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Biomedical subjects

T Oshima

Publications and source records attributed to T Oshima.

At least 181 records · Page 10Linked to original sources
PubMed1998

Expression of adhesion molecules in cultured human nasal mucosal microvascular endothelial cells activated by interleukin-1 beta or tumor necrosis factor-alpha: effects of dexamethasone.

Adhesion molecules of microvascular endothelial cells play a key role in the inflammatory processes involved in nonallergic sinusitis. We investigated the cytokine-regulated expression of intercellular adhesion molecule-1 (ICAM-1), E-selectin and vascular cell adhesion molecule-1 (VCAM-1), and the effect of dexamethasone on these expressions in cultured human nasal microvascular endothelial cells (HNMEC). ICAM-1 was enhanced, and E-selectin and VCAM-1 were induced in a dose-dependent fashion following stimulation with IL-1beta or TNF-alpha. HNMEC differed from human umbilical vein endothelila cells in that (1) maximal upregulation of ICAM-1 expression induced by IL-1beta or TNF-alpha required more time (2) TNF-alpha was more potent than IL-1beta in VCAM-1 expression, and (3) dexamethasone inhibited the upregulation of E-selectin expression alone. These findings contribute to a better understanding of the characteristic features of leukocyte infiltration into inflamed tissue and the effect of glucocorticoid in nonallergic chronic sinusitis.

Cell Adhesion Molecules↗
PubMed1998

Effect of 17beta-estradiol on inhibition of platelet aggregation in vitro is mediated by an increase in NO synthesis.

The low prevalence of coronary heart disease in premenopausal women and its increase after menopause are well established. Although estrogen is thought to play a role in protecting the vasculature, the mechanism has not been fully clarified. The contribution of platelets to atherosclerotic cardiovascular diseases is well recognized. The present study focused on the still-controversial effect of estrogen on platelet function. We investigated the in vitro effects of estrogen on human platelets, including their aggregation, Ca2+ metabolism, the synthesis of cyclic nucleotides, and NO (nitrite/nitrate) synthesis after stimulation with thrombin or ADP. Pretreatment of platelets with 17beta-estradiol reduced the platelet aggregation induced by thrombin or ADP, whereas 17alpha-estradiol had no effect. 17Beta-estradiol accelerated the recovery of [Ca2+]i after the agonist-induced peak and reduced the area under the curve of accumulated platelet [Ca2+]i but did not alter the baseline [Ca2+]i, Ca2+ influx induced by thrombin or ADP, the release of Ca2+ from internal stores, or the size of internal Ca2+ stores. Pretreatment of platelets with 17beta-estradiol had no effect on the intracellular concentration of cAMP but increased that of cGMP in agonist-stimulated platelets. Additionally, 17beta-estradiol increased the platelet concentration of nitrite/nitrate in a dose-dependent manner. These effects of 17beta-estradiol on platelet aggregation, Ca2+ metabolism, and NO synthesis were abolished by exposure to N(G)-monomethyl-L-arginine, an NO synthesis inhibitor. These results suggest that 17beta-estradiol plays an important role in inhibiting platelet aggregation by promoting Ca2+ extrusion or reuptake activity that is dependent on the production of cGMP by increasing NO synthesis.

Adult↗
PubMed1998

Angiotensin-converting enzyme inhibition, but not calcium antagonism, improves a response of the renal vasculature to L-arginine in patients with essential hypertension.

Endothelial function has been shown to be impaired in patients with essential hypertension. The purpose of the present study was to determine whether antihypertensive drug therapy improves impaired endothelium-dependent renal vasorelaxation in essential hypertensive patients without atherosclerosis. We evaluated the effects of intravenous infusion of L-arginine (500 mg/kg given over 30 minutes) on systemic and renal hemodynamics in 27 patients with mild to moderate essential hypertension who were randomly assigned to treatment with either the angiotensin-converting enzyme inhibitor imidapril or the calcium antagonist amlodipine for 12 weeks in a double-blind fashion. After the 12 weeks, the decrease in blood pressure was similar in the imidapril (n=14) and amlodipine (n=13) groups. The increase in renal plasma flow was also similar in both groups. L-Arginine-induced renovascular relaxation was increased by imidapril (renal plasma flow, 9.6+/-5.1% to 14.4+/-7.4%; renal vascular resistance, -10.4+/-8.1% to -16.7+/-9.2%, P<0.05, respectively) but not by amlodipine. Urinary excretion of nitrite/nitrate in response to L-arginine was significantly increased by imidapril (90+/-29% to 134+/-63%, P<0.05) but remained unchanged by amlodipine. These findings suggest that angiotensin-converting enzyme inhibition improves the impaired endothelium-dependent renovascular relaxation in patients with essential hypertension due to the increase in nitric oxide production and that the reduction in blood pressure with a calcium antagonist does not play a major role in the potentiation of L-arginine/nitric oxide-mediated effects.

