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Biomedical subjects

K Tagawa

Publications and source records attributed to K Tagawa.

At least 91 records · Page 5Linked to original sources
PubMed1991

Alzheimer's disease amyloid beta-clipping enzyme (APP secretase): identification, purification, and characterization of the enzyme.

Alzheimer's disease (AD) is the most frequent cause of dementia, although no genetic abnormality has been identified. Recent studies have elucidated the molecular defect in AD, including the abnormal deposition of amyloid beta peptide (beta/A4) in senile plaques of affected individuals. Normal brain contains the enzyme, APP secretase, which cleaves inside the beta/A4 portion of the precursor protein (APP); abnormal processing of APP occurs in AD brain. Until now, no evidence has been provided that APP secretase is an intracellular proteinase. We have now prepared two synthetic substrates of APP secretase, both of which contain the cleavage point and are much more sensitive than substrates previously available to identify APP secretase. Using these substrates, we found an intracellular proteinase that has APP secretase activity. This proteinase has been identified as cathepsin B.

Alzheimer Disease↗
PubMed1991

Organ assimilation of peptides.

Dipeptides injected intravenously or added to liver perfusion medium were hydrolyzed rapidly to amino acids. The clearance volumes per min of plasma Gly-Phe and Gly-Lys were 63% and 224%, respectively, of the total plasma volume. These values far exceed the blood flow in any single organ, suggesting that several organs must be involved in peptide assimilation. Intravenous administration of peptides increased the levels of their constituent amino acids in organs. Two possible explanations for this were assimilation of the peptides by the organs, and transport into the organs of the amino acids generated by extracellular hydrolysis of the peptides. The former possibility was tested by eliminating plasma lysine by enzymic degradation, so that the amino acid would accumulate only in the organs that assimilate lysine-containing peptides. Results showed that all organs tested, except the brain, had an intrinsic ability to assimilate peptides.

Animals↗
PubMed1991

Relationship of HBsAg subtypes with HBeAg/anti-HBe status and chronic liver disease. Part I: Analysis of 1744 HBsAg carriers.

A total of 1744 HBsAg carriers were investigated to determine whether there are clinical differences among HBsAg subtypes or not. Although adr was more predominant than adw in 1078 asymptomatic carriers as well as in 666 carriers with liver dysfunction, the adr carriers had liver dysfunction more frequently than the adw carriers (p = 0.005). In addition, the adr carriers were more often positive for HBeAg and less often positive for anti-HBe than the adw carriers (p less than 0.001). Multivariate analyses indicated that the HBsAg subtypes were associated with liver dysfunction not directly but through the relationship between the HBsAg subtypes and HBeAg/anti-HBe status. HBeAg/anti-HBe status of each age bracket in the adr carriers and in the adw carriers suggested that adr carriers are seroconverted later than adw carriers. In conclusion, HBsAg subtypes may affect the development of chronic liver disease, through their association with HBeAg/anti-HBe status.

Adult↗
PubMed1991

Relationship of HBsAg subtypes with HBeAg/anti-HBe status and chronic liver disease. Part II: Evaluation of epidemiological factors and suspected risk factors of liver dysfunction.

In this study, we examined a possibility that epidemiological factors or suspected risk factors of liver dysfunction could account for the different HBeAg/anti-HBe status or the different prevalence of liver dysfunction between the adr and adw carriers. A total of 428 HBsAg carriers were surveyed of their age, sex, racial background, socioeconomic status, place of residence, birthplace, alcohol consumption, smoking habit, and history of blood transfusion as epidemiological factors or suspected risk factors of liver dysfunction. Adjustment for those variables using multivariate analyses did not substantially affect the association of the HBsAg subtypes with either prevalence of liver dysfunction or HBeAg/anti-HBe status. HBsAg subtypes seem to directly affect HBeAg/anti-HBe status and consequently influence development of chronic liver disease.

Adult↗
PubMed1990

Isolation of a gene for a regulatory 15-kDa subunit of mitochondrial F1F0-ATPase and construction of mutant yeast lacking the protein.

