PubMed Health⌕ Search

Biomedical subjects

T Sakurai

Publications and source records attributed to T Sakurai.

At least 19 recordsLinked to original sources
PubMed1992

[Prospective randomized trials comparing hyperfractionated radiotherapy with conventional radiotherapy in stage III non-small cell lung cancer].

From September 1987 to August 1990, 36 patients with stage III non-small cell lung cancer were randomly assigned to 65 Gy in 26 fractions of 2.5 Gy each (conventional radiotherapy) or 71.5 Gy in 52 fractions of 1.375 Gy given twice a day (hyperfractionated radiotherapy). The overall time for both groups was 6.5 weeks. The groups were similar in terms of age, performance status, previous chemotherapy, stage IIIA and IIIB, and histopathology. The rate of complete response was 44.4% for hyperfractionation, and 16.7% for conventional fractionation. Overall survival rates at 24 months and 36 months were 50.0% and 21.8% for hyperfractionation, and 31.3% and 0% for conventional fractionation. Fever due to radiation pneumonitis occurred in seven of 18 patients with hyperfractionation (38.9%) and four patients with conventional fractionation (22.2%). No severe late toxicity has been observed in either group. We conclude that hyperfractionated radiotherapy in non-small cell lung cancer may improve survival without increasing severe toxicity.

Adult↗
PubMed1992

Kinetics of electron transfer between cytochrome c and laccase.

Rate constants have been determined for the electron-transfer reactions between reduced horse heart cytochrome c and resting Rhus vernicifera laccase as a function of pH, ionic strength, and temperature. The second-order rate constant for the oxidation of reduced cytochrome c was determined to be k = 125 M-1 s-1 at 25 degrees C in 0.2 M phosphate buffer at pH 6.0 with the activation parameters delta H++ = 16.2 kJ mol-1 and delta S++ = 28.9 J mol-1 K-1. The rate constants increased with decreasing buffer concentration, indicating that electron transfer from cytochrome c to laccase is favored by the local electrostatic interaction (ZAZB = -0.9 at pH 6 and -1.3 at pH 4.8) between the basic proteins with positive net charges. From the increase of the rate of electron transfer with decreasing pH, one of the driving forces of the reaction was suggested to be the difference in the redox potentials between the type 1 copper in laccase and the central iron in cytochrome c. Further, on addition of one hexametaphosphate anion per cytochrome c molecule, the rate of the electron transfer was increased, probably because the association of both proteins became more favorable.

Animals↗
PubMed1992

Complete primary structure and tissue expression of chicken pectoralis M-protein.

M-Protein (165 kDa) is a structural constituent of myofibrillar M-band in striated muscle. We generated a monoclonal antibody which recognized a 165-kDa protein from chicken pectoralis muscle in immunoblot analysis and stained the M-band under immunofluorescence microscopy. By screening a lambda gt11 cDNA library from chicken embryonic pectoralis muscle with this antibody, we isolated a cDNA clone encoding the M-protein. Northern blot analysis showed that M-protein mRNA is expressed in pectoralis and cardiac muscle but not in gizzard smooth muscle or non-muscle tissues. Moreover, the anterior latissimus dorsi muscle, which consists almost exclusively of slow fiber types, contains no detectable levels of the mRNA. The full-length cDNA sequence predicted a 1,450-amino acid polypeptide with a calculated molecular weight of 163 x 10(3). The encoded protein contains several copies of two different repetitive motifs: five copies of fibronectin type III repeats are in the middle part of the predicted molecule, and two and four copies of the immunoglobulin C2-type repeats are located toward the NH2-terminal and COOH-terminal regions, respectively. This indicates that M-protein, along with other thick filament-associated proteins such as C-protein, twichin, and titin, belongs to the superfamily of cytoskeletal proteins with immunoglobulin/fibronectin repeats.

Amino Acid Sequence↗
PubMed1992

Efficient purification of a full length and biochemically active p110Rb, the retinoblastoma gene product.

Rb protein was purified from recombinant baculovirus-infected Sf9 cells to apparent homogeneity by a simple solubilization and by immunoaffinity column chromatography. It was mainly obtained as p110Rb, the underphosphorylated form of the Rb protein family. This p110Rb was shown to form a specific complex in vitro with SV40 Tag and to bind to double or single stranded DNA. It could also affect Tag helicase activity in a biphasic-dose dependent manner, due to these two biochemical functions. This purification procedure provides sufficient amounts of native Rb protein to further elucidate its role as an anti-oncogene protein and a negative regulator of the cell cycle.

Animals↗
PubMed1992

Excitatory effect of adenosine on neurotransmission is due to increase of transmitter release in the hippocampal slices.

