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Biomedical subjects

H Horiuchi

Publications and source records attributed to H Horiuchi.

At least 127 records · Page 7Linked to original sources
PubMed1995

Beneficial effects of a novel anti-hypoxemic agent, TEI-7322, on bleomycin-induced experimental hypoxemia in rats.

Almitrine bismesylate is known to be an anti-hypoxemic agent that acts via the enhancement of hypoxic pulmonary vasoconstriction. However, screening for this class of compounds has been minimal, owing, in part, to a lack of convenient hypoxemic models in small animals. The present study was designed to establish a convenient model of hypoxemia induced by bleomycin and to evaluate anti-hypoxemic agents including a newly synthesized compound. TEI-7322, 2-allylamino-4-tert-butyl-amino-7-methyl-7H-pyrrolo[2,3- d]pyrimidine hydrochloride by using this model. Bleomycin was intratracheally instilled into rats. After 3 weeks, the arterial blood gas pressures were monitored in the animals in the conscious state. Then, prednisolone, doxapram, almitrine or TEI-7322 was administered to the bleomycin-treated rats to monitor changes in arterial blood gas pressures. Bleomycin-treated rats showed a decrease in the arterial blood O2 pressure (PaO2). The blood CO2 pressure (PaCO2) increased, along with an increase in the alveolar-arterial oxygen difference (AaDO2). These blood gas pressures in bleomycin-treated rats were not affected by treatment with prednisolone. Doxapram decreased the PaCO2 but did not change the PaO2. However, administration of almitrine or TEI-7322 significantly improved the PaO2 of bleomycin-treated rats with a decrease in the PaCO2. In conclusion, (1) bleomycin-induced lung injury causes hypoxemia in rats, probably resulting from ventilation-perfusion inequality; thus this model may be useful for evaluating anti-hypoxemic agents; and (2) TEI-7322, as well as almitrine, showed anti-hypoxemic effects in this model with different properties from those of doxapram, possibly due to improvement of ventilation-perfusion inequality, indicating that TEI-7322 may be a potent candidate for the treatment of hypoxemia.

Almitrine↗
PubMed1995

A GDP/GTP exchange-stimulatory activity for the Rab5-RabGDI complex on clathrin-coated vesicles from bovine brain.

Small GTPases of the Rab family are key regulators of intracellular transport. They are associated with the cytoplasmic surface of distinct exocytic and endocytic organelles and with transport vesicles connecting these compartments. Rab proteins are also present in the cytosol in the GDP-bound conformation complexed to Rab GDP dissociation inhibitor (RabGDI). Upon membrane association, RabGDI is released, and the Rab protein is converted into the GTP-bound form. In this paper we have investigated whether Rab5, which regulates the clathrin-coated vesicle-mediated pathway of endocytosis, can directly associate with the membrane of clathrin-coated vesicles (CCV) purified from bovine brain in vitro. We found that RabGDI can specifically deliver Rab5 but not Rab7, which is localized to late endosomes, to CCV. Furthermore, CCV contain a heat- and trypsin-sensitive activity that stimulates the dissociation of GDP from Rab5, but not from Rab7, and the subsequent binding of GTP. The activity was found to be associated with the CCV membrane but not with the coat components. CCV weakly stimulated GDP release from either post-translationally modified or unmodified Rab5 alone. However, maximal GDP dissociation stimulation required the presence of RabGDI, suggesting that the factor(s) responsible for the membrane association and GDP/GTP exchange of Rab5 recognize the protein complexed to RabGDI. These data demonstrate that CCV are competent for acquiring Rab5 and for converting the molecule into the GTP-bound active form.

Animals↗
PubMed1995

Analysis of the 3-phosphoglycerate kinase 2 promoter in Rhizopus niveus.

Promoter analysis was performed on the Rhizopus niveus 3-phosphoglycerate kinase 2-encoding gene (pgk2), one of the two pgk genes (pgk1 and pgk2) from this filamentous fungus sequenced so far. Deletion mutants of the promoter region were fused to the Escherichia coli uidA gene (which codes for beta-glucuronidase; GUS), and introduced into R. niveus to measure the intracellular GUS activities of the transformants. Deletion of the sequence between nt -174 to -133 (numbers indicate the position from the putative translation start codon) caused a significant decrease in the ratio of the GUS activity of the transformant cultured in glucose medium compared to that in glycerol medium. In this region, a 21-nt sequence which is well conserved between pgk1 and pgk2 is present. When it was inserted into the promoter region of the uninducible gene encoding RNase Rh of R. niveus, ligated in front of uidA and introduced into R. niveus, the GUS activity of the transformant was greatly induced by glucose, but less by glycerol. We therefore suggest that the 21-nt sequence is a glucose-inducible transcriptional activator of R. niveus. This is the first report on a transcriptional activator in zygomycetes.

