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Biomedical subjects

S Tamura

Publications and source records attributed to S Tamura.

At least 613 records · Page 34Linked to original sources
PubMed1987

Molecular cloning and nucleotide sequence of cDNA specific for rat ribosomal protein L5.

cDNA clones specific for rat ribosomal protein L5, which is the protein moiety of 5S RNA protein particles, were isolated by using a mixture of tetradecamer deoxyribonucleotide probes reflecting the amino acid sequence of the N-terminal portion of L5. A cDNA clone (pRL5-1) lacking the 3'-terminal region of L5 was isolated by hybrid-selected translation and shown to be L5-specific by the identity of the deduced amino acid sequence and that of the N-terminus of protein L5. pRL5-1 was then used to select another clone (pRL5-2) by colony hybridization which contained the entire coding region, 3'-non-coding region and poly(A) addition signal. The nucleotide sequence of L5-specific cDNA was determined by using these two clones. It contained a total of 1069 base pairs: 123 base pairs in the 5'-non-coding region, 894 base pairs in the coding region and 52 base pairs in the 3'-non-coding region. The poly(A) addition signal appeared at the 33rd nucleotide after the termination codon. The amino acid sequence deduced from this nucleotide sequence consists of 296 amino acids. The homology of amino acid sequence between L5 and other 5S RNA-binding proteins is discussed.

Amino Acid Sequence↗
PubMed1987

ATP-Mn2+ stimulates the generation of a putative mediator of insulin action.

Substantial evidence suggests that insulin receptor-associated protein kinase may play a pivotal role in the expression of the intracellular effects of insulin. This study was undertaken to determine whether insulin receptor kinase contributes to the generation of putative insulin mediators. The effect of ATP and divalent cation addition on the production of insulin mediators from liver plasma membranes was investigated. ATP (1 mM) added to liver plasma membranes in the absence of divalent cations enhanced insulin-stimulated release/generation of mediator slightly (approximately 3-fold). ATP in the presence of Mn2+ further increased release/generation of mediator markedly (approximately 100-fold). In contrast, ATP in the presence of Mg2+ had no stimulatory effect. Mn2+ and Mg2+ alone were ineffective. Addition of EDTA completely diminished the stimulatory effects of insulin, ATP, and Mn2+. The stimulation was ATP-specific since other nucleotides and nonhydrolyzable analogues of ATP had no or very weak activity. ATP-Mn2+ stimulated insulin-dependent mediator release/generation in a dose-dependent manner. These results suggest that insulin mediator release/generation is markedly stimulated by an ATP-Mn2+-dependent phosphorylation reaction, similar to insulin-stimulated receptor tyrosine kinase phosphorylation.

Adenosine Triphosphate↗
PubMed1987

Computed tomography and angiography in MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes); report of 3 cases.

Among mitochondrial encephalomyopathies, MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes, Pavlakis et al. 1983) is recognized as a distinct syndrome characterized by generalized convulsions and recurrent stroke-like episodes. The neuroradiological findings of three patients with MELAS are reported here. Retrospective review shows that MELAS should be included in the differential diagnosis of infarct-like lesions of the cerebrum.

Acidosis, Lactic↗
PubMed1987

Isolated unilateral absence of left pulmonary artery with peribronchial arteriovenous malformation showing recurrent hemoptysis.

Unilateral absence of a pulmonary artery is an uncommon condition and usually complicated by a cardiac anomaly. Our case is a rare one who showed the absence of the left pulmonary artery with left aortic arch and without cardiac anomaly. He suffered from recurrent hemoptysis and pneumonia since he was 9 months old. Angiography revealed peribronchial arteriovenous malformation of the affected lung which was supplied from subclavicular arteries and bronchial arteries. Although he was treated by operative ligation and angiographic embolotherapy of the supplying systemic arteries, the repeated the attacks of massive hemoptysis and necessiated left pneumonectomy at 10 years of age.

Arteriovenous Malformations↗
PubMed1987

Hepatic conversion of 1-(tetrahydro-2-furanyl)-5-fluorouracil into 5-fluorouracil in patients with hepatocellular carcinoma.

