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Biomedical subjects

P H Yu

Publications and source records attributed to P H Yu.

At least 163 records · Page 9Linked to original sources
PubMed1983

Specific photoactivated covalent binding of S-adenosylmethionine to phenylethanolamine-N-methyl transferase.

S-Adenosyl-L-methionine, the common methyl donor in enzymatic methylation systems, has been directly cross-linked to phenylethanolamine-N-methyltransferase from bovine adrenal medulla. Cross-linking was achieved by direct irradiation of a mixture of S-adenosyl-L-methionine and phenylethanolamine-N-methyl-transferase in Tris-HCl buffer (pH 7.5) by ultraviolet light at 254 nm. The cross-linking reaction is highly specific, as shown by a number of criteria. Phenylethanolamine-N-methyltransferase inhibitors S-adenosyl-homocysteine and SK & F 64139 can block this photoactivated cross-linkage. The S-adenosyl-L-methionine-phenylethanolamine-N-methyltransferase adduct is shown to be a homogeneous protein by Sephadex gel filtration, SDS-polyacrylamide gel electrophoresis and electrofocussing. Proteolytic digestion of this adduct releases one major S-adenosyl-L-methionine-labelled peptide, separable by paper chromatography. The results suggest that the cross-linking occurs at the specific active S-adenosyl-L-methionine-binding site of phenylethanolamine-N-methyltransferase.

Adrenal Medulla↗
PubMed1983

Trace acid levels in the plasma and MAO activity in the platelets of violent offenders.

The plasma concentrations of the unconjugated and conjugated so-called "trace acids," phenylacetic acid (PAA), m- and p-hydroxyphenylacetic acid (mHPA, pHPA), and platelet monoamine oxidase (MAO) activity were measured in 103 male prisoners detained in a psychiatric institution. Twenty-three had been convicted of violent crimes, 18 of sexual offenses, 24 of armed robbery, 27 of nonviolent property offenses, and 11 of miscellaneous nonviolent offenses. Unconjugated pHPA and conjugated PAA were found to be significantly reduced in the violent offenders when compared with those of the "nonviolent" groups. The levels of pHPA were also found to be low in sexual offenders. Platelet MAO activities to phenylethylamine, tryptamine, and p-tyramine between any of the categories of prisoners were not significantly different.

Adolescent↗
PubMed1983

Correlative relationship between biochemical activity and aggressive behaviour.

Correlative relationships were investigated between biogenic trace amines and histories of violence among offenders incarcerated in two federal penitentiaries. Plasma levels of unconjugated (U) and conjugated (C) trace acids (PAA, mHPA and pHPA) and platelet MAO activity to the substrates PE, TRYP and TA were assessed. A pilot study (N = 26) revealed a lower activity of MAO to TRYP among violent offenders. The factor analytically derived scale, Prison Disturbance, correlated with mHPA (U) .77 (p less than .001), mHPA(C) -.42 (p less than .05) and PAA (U) -.37 (p less than .10), controlling for time incarcerated. In the principal investigation (N = 103), PAA(C) (p less than .01), pHPA (U) (p less than .05) levels, and MAO activity to TRYP (p less than .05) were lower among violent offenders. Factor scores of biochemical activity produced even more significant results. However, when these results were cross validated with data from the pilot study, only minimal relationships were maintained.

Adult↗
PubMed1983

A study of the catabolism of trace amines in mentally disordered individuals with particular reference to agoraphobic patients with panic attacks.

Platelet MAO activity toward several trace amine substrates and the plasma levels of some trace acids have been investigated. Compared to controls, the agoraphobic patients were found to have significantly increased MAO activity. The substrate specificity in some of the patients appeared to be altered. The plasma levels of p-HPA and m-HPA were significantly lower than those of the control groups.

Adult↗
PubMed1983

Type A and B monoamine oxidase in glial cells in long-term culture.

Monoamine oxidase (MAO) in astroglial primary cultures increased during cell development. The enzyme activity towards type B substrate was further enhanced in cultures treated with 0.25 mM dibutyl cyclic AMP (dBcAMP), although dBcAMP (1 mM) does not effect MAO activity in vitro. It has been estimated that the dBcAMP treated cultures contain 70% type A and 30% type B MAO, while in the untreated one, there was virtually only type A MAO. Following the application of Percoll density gradient centrifugation, MAO associated with different subcellular fractions was obtained. The dBcAMP treated fractions were slightly heavier than the untreated ones.

Animals↗
PubMed1983

Platelet monoamine oxidase activity and trace acid levels in plasma of agoraphobic patients.

Platelet monoamine oxidase activity and plasma trace acid levels in 29 patients classified as agoraphobics was estimated. MAO activity towards p-tyramine and beta-phenylethylamine was found to be significantly higher in agoraphobics than in non-agoraphobic depressed patients and healthy controls. In addition plasma p-hydroxyphenylacetic acid levels were low in both agoraphobic and depressed patient groups. All patients were also assessed by Spielberger State Anxiety and the short form of the Beck Depression Inventory scales. No significant correlations could be found between platelet MAO activity or plasma trace acid levels and the psychological scores.

