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Biomedical subjects

M Tsuboi

Publications and source records attributed to M Tsuboi.

At least 199 records · Page 11Linked to original sources
PubMed1984

A possible correlation between DNA conformation and the mode of action of restriction enzymes.

The cutting modes of restriction endonucleases which recognize tetradeoxyribonucleotide sequences are classified into two groups. d(GGCC) and d(CGCG), for example, are cut to produce blunt ends, while d(CCGG) and d(GCGC) are cut to produce two-base-long cohesive ends. A conformational analysis by the Calladine-Dickerson method indicates that d(GGCC) and d(CGCG) should have a roll angle of successive base-pairs open towards the major groove at the central (second) base-pair step. On the other hand, d(CCGG) and d(GCGC) have such open roll angles at the first and third base-pair steps. It is suggested that, in general, the cutting mode of a tetramer-specific enzyme depends primarily upon the substrate conformation, rather than upon the enzyme. Similar correlations between the mode of action and substrate conformation are also suggested for hexamer-specific enzymes.

Base Sequence↗
PubMed1984

Sex difference in the inhibitory effect of aspirin on prostacyclin production of rat aortae.

The effect of aspirin on the prostacyclin (PGI2) production of rat aorta was investigated, and the influence of sex hormones on the effect of aspirin was studied by the treatments of hormone administration, ovariectomy and castration. There was no significant sex difference in the arterial production of PGI2 between male and female rats. However, the PGI2 production was decreased with aspirin treatment, and the effect of aspirin was more efficient in male rats. The inhibitory effect of aspirin was reduced in the rats treated with estradiol and the castrated male rats, but it was potentiated in the rats treated with testosterone and the ovariectomized female rats. These results suggest that sex hormones may regulate the effect of aspirin on the PGI2 production in the aorta.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Effects of Ca2+ and calmodulin antagonists on the oxygen uptake induced by acetylcholine or substance P in rat submandibular gland slices.

Effects of Ca2+ and calmodulin antagonists on the oxygen uptake induced by acetylcholine (ACh) or substance P (SP) were investigated in rat submandibular gland slices. The oxygen uptake induced by ACh or SP was significantly inhibited by removing Ca2+ from the medium and the slices. The oxygen uptake by ACh in the Ca2+-deficient slices was almost completely recovered by the addition of 3.0 and 5.0 mM Ca2+, whereas that by SP was not recovered by the addition of 3.0 mM Ca2+, but recovered by 5.0 mM Ca2+. Ca2+ antagonists, diltiazem, verapamil and La3+, significantly inhibited the ACh-induced oxygen uptake. On the other hand, the SP-induced oxygen uptake was inhibited by diltiazem and La3+, but not by verapamil. Calmodulin antagonists, trifluoperazine, chlorpromazine and W-7, had no inhibitory effects on the ACh-induced oxygen uptake. The SP-induced oxygen uptake was not affected by trifluoperazine, chlorpromazine and low concentrations of W-7, but was inhibited by high concentrations of W-7. These results suggest that the ACh- or SP-induced oxygen uptake is dependent on the presence and permeability of Ca2+ with a subtle difference between the ACh and the SP mechanisms and that the oxygen uptake is independent of calmodulin.

Acetylcholine↗
PubMed1984

Sequence-dependant polymorphism of DNA duplex in solutions.

Raman spectra of six synthetic polydeoxyribonucleotide duplexes with different base sequences have been examined in aqueous solutions with different salt or nucleotide concentrations. Detailed conformational differences have been indicated between B and Z forms of poly[d(G-C)] X poly[d(G-C)], between B forms of poly[d(G-C)] X poly[d(G-C)] and poly[d(G-m5C)] X poly[d(G-m5C)], between A and B forms of poly(dG) X poly(dC), between B and "CsF" forms of poly[d(A-T)] X poly[d(A-T)], between B forms of poly[d(A-U)] X poly[d(A-U)] and poly[d(A-T)] X poly[d(A-T)], and between low- and high-salt (CsF) forms of poly(dA) X poly(dT). The Raman spectrum of calf-thymus DNA in aqueous solution was also observed and was compared with the Raman spectra of its fibers in A, B, and C forms.

Animals↗
PubMed1983

Internal motion of deoxyribonucleic acid in chromatin. Nanosecond fluorescence studies of intercalated ethidium.

