PubMed Health⌕ Search

Biomedical subjects

K S Hui

Publications and source records attributed to K S Hui.

At least 37 records · Page 2Linked to original sources
PubMed1986

Cross-reactive red blood cell antigen-related substances in human leukocyte alpha interferon.

Human leukocyte alpha interferon (IFN alpha) is a blood product. The possible contamination with blood-group antigens was studied using the double-immunodiffusion technique. With the exception of one lot received in 1980, which did not react, all three recent lots received in 1983 and 1984 reacted with 16, 20, and 21 of the 22 erythrocyte group-specific antisera tested. The only antiserum that did not react with any of the IFN alpha lots was anti-N. Preincubation of the IFN alpha with antisera abolished the precipitate lines seen in double immunodiffusion. Recombinant human alpha interferon used as a control did not show any reaction. Our results indicate the presence of red blood cell antigen-related substances in IFN alpha.

Cross Reactions↗
PubMed1986

Effect of several amino acid phosphonates and other compounds on rat brain and kidney peptidases.

A series of N-terminal phosphonate derivatives, H2O3PCHPhNHR (R = Leu, Phe, Trp, and/or Tyr), were synthesized with the aim of mimicking phosphoramidon, a potent inhibitor of enkephalinase, while avoiding the lability of the scissile P-N bond. All of the N-phosphonobenzyl derivatives of the amino acids, including the substituted succinylhydrazobenzophenone compounds, were inactive toward rat brain aminopeptidase and rat kidney carboxypeptidase. The N-monobenzylphosphonobenzyl derivatives, PhCH2OPO(OH)CHPhNHR, of individual amino acids and several of the N-phosphonobenzyl dipeptides showed inhibition in the micromolar range toward the soluble exopeptidase but were inactive with both the brain and kidney endopeptidase.

Aminopeptidases↗
PubMed1985

Proctolin: a potent inhibitor of aminoenkephalinase.

Proctolin is a potent selective inhibitor of aminoenkephalinase. The specificity of its inhibition of various aminopeptidases is similar to that of puromycin; it inhibits aminoenkephalinase, but not leucine aminopeptidase or aminopeptidase M. Enkephalin breakdown by synaptic plasma membrane, but not by brain slices, is sensitive to proctolin. The inhibition by proctolin is partially caused by its resistance to enzymatic breakdown. The inhibition is of mixed type and is concentration dependent, and the two amino acids at the N-terminal are important for its action. The minimal structure for inhibition is a dipeptide with a basic amino acid at the N-terminal and a basic or an aromatic amino acid at the C-terminal.

Aminopeptidases↗
PubMed1985

An opiate receptor-associated aminopeptidase that degrades enkephalins.

During the purification of opiate receptor by affinity chromatography on wheat germ agglutinin-agarose, an aminopeptidase is coeluted with the receptor. Virtually all of both the enzyme and the receptor is retained on the hydroxylapatite column. The aminopeptidase functions optimally at neutral pH and is activated by Mn2+. The enzyme is sensitive to dithiothreitol, is inhibited by amastatin and bestatin, and is insensitive to puromycin. The enzyme seems to be linked to the receptor, since its activity is enhanced by D-Ala2-Met-enkephalinamide or naltrexone. The properties of this aminopeptidase indicate that it is distinct from neutral arylamidase, leucine-aminopeptidase, aminopeptidases A and B, brain acidic aminopeptidase, and the membrane aminoenkephalinase that we purified recently (4).

Aminopeptidases↗
PubMed1985

The endocrine glands in Pompe's disease. Report of two cases.

Pompe's disease (type II glycogenosis), an infantile form of generalized glycogenosis, is characterized biochemically by deficiency of lysosomal acid alpha-1,4-glucosidase and morphologically by intralysosomal glycogen storage in multiple organs, notably the central nervous system, heart, liver, and skeletal muscles. The endocrine system has not been described in detail in the literature. In two infants with Pompe's disease, intralysosomal glycogen was identified in the adrenal cortex and medulla, thyroid gland, parathyroid glands, pancreatic islets, and pituitary gland. Of special interest is the severe glycogen accumulation in the zona fasciculata of the adrenal glands.