A gene coding for yeast 15-kDa protein, a regulatory factor of mitochondrial F1F0-ATPase, was isolated. The cloned gene was disrupted in vitro and mutant strains that did not contain the 15-kDa protein were constructed by transformation of yeast cells with the disrupted gene. The ATP-synthesizing activity of the mutant mitochondria was the same as that of wild-type cells, suggesting that the 15-kDa protein is not required for mitochondrial oxidative phosphorylation. Collapse of the membrane potential induced ATP-hydrolyzing activity of F1F0-ATPase of the mutant mitochondria but not of normal mitochondria. Activation of the enzyme was also observed during incubation of submitochondrial particles from mutant cells, but not of those from wild-type cells. Thus, it is inferred that the 15-kDa protein supports the action of an intrinsic ATPase inhibitor of the ATP-hydrolyzing activity of the enzyme upon de-energization of mitochondrial membranes.

Amino Acid Sequence↗
PubMed1990

Activation of ATP hydrolysis by an uncoupler in mutant mitochondria lacking an intrinsic ATPase inhibitor in yeast.

An intrinsic ATPase inhibitor and 9-kDa protein are regulatory factors of mitochondrial ATP synthase in Saccharomyces cerevisiae. A gene encoding the ATPase inhibitor was isolated from a yeast genomic library with synthetic oligonucleotides as hybridization probes and was sequenced. The deduced amino acid sequence showed that the precursor protein contains an amino-terminal presequence of 22 amino acid residues. Mutant strains that did not contain the inhibitor and/or the 9-kDa protein were constructed by transformation of cells with their in vitro disrupted genes. The disruption of the chromosomal copy in recombinant cells was verified by Southern blot analysis, and the absence of the proteins in the mutant cells was confirmed by Western blot analysis. All the mutants could grow on a nonfermentable carbon source and the oxidative phosphorylation activities of their isolated mitochondria were the same as that of normal mitochondria. However, an uncoupler, carbonylcyanide-m-chlorophenylhydrazone, induced marked ATP hydrolysis in the inhibitor-deficient mitochondria, but not in normal mitochondria. These observations suggest that the ATPase inhibitor inhibits ATP hydrolysis by F1F0-ATPase only when the membrane potential is lost.

Adenosine Triphosphate↗
PubMed1990

Transport of glutathione across the mitochondrial membranes.

Transport of glutathione (GSH) into mitochondria was observed when mitochondria in state 4 respiration were incubated with high concentrations of GSH. This transport was suppressed by antimycin A or dicyclohexyl-carbodiimide, or in state 3 respiration. Upon dissipation of the proton gradient by a proton ionophore, mitochondrial GSH was released into the medium. GSH moved freely across the proton-permeated mitochondrial membrane, its movement depending only on the GSH gradient across the inner membrane. These results indicate that there is a transport system for GSH in the mitochondrial membrane, and that a proton gradient is necessary to maintain GSH in the matrix, and to transport GSH into mitochondria.

Animals↗
PubMed1990

Leakage of cytoplasmic enzymes from rat heart by the stress of cardiac beating after increase in cell membrane fragility by anoxia.

The effects of spontaneous beating after anoxia and the pumping stress induced by a left ventricular balloon on the leakage of myocardial enzymes from the isolated perfused rat heart were investigated. Beating of the heart was arrested by perfusion with high-K+ medium. When the beating was arrested during reoxygenation after anoxia, the leakage of lactate dehydrogenase (LDH) was significantly lower than during reoxygenation with spontaneous cardiac beating. After changing from K+ arrest to spontaneous beating by perfusion with low-K+ medium during reoxygenation, the leakage of LDH increased markedly. Imposition of left ventricular wall stress on the K(+)-arrested heart by repetitive passive distension during aerobic perfusion and after 20 min and 60 min of anoxia caused LDH leakages of 1.0, 4.6 and 21.0 units/g in 30 min, respectively. Under this mechanical stress, the release of LDH as a percentage of its total myocardial activity coincided well with that of cytoplasmic aspartate aminotransferase (AST), while the percentage release of mitochondrial AST was much less. These results appeared to indicate that the leakage of cytoplasmic enzymes during reoxygenation is accelerated by cardiac beating because of fragility of the cell membranes developing during the preceding anoxia.

