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Biomedical subjects

N Yamamura

Publications and source records attributed to N Yamamura.

At least 37 records · Page 2Linked to original sources
PubMed1998

Evaluation of [1-11C]octanoate as a new radiopharmaceutical for assessing liver function using positron emission tomography.

[1-11C]Octanoate was evaluated as a new radiopharmaceutical for the evaluation of liver function using positron emission tomography (PET). In biodistribution studies with normal mice, [1-11C]octanoate was rapidly taken up by the liver. [1-11C]Octanoate in the liver was present in the parenchymal cells and was predominantly metabolized via beta-oxidation followed by its rapid clearance. In the CCl4-treated mice, [1-11C]octanoate showed significantly slower hepatic clearance than that in the controls. In PET studies using rats, the time-radioactivity curves in the liver showed a two-phase decrease, and compared with the normal rat, the CCl4-treated rat showed a slower hepatic half-clearance time for the first phase, which is related to beta-oxidation metabolism. A preliminary PET study of [1-11C]octanoate metabolism in a normal volunteer was consistent with these animal studies. The present study showed that metabolism of [1-11C]octanoate in the liver was influenced by beta-oxidation, and it is advantageous to use [1-11C]octanoate clinically as a regional liver-function diagnostic agent in conjunction with PET.

Acetates↗
PubMed1998

Case report: Steatonecrosis in the upper abdomen following transcatheter arterial embolization for hepatocellular carcinoma.

A 66-year-old female with liver cirrhosis was treated by transcatheter arterial embolization (TAE) for a small hepatocellular carcinoma. She developed steatonecrosis with tenderness which occurred in the upper abdomen after TAE. The hepatic falciform artery from the middle hepatic artery was detected by arteriography. Necrosis in the upper abdomen was considered to be due to ischaemic changes caused by micromaterials for embolization of this artery, injuries of hepatic arterial endothelia slowly caused by carcinostatics, and chemotoxicity. It was considered that such complication as observed in this patient should be taken into consideration when performing TAE.

Aged↗
PubMed1997

[David's operation for aortic regurgitation associated with annulo-aortic ectasia].

A 54-year-old man with AR due to AAE underwent the replacement of ascending aorta by sparing an aortic valve (David operation). Under cardiopulmonary bypass, the aneurysmal aorta and the all three sinuses of valsalva were excised, leaving 5 mm of arterial wall attached to the aortic valve. The aortic valve was reimplanted inside a Dacron graft (28 mm Hemashield) which was calculated by aortic valve leaflet height as well as from the size of LVOT. The patient has survived the operative procedure and showed uneventful recovery. We believe this new procedure preserving the native aortic valve is useful for preventing from some complications associated with an artificial heart valve and improvement of QOL of patient.

Aorta↗
PubMed1997

[Japanese cases of hyperostosis frontalis interna].

Although hyperostosis frontalis interna is common in the western countries, it has been rarely reported in the literature in Japan. We had a chance to observe 5 cases diagnosed as hyperostosis frontalis interna. They were found among 10,902 patients who came to our hospital from August 1, 1993 to September 30, 1995. All the patients in these five cases are females aged 67 to 85 (mean = 74.2 years). Four of the 5 cases had been treated as hypertension, 2 as diabetes mellitus, and 1 as hyperlipoidemia. Two cases were accompanied by unruptured aneurysms. The pathology of one case accompanied by chronic subdural hematoma revealed no apparent development of Haversian systems of bone. It seems that the prevalence of this disease in Japan would increase from now on due to the fact that the life style and the diet among Japanese people has been getting westernized.

Age Factors↗
PubMed1996

Autoimmune chronic pancreatitis simulating pancreatic lymphoma.

A 51-yr-old man, who presented with diabetes mellitus, abdominal pain, inguinal lymphadenopathy, and diffuse enlargement of the whole pancreas on ultrasonography, was at first thought to have pancreatic lymphoma. Chemotherapy including steroid was carried out successfully, although the definitive diagnosis of lymphoma was not made. However, on follow-up, we realized that both laboratory findings, such as hyperglobulinemia and autoantibody-positive results, and radiographic features in this case were very similar to those of a case of autoimmune pancreatitis recently reported by Yoshida et al. (Dig Dis Sci 1995;40:1561-8). When the disease recurred, therefore, treatment with steroid alone was performed with an excellent result. We report a case of autoimmune pancreatitis simulating primary pancreatic lymphoma.

