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Biomedical subjects

T Hiraoka

Publications and source records attributed to T Hiraoka.

At least 19 recordsLinked to original sources
PubMed1992

[Development of a gel phantom for dose distributions by MR imager].

We reported a method of determining spatial dose distributions in tissue-equivalent phantoms using nuclear magnetic resonance imaging. To make a gel phantom, a cross-linked dextran gel (Sephadex G-200) was used as fixation agent of a ferrous sulphate solution. Although high quality images are obtained, the cost is very expensive to make the gel. We developed a new gel which is combined with an extra water absorbent polymer (Sumikagel N-100) and Sephadex G-200. The gel permits the determination of dose distributions for three dimensional treatment planning.

Ferrous Compounds↗
PubMed1992

Determination of ion recombination loss by two-voltage method for pulsed radiation beams.

The ion recombination loss is one of the most important correction factors for dosimetry using ionization chamber especially for the measurement of high-intensity pulsed radiation beam. The two-voltage method has been used frequently for the correction of ion recombination loss. Several ways to approximate the method are presented. Comparisons were carried out to check the validity of the approximation. Using four ionization chambers of different types and shapes, measurements were made to obtain the optimal value of the ratio for the two voltages.

Humans↗
PubMed1992

Promotion of hepatic metastases by liver resection in the rat.

In the early period following radical hepatectomy for hepatoma, recurrences in the remaining liver are frequently found. In regenerating liver, implantation and growth of tumour cells released into the portal system during surgical treatment might be promoted. We examined the relationship between liver regeneration and the formation of metastases following hepatic resection. Intraportal injections of rat ascites containing hepatoma AH130 cells at a concentration of 1 x 10(5) cells 0.2 ml-1 were made at various periods following two thirds liver resection in rats. Tumour cell injections immediately at 24 h after surgery resulted in an increased number of hepatic metastases compared with control animals. Tumour cell injections 2 weeks after hepatectomy, however, had no significant difference in effect compared with control rats. In contrast, tumour cells injected immediately after removal of half of the caudate lobe resulted in the same number of metastases as control animals. These results demonstrate that the number of artificially induced hepatic metastases was increased during an initial period of active liver regeneration and was proportional to the volume of hepatectomy. The effect of 5-fluorouracil (5FU) or mitomycin C (MMC) as inhibitors of hepatic regeneration on liver metastasis after hepatectomy was studied. The administration of 5FU (20 mg kg-1) or MMC (0.2 mg kg-1) immediately, 24 and 48 h after hepatectomy resulted in a marked reduction in metastatic lesions. The administration of 5FU caused delays in weight gain and decreases in the wet weight of remaining liver, while MMC had no effect on either. Accordingly, results of 5FU administration may be due to inhibitory effects on liver regeneration whilst that of MMC administration may be due to cytocidal antitumour effect. The effect of OK-432 as an immunoactivator on the implantation and growth of tumour cells in regenerating liver was also studied. Pretreatment with OK-432, 0.5 mg intraperitoneally on 7 consecutive days, had no effect on hepatic metastases. The pathophysiology of liver regeneration may enhance hematogenous hepatic metastasis and release of tumour cells during surgical manipulation may represent an important cause of recurrence following hepatic resection.

Animals↗
PubMed1992

Treatment of low density lipophorin with lipoprotein lipase: diacylglycerol content has no effect on dissociation of apolipophorin III from low-density lipophorin.

The mechanism of the conversion of low-density lipophorin (LDLp) to high-density lipophorin (HDLp) in long-distance flight insects was investigated using a lipoprotein lipase from a bacterium, Alcaligenes sp. Diacylglycerol of LDLp was steadily hydrolyzed in vitro by the lipase, resulting in a 90% loss of diacylglycerol from LDLp during incubation. The "lipase-treated LDLp" thus obtained still contained associated apolipophorin-III (apoLp-III). These data suggest that the dissociation of apoLp-III is independent of the depletion of diacylglycerol from LDLp, and that the decrease in particle diameter caused by the depletion of diacylglycerol does not force the dissociation of apoLp-III from the lipophorin particle. Some physico-chemical properties of the lipase-treated LDLp were measured.

