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Biomedical subjects

T Oshima

Publications and source records attributed to T Oshima.

At least 343 records · Page 19Linked to original sources
PubMed1993

An ecto-enzyme from Sulfolobus acidocaldarius strain 7 which catalyzes hydrolysis of inorganic pyrophosphate, ATP, and ADP: purification and characterization.

Membranes of Sulfolobus acidocaldarius, a thermoacidophilic archaebacterium, show novel enzymatic activities to hydrolyze PPi, ATP, and ADP at an optimal pH of 3, equal to the growth optimum. The activity increased by about 2-fold on addition of PPi and/or Pi to the growth medium, when yeast extract and casamino acids were removed. The enzyme which hydrolyzes PPi at pH 3 was solubilized and purified by successive chromatographies. The final preparation showed a 26 kDa single band on SDS-PAGE, and a molecular mass of 35 kDa on gel permeation chromatography. The Km and Vmax for PPi were 0.16 mM and 33 mumol Pi released/min/mg at 55 degrees C. ATP and ADP were also good substrates. Divalent cations were not essential for activity. Substrate inhibition at more than 5 mM PPi, ATP or ADP was observed. AMP, glucose-6-phosphate, and p-nitrophenyl phosphate were not hydrolyzed at all. The activity was 4-fold stimulated by addition of the lipid fraction extracted from the organism.

Adenosine Diphosphate↗
PubMed1993

Effects of novel polyamines on cell-free polypeptide synthesis catalyzed by Thermus thermophilus HB8 extract.

Effects of novel, naturally occurring polyamines on protein synthesis catalyzed by Thermus thermophilus cell-free extract were investigated. The results revealed the physiological importance of a branched quaternary polyamine, tetrakis(3-aminopropyl) ammonium, in thermophile protein biosynthesis. Longer polyamines than triamine supported the polypeptide synthesis at high temperature, though both the activity and the optimum temperature varied depending on polyamines added. The highest activity was found when tetrakis(3-aminopropyl)ammonium and a tetraamine were simultaneously present. The optimum temperature of the reaction supported by the combination of the branched polyamine and spermine was the highest and in accord with the optimum temperature of the bacterial growth. These results suggested an essential role of the quaternary amine in protein synthesis in vivo. This amine effectively stabilized the ternary complex between ribosomes, the messenger, and phenylalanyl-tRNA, and this stabilization may account, at least in part, for its action on the present reaction. In contrast, another branched polyamine, tris(3-aminopropyl)amine supported the activity only moderately even in the presence of another polyamine, though the tris amine stabilized the ternary complex as effectively as the quaternary amine. This result suggests the presence of another essential site for polyamine action in the thermophile polypeptide synthesis, in addition to the stabilization of the ternary complex. The effects of polyamines on MS2 RNA directed reaction resembled those on poly(U) directed polypeptide synthesis, indicating that polyamines are essential in protein biosynthesis directed by natural messengers in vivo. The quaternary amine inhibited the aminoacylation of tRNA(Phe), and the inhibition was canceled by the addition of another polyamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗
PubMed1993

Effects of polyamines on a continuous cell-free protein synthesis system of an extreme thermophile, Thermus thermophilus.

A continuous cell-free protein synthesis system of an extremely thermophilic eubacterium, Thermus thermophilus HB27, was constructed. This system produced MS2 phage RNA translation products at a rate of more than 5 micrograms per hour per 1.9 mg of ribosomes at 65 degrees C and the production continued linearly for at least 340 min. When no polyamine was added, the system did not produce the proteins. The highest activity was recorded when 0.1 mM tetrakis(3-aminopropyl)ammonium and 1.0 mM spermine were added simultaneously.

Bacterial Proteins↗
PubMed1993

Platelet calcium handling in spontaneously hypertensive rats and in three strains of normotensive rats.

