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Biomedical subjects

T Sekiguchi

Publications and source records attributed to T Sekiguchi.

At least 235 records · Page 13Linked to original sources
PubMed1979

Basis of thermostability in pig heart lactate dehydrogenase treated with O-methylisourea.

Acetamidination of pig heart lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) with ethyl acetimidate resulted in an increase of thermostability, and covalent bridge formation between pairs of lysine residues is observed. Guanidination with O-methylisourea of the enzyme also increases the thermostability, but such a bridge seems not to be formed. Increased thermostability of guanidinated enzyme is considered to be due to the shift of the pK values of the lysine residues from 10.5 to 12.5 after guanidination. Modification experiments with carbodiimide reveals that the enzyme contains 4.6 pairs of neighboring lysine and carboxyl residues per subunit, and amide bonding between 3.2 pairs results in an increase of thermostability. Guanidination of 4.6 Lys/subunit of the enzyme yields an enzyme derivative with considerably increased thermostability. Salt bridge formation between the 4.6 pairs of neighboring carboxyl and guanidinated lysine residues per subunit might make a major contribution to the increased thermostability of the guanidinated enzyme.

Animals↗
PubMed1979

Chemical modification of epsilon-amino groups in glutamine synthetase from Bacillus stearothermophilus with ethyl acetimidate.

The activity of glutamine synthetase [EC 6.3.2.1] from Bacillus stearothermophilus decreased slightly on modification with ethyl acetimidate. Acetamidination of 25--26 of the 2 epsilon-amino groups/subunit of the enzyme affected the maximum velocity, but not the Michaelis constant. The thermostability of the enzyme was considerably increased on acetamidination. Acetamidination of the enzyme did not affect the circular dichroism, the tryptophan fluorescence or the quenching effects of KI and acrylamide on the tryptophan emission. The fluorescence spectrum of p-toluidinylnaphthalene sulfonate bound to the enzyme changed on acetamidination.

Geobacillus stearothermophilus↗
PubMed1979

Cross-linking with diimidates of glutamine synthetase from Bacillus stearothermophilus.

Glutamine synthetase [EC 6.3.2.1] from Bacillus stearothermophilus was modified with diethyl malonimidate (DEM), dimethyl adipimidate (DMA), and dimethyl suberimidate (DMS). DMA modified most epsilon-amino groups. On modification with DMA, formation of 3 to 4 cross-links/subunit resulted in a large increase in thermostability. The activity, allosteric properties and fluorescence spectrum of the enzyme were not changed on cross-linking. The SDS-polyacrylamide gel electrophoretic profiles of DEM-, DMA-, and DMS-modified enzymes suggested that the interaction berween six subunits in each of the two hexagonal rings of the protein are heterologous and are different from those between the piled subunits on different rings.

Allosteric Regulation↗
PubMed1979

A case of multiple extra-adrenal pheochromocytomas.

A 22 year old man with two extra-adrenal pheochromocytomas located in the mediastinum and in the pelvis is presented. We believe this is the first report in Japan of extra-adrenal multiple pheochromocytomas in adult located in the two distant places.

Adult↗
PubMed1979

Assessment of fracture healing by vibration.

The wave signal from percussion of a bone (i.e. percussion-note) has been used to evaluate the extent of bony consolidation after fracture. Forty-one cases with a fresh tibial fracture and eight cases of delayed union of the tibia were investigated. The medial malleolus of the tibia was struck with a tapper and the vibration signal was picked up at the medial region of the tibial tuberosity. The changes in the signal waveform of the percussion-note with time were investigated. As healing proceeds, the signal waveform of the fractured bone approaches that of intact bone. In cases of delayed union, the character of the wave does not improve sufficiently with time. The authors are convinced that this is a promising new method for the early diagnosis of delayed union.

Adolescent↗
PubMed1978

A mammalian cell mutant with temperature-sensitive thymidine kinase.

