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Biomedical subjects

Y Takagi

Publications and source records attributed to Y Takagi.

At least 649 records · Page 36Linked to original sources
PubMed1982

Nucleotide sequence of Physarum polycephalum 5.8S rRNA gene and its flanking regions.

The nucleotide sequence of Physarum polycephalum 5.8S rRNA gene and its flanking regions has been determined. The homologies of the 5.8S rRNA sequence with those of Saccharomyces, Chlamydomonas and Xenopus were 56%, 50% and 52%, respectively. In spite of these relatively low homologies, its possible secondary structure was very similar to those of other species.

Animals↗
PubMed1982

Transposon Tn3-mediated replicon fusion.

To investigate inter-replicon transposition of Tn3, we used the cosmid-phage lambda packaging system coupled with density gradient fractionation and isolated recombinant molecules of different sizes. Cosmids derived from ampicillin-resistance-transducing phage were classified into four groups: (1) cosmid-Tn3 donor cointegrates considered as Tn3 transposition intermediates, (2) similar cointegrates carrying deletions of one copy of Tn3 and of adjacent cosmid DNA sequences, (3) cosmids carrying a single Tn3 insertion, and (4) cosmids carrying two independent Tn3 insertions. Genetic and biochemical studies indicated that cosmids isolated from ampicillin-resistance transductants were derived from the authentic cosmid-Tn3 donor cointegrate intermediates.

Bacteriophage lambda↗
PubMed1982

Characterization of a ColE1-like plasmid isolated from Shigella sonnei.

A multicopy plasmid, 4.7 kb in size, was isolated from Shigella sonnei and named pKY1. This plasmid produces a colicin E1-like bacteriocin (colicin E1*) in E. coli cells. The cells harboring pKY1 are immune not only to this bacteriocin but also to colicin E1, and the cells harboring Co1E1 show immunity to colicin E1* as well. Although these two plasmid DNAs have different cleavage maps and are compatible with each other, pKY1 shows partial DNA homology with ColE1 DNA. In this paper, we report the isolation and properties of several Tn3 inserted pKY1 mutants, and propose a preliminary genetic map of pKY1. It was also found that this plasmid is not capable of self-transmission and is poorly mobilized by the F factor.

Chromosome Mapping↗
PubMed1982

ColE1 vectors for direct selection of cells carrying a hybrid plasmid.

pKY2289, a ColE1::Tn3 derivative, useful for direct selection of cells carrying a hybrid plasmid, was deleted of its mobility functions and parts of the transposon including the left inverted repeat. This deletion mutant, named pKY2700 expresses low levels of colicin E1 synthesis even in recA cells. A nitrosoguanidine mutant of pKY2289 which shows a high level of constitutive colicin E1 synthesis was also deleted of the same sequences as pKY2700. The second plasmid, named pKY2800, has the same molecular weight (3.8 megadaltons) and almost the same structure as pKY2700, but produces colicin E1 at much higher levels and has a copy number 10 times higher. pKY2800 requires no colicin E1 induction for the direct selection of hybrid clones, while pKY2700 requires mitonmycin C at a concentration of 10 ng per ml. These two colE1 derivatives are useful as safe and convenient vectors for cloning DNA fragments at the cleavage sites of EcoRI, XmaI, and SstII of plasmid.

Bacteriophage lambda↗
PubMed1982

Re-examination of the ColE1 DNA regions essential for autonomous replication and their functions.

Starting from pAO3, a plasmid consisting of a quarter of colicinogenic factor E1 (ColE1) DNA, various small ColE1 derivatives were constructed by in vitro recombination and their ability to achieve autonomous replication was examined. The 436 base pair HaeIII-C fragment of pAO3 contained information for replication when it was recombined with the non-replicating Amp fragment. However, when it was connected to other DNA fragments, the resulting hybrid molecules were not isolated as plasmids. The present results indicate that the additional region of about 240 base pairs next to the HaeIII-C fragment of ColE1 is also essential for the maintenance of a plasmid state. Moreover, using various small ColE1 derivatives, the DNA region responsible for the interference and incompatibility functions of ColE1 DNAs was located. The results indicate that the interference and incompatibility functions are coded by the same ColE1 DNA segment and are not essential for the maintenance of a plasmid state.

Base Composition↗
PubMed1982

Postoperative thallium-201 myocardial images. Evidence of regression of right ventricular hypertrophy in man.

Thallium-201 myocardial scintigraphic studies were performed on 24 patients with chronic right ventricular overload before and after surgical correction of haemodynamic overload. The ages of the patients ranged from 20 to 65 years (mean 39 years) at operation. The degree of right ventricular visualisation remained essentially unchanged in an early postoperative study (four to 60 days), though a decrease in right ventricular cavity size was noted in patients with right ventricular volume overload. On later follow-up (18 to 36 months), thallium uptake in the right ventricle was definitely less than before operation in all 13 patients studied at this time. Because thallium-201 radioactivity reflects myocardial blood flow and mass, our study indicates that right ventricular hypertrophy is largely reversible. Thus, thallium-201 myocardial scintigraphy can be used to assess non-invasively regression of right ventricular hypertrophy in patients with right ventricular overload.

Adult↗
PubMed1982

Noninvasive visualization of the dilated main coronary arteries in coronary artery fistulas by cross-sectional echocardiography.

