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Biomedical subjects

O Yamamoto

Publications and source records attributed to O Yamamoto.

At least 19 recordsLinked to original sources
PubMed1996

Functional assessment of two vitamin D-responsive elements in the rat 25-hydroxyvitamin D3 24-hydroxylase gene.

Two vitamin D-responsive elements (VDRE-1 and VDRE-2) were recently identified in the 5'-upstream region of the rat 25-hydroxyvitamin D3 24-hydroxylase gene at -151/-137 and -259/-245, respectively. We studied the transcriptional regulation of this gene by vitamin D by means of mutational analysis. Introducing mutations into VDRE-1 and VDRE-2 in the native promoter -291/+9 reduced vitamin D-dependent chloramphenicol acetyltransferase activity by 86 and 41%, respectively. Mutation of the direct repeat -169/-155 located at 3 base pairs upstream of VDRE-1 also caused 50% decrease of chloramphenicol acetyltransferase activity. Connection of the element -169/-155 to VDRE-1 enhanced the vitamin D responsiveness of VDRE-1 5-fold through the heterologous beta-globin promoter. The fragment -291/-102 containing the two VDREs showed two shifted bands in the presence of the vitamin D receptor and retinoid X receptor in gel retardation analysis, and the appearance of the slower migrating band indicates that two sets of receptor complexes bind to this fragment simultaneously. These results demonstrate that VDRE-1 is a stronger mediator of vitamin D function than VDRE-2 due to the presence of the accessory element -169/-155 located adjacent to VDRE-1, although VDRE-2 exhibits a smaller dissociation constant for the vitamin D receptor-retinoid X receptor complex than VDRE-1.

Animals↗
PubMed1996

A phylogenetic study of Rubrobacter radiotolerans by sequence analysis of the 16S ribosomal RNA gene.

Partial sequence of the 16S ribosomal RNA gene of an extremely high radiotolerant bacterium, Rubrobacter radiotolerans (reclassified from Arthrobacter radiotolerans by chemical characteristics) was determined by PCR-amplification from a small amount of heat-lysed biomass, followed by direct sequencing of the PCR product. The sequence was aligned with seven species of Arthrobacter and also with representatives of various other bacterial groups. R. radiotolerans was confirmed to be out of the Arthrobacter group justifying the reclassification. Moreover, it has an individual position among the selected representatives being closer to the eubacterial groups.

Arthrobacter↗
PubMed1996

A low grade scirrhous carcinoma of eccrine gland origin in adolescence.

We report a rare occurrence of adnexal carcinoma in an adolescent. A 17-year-old Japanese girl had a gradually enlarging tumor on the elbow. Histopathologically, the exophytic tumor showed asymmetrical lobules of tumor embedded in a thickened collagenous stroma. The lobules were composed of various patterns of tumor cell nests ranging from tubular to solid forms. Invasive growth patterns were also observed in the stroma. Two types of the cells, cuboidal and elliptically polygonal, were noted. Immunohistochemistry revealed the presence of S-100 protein and cytokeratin 8 and the absence of gross cystic disease fluid protein-15 in the tumor cells. Electron microscopic observation showed a ductal or glandular differentiation and fragmented basal laminae around the nests. Light and electron microscopic findings of this tumor are suggestive of a low-grade sweat gland carcinoma.

Adenocarcinoma, Scirrhous↗
PubMed1996

Contact hypersensitivity is suppressed after sensitisation by dinitrofluorobenzene of early stage iso-skin grafts.

Isologous free skin grafts were applied to the backs of BALB/c mice and contact hypersensitivity studied by epicutaneous application of DNFB (2,4-dinitro-1-fluorobenzene) to the grafted skin. In the first experiment, the grafted skin was sensitised and the elicitation reaction assessed by measuring the ear swelling after five days. Sensitisation was not successful until two weeks after grafting. In such non-responding animals, re-sensitisation with DNFB on the ungrafted skin area was also unsuccessful, indicating the establishment of immunological tolerance. This tolerance was considered antigen-specific, as re-sensitisation with oxazolone was successful. In the second experiment, spleen cell suspension, both untreated and treated in vitro with antiThy 1.2, antiLyt 1.2, and antiLyt 2.2 antibody, from non-DNFB-responding mice was transferred into normal mice. Subsequently these mice were sensitised with DNFB. Sensitisation was not successful in the untreated group or in those treated with antiLyt 1.2 antibody. On the other hand, the groups treated with antiThy 1.2 and antiLyt 2.2 antibody did become sensitised. These results indicate that the unsuccessful delayed hypersensitivity of the grafted skin was caused by suppressor T cells. In addition, the density of epidermal Langerhans cells was reduced in the early stages of skin grafting and morphological abnormalities were present. From these results, we conclude that contact sensitisation during the early stage of grafting skin not only produces suppression of ear swelling but also induces antigen-specific tolerance. These results also suggest that the suppression depends on the antigen-specific suppressor cells and that acquirement of tolerance is associated with a reduction in the number of epidermal Langerhans cells in the grafted skin and abnormalities in their structure.

