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Biomedical subjects

P H Yu

Publications and source records attributed to P H Yu.

At least 181 records · Page 10Linked to original sources
PubMed1981

Studies on the pargyline-binding site of different types of monoamine oxidase.

[3H]Pargyline has been covalently linked to active sites of both type A and type B monoamine oxidase (MAO) obtained from various tissues. Rat heart and human placenta were chosen to represent predominantly type A MAO, pig and bovine livers to represent type B MAO, and rat liver and brain to represent mixed type A and type B MAO's. The [3H]pargyline-MAO adducts were isolated and hydrolyzed by proteolytic enzymes, and the labelled peptides (pargyline-binding sites) separated and compared by paper chromatography and by paper electrophoresis at various pH values. Only one common pargyline peptide was obtained from all the different MAO's. The alternative A and B sites were assessed after preincubation of rat liver MAO with the selective inhibitors deprenyl (to block the B site) and clorgyline (to block the A site). Following proteolysis of the [3H]pargyline of both type A and type B MAO from this pretreated rat liver, MAO has been purified by a series of chromatographic and electrophoretic procedures. Micro-Edman degradation, followed by dansylation, revealed the amino acid sequence to be Ser-Gly-Gly-Cys(X)-Tyr. It is concluded that the primary structures immediately surrounding the pargyline-binding sites are identical for both type A and type B MAO in these tissues.

Amino Acid Sequence↗
PubMed1981

Studies on the transmission of human hepatitis A virus to stump-tailed monkey.

The newly-caught stump-tailed monkeys (Macaca speciosa) with negative antibody to hepatitis A were inoculated with human hepatitis A virus. The following findings were observed in the monkeys after inoculation: (i) the elevation of activities of the serum glutamic-pyruvic transaminase, lactate dehydrogenase and its isoenzyme (LDH5), (ii) the seroconversion of antibody to hepatitis A virus. (iii) the shedding of hepatitis A antigen in feces. These findings show that the stump-tailed monkey (Macaca speciosa) is susceptible to infection of human hepatitis A virus. The virus recovered from the feces of the infected monkey, named as Hang-zhou A-1A strain of hepatitis A virus, has experienced two generations of successful transmission in monkeys.

Animals↗
PubMed1980

Dopamine-beta-hydroxylase and its apparent endogenous inhibitory activity in the plasma of some psychiatric patients.

The "apparent" and "absolute" levels of dopamine-beta-hydroxylase (DBH) in 62 psychiatric patients and 20 healthy control subjects have been investigated. No significant differences could be detected between control subjects and patients diagnosed as schizophrenic, unipolar depressive and bipolar depressive, when DBH was assayed in the presence of the anti-inhibitors Cu++ and N-ethylmaleimide (i.e., "absolute" DBH activity). In the absence of these anti-inhibitors, however, the levels of plasma DBH (i.e., "apparent" DBH activity) were considerably reduced in all cases, with the schizophrenic group also being significantly reduced (p less than 0.02) in comparison with the control group.

Adult↗
PubMed1980

Patterns of shedding of hepatitis A virus antigen in feces and of antibody responses in patients with naturally acquired type A hepatitis.

Serial stools and sera from 13 patients with hepatitis A were collected during an epidemic in 1978 in a rural village near Hangzhou, China, and were studied to determine the patterns of shedding of hepatitis A antigen (HAAg) and of antibody response in some cases. Of 44 stool specimens, 31 were HAAg-positive by a radioimmunoprecipitation-polyethylene glycol assay. The highest percentage of HAAg positivity was in stools collected one week before and one week after the peak elevation of serum glutamic pyruvic transaminase (SGPT) levels, and peak HAAg shedding in each patient usually occurred in the early stools. Fecal shedding of HAAg was detected as early as day 19 before peak elevation in SGPT level and as late as day 11 afterward and continued for at least 25 days. The pattern of HAAg shedding in feces and of complement-fixation and immune adherence antibody response in relation to the change in SGPT activity and jaundice in four patients with hepatitis A was demonstrated.

Alanine Transaminase↗
PubMed1979

Kidney lipids: changes caused by dietary 9-trans, 12-trans-octadecadienoate.