Adult↗
PubMed1998

Cloning of the gene for inorganic pyrophosphatase from a thermoacidophilic archaeon, Sulfolobus sp. strain 7, and overproduction of the enzyme by coexpression of tRNA for arginine rare codon.

The gene encoding an extremely stable inorganic pyrophosphatase from Sulfolobus sp. strain 7, a thermoacidophilic archaeon, was cloned and sequenced. An open reading frame consisted of 516 base pairs coding for a protein of 172-amino acid residues. The deduced sequence was supported by partial amino acid sequence analyses. All the catalytically important residues were conserved. A unique 17-base-pair sequence motif was found to be repeated four times in frame in the gene, encoding a cluster of acidic amino acids essential for the function. Although the codon usage of the gene was quite different from that of Escherichia coli, the gene was effectively expressed in E. coli. Coexpression of tRNA(Arg), cognate for the rare codon AGA in E. coli, however, further improved the production of the enzyme, which occupied more than 85% of the soluble proteins obtained after removal of heat denatured E. coli proteins.

Amino Acid Sequence↗
PubMed1998

Surgical criteria for obstructive sleep apnea syndrome based on localization of upper airway collapse during sleep: a preliminary study.

Obstructive sleep apnea syndrome (OSAS) is defined as intermittent complete or partial upper airway obstruction during sleep, causing mental and physical effects. Localization of obstructions in the upper airways in OSAS patients provides indispensable information for the selection of surgical procedures. We measured the pressure within the upper airways during sleep in 6 patients with OSAS in order to select the surgical procedure. Five patients were found to have the airway collapse in the velopharynx, and in three of them underwent uvulopalatopharyngoplasty (UPPP) with tonsillectomy was performed. The remaining one patient, having an obstruction in both the velopharynx and hypopharynx, underwent laser-assisted midline glossectomy as well as UPPP. The 4 patients receiving the operation showed improvements in the sleep apnea index and the lowest oxygen saturation postoperatively. These findings suggest that pressure measurement may be a reliable tool for localizing obstructions in OSAS patients and may be used for determined the surgical option.

Adult↗
PubMed1998

A case of basal cell adenocarcinoma of the parotid gland.

We present a 73-year-old female with an enlarged mass in the right parotid gland. Fine-needle aspiration cytology suggested pleomorphic adenoma. Diagnostic imaging revealed that the tumour had a well-defined margin arising from the deep lobe of the parotid gland. A total parotidectomy with preservation of the facial nerve was performed. The final histopathological diagnosis including immunohistochemical studies was basal cell adenocarcinoma, which is a recently defined entity and a rare epithelial neoplasm. No sign of local recurrence or metastasis 24 months postoperatively has been observed.

Adenocarcinoma↗
PubMed1998

[Talc pulmonary granulomatosis caused by intravenous administration of methylphenidate].

A 57-year-old man was admitted with fever and a dry cough in 1985. He had used methylphenidate intravenously for 3 years. A chest X-ray film on admission showed diffuse micronodular shadows and massive lesions in the lower lung fields bilaterally. Pulmonary granulomatosis was diagnosed histologically, but the etiology remained unclear. In 1993, the patient was readmitted because of symptom exacerbation. The micronodular shadows had extended and the bilateral, massive lesions had enlarged. Transbronchial lung biopsy revealed granulomas with crystallized foreign bodies. Electron microscopy confirmed that the foreign bodies consisted of magnesium and silicon, suggesting talc. Talc granulomatosis caused by intravenous administration of methylphenidate was subsequently diagnosed. The symptoms improved with conservative treatment, and no signs of reexacerbation have appeared.

Central Nervous System Stimulants↗
PubMed1998

[Comparison of crossing-over between 30-minute drip infusion vs 30-second injection of granisetron for nausea and vomitting with cisplatin].

