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Biomedical subjects

M Ochiai

Publications and source records attributed to M Ochiai.

At least 163 records · Page 9Linked to original sources
PubMed1989

Radiosensitizing hypoxic cells with new 3-nitro-1,2,4-triazole derivatives in vitro and in vivo.

The new regioisomer derivatives 4a-f and 5a-f of 3-nitro-1,2,4-triazole (3-NTR) were synthesized for the development of new radiosensitizers of hypoxic cancer cells for radiotherapy. N(2)-Substituted 3-NTR derivatives 5a-f were stronger radiosensitizers of hypoxic cells in vitro (Chinese hamster V79 cells) than N(1)-substituted 3-NTR derivatives 4a-f, but in vivo they were weaker (SCCVII carcinoma cells inoculated into C3H/He mouse).

Animals↗
PubMed1989

Inhibition of development of tolerance to nitroglycerin by preventive administration of N-acetylcysteine in rats.

The efficacy of N-acetylcysteine in reversing nitrate tolerance has been controversial. This study examined whether continuous administration of N-acetylcysteine, a sulfhydryl compound, can prevent the development of tolerance to nitroglycerin; its acute effects on developed tolerance were also assessed. Rats were treated with subcutaneous injections of 1) 100 mg/kg nitroglycerin, 2) 100 mg/kg nitroglycerin and 700 mg/kg N-acetylcysteine, 3 times a day for 3 days. The sensitivity to nitroglycerin was studied in aortic preparations. The degree of developed tolerance to nitroglycerin was partially inhibited by simultaneous injection of N-acetylcysteine. Subsequent in vitro preincubation of aortic strips with nitroglycerin (10(-5) M) reduced the subsequent nitroglycerin sensitivity of vessels from rats treated with nitroglycerin and N-acetylcysteine; sensitivity returned to the initial control level after in vitro preincubation with N-acetylcysteine. The nitroglycerin sensitivity of vessels from rats treated only with nitroglycerin, though, was not affected by in vitro preincubation with N-acetylcysteine. In conclusion, N-acetylcysteine is not effective in reversing the high degree of tolerance developed to nitroglycerin. However, continuous administration of N-acetylcysteine is effective in preventing the development of nitroglycerin tolerance.

Acetylcysteine↗
PubMed1989

[The relationship between mitral regurgitation and asynergy of the left ventricle in old myocardial infarction].

To elucidate the mechanism of mitral regurgitation (MR) in patients with old myocardial infarction, two-dimensional (2D) and 2D Doppler echocardiographic examinations were performed in 92 patients. According to the sites of asynergy in the short-axis view of the left ventricle at the papillary muscle level, the patients were classified in three groups; i.e., anteroseptal (AS) group (49 cases), inferoposterior (IP) group (29 cases), and the AS + IP group (14 cases). The existence and severity of MR were evaluated by 2D Doppler echocardiography and the presence of mitral valve prolapse (MPV), by 2D echocardiography. The mitral valve ring diameter was also measured. The incidence of MR was significantly higher in the IP group (41%) and AS + IP group (43%) than in the AS group (20%) (p less than 0.05, respectively). In the IP group, 21 patients had left ventricular asynergy at the base of the posterior papillary muscle; eight did not. In the former 21 patients with asynergy, MR was detected in 12 (57%) and MVP in nine (43%), whereas neither MR nor MVP was detected in the eight patients without asynergy. The grade of MR assessed by 2-D Doppler echocardiography was significantly more severe in patients with MVP than in those without MVP (MR distance: 23 +/- 6 mm with MVP vs 11 +/- 1 mm without MVP; p less than 0.05, MR area; 312 +/- 217 mm2 with MVP vs 64 +/- 29 mm2 without MVP; p less than 0.05). MR appeared at the mitral orifice between its middle portion and the posteromedial commissure, which coincided with the site of MVP in the majority of cases. In the AS and AS + IP groups, however, such close relationships between MR and MVP were absent. In these groups, mitral valve ring diameters were significantly larger in patients with MR than in those without MR (AS group: 32 +/- 3 mm with MR vs 24 +/- 2 mm without MR; p less than 0.01, IP group: 26 +/- 2 mm with MR vs 25 +/- 2 mm without MR; NS, AS + IP group: 30 +/- 3 mm with MR vs 24 +/- 1 mm without MR; p less than 0.05). Mitral valve ring diameters in the IP group with MR (26 +/- 2 mm) were smaller than in those in the AS and AS + IP groups with MR, and did not differ from those in the IP group without MR (25 +/- 2 mm). In conclusion, posterior papillary muscle dysfunction was mainly responsible for MR in the inferoposterior infarction and the dilatation of the mitral valve ring in the infarction involving the anteroseptal wall.