Trans,trans-linoleate at 50 and 100% of dietary fat decreased kidney size and altered its composition. Trans,trans-linoleate as the sole source of dietary fat impaired growth and caused more severe symptoms of essential fatty acid deficiency than was observed with hydrogenated coconut oil (HCO). The concentration of renal cholesterol, phospholipids (PL), triglycerides (TG) and cholesteryl esters (CE) were also decreased. Linoleic (18:2), homo-gamma-linolenic acid (20:3n6) and arachidonic acid (20:4n6) were significantly depressed in lipid classes, especially in PL and CE, by dietary trans,trans-linoleate. The increase in eicosatrienoate (20:3n9), especially in PL and CE of kidneys of rats fed HCO (essential fatty acid deficient), was slight in rats fed 100% trans,trans-linoleate, indicating that the trans,trans acid probably inhibited acyl elongation and desaturation.

Animals↗
PubMed1979

N-acylation of tyramines: purification and characterization of an arylamine N-acetyltransferase from rat brain and liver.

The N-acylation of tyramine isomers and other biogenic amines has been studied. The liver exhibits the highest activity towards tyramines, while the brain exhibits a low but significant activity. In the brain, tyramine N-acylation activity was heterogenously distributed. The arylamine N-acetyltransferase has been partially purified from both rat liver and brain, the two enzymes being quite similar with respect to their chromatographic properties, optimal pH requirement (pH 7.8), and their kinetic parameters. The product N-acetyltyramine is not oxidized by liver amidohydrolase or monoamine oxidase.

Acetyltransferases↗
PubMed1978

Phenylethanolamine N-methyltransferase from the brain and adrenal medulla of the rat: a comparison of their properties.

Two different molecular forms of phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1) have been isolated from the brain and adrenal glands of the rat as indicated by certain of their physicochemical properties, such as: molecular weight estimated on the basis of gel chromatography of Sephadex G-100; pH optima; electrophoretic mobility on acrylamide gel; and steady-state kinetic parameters. The high Km value for the brain PNMT has been assumed to be responsible for the low methylation ratio between norepinephrine and epinephrine in the CNS.

Adrenal Medulla↗
PubMed1976

Isolation of specific protease inhibitors from Neurospora crassa.

Four natural protease inhibitors have been partially purified by heat treatment, ion-exchange chromatography pand gel filtration from Neurospora crassa. The inhibitory activity has been estimated by measuring the inhibition of proteolysis of casein as well as by the protection of Neurospora tryptophan synthase from proteolytic inactivation. The inhibitors are all oligopeptides and possess molecular weights in the range 5000-24 000 and appear to be very specific to Neurospora proteases. They may be classified into two types. The first are specific to Neurospora alkaline protease and the second to acidic protease. None of them exhibited any effect on other proteases including trypsin, chymotrypsin, papain, pepsin, thermolysin, subtilisin and proteinase K. The possible physiological role of these inhibitors is discussed.

Bacterial Proteins↗
PubMed1976

Some observations on the interaction of dopamine-beta-hydroxylase and its natural inhibitors in the rat brain.

The difficulty of assaying dopamine beta-hydroxylase (DbetaH) (EC 1.14.17.1) has been circumvented by including N-ethylmaleimide (5 X 10(-2) M) in the incubation mixture along with a small amount of Cu2+ (20-60 muM). Such a procedure ensures that the maximum DbetaH activity is assessed in all extracts. As a result, the absolute levels of DbetaH in various regions of the rat brain have been established. The DbetaH values obtained are higher by 40% in the hypothalamus and 20% in the cerebral cortex, spinal cord, and caudate nucleus than those previously reported. The mechanism of the synergic effect seen when N-ethylmaleimide and Cu2+ are combined is not presently understood.

Adrenal Glands↗
PubMed1975

Proteolytic enzymes of Neurospora crassa. Purification and some properties of five intracellular proteinases.

Five intracellular proteolytic enzymes from Neurospora crassa were isolated and partially characterized: an acidic and an alkaline endopeptidase, one carboxypeptidase and two aminopeptidases. All these proteinases were purified from the same crude extract to homogenity by heat treatment, precipitation with ammonium sulfate, chromatography on DEAE-cellulose, CM-cellulose, DEAE-Sephadex, hydroxyapatite and by gel filtration. The acid proteinase hydrolysed acid-denatured haemoglobin at pH 3.0. The alkaline proteinase and the carboxypeptidase are serine proteinases that require a sulfhydryl group for activity. The aminopeptidases are both metallo-proteinases; one posseses broad specifity to the B-chain of oxidized insulin, the other posseses only narrow specifity and can only split the N-terminal basic amino acids of peptides.

Aminopeptidases↗