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Biomedical subjects

W K Liu

Publications and source records attributed to W K Liu.

At least 91 records · Page 5Linked to original sources
PubMed1988

A reevaluation of the amino acid sequence of human follitropin beta-subunit.

A collaborative study from two laboratories has been undertaken to re-evaluate the human follitropin beta-subunit sequence (hFSH beta), since areas of uncertainty remain in the wake of two earlier reports. The first report was by Shome and Parlow (1974). The second, by Saxena and Rathnam (1976), proposed revisions for sequence not definitively placed in the first study, as well as some differences in other placements. We have re-examined the sequence of the hFSH beta with more recent methodology. This has led to revision of certain areas of the sequence and resolution of differences between the two earlier proposals. Specifically, an -Ile-Ser- is established at 21-22, Asp at 41, Arg at 44, Lys at 46, and Glu at 111. These were areas of disagreement in the earlier proposals. A definitive placement of the residues around tryptophan-27 has now been obtained by three laboratories. C-terminal heterogeneity was observed with subunits ending at residue 107, 109, or 111. N-terminal heterogeneity has been observed in all preparations examined to date. A significant population of molecules with a proteolytic nick between residues 38-39 is noted. This is very likely an artifact of the collection and processing. The preparations examined in the present studies showed no evidence of residues 112-118 proposed by Saxena and Rathnam.

Amino Acid Sequence↗
PubMed1988

Ultrastructural changes of tracheal epithelium and alveolar macrophages of rats exposed to mosquito coil smoke.

The volatile organic compounds of mosquito coil smoke were analysed by a combination of gas chromatography and mass spectrometry. 67 volatile organic compounds were detected and 46, including allethrin, phenol, benzene, toluene, xylene, etc. could be identified. Allethrin, a common name for (+/-)-3-allyl-2-methyl-4-oxocyclopent-2-enyl (+/-)-cis,trans-chrysanthemate, is a synthetic pyrethroid, which is used as an insecticide or repellent in subtropical countries. The vapors also contain other aromatic and aliphatic hydrocarbons which are combustion products of other mosquito coil constituents, including wood dust, coconut flour and other fillers and dyes. An exposure to the mosquito coil smoke for 60 days (8 h per day, 6 days per week) resulted in a focal deciliation of the tracheal epithelium, metaplasia of epithelial cells, and morphological alterations of the alveolar macrophages of exposed rats.

Animals↗
PubMed1988

Identification and subcellular localization of proteins that are rapidly phosphorylated in tyrosine in response to colony-stimulating factor 1.

To investigate growth factor-mediated signal transduction, we have studied phosphorylation events that take place within seconds of the binding of colony-stimulating factor 1 (CSF-1) to its cell-surface receptor. CSF-1 stimulated rapid tyrosine phosphorylation of cellular proteins in murine BAC1.2F5 macrophages at 37 degrees C and 4 degrees C. The pattern of CSF-1-stimulated tyrosine phosphorylation of at least 15 different proteins at both temperatures was similar and unchanged by treatment of the lysate with reducing agent. With the exception of the 185-kDa CSF-1 receptor, a 260-kDa protein and a 133-kDa protein, the proteins were predominantly cytoplasmic. At 37 degrees C, all the proteins were phosphorylated within 30 sec of addition of growth factor. At 4 degrees C, CSF-1 receptor sites were saturated after 2 min of incubation in the presence of high concentrations of CSF-1 and differences in the order of appearance of phosphorylated proteins were observed: 185 kDa (CSF-1 receptor) (by 2 min); 99 kDa (by 4 min); 125 kDa (by 10 min); 61 kDa (by 30 min); and 260 kDa, 84 kDa, and 41 kDa (by 180 min). In addition to stimulating the phosphorylation of these proteins in tyrosine, CSF-1 caused dephosphorylation of phosphorylated serine residues on the receptor. As neither CSF-1 nor its receptor is internalized at 4 degrees C, analysis of these early reactions and the phosphotyrosine-containing proteins in intact cells under these conditions should lead to an understanding of the early events in growth factor receptor-mediated signal transduction.

Animals↗
PubMed1987

Structural studies on equine glycoprotein hormones. Amino acid sequence of equine lutropin beta-subunit.