Autoimmune Diseases↗
PubMed1995

Evaluation of radioiodinated iodoclorgyline as a SPECT radiopharmaceutical for MAO-A in the brain.

An in vivo estimation of the newly synthesized MAO-A specific inhibitor, [125I]-labeled N-[3(2,4-dichloro-6-iodophenoxy)propyl]-N-methyl-2- propynylamine ([125I]-iodoclorgyline), was performed. Retention of the radioactivity of this radioligand was observed in the brain from 1 h post-injection. Pretreatments with clorgyline and l-deprenyl showed selective binding of [125I]-iodoclorgyline to MAO-A in the brain at 24 h post-injection. Moreover, a good correlation (r = 0.907) between the uptake of [125I]-iodoclorgyline and MAO-A enzyme activity in the cortex was observed in the pretreatment study with several doses of clorgyline. Although improvement to increase the brain/blood ratio is desirable because of slow blood clearance of the radioactivity, radioiodinated iodoclorgyline may serve as a useful SPECT radiopharmaceutical for quantitative analysis of MAO-A in the brain.

Animals↗
PubMed1993

Alteration of eicosanoid production in the sensitized guinea pig lung by CS-518.

The effects of CS-518 (sodium 2-(1-imidazolylmethyl)-4,5-dihydrobenzo [b]thiophene-6-carboxylate), a thromboxane A2 synthase inhibitor, on changes in arachidonic acid metabolism were investigated in the lung of actively sensitized guinea pigs. Antigen challenge enhanced the production of thromboxane A2 as well as histamine and peptide leukotrienes in lung fragments. Exogenous leukotriene D4 also stimulated significant thromboxane A2 production in the non-sensitized lung in vitro. CS-518 was effective in preventing the thromboxane A2 production induced by either antigen or leukotriene D4, and the IC50 values were 90 and 7.5 ng/ml (320 and 27 nM), respectively. CS-518 markedly potentiated the production of prostaglandin E2 and I2 with slight inhibition of leukotriene formation, but indomethacin significantly stimulated leukotriene production. When CS-518 was administered orally, it induced long-lasting inhibition of thromboxane A2 production and potentiation of prostaglandin I2 production in guinea pig lung. Thus, CS-518 not only inhibited thromboxane production but also improved the change in arachidonic acid metabolism in the guinea pig bronchoalveolar tissue during allergic reaction in vivo as well as in vitro, which suggests amelioration of the asthmatic condition.

Administration, Oral↗
PubMed1993

Changes in plasma and urinary 11-dehydrothromboxane B2 in healthy subjects produced by oral CS-518, a novel thromboxane synthase inhibitor.

When 50 mg CS-518, a novel thromboxane (TX) A2 synthase inhibitor, was orally administered to healthy male volunteers, the plasma concentration of CS-518 peaked after 0.5 h and then decreased with a half-life of 0.44 h. There was no significant change in the plasma concentration of circulating TXB2, whereas that of circulating 11-dehydrothromboxane B2 (11-dhTXB2), an enzymatic metabolite of TXB2, was significantly decreased from 0.5 h to 24 h after administration; the maximal decrease to about 25% of the pre-dose value was found at 6 h. After CS-518 100 mg b.d. for 4.5 days, plasma 11-dhTXB2 was suppressed to the same extent as after the single dose of 50 mg from 6 h after the initial dose throughout the administration period. The urinary excretion of 11-dhTXB2 corrected for the creatinine level was significantly decreased by 70-84% throughout the treatment. These results suggest that CS-518 causes long-lasting inhibition of TXA2 synthase despite its rapid elimination from plasma, and that circulating 11-dhTXB2 in plasma and its urinary excretion can serve as a quantitative index of TXA2 synthase inhibition in vivo by CS-518.