The pharmacokinetics of 1-(tetrahydro-2-furanyl)-5-fluorouracil (FT) and its conversion into 5-fluorouracil (FUra) in liver tissue were studied in ten patients with hepatocellular carcinoma (HCC). The plasma concentration of FT after its intravenous injection (dosage: 800 mg) was computerfitted to a bi-exponential function (C = Ae-alpha t + Be-beta t), indicating a two-compartment disposition. The pharmacokinetic parameters did not significantly differ between the five patients with, and the five without cirrhosis of the liver. The plasma concentrations of FUra likewise showed no significant difference between the two groups. The rates of FT degradation in the liver tissue homogenate were similar for four of the patients with cirrhosis (0.10 +/- 0.05 mumol/g liver protein/30 min) and four of those without it (0.13 +/- 0.05). The rates of cytochrome P-450-dependent FUra formation in the microsomal fraction of liver tissue from two patients (1.1 and 1.3 nmol/mg microsomal protein/30 min) were dramatically reduced to less than half of those of two control subjects (2.4 and 2.7). The estimated rates of FUra formation in the soluble fraction (105,000 X g supernatant fraction) from the two patients (0.1 and 0.13 nmol/mg protein/30 min) were almost identical to those from the controls (0.12 and 0.14), suggesting that the rate in the soluble fraction from HCC patients may not be as strongly affected as the rate in the microsomal fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Studies on primed precursors of effector T cells involved in delayed-type hypersensitivity to sheep red blood cells in mice.

The nature of primed precursor T cells (primed pre-TD), capable of differentiating into effector T cells (TD) that mediate delayed-type hypersensitivity (DTH), was investigated in B10 mice which were primed by intravenous (iv) injection of various doses of sheep red blood cells (SRBC). The presence of primed pre-TD was detected by the ability of T cells in the spleens from primed mice, which were treated in vitro with pertussis toxin and then transferred into naive recipient mice, to generate DTH in the recipient mice 14 days after transfer. The primed pre-TD were induced antigen specifically 1 day after mice were primed by iv injection of a suboptimal (10(3)), an optimal (10(5)), or supraoptimal (10(9)) dose of SRBC. They were replaced by TD 4 days after priming in optimally sensitized mice, while they were maintained without generating TD for at least 5 weeks after priming in mice primed with either a suboptimal or a supraoptimal dose of SRBC. They were L3T4-positive and dense cells, fractionated in the high-density layers on a discontinuous Percoll density gradient, and capable of transforming into less dense TD, fractionated in the low-density layers. These results indicate that primed pre-TD, which are induced by an antigen signal and then can be activated by a nonspecific stimulus, are present not only in responsive mice but also in unresponsive mice, suggesting that either the generation of TD from primed pre-TD or primed pre-TD alone is the decisive factor for either responsiveness or unresponsiveness.

Animals↗
PubMed1987

Selective reduction of hepatic cytochrome P450 content in patients with intrahepatic cholestasis. A mechanism for impairment of microsomal drug oxidation.

Alteration of the components of the mixed-function oxidase system, including cytochrome P450, cytochrome b5, cytochrome P450 reductase, and cytochrome b5 reductase, was examined in liver microsomes prepared from needle biopsy samples of 12 patients with intrahepatic cholestasis. The rate of p-nitroanisole O-demethylation in the microsomes was also measured as the activity of cytochrome P450-dependent drug oxidation. The cytochrome P450 content (0.29 +/- 0.05 nmol/mg microsomal protein) in the patients was significantly lower than that in the 11 control subjects (0.41 +/- 0.09). The rate of p-nitroanisole O-demethylation was also significantly lower in the patients. However, the cytochrome b5 content and the activities of the reduced forms of nicotinamide adenine dinucleotide phosphate- and nicotinamide adenine dinucleotide-cytochrome c reductases did not differ between the two groups. Thus, selective reduction of cytochrome P450 seems to play a major role in the impairment of microsomal drug oxidation during intrahepatic cholestasis. Moreover, the reduction of cytochrome P450 was correlated with the serum concentrations of total bilirubin and bile acid but not with the serum glutamic oxaloacetic transaminase value. These observations suggest that the reduction of cytochrome P450 might be related to the severity of cholestasis.

Adult↗
PubMed1987

Oligodendrogliomas of the lateral ventricle: computed tomography and angiography.