Aged↗
PubMed1989

Activation of the ret-II oncogene without a sequence encoding a transmembrane domain and transforming activity of two ret-II oncogene products differing in carboxy-termini due to alternative splicing.

We previously reported the cloning of a transforming gene, ret-II, which contains the proto-ret kinase domain. In the present study ret-II cDNAs were cloned from a transformant and analyzed. The restriction map and nucleotide sequence indicated that the sequence upstream of the proto-ret kinase domain was replaced by another sequence, which encoded a fusion protein composed of 899 amino acids. This non-proto-ret sequence differed from that of the ret previously reported and had no hydrophobic amino acid stretch for a transmembrane domain. Furthermore, we obtained two kinds of ret-II cDNAs differing in their 3' regions and found that the differences were generated by alternative splicing. From these cDNAs, two types of oncogene products differing in their carboxy-terminal amino acid residues were predicted. The two products exhibited similar transforming activity in NIH3T3 cells. These data indicate that activation of proto-ret can occur as a result of replacement of the extra-cellular and transmembrane domains with the hydrophilic sequence. In addition, differences in the carboxy-terminal amino acid residues in the two types of ret-II oncogene products have no influence on the transforming activity of the ret-II oncogene.

Amino Acid Sequence↗
PubMed1988

Purification of a beta-1,3-glucan recognition protein in the prophenoloxidase activating system from hemolymph of the silkworm, Bombyx mori.

The plasma fraction (referred to as plasma-CPB) of silkworm hemolymph, from which a protein with affinity to beta-1,3-glucan was specifically removed according to Yoshida et al. (Yoshida, H., Ochiai, M., and Ashida, M. (1986), Biochem. Biophys. Res. Commun. 141, 1177-1184), was used to develop a method for quantitating the beta-1,3-glucan recognition protein of the prophenoloxidase activating system. In principle, a sample was judged to contain beta-1,3-glucan recognition protein when that sample could restore the ability of the system in plasma-CPB to be triggered by beta-1,3-glucan. Purification procedures for the recognition protein from silkworm hemolymph consisted of fractionation with ammonium sulfate, chromatography on DEAE-Toyopearl, Affi-Gel-heparin, and Mono Q and Superose 12 on the fast protein liquid chromatography system of Pharmacia LKB Biotechnology Inc. About 2.03 mg of beta-1,3-glucan recognition protein was obtained from 300 ml of hemolymph. The purified beta-1,3-glucan recognition protein was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing-polyacrylamide gel electrophoresis. beta-1,3-Glucan recognition protein had a molecular mass of 62 kDa composed of a single polypeptide and an isoelectric point of pH 4.3. It bound to curdlan beads (composed of beta-1,3-glucan with average particle size of 80 micron) in the absence of divalent cation, whereas its binding to glucans with beta(1----4)- or alpha(1----6)-glycosidic linkages was not detected under the experimental conditions. Elution of the beta-1,3-glucan recognition protein bound to curdlan beads could be achieved under strongly denaturing conditions (after incubation of the beads with sodium dodecyl sulfate and beta-mercaptoethanol in boiling water for 5 min), but elution at room temperature was poor. Since beta-1,3-glucan recognition protein is the only protein in silkworm plasma with strong affinity to beta-1,3-glucan and endows the prophenoloxidase activating system in plasma-CPB with the ability to be triggered by beta-1,3-glucan, it was concluded that binding of the purified beta-1,3-glucan recognition protein with beta-1,3-glucan causes the triggering of the prophenol-oxidase activating system in silkworm plasma. However, the nature of the activity that is generated as the result of binding is not yet known. The purified beta-1,3-glucan recognition protein bound to beta-1,3-glucan did not hydrolyze appreciably any of the 26 commercially available peptidyl-7-amino-4-methylcoumarins, substrates for various proteases.

