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Biomedical subjects

T Ishida

Publications and source records attributed to T Ishida.

At least 1,207 records · Page 67Linked to original sources
PubMed1980

X-ray structural and conformational studies of [5'-(tryptaminocarbonyl)-2'-deoxyribofuranosyl]thymine, a model compound for the study of the interaction between indole and thymine rings.

The crystal structure of [5'-(tryptaminocarbonyl)-2'-deoxyribofuranosyl]-thymine was determined by an X-ray method in order to elucidate a fundamental feature of interaction between indole and thymine rings. Refinement resulted in a conventional R value of 0.043. The bond lengths and angles are in good agreement with those of the related compounds. The deoxyribose unit has a C2'-endo envelope conformation, and orientation of the thymine base with respect to the sugar is anti. In the crystal, the double layers of the thymidine moieties are formed by the hydrogen bonds around a two-fold screw axis and a single layer of the indole moieties is held together by van der Waals contact, and they are alternately packed parallel to the bc-plane. The conformation of the molecule is an extended form, and the intra- and intermolecular interactions between the indole and thymine rings are not observed in the crystal because the dihedral angle of both rings is approximately a right angle (95.8 degrees), and there is no hydrogen bond or short contact between these rings. It was, however, suggested from the ultraviolet spectroscopic study in dilute solution and from the conformational analysis by energy calculation that the most stable conformation is a folded form with the intramolecular stacking interaction between indole and thymine rings. Therefore, the extended form observed in the crystal might be caused by the packing interaction between the neighboring molecules.

Chemical Phenomena↗
PubMed1980

Immunoreactive dog C-peptide level in the pancreatic vein.

C-peptide immunoreactivity (CPR) levels were measured in dog superior pancreaticoduodenal vein using synthetic dog C-peptide and its antiserum. The basal CPR level was approximately twice as high as the basal immunoreactive insulin (IRI) level on a molar basis. Glucose (10 mg/kg/min) or arginine (250 mg/kg/min) infusion for 5 min into the superior pancreaticoduodenal artery caused a prompt, parallel increase in IRI and CPR. IRI and CPR were closely equimolar at peak secretions. One bolus administration of synthetic neurotensin (10 microgram/kg) into the same artery produced a mild hyperglycemic response and biphasic IRI and CPR responses at 30 min in the vein. The IRI and CPR increases were closely equimolar during the first phase of secretion, but during the second peak a larger increase was found in CPR than IRI. Upon infusion of synthetic substance P (50 ng/kg/min) for 30 min, IRI and CPR concentrations showed a parallel and closely equimolar fall. These results indicate that insulin and C-peptide were released from beta cells in equimolar concentrations.

Animals↗
PubMed1980

The effect of somatostatin on the hepatic extraction of insulin and glucagon in the anesthetized dog.

Effects of somatostatin (250 ng/kg . min) or saline infusion on hepatic extraction of endogenous and exogenous insulin and glucagon were investigated in anesthetized dogs. After a 20-min control period, somatostatin or saline was infused into the superior mesenteric vein for 100 min. During the final 50 min of the somatostatin or saline infusion, insulin (1.7 mU/kg . min) and glucagon (20 ng/kg . min) were also infused. These infusions were then replaced with a saline infusion for an additional 30 min. Somatostatin rapidly and significantly decreased portal vein insulin and glucagon concentrations. Hepatic extraction of endogenous insulin decreased from the control value of 61 +/- 5% to 29 +/- 10% during the final 20 min of somatostatin infusion before exogenous insulin and glucagon were added to the infusion. The decrease in hepatic extraction of endogenous insulin is based on the mean of the individual values of the eight dogs in the group and may be spurious because of the very low concentrations of insulin which were being measured and the fact that at such low concentrations, some dogs appeared to have negative hepatic extraction of inulin. Glucagon extraction was unchanged (9 +/- 6% compared to 7 +/- 12%) during the first 50 min of infusion of somatostatin. Column chromatography demonstrated that the 3500 mol wt fraction of glucagon comprised 75 +/- 4% of the total glucagon immunoreactivity in the portal vein during the control period and 67 +/- 13% during the infusion of somatostatin. During the final 20 min of somatostatin infusion before the addition of insulin and glucagon, the blood glucose significantly decreased and hepatic glucose output fell from 2.4 +/- 0.4 to 1.4 +/- 0.3 mg/kg . min. However, the insulin to glucagon (3500 mol wt fraction) molar ratio did not change significantly (4.2 +/- 1.1 to 2.6 +/- 0.5). During the final 20 min of the combined infusion of somatostatin, insulin, and glucagon, hepatic extraction of insulin returned to control values and glucagon extraction rose from 7 +/- 12% to 35 +/- 11%. Hepatic glucose output increased without any significant change in the portal vein insulin to glucagon molar ratio. After the termination of the combined infusion, hepatic extraction of insulin was unchanged, but glucagon removal returned to control values. At this time, the portal vein insulin to glucagon ratio rose, and hepatic production of glucose fell below control values. These results demonstrate that somatostatin may influence peripheral insulin and glucagon values by modifying their hepatic extraction and inhibiting their pancreatic secretion. Hepatic glucose output did not always reflect the portal vein insulin to glucagon molar ratio.

Anesthesia↗
PubMed1980

5-Di-(2'-tetrahydropyranyl)secalonic acid D as a new antibiotic derivative with anticancer activity.

A pyranyl derivative was chemically synthesized from secalonic acid D, an antibiotic obtained from culture filtrates of Penicillium oxalium, and its anticancer activity towards a highly antigenic rat bladder cancer, BC-47, implanted into inbred ACI/N rat was studied. The anticancer effect of the drug was similar to that of adriamycin. Delayed initiation of treatment, starting 5 days after the cancer implantation, was more effective than treatment starting from day 1. In addition, it was less effective in an immunodeficient host subsequently implanted with BC-47. This compound is thought to retard the cancer cell growth until the appearance of tumor immunity in the host.

Animals↗