OBJECTIVES: Abnormalities in platelet calcium handling have been reported in spontaneously hypertensive rats (SHR) compared with Wistar-Kyoto (WKY) rats. Furthermore, several reports have indicated that WKY rats differ from both SHR and Wistar rats. The objectives of the present study were to investigate platelet calcium handling in three normotensive stains and in SHR, and to confirm the abnormal calcium mobilization in SHR. DESIGN AND METHODS: We compared calcium handling in fura-2-loaded platelets of SHR, Wistar, Sprague-Dawley (SD) and WKY rats. RESULTS: The basal cytosolic free Ca2+ concentration in platelets was significantly higher in SHR and significantly lower in SD rats than in the other strains. The intracellular Ca2+ response to thrombin in the presence of extracellular Ca2+ was greater in SHR than in the three normotensive strains. The thrombin-induced intracellular Ca2+ rise in the absence of extracellular Ca2+ was also greater in SHR and lower in SD rats than in and Wistar rats at higher doses of thrombin. The intracellular ionomycin-released calcium fraction, which may indicate the size of intracellular calcium stores, was similar in SHR, WKY and Wistar rats, and was greater than in SD rats. No difference was detected between WKY and Wistar rats in resting and peak agonist-evoked intracellular Ca2+ concentrations. CONCLUSIONS: These results show that calcium handling in WKY rats is similar to that in Wistar rats with respect to platelet calcium metabolism and confirm the abnormality in SHR. Furthermore, the enhanced intracellular Ca2+ response to thrombin in SHR was not dependent on the size of ionomycin-released Ca2+ stores. In addition, substantial differences in platelet calcium handling may occur even among normotensive strains if the strains are not related.

Animals↗
PubMed1993

Na(+)-Ca2+ exchange modulates Ca2+ handling of human platelets by altering intracellular Ca2+ store size.

OBJECTIVE: In order to elucidate the role of Na(+)-Ca2+ exchange in regulating cytosolic free Ca2+ concentration in human platelets, we investigated the relationship between cytosolic free Na+ and Ca2+ concentrations in human platelets. METHODS: Sodium-binding benzofuran isophthalate and fura-2 were used to monitor cytosolic free Na+ and Ca2+ concentrations, respectively. RESULTS: Ouabain at a concentration of 100 mumol/l induced an increase in cytosolic free Na+ concentration within 5 min, followed by increases in resting cytosolic free Ca2+ concentration and intracellular Ca2+ store. These three parameters were increased in a time-dependent manner significantly above the timed control over a period of 60 min. Pre-incubation of platelets with 100 mumol/l ouabain for 30 min significantly enhanced the cytosolic free Ca2+ response to thrombin and arginine vasopressin in the absence of extracellular Ca2+. The decrease from peak cytosolic free Ca2+ concentration in response to ionomycin in the absence of extracellular Ca2+ was significantly slower in low-Na+ buffer than in standard buffer. In addition, 5 mumol/ionomycin increased the cytosolic free Na+ concentration markedly in the presence of 0.1 mmol/l extracellular Ca2+, but the rise in cytosolic free Na+ concentration was suppressed by 2 mmol/l Ni2+ (NiCl2) or by removal of extracellular Ca2+. CONCLUSIONS: These results suggest that Na(+)-Ca2+ exchange is important in extruding Ca2+ from the cytosol in human platelets, and inhibition of this exchange leads to the accumulation of intracellular Ca2+ store, which may be responsible for the enhanced responsiveness of cytosolic free Ca2+ to agonists.

Blood Platelets↗
PubMed1993

An Alkalophilic Bacillus sp. Produces 2-Phenylethylamine.

A large amount of 2-phenylethylamine was produced in cells of alkalophilic Bacillus sp. strain YN-2000. This amine is secreted in the medium during the cell growth. The amounts of 2-phenylethylamine in both cells and medium change upon changing the pH of the medium.

Journal Article↗
PubMed1993

A physical map of the sulfur-dependent archaebacterium Sulfolobus acidocaldarius 7 chromosome.

A chromosomal map of the sulfur-dependent thermoacidophilic archaebacterium Sulfolobus acidocaldarius 7 was constructed with four restriction enzymes: NotI, BssHII, RsrII, and EagI. The map indicated that the chromosome is a single circular DNA of 2,760 +/- 20 kb (mean +/- standard error of the mean). rRNA genes were also mapped. They were located at one site in the genome.

Blotting, Southern↗
PubMed1993

Primary aldosteronism with ipsilateral adrenal cyst: report of a case.

