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Biomedical subjects

T Asano

Publications and source records attributed to T Asano.

At least 379 records · Page 21Linked to original sources
PubMed1995

Protective immune responses induced by secretion of a chimeric soluble protein from a recombinant Mycobacterium bovis bacillus Calmette-Guérin vector candidate vaccine for human immunodeficiency virus type 1 in small animals.

A recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG) vector-based vaccine that secretes the V3 principal neutralizing epitope of human immunodeficiency virus (HIV) could induce immune response to the epitope and prevent the viral infection. By using the Japanese consensus sequence of HIV-1, we successfully constructed chimeric protein secretion vectors by selecting an appropriate insertion site of a carrier protein and established the principal neutralizing determinant (PND)-peptide secretion system in BCG. The recombinant BCG (rBCG)-inoculated guinea pigs were initially screened by delayed-type hypersensitivity (DTH) skin reactions to the PND peptide, followed by passive transfer of the DTH by the systemic route. Further, immunization of mice with the rBCG resulted in induction of cytotoxic T lymphocytes. The guinea pig immune antisera showed elevated titers to the PND peptide and neutralized HIVMN, and administration of serum IgG from the vaccinated guinea pigs was effective in completely blocking the HIV infection in thymus/liver transplanted severe combined immunodeficiency (SCID)/hu or SCID/PBL mice. In addition, the immune serum IgG was shown to neutralize primary field isolates of HIV that match the neutralizing sequence motif by a peripheral blood mononuclear cell-based virus neutralization assay. The data support the idea that the antigen-secreting rBCG system can be used as a tool for development of HIV vaccines.

AIDS Vaccines↗
PubMed1995

Inhibition of pancreatic beta-cell glucokinase by antisense RNA expression in transgenic mice: mouse strain-dependent alteration of glucose tolerance.

We have generated transgenic mice, in either C57BL/6 or C3H background, expressing antisense glucokinase mRNA in beta-cells. The glucose phosphorylating activity at 60 mM glucose in transgenic islets was significantly lower than that in controls, and the insulin secretory response to glucose was lower in transgenic islets than in those of controls in both strains. Following i.p. glucose challenge, higher blood glucose levels were observed in transgenic mice than in controls in the C57BL/6 but not the C3H background. These data suggest that a beta-cell secretory defect, in combination with other undefined genetic factors, causes impaired glucose homeostasis in mice.

Animals↗
PubMed1995

Structural and functional analysis of the canine histamine H2 receptor by site-directed mutagenesis: N-glycosylation is not vital for its action.

G-protein-coupled receptors generally share a similar structure containing seven membrane-spanning domains and extracellular site(s) for N-glycosylation. The histamine H2 receptor is a member of the family of G-protein-coupled receptors, and has three extracellular potential sites for N-glycosylation (Asn-4, Asn-162 and Asn-168). To date, however, no information has been presented regarding N-glycosylation of the H2 receptor. To investigate the presence, location and functional roles of N-glycosylation of the H2 receptor, site-directed mutagenesis was performed to eliminate the potential site(s) for N-glycosylation singly and collectively. The wild-type and mutated H2 receptors were expressed stably in Chinese hamster ovary (CHO) cells or transiently in COS7 cells. Immunoblotting of the wild-type and mutated H2 receptors with an antiserum directed against the C-terminus of the H2 receptor showed that mutation at Asn-162, but not at Asn-168, resulted in a substantial decrease in the molecular mass. A mutation at Asn-4 led to a further decrease in the molecular mass. Tunicamycin treatment of the transfected cells yielded a sharp band with a molecular mass identical to that of the mutant devoid of all three potential sites for N-glycosylation. These findings indicate that the H2 receptor is N-glycosylated, and that N-glycosylation takes place mainly at two sites, Asn-4 and Asn-162. Neither the affinity for tiotidine nor that for histamine was affected by the mutagenesis. Immunocytochemistry and tiotidine binding showed that the mutated receptors were exclusively distributed on the cell surface in a fashion similar to that of the wild-type. In addition, the glycosylation-defective receptor was capable of activating adenylate cyclase and elevating the intracellular Ca2+ concentration in response to histamine in stable CHO cell lines. Thus N-glycosylation of the H2 receptor is not required for cell surface localization, ligand binding or functional coupling to G-protein(s).

1-Methyl-3-isobutylxanthine↗
PubMed1995

ATP-evoked membrane current in guinea pig adrenal chromaffin cells.

Adenosine 5'-triphosphate (ATP) evoked an inward current in whole-cell voltage-clamped adrenal chromaffin cells of the guinea pig. The reversal potential (Erev) of ATP-evoked current was about 0 mV in normal external solution and was shifted towards negative potentials by substituting Tris+ or sucrose, but not Ca2+, for the extracellular Na+. This current was mediated by the activation of non-selective cation channels and had some different properties from nicotinic current. It is suggested that these channels may function as a part of the ATP-induced Ca2+ influx pathway in guinea pig chromaffin cells.