Real-time cross-sectional echocardiographic studies of the main coronary arteries were performed in 20 normal subjects, 12 patients with patent ductus arteriosus and 14 patients with coronary artery fistula in whom the diagnosis was established by angiography. In 12 patients, the coronary artery that formed the fistula was dilated: The right coronary artery was involved in eight and the left coronary artery in four. The dilated coronary artery appeared as two dominant parallel echoes of wide lumen originating from the aorta in the region of the involved artery. Th echo diameter of the coronary artery correlated well with the angiographically estimated diameter of the artery. In the normal subjects and the patients with patent ductus arteriosus, we found no echocardiographic findings of coronary artery dilatation. This study demonstrates that cross-sectional echocardiography is useful in identifying the dilated coronary artery in coronary artery fistula and distinguishing this entity from patent ductus arteriosus.

Adolescent↗
PubMed1982

Age-associated change in macronuclear DNA content in Paramecium caudatum.

Macronuclear DNA content in Paramecium caudatum was found to be almost unchanged with a mean of about 400C during the earlier two-thirds of the life span in terms of the number of fissions and then it dropped rapidly to about one-fifth of the initial content. The age when rapid DNA decline occurred corresponded to that when the characteristics of senescence appeared. This decreasing pattern of macronuclear DNA content contrasted with earlier observations in P. tetraurelia, P. bursaria and Tetrahymena thermophila. The data suggested that in P. caudatum the distribution pattern of macronuclear DNA to daughter cells changed from an almost equal distribution in younger cells to an unequal distribution in older cells, while the relative volume of the macronucleus to the whole cell remained almost constant throughout the life cycle.

Aging↗
PubMed1982

[Left ventricular myxoma with special reference to diagnostic approach: report of a case].

A 36-year-old male with left ventricular myxoma was presented. The patient had no significant cardiac symptoms except for premature ventricular contractions. The diagnosis was made by two-dimensional echocardiography and cineangiography. The both visualized a tumor of 1.5 cm in diameter which was mobile in the anterior portion of the left ventricle at the level of the chordae tendineae. The accuracy of these techniques was confirmed at the time of operation. In the diagnosis of this lesion, two-dimensional echocardiography was superior to angiography because the stalk connecting the tumor with the anterior left ventricular wall was well visualized. M-mode echocardiography visualized an abnormal echo behind the interventricular septum, but failed to demonstrate the shape, size, mobility and stalk of the tumor. The tumor was not visualized by computerized tomography and RI angiography. The importance of two-dimensional echocardiography was emphasized in the diagnosis of a left ventricular myxoma, even if it is small.

Adult↗
PubMed1982

[Criteria for the diagnosis of prolapsed mitral valve using phonocardiography and echocardiography].

Our criteria for the diagnosis of prolapsed mitral valve were proposed in this paper. With this abnormality, the principal alterations in the mitral valve consist of an abnormal systolic leaflet motion and mitral regurgitation with or without systolic clicks. Our criteria include: (1) auscultatory or phonocardiographic findings suggestive of mitral regurgitation or mitral complex abnormality, (2) a posterior displacement of the mitral valve throughout the latter half of systole by M-mode echocardiography, and (3) a systolic bulging or an apparent systolic ballooning of the mitral valve by two-dimensional echocardiography. A diagnosis of prolapsed mitral valve is justified in a given case if (1) plus one or two other findings are present. Several confusing M-mode and two-dimensional echocardiographic findings for the diagnosis of this condition are neglected in this criteria. We believe that the diagnosis of prolapsed mitral valve, as a rule, should depend on the presence of significant auscultatory or phonocardiographic finding which is a major manifestation of our criteria. However, our criteria seem to be inadequate for the diagnosis of a systolic ballooning of the mitral valve toward the left atrium which is frequently associated with atrial septal defect, since an apical systolic murmur is often absent. The mitral valve ballooning in atrial septal defect, however, is of functional origin, and should be differentiated from an organic prolapsed mitral valve. Thus, to be significant of prolapsed mitral valve, an apical auscultatory or phonocardiographic findings should be unequivocal.

Echocardiography↗
PubMed1981

Experimental and clinical studies on the effect of biliary drainage in obstructive jaundice.

Mitochondrial respiratory function, ketogenesis and collagen metabolism of the liver in biliary obstruction and after its relief were investigated in dogs and patients with obstructive jaundice. In dogs, it was found that hepatic mitochondrial respiratory function decreased significantly with prolongation of biliary obstruction, but recovered to varying degrees depending on both the duration of obstruction and of the period after the relief of obstruction. Ketogenesis was also impaired by biliary obstruction and its recovery was found in a slight degree only in cases with short-term obstruction. Hepatic collagen content and the synthetic ability significantly increased in biliary obstruction, and returned to normal levels with a relatively short period after the relief. Analogous results were obtained in clinical cases, but the decrease in serum bilirubin was somewhat delayed and increased hepatic collagen content continued after relief of the obstruction. When major surgery is required in patients with obstructive jaundice, biliary drainage should be carried out first 4 to 6 weeks before the performance of major operations. In cases with biliary obstruction for 12 weeks or more, it is desirable to wait for more than 6 weeks after biliary drainage since recovery of hepatic function, especially mitochondrial function, will be extremely slow.

Animals↗