Base Sequence↗
PubMed1995

Cloning of the Rhizopus niveus pyr4 gene and its use for the transformation of Rhizopus delemar.

We have cloned a pyr4 gene encoding orotidine-5'-monophosphate decarboxylase of the filamentous fungus Rhizopus niveus. The pyr4 gene of R. nivens has an open reading frame composed of 265 amino-acid residues and has two putative introns. We have also isolated a pyr4 mutant of Rhizopus delemar from 5-fluoroorotic acid-resistant mutants and transformed it with the pyr4 gene of R. niveus as a selectable marker. Introduced DNA was integrated into the chromosome in a multiple tandem array. The mitotic stability of the introduced DNA was increased by a repeated sporulation process. The expression of the Escherichia coli beta-glucuronidase gene in R. delemar was successfully obtained under the control of the pgk2 gene promoter of R. niveus by co-transformation with the pyr4 gene.

Amino Acid Sequence↗
PubMed1995

Histopathologic study of human lacrimal gland. Statistical analysis with special reference to aging.

PURPOSE: Histopathologic changes in human lacrimal gland were investigated, and the relation between histopathologic parameters and patient age and sex, as well as the histopathologic differences between palpebral and orbital lobes of the lacrimal gland were analyzed. METHODS: Samples of the main human lacrimal gland that included the palpebral lobes and orbital lobes were taken in 80 autopsies. A statistical analysis was made based on light microscope observations with the following histopathologic changes as parameters: (1) fibrosis (focal, lobular, and diffuse); (2) acinar atrophy (focal, lobular, and diffuse); (3) periductal fibrosis; (4) interlobular ductal dilatation; (5) interlobular ductal proliferation; (6) lymphocytic foci; (7) periductal lymphocytic infiltration; and (8) fatty infiltration. RESULTS: The incidences of these parameters in the palpebral and orbital lobes ranged from 3.8% to 35.0%. Lobular fibrosis, lobular atrophy, diffuse fibrosis, diffuse atrophy, periductal fibrosis, lymphocytic infiltration, and fatty infiltration were more frequent in the orbital lobes with statistical significance, whereas interlobular ductal dilatation was more frequent in the palpebral lobes. There were statistically significant correlations between age and diffuse fibrosis, diffuse atrophy, and periductal fibrosis in the orbital lobes of women, and periductal fibrosis in the palpebral lobes of men. Diffuse fibrosis and diffuse atrophy in the orbital lobes were observed more frequently in elderly women than in elderly men. CONCLUSIONS: Various histopathologic changes were observed in the human lacrimal gland. Diffuse fibrosis, diffuse atrophy, and periductal fibrosis predominantly found in elderly women suggested a relation with keratoconjunctivitis sicca in postmenopausal women. The authors speculate the periductal fibrosis is related to the decrease in tear fluid outflow with age and that interlobular ductal dilatation in the palpebral lobes may be caused by stenosis of the excretory duct in the fornix of conjunctiva. Ductal pathologic changes may be important in lacrimal gland dysfunction.

Adolescent↗
PubMed1995

Inhibitory effects of a bisphosphonate (risedronate) on experimental periodontitis in rats.

The present study was designed to examine whether systemic administration of a bisphosphonate, risedronate, could prevent alveolar bone resorption in rats with experimental periodontitis. On Day 1, an elastic ring was placed around the neck of the right mandibular 1st molar to induce inflammatory periodontitis. The animals were given daily injections of either 0.9% NaCl (control group), or 0.8, 1.6 or 3.2 mumoles/kg (s.c.) of risedronate (experimental groups) from Days 1 to 7, and were killed on Day 8. Histological examinations and determination of bone mineral density in the interdental area between the 1st and 2nd molars with an image analyzer revealed that the presence of the elastic ring induced a loss of attachment and bone resorption in the control group. Vigorous bone resorption, with appearance of a large number of osteoclasts, was observed in the interdental and bifurcation areas. In the experimental groups, however, the resorption of alveolar bone and the loss of bone mineral content in these areas were prevented in a dose-dependent fashion, especially at doses of 1.6 and 3.2 mumoles/kg. Many osteoclasts were detached from the surface of the alveolar bone and had degenerated appearances, such as rounded shapes, loss of polarity and pyknosis. These results suggest that administration of risedronate is effective in preventing bone resorption in periodontitis.

Alveolar Bone Loss↗
PubMed1995

Chimeric TLS/FUS-CHOP gene expression and the heterogeneity of its junction in human myxoid and round cell liposarcoma.

