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Biomedical subjects

T Oshima

Publications and source records attributed to T Oshima.

At least 325 records · Page 18Linked to original sources
PubMed1994

Overexpression of genes of an extreme thermophile Thermus thermophilus, in Escherichia coli cells.

The 3-isopropylmalate dehydrogenase gene from an extreme thermophile, Thermus thermophilus, was not expressed in Escherichia coli unless a palindromic structure around the ribosome binding site was eliminated or a leader open reading frame was introduced into the upstream flanking region of the gene. This report suggests a way to increase the expression of this gene, with a high G+C content, in E. coli.

3-Isopropylmalate Dehydrogenase↗
PubMed1994

Lack of effect of ouabain on calcium homeostasis in rat platelets: comparative study with human platelets.

The precise mechanisms of Ca2+ handling in rat platelets are not fully understood. We sought to determine whether rat platelets possess a Na(+)-Ca2+ exchanger. First, we investigated the time course of the effect of ouabain (10(-4) M) on cytosolic sodium concentration ([Na+]i) and Ca2+ homeostasis in platelets from Wistar rats in comparison with those from humans. Ouabain increased platelet [Na+]i in both rat and human platelets. Whereas ouabain induced a time-dependent increase in basal and thrombin-stimulated (0.3 units/ml) cytosolic calcium concentration ([Ca2+]i) in human platelets, no change was found in rat platelets. Furthermore, 90-min pretreatment of rat platelets with ouabain did not affect the [Ca2+]i response to thrombin (0.1-1.0 units/ml) or a maximal dose of ionomycin (5 microM). Also the decline in [Ca2+]i after the peak response evoked by these agonists in the absence of extracellular Ca2+ was not changed by ouabain pretreatment. Similarly, replacement of extracellular Na+ had no influence on any of these determinations. Thus decreasing the plasma membrane Na+ gradient did not affect basal [Ca2+]i, thrombin-induced mobilization of Ca2+ from intracellular stores, internal Ca2+ discharge capacity, or Ca2+ extrusion from cytosol of rat platelets. In contrast to human platelets, a Na(+)-Ca2+ exchange mechanism does not appear to play a significant role in Ca2+ homeostasis of rat platelets.

Animals↗
PubMed1994

Lack of increase in platelet Ca2+ and Na+ in deoxycorticosterone acetate-salt hypertensive rats.

We have previously characterized abnormal Ca2+ handling in platelets of spontaneously hypertensive rats (SHRs). In this study, we investigated whether cellular Ca2+ metabolism and/or Na+ concentration is altered in platelets of deoxycorticosterone acetate-salt hypertensive rats (DOCA rats). The resting cytosolic Ca2+ concentration ([Ca2+]i) in platelets was significantly lower in DOCA rats than controls (54.5 +/- 1.4 vs. 61.2 +/- 2.3 nmol/l). The amplitude of the [Ca2+]i transient induced by thrombin was significantly increased in the absence, but not the presence, of external Ca2+ in DOCA rats compared with control rats. The [Ca2+]i response to 5 mumol/l ionomycin in the Ca(2+)-free buffer was greater in DOCA rats than in controls (546 +/- 23 vs. 470 +/- 18 nmol/l), indicating larger intracellular Ca2+ stores. The rate of recovery of [Ca2+]i after the peak response to thrombin was decreased in DOCA rats (79% at 0.1 U/ml and 91% at 1.0 U/ml thrombin of control rats). Cytosolic Na+ concentration ([Na+]i) in platelets was similar in DOCA and control rats. Altered Ca2+ levels are not correlated with [Na+]i in this salt-sensitive hypertensive model. Therefore, an increased [Ca2+]i is not an obligatory phenomenon in hypertension.

Animals↗
PubMed1994

Hiccuplike response elicited by mechanical stimulation of dorsal epipharynx of cats.

