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Biomedical subjects

O Yamamoto

Publications and source records attributed to O Yamamoto.

At least 127 records · Page 7Linked to original sources
PubMed1991

RBE of HTO to 60Co gamma-rays for cell killing of a radioresistant E. coli harboring plasmid.

Radioresistant E. coli TGl harboring pUC 18 plasmid which was Ampicillin-resistant was exposed to 60Co gamma-rays or 3H beta-rays in saline to determine whether the relative biological effectiveness of 3H beta-rays is higher than one. After exposure to 60Co gamma-rays at a dose rate of 0.465 Gy/min, the D0 by colony formation was 145 Gy in the presence of Ampicillin in or absence from the agar medium; whereas, the D0 was calculated as 118 Gy with and without Ampicillin after exposure to 3H beta-rays at a dose rate of 0.431 Gy/min. The relative biological effectiveness established for 3H beta-rays to 60Co gamma-rays was 1.23. The reason for the higher effectiveness of 3H beta-rays as compared to the reference 60Co gamma-rays is discussed in terms of nascent 0 production.

Beta Particles↗
PubMed1991

Carcinogenic effects of tritiated water (HTO) in mice: in comparison to those of neutrons and gamma-rays.

A series of experiments was carried out using female (C57BL/6N x C3H/He)F1 mice (BCF1) to assess the carcinogenic effect of tritiated water (HTO) following a preliminary experiment in which the acute effect of HTO was studied in young female mice of C57BL/6L strain in an attempt to gain basic information on the long-term experiment, and the results were compared with those of fission spectrum neutrons and gamma-rays. The obtained findings are summarized as follows. 1) C57BL/6N mice receiving a single intraperitoneal (i.p.) injection of HTO, 7.4 x 10(8) Bq (20 mCi) or more, died of bone marrow failure within 20 days. 2) In long-term experiment, BCF1 mice given 1.4 x 10(8) Bq to 5.6 x 10(8) Bq developed solid tumors in a variety of tissues but with no obvious dose dependency. 3) The fractionated exposure of 7.4 x 10(8) Bq (1.9 x 10(8) each, at 7-day intervals) was highly effective in induction of malignant T-cell lymphomas (85%) with a shorter latency than that of a single exposure (15%). 4) A protracted irradiation of 0.27 Gy of 137Cs, designed to simulate the decreasing absorption rate with time after a single i.p. injection of an equivalent dose of HTO resulted in a drastic reduction in induction rate of ovarian tumors as compared with that of an acute 60Co gamma irradiation. 5) The carcinogenic potential of HTO, given as a single i.p. injection, was quite similar to that of acute 60Co gamma ray irradiation at both 2.7 Gy and 0.27 Gy levels. On the other hand, the effect of HTO was slightly higher than that of protracted gamma-ray irradiation. 6) 252Cf fission neutrons was found to be more potent in tumor induction than gamma-rays or HTO beta-rays under the present experimental conditions.

Animals↗
PubMed1991

A scanning electron microscopic study of postnatal development of rat peribiliary plexus.

Hepatic microcirculation in the developing stages is not fully clarified. This study aimed at clarifying the development of hepatic microcirculation, especially peribiliary vascular plexuses, in neonatal rats by corrosion cast procedures and scanning electron microscopy. Peribiliary vascular plexuses of large bile ducts at the hilus of 1-day-old rats showed a simple capillary network that directly poured into the portal vein. The hepatic artery promptly tapered down into many small branches and ended in sinusoids or capillary plexuses around portal vein branches near the hilus. Neither apparent hepatic artery branches nor peribiliary vascular plexuses were found in the peripheral areas of the liver. On the seventh day, very loose peribiliary vascular plexuses and small hepatic artery branches appeared up to the peripheral portal tracts, and the peribiliary vascular plexuses of large bile ducts were still capillary networks. After the seventh day, peribiliary vascular plexuses of large and medium-sized portal tracts often poured into side branches of the portal vein rather than directly into the portal vein as shown in the rats from the first day mentioned above. Peribiliary vascular plexuses of the large bile duct in 2-week-old rats showed a double layer, that is, an outer layer composed of arteries and veins and an inner layer of capillary vessels, that resembled peribiliary vascular plexuses of adult livers. After nearly 4 wk, hepatic microcirculations had almost fully developed into those of adult rats. It was concluded that the gradual postnatal development of the hepatic arterial system and the peribiliary vascular plexuses occurred in parallel with the maturation of the intrahepatic biliary trees.