Adrenal cysts are rare; most lack endocrinologic activity and do not produce clinical symptoms. The present case is the first to be reported with both an adrenal cyst and a functioning adenoma present ipsilaterally. This 39-year-old male with hypertension was diagnosed as having primary aldosteronism as reflected by hypokalemia and an excess plasma aldosterone concentration (PAC). However, examination by computed tomography revealed a grossly enlarged left adrenal gland with a cyst-like lesion. The right adrenal appeared normal. At surgery, an adenoma and a cyst were found to coexist in the left adrenal cortex. The cyst fluid contained three times the amount of aldosterone present in plasma, less than in previous reports, and was considered to lack endocrinologic activity. Following a left adrenectomy, the patient's blood pressure, serum potassium concentration, and PAC all normalized without the need for medical treatment.

Adenoma↗
PubMed1993

Erythrocyte sodium cannot predict hypotensive effects of calcium channel blockers.

Antihypertensive efficacy of the calcium channel blocker, nilvadipine, was investigated in 21 patients with essential hypertension in relation to the intracellular sodium concentration ([Na]i) in erythrocytes and clinical variables, such as age, body weight, pretreatment blood pressure and plasma renin activity. Dihydropyridine nilvadipine reduced mean blood pressure from 120 +/- 6 to 106 +/- 8 mmHg (p < 0.01). The hypotensive effect of nilvadipine was positively correlated with age (r = 0.67, p < 0.01) and inversely correlated with plasma renin activity (r = -0.62, p < 0.01), but was not correlated with erythrocyte [Na]i or any other indices. Erythrocyte [Na]i was decreased with nilvadipine treatment (8.27 +/- 1.69 to 7.97 +/- 1.49 mM, p < 0.01). However, no link was found between the change in [Na]i and the hypotensive effect of the drug. In conclusion, the antihypertensive efficacy of nilvadipine was predictable by age and renin status, but not by erythrocyte [Na]i. A significant role of reduction of [Na]i in the hypotensive effect of the calcium channel blockers was not detected.

Age Factors↗
PubMed1993

[Detection of methicillin-resistant Staphylococcus aureus by in vitro enzymatic amplification of mecA and femA genes].

In the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection, rapid detection of MRSA is extremely important. The mecA gene codes the new drug resistant polypeptides called penicillin-binding protein 2a (PBP2a) or 2'(PBP2'), which mediates the clinically relevant resistance to all beta-lactam antibiotics. This gene could be beneficial in the detection of MRSA using the polymerase chain reaction (PCR). However, the identical mecA gene has been found in both coagulase-positive and coagulase-negative Staphylococcus with the appropriate methicillin-resistant phenotype. The second gene related to the expression of methicillin-resistance has been called femA. In this study, we amplified both mecA and femA genes by PCR in 97 strains and 32 clinical specimens. The mecA gene was positive in all 63(100%) MRSA strains and 2(6%) of the 34 methicillin-sensitive Staphylococcus aureus (MSSA) strains. Two strains with the methicillin-sensitive phenotype and the mecA gene resulted in methicillin-resistance when cultured on an agar plate containing 4.5% NaCl. The mecA gene was also present in all 10(100%) coagulase-negative Staphylococcus strains with the methicillin-resistant phenotype. The femA gene was positive in all 97(100%) MRSA and MSSA strains. On the other hand, the femA gene was absent from coagulase -negative Staphylococcus strains with the methicillin-resistant phenotype. Although the mechanism by which the product of femA gene influences the expression of methicillin-resistance is unknown, the gene appears to be restricted only in coagulase-positive Staphylococcus, regardless of methicillin-resistance. In conclusion, in vitro enzymatic amplification of both mecA and femA genes would lead to rapid and definite diagnosis of the MRSA infection.

Base Sequence↗
PubMed1992

[Hydralazine-induced enhancement of hyperthermia treatment in vivo].

Hydralazine (Hyd) is a vaso-active drug that significantly affects the nature of blood flow in tumors. As a result, Hyd reduces blood flow and oxygen tension in tumors, causing an increase in the toxic effect of hyperthermia treatment. We investigated enhancement of the anti-tumor effect of hyperthermia by Hyd on SCC-VII tumors in C3H mice. Hyd was administered by intraperitoneal injection, and tumors were heated by water bath. We measured the tumor temperature in animals receiving Hyd by thermocouple. We found no significant change in tumor temperature with Hyd treatment. The effect of Hyd (2.5 mg/kg, 5.0 mg/kg, 7.5 mg/kg) on tumors was evaluated in terms of a growth delay value at which tumor volume reached four-fold. The growth delay values obtained were 6.25 +/- 0.82, 7.14 +/- 0.90, 8.50 +/- 0.98, 9.72 +/- 0.92, and 9.84 +/- 1.3 days for: hyperthermia alone, Hyd of 1.0 mg/kg, 2.5 mg/kg, 5.0 mg/kg, respectively. This effect was independent of the time course of administration of Hyd. These results indicate that Hyd can increase the therapeutic efficacy of hyperthermia treatment. Changes in the microenvironment, such as low pH and tumor hypoxia, induced by arterial embolization may have increased the sensitivity of tumors to heat.