Recently, Granisetron (KYT) was proved to have a strong effect for cisplatin (CDDP)-induced emesis. We compared the effect of KYT for CDDP-induced emesis between two different administration schedules. Forty micrograms/kg of KYT was administered either by 30-minute drip infusion with 100 ml of saline (Group A) or 30-second injection with 10 ml of saline (Group B). We investigated the therapeutic effect of KYT in both group A and Group B by the crossing-over method. After the patients who had a malignant tumor and were going to receive CDDP (over 50 mg/m2) in two courses were selected, KYT was administered by the method of Group A or Group B in a double-blind comparison. The clinical efficacy was at least "effective" in 70% (7/10) of Group A and Group B. The study treatment was considered "useful" in 80% (8/10) of Group A, 90% (9/10) of Group B, and "safe" in 100% of Group A and B. There was no difference between two groups in this respect. The results showed that the slow intravenous injection of KYT also has an excellent antiemetic effect on CDDP-induced emesis and a high degree of safety.

Adult↗
PubMed1998

An active Ac-like transposable element in teleost fish.

The i4/i4 genotype of the medakafish, Oryzias latipes, exhibits a quasi albino phenotype due to insertion of a novel transposable element, Tol2, into the tyrosinase gene. Tol2 is 4681 bp in length, has short inverted terminal repeats, and contains four ORFs with the potential to encode a transposase protein. Excision activity of the element has been detected by PCR analysis. Genomic Southern of the Tol2 element revealed that about 20 copies are present in the diploid genome. Dot-matrix comparisons of amino acid sequences of ORFs show relatively high similarity with transposases from Ac of maize, hobo of Drosophila, and Tam3 of snapdragon, which are all active transposable elements. Tol2 is thus concluded to be an active Ac-like transposable element probably encoding a transposase protein. It should therefore find application as a unique material for establishing a gene tagging system in fish.

Journal Article↗
PubMed1997

A stable intermediate product of the archaeal zinc-containing 7Fe ferredoxin from Sulfolobus sp. strain 7 by artificial oxidative conversion.

Irreversible conversion of the purified zinc-containing 7Fe ferredoxin from the thermoacidophilic archaeon Sulfolobus sp. strain 7 was found to occur under aerobic conditions at pH 5.0 and at 4 degrees C. This process accompanied a substantial increase of the electron paramagnetic resonance signal attributed to a [3Fe-4S]1+ cluster, and the converted form containing approximately 6 Fe/Zn (mol/mol) had a net charge different from that of the native 7Fe ferredoxin. These data provide evidence for the formation of a stable intermediate product of the archaeal ferredoxin having two [3Fe-4S] clusters and a zinc center by artificial oxidative degradation. This further explains the discrepancy that a zinc center and two [3Fe-4S] clusters (but not a zinc center and one [3Fe-4S] cluster plus one [4Fe-4S] cluster) are observed in the crystal structure at pH 5.0.

Aerobiosis↗
PubMed1997

Lack of effect of transmembrane gradient of magnesium and sodium on regulation of cytosolic free magnesium concentration in rat lymphocytes.

The regulation of the intracellular concentration of Mg2+ ([Mg2+]i) is not fully understood. The level of Mg in lymphocytes is a good predictor of total body Mg status. We measured [Mg2+]i and total Mg in rat lymphocytes by using, respectively, the fluorescent Mg2+ indicator mag-fura-2 and atomic absorption spectrophotometry. The basal [Mg2+]i in rat lymphocytes was 328 +/- 23 micromol/l. An elevation to 5 mmol/l or the removal of extracellular Mg2+ did not affect [Mg2+]i. A reduction in extracellular Na+ did not influence [Mg2+]i for 60 min. The total Mg concentration in lymphocytes also remained stable. Results suggest that the permeability of the plasma membrane to Mg2+ is very low, and that Na+/Mg2+ exchange is not involved in the regulation of [Mg2+]i in rat lymphocytes.

Animals↗
PubMed1997

Expression and localization of the Na-K-2Cl cotransporter in the rat cochlea.

We identified the localization of the basolateral bumetanide-sensitive Na-K-2Cl cotransporter (BSC2) in the cochlea using an in situ hybridization method. In the rat cochlea, the BSC2 mRNA was mainly expressed in the strial marginal cells. Although the fibrocytes localized at the spiral prominence showed a weak expression of BSC2 mRNA, no expression was observed in the organ of Corti or spiral ganglion cells. The present findings are well consistent with a proposed cell model of ion transport in the marginal cell.

Animals↗
PubMed1997

Purification and characterization of isocitrate dehydrogenase from a hyperthermophilic archaebacterium, Caldococcus noboribetus.