Aging↗
PubMed1991

Morphological changes of hepatic microcirculation in experimental rat cirrhosis: a scanning electron microscopic study.

Morphological changes of hepatic microcirculation, especially peribiliary plexus, in experimental rat cirrhosis that resulted from the repeated intraperitoneal injections of N-diethylnitrosamine, 100 mg/kg body weight/one shot/week, were examined by scanning electron microscope. Control rats were treated with saline. Whole blood vessels of the rats were perfused by saline and stuffed with methylmethacrylated resin. Multiple nodular changes were seen in the livers after the five injections (5 wk) of N-diethylnitrosamine, and diffuse nodular transformations mimicking human cirrhosis after six injections (6 wk) were also seen. Overall changes in experimental rats were numerous vascular channels mainly composed of venous branches around the parenchymal nodules, increased arterioportal anastomoses and flattening of veins, especially hepatic vein branches. Peribiliary plexuses of the experimental rats were much richer in the vessels than those of the controls, and many dilated veins, ramified from portal vein branches, were present in the former. Direct connections between peribiliary plexuses and sinusoids or between peribiliary plexuses and portal veins increased in the experimental rats. Studies concerning microcirculatory changes of peribiliary plexuses in experimental rat cirrhosis are rare. It was concluded that the abnormal peribiliary plexuses in this experimental series might participate in a collateral circulation under a state of portal hypertension.

Animals↗
PubMed1990

Three-dimensional observation of the rat endocrine pancreas by a scanning electron microscope.

A three-dimensional observation was performed on chemically digested rat pancreata and vascular corrosion casts of it with a scanning electron microscope. The Langerhans islets were sporadically situated in the exocrine tissue and were surrounded by the fibrous capsule, which was so tough that it could not be chemically digested easily. This capsule was considered to play different roles in the collection of the endocrine cells in a functional unit, in the prevention of secreted hormones spreading into the adjacent exocrine and stromal tissue, in the support of the microvascular structure, and in the protection for the islet cells from the pancreatic enzymes, which are leaking into the stromal spaces physiologically. The microvascular structure of the islet, disclosed by the corrosion vascular casts, showed afferent vessels branching into the capillaries at the periphery of the islet and entering the core of it by a twisted course. These findings were considered to be related to the islet cell distribution, that is, A and D cells are at the periphery of the islet and B cells at the center of it. This might support the existence of a hormonal regulating mechanism among endocrine cells. In addition, the efferent vessels from the islet that communicate to the vascular network of the exocrine tissue might suggest that the endocrine system also regulates the exocrine function in a circulatory dynamic state.

Animals↗
PubMed1990

Scanning electron microscopic examinations of microvascular casts of the rat liver and bile duct.

Microvascular features of normal rat livers and bile duct system were examined with the vascular casts using methacrylated resin. Portal vein branches not only showed regular tapered down bifurcations but also had many side branches, some of which were directly connected with sinusoids. Terminations of hepatic arterial branches were divided into three types: 1) Many branches pouring into peribiliary capillary plexus (PBP), 2) branches directly pouring into periportal sinusoids and/or peripheral portal vein branches via arterio-portal anastomoses, and 3) anastomoses with periportal vascular plexus. PBP was composed of rich vascular networks. In large portal tracts, the plexus showed two layers, that is, the inner layer made up of a close network of capillary vessels and the outer layer consisting of a loose network of arteries and veins, while the PBP in the small portal tracts was composed of only a single layer of loose capillary network. Transitional features of these two patterns were found in the medium-sized portal tracts. PBP was supplied by afferent vessels from the interlobular hepatic artery as described above, and were directly connected with interlobular branches of the portal vein (internal root). The extrahepatic bile duct revealed a much richer vasculature than the intrahepatic bile duct. Both arterial and venous branches were ramified at almost right angle from a pair of arteries and veins running parallel with the bile duct. Occasional strictures, which might have been sphincter portions of the media, were noted at the branching sites of the artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Three-dimensional architecture of the microvasculature in the rat foot-pad, with special reference to vasculature around the eccrine sweat glands. A scanning electron-microscopic study of corrosion casts.

