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Biomedical subjects

I Nagata

Publications and source records attributed to I Nagata.

At least 325 records · Page 18Linked to original sources
PubMed1981

[Effect of oxytocin administration on prostaglandin concentrations in uterine and placental tissues of pregnant rabbit (author's transl)].

To clarify the mechanism of labor onset, the effect of exogenous oxytocin (OT) on tissue prostaglandin (PG) formation was studied in vivo. Changes of PG concentrations of the uterine venous plasma, myometrium, fetal and maternal cotyledons of placenta, and parietal decidua of late pregnant rabbits were evaluated between just before and 10 minutes after administration of 10 IU of OT. PGE1, PGE2, and PGF2 alpha were extracted from each tissue by Inagawa's method and measured by radioimmunoassay. Concentrations of PGE1 (344-1,280 ng/g wet weight) and PGE2 (656-3,000 ng/g wet weight) of the fetal cotyledon were 2-30 times higher than those of other tissues regardless of OT administration. Differences in PG concentrations between before and after OT administration were compared. The results were: 1) Changes of PGs in the plasma, fetal cotyledon, and parietal decidua showed no definite tendency after OT administration. 2) In the myometrium, all measured PG decreased after OT administration, suggesting that tissue PGs are not concerned with myometrial contraction when induced by exogenous OT. 3) In the maternal cotyledon of the placenta, PGs increased after OT administration, suggesting that the maternal cotyledon is the only site having close relationship between OT administration and PGs formation in vivo.

Animals↗
PubMed1981

[Alterations of oxytocin and prostaglandin E1, E2, F2 alpha levels in human plasma during labor (author's transl)].

In order to investigate the role of oxytocin (OT) and prostaglandins (PGs) in the mechanism of labor onset, changes of OT and PGs levels in human plasma were evaluated before labor, soon after the labor onset, and at the time of established labor in the following three groups. Group 1 consisted of 6 cases with spontaneous labor, group 2, of 6 cases with induced labor with PGF2 alpha drip infusion, and group 3, of 5 cases with induced with PGE2 vaginal suppository. OT concentrations were measured by RIA, PGE1, PGE2, and PGF2 alpha were extracted and determined by Inagawa's method. Levels of OT in group 1 were divided into two subgroups: subgroup 1 with high OT levels (24.0-116.2 microunits/ml) and subgroup 2 with low OT levels (below 7.2 microunits/ml) throughout labor. Changes of PGs level in subgroup 1 showed no definite tendency during labor, suggesting that OT appears to play the leading role in spontaneous labor. Those in subgroup 2 showed a particular behavioral pattern during labor, suggesting an important role played by PGs for the onset of labor following rupture of the membranes. The results of groups 2 and 3 are fully discussed in terms of labor process.

Female↗
PubMed1980

Experimentally induced cerebral aneurysms in rats: Part VI. Hypertension.

Cerebral aneurysms were induced in rats treated with unilateral ligation of the common carotid artery and hypertension produced by renal infarction with or without beta-aminopropionitrile, one of the lathyrogens. In this experiment, cerebral aneurysms developed more frequently than in the previous experiments in which hypertension induced by deoxycorticosterone and salt had been used. It was demonstrated that deoxycorticosterone was not essential to the development of the lesion. Regardless of its type, hypertension combined with carotid ligation played a primary role in the production of cerebral aneurysms in rats. Sodium chloride enhanced the systolic hypertension and thus increased the incidence of lesions. The role of hypertension in the development of cerebral aneurysms in humans is discussed.

Aminopropionitrile↗
PubMed1980

Experimentally induced cerebral aneurysms in rats: Part V. Relation of hemodynamics in the circle of Willis to formation of aneurysms.

All the rats were made hypertensive and fed beta-aminopropionitrile. Among them, cerebral aneurysms were never found in rats without carotid ligation. In rats with ligation of one or both common carotid arteries, cerebral aneurysms developed on the vessels where hemodynamic stresses were apparently increased. The relationship of hemodynamics in the circle of Willis to the development of cerebral aneurysms is discussed, being compared with findings in spontaneous lesions in man.

Aminopropionitrile↗
PubMed1980

Ultrasonic Doppler assessment of hemodynamics in superficial temporal artery--middle cerebral artery anastomosis.

The pre-, intra-, and postoperative hemodynamics were examined by a newly developed ultrasonic Doppler flowmeter in 20 patients undergoing 24 STA-MCA anastomoses. During the operations, no reverse flow was detected in the cortical branch of the middle cerebral artery. After anastomosis, prominent flow changes in direction and in volume were evident in the cortical branches and the flow pattern of the STA changed from an external carotid type preoperatively to an internal carotid type in well functioning bypasses. The results of postoperative studies were not always in good agreement with those of intraoperative studies and bypass function was relatively not good and labile in patients with only stenotic lesions and in those with "moyamoya disease".

Adolescent↗
PubMed1979

Interferon susceptibility of various cell lines persistently infected with haemagglutinating virus of Japan (HVJ).

Various cell lines persistently infected with para-influenza 1 virus, HVJ strain, were less susceptible to the antiviral action of interferon than the same cell lines when not infected with HVJ. When Vero cells persistently infected with a temperature-sensitive strain of HVJ were incubated at 38 degrees C, a non-permissive temperature, they became fully susceptible to interferon, whereas neither the haemadsorbing nor the cell-associated haemagglutinating activity of the virus was expressed. These findings suggest that the lowered interferon susceptibility of virus-carrier cells may be related to the maturation of virus in them. It was found that the low susceptibility of virus-carrier cells to interferon is not due to blocked adsorption of interferon or to inability of the cells to respond tointerferon. Studies with actinomycin D suggest that some step (or steps) before the synthesis of the messenger RNA for the antiviral protein is blocked.

Animals↗
PubMed1979

Examination of latent infection in germfree mice for some murine viruses.

Sera from some groups of germfree mice were examined for reactivity against Sendai, reo 3, Theiler's GD VII, ectromelia, and mouse hepatitis virus antigens. Of 51 sera collected in September and October 1976 and in August and September 1977 from one germfree mouse breeding colony, there was no positive reaction against all the antigens tested. Moreover, the attempt of virus isolation from homogenates of various organs including lungs, liver, kidneys, and intestines of 6 germfree mice was unsuccessful.

Animals↗
PubMed1978

Phosphodiesterase and its Ca2+-dependent activating factor in bovine thyroid.

Properties of cyclic 3',5'-nucleotide phosphodiesterase in the 100,500 X g supernatant of the bovine thyroid were investigated. The enzyme activity was measured by a radioisotopic method using an anionic-exchange resin, and it was found that the activity was stimulated by Mg2+. Sephadex G-200 gel filtration separated the supernatant into an activating factor, which required the presence of Ca2+, and an enzyme form dependent on the factor. The molecular weights were estimated to be 25,000 and 130,000, respectively. There appeared to be another enzyme form of cAMP phosphodiesterase with different dependence on the activating factor as suggested by gel filtration, but this enzyme form could not be clearly separated. cGMP phosphodiesterase purified by gel filtration showed biphasic kinetic behavior in the absence of Ca2+ and the activating factor, whereas, in their presence, the Lineweaver-Burk plot gave a single Km. The activating mechanism of phosphodiesterase may play a role in the control of concentrations of intracellular cyclic 3',5'-nucleotides in the bovine thyroid.

3',5'-Cyclic-AMP Phosphodiesterases↗