Isocitrate dehydrogenase from a hyperthermophilic archaebacterium Caldococcus noboribetus produced in Escherichia coli was purified. The purification was performed by heat treatment at 80 degrees C followed by single column chromatography. N-terminal amino acid sequencing analysis revealed that the N-terminal methionine is removed from the purified enzyme. Gel filtration analysis suggests that the enzyme has a homodimeric structure with a molecular weight of 90,000. The isoelectric point of the enzyme was estimated to be 5.6 by isoelectric focusing electrophoresis. The circular dichroism spectrum suggests that the enzyme has a secondary structure consisting of 23% alpha-helix and 34% beta-sheet. Enzymatic activity was observed under neutral pH, and the highest specific activity was obtained using cacodylic acid-KOH (pH 7.0) buffer. MgCl2 or MnCl2 was essential for the activity, and KCl concentrations higher than 0.33 M had an inhibitory effect on it. Apparent Km values were 72 and 43 microM for D,L-isocitrate and NADP, respectively. The enzyme showed extremely high stability against heat treatment, and no activity loss was observed by the treatment at 80 degrees C. The specific activity of the enzyme increased as temperature rose. Nearly no activity was observed at 40 degrees C or lower.

Archaea↗
PubMed1997

Effect of polar side chains at position 172 on thermal stability of 3-isopropylmalate dehydrogenase from Thermus thermophilus.

To understand the role of the amino acid residue at position 172 in the conformational stability, four mutant enzymes of Thermus thermophilus 3-isopropylmalate dehydrogenase in which Ala172 was replaced with Asp, Glu, Asn, and Gln were prepared by site-directed mutagenesis. Three mutants were more stable than the wild-type enzyme. No significant change in catalytic properties was found in the mutant enzymes. The molecular modeling studies suggested that the enhanced thermostability of the mutant enzymes resulted from the formation of extra electrostatic interactions and/or improvement of hydrophobic packing of the interior core.

3-Isopropylmalate Dehydrogenase↗
PubMed1997

Extracellular Mg2+ inhibits capacitative Ca2+ entry in vascular smooth muscle cells.

BACKGROUND: Agonist-induced Ca2+ entry is thought to be mediated by capacitative Ca2+ entry other than L-type Ca2+ channels in vascular smooth muscle cells (VSMCs). The mechanism for capacitative Ca2+ entry has not been fully elucidated. Our objective was to examine the effect of external Mg2+ on capacitative Ca2+ entry in cultured rat aortic VSMCs. METHODS AND RESULTS: Three doses of external Mg2+ concentration (nominally 0, 1, and 5 mmol/L) were used. After exposure to 1 mumol/L, angiotensin II (Ang II) in Ca(2+)-free medium, addition of Ca2+ to the medium caused an increase in cytosolic free Ca2+ concentration ([Ca2+]i), indicating Ang II-induced Ca2+ influx. This Ca2+ influx was attenuated in cells preincubated with high external Mg2+ concentrations or with 1 mumol/L nifedipine. After VSMCs in Ca(2+)-free medium were exposed to 1 mumol/L thapsigargin, which inhibits the sarcoplasmic reticulum Ca(2+)-ATPase and depletes Ca2+ stores, addition of Ca2+ to the medium induced an increase in [Ca2+]i, indicating capacitative Ca2+ entry. This entry pathway was found to be independent of dihydropyridine-sensitive Ca2+ channels and inhibited by increased external Mg2+ concentration. External Mg2+ concentration did not influence Ca2+ efflux across the plasma membrane after stimulation with Ang II plus thapsigargin. CONCLUSIONS: Results suggest that in VSMCs, capacitative Ca2+ entry is reduced by external Mg2+. This mechanism may explain in part the inhibitory effect of external Mg2+ on Ca2+ handling.

Angiotensin II↗
PubMed1997

Alternatively spliced isoforms of the Na+/Ca2+ exchanger in the guinea pig cochlea.

The cochlea has been suggested to express some Na+/ Ca2+ exchangers (NCX), since efficient acoustic transduction requires cytosolic calcium homeostasis. The present study revealed that several spliced isoforms of NCX are expressed in the guinea pig cochlea. Moreover, to determine their localization in the cochlea, microdissected RT-PCR was performed. The guinea pig cochlea was microdissected into three parts (lateral wall, the organ of Corti and modiolus). The cochlear lateral wall and the organ of Corti expressed only a single isoform of NCX1. On the other hand, five isoforms of NCX1 and four isoforms of NCX3 were detected in the cochlear modiolus. The alternative splicing may provide diverse functions for NCX in the cochlea.

Alternative Splicing↗