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T Oshima

Publications and source records attributed to T Oshima.

At least 163 records · Page 9Linked to original sources
PubMed1998

Serial increase in the thermal stability of 3-isopropylmalate dehydrogenase from Bacillus subtilis by experimental evolution.

We improved the thermal stability of 3-isopropylmalate dehydrogenase from Bacillus subtilis by an in vivo evolutionary technique using an extreme thermophile, Thermus thermophilus, as a host cell. The leuB gene encoding B. subtilis 3-isopropylmalate dehydrogenase was integrated into the chromosome of a leuB-deficient strain of T. thermophilus. The resulting transformant showed a leucine-autotrophy at 56 degrees C but not at 61 degrees C and above. Phenotypically thermostabilized strains that can grow at 61 degrees C without leucine were isolated from spontaneous mutants. Screening temperature was stepwise increased from 61 to 66 and then to 70 degrees C and mutants that showed a leucine-autotrophic growth at 70 degrees C were obtained. DNA sequence analyses of the leuB genes from the mutant strains revealed three stepwise amino acid replacements, threonine-308 to isoleucine, isoleucine-95 to leucine, and methionine-292 to isoleucine. The mutant enzymes with these amino acid replacements were more stable against heat treatment than the wild-type enzyme. Furthermore, the triple-mutant enzyme showed significantly higher specific activity than that of the wild-type enzyme.

3-Isopropylmalate Dehydrogenase↗
PubMed1998

DD genotype of the angiotensin I-converting enzyme gene is a risk factor for early onset of essential hypertension in Japanese patients.

Although angiotensin-converting enzyme (ACE) plays an important role in blood pressure regulation, no relationship between the insertion/deletion (I/D) polymorphism of the ACE gene and essential hypertension has been observed. However, as the pathogenesis and genetic background of essential hypertension are heterogeneous, we investigated whether the ACE gene is a marker of subgroups of patients with essential hypertension. A group of 178 patients with essential hypertension (90 men/88 women; 53 +/- 13 years of age, mean age +/- SD ) and 101 normotensive control subjects (54 men/47 women; 51 +/- 14 years of age, mean age +/- SD ) were included in the study. The allele frequencies of the two groups were similar. There were no differences in age, blood pressure, retinopathy grade, presence of proteinuria, or resting plasma renin activity (PRA) among the hypertensive patients with the II, ID, and DD genotypes. However, the age of onset of hypertension of patients with the DD genotype was lower (p < 20.05) and their left ventricular mass index was higher (p < 2 0.05) than those in patients with the non-DD genotype. These data suggest that the I/D polymorphism of the ACE gene is associated with an early onset of hypertension and left ventricular hypertrophy in Japanese patients with essential hypertension.

Adult↗
PubMed1998

GABAergic inhibition of hiccup-like reflex induced by electrical stimulation in medulla of cats.

We hypothesize that the hiccup reflex is actively inhibited through GABA(B) receptor within central connections of the hiccup reflex arc. Because the hiccup-like reflex can be elicited by electrical stimulation to a limited area within the medullary reticular formation, the hiccup-evoking site (HES), electrical stimulation (50-100 microA, three train pulses at 20 Hz) was delivered to HES by means of a metal electrode containing 1.0 mM baclofen, in anesthetized spontaneously breathing cats. The evoked response was characterized by a brief powerful increase in diaphragmatic activity and a temporal suppression of the posterior cricoarytenoid muscle, laryngeal dilator, which corresponded to the fixed motor pattern of hiccup reflex. The hiccup-like response was rapidly suppressed after microinjection of baclofen (0.1-0.5 nmol) into HES, indicating that HES has GABA(B) receptors. In the other experiments, to histologically examine the inputs to the hiccup reflex arc, unconjugated cholera toxin subunit B (UCTB) was injected into HES. Following injections of UCTB, retrogradely labelled cells were found distributed in various areas of the lower brainstem. Among these areas, the nucleus raphe magnus (RM) is reported to have GABA-containing cells. It is thus hypothesized that RM is most likely to be the source of the GABAergic inhibitory inputs to the hiccup reflex arc.

Animals↗
PubMed1998

Midfacial degloving approach facilitated by endoscope to the sinonasal malignancy.

