Biomedical subjects

K Nagata

Publications and source records attributed to K Nagata.

At least 1,009 records · Page 56Linked to original sources

PubMed1982

Topographic electroencephalographic study of cerebral infarction using computed mapping of the EEG.

Computed mapping of the electroencephalogram (CME) is a newly developed method using a microcomputer system that displays the scalp topograph as the square roots of the average power spectra over each EEG frequency band on a color television screen. This new device has been employed in an examination of functional lesions in 20 patients with aphasia due to cerebral infarction. The results were compared with those of computer tomography (CT) and regional cerebral blood flow (rCBF) studies using intracarotid 133Xe. A high-voltage focus of slow components and an asymmetrical distribution of alpha activity were regarded as signs of functional lesions on CME. Twelve patients showed high-voltage foci and six showed asymmetrical alpha activity on CME, which correlated well with the lesions on CT and/or rCBF studies. Especially in patients with motor aphasia, CME demonstrated the abnormality in advance of the appearance of a low-density area on CT. Compared with conventional EEG interpretation, CME is very useful in topographic and objective diagnosis of functional lesions, although the source of the data is the same as for the conventional EEG.

Alpha Rhythm↗

PubMed1982

Adenovirus DNA replication in vitro: identification of a host factor that stimulates synthesis of the preterminal protein-dCMP complex.

A protein factor that participates in the formation of a covalent complex between the 80,000-dalton precursor of the adenovirus (Ad) terminal protein (pTP) and 5'-dCMP has been isolated and characterized. This 47,000-dalton protein, isolated from nuclear extracts of uninfected HeLa cells, has been designated nuclear factor I. It is free of detectable DNA polymerase alpha, beta, and gamma activities. In the presence of Ad DNA-prot, the Ad-protein fraction (containing the pTP and the Ad-associated DNA polymerase), ATP, Mg2+, and dCTP, nuclear factor I stimulates formation of the pTP-dCMP complex. Addition of the Ad DNA binding protein (Ad DBP) renders the formation of the pTP-dCMP complex completely dependent on the addition of nuclear factor I. When Ad DNA-prot is replaced with phi X174 single-stranded circular DNA, pTP-dCMP complex formation requires only the Ad-protein fraction; Ad DBP and ATP are inhibitory and nuclear factor I has no effect on this reaction. This suggests that the initiation reaction observed with Ad DNA-prot in the absence of Ad DBP occurs at single-stranded DNA sites. In the presence of Ad DBP, these sites are blocked thus creating a requirement for nuclear factor I in pTP-dCMP complex formation.

Adenoviruses, Human↗

PubMed1982

Changes in contractile proteins during differentiation of myeloid leukemia cells. II. Purification and characterization of actin.

A myeloid leukemia cell line, M1, differentiates to macrophage and gains locomotive and phagocytic activity when incubated with conditioned medium (CM) from a fibroblast culture and bacterial endotoxin. To characterize the actin molecules before and after differentiation, the actin was purified through three sequential steps: DEAE-sephadex A- 50, polymerization/depolymerization, and sephadex G-150 chromatography. There were no essential differences between the inhibitory activity of actins from control M1 cells and CM-treated M1 cells on both DNase I and heavy meromyosin (HMMM) K(+)-EDTA-ATPase; the same dose response as with skeletal muscle actin took place. After the treatment with CM, however, the specific activity for the activation of HMMM Mg(2+)- ATPase by actin became two-fold that of untreated M1 actin, which was one third of the value for skeletal muscle actin. The V(max) for the control and the CM-treated M1 cell, as well as the skeletal muscle actins, proved to be the same. By contrast, the K(app) values for the control and CM-treated M1-cell actins were 3- and 1.5-fold the value for skeletal-muscle actin. This means that CM treatment of the M1 actin produced a twofold affinity for the Mg(2+)-ATPase of skeletal-muscle myosin. The critical concentrations for polymerization were compared under different salt concentrations and temperatures. Although no marked difference was found for the presence of 2 mM MgCl(2), 0.1 M KCl in place of MgCl(2) at 5 degrees C gave the following values: 0.1 mg/ml for skeletal-muscle actin, 0.7 mg/ml for control M1 actin, 0,5 mg/ml for CM- treated M1 actin, and 1.0 mg/ml for the D(-) subline that is insensitive to CM. Although the critical concentration of D(-) actin is extraordinarily high, this actin showed normal polymerization above the critical concentration. This together with the data presented in our previous paper, that the D(-) actin in the crude extract did not polymerize, suggests that an inhibitor for actin polymerization is present in the subline. The kinetics experiment at 0.1 M KCl and 25 degrees C revealed a slower polymerization of untreated M1- and D(-)-cell actins as compared with CM-treated M1 actin. This delayed polymerization was due to a delay during the nucleation stage, not during the elongation stage. By isoelectric focusing, the ratios of beta- to gamma-actin showed a marked difference depending on the states of cells: about 4.9 for control M1, 2.8 for CM-treated M1, and 7.6 for D(-)-subline actins. Tryptic peptide maps also revealed the presence of different peptides. Thus, the functional differences of actin before and after the differentiation was accompanied by some chemical changes in actin molecules.

