diltiazem and nitrendipine were additive at room temperature but synergistic at 33 degrees C. The use-dependent block by 3 microM of diltiazem was significantly enhanced from 28% to 68% by addition of 30 nM of nitrendipine, which by itself did not have a blocking effect. Thus, we conclude that benzothiazepine- and dihydropyridine binding sites interact and potentiate their blocking action on L-type Ca2+ channels in a temperature-dependent manner.

Animals↗
PubMed1998

Salivary gland malignant myoepithelioma: a clinicopathologic and immunohistochemical study of ten cases.

BACKGROUND: Malignant myoepithelioma (MME) of the salivary gland, also known as myoepithelial carcinoma, is rare and its biologic behavior has not been clarified fully. METHODS: Ten cases of MME were analyzed for their clinicopathologic features and immunohistochemical characteristics, focusing on prognostic factors and tumor differentiation. In addition, six cases of benign myoepithelioma (BME) also were examined for comparison. RESULTS: The ten patients with MME (3 men and 7 women) ranged in age from 48-81 years (mean, 61.9 years). Seven cases of MME arose in the parotid salivary gland, two in the submandibular salivary gland, and one in minor salivary glands of the soft palate. In the current series, the incidence of MME was 0.45% among 1945 cases of major salivary gland tumors. Seven cases of MME developed from a benign preexisting tumor (six in pleomorphic adenoma and one in BME). Four of nine patients with MME died of the disease and two patients developed a recurrence. It was shown that MMEs were comprised of one cell type or a combination of two cell populations; these included, in order of incidence, epithelioid, spindle, and plasmacytoid cells. Patients with MME with marked cellular pleomorphism and perineural invasion had a poor prognosis. Immunohistochemically, putative myoepithelial markers such as muscle actins, cytokeratin 14, vimentin, and calponin, and S-100 protein were expressed highly in MME. High and low molecular weight cytokeratins and epithelial membrane antigen also frequently were positive in MME. p53 expression was observed in five MME cases, four of which either recurred or were fatal. Cellular proliferative activity assessed by mitotic count and the Ki-67 labeling index was significantly higher in MME cases than in BME cases. In limited cases, such cellular proliferative activity was shown to have prognostic value. Ultrastructurally, the tumor cells displayed certain myoepithelial characteristics. CONCLUSIONS: MME is a rare salivary gland tumor showing clinicopathologic diversity and presenting with various stages of myoepithelial differentiation. Histologic aggressiveness, marked cellular pleomorphism, p53 expression, and high cell proliferative activity were found to be correlated with a poor clinical outcome.

Actins↗
PubMed1998

Effect of lipo-prostaglandin E1 on crescentic-type anti-glomerular basement membrane nephritis in rats.

The antinephritic effect of lipo-prostaglandin E1, prostaglandin E1 ((1R,2R,3R)-3-hydroxy-2-[(E)-(3S)-3-hydroxy-1-octenyl]-5-oxocyclopent ane heptanoic acid) incorporated in lipid microspheres was investigated using an experimental model of nephritis, crescentic-type anti-glomerular basement membrane nephritis. Lipo-prostaglandin E1 was given i.v. twice a day at 20, 40 and 80 microg/kg and azathioprine, an immunosuppressive agent, at 20 mg/kg was given p.o. once daily from the autologous phase, in which glomerulonephritis was fully developed (the 21 st day after injection of the anti-glomerular basement membrane serum), to the 50th day. Lipo-prostaglandin E1 (40 and 80 microg/kg x 2 per day) significantly inhibited the development of glomerular alterations as well as the elevation of proteinuria and plasma creatinine. Lipo-prostaglandin E1 (20 microg/kg x 2 per day) and azathioprine (20 mg/kg per day) significantly inhibited only the glomerular histopathological changes. Lipo-prostaglandin E1 at three doses significantly decreased the deposition of both rabbit immunoglobulin G and rat immunoglobulin G on the glomerular basement membrane in nephritic rats, but azathioprine apparently inhibited only the deposition of rat immunoglobulin G. A single administration of lipo-prostaglandin E1 inhibited the elevation of platelet aggregation and restored the decrease in renal tissue blood flow in nephritic rats. In addition, a single administration of lipo-prostaglandin E1 inhibited the elevation of glomerular thromboxane B2 and 6-keto prostaglandin F1alpha production in nephritic rats. These results suggest that lipo-prostaglandin E1 may be an effective agent for the treatment of glomerulonephritis. Its antinephritic effect may be due to the inhibition of platelet aggregation, an increase in renal tissue blood flow, a decrease in rabbit and rat immunoglobulin G deposition, and amelioration of the abnormal metabolism of arachidonic acid.