To identify the site for triggering hiccup, we recorded activities from the diaphragm (DIA), posterior cricoarytenoid muscle (PCA) of the larynx, and abdominal muscle (ABD) along with intrapleural pressure (Ppl) in anesthetized spontaneously breathing cats. To directly access the epipharynx and to observe glottic movement, we made a submental opening at the level rostral to the epiglottis. Mechanical stimulation of the epipharynx evoked a fixed motor pattern of hiccup: DIA showed spasmodic discharge, and Ppl exhibited spiky negative pressure swing; phasic (inspiratory) discharge of PCA was inhibited, and glottic adduction was revealed by direct observation; and ABD remained suppressed during this response. Chlorpromazine hydrochloride or CO2 inhalation suppressed the response, and the intensity of the response varied according to phase of the respiratory cycle, being largest at midinspiration and least at midexpiration. These are compatible with clinical data on human hiccup. Mechanical stimulation of various parts other than the epipharynx failed to evoke the hiccuplike response. The triggering site was located in the dorsal wall of the epipharynx overlying the occipital bone. These results indicate that mechanical irritation of the dorsal epipharynx is essential for triggering hiccup.

Animals↗
PubMed1994

Effects of age and sex on sodium chloride sensitivity: association with plasma renin activity.

The mechanism by which excessive NaCl intake raises blood pressure has not been fully clarified. The present study was undertaken in 87 Japanese inpatients with essential hypertension to investigate the interrelation among effects of age, sex and the renin-angiotensin system on NaCl sensitivity. After ingesting a regular NaCl diet (170 mmol/day) for one week, subjects were placed sequentially on a week of low NaCl diet (50 mmol/day) and a week of high NaCl diet (340 mmol/day). NaCl sensitivity defined as the difference in mean blood pressure between the low and high NaCl diets did not differ between genders. NaCl sensitivity was positively correlated with age and the change in PRA. The fall in PRA after NaCl loading was significantly smaller in women than in men. By multiple regression analysis, age and the change in PRA independently contributed to the change in mean blood pressure. Furthermore, the interaction between sex and the change in PRA was selected as a statistically significant variable. In conclusion, NaCl sensitivity of blood pressure is independently associated with age and the inadequate suppression of the renin-angiotensin system. Because the contribution of the change in PRA to NaCl sensitivity was greater in women than in men, the mechanism of blood pressure elevation after NaCl loading may differ between genders.

Age Factors↗
PubMed1994

[Multicenter prospective study of retinopathy of prematurity--II. Optimum timing of the first examination].

We reviewed the records of 360 cases of retinopathy of prematurity (ROP) in 12 institutions in Japan, and investigated the optimum timing of the first examination. On the basis of the onset of ROP and the timing of the first treatment, the first ophthalmological examination should be performed 3 weeks after birth or 29 weeks of postconceptional age at the latest. Regarding the visibility of the fundus, there was little hazy media after 29 weeks of postconceptional age. Under the basic policy that the severe progressive "plus" disease should be properly treated, we concluded that the first ophthalmological examination should be performed 3 weeks after birth at the latest. When the gestational age at birth is less than 26 weeks, funduscopy at the post conceptional age of 29 weeks is advisable.

Humans↗
PubMed1994

[Multicenter prospective study of retinopathy of prematurity--III. Timing of the coagulation therapy and the course of retinopathy of prematurity after coagulation].

We reviewed the records of 360 cases of retinopathy of prematurity (ROP) in 12 institutions in Japan, and investigated the timing of the coagulation therapy and the course of ROP after coagulation. The first coagulation therapy was performed at 9.6 weeks after birth and 35.9 weeks of postconceptional age on the average. The severity index in individual infants also showed that the disease became worse during the period from 32 to 36 weeks of postconceptional age. However, the fundus was clearly visible and there was no primary hazy media during this period. On the basis of the results of the timing of the first treatment, the visibility of the fundus, and the severity index in individual infants, we concluded that an ophthalmological examination with special care should be performed during the period from 32 to 36 weeks of postconceptional age.

Humans↗
PubMed1994

[Multicenter prospective study of retinopathy of prematurity--IV. Comparison with the data from University of Miami].

