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Biomedical subjects

N Shimada

Publications and source records attributed to N Shimada.

At least 217 records · Page 12Linked to original sources
PubMed1990

Differences in ischemia-induced accumulation of amino acids in the cat cortex.

It is well established that excitatory amino acid neurotransmitters are extensively liberated during ischemia and that they have neurotoxic properties contributing to neuronal injury. To study changes in the liberation of excitatory and other amino acids during cerebral ischemia, we measured their extracellular concentrations and related them to blood flow levels and electrophysiologic activity (electrocorticogram and auditory evoked potentials) before and for up to 2 hours after multiple cerebral vessel occlusion in 14 anesthetized cats. Blood flow levels between 0 and 43 ml/100 g/min were reached. Concentrations of the excitatory amino acid neurotransmitters increased most (aspartate 10-fold, glutamate 30-fold, and gamma-aminobutyric acid 300-fold compared with control values) below a blood flow threshold of 20 ml/100 g/min. The total power of the electrocorticogram and the amplitude of the auditory evoked potentials were affected below the same blood flow threshold. In contrast, concentrations of the nontransmitter amino acids taurine, alanine, asparagine, serine, and glutamine increased 1.5-5-fold as blood flow decreased, while concentrations of the essential amino acids phenylalanine, valine, leucine, and isoleucine did not change during cerebral ischemia. The great increases in concentrations of the excitatory amino acid neurotransmitters below a blood flow threshold close to that for functional disturbance is in accordance with the role of these amino acids in ischemic cell damage. Their release at blood flow levels compatible with cell survival and the increase in their concentrations with severity and duration of cerebral ischemia imply that excitotoxic antagonists may have potential as therapeutic agents.

Amino Acids↗
PubMed1990

[Experimental investigations of the propagation mechanism and the nerve regulatory mechanism of the interdigestive migrating electric complex in intestinal movement].

Segments and Thirty-Vella type loops of the small intestine of dogs were prepared, and the excitation propagation pattern of the interdigestive migrating electric complex (IMEC) was observed by electromyography. The nerve regulatory mechanism in intestinal movement was investigated. The results indicated that first, the frequency of the basic electric rhythm (BER) is controlled so that a downward gradient is formed from the upper to the lower intestine, but this gradient continues to be controlled by a two-dimensional control mechanism involving parietal factors and extrinsic nerves due to transection of the intestines and damage to the extrinsic nerves in the dominant region. However, propagation of the IMEC in the small intestine appeared to be regulated by a combination of the two-dimensional control mechanism involving extrinsic and parietal nerves corresponding to the BER control mechanism. It was clear that the propagation mechanism of IMEC is related to the BER frequency, and propagation of the IMEC is downward in accordance with the frequency gradient of BER.

Animals↗
PubMed1990

Antiviral effect of oxetanocin G against guinea pig cytomegalovirus infection in vitro and in vivo.

The antiviral activity of a new guanosine analog, 9-(2-deoxy-2-hydroxymethyl-beta-D-erythrooxetanosyl)guanine (OXT-G), against guinea pig cytomegalovirus (GPCMV) was evaluated both in vitro and in vivo. In the plaque reduction assay, the median effective concentration (EC50) of OXT-G, ganciclovir (DHPG) and acyclovir (ACV) against GPCMV was 0.03, 6.4 and 52 micrograms/ml, respectively. The selectivity index, based on the ratio of the median inhibitory concentration for cell growth of guinea pig embryo fibroblasts to the median effective concentration for GPCMV plaque formation, was about 100-fold higher than that of DHPG. In an in vivo study, Hartley guinea pigs infected with GPCMV were treated with OXT-G or DHPG (20 mg/kg/day) for 2 weeks, and it was found that virus titers in the salivary gland were 70-fold lower in OXT-G-treated guinea pigs than in DHPG-treated animals. The results indicate that OXT-G was more potent and selective against GPCMV infection than DHPG.

Acyclovir↗
PubMed1990

[Effect of maternal oxygenation on fetal blood gas status in shiba goat fetuses].