Myxoid liposarcomas have a unique and specific t(12;16)q13;p11) chromosomal translocation. The breakpoint has recently been identified and shown to involve the TLS/FUS gene on chromosome 16 and the CHOP gene on chromosome 12. This translocation causes fusion of these genes resulting in the expression of a novel chimeric TLS/FUS-CHOP message. Using the polymerase chain reaction with primer sets derived from sequences of TLS/FUS and CHOP cDNAs, we could amplify three types of the fusion transcripts from seven of seven samples of myxoid and round cell liposarcomas. In six of the seven positive samples, two kinds of chimeric messenger RNAs were found that have been reported previously. However, the last sample had a novel chimeric message that had an extra sequence of 33 bp derived from the TLS/FUS gene. Thus, it was shown that these fusion transcripts had a varying extent of the sequence of TLS/FUS gene incorporated at the site of the fusion. However, the TLS/FUS-CHOP fusion transcripts were not detected in two pleomorphic liposarcomas or in three myxoid variants of malignant fibrous histiocytomas. Our findings indicate that in liposarcomas TLS/FUS-CHOP fusion transcripts have variations at the junction of chimeric messages, which was the case for Ewing's sarcoma. Detection of the chimeric message by reverse transcription polymerase chain reaction was also suggested to be a useful approach for the diagnosis of myxoid and round cell liposarcomas that have (12;16) translocation, and for distinguishing them from pleomorphic liposarcoma and myxoid variant of malignant fibrous histiocytomas.

Adult↗
PubMed1995

Effect of clenbuterol on sulfur dioxide-induced acute bronchitis in guinea pigs.

When guinea pigs were exposed to sulfur dioxide (SO2) gas (800 ppm, 2 h), they showed hyperresponsiveness to intravenously administered serotonin (5-hydroxytryptamine (5-HT)). This hyperresponsiveness continued for over 24 h after the exposure to the gas. The degeneration, desquamation of epithelium, and edema of the lamina propria of the trachea and bronchi were observed in animals after a 2-h exposure of SO2 histopathologically. These changes seemed to be the early phase of acute bronchitis. Then, we examined the effect of clenbuterol, a selective beta-2 adrenoceptor agonist, on the SO2-induced bronchial hyperresponsiveness in these animals. Orally administered clenbuterol (1-10 micrograms/kg) suppressed the hyperresponsiveness to 5-HT in a dose-dependent manner. These results suggest that clenbuterol might inhibit the hyperresponsiveness that accompanies acute bronchitis and that this agent may be useful for remission of broncho-spasm.

Acute Disease↗
PubMed1995

Suppressive effect of clenbuterol on citric acid-induced cough reflex in guinea pigs.

We previously demonstrated that clenbuterol suppressed bronchial hyperresponsiveness in acute bronchitic models. However the effect of clenbuterol on the cough reflex, the main symptom of acute bronchitis, is not clear. The present study was thus undertaken to investigate the influence of clenbuterol on the cough reflex. Oral administration of clenbuterol (3 and 10 micrograms/kg) to guinea pigs markedly inhibited the increase in the respiratory resistance in response to 5-HT in a dose-dependent manner. At doses of 10 micrograms/kg and above, clenbuterol significantly inhibited the cough reflex induced by citric acid in guinea pigs. These doses are comparable with those causing broncho-dilation as described above, suggesting that the suppressive effect of clenbuterol on the cough reflex in guinea pigs may result from mainly its broncho-dilative action via stimulation of beta-2 adrenoceptors in airway smooth muscles however, other mechanisms cannot be ruled out. These results indicate that this agent may be useful for treatment of cough, the main symptom of acute bronchitis.

Airway Resistance↗
PubMed1994

Rab escort protein-1 is a multifunctional protein that accompanies newly prenylated rab proteins to their target membranes.

Rab proteins comprise a family of small GTPases that serve a regulatory role in vesicular membrane traffic. Geranylgeranylation of these proteins on C-terminal cysteine motifs is crucial for their membrane association and function. This post-translational modification is catalysed by rab geranylgeranyl transferase (Rab-GGTase), a multisubunit enzyme consisting of a catalytic heterodimer and an accessory component, named rab escort protein (REP)-1. Previous in vitro studies have suggested that REP-1 presents newly synthesized rab proteins to the catalytic component of the enzyme, and forms a stable complex with the prenylated proteins following the transfer reaction. According to this model, a cellular factor would be required to dissociate the rab protein from REP-1 and to allow it to recycle in the prenylation reaction. RabGDP dissociation inhibitor (RabGDI) was considered an ideal candidate for this role, given its established function in mediating membrane association of prenylated rab proteins. Here we demonstrate that dissociation from REP-1 and binding of rab proteins to the membrane do not require RabGDI or other cytosolic factors. The mechanism of REP-1-mediated membrane association of rab5 appears to be very similar to that mediated by RabGDI. Furthermore, REP-1 and RabGDI share several other functional properties, the ability to inhibit the release of GDP and to remove rab proteins from membranes; however, RabGDI cannot assist in the prenylation reaction. These data suggest that REP-1 is per se sufficient to chaperone newly prenylated rab proteins to their target membranes.

Alkyl and Aryl Transferases↗