PubMed Health⌕ Search

Biomedical subjects

K S Hui

Publications and source records attributed to K S Hui.

49 records · Page 3Linked to original sources
PubMed1979

Mass spectrometric identification of Cu, Zn, Fe, Co, Mn, Mg, and Pb in mammalian brain.

Combining the techniques of thin-layer chromatography (TLC) and mass spectrometry, we unambiguously identified the trace metals Cu, Zn, Fe, Pb, Mn, Co, and Mg in the brain of a female human who had no evidence of any pathologic disease in the central nervous system, and in brains from mouse, rat, guinea pig, and rabbit. These trace metals were also found in anatomic regions of human brain: cortex (gray), cortex (white), caudate nucleus, putamen, hippocampus, and thalamus, and in anatomic regions of rat brain: hypothalamus, cerebellum, stem striatum, and "the rest." The metals were characterized from the color and Rf values of their tetraphenylporphyrin chelates on TLC and from the mass and pattern of molecule ion cluster of the mass spectrum. The unexpected presence of lead in the brain is discussed.

Animals↗
PubMed1979

Purification and covalent coupling of calf brain prolidase.

We have investigated methods of stabilizing prolidase by chemical modification and covalent coupling to various supports, for use in protein hydrolysis and possible use in enzyme replacement therapy. Purified acetone powder of calf brain prolidase was further purified by gel filtration on Sephadex G-200 and chromatography on DEAE-Sephadex A25. Polyacrylamide gel electrophoresis showed that the number of bands was reduced from 11 to 2. Since yields were low, the purified (NH4)2SO4 fraction was used in all experiments. Thiolation of the enzyme reduced the amount of protein coupled to AH- or CH-Sepharose 4B. Activities were highest when the protein was linked through its carboxyl groups. The coupled enzyme showed much greater thermal stability than its free counterpart. Of the bound preparations, the thiolated was less stable than the untreated. Untreated and thiolated enzymes bound to either matrix showed higher activity at low pH and less at high pH than the free material. Thiolation shifted the pH maximum from 6.8 to 7.5. The free thiolated enzyme and that bound to activated SH-Sepharose 4B showed greater thermal stability and a broader pH range of optimal activity than the bound untreated enzyme. These results show that prolidase can be immobilized by coupling to an insoluble matrix through various types of covalent bonds with retention of activity and increased stability.

Animals↗
PubMed1978

Prolidase activity in rat brain; developmental, regional and subcellular distribution.

We determined the regional and subcellular distribution of prolidase in rat brain and its changes with development. The most rapid changes in enzyme activity occurred perinatally, with a maximum level of activity 2 days before birth and a minimum 1 day after birth. Of the 7 regions examined, cerebellum had the highest enzyme level, followed by medulla. The lowest levels were found in the hypothalamus in the adult and in the midbrain in the young. Polidase was mainly soluble; over 55% was recovered in the S2fraction, and the rest was released from the particulate fractions by hypotonic shock. Brains of male rats contained a slightly higher level of the enzyme.

Animals↗
PubMed1977

Covalent coupling of calf brain prolidase.

Calf brain prolidase covalently bound to CNBr-Sepharose 4B, retained about 32% of the activity of the uncoupled enzyme. The free enzyme showed slightly greater stability than the bound preparation when stored at 20 degrees C or at 0 degrees C. However, in either case the free and bound enzymes were more stable at the lower temperature. Greater thermal stability was shown by the free enzyme than by the bound preparation over a temperature range of 25 degrees C-60 degrees C. The free and bound prolidase, with and without Mn+2, had maximal activity at pH 4.0. Although the bound enzyme showed a single maximum, the free preparation exhibited three pH maxima of 4.0, 9.0, and 6.5, in decreasing order of activity. The ions Ag+, Cu+, Hg+2, and Zn+2 were strongly inhibitory on the free enzyme, whereas inhibition of the bound enzyme, with the exception of Zn+2 , was less. Unlike the coupled enzyme, a stimulatory effect was obtained on the free preparation with Co+3, Mg+2, and Mn+2. Various other compounds were studied and their effects were noted.

Animals↗
PubMed1976

Qualitative and quantitative mass spectrometry of some biologically important trace metals as their tetraphenylporphyrin chelates.

The use of the mass spectrometric integrated ion current technique for the quantitative analysis of some trace metals at their tetraphenylporphyrin chelates is described. The linearity of the calibration curves and the sensitivity of the technique are improved by employing deuterated tetraphenylporphyrin chelates as loading agents. Femtomole quantities of the chelates may be detected. The use of deuterated tetraphynylporphyrin chelates as internal standards overcomes the problems of losses occurring during chromatographic separation and by thermal decomposition in the mass spectrometer.