The purpose of this study is to investigate the effect of maternal oxygen administration on the fetal blood gas status. Five Shiba goat fetuses were used whose gestational days were 134 +/- 4 days. Maternal and fetal pH, pO2, pCO2, B.E., and hematocrit were measured every 30 minutes during 4 l/min oxygen administration for 60 minutes. Maternal arterial blood pO2 increased from 95.5 +/- 19.6 mmHg to 262.6 +/- 75.8 mmHg at 30 minutes and to 207.8 +/- 110.1 mmHg at 60 minutes. Fetal arterial blood pO2 increased significantly from 18.4 +/- 3.0 mmHg to 24.4 +/- 5.8 mmHg and 23.6 +/- 6.9 mmHg, respectively. There was a significant positive correlation between maternal pO2 and fetal pO2. The increase in fetal pO2 was small when the control pO2 was less than 17 mmHg. Although maternal pH did not change significantly, fetal pH decreased significantly from 7.29 +/- 0.07 to 7.25 +/- 0.07 at 60 minutes. Also fetal hematocrit decreased significantly from 33.9 +/- 5.2% to 32.8 +/- 5.4% at 60 minutes. Neither maternal nor fetal pCO2 and B.E. changed significantly. Therefore, we concluded that the effect of maternal oxygen administration on fetal pO2 was small when the fetus was already hypoxic. Also 60 minutes' oxygen administration may cause the decrease in fetal pH and hemodilution.

Animals↗
PubMed1990

[An epidemiological study of health behavior and health consciousness in smoking behavior modification].

Among health enhancement activities which have been promoted at various worksites smoking cessation is the most common but is seldom very successful. Smoking cessation programs have almost always neglected individual background factors. The main purpose of this study is to evaluate the factors critical to behavior modification with respect to smoking cessation at worksites. Five hundred and sixty-five chemical factory workers responded to questionnaires on their smoking behavior lifestyle, drinking habits, opinions on smoking, opinions on quitting smoking, knowledge about the effects of smoking on health, and type A behavior pattern. Two hundred thirty two male smokers (age 20-58) were chosen for the smoking cessation program, which was administered during the periodical health examinations. One year after receiving the anti-smoking education their smoking behaviors were again surveyed. Fifteen employees had quit smoking and 79 had reduced consumption by more than 10 cigarettes per day. A principal component analysis was performed in order to extract factors from the numerous items on the questionnaire. Principal component scores were compared between the group that had stopped smoking or had cut back by more than 10 cigarettes per day (Responsive Group) and the rest of the smokers (Unresponsive Group). Principal component scores, which appear to be related to levels of individual health consciousness and levels of regular exercise, were significantly higher in the responsive group than in the unresponsive group. No significant differences were noted between the two groups for principal component scores for knowledge of effects of smoking on health, drinking habits, opinions on smoking, opinions on quitting smoking, and type A behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[A case report of phylloides tumor of the prostate: review of the literature and analysis of bizarre giant cell origin].

A case of phylloides tumor of the prostate in a 58-year-old male is presented. The tumor was composed of columnar cystic folds and pleomorphic stromal elements including bizarre giant cells. Electron microscopic examination, which was performed using specimens embedded in paraffin blocks, revealed that the bizarre giant cells originated from the smooth muscle. The postoperative course was uneventful, with no evidence of local recurrence or metastasis for more than 2 years after operation.

Giant Cells↗
PubMed1990

[Clinical study of male patients with primary biliary cirrhosis (PBC)].

We studied 10 male and 23 female patients with PBC to determine whether the clinical and histological features of this disease differed in male and female patients. There were no significant difference between men and women in age distribution and biochemical examinations. In female patients, autoimmune associated conditions such as sicca syndrome, Raynaud syndrome and arthritis were observed 22%, 13% and 36%, respectively. By contrast, no male patients developed those conditions. 80% of the male patients and 70% of the female patients belonged to asymptomatic PBC, and early histological stage, such as Scheuer's I and II were observed 90% of the male patients and 78% of the female patients, respectively. No male patients showed clinical or histological progression during follow-up period (median was 64 months). Nevertheless, not a few female patients showed progression including 3 cases who died during the follow-up period (median was 47 months). We concluded that male patients with PBC tend to have favorable prognosis comparing to female patients.

Adult↗
PubMed1989

An ATP-driven Cl- pump in the brain.