Adjuvants, Immunologic↗
PubMed1995

The use of an ileostomy connector to diminish the frequency of defecation prior to ileostomy closure in patients with a pelvic pouch.

A new method for allowing stool passage into the pelvic pouch before ileostomy closure to verify the defecation state and diminish stool frequency is reported herein. This was accomplished by fitting an ileostomy connector connecting the proximal and distal openings of the diverting loop stoma. The ileostomy connector was initially in place for 6 h a day, the length of time being gradually increased until it was able to be left in for 24 h a day over a 3-month period. The calculated daily frequency of stools decreased from 24 to 6 or 7 times, and the mean daily frequency immediately after ileostomy closure was 6.5 times. Physiological study also showed an improvement, with squeeze pressure increasing from 35 cmH2O to 116 cmH2O and the maximum tolerated volume increasing from 35 ml before, to 90 ml 3 months following the use of an ileostomy connector. Thus, we conclude that an ileostomy connector may be useful to predict postoperative functional outcome and its complications, and to diminish the frequency of defecation before ileostomy closure in patients with a covering loop stoma.

Adult↗
PubMed1995

Technetium-99m tetrofosmin and technetium-99m sestamibi imaging of multiple metastases from differentiated thyroid carcinoma.

A 79-year-old male with follicular thyroid carcinoma metastasizing to the lung, bone and lymph nodes was subjected to whole-body scintigraphy using technetium-99m tetrofosmin and 99mTc-sestamibi. Both agents delineated the metastatic lesions and the two image qualities were comparable. We believe that 99mTc-tetrofosmin and 99mTc-sestamibi images may be helpful in localizing metastatic foci and substitute for thallium-201 in the follow-up of patients with differentiated thyroid carcinoma.

Adenocarcinoma, Follicular↗
PubMed1995

Stimulatory mechanism of EM523-induced contractions in postprandial stomach of conscious dogs.

BACKGROUND & AIMS: EM523, a motilin agonist, is intended to be used as a gastroprokinetic during the postprandial period, but the mechanism(s) by which EM523 stimulates postprandial contractions in the stomach has not been studied before. The aim of this study was to examine the mechanism of contraction-stimulating activity by EM523 in fed dogs. METHODS: Contractile activity in the gastric antrum of 5 dogs was monitored using a long-term implanted force transducer and measured by integrating the area under the curve. Test materials were continuously infused or injected intravenously. RESULTS: EM523 (1-30 micrograms/kg) induced a dose-dependent increase in fed-type contractions. EM523-induced contractile activity was partially inhibited by atropine, hexamethonium, dopamine, 5-hydroxytryptamine 3 (5-HT3) receptor antagonist, and substance P antagonist. Atropine-resistant and EM523-induced contractions were further inhibited by 5-HT3 receptor antagonist and substance P antagonist, and the combined use of the two antagonists completely eliminated the atropine-resistant and EM523-induced contractions. CONCLUSIONS: EM523-induced contractions in the fed stomach are quite different from phase III contractions in the fasted state and are mediated partially through the cholinergic pathway. The noncholinergic pathway involves 5-HT3 and neurokinin 1 receptors.

Animals↗
PubMed1995

Oral administration of tritiated water (HTO) in mouse. II. Tumour development.

Previously we reported haematopoietic death as an effect of tritiated water (HTO) in drinking water in the concentration range from 5.92 x 10(11) to 1.85 x 10(10) Bq/dm3. In the present study the effects of HTO in a lower concentration range from 9.25 x 10(9) Bq/dm3 (0.240 Gy/day) to 3.70 x 10(8) Bq/dm3 (0.096 Gy/day) are reported. Female (C57BL/6N and C3H/He)F1 mice were maintained on drinking water containing various levels of HTO. Mice survived for > 150 days with a high incidence of tumour development (70 to 80%). In the dose-rate range from 9.25 x 10(9) Bq/dm3 (0.240 Gy/day) to 1.85 x 10(9) Bq/dm3 (0.048 Gy/day) the main cause of death was thymic lymphoma. However, at a dose-rate of 9.25 x 10(8) Bq/dm3 (0.024 Gy/day) the incidence of thymic lymphoma sharply decreased, while the incidence of other tumours increased. The tumour type became more diverse at lower concentrations of HTO. The latent period of tumour development was shorter and the life-shortening effect was more marked by 3H beta-irradiation in this study than b X- or gamma-irradiation reported in other investigations.