The entire microvascular architecture in rat foot-pads including that of eccrine sweat glands was studied by scanning electron microscopy using a vascular corrosion-cast replication technique. In the central roofs of the pads, particularly elaborate capillary networks were arranged in rows perpendicular to the long axis of the foot. In the marginal regions of the pads, simple networks of capillaries were arranged in lamellar sheets parallel to the surface of the sole of the foot. Complex spongy networks of vascular trees were observed in the subcutaneous layer of the pads. These vessels were supplied by the pad artery, and then, after forming capillary networks in the roofs of the pads, they drained into the metatarsal vein. Rod-shaped cages of capillaries were observed around the eccrine sweat glands. One descending arteriole, arising from a connecting arteriole, and a few venules were connected with these capillary cages at their upper and lateral sides. Occasional arterio-venous and veno-venous anastomoses were also observed around the eccrine sweat glands. This microvascular architecture may adjust well to the mechanical and physiological conditions encountered in the foot-pads. The relation of the microvascular architecture around the eccrine sweat glands with their development is also discussed.

Animals↗
PubMed1990

Changes in the hormone receptors of human breast carcinoma xenografts in nude mice by treatment with cytotoxic agents.

We examined the effect of chemotherapeutic agents on the estrogen receptors (ER) of breast carcinomas in vivo using human breast carcinoma strains (Br-10, T-61) serially transplanted into nude mice. When the tumor size reached approximately 1 X 1 X 1 cm, mitomycin C (MMC) at doses of 1, 2 and 4.5 mg/kg and cyclophosphamide (CPA) at a dose of 120 mg/kg, were administered once intraperitoneally, and the ERs of the tumors were measured sequentially by the dextran-coated charcoal method. Four days after the MMC administration at above doses, the binding sites of ER in Br-10 were not reduced and binding affinity was not affected. When the changes in ER content with time after the treatment with 4.5 mg/kg MMC and 120 mg/kg CPA were investigated, the ER content was found to be stable until 4 days after the treatment with both drugs, although the growth of T-61 had been significantly inhibited by the drugs. From these findings, it seems reasonable to initiate chemotherapy before endocrine therapy, since the chemotherapeutic agents did not reduce the ER content of the breast cancer strains.

Animals↗
PubMed1990

HTO oral administration in mice. I: Threshold dose rate for haematopoietic death.

Tritiated water in various concentrations was orally administered continuously to (C57BL/6N and C3H/He)F1 female mice in a closed animal chamber. Tritium radioactivity in various organ tissues was measured periodically after initiating tritiated water intake using an automatic sample combustion system and a liquid scintillation counter. After 7 days the specific radioactivity reached a plateau. These data allowed absorbed organ doses to be estimated. Within a range of 1.48 x 10(11) to 5.92 x 10(11) Bq/dm3 as the concentration of tritiated water in drinking water, the time of death after initiating the administration was about 2 weeks, a typical time for haematopoietic death. A linear relationship of times of death with tritiated water concentrations in drinking water was observed, on a log-log scale, between 1.85 x 10(10) Bq/dm3 and 1.48 x 10(11) Bq/dm3. At concentrations lower than 9.25 x 10(9) Bq/dm3, mice no longer died from haematopoietic failure. We conclude, therefore, that there should be a threshold dose rate for haematopoietic death.

Animals↗
PubMed1990

An autopsy case of peritoneal malignant mesothelioma in a radiation technologist.

A case of peritoneal malignant mesothelioma in a radiation technologist, who had worked in this field for 34 years, is reported. Histopathologically, a biopsy specimen from the retroperitoneal tumor revealed a biphasic type of malignant mesothelioma. Electron microscopy disclosed that the tumor cells contained prominent microvilli, basal laminae adjacent to the stroma, junctional complexes, desmosomes, tonofilaments, clusters of glycogen granules, well developed rough endoplasmic reticulum (RER), confronting cisternae showing direct continuity with the RER and membrane-bound granules suggestive of secretory activity. No increased amount of asbestos was detected in autopsied lung material or the peritoneal mesothelioma. The estimated cumulative dose of occupational irradiation was calculated to be about 40 to 50 rad at most. Irradiation was discussed in relation to the etiology of the peritoneal mesothelioma.

Autopsy↗
PubMed1990

Formation of nerve twig-like nests and schwannoma in an unusual case of neurofibroma.