EDTA-treated microsomes prepared from rat brain mainly consisted of sealed membrane vesicles 200-500 nm in diameter and were rich in both Cl- -ATPase and Na+,K+-ATPase activities. Such Cl- -ATPase-rich membrane vesicles accumulated Cl- in an ATP-dependent and osmotically reactive manner in the presence of 1 nM ouabain. The Cl- uptake was maximally stimulated by ATP with a Km value of 1.5 mM; GTP, ITP, and UTP partially stimulated Cl- uptake, but CTP, beta, gamma-methylene ATP, ADP, and AMP did not. The ATP-dependent Cl- uptake was accelerated by an increase in the medium Cl- concentration with a Km value of 7.4 mM. Such stimulation of Cl- uptake by ATP was dependent on the pH of the medium, with an optimal pH of 7.4, and also on the temperature of the medium, with an optimal range of 37-42 degrees C. Ethacrynic acid dose dependently inhibited the ATP-dependent Cl- uptake with a concentration for half-maximal inhibition at 57 microM. N-ethylmaleimide (0.1 mM) completely inhibited and sodium vanadate (1 mM) partially inhibited the ATP-dependent Cl- uptake. The membrane vesicles did not accumulate H+ in the Cl- uptake assay medium. The ATP-dependent Cl- uptake profile agreed with that of Cl- -ATPase activity reported previously (Inagaki, C., Tanaka, T., Hara, M., and Ishiko, J. (1985) Biochem. Pharmacol. 34, 1705-1712), and this strongly supports the idea that Cl- -ATPase in the brain actively transports Cl-.

Adenosine Triphosphatases↗
PubMed1989

Ischemic flow threshold for extracellular glutamate increase in cat cortex.

Extracellular glutamate (Glu), cerebral blood flow (CBF), and auditory-evoked potentials (AEPs) were measured concurrently using microdialysis and hydrogen clearance in the auditory cortex of anesthetized cats during global ischemia of various severities. A threshold-type relationship was observed between extracellular Glu and CBF: Glu increased at CBF levels below about 20 ml/100 g/min. The Glu increase was related to the impairment of AEPs. The results suggest that Glu neurotoxicity is an important factor for ischemic neuronal injury even in penumbra.

Animals↗
PubMed1989

[Exposure of primary school children and their mothers to nitrogen dioxide in Sapporo City: comparisons of groups clustered by maternal daily behavior and habits].

Exposure of primary school children and their mothers to NO2 was investigated in two schools in the city of Sapporo. One school was located in the city center and another in a suburb of the city. The school children and mothers were requested to put on NO2 filter badges for 24 hours and to record activity during that period. They were also requested to fill out ATS-DLD questionnaires. The surveys were repeated twice, in the summer of 1986 and in the winter 1987, due to possible seasonal variation. Average NO2 exposure levels of both school children and mothers were lower in the summer than the corresponding averages in the winter. The average of the children was lower than that of mothers in both summer and winter. Averages of the children of the city-center school were higher than those of children in the school in the suburb in both summer and winter. These differences were not observed in mothers' averages. To examine the relationship between NO2 exposure levels and maternal daily behavior and habits, the subjects were classified into three clusters by employment status, living area, smoking habits, type of heating appliance, and use of fans during cooking. While average NO2 exposure levels of children were similar among the three clusters, the average of the mothers of the third cluster was the highest among the clusters in either summer or winter. The third cluster was characterized by the highest rate of employment among the clusters, spending less time in their kitchens and not using fans regularly.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1989

[Changes in serum parathyroid hormone levels during pregnancy].

As pregnancy poses a significant challenge to maternal calcium homeostasis, it is interesting to investigate a change in serum parathyroid hormone (PTH) level throughout pregnancy. PTH metabolism in pregnancy has not been clearly defined. We have made an attempt to evaluate changes in serum intact PTH level during pregnancy. Compared with nonpregnant women, serum intact PTH concentrations were decreased significantly in pregnant women during the first and the second trimester, but not during the third trimester. Nephrogenous cyclic AMP excretion, index of parathyroid function has been reported to be decreased in pregnant women during the first and second trimester, but to be in normal range in pregnant women during third trimester. Our finding consisted with these facts.

Adult↗
PubMed1989

[Lutein cyst].

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Female↗