The amino acid sequence was determined for equine lutropin beta (eLH beta). Large fragments were derived from reduced, carboxymethylated eLH beta by digestion with Staphylococcus aureus V8 protease, by cyanogen bromide cleavage, and by cleavage of acid-labile Asp-Pro bonds. The fragments were purified by gel filtration and high performance liquid chromatography (HPLC). The fragments were sequenced by automated Edman degradation to establish the primary structure of eLH beta. Some peptides were further digested with chymotrypsin and the resulting peptides purified by HPLC. In addition to sequencing by automated Edman degradation, these were also sequenced by the complementary 5-dimethylaminonaphthalene-1-sulfonyl-Edman procedure which enabled us to directly identify glycosylated amino acids. The eLH beta subunit is a glycoprotein of 149 amino acids containing both N- and O-linked oligosaccharides. It possesses a COOH-terminal extension similar to that seen in human chorionic gonadotropin. Carboxypeptidase Y digestions suggest that the COOH terminus is blocked by glycosylation. Interestingly, the amino acid sequence of eLH beta is identical to that of equine chorionic gonadotropin beta (Sugino, H., Bousfield, G. R., Moore, W. T., and Ward, D. N. (1987)J. Biol. Chem. 262, 8603-8609).

Amino Acid Sequence↗
PubMed1987

Cytotoxicity of airborne particles from roadside urban gardens.

Airborne particles were collected in two small urban gardens along the roads with heavy traffic in Hong Kong. The chemical and physical properties of the particles of a diameter about 1 micron were analysed by a scanning electron microscope incorporated with a x-ray energy dispersive microanalyzer and an atomic absorption spectrophotometer. The cytotoxicities of particles were compared using an in vitro alveolar macrophage culture assay. It was found that both particles significantly increase (p less than 0.05) the release of lactate dehydrogenase and acid phosphatase into the medium in addition to damage the surface morphology and intracellular structures of the macrophages to a variable extent after exposure to the particles.

Air Pollutants↗
PubMed1987

Heavy metal pollution in roadside urban parks and gardens in Hong Kong.

An ecological survey was conducted on metal contamination (including Cd, Pb, Ni, Zn, Cu, Mn and Fe) of vegetation (leaf of Bauhina variegata), surface soil (0-1 cm) and dust (from road curbs) collected at 13 urban parks near busy roads (with heavy traffic volume) in Hong Kong. Samples from roadside parks had significantly higher metal contents than the control site (away from automobile traffic). A close correlation was found between traffic volume and metal contents of leaf, soil and dust. Washing of leaf samples reduced the levels of Cu, Mn, Zn and Fe contamination and suggested that the source of heavy metal pollution was mainly due to aerial deposition from motor vehicles.

Environmental Pollution↗
PubMed1987

Toxic effects of mosquito coil (a mosquito repellent) smoke on rats. I. Properties of the mosquito coil and its smoke.

The physical and chemical properties of the mosquito coil, a commonly used mosquito repellent in Asia and South America, were analysed. The smoke emitted from the burning mosquito coil consists of submicron particles (diameter less than 1 micron) coated with a considerable amount of heavy metals, allethrin and a wide range of organic vapors, such as phenol and o-cresol. Therefore, a lengthy exposure to this smoke will cause adverse effects on the consumers.

Allethrins↗
PubMed1987

Toxic effects of mosquito coil (a mosquito repellent) smoke on rats. II. Morphological changes of the respiratory system.

A group of 20 female albino rats was exposed to mosquito coil smoke, 8 h a day, 6 days per week, for 60 days. An additional group receiving air exposure served as control. The smoke-exposed animals had a lower body weight than the controls. Smoke-induced histopathological lesions, including an inflammation of the tracheal epithelium, atelectasis of the lung parenchyma, emphysema, increase of alveolar macrophages in the alveolar space and perivascular infiltration of polymorphonuclear cells were observed in the experimental rats. An elevation of enzyme activities of lactate dehydrogenase, glutamate pyruvate transaminase, glutamate oxoacetate transaminase and acid phosphatase were found in the serum of the smoke-exposed rats indicating the enzymes were released from the damaged tissues into the blood stream.

Animals↗
PubMed1987

Fly ash hemolysis as related to its alkalinity.

Fly ash particles were collected from the precipitator of a power plant in Hong Kong and the hemolytic activity of the particles of the respirable range (smaller than 10 micron) was studied using a rat red blood cell assay system. It was revealed that coal-fired fly ash had a high hemolytic activity which was dose independent. The hemolysate changed from red to brownish-green. Chemical analyses, including scanning electron microscopy incorporated with energy dispersive X-ray microanalysis, inductively coupled plasma spectrophotometry, and X-ray power diffractometry, showed that a considerable amount of calcium salt coated the surface of the particles. The high alkalinity of the calcium salt initially damaged the red blood cell membrane and then destroyed the hemoglobin molecules released from the damaged cells. This phenomenon only caused a discrepancy if the amount of hemoglobin which remained in the incubation medium was taken into account for the measurement of hemolytic activity of fly ash particles.