Animals↗
PubMed1992

Immunocytochemical localization of 205 kDa microtubule-associated protein (205 kDa MAP) in the guinea pig organ of Corti.

We have studied the immunocytochemical localization of microtubule-associated proteins (MAPs) in the guinea pig organ of Corti. Using immunological methods with antibodies against MAP1A, MAP1B, MAP2, tau and 205 kDa MAP, we have identified 205 kDa MAP as a major MAP of the sensory epithelium in the organ of Corti. Immunoperoxidase microscopic study has shown that both cochlear hair cells and supporting cells reacted with anti-205 kDa MAP antibody. Immunoelectron microscopy revealed that 205 kDa MAP was associated with most microtubules in the sensory epithelial cells. It was also associated with the microtubules of bundle structures within supporting cells, suggesting that this MAP might form a part of cross-bridges between microtubules and between microtubules and actin filaments in the bundle structure. In contrast, MAP1A, MAP1B and tau, which are known to be expressed in neuronal tissue, were localized only in nerve fibers in the organ of Corti, not in the sensory epithelium. MAP2, which is known to be localized in dendrites and soma of nerve cells, was not distributed in nerve fibers in the organ of Corti. These results suggest possible roles of the 205 kDa MAP in the formation and maintenance of the highly polarized morphology of the epithelial cells of the organ of Corti, through stabilization and modulation of microtubule networks of these cells.

Animals↗
PubMed1992

Molecular structure and function of the porcine arachidonate 12-lipoxygenase gene.

The gene encoding arachidonate 12-lipoxygenase was cloned from a porcine EMBL3 genomic library using a cDNA probe of the enzyme, and its nucleotide sequence was determined. The gene consists of 14 exons with 13 introns, and spans approximately 8 kilobases. Analysis of splice junctions indicated that all of the splice donor and acceptor sites conformed to the GT/AG rule. An approximately 1-kilobase region upstream of the coding sequence contains nine GC-boxes for potential Sp1-binding sites at positions -77, -135, -145, -165, -214, -636, -643, -684, and -813. There are two sets of AP-2 binding sequence at positions -234 and -402. Neither typical TATA box nor CCAAT box is found in this region. The transcriptional start site was determined by primer extension analysis, and was tentatively identified as a cytidine residue located 19 bases upstream from initiation codon. Southern blot analysis revealed the presence of one copy of 12-lipoxygenase gene per haploid genome. We found striking similarities in genomic organization as well as the promoter sequences between the porcine 12-lipoxygenase and the rabbit 15-lipoxygenase genes, suggesting that these genes are evolutionarily related.

Amino Acid Sequence↗
PubMed1992

[Evaluation of thermal damage after hyperthermia on murine experimental tumor by 31P-NMR spectroscopy--correlation between ATP and growth curve].

The possibility of using 31P-NMR spectroscopy (31P-MRS) to estimate the effect of hyperthermic treatment on mouse FM3A tumor was investigated. 1 x 10(6) cells, suspended in saline, were subcutaneously inoculated to the right thigh of C3H mice. For hyperthermic treatment, the tumor-bearing leg was heated by immersing it in a water bath at 44 degrees C for 10, 20 or 30 min. The signal intensities of ATP and Pi of the tumor were measured utilizing the 31P-MRS technique to calculate the ATP/Pi ratio. Immediately after heating, the ATP/Pi ratio decreased markedly. Eighteen hours after hyperthermic treatment, the ratio recovered but was still smaller than the control value, then became almost constant by 24 hours after heating. The ATP/Pi ratio at 24 hours after heating decreased with increased length of heating and was inversely related to tumor regrowth after hyperthermic treatment. We concluded that non-invasive monitoring with 31P-MRS might provide a good indication of the effect of hyperthermic treatment.

Adenosine Triphosphate↗