Administration, Oral↗
PubMed1991

Why don't all termite species have a sterile worker caste?

No general theory explains why a sterile worker caste is not found in all species of both Hymenoptera and Isoptera (Insecta). Recent empirical finding show that, in the termites (Isoptera), feeding outside the nest correlates well with the evolution of the sterile (true) worker caste from the non-sterile (false) worker caste. Here we explain the connection between food-nest separation and true worker evolution in termites, providing a general theory on the restricted distribution of the sterile worker caste in the Isoptera. A cost-benefit model suggests that there is a critical level of nest stability above which natural selection favours true workers over false workers, irrespective of genetical relatedness. Because food-nest separation tends to increase nest stability, this theoretical result implies that the less a termite species consumes its nest as food, the more likely is its nest stability to fall above the critical level and a true worker caste will evolve.

Animals↗
PubMed1990

Autogenous and anautogenous mosquitoes: a mathematical analysis of reproductive strategies.

A mathematical model is presented to compare the relative advantage of an anautogenous mosquito population (in which females blood feed throughout life) with an obligate autogenous population (in which females do not feed on blood for the first oviposition). The advantage is measured by the intrinsic rate of natural increase. Autogeny was more advantageous than anautogeny when host searching time (ts), the ratio of the fecundity of the first autogenous to anautogenous oviposition (p), the fecundity in one anautogenous oviposition (n), or the instantaneous death rate of the adult population (D) was large, or when the preimaginal period (xo), the instantaneous death rate during the preimaginal period (D'), or survival during blood feeding (s) was low. The parameters most sensitive to the advantage of autogeny were ts, p, and s. The value of n was insensitive, and xo, D, and D' were intermediately sensitive to autogeny. Conditions when autogeny was advantageous were equivalent to conditions conducive to high autogeny rates in facultatively autogenous species, which alter the expression of autogeny depending upon environmental stimuli. Data on several facultatively autogenous species are discussed qualitatively and quantitatively to demonstrate the utility of our model in considering the evolution of autogeny and the autogeny rate.

Animals↗
PubMed1989

[Adult T-cell leukemia with vertebral bone tumor and acute transverse myelopathy].

We describe a case of adult T-cell leukemia (ATL) with vertebral bone invasion, who developed acute paraplegia and responded well to irradiation and combined chemotherapy. A 36-year-old man born in Tsushima Island was admitted to our hospital in May 1987, because of a sudden onset of paraplegia, hypesthesia below the level of 7th thoracic vertebra and vesicorectal disturbance. The white blood cell count was 9,500/microliter with 16% of abnormal lymphocytes showing lobulated nuclei. The surface marker analysis revealed that CD3, CD4, CD8 and CD25 positive cells were 88.1, 83.9, 6.4 and 1.3% of the peripheral mononuclear cells, respectively. Anti-ATLA antibody was positive. Serum calcium level was elevated. Bone scintigraphy showed multiple vertebral bone lesions. Vertebral bone mass and a compressed spinal cord in the 7th thoracic level were confirmed by CT scanning and MR imaging. Cerebral spinal fluid was negative for tumor cells. A diagnosis of ATL was made. Irradiation and combination chemotherapy improved bone lesions and neurological signs and the disease was well controlled by maintenance chemotherapy up to the present (August, 1988).

Acute Disease↗
PubMed1982

A case of acute non-A, non-B sporadic hepatitis with evolution of liver cirrhosis on serial histologic follow-up.

Progression of acute non-A, non-B (NANB) posttransfusion hepatitis to liver cirrhosis has been well recognized as in hepatitis B infection, whereas no progression of acute NANB sporadic hepatitis to liver cirrhosis has yet been documented. We reported a 29-year-old male with prolonged transaminase elevations in whom acute NANB sporadic hepatitis progressed to histologically confirmed cirrhosis during follow-up of about 3 years. It is suggested that some of the cryptogenic cirrhosis of non-B type may develop from acute NANB sporadic hepatitis and long-term observation is also needed in patients with acute hepatitis of this category.

Adult↗