Administration, Oral↗
PubMed1995

Keratinocyte degeneration in human facial skin: documentation of new ultrastructural markers for photodamage and their improvement during topical tretinoin therapy.

We examined epidermal impairment in photodamaged Caucasian skin by light and electron microscopy and observed two types of degeneration of the basal and suprabasal keratinocytes. The first was an electron-lucent degeneration predominantly seen in the periphery of the cells. The marked lucent degeneration occurred in 14% of the basal and suprabasal keratinocytes, predominantly in cells immediately adjacent to melanocytes. In skin specimens with a large number of such damaged keratinocytes, bleb-like keratinocytic protrusions or electron-lucent intercellular structures were also seen. Many vacuolar structures were observed just under the dermoepidermal junction, occupying 9% of the junction length. These structures were produced by herniation of the degenerative portion of the basal and suprabasal keratinocytes, and appeared to be phagocytized by dermal macrophages. The vacuolar alterations in the basal layer and dermoepidermal junction previously reported at the light microscopic level probably represent these intercellular lucent structures, bleb-like protrusions and vacuole-like structures at the electron microscopic level. The second type, dark-staining keratinocytes, probably representing an extensive degenerative process, constituted 4% of the basal and suprabasal keratinocytes. After 12 months of topical tretinoin treatment, dramatic improvement of both degenerative processes of the keratinocytes was noted.

Administration, Cutaneous↗
PubMed1995

Ultrastructural effects of topical tretinoin on dermo-epidermal junction and papillary dermis in photodamaged skin. A controlled study.

We examined the effects of daily topical application of 0.05% tretinoin cream on photodamaged Caucasian facial skin by electron microscopy. Specimens obtained pretreatment, after 6 and 12 months of tretinoin therapy (20 patients), and after 6 months of vehicle treatment (5 patients) were compared in a blinded fashion, with special attention to the dermoepidermal junction and papillary dermis. Baseline specimens disclosed various degrees of damage including reduplication of basal lamina, smudging and sparsity of collagen fibers, and nodular arrangement of degenerated microfibrils in the papillary dermis. No significant changes were observed at 6 months in the papillary dermis of either tretinoin-treated or vehicle-treated patients. After 12 months of tretinoin treatment, however, disorganized collagen fibers, which were conspicuous in 11 patients at baseline, were replaced by new well-organized collagen fibers in a wavy pattern in 6 patients. In addition, the amount of nodularly degenerated microfibrillar material decreased in 15 of 18 patients with this finding at baseline. In contrast, no significant change was noted in the number of anchoring fibrils per unit length of the lamina densa. These observations provide further evidence that topical treatment with 0.05% tretinoin produces papillary dermal reconstruction, for which more than 6 months of application were required.

Administration, Topical↗
PubMed1995

Mechanism for lowering blood ammonia levels by lactitol.

Lactitol has been reported to decrease the blood ammonia concentration in various experimental hyperammonemia models such as portacaval shunted rats. The mechanism responsible for this lowering of blood ammonia levels was investigated in rats. When lactitol was given orally twice a day for 7 days at doses of 3 and 10 g/kg/day and at half that daily dose on day 8, it significantly decreased the ammonium concentration of the portal blood by 27.3-43.2%, cecal ammonia contents by 49.2-57.6% and the pH of the cecal contents from 6.52 to 5.92-5.54, 4 hr after the final administration. Lactitol also inhibited increases in the portal ammonia concentration induced by the intracecal administration of ammonium acetate (300 mg/kg) 4 hr after the final administration. When lactitol was given orally at bolus doses of 1 and 3 g/kg simultaneously with a charcoal meal, lactitol significantly facilitated small intestinal transit by 12-13%. At a bolus dose of 3 g/kg, given 1 hr before the administration of a charcoal meal into the proximal colon, lactitol significantly facilitated colonic transit by 29.5%. These effects of lactitol were similar to those of lactulose. These findings suggest that lactitol decreases blood ammonia concentration by inhibiting both the production and the absorption of ammonia through reducing intestinal pH and shortening the residence time of intestinal contents in the intestinal tract.

Acetates↗
PubMed1995

Enzyme-linked immunosorbent assay for serum apolipoprotein B-100, a major triglyceride-transport protein in dairy cows.