Chelating Agents↗
PubMed1975

The separation by thin-layer chromatography of trace metals as their tetraphenylporphyrin chelates.

The tetraphenylporphyrin chelates of iron, cobalt, manganese, nickel, zinc, copper, rhodium lead, cadmium and mercury were prepared and their chromatographic behaviour investigated using four different adsorbents and eleven different solvent systems. Mixtures of lead, cadmium and mercury chelates exhibited isographic behaviour in all conditions; mixtures of the other metal chelates were adequately resolved on silica (MN Polygram Sil SHR) by the solvent system light petroleum (b.p. 80-100 degrees)-toluene-acetic acid-water (66:33:85:15, v/v, upper phase). The intense colours of the chelates permit their visual detection at levels of about 10(-10) moles; using the integrated ion-current mass spectrometric procedure, as little as 10(-14) moles of metal could be detected and assessed.

Adsorption↗
PubMed1975

An improved implantation pellet for rapid induction of morphine dependence in mice.

A new type of morphine implantation pellet for the rapid induction of physical dependence in mice can be prepared by absorbing 7 mg morphine sulphate onto molecular sieves Type 4A (BDH). The small cylindrical pellets can be implanted subcutaneously without trauma and the need for anaesthesia, and are easily removed at any time from the animals. The peak of physical dependence is reached 24 h after implantation, and mortality is negligible. Withdrawal symptoms can be precipitated by intraperitoneal injection of naloxone, without removal of the pellet, and up to 70% of a group of mice show the characteristic urge to jump off a raised platform. This type of pellet has definite advantages over some other sustained-release preparations used in studies on morphine addiction in small animals.

Animals↗
PubMedDate not supplied

Enkephalin-containing polypeptides are potent inhibitors of enkephalin degradation.

Enkephalin-containing polypeptides derived from pro-enkephalin A, pro-enkephalin B, or pro-opiomelanocortin were inhibitors of enkephalin degradation by aminoenkephalinases purified from cytosol or membranes. Of the peptides, Argo-Met-enkephalin was the most potent inhibitor for the aminoenkephalinases, with an IC50 of about 0.6 microM, it was more effective than bestatin (IC50 = 0.8-1.0 microM). This inhibition was partly due to substrate competition. Argo-Met-enkephalin was hydrolyzed by aminoenkephalinases to form Arg, Tyr, and Gly-Gly-Phe-Met in a substrate-inhibited manner. The hexapeptide also inhibited the breakdown of Arg- and Tyr-beta-naphthylamide by the membrane aminoenkephalinase. Since Argo-Met-enkephalin did not inhibit leucine aminopeptidase, it was a more selective inhibitor than bestatin of Met-enkephalin breakdown by aminopeptidases. Argo-Met-enkephalin inhibited enkephalin breakdown by synaptosomal plasma membranes but not by brain slices. Our data suggest that in addition to their possible role as opioids, the enkephalin-containing polypeptides may be regulators of enkephalin levels.

Aminopeptidases↗
PubMedDate not supplied

Changes in puromycin-sensitive aminopeptidases in postmortem schizophrenic brain regions.

We studied the distribution of puromycin-sensitive aminopeptidase (PSA) in well-defined human brain ares by Western immunoblot in an attempt to examine its possible role in schizophrenia. The schizophrenic brains were from suicide victims (n = 13) of either sex, with an age range of 30-60 yr (average 45). The controls were mostly victims of myocardial infarction (n = 12), of either sex and between 32 and 56 yr old (average 44). The brain regions were obtained within 48 h after death. After ultracentrifugation the PSA was quantified by Western blot analysis using a PSA antiserum. The distribution of the two most abundant antigens, MW 100 kDa (PSA-100) and 170 kDA (PSA-170), were compared. PSA-100 had peptidase activity, PSA-170 did not. PSA-100 was found in all of the region studied. In the control brain areas prefrontal cingulate and frontal cortices, thalamus, hippocampus, hypothalamus and outer globus pallidus contained significantly more PSA-100 than the corresponding areas from schizophrenic brain. PSA-170 was mostly found only in areas of schizophrenic brains. In three control brains, in one area of each, it could be detected, but the level in each of these regions was less than 30% of that in the corresponding schizophrenic area. PSA-170 was found in all the schizophrenic brains, in 20 of the 35 regions we studied, with parahippocampal cortex the highest (134 ng/g wet tissue) and frontal inferior cortex the lowest (9.3 ng/g wet tissue). It was not detectable in cerebral or cerebellar white matter. Our data show that the amounts and distribution of PSA-170, a protein of unknown function, is restricted mostly to schizophrenic brain areas. The difference is not due either to neuroleptic treatment of the patient or to the postmortem proteolysis of the brain samples.

Adult↗