Actins↗

PubMed1982

Changes in myosin during differentiation of myeloid leukemia cells.

Changes in cellular myosin were followed during the differentiation into macrophages of a myeloid leukemia cell line (Ml) which can be induced by conditioned medium (CM) from a rat embryo culture. To extract the myosin, we used three different procedures, all of which gave a lower yield of myosin for the differentiated than for the undifferentiated Ml cells. This low extractability we attributed to increased binding of the myosin to the plasma membrane. Taking the different extractabilities into consideration, we calculated the myosin contents in the total cellular protein from the densitometry of SDS-polyacrylamide electrophoresis, 0.6% for the untreated Ml cells and 1.0% for the differentiated ones. The three ATPase activities of the Ml cell myosin were in the order, K+-EDTA-=Ca2+- much greater than Mg2+-ATPase in the presence of 0.6 M KCl, whether or not there was treatment with CM. Myosin was purified through fractionation with 25-55% saturated ammonium sulfate, then gel filtration with Sepharose 4B followed by affinity chromatography on F actin-Sepharose 4B. The Ml cell myosin consists of 1 heavy chain (H) and 3 light chains (L1, L2, L3), with molecular ratios of L1 + L2/H not equal to and L3/H not equal to 1. The ratio of L1/L2 was about 1.2 for the untreated Ml cells, but it decreased to about 0.7 after differentiation.

Adenosine Triphosphatases↗

PubMed1982

Effect of pyridoxine-deficiency on the syntheses of aspartate aminotransferase in rat liver and muscle in vivo.

The rates of synthesis of aspartate aminotransferase isozymes in the liver and skeletal muscle in pyridoxine-deficient rats were examined. The rates of synthesis were compared in rats given pyridoxine-deficient diet ad libitum, rats given control diet ad libitum and rats pair-fed with those on the deficient diet. The rates of incorporation of 3H-L-leucine by both cytosolic and mitochondrial enzymes were highest in pair-fed controls. Incorporation of radioactivity into the cytosolic enzyme was higher in deficient rat liver than in that of controls fed ad libitum, but the rate of incorporation into the mitochondrial enzyme was similar in these two groups. In muscle the rates of incorporation of labeled leucine into both isozymes were similar in all groups when expressed relative to total protein synthesis. It was suggested that increase of glucocorticoid receptor might result in increased synthesis of cytosolic aspartate aminotransferase in pyridoxine-deficient rat liver.

Animals↗

PubMed1982

Effect of pyridoxine deficiency on activities and amounts of aspartate aminotransferase isozymes in rat tissues.

The enzyme and antigen activities of aspartate aminotransferase [EC 2.6.1.1] isozymes in several tissues of rats fed on pyridoxine-deficient or control diet for 4 weeks were determined. The enzyme activities in liver (supernate, mitochondria), heart (supernate), brain (mitochondria), and muscle (mitochondria) preparations of the deficient rats were abnormally low, whereas those in other tissue preparations were similar to those of control rats. In liver and heart preparations, the antigen activities of the deficient rats were similar to those in controls, but in brain and muscle mitochondria they were abnormally low. These findings suggest that the activity and the amount of this enzyme are regulated in different ways in different tissues, and suggest that the coenzyme level affects metabolic regulation of the enzyme molecule.

Animals↗

PubMed1982

A cofactor protein required for actin activation of myosin Mg2+ATPase activity in leukemic myeloblasts.

The Mg2+ATPase activity of the myosin of a myeloid leukemia cell line (Ml) was not activated by purified Ml actin or by muscle actin alone. Activation required the presence of a cellular fraction as a cofactor in addition to the actin, when Mg2+ATPase was stimulated as much as 20-fold. The cofactor was partially purified and characterized. 1) Its molecular weight was estimated as 45,000 to 55,000 daltons by gel filtration and as 45,000 daltons by SDS polyacrylamide gel electrophoresis. 2) The cofactor was a light chain kinase that phosphorylated both the L1 and L2 light chains of the Ml cell myosin, but not the L3 or heavy chain.