We have investigated the internal motions of DNA in a nucleosome core particle and chromatin by measuring the nanosecond fluorescence depolarization of intercalated ethidium. Assuming that the observed anisotrophy decay originates from the torsional motion of DNA, we have analyzed the dynamics of DNA in a nucleosome core particle and in chromatin in detail. The results suggest that DNA in a nucleosome core particle has a torsional rigidity similar to that of DNA in solution and that even at the point of the ionic bonds between DNA and a histone octamer the torsional motion of DNA is not completely inhibited. On the other hand, the dynamics of linker DNA in chromatin were found to reflect the overall structural state of the chromatin: the motion of linker DNA was suppressed as the structure of chromatin turned from an extended state to a condensed one. This indicates that, in solenoidal chromatin, nucleosome movements in chromatin are largely suppressed. Furthermore, the result may suggest that the torsional rigidity of linker DNA is increased as it is forced to bend in solenoidal chromatin.

Animals↗
PubMed1983

Hydrogen-deuterium exchange studies on guanidinated pig heart lactate dehydrogenase.

Pig heart lactate dehydrogenase becomes more thermostable on increasing the degree of guanidination (conversion of lysine to homoarginine) (Minotani, N., Sekiguchi, T., Bautista, J.G. and Nosoh, Y. (1979) Biochim. Biophys. Acta 581, 334-341). The conformational change of the protein on guanidination was then examined by hydrogen-deuterium (H-2H) exchange reactions. It ws found that (i) the fluctuation degrees of peptides and tyrosine and tryptophan residues in the protein decrease in that order, (ii) two H-2H exchangeable tryptophan residues per subunit are freely accessible to solvent and the fluctuation degrees of the residues does not change on guanidination, (iii) the H-2H exchange detectable tyrosine residues are not freely accessible to solvent and become less fluctuating when 15 lysine residues per subunit are guanidinated, and (iv) the peptides become much less fluctuating on increasing the degree of guanidination. The specific activity of the enzyme decreased on guanidination. The increased thermostability of the protein on guanidination may be related to the decrease in flexibility of the molecular structure by sacrificing the enzyme activity.

Animals↗
PubMed1983

Raman diagnosis of nucleic acid structure: sugar-puckering and glycosidic conformation in the guanosine moiety.

Observations of Raman spectra of various nucleic acids indicate that the guanine ring breathing frequency is sensitive to the internal rotation angle around the glycosidic bond and to the conformation of the five-membered ring of the ribose residue that is directly connected with the guanine residue in question. It is found that 682 cm-1 for C2'-endo-anti, at 665 cm-1 for C3'-endo-anti, and at 625 cm-1 for C3'-endo-syn. A DNA octamer d(GpGpApApTpTpCpC) shows, in its aqueous solution, a broad Raman band at 680 cm-1 with a tail at 670 cm-1. This fact suggests that the guanosine residues in this oligomer take primarily C2'-endo-anti conformation but an appreciable amount of fluctuation of the ribose ring structure towards C3'-endo is involved.

Base Sequence↗
PubMed1983

The isolation and genetic analysis of sporulation-deficient mutants in Saccharomyces cerevisiae.

Sporulation-deficient mutants were isolated from a homothallic strain of Saccharomyces cerevisiae. Sporulation was induced in these mutants by procedures to sporulate the products of protoplast fusion between mutants and wild-type strains. Spores formed in this way were crossed to wild-type strains in order to analyze them genetically. Twenty-three genes essential to sporulation were identified by tetrad analysis and complementation tests. Gene symbols spoT1 to spoT23 were tentatively assigned to them. These mutants fell into four classes by examination of premeiotic DNA synthesis and meiotic nuclear division: (i) Premeiotic DNA synthesis did not occur (spoT1 - spoT11); (ii) premeiotic DNA synthesis occurred but meiosis I did not occur (spoT12 - spoT15); (iii) meiosis II did not occur (spoT16 - spoT18); (iv) meiosis II occurred but mature spores were not formed (spoT19 - spoT23). Genes spoT4, spoT8, spoT20, and spoT23 were mapped on chromosomes IV, II, XVI and XI, respectively. SpoT18-1 was a UAG nonsense mutation.

Crosses, Genetic↗
PubMed1983

Dynamics of DNA in chromatin and DNA binding mode to core protein.

We have studied the dynamics of DNA in nucleosome core particles and in the linker region of chromatin using nanosecond fluorescence anisotropy decay measurements of intercalated ethidium. DNA in the core undergoes torsional motions to the same extent as the linker DNA in extended chromatin. We therefore concluded that the binding of DNA to the histone octamer is relatively weak or limited to a few points; stretches of at least several tens of base pairs exist which can move as freely as DNA in solution.

Animals↗
PubMed1983

Immunocytochemical localization of T antigen in cells of BK virus-induced hamster brain tumor.