Adenosine Triphosphate↗
PubMed1995

Evidence for a free N-acetylneuraminic acid-hydroxylating enzyme in pig mandibular gland soluble fraction.

The activity of a free N-acetylneuraminic acid (Neu5Ac)-hydroxylating enzyme which converted Neu5Ac into N-glycolyl-neuraminic acid (Neu5Gc) was demonstrated in the soluble fraction of pig mandibular gland. The hydroxylation was possible only with NADPH as the electron donor. The apparent Km was 4.5 mM Neu5Ac. At 0.5 mM monovalent cations had no effect on the hydroxylation of Neu5Ac whereas bivalent cations gave varied inhibition capacities ranging from 14 to 75%. EDTA gave a time-dependent enhancement of activity. It was concluded that the enzyme does not require an exogenously added inorganic cofactor. Results from salt fractionation of the soluble fraction and the use of inhibitors such as mercurials suggested that the hydroxylation of Neu5Ac to Neu5Gc may involve other, as yet unknown, component(s) and the possibility of electrons donated by NADPH being transferred to activated molecular oxygen (second substrate). We propose to name this enzyme N-acetyl-neuraminic acid hydroxylase.

Animals↗
PubMed1995

Mitochondrial diabetes mellitus--glucose-induced signaling defects and beta-cell loss.

Japanese diabetic patients whose mothers were also diabetic were screened, using peripheral leukocytes, for an A to G transition at nucleotide pair 3243 of the mitochondrial gene, a tRNA(Leu)(UUR) mutation. This mutation was identified in four pedigrees from among 300 unrelated patients. Diabetes mellitus cosegretated with the mutation, except in 1 young subject, and was maternally inherited. Long-term follow-up revealed that the underlying disorder in affected members is a progressive impairment of insulin secretion. In accord with this finding, this mutation was found to be highly prevalent in a subset of diabetes mellitus called slowly progressive IDDM; the mutation was identified in 3 of 27 Japanese patients enrolled in the prospective study of islet cell antibody (ICA)-positive, initially non-insulin-dependent diabetic patients, who are very likely to become insulin dependent in several years. The histologic characteristics of slowly progressive IDDM include loss, though incomplete, of pancreatic beta-cells. Mitochondrial gene defects in beta-cells could therefore cause glucose-induced signaling defects as well as beta-cell loss, which explains the wide range of diabetic phenotypes, from NIDDM phenotype to IDDM, in patients with this mitochondrial gene mutation.

Adolescent↗
PubMed1995

The effect of high-energy shock wave therapy combined with cisplatin on mouse hepatoma.

It is well documented that high-energy shock waves (HESW) can produce antitumor effects in vivo and in vitro. Furthermore, because HESW can be focused on a limited area, this therapy is considered applicable to the treatment of localized cancer. In this study, we investigated the effects of HESW therapy combined with cisplatin (CDDP) on MH134 hepatoma in a mouse model. Tumor growth was inhibited by 1 mg/kg CDDP treatment in combination with 2,000 HESW administration, but not by 1 mg/kg CDDP treatment only. Moreover, the CDDP concentration in the tumor increased after HESW administration. The active oxygen induced by HESW was then investigated by the electron spin resonance system, and it was found that HESW generated hydroxy-radicals. As oxygen radicals have been reported to change cell membrane potential, it is supposed that active oxygen induced by HESW changes cell membrane permeability, and that CDDP is concentrated in the tumor. Therefore, the combined therapy with HESW and CDDP showed synergistic inhibitory effects on tumor growth.

Animals↗
PubMed1995

Flush induced by fluoroquinolones in canine skin.

The flush induced by two fluoroquinolone antibacterial agents, balofloxacin and ofloxacin, was studied in beagle dogs. Intradermal injection of the fluoroquinolones at concentrations above 10(-5) M produced a localized flushed area. The flush responses to fluoroquinolones were inhibited by co-administration with H2-antagonist(s) (ranitidine or cimetidine), but not with H1-antagonist(s) (mepyramine or chlorpheniramine). Similar inhibitory effects of these H2-antagonists were observed for the response to histamine. The flush responses to fluoroquinolones were inhibited by a local pretreatment with compound 48/80 administered to deplete the local stores of mast cell-bound histamine. When the fluoroquinolones were orally administered at a dose of 400 mg/kg, the concentration of histamine in plasma was increased, being accompanied by systemic erythema. These results indicate that the flush induced by fluoroquinolones is mediated by histamine release from canine cutaneous mast cells and H2-receptor stimulation.

Animals↗
PubMed1995

Effects of orally administered Clostridium butyricum MIYAIRI 588 on mucosal immunity in mice.