Computed tomographic (CT) and angiographic findings in four cases of oligodendroglioma of the lateral ventricle are reported. CT showed a midline nodular intraventricular mass containing punctate calcifications and cysts. The tumors were slightly to markedly enhanced after the infusion of contrast media. Angiography showed slightly increased vascularity in the mass, and displacement of subependymal veins near the tumor. Oligodendrogliomas of the lateral ventricle are rare but should be included in the differential diagnosis of intraventricular tumors near the foramen of Monro.

Adult↗
PubMed1987

A monoclonal antibody against a synthetic fragment of bombyxin (4K-prothoracicotropic hormone) from the silkmoth, Bombyx mori: characterization and immunohistochemistry.

Monoclonal antibodies were produced by immunizing mice with a synthetic decapeptide corresponding to the N-terminal portion of the A-chain of bombyxin, a peptide from Bombyx mori which activates the prothoracic glands of the saturniid moth, Samia cynthia ricini, and was previously called 4K-PTTH. We obtained a hybridoma clone secreting an antibody that recognized specifically bombyxin after treatments for disulfide-bond reduction but did not when untreated. Immunoblotting studies demonstrated the presence of highly heterogeneous immunoreactive components in Bombyx brain homogenates. Immunohistochemistry using this antibody indicated that bombyxin was produced by four pairs of mid-dorsal neurosecretory cells of the brain and transferred to and released from the corpora allata of Bombyx.

Animals↗
PubMed1987

Activation of rat liver and rabbit skeletal muscle glycogen synthases by rat liver cytosolic protein phosphatases.

To gain more insight into the nature of the substrate specificity of protein phosphatases, four forms of glycogen synthase D were used as substrates for previously characterized protein phosphatases, IA, IB, and II, from rat liver cytosol. The phosphatase activity was measured as the conversion of glycogen synthase D to synthase I. While glycogen synthase isolated from rat liver as the D-form was activated mainly by phosphatase IA, rabbit skeletal muscle glycogen synthase previously phosphorylated in vitro by cyclic AMP-dependent protein kinase or phosphorylase kinase was activated efficiently by phosphatases IA, IB, and II. Glycogen synthase isolated from rabbit skeletal muscle as the D-form, however, was a poor substrate for all three phosphatases. These results suggest that the phosphorylation state as well as the primary structure of synthase D markedly affects the rate of its activation by individual protein phosphatases. A protein phosphatase released from rat liver particulate glycogen, on the other hand, activated all forms of synthase D used here readily and at about the same rate.

Animals↗
PubMed1987

Indication of aorto-coronary bypass graft surgery for infarction area of myocardium considered from exercise thallium-201 myocardial imagings.

To assess accurately the indication and effects of aorto-coronary bypass graft surgery (ACBG) to the myocardium infarction area, 35 patients with myocardial infarction were analyzed by using exercise thallium-201 myocardial imagings. The patients were classified into group I (18 cases) and group II (17 cases) before ACBG. Group I consisted of patients with regional hypoperfusion in the initial image who showed redistribution in the delayed image to the infarction area of myocardium. Group II consisted of those with regional hypoperfusion in the initial image without redistribution in the delayed image. Group I showed a significant improvement in myocardial perfusion (p less than 0.01), pressure rate product (p less than 0.01), global left ventricular ejection fraction (p less than 0.01), segmental wall motion abnormality (p less than 0.01), and exercise tolerance when compared with those of group II before and after ACBG. The above study showed that the pre- operative redistribution of the infarction area in the delayed image suggests myocardial viability and ACBG will be effective.

Coronary Angiography↗
PubMed1987

Immunohistochemical and affinity electrophoretic studies of alpha-fetoprotein of a patient with hepatocellular carcinoma in the intrathoracic space.

Immunohistochemical and affinity electrophoretic studies were carried out on alpha-fetoprotein components produced by a tumor of hepatocellular origin located on the chest wall and originating from the intrathoracic and extrapleural space tissue. The major components of alpha-fetoprotein were consistent with those produced by the hepatocellular carcinoma. Accordingly, this seems to be the first reported case of hepatocellular carcinoma that may have developed from accessory liver tissue seemingly isolated from the liver and located in the intrathoracic space.

Angiography↗