The localization of both the large T and small t tumor (T) antigens in cultured cells (Vn 12 cells) of hamster brain tumors induced with BK virus (BKV), a new human papovavirus, was studied by an enzyme labelled antibody method at both the light and electron microscopic levels. Under the light microscope, BKV T antigen was observed in the nucleus, except for the nucleoli, of cells in interphase, and under the electron microscope it was observed in the nucleus except for the nucleoli and nuclear membrane. BKV T antigen appears to be closely associated with nuclear chromatin as previously reported for simian virus 40 tumor antigen (SV40 T antigen). The intracellular localization of BKV T antigen was the same as that of SV40 T antigen. In metaphase, BKV T antigen seems to be distributed diffusely throughout the cytoplasm except for the chromosomes. In telophase, BKV T antigen transfers from the cytoplasm to the nucleus. The migration of BKV T antigen during the cell cycle is thought to be related to the function of T antigen.

Animals↗
PubMed1983

Stimulation of amylase and sialic acid releases from dog submandibular gland slices by pilocarpine or high K+ medium: a possible role of calmodulin for their releases.

The mechanism of amylase and sialic acid releases stimulated by pilocarpine or high K+ medium was investigated in the slices of dog submandibular glands. The release of both amylase and sialic acid was dose-dependently increased by pilocarpine and a considerable release was observed at pilocarpine concentrations of more than 1 microM. Similar effects were observed when K+ concentration in the medium was increased and the maximal response was observed at 75 mM K+. The release of amylase and sialic acid by pilocarpine or K+ considerably decreased by removing Ca2+ from the medium and the slices. The release of amylase in the Ca2+-deficient slices was nearly recovered by the addition of 2.5 and 5.0 mM Ca2+, whereas that of sialic acid was recovered by only 60-75%. Ca2+ inhibitors, La3+ and verapamil, and calmodulin inhibitors, trifluoperazine, prenylamine, and W-7, significantly inhibited the release of amylase and sialic acid induced by the stimulants. These results suggest that the release of amylase and sialic acid stimulated by pilocarpine or K+ is dependent on the presence of Ca2+, and that the activation of calmodulin is involved in the process of the release.

Amylases↗
PubMed1983

Studies on peptide antibiotics, leucinostatins. I. Separation, physico-chemical properties and biological activities of leucinostatins A and B.

Leucinostatin, a peptide antibiotic, was separated by silica gel and alumina column chromatography into two related components designated as leucinostatin A hydrochloride (C61H111-N11O13.HCl) and leucinostatin B hydrochloride (C61H109N11O13.HCl). Physico-chemical as well as biological properties of the two separated components were analyzed. These properties pointed to closely resembling chemical structures.

Animals↗
PubMed1983

Studies on peptide antibiotics, leucinostatins. II. The structures of leucinostatins A and B.

Structures I and II have been assigned to leucinostatins A and B based on fast atom bombardment, secondary ion, field desorption and chemical ionization mass spectrometry, NMR studies and chemical degradation methods of the intact antibiotics and their acid hydrolysis products. The essential difference between leucinostatins A and B is concluded to be the replacement of (2S)-N1,N1-dimethylpropane-1,2-diamine in leucinostatin A by (2S)-N1-methylpropane-1,2-diamine in leucinostatin B. This was further confirmed from the evidence that methylation with methyl iodide led each antibiotic to the identical compound which was named leucinostatin A-M (III).

Anti-Bacterial Agents↗
PubMed1983

[Effects of Ca2+ and calmodulin inhibitors on lipolysis induced by epinephrine, norepinephrine, caffeine and ACTH in rat epididymal adipose tissue].

The effects of Ca2+ and calmodulin inhibitors on lipolysis induced by epinephrine, norepinephrine, caffeine and ACTH in rat epididymal adipose tissue were investigated. 1. Omission of Ca2+ from the incubation medium slightly depressed lipolysis induced by epinephrine, norepinephrine and ACTH. Lipolysis induced by caffeine was significantly depressed. 2. Lipolysis induced by epinephrine, norepinephrine, caffeine and ACTH was strongly depressed when Ca2+-deficient tissue was incubated in Ca2+-free Ringer solution. 3. In Ca2+-deficient tissue, the addition of 0.75mM Ca2+ apparently restored lipolysis induced by epinephrine, norepinephrine and ACTH, whereas that by caffeine was restored to only approximately 89%. 4. The addition of La3+ markedly inhibited lipolysis induced by each agonist. 5. The Ca2+ antagonists such as verapamil and diltiazem dose-dependently inhibited lipolysis induced by each agonist. 6. The specific calmodulin inhibitors such as chlorpromazine, trifluoperazine and W-7 markedly inhibited lipolysis induced by each agonist. These results strongly support the possible key role that the redistribution and influx of Ca2+ may play in lipolysis induced by epinephrine, norepinephrine, caffeine and ACTH, and further suggest that calmodulin may affect lipolysis.

Adipose Tissue↗