Adenosine has dose-dependent biphasic excitatory and inhibitory effects on neurotransmission in the hippocampus. The mechanism of the excitatory action is not known although that of the inhibitory action has been well analyzed. Here we report on the mechanism of excitatory action of adenosine, using hippocampal slices. Studies of intracellular recordings of CA3 pyramidal neurons showed that the amplitude of EPSP was dramatically enhanced by application of adenosine at low concentration (0.1 microM) without changing resting membrane potentials, membrane conductance or the threshold for spike generation by injecting current pulses. On the other hand, the presence of adenosine at a concentration of 0.1 microM during electrical stimulation to the slices increased 1.7 times the release of glutamate, an excitatory neurotransmitter in the hippocampus. These results indicate that the excitatory action of adenosine at low doses is due to the increase of transmitter release.

Adenosine↗
PubMed1992

Level of ETB receptor mRNA is down-regulated by endothelins through decreasing the intracellular stability of mRNA molecules.

Using ROS17/2 rat osteosarcoma cells as a model system, we examined the possibility that endothelin (ET)-induced down-regulation of ETB receptor was accompanied by a decrease in levels of ETB receptor mRNA. Northern blot analysis showed that low doses of ET-1 and ET-3 caused a transient decrease in ETB receptor mRNA in the cells. The maximum decrease in the levels of ETB receptor mRNA (80%) occurred after 2-4 h of exposure of the cells to ETs and was followed by a gradual recovery to control levels by 24 h. The effects were dose-dependent (EC50-1 nM), and ET-1 and ET-3 were almost equipotent in eliciting the response. The addition of either ionomycin, a Ca2+ ionophore, or phorbol dibutyrate, a protein kinase C activator, mimicked the effect of ETs. These results suggested that ETs-induced down-regulation of ETB receptor mRNA was mediated by the activation of ETB receptor and that it may have involved ETB receptor coupled second messenger pathways. We also showed that ETB receptor mRNA had a long intracellular life span which suggested that ETs-induced down-regulation of ETB receptor mRNA may have been due to a decrease in the stability of mRNA, rather than inactivation of the transcription of mRNA.

Animals↗
PubMed1992

Action of endothelin-1 on rat astrocytes through the ETB receptor.

We investigated the effect of ET-1 on the state of rat cerebral astrocytes (AC) differentiation. AC ceased to proliferate and changed into its differentiated state by treatment with dibutyryl cyclic AMP (DBcAMP). The cell growth activity in DBcAMP-treated AC was stimulated by ET-1 in a dose-dependent manner. Over similar dose ranges, ET-1 suppressed the glutamine synthetase activity in DBcAMP-treated AC. The molar potency of ET-1 in this action was at least 3 orders of magnitude higher than that in mitogenic action in AC under the proliferative state previously reported. Northern blot analysis revealed that ETB receptor mRNA level in DBcAMP-treated AC was markedly higher than that in AC untreated with DBcAMP. Consistently, binding studies showed that the Bmax value for [125I]ET-1 in DBcAMP-treated AC was 16 times higher than that in AC untreated with DBcAMP. These results suggest that ET-1 potently induced a retraction of the differentiation state of AC from fully the specialized state and that the high responsiveness of differentiated AC to ET-1 was partly attributed to the high level expression of the ETB receptor.

Animals↗
PubMed1992

Cloning and expression of rat preproendothelin-3 cDNA.

We report here the cloning and expression of a rat full-length cDNA encoding preproendothelin-3 (preproET-3). The predicted rat preproET-3 consisted of 167 amino acid residues. As in other ET-family peptides, the mature rat ET-3 was predicted to be produced through unusual processing from a 41-residue intermediate, the big ET-3 in rat. Transient transfection of COS-7 cells with the cloned preproET-3 cDNA resulted in the production of mature ET-3 and this production was inhibited by phosphoramidon, a metaloprotease inhibitor. This suggested that a phosphoramidon sensitive mechanism was involved in the production of ET-3 in the transfected COS-7 cells. Northern blot analysis showed that an approximately 3.0-kb rat preproET-3 mRNA was expressed in rat tissues, including the eye ball, submandibular gland, brain, kidney, jejunum, stomach and spleen. A 2.0-kb and a 3.3-kb mRNA were also detected in the eye ball and small intestine, respectively. The distinct distribution of rat preproET-3 mRNA from that of preproET-1 mRNA suggested that ET-1 and ET-3 played different roles.

Amino Acid Sequence↗
PubMed1992

Inhibition of Ca(2+)-dependent catecholamine release by myosin light chain kinase inhibitor, wortmannin, in adrenal chromaffin cells.