A case of unusual neurofibroma in an 18-year-old Japanese male is reported. The histology of the tumor was characterized by nerve twig-like nests intermingled with fascicular bundles. In the central portion, the tumor also contained a lobular lesion showing features characteristic of schwannoma. Immunohistochemically, the tumor cells in both the nests and the lobular lesion demonstrated a mostly positive reaction for S-100 protein. S-100 protein-positive and -negative cells were observed in equal numbers in the fascicular bundles surrounding the nests. This unusual nerve sheath tumor in which the S-100 protein-positive cells form both nerve twig-like nests and lobular schwannoma has not been reported previously. The origin of the S-100 protein-positive cells in the two lesions is also discussed.

Adolescent↗
PubMed1990

[A case of psoriatic arthropathy complicated with clinical feature of ankylosing spondylitis].

UNLABELLED: A 25 years old man with psoriatic arthropathy complicated with clinical feature of ankylosing spondylitis was reported. 230 Japanese cases of psoriatic arthropathy were discussed. RESULT: 1) commoner in male 2) the cases that skin lesions were prior to arthritis and the cases that arthritis was prior to skin lesions were almost the same number 3) rheumatoid factor was seropositive in 17% of the cases 4) HLA-B27 was present in 9 of 50 cases and 7 of these 9 cases had central type arthritis 5) the cases had accompanied nail dystrophies in a high rate 6) concerning on skin lesion, many cases had atypical psoriatic lesion 7) 21.1% of the cases had central type arthritis 8) there were no certain effective therapy 9) prognosis of central type cases were relatively worse.

Adult↗
PubMed1990

Low-dose-rate effect of tritium beta-rays on transfection activity of phage DNA related to an oxidative species different from .OH, HO2. O2-., and H2O2.

In order to study the low-dose-rate effect of tritium beta-irradiation, we exposed single-stranded DNA of M13 mp10 phage to purified tritiated water. The beta-irradiated DNA was then transfected to E. coli K12 JM101. The lower the radiation dose rate, the more the transfection activity decreased. After the low-dose-rate effect was confirmed, the characteristics of tritiated water were also studied. The formation of an active oxidative species different from .OH, HO2., O2-., and H2O2 was found in the tritiated water by using UV spectrometry and luminescence measurement. Attributing it to nescent oxygen by reason of the production of the epoxide from mesityl oxide, we discussed the low-dose-rate effect from the viewpoint that the yield of the DNA modification could be relatively higher than that of the O2 formation in a competition reaction when the dose rate was lower.

Bacteriophages↗
PubMed1989

Inhibition of H+,K+-ATPase by methyl(E)-2-(3,4-dimethoxystyryl)-benzimidazole-4-carboxylate (ALE-36).

ALE-36, as well as omeprazole and SCH 28080, markedly inhibited the [14C]aminopyrine (AP) accumulation induced by dibutyryl cyclic AMP (dbcAMP) and H+,K+-ATPase activity in a concentration-dependent manner. The inhibitory effect of omeprazole on the dbcAMP-induced [14C]AP accumulation was reversed by treatment with beta-mercaptoethanol, but those of ALE-36 and SCH 28080 were not. ALE-36 and SCH 28080 did not inhibit dog renal Na+,K+-ATPase activity, while omeprazole and ouabain did inhibit this enzyme activity. These results suggest that the inhibitory action of ALE-36 on acid secretion is due to the specific inhibition of gastric H+,K+-ATPase, the manner being different from in the case of omeprazole.

Adenosine Triphosphatases↗
PubMed1989

Effects of ALE-36 on gastric secretion, and gastric and duodenal ulcers induced in rats.

We examined the antisecretory and anti-ulcer effects of ALE-36 in rats. ALE-36 (3-30 mg/kg) dose-dependently inhibited gastric acid secretion in pylorus-ligated rats. However, the agent apparently increased the volume of gastric juice, and the Na+ and Cl- ion outputs. These changes were almost completely prevented by pretreatment with indomethacin, suggesting that endogenous prostaglandins in the gastric mucosa mediated the changes. Pretreatment with ALE-36 (3-30 mg/kg) inhibited the development of stress-, aspirin-, and indomethacin-induced gastric lesions, and mepirizole-induced duodenal ulcers. Repeated administration of ALE-36 significantly accelerated the healing of gastric ulcers induced by thermocautery.

Animals↗