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Biomedical subjects

S Nagata

Publications and source records attributed to S Nagata.

At least 757 records · Page 42Linked to original sources
PubMed1980

Mitral cleft in ostium primum atrial septal defect assessed by cross-sectional echocardiography.

We attempted to detect mitral deformities in ostium primum atrial septal defect using real-time cross-sectional echocardiography. Transverse sections of the anterior mitral leaflet echo were examined in 11 patients with this malformation who subsequently received surgical treatment. The section for observing the transverse view of te anterior leaflet was along the sagittal plane of the body, because of the deformity of the mitral annulus. Each echocardiographic finding was compared with the surgical and angiographic findings. On the echocardiogram, the superior and inferior parts of the anterior mitral leaflet separated into two parts during diastole in all patients with mitral cleft. Thin linear echoes connected the ridges of the cleft and the ventricular septum in seven patients in whom the accessory chordae at that area were revealed at surgery. The systolic configuration of the anterior leaflet echo varied among the patients. The severity of the miral regurgitation seemed to relate not only to the size of the cleft but also to the systolic configuration of the anterior mitral leaflet. After surgery, diastolic separation of the anterior leaflet echo was no longer observed. However, the abnormal systolic configuration of the anterior leaflet was unchanged.

Adolescent↗
PubMed1980

[Evaluation of estimation method of X-ray spectral distribution by attenuation data (author's transl)].

This paper describes a method for estimating spectral distributions from X-ray attenuation data obtained by inserting metal filters in the beam. First, the principle of the estimation method is briefly outlined. the spectral distribution is approximated by a histogram with an appropriate number of cells whose heights are estimated by recursive algorithm. The algorithm is based on a gradient method that seeks the minimum of a least-square criterion function. Next, the following two problems to which special attention should be paid in practical applications are discussed: 1) appearance of discontinuity in estimated distribution; and 2) termination criterion of iterative computation. The problem 1) is investigated theoretically and the improved algorithm is devised. Computer simulation is performed for the problem 2), and a proper termination criterion based on the decreasing curve of the least-square criterion function is given. The validity of estimation results is illustrated about the spectral distribution of 140 kV constant potential X-ray source.

Computers↗
PubMed1979

Psychosomatic studies of allergic disorders.

It is generally conceded that allergic disorders occur in individuals who have a hereditary or congenital allergic constitution. Clinical symptoms of allergic disorders, however, often disappear due to changes of the individuals' life situations and/or their adaptive patterns. In a comparative study of allergic predisposition in students with allergic disorder (asthmatics) and students who had become completely free from childhood asthma for more than 3 years, without specific treatment, there was no significant difference in allergic predisposition between the two groups. The same tendency was also found between adult patients with allergic disorder (asthmatics) and persons who had shown complete remission for more than 3 years, having had psychosomatic treatment. These findings suggest that allergic predisposition does not influence the prognosis of allergic disorders as much as do socio-psychological factors. It is thought that the effect of psychosomatic treatment reconditions these socio-psychological factors which disturb homeostatic balance and which facilitate the clinical manifestation based on the allergic predisposition.

Adult↗
PubMed1978

Interaction of subunits of polypeptide chain elongation factor I from pig liver. Formation of EF-1alpha.EF-1betagamma and EF-1beta complexes.

In the preceding papers, we showed that one of the two complementar factors of polypeptide chain elongation factor 1 (EF-1) from pig liver, EF-1alpha, functionally corresponds to bacterial EF-Tu (Nagata, S., Iwasaki, K., and Kaziro, Y. (1976) Arch. Biochem. Biophys. 172, 168), while the other, EF-1betagamma, as well as one of its subunits, EF-1beta, corresponds to bacterial EF-Ts (Motoyoshi, K. and Iwasaki, K. (1977) J. Biochem. 82, 703). Therefore, the interaction between EF-1alpha and EF-1 betagamma or EF-1beta was was examined and the following results were obtained. i) EF-1betagamma catalytically promoted the exchange of [14C]GDP bound to EF-1alpha with exogenous [3H]GDP. ii). In the absence of the exogenous guanine nucleotide, EF-1betagamma as well as EF-1beta could displace GDP bound to EF-1alpha to form an EF-1alpha.EF-1betagamma as well as an EF-1alpha.EF-1beta complex. iii) The occurrence of EF-1alpha.EF-1betagamma and EF-1alpha.EF-1beta complexes was demonstrated by gel filtration on Sephadex G-150. These results strongly indicate that the mechanism of the action of EF-1betagamma or EF-1beta in converting EF-1alpha.GDP into EF-1alpha.GTP is analogous to bacterial EF-Ts, and the reaction is accomplished by the following reactions; EF-1alpha.GDP + EF-1betagamma (or EF-1beta) in equilibrium EF-1alpha.EF-1betagamma (or EF-1beta) + GDP; EF-1alpha.EF-1beta (or EF-1beta) + GTP IN EQUILIBRIUM EF-1alpha.GTP + EF-1betagamma (or EF-1beta).

Animals↗
PubMed1977

Electron microscopic study on the early histogenesis of thymus in the toad, Xenopus laevis.

Sequential electron microscopic observations of thymic histogenesis in the toad, Xenopus laevis, reveal that the thymus arises as epithelial buddings of the visceral pouches at Nieuwkoop-Faber stage 40, and acquires its basic histological features at stages 48-49. In the rudiments and the surrounding mesenchyme at stages 43-45, there are non-epithelial cells with pseudopodia, abundant ribosomes, and marginated heterochromatin. These cells, possible precursor cells of thymic lymphocytes, are frequently observed to attach and pass through the basal lamina which coats the thymic rudiment. The proliferation and differentiation of large lymphocytes are evident at stage 47. During stages 48-49 the small lymphocytes, lymphoid cortex and epithelial medulla including the thymic cysts, differentiate, and vascularization occurs. The results provide an ultrastructural basis for recent experimental evidence that the thymus exerts its essential function at stages 47-48. The possibility of non-epithelial derivation of thymic lymphocytes is discussed.

Animals↗
PubMed1977

[Simplification of gamma-ray spectral data by using Fourier transform].

A method is proposed to represent gamma-ray response spectra by Fourier series for the purpose of compressing spectral data. The usefulness of the method was confirmed by applying it to a spectral library of a NaI detector. In the method, a response spectrum as a wave is described by superposition of sine (cosine) waves with low frequencies, whose coefficient parameters can be obtained by a Fast Fourier Transform program. The relation between the number of parameters and the fitting error is discussed, and as the result, it is shown that the number of parameters can be reduced to about a half. The merits and features are presented in practical application of the method to the analysis of gamma-ray spectra.

Fourier Analysis↗