The activation of local mucosal immunity by Clostridium butyricum MIYAIRI 588 (CBM588) was investigated in germ-free mice. An increase of polyclonal IgA production in the small intestine or secretion into the intestinal lumen was observed in mice mono-associated with CBM588 and fed a diet containing killed vegetative cells of CBM588 (VCBM). However, fecal IgA of anti-CBM588 was rarely formed in mice administered CBM588 during 6 weeks from administration. Cholera toxin was administered orally to SPF mice fed a diet containing CBM588, and IgA secretion of anti-cholera toxin was enhanced in mice fed a VCBM diet. In addition, the production of IgA, IgM and IgG in Peyer's patch cell culture was increased in the presence of VCBM. These results suggest that oral administration of CBM588 stimulates polyclonal mucosal immune activity and shows adjuvant activity for anti-cholera toxin.

Adjuvants, Immunologic↗
PubMed1995

Characteristics of ATP-induced catecholamine secretion from adrenal chromaffin cells of the guinea-pig.

The effect of ATP on catecholamine secretion and intracellular Ca2+ concentration ([Ca2+]i) was examined using perfused adrenal glands and dispersed chromaffin cells of the guinea-pig. The application of ATP (2 to 10 mM) for 2 min caused a dose-dependent increase in catecholamine secretion from perfused adrenal glands. ADP, but neither AMP nor adenosine, was also effective in increasing catecholamine secretion, though its potency was much less than that of ATP. 3. The ATP-induced secretory response was observed even under Na(+)-deficient conditions, but was reversibly abolished by removal of extracellular Ca2+. 4. In dispersed chromaffin cells, ATP (0.5 mM) caused increases in catecholamine secretion and [Ca2+]i, both of which were abolished after the removal of extracellular Ca2+. 5. These results indicate that ATP released from adrenal chromaffin cells together with catecholamine may exert a positive feedback influence on the following exocytotic catecholamine secretion. This effect may be accomplished by increasing the entry of extracellular Ca2+, but not by mobilizing intracellular Ca2+ stores in adrenal chromaffin cells of the guinea-pig.

Adenine Nucleotides↗
PubMed1995

Localization of various forms of the gamma subunit of G protein in neural and nonneural tissues.

For a study of the localization of various forms of the gamma subunit of G proteins, antibodies were raised in rabbits against peptides that corresponded to partial amino acid sequences of bovine gamma 2, gamma 3, gamma 5, and gamma 7. Affinity-purified antibodies against gamma 2, gamma 3, and gamma 5 reacted specifically with gamma 2, gamma 3, and gamma 5, respectively, but the antibody against gamma 7 reacted with gamma 2, gamma 3, and a novel gamma subunit, designated gamma S1, as well as with gamma 7. Because these antibodies reacted with the respective forms of the gamma subunit from rat brain, we investigated the localization of gamma subunits in the rat. gamma 2 and gamma 3 were abundant in all regions in the brain, whereas the concentration of gamma 5 and gamma 7 was relatively low with the single exception being a high concentration of gamma 7 in the striatum. The concentration of gamma 2 was consistently high during ontogenic development in the rat brain, whereas gamma 3 appeared about a week after birth and their concentrations then increased until a month after birth. In tissues other than the brain, gamma 3 was observed only in the pituitary gland, whereas gamma 2, gamma 5, and gamma 7 were found in a variety of tissues. In addition, most tissues contained relatively high concentrations of some other gamma subunit, which was detected with an antibody against a gamma 7-derived peptide and appeared to be gamma S1. Among cloned cells tested, gamma 3 was detected only in PC12 pheochromocytoma cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

Endoscopic ultrasound-guided pancreatography: a case report.

Endoscopic ultrasound-guided pancreatography was performed on a 48-year-old man with a diagnosis of pancreatic stone. A pylorus-preserving pancreaticoduodenectomy had been performed previously on this patient, approximately two years earlier, following the diagnosis of a tumor-forming pancreatitis. Endoscopic retrograde pancreatography and conventional ultrasound-guided percutaneous pancreatography had failed to yield a diagnosis. However, endoscopic ultrasound-guided pancreatography was performed successfully, delineating the pancreatic duct and a filling defect caused by intraductal calculi. Endoscopic ultrasound-guided pancreatography will be a potential alternative in cases when endoscopic retrograde pancreatography has failed or proved non-diagnostic.

Calculi↗
PubMed1995

Rare association of human papillomavirus DNA with esophageal cancer in Japan.

