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Biomedical subjects

T Higashi

Publications and source records attributed to T Higashi.

At least 469 records · Page 26Linked to original sources
PubMed1978

An approach to nutritional therapy of hepatic encephalopathy by normalization of deranged amino acid patterns in serum.

A mixture with essential and nonessential amino acids high in branched chain amino acids and low in aromatic amino acids (Fischer solution), and another synthetic mixture of branched chain amino acids containing 3 amino acids associated with the urea cycle (Hep-OU) were infused to control subjects and patients with severe hepatic disease. Alterations in serum aminograms, blood ammonia levels and electroencephalograms following the infusion were studied and compared with those obtained by a commercially available amino acid mixture. Short-term or continuous infusion of a commercially available amino acid solution to cirrhotic patients caused an increase in methionine, phenylalanine and tyrosine and a decrease in branched chain amino acids. These post-infusion results were similar to the patterns seen in hepatic encephalopathy. In cirrhotic patients, infusion of Fischer solution which contains small quantities of methionine and phenylalanine produced an increase in the concentrations of these 2 amino acids, probably because of impaired utilization by the injured liver. No marked alterations in serum aminograms, however, were observed in cirrhotic patients either immediately after, or 3 h after, the end of the Hep-OU infusion. Reduction of methionine, tyrosine and phenylalanine levels and elevation of the molar ratio of (valine + leucine + isoleucine)/(phenylalanine + tyrosine) were significant. The infusion of Hep-OU to patients with liver cirrhosis or subacute hepatitis resulted in clinical and neurological improvements and the restoration of the molar ratio of branched chain amino acids/aromatic amino acids.

Amino Acids↗
PubMed1977

Rat liver glutathione: possible role as a reservoir of cysteine.

Rat liver contains a high concentration (7-8mM) of reduced glutathione and its level changes rapidly when starving or feeding rats. We concluded that one of the functions of liver glutathione was to act as a reservoir of cysteine. When starved rats were fed a protein-free diet, the increase in liver glutathione was dependent on the amount of cysteine added to the diet. A cysteine-dependent increase of glutathione was also observed in rats fed a diet containing gelatin with cysteine, but the increase was relatively lowered compared with rats fed a protein-free diet containing the same amount of cysteine. This suppression of the increase in glutathione was observed much more clearly when the gelatin diet was fortified with tryptophan in addition to cysteine. In the presence of tryptophan, L-[35S]-cysteine in the diet appeared to be incorporated primarily into liver and serum proteins, and degradation of liver glutathione must also have been enhanced. Addition of excess cysteine to the diet masked the effects of gelatin and tryptophan, stimulated glutathione synthesis in the liver as well as incorporation of dietary cysteine into protein fractions. Prolonged starvation of rats or injection of dibutyryl-3',5'-cyclic AMP lowered the glutathione level,but the level did not decrease below 2 to 3 mM. These findings suggest that there may be at least two pools of glutathione. A labile fraction, constituting one-third to one-half the total liver glutathione, probably serves as a reservoir of cysteine which can be released by gamma-glutamyl-transferase when necessary.

Animals↗
PubMed1977

A new factor from enteric bacteria of rats amplifying induction of liver enzyme by glucocorticoid. 2. Mechanism of action.

1. An amplifier of the action of glucocorticoid was purified from Proteus mirabilis as described previously. It was found that it amplified the induction of liver tyrosine aminotransferase by dexamethasone markedly with doses of dexamethasone that caused minimal enzyme induction, but had little effect with doses that caused maximal induction. Thus the amplification may represent a saving of glucocorticoid. The amplification of enzyme activity was brought about by increase in amount of enzyme. 2. The amplification was observed when the amplifier was administered before or with dexamethasone, but not when it was given 2 h after dexamethasone. These results and the finding that actinomycin D inhibited the amplification indicate that the amplifier does not act on the translational level of enzyme induction. 3. It was found that the amplifier increased both incorporation of [3H]dexamethasone into the cytosol and binding of [3H]dexamethasone of cytosol protein and that it decreased decay of the [3H]dexamethasone-protein complex.

Animals↗
PubMed1977

Gallium-67 scanning in the evaluation of therapy of malignant tumors of the head and neck.

Gallium-67 scintigraphy was performed on 25 patients with a variety of malignant tumors of the head and neck in order to evaluate the susceptibility of the tumors to irradiation and chemotherapy before treatment and to monitor the effectiveness of therapy. If certain limitations are borne in mind, gallium scanning may prove a valuable tool in planning and evaluating therapy of malignant tumors.

Adult↗
PubMed1977

Studies on rat liver catalase. IX. Role of methionine in polypeptide chain inhibition.

Initiation with methionine of the synthesis of rat liver catalase [EC 1.11.1.6] has been investigated. Analysis of the N-terminal residue of nascent catalase peptides labeled in vivo with injected radioactive amino acids, including [3H]methionine, indicated a remarkably high content of methionine. By fractionating [3H]methionine-labeled nascent catalase according to chain length, it was found that peptides of shorter chain length contained more N-terminal methionine relative to total methionine incorporated. In addition, only a small amount of [3H]methionine was detected as the N-terminal amino acid when newly completed catalase was examined by Edman degradation. These results indicate that the synthesis of liver catalase is initiated with methionine, and suggest the presence of a mechanism for its subsequent removal from the N-terminal position. Catalase was also synthesized in a cell-free system directed by the catalase mRNA, using [3H]Met-tRNAf or [3H]Met-tRNAm. The results obtained in such in vitro experiments were in good agreement with those from in vivo studies, and further showed that the N-terminal methionine was provided by a specific initiator tRNA, i.e. tRNA Met f.