To elucidate the possible involvement of myosin light chain kinase (MLCK) in the mechanism of exocytosis, we studied effects of MLCK inhibitor, wortmannin, on the secretory function of bovine adrenal chromaffin cells. Preincubation of chromaffin cells with wortmannin inhibited both acetylcholine- and high K(+)-evoked catecholamine (CA) release. The IC50 for high K(+)-evoked CA release was 1 microM. When the cells were permeabilized with digitonin after wortmannin preincubation, Ca(2+)-dependent exocytosis was inhibited in a dose-dependent manner (IC50, 1 microM). These findings suggest the implication of MLCK in the Ca(2+)-triggered process in the machinery of exocytosis.

Acetylcholine↗
PubMed1992

Anaerobic reactions of Rhus vernicifera laccase and its type-2 copper-depleted derivatives with hexacyanoferrate(II).

Anaerobic reactions of Rhus vernicifera laccase and its type-2 copper-depleted derivatives with hexacyanoferrate(II) were investigated by absorption and e.s.r. spectroscopy. When native laccase was treated with excess hexacyanoferrate(II), the type-1 and type-2 coppers were immediately reduced and the e.s.r. signal due to type-3 copper was transiently observed. After incubation, a novel e.s.r. signal (g parallel = 2.31, g perpendicular = 2.08) developed together with the type-1 copper signal. Only the novel e.s.r. signal was left after the sample had been treated with ascorbate. In the corresponding absorption spectrum, a new band was observed at around 490 nm. A similar new e.s.r. signal did not appear for the type-2-copper-depleted (T2D) laccase, in which the type-3 copper had been reduced during the procedure to deplete the type-2 copper. On the other hand, the novel e.s.r. signal emerged when the type-3 copper in T2D laccase had been previously reoxidized with H2O2. The novel e.s.r. signal was not significantly saturated even by 200 mV microwave power at 4 K. Quantitative estimations and a small molecule study for CuII-FeII(CN)6 and CuII-FeIII(CN)6 systems suggested that the novel e.s.r. signal corresponds to some sort of adduct involving the type-3 copper and hexacyanoferrate(II).

Anaerobiosis↗
PubMed1992

Functional regulation of osteoblastic cells by the interaction of activin-A with follistatin.

A high number of 125I-activin-A binding sites (an apparent Kd of 260 pM and 5,600 sites/cell) were observed on MC3T3-E1 cells, a well characterized osteoblastic cell line. Activin-A has a mitogenic effect on these cells, with the greatest influence being observed on cells in an undifferentiated state, as well as a suppressive effect on the alkaline phosphatase activity. Northern and ligand blotting analyses revealed that these osteoblastic cells produce follistatin, which was down-regulated by retinoic acid treatment. Because follistatin is an activin-A-binding protein, we suggest that activin-A modulates the function of osteoblastic cells by being regulated by follistatin during differentiation.

Activins↗
PubMed1992

Reversible effect of calcium-binding protein regucalcin on the Ca(2+)-induced inhibition of deoxyuridine 5'-triphosphatase activity in rat liver cytosol.

The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on deoxyuridine 5'-triphosphatase (dUTPase) in the cytosol of rat liver was investigated. Addition of Ca2+ up to 5.0 microM to the enzyme reaction mixture caused a significant decrease of dUTPase activity, while Zn2+, Cd2+, Co2+, Al3+, Mn2+ and Ni2+ (10 microM) did not have an appreciable effect. The Ca(2+)-induced decrease of dUTPase activity was reversed by the presence of regucalcin; the effect was complete at 1.0 microM of the protein. Regucalcin had no effect on the basal activity of the enzyme. Meanwhile, the reversible effect of regucalcin on the Ca2+ (10 microM)-induced decrease of dUTPase activity was not altered by the coexistence of Cd2+ or Zn2+ (10 microM). The present data suggest that liver cytosolic dUTPase is uniquely regulated by Ca2+ of various metals, and that the Ca2+ effect is reversed by regucalcin.

Animals↗
PubMed1992

Selective reduction of glutamate in the rat superior colliculus and dorsal lateral geniculate nucleus after contralateral enucleation.