Adrenal Glands↗
PubMed1984

Clinicopathological correlations of disseminated intravascular coagulation in patients with head injury.

To try to define the significance of disseminated intravascular coagulation (DIC) in head-injured patients, we correlated clinical, laboratory, and pathological findings in 16 patients with head injury as their main problem who had DIC, who died within 4 days of injury, and who were examined postmortem. Patients were ranked according to the number of abnormal laboratory screening tests for DIC and the severity of these abnormalities. The most frequently abnormal laboratory tests were the fibrinogen degradation products and fibrinogen, followed in order by the activated partial thromboplastin time, prothrombin time, and thrombin time. The platelet count was the least abnormal value. The patients with the fewest abnormalities had the least abnormal computed tomographic scans. Autopsy reports revealed necrosis and bleeding in the brain and in a number of other organs, particularly the lungs. Microthrombi were not reported in the original autopsy reports. However, when these cases were reevaluated and their slides were stained with an immunoperoxidase technique using rabbit anti-human fibrinogen antiserum, microthrombi were seen frequently. Large microthrombi were more common in patients who had died within less than 24 hours, suggesting a relationship to death or to less time for lysis. In order of frequency, the brain/spinal cord, liver, lungs, kidneys, and pancreas were most commonly affected, and the liver, pituitary gland, pancreas, thymus, brain/spinal cord, large intestine, kidneys, and lungs had the greatest density of microthrombi. Pulmonary dysfunction had been a frequent problem in these patients, which may have been related to the high incidence of microthrombi and bleeding found in the lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation Tests↗
PubMed1983

Purification and characterization of an enkephalin aminopeptidase from rat brain membranes.

A membrane-bound aminopeptidase was purified from rat brain, and its activity was assayed by high-pressure liquid chromatography with Met-enkephalin as the substrate. The enzyme was extracted with 1% Triton X-100 and purified by chromatography, successively on DEAE-Sepharose CL-6B, Bio-Gel HTP, and Sephadex G-200 columns. The overall purification was about 1200-fold, with 25% yield. The purified enzyme showed one band on disc gel electrophoresis and two bands on sodium dodecyl sulfate electrophoresis with molecular weights of 62 000 and 66 000. The aminopeptidase has a pH optimum of 7.0, a Km of 0.28 mM, and a Vmax of 45 mumol (mg of protein)-1 min-1 for Met-enkephalin. It releases tyrosine from Met-enkephalin, but it does not split the byproduct. It does not hydrolyze gamma- or beta-endorphin, or dynorphin, but it does hydrolyze neutral and basic aminoacyl beta-naphthylamides. The enzyme is inhibited by the aminopeptidase inhibitors amastatin, bestatin, and bestatin-Gly. Its properties, such as its subcellular localization, substrate specificity, pH optimum, and molecular weight, distinguish it from leucine aminopeptidase, aminopeptidase A, aminopeptidase B, aminopeptidase M, and the soluble aminopeptidase for enkephalin degradation.

Aminopeptidases↗
PubMed1983

Short-lived effect of (Des-Tyr)-gamma-endorphin in schizophrenia.

Des-tyrosine-gamma-endorphin (DT gamma E) has been reported to alleviate symptoms of schizophrenia. Attempting to replicate those reports, we administered 1 mg of DT gamma E, i.m., for 8 consecutive days to nine patients meeting the DSM-III criteria for schizophrenia. Patients in this double-blind, crossover, and placebo-controlled study showed a statistically significant, but clinically modest improvement. The improvement was detectable during the first several days of the DT gamma E treatment; the symptoms then returned to baseline level in spite of continued doses of DT gamma E. Testing the metabolism of DT gamma E in the patients' plasma, we found a high rate of formation and of degradation, but the metabolic rates were not related to clinical symptoms.