Animals↗
PubMed1976

Biosynthesis of rat kidney catalase. Double-labeling by [14C]leucine and delta-amino[3H]levulinic acid.

Kidney catalase [EC 1.11.1.6] was doubly labeled by injecting a mixture of [14C]-leucine and delta-amino[3H]levulinic acid (ALA) into normal and allyliso-(2-isopropyl-4-pentenoyl)urea (Sedormid)-treated rats. Shortly after the injection of a tracer dose or the precursors, catalase in microsomes showed the highest specific radioactivities among catalases from various cell fractions. On the other hand, peroxisomal catalase was labeled gradually, reaching a plateau at about 90 min. The patterns of incorporation of both isotopes were similar to those obtained previously with rat live catalase, except that the 3H-radioactivities were much higher. From the results obtained it could be postulated that kidney catalase is synthesized on polysomes and then transferred to peroxisomes, directly or via the soluble phase. The ratio of 3H/14C incorporated was lowest in microsomal catalase, highest in microsomal catalase, highest in peroxisomal enzyme and intermediate in catalase of the soluble fraction. The increment with time was large in the latter two catalases, while the former showed a rather small change. The evidence suggests that nascent catalase contains less heme than the completed molecule; further addition of heme to this intermediate seems to occur in the cytosol, and possibly also in peroxisomes. Administration of a porphyrinogenic drug, (2-isopropyl-4-pentenoyl)urea, produced a remarkable decrease in the incorporation of [3H]ALA into kidney catalase, with no significant effect on that of [14C]leucine.

Aminolevulinic Acid↗
PubMed1976

Higher transpeptidation activity and broad acceptor specificity of gamma-glutamyltransferases of tumors.

The gamma-glutamyltransferase (EC 2.3.2.2) (=gamma-glutamyltranspeptidase, gamma-GTP) activity in hepatoma induced by 3'-methyl-4-(dimethylamino)azobenzene (3'-Me-DAB) was 120-fold higher than that of normal liver and high activity was also found in bovine hepatocellular carcinoma. gamma-GTPs from these malignant tissues responded more and showed broader specificity to gamma-glutamyl group acceptors than those from normal tissue such as bovine, rat, and mouse liver and bovine kidney. Three species of gamma-GTP were isolated from bovine kidney by DEAE-cellulose chromatography, whereas only two species were isolated from bovine hepatocellular carcinoma. The carcinoma lacked the least acidic enzyme species. Appropriate gamma-glutamyl group acceptors stimulated more-acidic enzyme species more than less-acidic species in both tissues. The fractions separated from the hepatoma were stimulated more than those of kidney by gamma-glutamyl group acceptor. The enzymes from normal tissues responded similarly to a gamma-glutamyl group acceptor irrespective of the difference in their activity. Thus, gamma-GTPs of malignant tissues appear to be more versatile for amino acid transport, both qualitatively and quantitatively. In these properties the enzyme of mouse fetal liver which showed the highest activity in the last period of pregnancy resembled the enzymes of malignant rather than normal tissues. The activity of hepatic gamma-GTP is not parallel with the rate of cell proliferation during normal development.

Amino Acids↗
PubMed1975

Energy-transducing membrane-bound coupling factor-ATPase from Mycobacterium phlei. I. Purification, homogeneity, and properties.

The membrane-bound coupling factor from Mycobacterium phlei was solubilized from membrane vesicles by washing with low ionic strength buffer or 0.25 M sucrose. The solubilized enzyme exhibited coupling factor, latent ATPase, and succinate oxidation-stimulating activity. Purification by affinity chromatography using Sepharose coupled to ADP yielded a homogeneous preparation of latent ATPase which was purified about 200-fold with an 84% yield in a single step. Purified latent ATPase exhibited coupling factor activity but no succinate oxidation-stimulating activity. The molecular weight of latent ATPase was determined to be 250,000 +/- 10,000 by Sephadex G-200 chromatography. The ATPase was unmasked by trypsin treatment and activated by Mg2+ ion. However, trypsin treatment inactivated the coupling factor activity in the purified enzyme, indicating that the catalytic sites for ATPase and coupling activity are different. Unlike mitochondrial ATPase, latent ATPase from M. phlei was not cold-labile. Of the nucleoside triphosphates, UTP, ITP, and epsilon-ATP (1-N6-ethenoadenosine triphosphate) were hydrolyzed to a lesser extent compared to ATP. Kinetic data showed that ADP acted as a competitive inhibitor of latent ATPase activity with a Ki of 5 x 10(-3) M. Uncouplers of oxidative phosphorylation and respiratory inhibitors did not affect the latent ATPase activity, while sodium azide (0.1 mM) inhibited the latent ATPase activity.

Adenosine Triphosphatases↗
PubMed1975

Clinical evaluation of 67Ga-citrate scanning in the oral region.

Gallium-67-citrate was administered to thirty-nine patients who had a variety of benign, malignant, and inflammatory lesions of the oral region. The gallium-67 scintigram was noted to be valuable in the diagnosis of maxillary carcinoma, parotid carcinoma, and malignant lymphoma. Clinically, it is possible to differentiate malignant tumors from benign ones with the aid of 67Ga scanning. It is difficult, however, to differentiate malignant tumors from inflammatory lesions. At present, it is difficult to defect the small malignant lesion by means of a 67Ga scintigram.

Adolescent↗