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M Okamoto

Publications and source records attributed to M Okamoto.

At least 901 records · Page 50Linked to original sources
PubMed1987

[Noninvasive measurement of cardiac output using two-dimensional Doppler echocardiography and analysis of sources of error].

The purpose of this study was (1) to analyze the factors responsible for errors in the two-dimensional Doppler echographic measurements of cardiac output (C.O.) and (2) to establish a noninvasive method for measuring C.O. The subjects were 50 cardiac patients who had neither aortic valve disease nor intracardiac shunts. The C.O. was calculated using the following formula: C.O. (l/min) = mean flow velocity (cm/sec) x pi(aortic ring diameter/2)2 (cm2) x 60/10(3) Left ventricular ejection flow velocity was recorded in the center of the aortic ring from the apical approach. Mean velocity was calculated by integration of instantaneous mean velocity in the ejection phase divided by the cardiac cycle length, and was corrected by the Doppler incident angle. The inner diameter of the aortic ring was measured in the parasternal long-axis view at the time of the maximum ejection flow velocity. The following results were obtained: 1. Sources of error in the measurement of cardiac output. 1) Accuracy of instantaneous mean velocity calculating circuit: This calculating circuit was accurate in model experiments using pulsatile flow. 2) Effect of high-pass filter: In model circuits, application of high-pass filter overestimated flow velocity. The higher the cut-off frequency of the high-pass filter, the larger the overestimation. This was probably due to the parabolic flow velocity profile in the circuit. 3) Flow velocity profile in the aortic ring: The flow velocity profile seemed to be flat in the aortic ring except near the anterior aortic wall. Therefore, the effect of the high-pass filter was considered to be negligible in case of clinical application. 4) The effects of shift and size of sample volume: The location of sample volume relative to the aortic valve ring shifted about 7 mm during systole. However, the shift and size of sample volume seemed to have little effect on the measured C.O., because the flow velocity profile was nearly flat in the aortic ring. 5) Ultrasound beam incident angle: From a practical viewpoint, it was necessary to set an incident angle of less than 50 degrees for minimizing the error. We were able to set the angle within 50 degrees in all but one of patients. 6) Diameter of the aortic ring: Two-dimensional echographic measurement of the aortic ring diameter was not so accurate; it seemed to become a major source of error in the calculation of C.O.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

T-cell independent transfer of organized granuloma formation.

A direct role for delayed hypersensitivity in organized granuloma formation has been emphasized in the literature, but some clinical and experimental studies have suggested a more complicated relationship. In order to further evaluate T-cell function in cutaneous granulomatous inflammation, hepatic granulomas isolated from athymic mice with schistosomiasis were grafted into the skin of athymic and euthymic mice. Granulomas developed in athymic mice, as seen previously after transplantation of euthymic hepatic granulomas, indicating that granulomas develop in the skin without T-cell function. However, the granulomas in athymic mice skin were smaller and lacked eosinophils and mast cells, whereas the athymic mouse granulomas grafted in euthymic mice skin were larger, better organized, and associated with tissue eosinophilia. These findings suggest that granuloma initiation itself is T-cell independent, but that T-cell participation enhances the granulomatous reaction.

Animals↗
PubMed1986

Platelet activating factor (PAF) involvement in endotoxin-induced thrombocytopenia in rabbits: studies with FR-900452, a specific inhibitor of PAF.

PAF (1 ug/kg) injected intravenously (i.v.) into anesthetized rabbits resulted in marked loss of circulating platelets and leukocytes. Administration of FR-900452 1-methyl-3-(1-(5-methylthiomethyl-6-oxo-3-(2-oxo-3-cyclopenten-1-y lidene)- 2-piperazinyl) ethyl)-2-indolinone, a specific PAF inhibitor, at a dose of 10 mg/kg i.v. with 10 min prior to the PAF injection significantly prevented both changes. On the other hand, PAF has been considered as a mediator of endotoxin shock. Therefore, in order to determine whether endogenous PAF contributes to the occurrence of thrombocytopenia or leukopenia in endotoxin shock, we assessed the effect of FR-900452 on the thrombocytopenia and the leukopenia following bolus i.v. injection of E.coli endotoxin (0.03 mg/kg) in rabbits. As a result, pretreatment with the compound (10 mg/kg, i.v.) significantly reduced the thrombocytopenia at 60 and 180 min after the endotoxin injection. In contrast, FR-900452 did not reduced the leukopenia at any time of after endotoxin. These results indicate that PAF might be involved in the occurrence of thrombocytopenia in rabbit endotoxemia and the contribution of PAF to the leukopenia is much less extent than that to the thrombocytopenia.

Animals↗
PubMed1986

Integrated function of a kinetic proofreading mechanism: double-stage proofreading by isoleucyl-tRNA synthetase.