Actins↗

PubMed1982

Rhabdomyosarcoma of the right ventricle.

A case of a 66-year-old male with rhabdomyosarcoma of the right ventricle who presented first with a pleuritic chest pain and later developed congestive heart failure with A-V block is described. The total period of the disease was about 9 months. At autopsy the right ventricle and wall were found to be replaced by tumor tissue which was diagnosed histologically as rhabdomyosarcoma of the alveolar type. We described one case and 52 rhabdomyosarcomas of the heart from the literature; the ages ranged from 3 months to 92 years with 29 men and 23 women (unknown 1). The primary lesions were right ventricle 29%, right atrium 26%, left atrium 24%, left ventricle 6%, and others 15%.

Aged↗

PubMed1982

A unique change of steroid metabolism in rat liver microsomes induced with highly toxic polychlorinated biphenyl(PCB) and polychlorinated dibenzofuran(PCDF).

Pretreatments of rats with the highly toxic compounds such as 3,4,5,3',4'-pentachlorobiphenyl(PenCB), and 2,3,7,8-tetrachloro(TCDF) and 2,3,4,7,8-pentachlorodibenzofuran(PenCDF), which are potent 3-methylcholanthrene(MC)-type inducers, increased selectively 7 alpha-hydroxylation, but strongly suppressed 2 alpha-, 6 beta- and 16 alpha-hydroxylations as well as 5 alpha-reduction of progesterone and testosterone in the liver microsomes. This unique change in the metabolic pattern was accompanied by a marked decrease in total metabolism of both steroids and appeared to correlate apparently with their toxic potency. This kind of change was not shown by pretreatments with not only MC itself but also the phenobarbital-type(2,4,5,2',4',5'-hexachlorobiphenyl) and the mixed type PCBs(Kanechlor 400, a PCB mixture with 48% chlorine content), all of which possess only a low acute toxicity. The metabolic change produced by 3,4,5,3',4'-PenCB, 2,3,7,8-TCDF and 2,3,4,7,8-PenCDF might not be due to their stimulatory or inhibitory effects, because when added to the incubation mixture 3,4,5,3',4'-PenCB did not change the metabolic pattern with MC-microsomes to that with 3,4,5,3',4'-PenCB-microsomes. Furthermore, either 2,3,7,8-TCDF or 2,3,4,7,8-PenCDF gave similar metabolic pattern whereas their residual levels in the liver were greatly different from each other at the time of sacrifice. These results suggest that this kind of unique change of the steroid metabolism produced by highly toxic PCBs and PCDFs may be responsible, at least in part, for the endocrine symptoms caused by these compounds via disturbance of steroid homeostasis.

Animals↗

PubMed1982

Influences of the alteration in aortic pressure on regional myocardial function and regional myocardial blood flow in partial coronary artery occlusion.

This study was designed to simultaneously evaluate the effects of alterations in aortic pressure (AoP) on regional myocardial function and regional myocardial blood flow (MBF) in anesthetized dogs with partial coronary occlusion. Regional myocardial function was assessed by both segment-length and tension gauges. The left circumflex coronary artery flow was reduced to 50 to 70% by a constrictor. When systolic aortic pressure (AoPS) fell from 103.6 +/- 7.4 to 72.5 +/- 4.9 mmHg following nitroprusside infusion, systolic shortening (SS) markedly depressed from 0.63 +/- 0.17 to 0.09 +/- 0.20 mm (p less than 0.01), developed tension (DT) decreased by 30% (p less than 0.01), and MBF assessed with tracer microspheres decreased from 0.61 +/- 0.13 to 0.36 +/- 0.11 ml/min/Gm (p less than 0.01) in ischemic regions. In non-ischemic regions SS was enhanced from 0.78 +/- 0.16 to 0.89 +/- 0.15 mm (p less than 0.05), but DT and MBF showed no changes. An elevation of AoPS from 106.4 +/- 5.6 to 143.3 +/- 6.9 mmHg following methoxamine infusion brought about enhanced SS from 0.42 +/- 0.15 to 0.48 +/- 0.09 mm (p less than 0.05), a 50%-increase in DT (p less than 0.01), and was associated with an increase in MBF from 0.66 +/- 0.03 to 1.19 +/- 0.07 ml/min/Gm (p less than 0.01) in ischemic regions. These results indicate that, in partial coronary occlusion, a fall of AoP induces redistribution of blood flow away from ischemic regions and aggravates the function of the ischemic myocardium, while an elevation of AoP may produce beneficial effects upon the ischemic myocardium.

Animals↗

PubMed1982