Alcaligenes↗
PubMed1992

Effect of activated protein C on impaired fibrinolysis in rats with obstructive jaundice.

We studied the effect of activated protein C (APC) on impaired fibrinolysis using a rat model in which disseminated intravascular coagulation (DIC) is induced by the intravenous injection of endotoxin in rats with obstructive jaundice. An intravenous injection of endotoxin in rats with obstructive jaundice resulted in pulmonary hemorrhages and a marked increase in the plasma levels of tissue-type plasminogen activator (t-PA) antigen and plasminogen activator inhibitor activity. Prophylaxis with APC before the injection of endotoxin resulted in a decrease of the number of lung hemorrhages and an accelerated release of t-PA antigen. Thus, DIC in obstructive jaundice may be due to impairment of fibrinolysis and an increased susceptibility of endothelial cells to endotoxin. APC may be effective as a treatment for patients with obstructive jaundice associated with DIC.

Animals↗
PubMed1992

Platinum-diaminobenzidine reaction and its contribution to the quantitation of cytochrome oxidase activity.

The platinum-diaminobenzidine (Pt-DAB) reaction, which yields a black, electron-dense, insoluble, Pt-containing reaction product at the active site of cytochrome oxidase without postosmification, has been developed. This reaction permits us to quantitate the oxidase activity in an individual mitochondrion or in its constitutent part by the energy dispersive X-ray analysis (EDAX), based on the platinum atoms incorporated in the product.

3,3'-Diaminobenzidine↗
PubMed1992

Alpha-fetoprotein-producing pancreatic cancer--a case report and review of 28 cases.

The case of a female patient with an alpha-fetoprotein (AFP)-producing acinar cell carcinoma of the pancreas is reported, and 28 cases in the literature are reviewed. In our case, the serum AFP level declined drastically after removal of the tumor, but increased when widespread metastases appeared. AFP was detected in the cytoplasm of the cancer cells by immunohistochemical staining. Immunoelectron microscopic studies revealed AFP on the endoplasmic reticulum of the cancer cells. Of the 28 cases with AFP-producing pancreatic cancer, liver metastases were identified in 21 cases (76% overall). There was no correlation between the serum AFP level and liver metastases. Immunohistochemical studies revealed localization of AFP at the primary lesion in 6 out of eight cases tested. In cases of AFP-producing pancreatic cancer, serum AFP levels are useful for the diagnosis and as a marker for evaluating recurrent disease and therapeutic response, and for the management of gastrointestinal disease it should be remembered that some pancreatic cancers produce AFP.

Adenocarcinoma↗
PubMed1991

Synthesis of a 3-ether analogue of lipid A.

Lipid A 3-ether analogues were synthesized from allyl 2-deoxy-4,6-O-isopropylidene-2-trifluoroacetamido-alpha-D-glucopyr anoside and 3,4,6-tri-O-acetyl-2-trifluoroacetamido-alpha-D-glucopyranosyl bromide. The compound lost completely the endotoxic activity.

Animals↗
PubMed1991

Endotoxin-induced lung hemorrhages in obstructive jaundiced rats.

Endotoxemia in patients with biliary obstruction contributes to the high morbidity and mortality rates following surgery. We developed an animal model of disseminated intravascular coagulation (DIC) in rats on which bile duct ligation was performed following an injection of endotoxin (200 micrograms/kg bw). Macroscopic hemorrhages and microthrombi in the lung were found in jaundiced rats 6 hours after the injection of endotoxin and yet these phenomena were not found in non-jaundiced rats following an injection of the same amount of endotoxin. Coagulation studies also revealed characteristic findings of DIC in the jaundiced rats following the injection of endotoxin. This study confirms that obstructive jaundice is one of the main predisposing factors in the course of endotoxin-induced DIC.

Animals↗
PubMed1991

Synthesis of 2-deoxy-2-[(2,2-difluoro-3-hydroxytetradecanoyl)amino]-3-O- [(R)-3-(tetradecanoyloxy)tetradecanoyl]-D-glucopyranose 4-phosphate.