Adult↗
PubMed1983

Effect of bestatin analogues and other compounds on enkephalin hydrolysis by an aminopeptidase from the mesophiles pseudomonas sp ATCC 11299A and chromobacterium violaceum ATCC 12540.

In our studies on newly synthesized compounds for their potential analgesic effect, we decided for purposes of convenience and economy to investigate non-mammalian sources for the presence of enkephalin degrading enzymes. An aminopeptidase that catalyzes the hydrolysis of the tyrosylglycyl bond of leucine- and methionine enkephalin was purified from the mesophiles Pseudomonas sp ATCC 11299a (Ps) and Chromobacterium violaceum ATCC 12540 (Cv). Each preparation also hydrolyzed to varying extents neutral dipeptides, tripeptides, tetrapeptides and amino acid beta-naphthylamides. The Ps enzyme has a pH optimum of 6.8, Km of 80 microM and a Vmax of 6.7 nmoles/min/mg of protein. The Cv enzyme has a pH optimum of 6.8-7.2, Km of 111 microM and a Vmax of 42 nmoles/min/mg of protein. Both are sulfhydryl enzymes since they are activated by dithiothreitol (DTT) and inactivated by p-chloro- and p-hydroxymercuribenzoate. They are not glycoproteins since they pass unretained through a Con A-Sepharose column. The activity lost by dialysis against EDTA can be restored, wholly or in part, by Co+2, Mg+2, Mn+2 and Ni+2; ions exerting an inhibitory effect were A1+3, Cd+2, Cu+2, Hg+2 and Zn+2. From a range of organic compounds, the greatest inhibition was elicited by the microbial peptides amastatin and bestatin. Several dipeptide analogues of bestatin, synthesized from DL-threo-2-amino-3-hydroxy-3-phenylpropanoic acid (AHPP) as the N-terminal residue in order to define the stereospecific requirements of the alpha, beta-functional groups for maximal activity, were not as active as the parent compound.

Aminopeptidases↗
PubMed1981

The effect of naloxone on enkephalin catabolism.

Naloxone strongly inhibited the breakdown of Met- and Leu-enkephalin when the substrate was incubated with brain homogenate, supernatant, or partially purified soluble aminopeptidase, but it had no effect on the mitochondrial fraction. Arylamidase was also inhibited by naloxone. The inhibitory effect of naloxone on the soluble aminopeptidase was in a linear relationship with concentration in the range of 8-500 microM. The KI for Met-enkephalin is 0.6 mM and for Leu-enkephalin is 2.0 mM. When the naloxone was administered intraperitoneally to the mice, its effects were somewhat different from its effects in vitro. It inhibited the brain catabolism of Met-enkephalin but not of Leu-enkephalin or Tyr-beta NA in vitro. In vivo, acute morphine in mice decreased the Met-enkephalin hydrolysis but increased the Leu-enkephalin hydrolysis. Chronic morphine (by morphine pellet implantation) increased the breakdown rate of enkephalin and of Tyr-beta NA. Naloxone (1 mg/kg) could not reverse the effects of morphine, although abstinence syndrome and stereotypical jumping were precipitated. Naloxone decreased the Leu-enkephalin level in the control mice but did not affect it in the addicted mice.

Aminopeptidases↗
PubMed1980

Separation of alkylaminonaphthylenesulfonyl peptides and amin acids by high-performance liquid chromatography. Methods for measuring melanotropin inhibiting factor breakdown.