Adult↗
PubMed1982

Deuterium isotope effects in the ninhydrin reaction of primary amines.

The rate of development of Ruhemann's purple in the ninhydrin reaction of two deuterated primary amines, aa-d2-p-tyramine and aa-d2-beta-phenylethylamine, is significantly reduced. It appears to be a primary isotope effect and indicates that the cleavage of the carbon-hydrogen bond at the a-position is involved in the rate-determining step of the color reaction.

Amines↗
PubMed1982

Formation of 6 beta-hydroperoxyprogesterone in rat liver microsomes.

To verify the concept that molecular oxygen can be enzymically introduced as such into the steroid nucleus, radioactive progesterone and also 5-pregnene-3,20-dione were incubated with microsomal preparations of rat liver. In both cases, a significant amount of radioactive 6 beta-hydroperoxyprogesterone was isolated, together with 6 beta-hydroxyprogesterone and 6-oxoprogesterone. Addition of p-hydroxymercuribenzoate and mercurichloride significantly inhibited the formation of the hydroperoxide, whereas potassium cyanide and carbon monoxide were only partially inhibitory. Addition of 6 beta-hydroperoxyprogesterone to cytochrome P-450 containing fractions of hepatic microsomes induced a Type I difference spectrum characterized by an absorption maximum at 392 nm, a minimum at 420 nm, and an isosbestic point at 407 nm. At 4 degrees C, its apparent dissociation constant was found to be in the same order of magnitude as that of 6 beta-hydroxyprogesterone, namely 1.33 microM. A new pathway in rat liver for the formation of both 6 beta-hydroxyprogesterone and 6-oxoprogesterone via the 6 beta-hydroperoxide as a common precursor, is proposed.

Animals↗
PubMed1982

Plasma levels of phenylacetic acid, m- and p-hydroxyphenylacetic acid, and platelet monoamine oxidase activity in schizophrenic and other patients.

Blood from chronic schizophrenic patients in two hospitals (A and B) and from institutional and noninstitutional controls was analyzed for platelet monoamine oxidase (MAO) activity toward three different substrates (tryptamine, phenylethylamine, and p-tyramine) and for plasma levels of conjugated and unconjugated phenylacetic acid (PAA) and m- and p-hydroxyphenylacetic acids (mHPA and pHPA). Compared to the controls, schizophrenic patients were found to have significantly reduced MAO activity. Although significant differences were found between unconjugated PAA (reduced) in Hospital B, conjugated pHPA (increased) in Hospital A, and conjugated PAA (increased) in Hospitals A and B and noninstitutional controls, the most consistent significant finding was a reduced unconjugated mHPA in both groups of schizophrenic patients compared with both control groups.

Antipsychotic Agents↗
PubMed1982

Comparison of biochemical properties of platelet monoamine oxidase in mentally disordered and healthy individuals.

We have investigated some biochemical properties of platelet monoamine oxidase (MAO) isolated from chronic schizophrenic and agoraphobic patients, nonschizophrenic institutional controls, and healthy volunteers. The enzyme activity level in the healthy population was reasonably constant over at least a 6-week period. High correlations were found between MAO activity assessed for different substrates (p-tyramine, beta-phenylethylamine, and tryptamine). Some heterogeneity of the platelet MAO may exist, however, at least in some of the chronic schizophrenics, since the substrate specificities were changed and the Km values reduced. The half-life of the enzyme at 58 degrees C was 2-3 minutes and the transition temperature derived from Arrhenius plots was 16-17 degrees C with respect to beta-phenylethylamine. Platelet MAO from chronic schizophrenics was not significantly different from control values with respect to temperature effects. SDS-polyacrylamide gel electrophoresis of the 3H-pargyline-MAO adduct revealed that the subunit of platelet MAO is a single band protein with a molar individuals. The adjacent structure of the flavine site of the platelet MAO was chromatographically identical to the penta-peptide isolated from MAOs from other tissues. The response of platelet MAO to thimerosal, a new differential type A MAO inhibitor, could be distinguished not only from type A MAO isolated from human placenta, but also from type B MAO isolated from bovine liver.

Agoraphobia↗
PubMed1981

Susceptibility of monkeys to human hepatitis A virus.

A stump-tailed monkey, newly caught and without antibody to hepatitis B virus (HAV), was successfully infected with human HAV. The following alterations were observed in the monkey's functions: (1) elevation in activities of serum glutamic pyruvic transaminase, lactate dehydrogenase, and its type 5 isoenzyme (electrophoretically the fastest moving); (2) development of antibody to HAV; and (3) shedding of HAV antigen in feces. The virus isolated from the monkey, designated the Hangzhou A-1A strain of HAV, was serially transmitted to two other stump-tailed monkeys. Thus, the stump-tailed monkey (Macaca speciosa) is susceptible to infection with human HAV.

Animals↗