6-Ketoprostaglandin F1 alpha↗
PubMed1998

5-hydroxydecanoate selectively reduces the initial increase in extracellular K+ in ischemic guinea-pig heart.

The aim of the present study was to determine the effect of 5-hydroxydecanoate (5-HD) on extracellular K+ levels during global ischemia for 30 min employing K+-sensitive electrodes in isolated guinea-pig hearts. 5-HD (100 microM) reduced the K+ accumulation during the early period of ischemia, but did not inhibit the elevation of extracellular K+ in the latter half of the ischemic period which was selectively enhanced by ouabain (3 microM). Thus, 5-HD appears to exert a similar mode of action as glibenclamide on extracellular K+ accumulation in the ischemic guinea-pig hearts. The present study also strengthens the previous conclusion that an ATP-sensitive K+ channel contributes only to the initial increasing phase of extracellular K+ accumulation during ischemia in guinea-pig hearts.

Animals↗
PubMed1998

Developmental rescue of Drosophila cephalic defects by the human Otx genes.

The molecular mechanisms of head development are a central question in vertebrate and invertebrate developmental biology. The anteriorly expressed homeobox gene otd in Drosophila and its homolog Otx in mouse are required for the early development of the most anterior part of the body, suggesting that a fundamental genetic program of cephalic development might be conserved between vertebrates and invertebrates. We have examined this hypothesis by introducing the human Otx genes into flies. By inducing expression of the human Otx homologs with a heat shock promoter, we found that both Otx1 and Otx2 functionally complement the cephalic defects of a fly otd mutant through specific activation and inactivation of downstream genes. Combined with previous morphological studies, these results are consistent with the view that a common molecular ground plan of cephalization was invented before the diversification of the protostome and the deuterostome in the course of metazoan evolution.

Amino Acid Sequence↗
PubMed1998

Comparative study of behavioral development between high and low shuttlebox avoidance rats.

Previously, we reported that high- and low-avoidance animals (HAA and LAA, respectively), selectively bred for different avoidance response rates in a shuttlebox avoidance test, showed additional behavioral differences in wheel cage activity and in water maze performance after weaning. In the present study, physical and behavioral development were examined in HAA and LAA during the preweaning period. As compared to HAA, LAA offspring showed lower body weight, delayed eye opening, poorer performance in pivoting and negative geotaxis, and increased open-field activity. A fostering study indicated that these differences observed in eye opening, pivoting, negative geotaxis, open-field activity, swimming speed, shuttlebox avoidance and wheel cage activity were independent of maternal care. Only the pup weight was strongly dependent on the maternal line. These results indicate that behavioral differences between HAA and LAA observed in the pre- and postweaning periods may be linked to the avoidance genotype, but the difference in pup weight may be caused by maternal care.

Animals↗
PubMed1998

Basal cell adenocarcinoma of the salivary glands: comparison with basal cell adenoma through assessment of cell proliferation, apoptosis, and expression of p53 and bcl-2.

BACKGROUND: Basal cell adenocarcinoma (BCAC) of the salivary gland is a rare tumor and recently described entity. Eleven cases of BCAC are presented here and compared with basal cell adenoma (BCA) through assessment of cell proliferative activity, apoptosis, and expression of p53, bcl-2, and epidermal growth factor receptor (EGFR) because these two tumors show close similarity in some cytologic and architectural characteristics. METHODS: Formalin fixed, paraffin embedded sections of 11 cases of BCAC and 9 cases of BCA, selected from the authors' files of 1851 primary tumors of the major salivary gland, were examined using immunostaining for Ki-67 (MIB-1), p53, bcl-2, and EGFR. In addition, apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling. RESULTS: The incidence of BCAC was 0.6% among patients with major salivary gland tumors in the current series. Nine cases of BCAC arose in the parotid gland and two were of submandibular gland origin. Approximately 50% of the patients had recurrences, but no patient developed metastases or died of disease. Vascular involvement (75%), perineural invasion (36%), and necrosis (45%) were common features. Cell proliferative activity, including mitotic count, Ki-67 labeling index (LI), and apoptotic index were significantly higher in BCAC than BCA. More than four mitotic figures per ten high-power fields or a Ki-67 LI > 5% appeared to be limited to cases of BCAC. Considering those cases expressing p53 or EGFR in > 10% of tumor cells as positive, 6 of the 11 BCAC cases were positive for p53 and 3 were positive for EGFR. In contrast, all BCA cases were negative for p53 and EGFR. Although all cases of BCA were strongly positive for bcl-2 (> 50% of tumor cells), 3 of 11 cases of BCAC were completely negative. CONCLUSIONS: BCAC is a rare salivary gland tumor with a relatively high recurrence rate. Examination of cell proliferation, apoptosis, and expression of p53, bcl-2, and EGFR were found to be useful in distinguishing malignant basal cell tumors from their benign counterparts arising in the salivary gland.

