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Biomedical subjects

K Kojima

Publications and source records attributed to K Kojima.

At least 811 records · Page 45Linked to original sources
PubMed1978

Resolutions in imaging with Fresnel zone plate.

A coarse Fresnel zone plate (FZP) may be used as a large-area coded aperture for imaging incoherent sources. The longitudinal and lateral spatial resolutions are discussed on the basis of experiment using an FZP having 18 or 19 zones as an aperture. In this paper, it is then shown that the lateral spatial resolution is about 5 mm and the longitudinal is about 1 cm, respectively and it is appropriate to use the longitudinal resolution factor 3.7 as a guide to know the tomographic effect. These results may be extended for imaging incoherent gamma-ray sources. According to our experiments, radioactivity of several tens of a millicurie is necessary for imaging with 99mTc, when using X-ray film as a detector. Therefore, it is important to improve the detector in order to apply to the human organ imaging generally.

Holography↗
PubMed1978

[Whole-body retention studies of 167Tm-citrate.--Estimation of radiation dose to human from 167Tm-citrate--(author's transl)].

For the purpose of calculating absorbed dose to humans from 167Tm-citrate, the whole-body retention studies using 5 rats were carried out. Up to 40 days following intravenous injection of 167Tm-citrate, the whole-body counts were monitored with a animal counter. The whole-body retention curve was obtained with three exponentaial components. Namely, the 26% of the injected 167 Tm-citrate had a biological half-time of 3.4 hours, 12.5% had a biological half-time of 99 hours and 61.5% had a biological half-time of 106 days. These results indicate, that three components consist of the rapid clearance from the kidneys, the retention in the liver and other soft tissues with relatively long half-time and the retention in the bones with long half-time. Based on these biological data and the MIRD Committee method, the average dose estimates to the bone and whole-body from intravenous administration of 1 mCi 167Tm-citrate were 7.08 rads and 1.28 rads, respectively.

Animals↗
PubMed1978

Rat gastric secretion studies with synthetic gastrin-like tetrapeptide.

Gastric acid and pepsin secretions were measured in the perfusing rat stomach preparation with sodium-citrate-phosphate buffer, pH 6.6. In anesthetized rat stomach preparation, acid output in both basal and stimulated conditions seemed to be small, but pepsin output was observed even in a short period. In the rats which were fed freely just before use, basal pepsin output was significantly lower than that of fasted rats, although in the basal acid output and in the acid and pepsin output during stimulation in both groups, there was no difference statistically. Intravenous infusion of tetragastrin (1, 2, 4, 8, 16 and 32 microgram/kg/hr) produced a dose dependent acid and pepsin secretions. Tetragastrin, at the dose of 8 microgram/kg/hr, stimulated acid and pepsin output. Acid output was kept constant for three hours, but pepsin output was made to peak within an hour and formed a plateau after 1.5 hours at a level of 30% of peak pepsin output.

Animals↗
PubMed1978

Organotropic effect of N-bis (2-hydroxypropyl)nitrosamine: production of lung and liver tumors by its oral administration in mice.

The organotropic effect of N-bis(2-hydroxypropyl)nitrosamine (DHPN) orally administered to mice was studied. The main targets for the carcinogenic effect of DHPN were the lung and liver, with tumors induced by doses greater than 100 ppm DHPN for 16 weeks. The highest incidence was seen in liver vascular tumors including hemangioma, hemangioendothelioma, and hemangioendothelial sarcoma in mice treated with 1,000 ppm DHPN. Lung tumors were alveolar adenoma and adenocarcinoma. No pancreatic tumors were found. The present results suggest that the carcinogenic response in mice to DHPN was similar to that in rats and guinea pigs but different from that in hamsters.

Administration, Oral↗
PubMed1978

Excretion of X-prolyl dipeptidyl-aminopeptidase in human urine as determined with a new fluorogenic substrate.

X-Prolyl dipeptidyl-aminopeptidase activity was found in human urine by a sensitive fluorescence assay in which a new fluorogenic substrate, 7-glycylproline-4-methylcoumarinamide, is used. The Km value was 2.9 X 10(-4) mol/liter, and the optimum pH was 8.7 in glycine-NaOH buffer. The enzyme activity was stable at 4 degrees C for at least five days. On Sephadex G-200 column chromatography, normal human urine showed a main peak with an approximate relative molecular mass of 400 000. The procedure is simple, rapid, and accurate. The enzyme activity in urine of normal adults was: 4.30 +/- 0.13 (SE) (range, approximately 1.84-8.96) micronmol/min per gram of creatinine, and 2.16 +/- 0.09 (SE) (range, approximately 0.38-6.98) micronmol/min per liter of urine.

Adolescent↗
PubMed1977

Translocation of hyaluronic acid in cell surface of cultured mammalian cells after x-irradiation and its recovery by added adenosine triphosphate.

To investigate the mechanism of radiation-induced decrease in cell electrophoretic mobility and its recovery by added adenosine triphosphate, specific enzymes and buffer solutions of different ionic strength were utilized. Decrease in the mobility of irradiated cells was detected only with the buffer solution of ionic strengths higher than 0.100. In this range of ionic strengths, removal of hyaluronic acid from cell surface by hyaluronidase had no effect on the electrophoretic mobility of irradiated cells, while the enzyme treatment resulted in 27% mobility reduction in non-irradiated cells. The removal of sialic acid and chondroitin sulfate by their specific enzymes resulted in the similar decrease in mobility either in irradiated and non-irradiated cells. These results suggest that the X-ray induced translocation of hyaluronic acid from the peripheral zone of O--7.5 A into the deeper zone of about 10--17 A, if we use the Debye-Hückel's thickness of ion atmosphere for an approximate estimate of effective depth of electrokinetic plane of shear. Hyaluronic acid reappeared to the peripheral zone by the subsequent incubation after small dose irradiation, or by the addition of 1 mM adenosine triphosphate with Ca2+.

Adenosine Triphosphate↗
PubMed1977

Decrease and recovery in cell surface charge induced by anesthetics.

We applied cell electrophoresis to detect the effect of anesthetics on membrane, and clarified the concentration - effect relationship and the term of reversibility. The cell electrophoretic mobility of rat erythrocytes decreased with time of incubation with intravenous anesthetics (thiopental or droperidol) at clinical concentrations and reached a minimum value of 25% reduction in 30 min. The effect changed gradually in the concentration range of 0.5-1000 microgram/ml of thiopental, and changed markedly with 0.3-1 microgram/ml of droperidol. Washing out of the anesthetics and subsequent incubation in serum-containing medium resulted in the complete recovery in the mobility when 5 microgram/ml thiopental or 1 microgram/ml droperidol was used. With high concentration of thiopental (100 microgram/ml) or droperidol (10 microgram/ml, however, unrecovered fraction of cells increased with time of treatment. The critical time for retaining the reversibility was about 2 hr.

Anesthetics↗