Aerosols↗
PubMed1987

Beta-microseminoprotein (beta-MSP) is not an inhibin.

Beta-microseminoprotein (beta-MSP), a sperm-coating antigen isolated from human seminal plasma, has apparent structural identity with "beta-inhibin" isolated from the same source. Publication of the amino acid sequence of beta-MSP revealed a greater than 96% homology with "beta-inhibin," with only a proline-threonine substitution at positions 39 and 40, and the omission of a glycine at position 93. Due to the nearly identical sequences of "beta-inhibin" and beta-MSP, we examined the ability of beta-MSP and its tryptic peptides to inhibit basal follicle-stimulating hormone (FSH) secretion from rat pituitary cells in culture, the inhibin bioassay. Whole pituitaries collected from 250- to 300-g male rats were dispersed enzymatically and plated onto 24-well culture dishes for 3 days. beta-MSP and its tryptic peptides were dissolved in cell culture medium, applied to the pituitary monolayer cell cultures, and incubated for an additional 3 days. FSH levels in the medium were determined by radioimmunoassay. A partially purified preparation of inhibin and our in-house inhibin standard, both prepared from porcine follicular fluid (pFFl), were included in the same assay. Whereas the partially purified inhibin from pFFl showed a dose-dependent inhibition of FSH secretion, with a 50% inhibitory dose (ID50) of 50 ng, which paralleled that of the standard, beta-MSP and its tryptic peptides failed to depress FSH levels in the medium at any of the doses tested (10-10,000 ng/ml). We conclude that beta-MSP is not an inhibin under our assay conditions.

Animals↗
PubMed1986

Ultrastructural changes in gills of Sarotherodon mossambicus treated with chicken manure.

Sarotherodon mossambicus were fed a chicken manure (60%) supplementary diet for 4 weeks under laboratory conditions, and significantly higher (P less than 0.05) concentrations of Mn, Fe, Cu, Pb, and Zn were obtained in the gills of the treated fish. Ultrastructural changes including separation of the epithelium from the pillar cell system and subsequently increasing the blood-water barrier, necrosis of lamellar cells, collapse of lamellar blood spaces, and hyperplasia of interlamellar cells were found in the lamellae of the gills of the treated fish.

Administration, Oral↗
PubMed1986

Comparison of hemolytic activities of coal fly ash and its soluble and insoluble fractions.

Coal fly ash of a particle diameter smaller than 10 micron was collected from the precipitator of a power plant in Hong Kong. Comparison of hemolytic activities between fly ash and free silica showed that fly ash had a lower biological effect than free silica. The hemolytic activities of the soluble and insoluble fractions of fly ash were further compared by two methods: total hemoglobin method and cyanmethemoglobin method. An analysis of results showed significant differences for fly ash and its soluble fraction between methods (P less than 0.05 and P less than 0.01, respectively). Fly ash, which contained a silicate level similar to its insoluble fraction, had a hemolytic activity higher than the summation of both its soluble and insoluble fractions. This indicates that the hemolytic activity was independent of the silicate content in the fly ash samples.

Animals↗
PubMed1986

Inhibin fractionation: a comparison of human and porcine follicular fluid, with particular reference to protease activation.

A novel treatment has been devised in our studies of the purification of inhibin from porcine and human follicular fluids (pFFl and hFFl, respectively). Both pFFl and hFFl were precipitated with acetone and extracted with acetic acid to provide a starting material for subsequent gel filtration and reverse-phase high-pressure liquid chromatography (HPLC). Inhibin from pFFl was purified 4200-fold using this methodology. Inhibin from hFFl could not be purified to this degree since recoveries were relatively poorer than for pFFl and yielded too little material for the HPLC step. In our fractionation scheme, protease activities were assessed with a gel electrophoresis assay system. Protease activity at approximately 90 kDa was observed in raw pFFl. When inhibin was fractionated by extraction or chromatography, additional bands of protease activity appeared near 150 kDa, 66 kDa and at less than 45 kDa. In raw hFFl, only faint bands of protease activity were observed at approximately 90 kDa and at 85-90 kDa. Upon further fractionation of hFFl, protease activity was reduced below the ability of this method to detect it. Our results suggest that, with our treatment of follicular fluid, protease activity is present in pFFl and additional protease activity appears upon fractionation; proteases, although present, do not eliminate the possibility of obtaining a highly purified inhibin preparation with acceptable recoveries of inhibin activity during purification; and although protease activity could be reduced or eliminated from hFFl, the low yields of inhibin activity from this method mandate a different approach to purification of inhibin from hFFl.