An ELISA was developed to determine serum concentration of apolipoprotein B-100, a major triglyceride-binding protein in very low-density lipoproteins and a putative maker for hepatic lipidosis of dairy cows. Serum apolipoprotein B-100 was prepared electrophoretically, and antibodies to this protein were raised in rabbits. The antiserum prepared was further purified by affinity chromatography, using bovine serum albumin-Sepharose 4B, to remove antibodies to albumin. For the ELISA, addition of 2-mercaptoethanol to the coating buffer (50 mM sodium carbonate, pH 9.6) was required to evaluate apolipoprotein B-100 concentration in serum. The ELISA developed was sensitive (detection limit was 300 to 400 ng/ml of serum) and reliable (coefficients of variance were in the range of 3.3 to 7.6%). By use of the established ELISA, the serum apolipoprotein B-100 concentration was found to be significantly (P < 0.01) lower during the early lactating stage than during other stages of lactation. Reduced hepatic synthesis or secretion of apolipoprotein B-100 during the early lactating stage, together with the excess uptake by the liver of serum nonesterified fatty acids, is suggested to be relevant in the accelerated accumulation of triglycerides in the liver of dairy cows during the periparturient period.

Animals↗
PubMed1994

Inhibition of phase III activity by acid in canine stomach.

Very few phase III activity of the interdigestive migrating contractions (phase III) occurs in the stomach of fasted duodenal ulcer patients. But the mechanism is not well understood. In this study, we studied the effect of gastric and duodenal acidification on the spontaneous phase III activity in the upper gastrointestinal tract of conscious dogs. Gastric and duodenal motor activity in 5 conscious dogs was monitored by means of chronically implanted force transducers. Intragastric pH changes were measured by placing a pH glass electrode in the gastric antrum. Intragastric and intraduodenal acidification was achieved by i.v. infusion of histamine, and by intragastric and intraduodenal instillation of acidic solutions of different pHs. The plasma motilin concentrations were measured by radioimmunoassay. Histamine (40 micrograms/kg/h) inhibited spontaneous phase III activity, but the histamine-induced inhibition was completely prevented by pretreatment with famotidine, a potent histamine H2 receptor antagonist (0.3 mg/kg, i.v.). Intragastric acidification at pH 1.0 strongly inhibited spontaneous phase III activity, but an acidic solution at pH 2.0 had no effect in inhibiting phase III activity. Intraduodenal acidification at pH 1.0 also inhibited spontaneous phase III activity. Histamine injection and gastric and duodenal acidification at pH 1.0 strongly suppressed motilin release. It is concluded that gastric and duodenal acidification at pH 1.0 inhibits the occurrence of the spontaneous phase III activity, and the suppression of endogenous release of motilin due to gastric and duodenal acidification at pH 1.0 is involved in this inhibitory mechanism.

Animals↗
PubMed1994

Identification of a vitamin D-responsive element in the 5'-flanking region of the rat 25-hydroxyvitamin D3 24-hydroxylase gene.

The 5'-flanking region of the rat vitamin D3 24-hydroxylase (P450cc24) gene was examined and a vitamin D-responsive element (VDRE) responsible for the 1 alpha,25-dihydroxyvitamin D3 (1,25-(OH)2D3) enhancement was identified. Unidirectional deletion analyses of the 5'-flanking region indicated that the region [-167/-102] is involved in vitamin D responsiveness. Further functional analyses showed that the segment [-204/-129] conferred the hormone responsiveness in an orientation-independent manner when it was placed upstream to the heterologous thymidine kinase promoter or the rabbit beta-globin promoter. The segment [-204/-129] contained two direct repeat motifs homologous to other VDREs found in the osteocalcin and osteopontin genes. Synthetic oligonucleotides containing the putative VDRE were used for functional analyses and gel mobility shift assays. The proximal [-151/-137], but not the distal [-169/-155] direct repeat activated the transcription in response to 1,25-(OH)2D3 through the beta-globin promoter. Furthermore, the proximal direct repeat formed a complex with the vitamin D receptor and a nuclear accessory factor(s) from COS cells (or retinoid X receptor) in the presence of 1,25-(OH)2D3. These results indicate that a direct repeat motif, AGGTGAgt-gAGGGCG, located at -151 base pairs upstream in the antisense strand binds to a heterologous dimer consisting of the VDR occupied with 1,25-(OH)2D3 and the nuclear accessory factor and that it plays a critical role in mediating the vitamin D enhancement of the rat P450cc24 gene expression.

Animals↗