We investigated the records of 360 cases of retinopathy of prematurity (ROP) in 12 institutions in Japan (we treated the severe progressive "plus" disease by coagulation therapy), and compared them with data from University of Miami (Ophthalmology 94: 620-629, 1987), as representative of the natural course of ROP without coagulation therapy in those days. The timing of the first examination and the first positive diagnosis were later at University of Miami than in Japan. The time of maximal severity of the disease and occurrence of regression were also later the University of Miami than in Japan. In Japan, the first examination was performed at 29 weeks of postconceptional age or at 3 weeks after birth. At the University of Miami, the first examination was performed at 32 weeks of postconceptional age. If the severe progressive "plus" disease is to be properly treated by photo-coagulation or cryotherapy, it is essential to commence fundus examination earlier.

Florida↗
PubMed1994

[Clinical study of cyclic intra-arterial chemotherapy using mitoxantrone for advanced hepatocellular carcinoma].

Cyclic intra-arterial infusion chemotherapy using Mitoxantrone via reservoir system was prescribed for 8 patients with advanced hepatocellular carcinoma. According to the clinical staging system, two patients were in Stage III and the other six patients in Stage IV-A. Vp-3 portal invasion was observed in six out of the eight patients. Mitoxantrone (5-8 mg/body) was administered intra-arterially via port-a-cath device every 4 weeks. For tumor response, there were two PR cases, four NC cases, and two PD cases. Thus, the response rate was 25%. The mean survival period was 6.5 months, and 1-year survival rate was 13%. In one of two PR cases, the survival time has been more than two years so far. Gastrointestinal toxicities such as nausea and vomiting were not severe. Critical myelosuppression requiring medication was not observed. Although a temporary increase of serum bilirubin was found in two cases, no severe damage to hepatic function was observed. From our preliminary data, this arterial infusion chemotherapy using Mitoxantrone via reservoir system can be safely performed on non-hospitalized patients with advanced hepatocellular carcinoma, and may be a useful treatment modality.

Aged↗
PubMed1993

[The prediction of blood pressure after adrenalectomy in primary aldosteronism].

In 30-40% of patients with primary aldosteronism owing to adenoma, hypertension is not relieved even though a hyper-functioning adenoma has been completely removed. The purpose of this study is to determine whether the prognosis of hypertension can be evaluated pre-operatively in patients with primary aldosteronism. Thirteen patients (6 men, 7 women; 47 +/- 9 years old) with primary aldosteronism were studied and adrenalectomy was performed in all cases. The success of the operation was confirmed by the normalization of plasma renin activity (PRA), plasma aldosterone concentration (PAC) and serum potassium. Eight patients, 3 men and 5 women, whose blood pressure (BP) was reduced to below 140mmHg systolic and 90mmHg diastolic at one year after the operation were classified as "group N" and the other 5 cases, 3 men and 2 women, remained hypertensive and were classified as "group H". There were no significant differences in the age of the patients, duration of hypertension, pretreatment mean BP and severity of hypertension between the two groups. Thus, it is doubtful that the lack of improvement of hypertension is due to the irreversible damage of the small arteries. Although pretreatment BP was similar in the two groups, systolic BP after the administration of 200mg per day of spironolactone for one week was significantly reduced in group N, but not in group H. Moreover, a significant correlation was found between mean BP after treatment with spironolactone and post-operative mean BP in all subjects. Pretreatment PRA was significantly lower in group H.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1993

Kinetic analysis on the substrate specificity of 3-isopropylmalate dehydrogenase.

Substrate specificity of 3-isopropylmalate dehydrogenase is analyzed using a series of synthetic (2R,3S)-3-alkylmalates. Each analog with hydrogen, methyl, ethyl, isopropyl, isobutyl, tert-butyl, and isoamyl group on C-3 functions as a substrate, implying a broad substrate specificity of the enzyme toward alkylmalates. The incremental binding energy of the isopropyl group of 3-isopropylmalate to the enzyme is estimated to be 3.55 kcal/mol, the rather small value supporting the broad specificity. Although the enzyme shows a broad specificity toward the alkylmalates, it does not show activity with isocitrate which has a negatively charged carboxymethyl group instead of the alkyl groups.

3-Isopropylmalate Dehydrogenase↗
PubMed1993

Tyr-139 in Thermus thermophilus 3-isopropylmalate dehydrogenase is involved in catalytic function.