The effects of afferent lesions on the levels of glutamate, aspartate and gamma-aminobutyric acid (GABA) in the laminae of the superior colliculus (SC) and dorsal lateral geniculate nucleus (dLGN) of the rat were studied, using microassay methods for these amino acids. The analysis was performed 12-14 days after left eye enucleation, or ablation of right visual cortical area, or both left eye enucleation and ablation of right visual cortex. Superficial gray layer (SGL) and deep layers in the SC were dissected out from the thin-sectioned, freeze-dried sample. In the dLGN, the outer and inner laminae were separately dissected. The glutamate contents in the upper half of SGL and outer lamina of dLGN contralateral to eye enucleation decreased significantly (15%). Combination of eye enucleation and visual cortical ablation further decreased the glutamate content in the upper half of the right SGL (29.3%). On the other hand, aspartate and GABA concentrations in the SC and dLGN exhibited no significant reduction after deafferentations. These results indicate that the retino-tectal and retino-geniculate pathway of the rat may be glutamatergic in nature.

Animals↗
PubMed1992

Spin-echo M-mode NMR imaging.

A nuclear magnetic resonance (NMR) imaging and display method for the observation of the continuous motion of objects is presented. By modifying a line scan technique, the spin-density distribution along a line is displayed in succession. Although spatial information is limited to only one dimension, the motion of the object is recorded at intervals of 55 ms by using a commercially available NMR imaging system. In a phantom study, this method yielded accurate velocity measurements along a single axis. When the method was applied to the human chest, an image analogous to that of M-mode echocardiography was obtained. This method, which can be called spin-echo M-mode NMR imaging, approaches the functional analysis of cardiac wall motion in regions where echocardiography is not possible. The effects of respiratory motion on the left ventricular wall were recorded in addition to its intrinsic contractile motion in an image obtained along a line parallel to the cranio-caudal axis of the body. The advantages of this method to assess cardiac wall motion in a patient with an arrhythmia were also demonstrated.

Atrial Fibrillation↗
PubMed1992

Electrospray ionization mass spectra of hemoglobin and transferrin by a magnetic sector mass spectrometer. Comparison with theoretical isotopic distributions.

Electrospray ionization mass spectra of human hemoglobin chains and of transferrin were acquired on a magnetic sector mass spectrometer. The observed molecular ion for each hemoglobin chain was in good agreement with the theoretical isotopic distribution at a reasonable resolution of 2000. The clear separation of a variant beta-chain in admixture with the normal counterpart at mass 15,867 that differed from it by 14 Da (0.09%) ensured that a smaller mass difference could be detected. The molecular ions for human transferrin were too broad compared with the theoretical shape to determine the molecular mass accurately, probably due to the heterogeneity of the carbohydrate moiety. A decrease in mass by neuraminidase digestion, however, determined the average number of sialic acids in the molecule.

Hemoglobins↗
PubMed1992

A comparative study of once-a-day morning and once-a-day bedtime administration of 40 mg famotidine in treating duodenal ulcers.

A randomized controlled study comparing once-a-day morning and once-a-day bedtime administration of 40 mg famotidine in treating duodenal ulcers was carried out in 99 Japanese patients. Endoscopic examinations were performed at the baseline and repeated at 3-week intervals until healing was confirmed. Eighty-two patients fulfilled the evaluation criteria (38 in the morning group and 44 in the bedtime group). In 13 of these patients the antisecretory effects of these regimens were also assessed by 24 h intragastric pH monitoring. The healing rates were 66% after 3 weeks and 95% after 6 weeks in the morning group, and 57% after 3 weeks and 80% after 6 weeks in the bedtime group. The differences were insignificant between the two groups, but there was a higher healing rate tendency after 6 weeks in the morning group (0.05 less than P less than 0.10). Regarding pain subsidence, there were no significant differences between the two groups. Both treatments were significantly superior to the control group in increasing 24 h intragastric pH. The morning regimen was significantly superior to the bedtime regimen in suppression of daytime acidity. On the contrary, the bedtime regimen was significantly superior to the morning regimen in suppression of nocturnal acidity. These findings suggest that suppression of nocturnal acidity is important but not essential to promote duodenal ulcer healing and suppression of daytime acidity is equally important. Thus, once-a-day morning administration of 40 mg famotidine seems to be at least as effective as once-a-day bedtime administration of 40 mg famotidine in treating duodenal ulcers.

Adult↗
PubMed1992

Molecular characterization of endothelin receptors.

Following the first report on the identification of endothelin (ET), an increasing body of work has accumulated on this endothelium-derived 21-amino acid vasoconstrictor peptide. Subsequently, the existence of three distinct isoforms of ET, designated ET-1, ET-2 and ET-3, was predicted from the finding of three separate genes. The differential potencies of the three isoforms of the ET family have opened up the possibility of the existence of multiple ET receptor subtypes. Recently, molecular biological techniques provided direct evidence of at least two distinct subtypes of ET receptor. This article discusses the functions of the ETs, focusing especially on the molecular characteristics of their receptors.

Amino Acid Sequence↗