To examine whether human papillomavirus (HPV) DNA is associated with esophageal cancer, frozen and paraffin-embedded neoplasms of the upper aerodigestive tract, including esophageal cancer, were investigated. DNA obtained from frozen specimens and cell lines were analyzed by both polymerase chain reaction (PCR) and Southern blot hybridization. DNA from paraffin-embedded samples were analyzed strictly by PCR. DNA of HPV types 6 and 11 was detected in papillomas of the upper respiratory tract at > 50%. However, HPV DNA was infrequently detected in specimens from the upper digestive tract (31 esophageal cancers and 2 esophageal carcinoma--derived cell lines), even by PCR at a sensitivity of 0.1 copy number per cell. These results suggest that the etiologic significance of HPV infection in esophageal cancer is negligible.

Base Sequence↗
PubMed1995

The G-protein G(o) in mammalian cardiac muscle: localization and coupling to A1 adenosine receptors.

To investigate the functional relevance of the G-protein G(o) to adenosine-induced effects in the heart, we studied the localization of G(o) and its interaction with A1 adenosine receptors. Concentrations of G(o) in various mammalian hearts differed markedly between the atrial and the ventricular muscle, as well as among species. In most species examined, the concentration of G(o) was much higher in the atrium than in the ventricle. The highest levels of G(o) in atria and ventricles were found in the ferret heart. An immunohistochemical study of the ferret heart with G(o) alpha-specific antibodies showed that G(o) was localized throughout the membranes of cardiac myocytes, including the intercalated disks. In addition, G(o) was densely distributed in the nerve fibers and Purkinje fibers. Analyses of G(o) alpha subtypes showed that bovine atrium mainly contained G(o)A alpha, while bovine ventricle contained only G(o)B alpha. By contrast, ferret ventricle contained both subtypes of G(o) alpha. To study the coupling of G(o) to A1 adenosine receptors, receptors in ventricular membranes of ferrets, which had been pretreated with pertussis toxin, or purified receptors were reconstituted with purified G(o)A and G(o)B. The reconstitution experiments indicated that both subtypes of G(o) coupled with A1 adenosine receptors. These results suggest that the effect of adenosine is mediated by both G(o)A and G(o)B in membranes of ferret cardiac myocytes.

Animals↗
PubMed1995

Enhancement of stress-induced synthesis of stress proteins by mastoparan in C6 rat glioma cells.

The levels of two small stress proteins, hsp27 and alpha B crystallin, were low in C6 glioma cells confluency. However, the levels of the two proteins increased after exposure of cells to heat (42 degrees C for 30 min) or arsenite (50-100 microM for 1 h) stress. When cells were exposed to arsenite or heat in the presence of mastoparan, a peptide toxin from wasp venom, the induction of hsp27 and alpha B crystallin was markedly stimulated, as detected by means of specific immunoassays, Western blot analysis, and Northern blot analysis. The response of hsp70 to each stress was also enhanced in the presence of mastoparan. Treatment of cells with 40 microM mastoparan alone barely induced the accumulation of hsp27 and alpha B crystallin. The stimulatory effect of mastoparan was little affected in cells that had been treated with pertussis toxin, but it was strongly suppressed in the presence of quinacrine, an inhibitor of phospholipase A2. These results suggest that mastoparan, which is an activator of phospholipase A2, enhances the responses to stress of hsp27, alpha B crystallin and hsp70 by increasing the metabolic activity of the arachidonic acid cascade.

Animals↗
PubMed1995

Modulation of the stress-induced synthesis of stress proteins by a phorbol ester and okadaic acid.

The expression of alphaB crystallin, hsp27, and hsp70 in C6 cells increased when they were exposed to arsenite (50 microM for 1 h) or heat (42 degrees C for 30 min), as detected by specific immunoassays, Western blot analysis, and Northern blot analysis. When cells were exposed to arsenite in the presence of 0.1 microM phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, or 0.2 microM okadaic acid, an inhibitor of phosphoserine/phosphothreonine protein phosphatases, expression of alphaB crystallin was markedly enhanced. The induction of hsp27 and hosp70 expression was also stimulated to a considerable extent in the same cells. The stimulatory effect of PMA was further enhanced in the presence of okadaic acid, but it was strongly inhibited in the presence of 0.5 microM staurosporine, an inhibitor of protein kinase C. PMA and okadaic acid also stimulated the response to heat stress of the expression of alphaB crystallin, but they barely stimulated the response to heat stress of hsp27. The extent of stimulation of the arsenite-induced responses by PMA and okadaic acid was greater when the concentration of arsenite (i.e. the magnitude of the stress) was relatively low (25-50 microM). The arsenite-induced release of arachidonic acid from cells was also stimulated in the presence of PMA and/or akadaic acid, and the stimulatory effects of PMA and okadaic acid on the arsenite-induced accumulation of alphaB crystallin and hsp27 were strongly suppressed by quinacrine, an inhibitor of phospholipase A2. These results suggest that the stimulatory effects of PMA and okadaicacid on the stress responses are cuased, in part, by the increased metabolic activity of the arachidonic acid cascade, as a consequence of the activation of phospholipase A.

Alkaloids↗