Adenosine Triphosphate↗
PubMed1990

Regulatory proteins of F1F0-ATPase: role of ATPase inhibitor.

An intrinsic ATPase inhibitor inhibits the ATP-hydrolyzing activity of mitochondrial F1F0-ATPase and is released from its binding site on the enzyme upon energization of mitochondrial membranes to allow phosphorylation of ADP. The mitochondrial activity to synthesize ATP is not influenced by the absence of the inhibitor protein. The enzyme activity to hydrolyze ATP is induced by dissipation of the membrane potential in the absence of the inhibitor. Thus, the inhibitor is not responsible for oxidative phosphorylation, but acts only to inhibit ATP hydrolysis by F1F0-ATPase upon deenergization of mitochondrial membranes. The inhibitor protein forms a regulatory complex with two stabilizing factors, 9K and 15K proteins, which facilitate the binding of the inhibitor to F1F0-ATPase and stabilize the resultant inactivated enzyme. The 9K protein, having a sequence very similar to the inhibitor, binds directly to F1 in a manner similar to the inhibitor. The 15K protein binds to the F0 part and holds the inhibitor and the 9K protein on F1F0-ATPase even when one of them is detached from the F1 part.

Adenosine Diphosphate↗
PubMed1990

A case report of primary fibrosarcoma of the liver.

A 75-year-old woman was admitted to our hospital complaining of right hypochondrial pain. Echo sonography and computed tomography demonstrated a large tumor with irregular internal density in the right lobe of the liver. Angiography revealed a moderately hypervascular tumor. She was treated with transcatheter arterial embolization. Three weeks later, the tumor ruptured. She died of accompanying acute myocardial infarction seven months after the onset of the illness. Autopsy revealed primary fibrosarcoma of the liver. The tumor appearance varied from firm whitish to soft myxomatous. A part of the tumor showed hemorrhagic necrosis. There was no intrahepatic metastasis. The tumor tissue was composed of spindle shaped cells and immunohistochemically stained with vimentin.

Aged↗
PubMed1990

Simultaneous bindings of ATPase inhibitor and 9K protein to F1F0-ATPase in the presence of 15K protein in yeast mitochondria.

Yeast mitochondrial ATP synthase has three regulatory proteins, ATPase inhibitor, 9K protein, and 15K protein. The 9K protein binds directly to purified F1-ATPase, as does the ATPase inhibitor, but the 15K protein does not [Hashimoto, T. et al. (1987) J. Biochem. 102, 685-692]. In the present study, we found that 15K protein bound to purified F1F0-ATPase, forming an equimolar complex with the enzyme. The apparent dissociation constant was calculated to be 1.4 x 10(-5) M. The ATPase inhibitor and 9K protein also bound to F1F0-ATPase in the presence of ATP and Mg2+, and the dissociation constants of their bindings were about 3 X 10(-6) M. They bound to the enzyme competitively in the absence of 15K protein, but in its presence, they bound in equimolar amounts to the enzyme. The ATP-hydrolyzing activity of the enzyme-ligand complex was greatly influenced by the order of bindings of ATPase inhibitor and 9K protein: when the ATPase inhibitor was bound first, the activity of the enzyme was inhibited completely and was not restored by 9K protein, but when 9K protein was added first, the activity was inhibited only partially even after equimolar binding of the ATPase inhibitor to the enzyme. These observations strongly suggest that the 15K protein binds to the F0 part and functions to hold the ATPase inhibitor or 9K protein on the F1 subunit.

Adenosine Triphosphatases↗
PubMed1990

Kinetics of hydroperoxide degradation by NADP-glutathione system in mitochondria.