Adenocarcinoma↗
PubMed1998

Effects of long-acting angiotensin-converting enzyme inhibitor, imidapril, on the lower limit of cerebral blood flow autoregulation in hypertensive rats.

The objective of the present study was to examine the effects of a long-acting angiotensin converting enzyme inhibitor, imidapril ((4S)-1-methyl-3-¿(2S)-2-[N-(1S)-1-ethoxycarbonyl-3-phenylpropyl) amino] propionyl¿-2-oxoimidazolidine-4-carboxylic acid hydrochloride), for 7 days on the cerebral blood flow autoregulatory response to hypotension in hypertensive rats. We measured the cerebral blood flow at rest and during hemorrhagic hypotension, using laser-Doppler flowmetry. At the same time, the absolute baseline cerebral blood flow values in the parietal cortex were quantified with the hydrogen clearance method. After administration of imidapril at a dose of 5 mg/kg/day for 7 days, the resting value of mean arterial blood pressure was significantly decreased by 25 mm Hg (P < 0.001), cerebral vascular resistance was lowered by 14.4% (P < 0.05) and the lower limit of cerebral blood flow autoregulation was shifted to a lower level, 106+/-11 mm Hg (mean +/- S.D.), from 137+/-8 mm Hg in the control group (P < 0.001), while resting cerebral blood flow remained unchanged. The present results demonstrated that imidapril preserves cerebral blood flow and significantly shifts the lower limit of cerebral autoregulation towards lower blood pressure levels.

Adenosine Triphosphate↗
PubMed1998

Effects of prenatal exposure to 5-fluoro-2'-deoxyuridine on developing central nervous system and reproductive function in male offspring of mice.

The effect of 5-fluoro-2'-deoxyuridine (FrdU) on the developing brain and postpubertal reproductive function of male mouse offspring treated prenatally was investigated. FrdU was administered intraperitoneally to pregnant ICR mice at 1.5, 3, 6, 12.5, 25, and 50 mg/kg/day on days 8 through 13 of gestation or 12.5, 25, and 50 mg/kg/day on days 14 through 18 of gestation. Dams were allowed to deliver spontaneously. Dams treated with FrdU at 12.5, 25, and 50 mg/kg/day on days 8 through 13 of gestation did not deliver because of entire intrauterine death of embryos. Male offspring were aged for 10 or 15 weeks and then cohabited with untreated female mice for assessment of reproductive performance. Histological examination of the testis, epididymis, prostate, and seminal vesicle of offspring at 12 weeks of age, and sperm analysis of offspring at 12 or 17 weeks of age were performed. Dose-dependent decreases in body weight gain were noticed throughout the life of offspring. A marked decrease in the copulation rate was noted in the group treated with FrdU at 6 mg/kg/day on days 8 through 13 of gestation. However, neither histological examination of testes and sex-accessory glands nor sperm analysis revealed adverse effects of FrdU on the reproductive function in the male offspring of dams treated with FrdU at 6 mg/kg/day on days 8 through 13 of gestation. There were no significant differences in the relative weight of testes and epididymides between the group treated with FrdU at 6 mg/kg/day on days 8 through 13 of gestation and the control group. Absolute brain weight in the groups treated with FrdU on days 8 through 13 of gestation significantly decreased, while relative brain weight increased in the group treated at 6 mg/kg/day on days 8 through 13, and at 25 and 50 mg/kg/day on days 14 through 18 of gestation. Dilatation of the lateral and third ventricles was observed in all of the male offspring of dams treated with FrdU at 6 mg/kg/day on days 8 through 13 of gestation, when inspected at 12 and 17 weeks of age. In the subsequent study, ICR mice were treated intraperitoneally with FrdU at 6.25-100 mg/kg on day 12 of gestation, and the fetuses obtained 24 h after treatment. Histological observation was performed in the ventricular zone of telencephalon, and in the ependymal and mantle layers of diencephalon in the fetal brain. The incidence of pyknotic cells in these areas was increased linearly with increasing FrdU dose. From these results and our previous findings, we suggest that damage to the central nervous system, a substantial neuronal deficit, resulting from excessive cell death in the developing brain may lead to reproductive dysfunction after puberty.

Abnormalities, Drug-Induced↗
PubMed1998

Shortening of action potential duration is not prerequisite for cardiac protection by ischemic preconditioning or a KATP channel opener.

