Search PubMed⌕ Search

Biomedical subjects

S Nagata

Publications and source records attributed to S Nagata.

At least 775 records · Page 43Linked to original sources
PubMed1977

[Analysis of gamma-ray spectra by using fast Fourier transform (author's transl)].

In order to simplify the mass data processing in a response matrix method for gamma-ray spectral analysis, a method using a Fast Fourier Transform devised. The validity of the method was confirmed by a computer simulation for spectra of a NaI detector. The method uses the fact that spectral data can be represented by Fourier series with reduced number of terms. The estimation of intensities of gamma-ray components is performed by a matrix operation using the compressed data of an observation spectrum and standard spectra in Fourier coefficients. The identification of gamma-ray energies is also easy. Several features in the method and a general problem to be solved in a response matrix method are described.

Fourier Analysis↗
PubMed1976

Purification and properties of a new polypeptide chain elongation factor, EF-1beta, from pig liver.

Eukaryotic polypeptide elongation factor 1 (EF-1) from pig liver has been resolved into two complementary factors, EF-1alpha and EF-1beta (Iwasaki, K., Mizumoto, K., Tanka, M., and Kaziro, Y. (1973) J. Biochem. (Tokyo) 74, 849). This paper describes the procedures for purification of EF-1beta and some properties of the purified factor. The purification method includes an aqueous two-phase separation technique, a treatment of the crude factor with sodium cholate and two successive column chromatographies on diethyl-aminoethyl-Sephadex A-50. By this method, EF-1beta was purified about 50-fold starting from the material obtained after two-phase separation followed by ammonium sulfate fractionation with a recovery of 20%. The purified EF-1beta appeared homogeneous, having a molecular weight of about 90,000. It consisted of two unequal subunits of the molecular weights of 55,000 and 30,000. It stimulates polymerization of phenylalanine dependent on poly(U) in the presence of both EF-1alpha and EF-2, as well as the EF-1alpha-dependent binding of phenylalanyl-tRNA to ribosomes in the presence of GTP. However, it had no effect on the stoichiometric binding of phenylalanyl-tRNA to ribosomes dependent on EF-1alpha in the presence of guanyl-5'-yl methylenediphosphonate. These results indicate that the function of EF-1beta is to stimulate the recycling of EF-1alpha.

Animals↗
PubMed1976

Restoration of immune responsiveness in early thymectomized xenopus by implantation of histocompatible adult thymus.

Larvae of the South African clawed toad, Xenopus laevis, were thymectomized at Nieuwkoop and Faber stages 45-46 (4-5 days after fertilization). The 1-1.5-year-old thymusless toads thus obtained were implanted with histocompatible thymus from 1-year-old toads, and 4 weeks later were given skin allografts or rabbit red blood cells (RRBC) to determine their immune response. In contrast with the perfectly tolerant thymusless controls, the thymus-implanted toads rejected skin allografts after longer survival times (25-66 days) than the nonthymectomized controls (18 - 19 days). Accelerated rejection (15 - 27 days) of the second-set skin allografts was evident in the thymus-implanted individuals. Similarly, the capacity of antibody production against RRBC was restored to the thymus-implanted toads to roughly the normal extent. Implantation of thymus also restored the histological features of the spleen in thymectomized toads. The experiments clearly demonstrate that in Xenopus the thymus plays an essential role for immunity at the early stages of its histogenesis. The restorative capacity of the adult thymus is also stressed.

Animals↗
PubMed1976

Distribution of the low molecular weight form of eukaryotic elongation factor 1 in various tissues.

Since it was shown that the low molecular weight form of the eukaryotic polypeptide chain elongation factor 1 (EF-1alpha) is highly unstable but could be stabilized by the addition of 25% (v/v) glycerol to all the buffer solutions (Nagata, S., Iwasaki, K., & Kaziro, Y. (1976) Arch. Biochem, Biophys, 172, 168-177), its distribution in several tissues has been investigated under conditions where it is stabilized. The results obtained indicate that EF-1alpha is present as a predominant species in all the tissues examined, such as pig liver, rat liver, rabbit reticulocytes, and Artemia salina cysts. Furthermore, it is suggested that the high molecular weight form of the elongation factor 1 contains a new elongation factor, EF-1beta, in addition to EF-1alpha, while the low molecular weight form contains little EF-1beta.

Animals↗
PubMed1976

Diagnosis of endocardial cushion defect with cross-sectional and M-mode scanning echocardiography. Differentiation from secundum atrial septal defect.

Twelve cases of endocardial cushion defect were studied before and after operation with ultrasono-cardiotomography (tomography) cross-sectional echocardiography, two-dimensional echocardiography, B-scan echocardiography) and M-mode scan along a horizontal section of the heart. For comparison, 20 healthy subjects, 18 cases of mitral valvular disease, 4 cases of congestive cardiomyopathy, 1 case of partial anomalous pulmonary venous drainage, and 25 cases of atrial septal defect of secundum type were also examined with the same technique. In cases without cardiac malformation, the echo of the anterior mitral valve was usually continuous medially with that of the interatrial septum in the horizontal plane at the level of the membranous septum. This feature was clearly recorded in all cases with right heart enlargement. In ostium secundum atrial septal defect the echo of the anterior mitral valve continued into that of the interatrial septum. An echo interruption was shown, indicating the defect itself to be in the middle part of the interatrial septum. In all the cases of endocardial cushion defect which we examined discontinuity was shown between the echo of the anterior mitral valve and that of the interatrial septum. This discontinuity was interpreted as indicating the defect itself. The mitral valve ring echo was close to the basal end of that of the interventricular septum, possibly reflecting an abnormal attachment of the mitral valve. In all cases, after operation, the echo of the artificial interatrial septum was recorded, continuous with that of the anterior mitral valve. The features of the echocardiographic sweep from the anterior mitral valve to the interatrial septum were thus different in the three groups. These echocardiographic differences are thought to correspond to the anatomical differences between the normal, atrial septal defect of secundum type, and endocardial cushion defect, and are essential features differentiating them from each other.

