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Biomedical subjects

K Imai

Publications and source records attributed to K Imai.

At least 1,171 records · Page 65Linked to original sources
PubMed1988

Determination of flow and rate constants in a kinetic model of [99mTc]-hexamethyl-propylene amine oxime in the human brain.

The values for flow and rate constants for a kinetic model of [99mTc]-hexamethylpropyleneamine oxime (HM-PAO) distribution in the human brain were determined. The single-pass extraction ratio of HM-PAO was also determined in the rat brain by the indicator diffusion method; a value of 0.90 +/- 0.02 (mean +/- SEM, n = 5) was obtained. Time course data of brain activity and arterial blood activity of the tracer were fitted to a four compartment model: Values of blood flow and the first-order rate constants for backdiffusion of the diffusible tracer from brain to blood (k2), conversion of the lipophilic tracer to the hydrophilic one in brain (k3), and conversion of the diffusible tracer to the nondiffusible one in blood (k5) were determined. Conversion of hydrophilic tracer back to a lipophilic form in both blood and brain was assumed to be negligible during the course of the experiment. The values obtained for blood flow, k2, and k3 were, respectively, 0.40 +/- 0.03 ml/g/min, 0.38 +/- 0.04 min-1, and 0.92 +/- 0.05 min-1 in the gray matter (n = 4), and 0.23 +/- 0.01 ml/g/min, 0.17 +/- 0.01 min-1, and 1.01 +/- 0.05 min-1 in the white matter (n = 2) in patients with cerebrovascular disorder. The k5 value was 1.14 +/- 0.06 min-1 (n = 4). These experimentally determined values agree well with the theoretical ones previously reported by Lassen et al. The results suggest the relative constancy of the k3 and k5 values and the more prominent initial backdiffusion of the lipophilic HM-PAO from brain to blood in high flow regions compared to low flow regions.

Animals↗
PubMed1988

A case of early cancer in the gallbladder: immunohistological analysis with monoclonal antibodies.

A case of early cancer in the gallbladder is reported. The tumor was disclosed as an echogenic nodular lesion with irregular margin by ultrasonography and endoscopic retrograde cholangiography. Among several tumor markers, CA19-9 showed a slightly higher level (51 U/ml). An operation was carried out because of the tumor size (over 10 mm) and the coexistence of a gallstone. The tumor was a well differentiated tubular adenocarcinoma. In the carcinoma tissue, CA19-9 and YH206 antigens showed different staining patterns, the latter antigen being detected by the monoclonal antibody, YH206, established in our laboratory. Although CA19-9 was strongly positive in the non-cancerous gallbladder epithelial cells, the YH206 antigen was negative. A slight elevation of the CA19-9 level in the patient's serum was probably caused by a diffusion of the CA19-9 antigen from the gallbladder epithelial cells to the serum, due to inflammation. On the other hand, it is interesting to note that the YH206 antigen was not demonstrated in the non-cancerous gallbladder epithelial cells but was in the cancer tissue.

Adenocarcinoma↗
PubMed1988

Characterization and partial purification of a non-interferon macrophage activating factor produced by human leukemic T cell line.

Culture supernatants from several human leukemic T cell lines were found to contain a macrophage activating factor which enhanced hydrogen peroxide release from human peripheral blood monocyte-derived macrophages. The macrophage activating factor from a T cell line, CCRF-CEM, was characterized biochemically and compared with interferon-gamma, which is also an immunological product of T cells and has a potent macrophage activating activity. In contrast to interferon-gamma, the macrophage activating factor in the culture supernatants bound to an anion exchanger and did not adsorb onto concanavalin A gel. Culture supernatants and active fractions from chromatographies were essentially devoid of anti-viral activity. Anti-human interferon-gamma monoclonal antibody also failed to neutralize the macrophage activating factor from CCRF-CEM. MAF was eluted in the fractions with molecular weight of 40,000 to 60,000 on gel filtration in the presence of a detergent and a salt. MAF was partially purified to about 1,300-fold by the methods described above: chromatography with anion exchangers and gel filtration. It was concluded that MAF from CCRF-CEM was biochemically and immunologically different from interferon-gamma.

Chromatography, Ion Exchange↗
PubMed1988

Direct autoradiographic comparison of 99Tcm-HMPAO with 125I-IMP in experimental brain ischaemia.