Midfacial degloving is known to provide excellent exposure of the central compartment of the anterior and middle cranial fossae without facial incisions. In this study, an endoscope was adapted for midfacial degloving technique in the medial maxillectomy with ethmoidectomy in five patients with sinonasal malignancy. Meticulous and safe manipulation in the medial and inferior aspect of the orbit, sphenoid sinus and olfactory fossa can be obtained by endoscopic management without serious complications. This procedure, employing an endoscope, offers accurate and safe resection of selected cases with the sinonasal malignancy.

Adult↗
PubMed1998

Amino acid formation in gas mixtures by high energy particle irradiation.

Amino acids were formed from carbon monoxide, nitrogen and water, which are possible constituents of the primitive earth's atmosphere, by irradiation with high energy particles (components of cosmic rays). Glycine yield was proportional to the total energy deposited to the gas mixture, and its G-value was as high as 0.02 when the carbon monoxide/nitrogen ratio was 1. Based on an estimate of the effective energies of various types of energy sources available in the primitive earth's atmosphere for amino acid synthesis, it is suggested that cosmic rays were one of the most important energy sources for the synthesis of amino acids on the primitive earth.

Amino Acids↗
PubMed1998

A2 adenosine receptors in Mongolian gerbil middle ear epithelium and their regulation of Cl- secretion.

The present study investigates the effects of adenosine and its analogues on Cl- secretion in primary cultures of gerbil middle ear epithelium. Short-circuit current (Isc), an index of transepithelial active transport, was measured on the same cells cultured on porous filters. Baseline Isc and transepithelial resistance were 27.0 +/- 0.7 microA cm-2 and 275 +/- 7 omega cm2, respectively (n = 178). Extracellular adenosine and its analogues elicited a sustained increase in Isc when added to apical or basolateral surfaces. Both the A2A selective agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido adenosine and the A2A/A2B nonselective agonist 5'-(N-ethyl-carboxamido)adenosine (NECA) increased Isc, but NECA was more effective than CGS21680. A1 selective antagonist 8-cyclopentyl-1,3-dipropylxanthine did not reduce NECA-induced Isc. These results suggest the presence of both A2A and A2B receptors. NECA did not stimulate a rise in the intracellular Ca2+ concentration ([Ca2+]i) in single middle ear epithelial cells cultured on glass coverslips. Dibutyryl cAMP (dbcAMP) induced an initial transient increase in Isc followed by the sustained plateau. Addition of dbcAMP also caused a transient increase in [Ca2+]i. The protein kinase A inhibitor, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide, greatly reduced the increase in the Isc responses to NECA. 1,2-Bis-(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid-acetoxymethyl ester influenced neither the NECA-induced increase in Isc nor the dbcAMP-induced sustained phase of Isc, but greatly inhibited the dbcAMP-induced transient increase in Isc. Glibenclamide, a cystic fibrosis transmembrane conductance regulator (CFTR) channel inhibitor, reduced the NECA-induced Isc. These results indicate that extracellular adenosine and its analogues activate the cAMP-protein kinase A system, but not intracellular Ca(2+)-dependent mechanisms, leading to Cl- secretion, possibly through the CFTR Cl- channels in the cultured gerbil middle ear epithelium.

Adenosine↗
PubMed1998

Selective neutrophil depletion with monoclonal antibodies attenuates ischemia/reperfusion injury in skeletal muscle.

The purpose of this study was to determine whether depletion of circulating neutrophils, using an antineutrophil monoclonal antibody (RP3), would attenuate ischemia/reperfusion injury in rat skeletal muscle. A 3- and 5-hr period of ischemia was induced unilaterally into the hindlimbs of rats; the isolated limbs were then reperfused for 24 hr after ischemia. The gastrocnemius muscle was then removed, and blood was taken simultaneously. The hematologic parameters were measured, muscle neutrophil sequestration was assessed by myeloperoxidase (MPO) activity, free radical production was evaluated by the tissue lipid peroxides (LPO) levels, muscle viability was assessed by tissue levels of adenosine triphosphate (ATP) and creatine phosphate (PCr) levels, and muscle wet/dry weights were determined. Treatment with RP3 selectively and sufficiently depleted the circulating neutrophil population, markedly reduced MPO, and significantly attenuated LPO and the tissue water content after both 3- and 5-hr of ischemia. After 3 hr of ischemia, ATP and PCr levels were significantly increased by neutrophil depletion; however, after 5 hr of ischemia, the same effect was not demonstrated. These results suggest that neutrophil depletion after 3 hr of ischemia restrains free radical production and edema formation, and also attenuates skeletal muscle ischemia reperfusion injury; however, after 5 hr of ischemia, ischemic damage was so severe, that neutrophil depletion did not reduce ischemia reperfusion injury.