Our purpose was to determine whether amelioration of myocardial contractile dysfunction by an ATP-sensitive potassium (KATP) channel opener or ischemic preconditioning is mediated by shortening of action potential duration during the early period of ischemia. Extracellular potassium concentration ([K+]e), monophasic action potential duration (MAPD) and thickening fraction were measured during ischemia and reperfusion of the left anterior descending coronary artery in anesthetized dogs. Control dogs were subjected to a 10-min occlusion (test occlusion) followed by a 120-min reperfusion. The five dogs which made up the pinacidil group, received 0.03 mg/kg as an i.v. bolus and then were infused at a rate of 0.04 mg/kg/h for 20 min prior to the test occlusion. In the preconditioning group, six dogs were subjected to a 5-min occlusion and a 10-min reperfusion prior to the test occlusion and reperfusion. Both pinacidil and preconditioning improved regional contraction during reperfusion after the test occlusion. In the control group, MAPD shortened and [K+]e increased during ischemia. Preconditioning abolished MAPD shortening and blunted the rise of [K+]e during ischemia. Pinacidil did not affect either the shortening of MAPD or [K+]e elevation during ischemia. These results suggest that the shortening of MAPD is not a prerequisite for amelioration of contractile dysfunction by a KATP channel opener or ischemic preconditioning.

Action Potentials↗
PubMed1998

Effects of trimebutine maleate on gastric motility in patients with gastric ulcer.

The effects of trimebutine maleate (TM), a prokinetic drug, on gastrointestinal motility in patients with gastric ulcer were investigated. Twenty patients with active gastric ulcers were allocated to two groups; 10 patients received a proton pump inhibitor alone (PPI group), given orally, and 10 patients received oral TM in combination with a PPI (PPI + TM group), each for a period of 8 weeks. Electrogastrography (EGG) and gastric emptying were measured before and after the treatment period. During the active ulcer stage, tachygastria (more than 0.06 Hz) or bradygastria (less than 0.04 Hz) in the EGG frequency were observed in 9 patients either before or after meals. During the healed ulcer stage, tachygastria or bradygastria was observed in 4 of 10 patients in the PPI group, while in the PPI + TM group, 1 patient had tachygastria and none had bradygastria. Postprandial dip (PD) was observed in 3 of the 20 patients during the active stage, while after treatment, PD was observed in 3 patients in the PPI group and in 6 patients in the PPI + TM group, respectively. Gastric emptying in the PPI group did not show any change between before and after treatment, while that in the PPI + TM group improved significantly after treatment. These results suggest that TM may have an ameliorative effect on abnormal gastric motility in patients with gastric ulcer.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1998

Calcitonin gene-related peptide affords gastric mucosal protection by activating potassium channel in Wistar rat.

BACKGROUND & AIMS: Calcitonin gene-related peptide (CGRP) protects the gastric mucosa against injurious stimuli in various experimental models. The underlying mechanism could be the increase in gastric mucosal blood flow (GMBF). A number of endogenous vasodilators exert their effects through the activation of adenosine triphosphate (ATP)-sensitive potassium (KATP) channels on vascular smooth muscle. The present experiments were performed to elucidate whether CGRP increases GMBF through the activation of KATP channels and whether the channels are involved in the protection by CGRP of gastric mucosa. METHODS: GMBF was determined by the hydrogen-clearance technique in male Wistar rats. Mucosal lesions were produced by intragastric superfusion with 0.15N HCland 15% ethanol for 40 minutes. Effects of an agonist (Y-26763, intra-arterially) and an inhibitor (glibenclamide, intravenously) of KATP channels were tested. RESULTS: Y-26763 increased GMBF, which was abolished by glibenclamide, and a CGRP-induced increase in GMBF was attenuated by glibenclamide. Macroscopic and microscopic lesions were exacerbated by human CGRP-(8-37) (a CGRP-1 receptor antagonist; intra-arterially) and glibenclamide but were ameliorated by exogenous CGRP (intra-arterially). CONCLUSIONS: CGRP protects the gastric mucosa against ulcerogenic stimuli, at least in part, through the activation of KATP channels in rats.

Animals↗
PubMed1998

Domains of beta1 and beta2 adrenergic receptors to bind subtype selective agonists.

We studied the binding region of several beta1 and beta2 selective agonists by using chimeric beta1 and beta2ARs, and point-mutated beta2 adrenergic receptors (ARs). By replacing a single transmembrane domain (TMD) of beta1AR (or beta2AR) with the corresponding region of beta2AR (or beta1AR), we found that beta2 or beta1 selectivities were determined by TMD2 and TMD7 of beta2AR or by TMD2 of beta1AR, respectively. Alanine-substituted beta2AR mutants showed that tyrosine at position 308 in TMD7 played an important role in binding of beta2 selective agonists with high affinity. These data also suggested that the substituent on the amine portion was important for subtype selective agonist binding.

Adrenergic beta-Agonists↗