Experimental measurements for isoleucyl-tRNA synthetase proofreading valyl-tRNAIle in Escherichia coli previously have been incorporated into the conventional Michaelis-Menten model for this system. This model was augmented to include two stages of proofreading--the aminoacyl adenylate and aminoacyl-tRNA stages--and used to predict the values of four additional rate constants that have been determined experimentally. The results suggest that two stages of conventional kinetic proofreading with binding sites designed for isoleucine (the "correct" substrate) are inconsistent with the experimental data, that a double-stage mechanism in which one stage (the "double-sieve") involves a binding site designed for valine (the "incorrect" substrate) and the other involves a binding site designed for isoleucine is consistent with all the experimental data, and that the experimental data are not sufficiently accurate to distinguish the stage at which the double-sieve mechanism operates in vivo. Furthermore, analysis of the model suggests that four parameters have the most questionable values and that experimental refinement of their estimates will be needed to determine which of the two stages involves the double-sieve mechanism.

Amino Acyl-tRNA Synthetases↗
PubMed1986

Characterization of elastase associated with granulomatous tissue remodeling.

Elastases have been reported to be involved in various types of tissue injury. In this study we detected hydrolytic activities for [3H]-elastin and Suc-Ala-Ala-Ala-pNA (SLAPN) in hepatic granulomas which became elevated in parallel with enlargement of the granulomas and disappearance of aldehyde-fuchsin-stained filaments in the lesions of mice infected with Schistosoma mansoni. The elastase was partially purified by gel filtration followed by anion-exchange chromatography. This enzyme has a molecular weight of 20-25k and hydrolyzed denatured collagen (azocoll), Glu-Pro-Val-pNA, SLAPN, and [3H]-elastin. Optimal pH was 7-8.5. It is a serine proteinase and distinct in its inhibitor profile from murine peritoneal macrophage elastase, which has been reported by others. Digestion of elastic fibers in vessel walls and fine fibrils in newly developed granulomas by the granuloma elastase was histochemically identified with aldehyde-fuchsin stain. These results indicate that a serine proteinase functions as a major elastase in granulomatous tissue remodeling and may account for the disappearance of elastic fibers and other elements of the matrix in fully developed granulomas.

Aldehydes↗
PubMed1986

Developmental anomalies induced by all-trans retinoic acid in fetal mice: I. Macroscopic findings.

The administration of a single dose of all-trans retinoic acid on day 8 of gestation to pregnant mice, ICR strain, led to malformed fetuses in all of the litters. All-trans retinoic acid (RA) was dissolved in olive oil and given in doses of 60 or 40 mg/kg of body weight. The control mice were given vehicle alone. Examination on day 18 of gestation of the fetuses exposed to 60 mg/kg showed various malformations, such as exencephaly, exophthalmus, micrognathia, agnathia, cleft palate, cleft lower lip, spina bifida, atresia ani, tail anomalies, agenesis of the kidneys, or hydronephrosis. In the fetuses exposed to 40 mg/kg, isolated cleft palate was much more common than in those exposed to 60 mg/kg. Double-stained preparations of bone and cartilage showed cranio-facial anomalies and axial skeletal anomalies: a- or hypogenesis of palatine or maxillary bones, tympanic ring, squamosal temporal bone or otic ossicles in cartilage, and fusion of basioccipital to basisphenoid and maxilla, zygomatic and mandibular bones; a- or hypogenesis of caudal vertebrae and supernumerary thoracic and lumbar vertebrae. These results indicate that anomalies comparable to those seen in the infants of mothers treated with isotretinoin, 13-cis retinoic acid, during pregnancy can also be induced in mice and suggest that the site affected by RA may be neural crest cells, including those in the cephalic and caudal regions, and cells committed to somitic mesoderm in the trunk region.

Abnormalities, Drug-Induced↗
PubMed1986

Ultrastructural and immunohistochemical studies on steroid-secreting cells of testis and ovary of normal and 3-methylcholanthrene-treated mice.

The testis and ovary of normal and 3-methylcholanthrene-treated mice were studied ultrastructurally and immunohistochemically in order to learn whether steroid-secreting cells of the gonads are involved in drug metabolism. The steroid-secreting cells, i.e., Leydig cells of the testis, and theca interna cells, interstitial gland cells, and corpus luteum cells of the ovary of 3-methylcholanthrene-treated mice show a strong positive reaction to the antiserum against, hepatic microsomal cytochrome P-450, of liver which is the terminal oxidase of the drug-metabolizing enzyme complex. In addition, it was found that elements of smooth endoplasmic reticulum (SER) in drug-treated mice become well developed as compared with those in control animals. These findings indicate that the steroid secreting cells in testis as well as ovary are involved in the metabolism of both endogenous and exogenous chemical compounds.

Animals↗
PubMed1986

3-Methylcholanthrene-induced ethoxyresorufin O-deethylase activity in alveolar type II cells of rabbit lung.

Lungs of 3-methylcholanthrene-treated rabbits and those of untreated rabbits were digested with protease, and the cells were separated into an alveolar type II cell-rich fraction and a Clara cell-rich fraction by the use of counter-flow centrifugal elutriation. Drug oxidation activities of the cell homogenate of each fraction were examined. Marked elevation of ethoxyresorufin O-deethylase activity was found mainly in the cell homogenate of the alveolar type II cell-rich fraction after 3-methylcholanthrene treatment. The activity increased 6-fold with the drug treatment. Coumarin hydroxylase activity was found mainly in the cell homogenates of the Clara cell-rich fraction of the 3-methylcholanthrene-treated and untreated rabbits. The activity increased 3.5-fold with the drug treatment.

Animals↗