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Biomedical subjects

W C Chang

Publications and source records attributed to W C Chang.

At least 253 records · Page 14Linked to original sources
PubMed1986

Characterization of lens crystallins and their mRNA from the carp lenses.

Crystallins from carp eye lenses have been isolated and characterized by gel permeation chromatography, SDS-gel electrophoresis, immunodiffusion and amino acid analysis. gamma-Crystallin is the most abundant class of crystallins and constitutes over 55% of the total lens cytoplasmic proteins. It is immunologically distinct from the alpha- and beta-crystallins isolated from the same lens and its antiserum shows a very weak cross-reaction to total pig lens antigens. Comparison of the amino acid compositions of carp gamma-crystallin with those of bovine gamma-II, haddock gamma- and squid crystallins indicates that gamma-crystallin from the carp is very closely related to that of the haddock, and probably also related to the invertebrate squid crystallin. In vitro translation of total mRNAs isolated from carp lenses confirms the predominant existence of gamma-crystallin. The genomic characterization of carp crystallin genes should provide some insight into the mechanism of crystallin evolution in general.

Amino Acids↗
PubMed1986

Natural killer-cell immunodeficiency in patients with chronic myelogenous leukemia. I. Analysis of the defect using the monoclonal antibodies HNK-1 (LEU-7) and B73.1.

Quantitative evaluation of natural killer (NK) cells using the HNK-1 (Leu-7) and B73.1 monoclonal antibodies (MAbs) was correlated with NK activity in 13 patients with chronic myelogenous leukemia (CML) and compared to normal donor controls. A consistent observation was the presence of normal absolute numbers of B73.1+ lymphocytes as well as normal to increased absolute numbers of HNK-1+ lymphoid cells in the peripheral blood of chronic-phase CML patients. Despite normal to increased numbers of B73.1+ and HNK-1+ lymphoid cells, these patients consistently demonstrated a significant impairment of lymphocyte-mediated NK activity in their peripheral blood. Further experiments demonstrated that chronic-phase CML patients, in contrast to normal controls, had significantly increased percentages of HNK-1+, E+ and B73.1+, E+ lymphoid cells and significantly decreased percentages of HNK-1+, E- and B73.1, E- lymphoid cells, which resulted in significant reversals of the HNK-1+, E+ to HNK-1+, E- and B73.1+, E+ to B73.1+, E- lymphoid cell ratios. (HNK-1+ [E+/E-] greater than B73.1+ [E+/E-]). Furthermore, as compared to normals, both FACS-sorted HNK-1+ and B73.1+ lymphoid cells from the E+ fraction of CML patients were consistently defective in NK activity, and could not be substantially augmented with alpha-interferon preparations. Although markedly defective in their ability to lyse K-562, HNK-1+ lymphoid cells from the E+ fraction of CML patients were not defective in their ability to bind to the NK-sensitive target, K-562. In contrast, NK-defective B73.1+ lymphoid cells were partially defective in their ability to bind to K-562.

Antibodies, Monoclonal↗
PubMed1986

Biochemical comparison of epsilon [correction of gamma]-crystallins from duck and frog eye lenses.

A biochemical comparison has been made on the crystallins isolated from duck and frog lenses. Gel-permeation chromatography of lens homogenates from both classes on Fractogel TSK HW-55(S) revealed a homogeneous trimeric protein of 120 kDa in the duck lenses and a monomeric protein of 39 kDa in the frog lenses. Both crystallin fractions consist only of an approx. 38-kDa polypeptide in their subunit structures as determined by SDS gel electrophoresis. These two crystallins were compared with respect to their native molecular masses, subunit structures, peptide mapping and amino acid compositions in order to establish the identity of each crystallin. We have found differences in the protein structures of these two crystallins despite some degree of similarity in their amino acid compositions.

Amino Acids↗
PubMed1986

Inhibition of human natural killer cell activity by platelet-derived growth factor.