Animals↗
PubMed1988

Modulation of tyrosine phosphorylation of p36 and other substrates by the S-100 protein.

The inhibitory effects of Ca2+-binding proteins on tyrosine phosphorylation of p36 protein isolated from bovine intestinal epithelium by immunoprecipitated p130fps were investigated. S-100 protein dose dependently inhibited the p36 phosphorylation, and calmodulin weakly depressed the phosphorylation, whereas parvalbumin and troponin C had no significant effects. The S-100 preparation purified from bovine brain did not contain phosphatase activity or ATPase activity. The concentration of ATP did not affect the S-100-mediated inhibition of phosphorylation but the substrate protein, p36, reversed the inhibition. S-100 similarly inhibited the tyrosine phosphorylation of p36 by p60src but did not affect the p36 phosphorylation by protein kinase C. S-100 inhibited the tyrosine kinase activity of p130fps using the other substrates tested as well. These results suggest that S-100 interacts with the substrate binding site of retroviral tyrosine-specific protein kinases and may play a regulatory role in the tyrosine phosphorylation.

Adenosine Triphosphatases↗
PubMed1988

Thyroid hormones inhibit the Ca2+ calmodulin-induced activation of myosin light chain kinase.

L-Thyroxine (T4) and L-triiodothyronine (T3) specifically, inhibited myosin light chain kinase (MLC-kinase) from various tissues whereas inhibitory effects of T4 and T3 on other protein kinases such as protein kinase C, cAMP-dependent protein kinase, casein kinase I, casein kinase II and calmodulin kinase II were much weaker. T4 was a more potent inhibitor of MLC-kinase than T3. Kinetic studies showed that T4 behaved as a competitive inhibitor of MLC-kinase toward calmodulin (CaM) and that Ki value was 2.5 microM. The activity of the catalytic fragment of MLC-kinase, which is active without CaM, was not inhibited by T4. 125I-T4 gel overlay revealed that CaM did not bind T4 but MLC-kinase had 125I-T4 binding activity. These observations suggest that T4 binds at or near CaM binding domain of MLC-kinase and inhibits CaM-induced activation of MLC-kinase.

Animals↗
PubMed1988

Identification of a transforming activity suppressing sequence in the c-raf oncogene.

Our previous study revealed that the rat c-raf was activated by a rearrangement leading to replacement of the amino-terminal half of the product. Therefore, we suggested that some sequences present in the amino-terminal half might prevent c-raf from becoming an active oncogene. To examine this possibility, we constructed a series of deletion mutants of c-raf cDNA by the random linker insertion method. By transfection of NIH3T3 cells with these mutants, a region whose deletion resulted in activation of c-raf was identified. This region is located at amino acid residues 245 to 261, immediate upstream of the kinase domain of the c-raf product and is rich in serine and threonine residues. This region includes a sequence of six amino acids, RSTSTP, which is conserved in the products of normal raf gene families of various species. This sequence is the best candidate for suppressing transforming activity of c-raf.

3T3 Cells↗
PubMed1988

Identification by a random linker insertion method of a region which suppresses the transforming activity of the raf oncogene.

Activation mechanism of raf oncogene was studied by applying in vitro mutagenesis to its cDNA. Previous studies suggested the presence of an activation suppressing sequence in the amino-terminal half of c-raf product. Loss of the sequence by genetic rearrangement was presumed to convert c-raf to possess transforming activity. To identify such sequence, we prepared cDNA mutants by random linker insertion. Synthetic oligonucleotide linker was inserted into the plasmid containing cDNA at a single and random site. Coupling two different mutants, in-frame deletion mutants were constructed systematically. Analysis of these deletion mutants revealed a region, the loss of which made c-raf activated.

Animals↗
PubMed1988

[Transmitral blood flow velocity patterns evaluated by pulsed Doppler echocardiography in diagnosing transient myocardial ischemia].