Hydroperoxide decomposition by the NADP-glutathione system in rat liver mitochondria was analyzed. Mitochondria were found to contain high concentrations of the reduced form of glutathione (GSH) (4.32 +/- 0.50 nmol/mg) and NADPH (4.74 +/- 0.64 nmol/mg), and high activities of glutathione peroxidase and reductase. In the initial phase of the reaction, the rate of hydroperoxide decomposition was proportional to both the GSH level and the activity of GSH peroxidase. However, in the later steady state, the step of NADP reduction was rate-limiting, and the overall reaction rate was independent of the initial concentration of GSH, and activities of glutathione peroxidase and reductase. Some GSH was released from mitochondria during incubation, but the rate of the decomposition could be simply expressed as kappa [GSH]/2, where kappa is the first-order rate constant of the peroxidase and [GSH] is the intramitochondrial level of GSH in the steady state. The rate of the reaction in the steady state was also dependent on the NADPH level, its reciprocal being linearly correlated with [NADPH]-1. The rate of decomposition of hydroperoxide was influenced by the respiratory state. During state 3 respiration, the rate was greatly depressed, but was still considered to exceed by far the rate of physiological generation of hydroperoxide.

Animals↗
PubMed1990

Human plasma gelsolin binds adenosine triphosphate.

Binding studies of human plasma gelsolin with ATP were done by equilibrium dialysis. Analysis of the binding data showed that plasma gelsolin had one class of ATP binding site with Kd = 2.8 x 10(-7) M, which saturated at an ATP/gelsolin ratio of 0.6. The bioluminescent assay for ATP with luciferin and firefly luciferase confirmed that the protein contained a nucleotide as ATP.

Adenosine Triphosphate↗
PubMed1990

Clinical evaluation of a direct colorimetic method for determination of amniotic phospholipids.

Evaluation of amniotic phospholipids, which are a parameter of fetal lung maturation, is important in the management of premature infants. The method available for measuring the lecithin/sphingomyelin (L/S) ratio, which appears to provide an index to fetal lung maturity, is laborious, involving determinations of phospholipids, and so is unsuitable for rapid quantitative measurement of phospholipids in the amniotic fluid in the perinatal period. We developed a simple, sensitive colorimetric assay for phospholipids without their extraction. This assay is based on the fact that phospholipids form stable hydrophobic complexes with Co(SCN)4, Fe(SCN)2- and Fe(SCN)3 within about 1 hr. Amniotic fluid samples (n = 115) were collected from women with normal and abnormal pregnancies in week 16-41 of pregnancy, and these samples were examined both by thin layer chromatography (TLC) and by our method of phospholipid determination. Good correlations were observed between the L/S ratio determined by TLC and the values obtained by this method. Moreover the distributions of the dipalmitoylphosphatidylcholine (DPPC) content and DPPC/sphingomyelin (SM) ratio were similar to those of the PC content and L/S ratio. This method was proved to be more accurate than other methods such as TLC and the shake test for predicting neonatal RDS.

Amniotic Fluid↗
PubMed1990

Occipital lobe infarction and positron emission tomography.

Even though the PET study revealed a total infarct in the territory of the left PCA in our 3 cases of pure alexia, it is still obscure which part of the left occipital lobe is most closely associated with the occurrence of the pure alexia. In order to elucidate the intralobar localization of the pure alexia, it is needed to have an ideal case who shows an pure alexia due to the localized lesion within the left occipital lobe. Furthermore, high-resolution PET scanner will circumvent the problem in detecting the metabolism and blood flow in the corpus callosum which plays an important role in the pathogenesis. We have shown that the occlusion of the right PCA also produced a left unilateral agnosia which is one of the common neurological signs in the right MCA infarction. To tell whether the responsible lesion for the unilateral spatial agnosia differs between the PCA occlusion and the MCA occlusion, the correlation study should be carried out in a greater number of the subjects. Two distinctive neuropsychological manifestations, cerebral color blindness and prosopagnosia, have been considered to be produced by the bilateral occipital lesion. The PET studies disclosed reduction of blood flow and oxygen metabolism in both occipital lobes in our particular patient who exhibited cerebral color blindness and prosopagnosia.

Aged↗