2-Deoxy-2-[(2,2-difluoro-3-hydroxytetradecanoyl)amino]-3-O-[(R)-3- (tetradecanoyloxy)tetradecanoyl]-D-glucopyranose 4-phosphates (9H,L) were synthesized from allyl 2-amino-2-deoxy-4,6-O- isopropylidene-beta-D-glucopyranoside (1), (+/-)-3-[(benzyloxycarbonyl)oxy]-2,2-difluorotetradecanoic acid, and (R)-3- (tetradecanoyloxy)tetradecanoic acid. Both compounds 9H and 9L were more active than GLA-60 for the prostaglandin D2 releasing test on macrophages.

Animals↗
PubMed1991

Enzyme-induced aggregation and disaggregation of tumor cells via the cell surface glycocalyx in association with deoxyribonucleic acid.

Serine proteases cause aggregation of the rat ascites tumor cell lines AH-130, AH-109A and YS in vitro, and the tumor cell aggregates are dissolved by treatment with DNase I. We previously demonstrated that these events played a critical role in the augmentation or reduction of experimental blood-borne metastasis of these cell lines. In the present study, the ultrastructural features of this protease-dependent aggregation were analysed. Transmission and scanning electron microscopy revealed that after the protease treatment each tumor cell was surrounded by a thin membranous (sleeve-like) structure. This sleeve-like structure was stained with ruthenium red to an intensity similar to the cell surface of the control. Adjacent cells became attached to each other with microvilli via this fine structure. Immuno-electron microscopy revealed DNA antigen as dense patches on the sleeve-like structure or as faint and diffuse deposits on the outer surface of the cells by indirect immunoperoxidase staining using an anti-DNA monoclonal antibody. Both the sleeve-like structure and immunopositive deposits disappeared after treatment with DNase I. Neither cell viability nor the normal ultrastructure of their organelles was influenced by the enzyme treatment. These results indicate that serine protease-induced tumor cell aggregation is due to cellular contact via the sleeve-like structure, which probably originates from the cell surface glycocalyx in association with DNA molecules of unknown origin.

Animals↗
PubMed1991

Catecholamines in experimentally growth-retarded rat fetus.

This study was designed to evaluate the sympathoadrenal system in rat IUGR fetuses prepared by the Wigglesworth method. Samples were obtained on day 20 of gestation. In the amniotic fluid, concentrations of norepinephrine (NE) and particularly epinephrine (E) were significantly higher in IUGR fetuses than in normally developed fetuses (NE: p less than 0.05, E: p less than 0.01). L-Dopa and three catecholamines in the adrenal glands were decreased in IUGR fetuses. The mol ratios (L-dopa: dopamine: NE: E) were 1: 4: 35: 63 in IUGR fetuses and 1: 5: 39: 87 in normal fetuses. The ratio for epinephrine to L-dopa was significantly lower in IUGR fetuses (p less than 0.05). Adrenal phenylethanolamine-N-methyltransferase activities showed no difference between the two groups. From these results, adrenal epinephrine synthesis in IUGR fetuses was thought to be normal. Because of the depletion of adrenal epinephrine in IUGR fetuses, the plasma epinephrine concentrations were significantly lower after acute hemorrhagic shock (p less than 0.01). However, the plasma concentrations of dopamine and norepinephrine were significantly higher (dopamine: p less than 0.01, NE: p less than 0.001) in IUGR fetuses. These findings suggest that the hypersecretion of adrenal epinephrine is a protective response to chronic stress and the decrease of adrenal epinephrine may be a causative factor for the reduced reserves in the defense mechanism of IUGR fetuses.

Adrenal Glands↗
PubMed1991

X-ray sensitivity of fibroblast cell strains derived from atomic bomb survivors with and without breast cancer.

Fibroblasts were established in vitro from skin biopsies obtained from 55 women and 1 man with or without breast cancer and with or without exposure to radiations from the atomic bomb (A-bomb) explosion in Hiroshima. The radiosensitivity of these cells was evaluated by clonogenic assays after exposure to X-rays. Dose-response curves were fitted to a multitarget model, S/S0 = A[1-(1-e-D/D0)N]. There was no difference in the means or variances of radiosensitivity between exposed and nonexposed groups, or between groups with and without breast cancer.

Breast Neoplasms↗