Amino Acid Sequence↗
PubMed1985

Gonadal development and fertility of mice treated prenatally with cadmium during the early organogenesis stages.

Gonadal development was studied in mouse embryos that were exposed to cadmium during the early organogenesis stages. At 13.5 days, both the male and the female embryos had small genital ridges. Fewer primordial germ cells were found in the male embryos. In both sexes, many primordial germ cells were left outside the genital ridges, presumably as a result of retarded cell migration. In 16.5-day embryos, the size of the testes and ovaries and the number of differentiating germ cells were reduced. Many germ cells degenerated during the differentiation to spermatogonia and meiotic oocytes. The perturbed gonadal development was less likely to be caused primarily by a defective hypothalamopituitary axis but was more a part of the general cadmium-induced damage. The fertility of the male offspring was impaired by the prenatal cadmium insult, but the females were apparently fertile. The epididymal spermatozoa of the cadmium-affected offspring showed a lower fertilizing capacity in vitro. The impaired fertility of the cadmium-affected mice was the result of poor gonadal growth, paucity of germ cells, and defective maturation of the gametes.

Abnormalities, Drug-Induced↗
PubMed1985

Hybrids from equine LH: alpha enhances, beta diminishes activity.

LH hybrids were prepared by combining eLH alpha and eLH beta with the corresponding subunits of oLH, pLH and hCG. Recombinants were isolated by gel filtration and assessed by SDS-polyacrylamide gel electrophoresis under both dissociating and non-dissociating conditions. All combinations of subunits produced hybrid LH molecules. Hybrids prepared by combining eLH beta with oLH alpha, pLH alpha or hCG alpha were very inactive in rat radioligand and Leydig cell in vitro bioassays. Hybrids prepared with eLH alpha were very active in both assays. The greatest potentiating activity was observed when eLH alpha was combined with pLH beta. The resulting hybrid was 49 times as active as pLH in stimulating steroidogenesis by Leydig cells.

Animals↗
PubMed1985

Properties and toxicity of airborne wood dust in wood-working establishments.

The total suspended dust levels, particle shape and size distributions and metal concentrations (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) of wood dust in the breathing zone of 3 small wood-working establishments were monitored. In vitro culture assay indicated that the mortality of alveolar macrophage was related to the metal content of dust collected from these 3 workplaces.

Air Pollutants, Occupational↗
PubMed1985

Priming procedure and hormone preparations influence rat granulosa cell response.

The FSH activity in equine (e) FSH, eLH, eCG, and ovine LH were examined and compared to that in the standard reference preparation NIH FSH-S13 by three types of assay: the FSH radioreceptor assay with rat testicular homogenate and the stimulation of plasminogen activator production and steroidogenic activity in granulosa cells from diethylstilbestrol (DES)- or eCG-primed donor rats. The difference in the two types of granulosa cells was that the eCG-primed cells have already acquired significant aromatase activity. With the exception of oLH, which showed very little FSH activity (approximately 0.03-0.08 X NIH FSH-S13) throughout the three assays, the equine gonadotropins exhibited great variations in activity with respect to each assay. eFSH, the most active molecule in these assays, had an activity of 44 X NIH FSH-S13 in the receptor binding assay, 8.75 X NIH FSH-S13 in plasminogen activator production, and 4-5 X NIH FSH-S13 in steroid production when assayed in the DES-primed granulosa cells. In the eCG-primed cells, eFSH showed an activity of 4.2 X NIH FSH-S13 in plasminogen activator production and 8.2 X NIH FSH-S13 in progesterone production. eLH had an activity of 10 X NIH FSH-S13 in FSH radioreceptor assay, but showed very little activity and behaved like oLH in stimulation of the cellular responses of DES-primed granulosa cells. However, when eLH was assayed in the eCG-primed cells, it did show stimulating activity with respect to the production of plasminogen activator and progesterone; however, the dose-response curves were not parallel to those of eFSH and eCG. eCG had much less FSH receptor-binding activity (0.29 X NIH FSH-S13) than eLH. It behaved like a LH molecule in DES-primed granulosa cells, but did show activity (approximately 1 X NIH FSH-S13) in stimulating the production of plasminogen activator and progesterone in eCG-primed granulosa cells. From these results, we conclude that under our culture conditions, neither eLH nor eCG was active in the DES-primed granulosa cells, but both were active in the eCG-primed cells, and that the choice of assay conditions and reference standards is very important. Different types of assay may give rise to completely different comparisons for the same molecules. The equine gonadotropins provide a particularly dramatic example of such differences.

Animals↗