Local cerebral blood flow (LCBF) images of HMPAO and IMP were directly compared in experimental brain ischaemia in the same rats using a double-tracer autoradiographic technique. Both images were identical in distribution throughout the whole flow areas. However, LCBF values were much lower in HMPAO than in IMP. The results suggest that HMPAO acts as a chemical microembolus in rat brain in both low and high flow areas; however, a quantitative flow measurement is difficult in an HMPAO study.

Amphetamines↗
PubMed1988

Isolation of genomic DNA controlling mouse melanoma antigen defined by monoclonal antibody.

We have isolated the genomic DNA controlling the expression of murine specific melanoma antigen by employing cosmid shuttle vector and monoclonal antibody. Transfection of the cosmid library derived from mouse melanoma cells into human melanomas and repeated cell sortings of the fluorescence-bright population enabled us to enrich the antigen-positive transfectants. We rescued a 34.8 kb DNA fragment from the transfectants by in vitro packaging and showed it to be responsible for the antigen expression. However, we noticed instability of the antigen expression when the selection pressure imposed by the cell sorting was removed. This seemed to be due to the fact that the insert DNA was preferentially deleted from this cosmid vector without loss of the vector sequence itself.

Animals↗
PubMed1988

The joint effects of two factors in the aetiology of oesophageal cancer in Japan.

A multifactorial approach to the aetiology of oesophageal cancer was made on the basis of a case-control study in Saitama prefecture, Japan. The joint risks of two factors were calculated directly from joint distributions, following a dichotomous exposure model. Three models of factor combinations were taken into account: two risk enhancing factors, two risk reducing factors, and risk enhancing and reducing factors. We observed remarkable risk elevations in the first model, and the observed joint risks were in the neighbourhood of the multiplicative products of single acting risks of individual factors. The highest odds ratios of about 10 or more were found with combinations of salty foods, excessive intake of rice and alcohol abuse. The second and third models also followed a multiplicative modification of risk. The lowest odds ratios of less than 0.2 were observed in the second model, with combinations of fruits and raw vegetables, fruits and seaweed, and raw vegetables and meat. In the third model, the increased risk caused by an enhancing factor was reduced proportionately to the presence of a risk reducing factor. Finally the dose-response relations of two factors were observed and shown to be categorised into three typical patterns of risk modification, following a three exposure level model. These patterns could be explained by both the dose-response relations of individual factors and the multiplicative modification of risk.

Aged↗
PubMed1988

A macrophage receptor for liver lysosomal beta-glucosidase.

beta-Glucosidase was purified from lysosomal membranes isolated from rat liver. Binding and uptake of the purified beta-glucosidase were mediated via an apparently single binding site on rat peritoneal macrophages. The number of sites and the Kd were 4.20 X 10(4)/cell and 1.00 X 10(-7) M, respectively. Neither of the processes was inhibited by ligands for mannose/fucose receptors, mannose 6-phosphate receptors, or scavenger receptors, or by other glycoproteins and sugar compounds. A portion of the beta-glucosidase taken up into the macrophages was degraded rapidly. These results suggested that liver lysosomal beta-glucosidase was endocytosed via a receptor not previously described.

Animals↗
PubMed1988

Effect of hypophysectomy on 17 alpha-hydroxylase activity in theca cells of the ovarian follicle in the Japanese quail.

The activity of 17 alpha-hydroxylase, a key enzyme for progesterone metabolism in avian follicles, was measured in cell-free homogenates of isolated theca cells of Japanese quail. Kinetic studies revealed that differences in enzyme activity in the largest and the second largest follicles were mainly due to differences in Vmax values. In order to investigate the mechanism of regulation of 17 alpha-hydroxylase activity, quail were hypophysectomized at various time periods during the ovulatory cycle, and 17 alpha-hydroxylase activity in theca homogenates was measured 4 h after surgery. Hypophysectomy at 8 h before the predicted time of ovulation, which is the time when the preovulatory luteinizing hormone (LH) surge is initiated, resulted in a significant decrease in enzyme activity. In contrast, activity was increased when the pituitary was removed 20 h before ovulation. Hypophysectomy 24 h before ovulation had no effect on enzyme activity.

Animals↗
PubMed1988

[Diagnosis of early cancer with monoclonal antibodies].

Monoclonal antibodies which have been utilized in the field of early diagnosis for cancer were reviewed. Monoclonal antibodies to ras oncogene product and to very high-molecular-weight MUSE 11 antigen were found to be useful for diagnosing some of the early carcinomas.

Antibodies, Monoclonal↗