To evaluate the influences of transient myocardial ischemia on transmitral blood flow velocity patterns, pulsed Doppler echocardiography was performed during coronary artery occlusion in 10 anesthetized open-chest dogs, and also during esophageal pacing or the administration of dipyridamole in 79 patients with coronary artery disease (CAD), and in 19 control subjects. During occlusion of the coronary artery, an abrupt decrease in the peak velocity of the rapid filling wave (R) was noted within one min simultaneously with rapid decrease of % wall thickening in the ischemic regions. The peak velocity of atrial filling was augmented compensatorily. Although the transmitral blood flow velocity pattern did not change in the controls with esophageal pacing, changes similar to those which were obtained during experimental studies were demonstrated in CAD patients. There were no significant differences between transmitral blood flow velocity patterns of patients with multivessel disease and those with single vessel disease. Ischemic changes in transmitral blood flow velocity patterns were not demonstrated in patients with mitral regurgitation. Sublingual nitroglycerin normalized post-pacing abnormal blood flow velocity patterns. In contrast, after the intravenous administration of 0.56 mg/kg of dipyridamole, R and A were increased and the A/R ratio was unchanged both in CAD patients and the control groups. Deceleration time, or the half time, was prolonged during both provocation tests in CAD patients, and these changes were transient and were restored within several min. Furthermore, they were noted more frequently than was the development of ST depression on ECG, or chest pain. These findings indicate that the transmitral blood flow velocity patterns obtained by pulsed Doppler echocardiography are useful for detecting transient myocardial ischemia, though they have limitations in diagnosing the extent of coronary artery disease.

Animals↗
PubMed1988

Molecular cloning and characterization of human ret-II oncogene.

A transformant having ret-II was obtained by transfection of NIH3T3 cells with DNA from a human sigmoid colon cancer. Comparison of the restriction map of ret-II with that of proto-ret revealed that the ret-II has rearrangements both 5' and 3' to the sequence coding for the kinase domain. However, only the upstream rearrangement was consistently observed in all transformants, suggesting that the upstream rearrangement resulted in the activation of proto-ret. The recombination point and replaced sequence of ret-II were different from those previously reported for ret (Takahashi et al., 1985). In addition, ret-II does not retain region coding for transmembrane of proto-ret. This rearrangement, however, was not detected in the original tumor DNA by Southern blot analysis.

Animals↗
PubMed1988

[Tricuspid regurgitation in mitral valve prolapse studied by two-dimensional color flow mapping].

To assess the incidence of tricuspid regurgitation (TR) in mitral valve prolapse (MVP), 96 patients with MVP and 23 normal control subjects were studied. Subjects in the MVP group were further classified as a group with mitral regurgitation (MR(+) group: 61 cases), and MR(-) group (35 cases). The presence of TR in each group was studied by two-dimensional color flow mapping using a Toshiba SSH-65A apparatus. The incidence of TR was 49% in the MR(+) group and 34% in the MR(-) group, and both (35 cases). The presence of TR in each group was studied by two-dimensional color flow mapping using a Toshiba SSH-65A apparatus. The incidence of TR was 49% in the MR(+) group and 34% in the MR(-) group, and both values were statistically greater than 9% in the control group (p less than 0.001 and p less than 0.05, respectively). A female preponderance was observed only in the MR(+) group. Tricuspid valve prolapse was observed in six cases (10%) in the MR(+) group, two cases (6%) in the MR(-) group, and none in the control group. The mean tricuspid ring dimension did not differ significantly among the three groups. The female patients in MR(+) group had statistically greater measurements than the normal female subjects (p less than 0.01). In conclusion, the incidence of TR was statistically greater in female patients in the MR(+) group than in females in the other groups. It is suspected that functional or pathological changes which induce MVP are likely to progress to the tricuspid ring in female patients.

Adolescent↗
PubMed1987

Effect of oridonin, a Rabdosia diterpenoid, on radiosensitization with misonidazole.

The radiosensitization brought about by oridonin, one of the Rabdosia diterpenoids, alone or in combination with misonidazole, was investigated in Chinese hamster V79 cells. The enhancement ratio of 1.92 was obtained when 0.01 mM oridonin and 1 mM misonidazole were administered to hypoxic cells under radiation. The enhancement ratios of oridonin and misonidazole for hypoxic cells were 1.16 and 1.59 respectively. Hence, a supra-additive effect was obtained by the combined treatment with these two drugs. Under aerobic conditions, no effect of 0.01 mM oridonin on the radiosensitization caused by misonidazole was observed.

Animals↗