N,N-Dimethyl diethyl, dipropyl, dibutyl, and N-monoisopropylaminoaphthylenesulfonyl derivatives of melanotropin inhibiting factor (MIF) and its metabolites were prepared, and their chromatographic behavior was investigated with thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), using five solvent systems on polyamide layers and ten solvent systems on muBondapak C18 and muBondapak phenyl columns. A mixture of MIF and its metabolites derivatized with Dns chloride was adequately resolved by two-dimensional chromatography on polyamide layer with solvent systems, formic acid-water (3:97) and benzene-acetic acid (9:1). Bns-MIF and its metabolites were separated with muBondapak C18 column with the solvent system acetonitrile-0.01 M sodium sulphate buffer, pH 7 (50:50). They were separated into five groups: Gly and Bns acid; Pro-Leu, Leu-Gly and Leu; Pro; Gly-NH2; and MIF. The alkylaminonaphthylenesulfonyl derivates had strong fluorescence, which permitted their detection at the level of 10(-11) to 10(-9) mol. Dns-MIF and its derivatives had the lowest detectable amounts. HPLC with the aid of the Dns derivation is reliable and fast, and is the preferable method for study of neuropeptide breakdown.

Alkanesulfonates↗
PubMed1980

Enkephalin degradation stimulated by captopril.

Changes in the rates of degradation of Met- and Leu-enkephalin by brain aminopeptidase were measured by UV absorption after high-pressure liquid chromatography. The cleavage of enkephalin paralleled the generation of tyrosine. Captopril (SQ 14,225) stimulated enzyme activity, to a greater extent with Met- than with Leu-enkephalin. Pro-His-Pro-NH2, histidine, and histamine stimulated enkephalin aminopeptidase approximately twice as much as captopril. The sulfhydryl group of captopril was not the only factor in its effect. The addition of captopril did not change the pH optimum, and it stimulated enkephalin degradation between 25 and 50 degrees C.

Aminopeptidases↗
PubMed1980

Degradation of melanotropin inhibiting factor by brain.

Degradation of melanotropin inhibiting factor (MIF) was measured by fluorometry, using pareptide as an internal standard, following the separation of the dansyl derivatives of MIF and its metabolites by HPLc. MIF was not split by carboxypeptidases A and B, prolidase, or pyroglutamate aminopeptidase. It was hydrolyzed by leucine aminopeptidase, aminopeptidase M, and carboxypeptidase Y. Rat brain hydrolyzed 159 nmol of MIF per mg of protein per h; the activity was linear with enzyme concentration. Hydrolysis start from the N-terminal end, as shown by the appearance of proline as the first metabolite of the MIF degradation, followed by leucine, glycinamide, leucylglycine, and glycine. Activity in the rat brain regions was in the order striatum, medulla oblongata > cortex, hippocampus, midbrain > hypothalamus, cerebellum, and pituitary. The enzyme was mostly in the supernatant, with significant amounts in the myelin and synaptosomal fractions. MIF aminopeptidase could be separated from carboxypeptidase by centrifugation at 30,000 x g for 20 min and precipitation with 45--75% (NH4)2SO4. It showed pH optima in the alkaline range (8.25 and 8.75) and was inhibited by EDTA, EGTA, SQ 14,225, puromycin, bacitracin, and bestatin.

Aminopeptidases↗
PubMed1980

Activation and inhibition of cerebral prolidase.

Purified of prolidase from calf brain (acetone and [NH4]2SO4 fractionation) separated this enzyme from proteases, leucine aminopeptidase, master dipeptidase, and Gly-Gly dipeptidase. Prolidase was tested with peptidase and protease inhibitors, used at higher levels (35 times or more) than their ID50 for peptidases and proteases. Bacitracin, leupeptin, chymostatin, and antipain had no effect; pepstatin slightly increased activity, and only bestatin was inhibitory. Antibiotics that affect protein synthesis did not inhibit prolidase. Peptides with proline at the NH2 end activated prolidase, whereas those with proline at the carboxyl end inhibited it. Di, tri, and tetra-Pro peptides increased prolidase activity. Thyrotropin-releasing hormone had no effect on prolidase; its analog Pro-His-Pro-NH2 gave high activation and decreased the Km from 20 mM to 1.54 mM. Pro-peptide inhibitors and activators were not themselves split by prolidase. The results indicate influences of specific peptides, for both inhibition and activation, on prolidase activity.

Animals↗