We have isolated a mutant clone from mouse FM3A cells with temperature-sensitive defects both in cytokinesis and in thymidine kinase enzyme activity. The clone, designated tsCl.B59, was isolated after mutagenesis at 33 degrees C followed by exposure to cytosine arabinoside at 39 degrees C. It was derived from a thymidine kinase deficient, 5-bromodeoxyuridine-resistant clone (S-BUCl.42) which was originally derived from wild-type clone H-5 of FM3A cells. The temperature-sensitive mutant clone grows normally at 33 degrees C, but not at 39 degrees C, where it exhibits an increased frequency of multinucleate cells due to defective cytokinesis. Unlike the parental S-BUCl.42 cells, which have negligible thymidine kinase activity and are unable to incorporate 3H-thymidine, the mutant in corporates substantial amounts of 3H-thymidine at 33 degrees C, although its thymidine kinase activity remains lower than that of wild-type H-5 cells. When cultures of tsCl.B59 cells are transferred to 39 degrees C, incorporation of 3H-thymidine decreases markedly. The decrease has been shown to be due to thermolability of the thymidine kinase in tsCl.B59 cells.

Adenocarcinoma↗
PubMed1978

DNA content of microcells prepared from rat kangaroo and mouse cells.

Enucleation of animal cells in which nuclear fragmentation (micronucleation) has been induced by treatment with mitotic inhibitors results in the formation of subdiploid microcells consisting of one or several micronuclei, some cytoplasm and surrounded by a plasma membrane. Microcells were prepared from rat kangaroo cells (12 chromosomes) and a polyoma virus transformed mouse cell line (61 chromosomes) and analysed for DNA content. Microspectrophotometric DNA measurements and the appearance of micronuclei at mitosis show that small micronuclei contain genetic information equivalent to single chromosomes. A large proportion of the micronuclei and the microcells, however, contains DNA corresponding to several chromosomes. Heterogeneous mixtures of microcells can be fractionated by a unit gravity sedimentation procedure so as to isolate the small microcells. These can afterwards be fused with intact normal or mutant cells.

Animals↗
PubMed1977

Acidostability of speroplasts prepared from Thiobacillus thiooxidans.

Thiobacillus thiooxidans was acidostable even in the absence of its respiratory substrate, elementary sulfur. This suggests that the acidostability of the bacterium was enery-independent. The organism was subjected to osmotic shock with 0.75 M sucrose at 0 degrees C and then treated with snail intestinal juice in the presence of 0.3 M sucrose. The decrease in the optical density of the sample thus prepared on dilution with deionized water and electron microscopic observation of the sample showed that spheroplasts were formed from the bacterium by this procedure. Spheroplasts were able to respire sulfur and their respiratory activity was acidostable. Spheroplasts, when treated with Nagase, proteolytic enzyme, lost their acidostability, and some protein components disappeared from the membrane fraction. This suggests that the acidostability of the bacterium may be related to protein conponents of the membrane.

Acidithiobacillus thiooxidans↗
PubMed1977

ATP and acetylene-reducing activity of a sulfate-reducing bacterium.

A sulfate-reducing bacterium, a strain of Desulfovibrio vulgaris, when lactate or pyruvate was supplied as an electron and energy source, reduced acetylene only in the presence of sulfate. Acetylene reduction started after a lag of 1 h. H2 which acts as an electron and energy source for sulfate reduction was unable to reduce acetylene even in the presence of sulfate. It was suggested, from the measurements of the amounts of adenine nucleotides of the bacterium incubated under various conditions, that the bacterium is able to reduce acetylene at a high ATP level or a high ATP/ADP ratio.

Acetylene↗
PubMed1976

Effect of temperature on the viability of Bacillus stearothermophilus.

One of the obligate thermophilic bacteria, Bacillus stearothermophilus, was unable to grow at temperatures below 35 degrees C. About 80% of the population in the bacterial culture died at the temperatures, and the same extent of loss in either of the activities of oxygen consumption or synthesis of protein or nucleic acid of the organisms was observed. With the progress of death of the organisms, reduced nicotinamide-adenine dinucleotide came to be oxidized by the organisms, enzymes such as fructose-1,6-diphosphate aldolase, when the organisms were washed with phosphate buffer, were leaked out of the organisms, and an increasing amount of ribonucleoprotein was released into the culture medium. The change of the membrane state was then suggested to be one of the possible causes for the death of the organisms at the temperatures.

Bacterial Proteins↗