Adolescent↗
PubMed1976

Visualization of Ebstein's anomaly of the tricuspid valve by two-dimensional and standard echocardiography.

Seven patients with Ebstein's anomaly were studied by two-dimensional echocardiography, with and without stop-action technique, and by standard echocardiography. Sagittal two-dimensional echocardiograms visualized a small functional right ventricle and a large atrialized right ventricle. These two parts of the chamber were separated by the anterior tricuspid leaflet and its chordae tendineae. The echocardiograms corresponded to the findings of the right ventriculogram. In horizontal two-dimensional echocardiograms a huge anterior tricuspid leaflet, atrialized right ventricle, and a displaced septal tricuspid leaflet, intervening between the functional right ventricle and the sinus portion of the functional right ventricle, were visualized. The origin of the septal tricuspid leaflet was clearly shown to be abnormal in five cases. The left ventricle was small with distinct clockwise rotation of the interventricular septum. Two-dimensional echocardiography provided information useful in evaluation of the functions of the right ventricle and the tricuspid valve and determination of what surgical procedure to follow.

Ebstein Anomaly↗
PubMed1975

Interatrial septum in B-mode and conventional echocardiograms - a clue for the diagnosis of congenital heart diseases.

The interatrial septum was studied with B-mode echocardiography to determine whether there were specific ultrasonic features characteristic of such congenital heart diseases as atrial septal defect and endocardial cushion defect. In transverse tomograms in the third and fourth intercostal space the interatrial septum is detected almost parallel to the anterior chest wall. The septum continues leftward to the echo of the anterior mitral leaflet. When the interatrial septum extends beyond the left sternal border, it can also be recorded near the left sternal border in the sagittal tomogram. The interatrial septum can also be recorded by conventional echocardiography. The pattern is wavy and synchronous with the heart beat with an amplitude of about 10 mm. It is seen near the chest wall in patients with left atrial enlargement and far from the chest wall in patients with right atrial enlargement. The defect in the interatrial septum was visualized by B-mode and conventional echocardiogram in patients with ostium secundum atrial septal defect. The defects were no longer observed after surgery.

Adolescent↗
PubMed1975

An unusual pattern of the mitral echocardiogram observed in cases of congestive cardiomyopathy and other myocardial diseases.

(1) Narrowness of the early-diastolic and presystolic peaks on the echo curve of the anterior mitral leaflet and an abnormal step formation at the middle or higher level on the descending limb of the presystolic peak were observed in 7 cases with congestive cardiomyopathy or myocardial fibrosis, 1 case with myocardial infarction, and 1 case with cardiomyopathy due to progressive muscular dystrophy. (2) This abnormal pattern is considered to be closely related to the myocardial condition in the above-mentioned diseases. (3) Probable mechanisms for this pattern formation are considered as follows: (i) a sudden reduction of distensibility of the left ventricle after filling of the ventricle over a certain limit near full-filling, and impaired ventricular contractility, (ii) restriction in the mobility of the mitral valve and its chardae due to thier inability to adapt themselves to a developed dilatation of the left ventricle. (4) A similar presystolic step formation on the echo curve of the anterior mitral leaflet was observed in 3 of 25 cases of hypertrophic cardiomyopathy of Goodwin's sense. Differences between the myocardial state in congestive cardiomyopathy or in similar myocardial diseases and that in hypertrophic cardiomyopathy were also discussed.

Adolescent↗
PubMed1968

Studies on the posterior silk gland of the silkworm, Bombyx mori. I. Growth of posterior silk gland cells and biosynthesis of fibroin during the fifth larval instar.

Growth of the posterior silk gland and biosynthesis of fibroin during the fifth larval instar of the silkworm, Bombyx mori, have been studied. In accordance with the exponential increase in the wet weight of the gland, the amounts of DNA, RNA, protein, and lipids per animal increased rapidly in the early stage of the fifth instar (0-96 hr). Biosynthesis of fibroin, on the contrary, mainly proceeds in the later stage of the fifth instar (120-192 hr). Electron microscopical observations have shown that, in the very early stage (0-12 hr), a number of free ribosomes exist in the cytoplasm. Rough endoplasmic reticulum (ER) with closely spaced cisternae was also observed. Then rough ER starts to proliferate rapidly, and at the same time lamellar ER is rapidly or gradually transformed into vesicular or tubular forms. In the later stage of the fifth instar (120-192 hr), the cytoplasm is mostly filled with tubular or vesicular ER. Golgi vacuoles, free vacuoles (fibroin globules), and mitochondria are also observed. It is concluded that in the early stage of the fifth instar the cellular structures necessary for the biosynthesis of fibroin are rapidly formed, while in the later stage the biosynthesis of fibroin proceeds at a maximum rate and utilizes these structures.

Animals↗