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Biomedical subjects

J Takahashi

Publications and source records attributed to J Takahashi.

At least 19 recordsLinked to original sources
PubMed1992

Decrease in plasma GLP-1 immunoreactivity in starved rats.

To determine whether starvation affects the metabolism of glucagon-like peptide-1 (GLP-1), we measured the plasma levels of proglucagon-derived peptides and the biosynthesis and posttranslational processing of proglucagon in groups of six rats starved for 1, 3 and 5 days. The plasma levels of GLP-1 immunoreactivity (GLP-1 IR) and glucagon-like immunoreactivity (GLI) decreased during starvation reaching 79 and 56% of the respective control values by day 5 (P less than 0.05 and less than 0.01 vs control). The same is true of the plasma IRI level. The ileal contents of GLP-1 IR and GLI were 50.8 +/- 3.8 pmol/g wet weight and 161.8 +/- 13.2 pmol/g wet weight, respectively, on day 5 of starvation, which were significantly lower (P less than 0.01) than the respective values of 94.8 +/- 16.6 pmol/g wet weight and 262.7 +/- 28.1 pmol/g wet weight in control rats. However, the pancreatic contents of proglucagon-derived peptides tended to increase during starvation, although their increases were not statistically significant. No significant change in the posttranslational processing of proglucagon was detected during starvation. The decrease in the ileal proglucagon-derived peptides content was not associated with a decrease in intestinal proglucagon mRNA transcripts. These results suggested that decreased synthesis of proglucagon-derived peptides by the intestine was largely responsible for the reductions in their circulating levels in starved rats.

Analysis of Variance↗
PubMed1992

Cell kinetic study of murine jejunal crypts during multiple doses per day.

We studied cell kinetics of mouse jejunal crypts during multiple fractionation using double labeling methods. Mice were irradiated to the total body once a day or twice a day. Fraction size was 2 Gy. Overall time was 1, 3 and 5 days. Labeling index (LI), duration of S phase (Ts) and potential doubling time (Tpot) were assessed next morning following the irradiation schedule. Mice were administered both bromo-deoxyuridine (BrdUrd) and 3H-Thymidine ([3H]dT) with a constant interval. Removed jejunum were stained with immuno-histochemistry and, then, processed for autoradiography. BrdUrd and [3H]dT LIs were the same and were increased up to 5 days despite the fractionation schedule. After 1 day following 2 fx/day, both Ts and Tpot decreased significantly. For 1 fx/day treatment, neither Tpot nor Ts changed. After 5 day following 1 and 2 fx/day, both Ts and Tpots were the same and Tpots were significantly shorter than that obtained from control. It seems that proliferative responses between 1 and 2 fx/day were different.

Animals↗
PubMed1992

N-(F-18)-fluoroacetyl-D-glucosamine: a new positron labeled pharmaceutical for cancer study.

In order to evaluate the role of hexosamine metabolism in tumor tissue, we studied the biodistribution of N-(F-18)-fluoroacetyl-D-glucosamine (FAGlu) in male Donryu rats bearing poorly differentiated hepatomas (AH109A and AH272). Compare with the former result of the high tumor uptake of FAGlu in C3H/He mice bearing well differentiated spontaneous hepatoma, the tumor uptakes of FAGlu in these tumors showed the lower values. This suggested that spontaneous hepatoma maintained a high activity of glucosamine metabolism, while poorly differentiated hepatoma had little activity. Metabolism of glucosamine in tumor tissue may be another marker for characterizing tumors. We also discuss the tissue distribution of new F-18 labeled hexosamines, N-(F-18)-fluoroacetyl-D-mannosamine and N-(F-18)-fluoroacetyl-D-galactosamine in tumor bearing rats.

Acetylgalactosamine↗
PubMed1990

Effects of nutritional conditions on plasmid stability and production of tryptophan synthase by a recombinant Escherichia coli.

Effects of nutritional conditions and insertion direction of the tryptophan synthase (TSase) gene into a plasmid vector on the plasmid stability and the production of TSase in high cell concentration cultures were examined using recombinant Escherichia coli (E. coli K12 IFO 3301) harboring pBR322trpAB(1) (the TSase gene was inserted at the EcoRI site of pBR322 in the clockwise direction) and pBR322trpAB(2) (counterclockwise direction). As to the effects of the insertion direction, the cells harboring pBR322trpAB(2) were slightly lower in the growth rate and the plasmid stability than those harboring pBR322trpAB(1). However, the former was higher in the productivity of TSase and the final cell concentration attained than the latter. On the other hand, the addition of organic nutrients, especially yeast extract, to TK-25 medium was very effective to improve the plasmid stability. Among the components of yeast extract, L-glutamic acid was found to be effective to improve both the plasmid stability and the production of TSase. When 1 g/l of L-glutamic acid was added to TK-25 medium, a mineral synthetic medium developed for a high concentration culture, 115g (dry basis)/l of recombinant cells were obtained in 14 hr and the expression of TSase was maintained at 240-300 U/mg-protein during the cultivation.

Amino Acids↗
PubMed1979

Analysis of paramagnetic centers in X-ray-irradiated enamel, bone, and carbonate-containing hydroxyapatite by electron spin resonance spectroscopy.

Carbonate-containing hydroxyapatite, enamel, and bone were irradiated by an X-ray and investigated between 77 degrees and 350 degrees K by means of electron spin resonance (ESR) spectroscopy. The ESR spectrum of enamel irradiated at 77 degrees K in vacuum and observed at the same temperature was almost the same as that of the carbonate-containing hydroxyapatite. The temperature dependence of signal intensities confirms a spin-energy exchange between the mineral and organic constituents in bone, but in enamel no or very little spin-energy exchange between the mineral and organic constituents. Considerable similarity among the ESR spectra of enamel, bone, and carbonate-containing apatite was obtained after X-ray irradiation in air at 300 degrees K with both an X-band and a Q-band ESR spectrometer. The Q-band spectrum can be interpreted in terms of two paramagnetic species. One is identified as a CO3(3-) anion radical which has an axial symmetry with g factors of 2.0029 and 1.9972. The other species is found to be centered at g = 2.0019.

Animals↗
PubMed1979

[Oxygen contents and casting porosities in Ag alloys (author's transl)].

Although pure Ag has a large casting porosity near the sprue attachment, Ag-Zn and Ag-Cu alloys have small or no porosities. The casting porosities of Ag-Au alloys are similar to that of pure Ag. These experimental results were discussed using the calculated oxygen contents in molten state and the measured oxygen contents of castings, and related to the capacity for deoxidization of additive elements. In the present study the casting porosities in pure Ag and Ag-Au alloys are considered to be not shrinkage porosities, but porosities due to discharged oxygen gas. In spite of high oxygen contents of molten state and castings, the casting porosity was not observed in pure Cu. This may be due to the fact that the occluded oxygen atoms exist as copper oxide (Cu2O) in solid Cu.

Dental Alloys↗