Adenine Nucleotides↗
PubMed1998

Mitochondrial DNA deletion is a predisposing cause for sensorineural hearing loss.

Composed of a postmitotic stable tissue, the inner ear is a target organ for mitochondrial DNA (mtDNA) mutation. To determine whether mtDNA mutation is a predisposing factor in patients with sensorineural hearing loss (SNHL), the authors assessed the mtDNA4977 deletion from 60 patients with SNHL and 47 normal control subjects. All cases had no past history of ototoxic or noise exposure, middle ear disease, or other known etiological factors for SNHL. DNA specimens extracted from peripheral blood leukocytes were used for detection of mtDNA4977 deletion by polymerase chain reaction. Patients with SNHL had a significantly higher rate of the mtDNA4977 deletion than did controls (75% vs. 30%, P < 0.0001). The detection rate of mtDNA4977 deletion was significantly increased with the deterioration of the hearing threshold. Aging did not influence the detection rate of mtDNA4977 deletion in either the control or SNHL group. The authors have described high detection rates of the mtDNA4977 deletion in patients with idiopathic bilateral SNHL and propose that at least some of the advanced SNHL cases should be categorized as mitochondrial oxidative phosphorylation diseases. This inference would offer novel possibilities for treatment and prevention of SNHL including presbycusis.

Adult↗
PubMed1998

Increased cytosolic free Mg2+ and Ca2+ in platelets of patients with vasospastic angina.

This study was designed to test the hypothesis that the cellular metabolism of Ca2+ and Mg2+, which is important in platelet function, is abnormal in the platelets of patients with vasospastic angina. Cytosolic free Mg2+ concentration ([Mg2+]i) and Ca2+ handling were determined in the platelets of 24 patients with vasospastic angina and 24 control subjects by use of mag-fura 2 and fura 2. Platelet aggregation was also examined. Basal [Mg2+]i and cytosolic free Ca2+ concentration ([Ca2+]i) in platelets were significantly higher in patients with vasospastic angina than in control subjects. The amplitude of the [Ca2+]i transient induced by thrombin (0.03-1.0 U/ml) was significantly increased in the presence, but not in the absence, of extracellular Ca2+ in patients with vasospastic angina, as compared with controls. Therefore, the influx of Ca2+ across the plasma membrane may be accelerated in vasospastic angina. Thrombin (0.1-1.0 U/ml)-induced maximum aggregation response was significantly greater in patients with vasospastic angina than in controls. Results suggest that increased [Mg2+]i and altered Ca2+ handling by platelets may be associated with coronary vasospasm.

Adenosine Diphosphate↗
PubMed1998

Abnormal platelet Ca2+ handling accompanied by increased cytosolic free Mg2+ in essential hypertension.

To test the hypothesis that abnormal platelet Ca2+ handling in essential hypertension results from cellular Mg2+ deficiency, cytosolic free Mg2+ concentration ([Mg2+]i) and Ca2+ metabolism were studied in mag-fura 2 and fura 2-loaded platelets from 30 essential hypertensive patients and 30 sex- and age-matched normotensive controls. Basal cytosolic free Ca2+ concentration ([Ca2+]i) and intracellular Ca2+ discharge capacity were higher in hypertensives than in normotensives (22 +/- 5 vs. 18 +/- 5 nM, P < 0.05; 743 +/- 250 vs. 624 +/- 144 nM, P < 0.05, respectively). The thrombin (0. 03-1.0 U/ml)-evoked [Ca2+]i response was also enhanced in platelets from hypertensives in both the absence and presence of extracellular Ca2+. However, basal [Mg2+]i was higher in hypertensives than in normotensives (437 +/- 110 vs. 353 +/- 85 microM, P < 0.05), whereas serum Mg2+ was similar in the two groups. These results oppose the Mg2+ deficiency hypothesis in platelets in essential hypertension.

Blood Platelets↗