The role of Tyr-139, which is thought to be located at the active site of Thermus thermophilus HB8 3-isopropylmalate dehydrogenase, has been investigated by site-specific replacement with phenylalanine. The replacement scarcely affected the Michaelis constant (Km) for 3-isopropylmalate, but caused a 13-fold decrease of that for NAD. The catalytic constant (kcat) showed a 14-fold decrease. Accordingly, the catalytic efficiency (kcat/Km) decreased for 3-isopropylmalate but not for NAD. The results suggest that Tyr-139 is involved in the catalytic function through interaction with 3-isopropylmalate.

3-Isopropylmalate Dehydrogenase↗
PubMed1993

Superiority of plasma 11-dehydro-TXB2 to TXB2 as an index of in vivo TX formation in rabbits after dosing of CS-518, a TX synthase inhibitor.

We compared plasma 11-dhTXB2 and TXB2 for their ability to reflect in vivo TX formation in rabbits treated with AA and CS-518, a TX synthase inhibitor. The average plasma level of TXB2 in rabbits was much higher than that of 11-dhTXB2, probably because of artificial formation of TXB2 during blood sampling. CS-518 (1 mg/kg, p.o.) caused a long-lasting suppression of the 11-dhTXB2 level, and its inhibitory effect on 11-dhTXB2 was much more extensive than that on TXB2. AA-infusion for 5 min resulted in transient and remarkable increases of both TXs, and prevention of such increases by CS-518 pretreatment (1 mg/kg, i.v.) was shown: inhibitions of 11-dhTXB2 and TXB2 were 85% and 40%, respectively. The inhibitory effect caused by CS-518, which was more clearly observed on plasma 11-dhTXB2 than on TXB2, was due to not only the completely inhibited levels without artificial formation but also the durable high levels based on the long half-life of 11-dhTXB2 in AA-infused rabbits. CS-518 injection during sustained AA-infusion also resulted in a 2-fold faster disappearance of plasma 11-dhTXB2 than was seen without CS-518, despite its long half-life. Considering the absence of artificial formation, the long half-life, and the good response to change of TX formation, plasma 11-dhTXB2 is superior to TXB2 as an index for monitoring in vivo TX synthase activity and its pharmacological modification with AA and CS-518.

Animals↗
PubMed1993

Planetary quarantine in the solar system. Survival rates of some terrestrial organisms under simulated space conditions by proton irradiation.

We have been studying the survival rates of some species of terrestrial unicellular and multicellular organism (viruses, bacteria, yeasts, fungi, algae, etc.) under simulated interstellar conditions, in connection with planetary quarantine. The interstellar environment in the solar system has been simulated by low temperature, high vacuum (77 K, 4 x 10(-8) torr), and proton irradiation from a Van de Graaff generator. After exposure to a barrage of protons corresponding to about 250 years of irradiation in solar space, tobacco mosaic virus, Bacillus subtilis spores, Staphylococcus aureus, Micrococcus flavus, Aspergillus niger spores, and Clostridium mangenoti spores showed survival rates of 82, 45, 74, 13, 28, and 25%, respectively.

Bacteria↗
PubMed1993

Preliminary report: suspicion of hearing-loss at age 0-1 years by TV viewing attitude.

To determine any difference of TV viewing attitude between normal and hearing-loss children, 14 normal and 8 sensory impaired infants/toddlers were observed separately in a playroom with a TV set showing a 12-min videotape. All children enjoyed TV and showed clear differences in TV viewing behavior between hearing-loss and auditory normal children. At the beginning of their favorite programs or changes in programs, normal infants/toddlers were quickly aware of the TV sound and turned toward the TV set, where as hearing-loss children remained unaware. Our observation proved the intact hearing of two clients who had not responded to regular infant auditory tests. Moreover, we surveyed 65 hearing-loss children. Only 21% of them began to watch TV at 0 year of age, 50% at 1 year. They did it apparently later than normal infants who began to watch TV mostly before 1 year of age in the Japanese general population. From fitting with a hearing aid, however, most of them began to enjoy TV, watch it longer, have their favorite programs (music, songs, etc.) and turn to face the TV whenever a favorite program began. This suggests hearing acuity is important to enjoy TV. Since TV is already familiar and attractive to most any children, it is a useful and sensitive tool for early detection of hearing-loss children at 6-18 months of age.

Child Behavior↗