The present report demonstrates that the naturally occurring biologic substance, platelet-derived growth factor (PDGF), substantially inhibits human natural killer (NK) cell activity. More precisely, pretreatment of peripheral blood mononuclear cells for 2 h with nanogram amounts of either partially purified PDGF or highly purified PDGF significantly inhibited peripheral blood NK cell activity (cytotoxicity) in a dose-dependent manner as measured against the NK-sensitive target, K-562. Furthermore, pretreatment of purified NK cells for 2 h with nanogram amounts of purified PDGF also resulted in a significant, dose-dependent inhibition of human NK cell activity (cytotoxicity), as mediated by positively selected, B73.1+ human NK cells sorted on a fluorescence-activated cell sorter. In addition to the inhibition of NK-mediated cytotoxicity, nanogram amounts of purified PDGF also significantly inhibited the single-cell binding of B73.1+ human NK cells to the NK-sensitive target K-562, as determined by routine single-cell-binding assays (i.e. conjugate formation). The implications of these findings are discussed.

Cell Line↗
PubMed1985

Enhancement of endogenous production of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid in aortic smooth muscle cells by platelet-derived growth factor.

Platelet-derived growth factor (PDGF) has a chemotactic effect on smooth muscle cells, which is inhibited by lipoxygenase inhibitor caffeic acid. In order to study the role of endogenous lipoxygenase products of arachidonic acid on the chemotactic action of PDGF, effects of PDGF on the lipoxygenase pathway in smooth muscle cells were examined. Lipoxygenase products were analyzed by high-performance liquid chromatography. 15-, 5- and 12-lipoxygenase activities, in order of magnitude, were found in smooth muscle cell homogenate. However, when the lipoxygenase products were analyzed using intact cells prelabelled with [14C]arachidonic acid, only 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE) was found to be produced endogenously. In addition, 12-HETE was not released into the medium. Treatment of the cells with PDGF increased the endogenous production of 12-HETE. The amounts of intracellular 12-HETE in PDGF-treated cells were 126, 132 and 146% at 1, 3, and 10 hr's after the initiation of PDGF treatment, respectively, when control value at each time point was considered as 100%. Caffeic acid (10(-4) M) completely inhibited the PDGF effect on 12-HETE production. However, PDGF treatment did not significantly alter the 12-lipoxygenase activity. These results suggest that the stimulatory effect of PDGF on 12-HETE production was not mediated by the activation of 12-lipoxygenase activity. Since 12-HETE itself is a potent chemoattractant for smooth muscle cells, the present dat strongly suggest that 12-HETE could be an important intracellular mediator of the chemotactic action of PDGF on aortic smooth muscle cells.

Animals↗
PubMed1985

Induction of a decrease in renal NAD+-dependent 15-hydroxyprostaglandin dehydrogenase activity by estradiol in rats.

The effect of estradiol administration on renal and pulmonary NAD+-dependent 15-hydroxyprostaglandin dehydrogenase activities in rats was studied. Estradiol induced a significant decrease in renal but not in pulmonary enzyme activity. Kinetic parameters for the renal enzyme from control and treated groups were compared. An identical apparent Km for prostaglandin E2 was obtained for the enzyme from both groups. Vmax in the treated group was progressively decreased and plateaued 1 day after estradiol injection. The estradiol-induced decrease in renal enzyme activity was blocked by an anti-estrogen, nafoxidine, suggesting that the effect of estradiol was a was a receptor-mediated event. The decrease in renal prostaglandin catabolic enzyme activity induced by estradiol may result in prolonging the half-life of circulating prostacyclin and may account, in part, for the anti-thrombogenic effect of estradiol.

Animals↗
PubMed1985

Increase in 12-lipoxygenase activity in platelets of spontaneously hypertensive rats.

12-Lipoxygenase activity in platelets of spontaneously hypertensive rats was investigated. Enzyme activity was measured in the absence and the presence of reduced glutathione. In both assay conditions, 12-lipoxygenase activity in platelets of spontaneously hypertensive rats was significantly higher than that in platelets of normotensive rats. Since 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), a 12-lipoxygenase product of arachidonic acid in platelets, has been reported to be a potent chemoattractant for aortic smooth muscle cells, increase in biosynthesis of 12-HETE in platelets of spontaneously hypertensive rats might contribute to the explanation of pathogenesis of vascular disorder commonly found in hypertension patients.

Animals↗
PubMed1985

A cross-cultural study of depressive symptomology.

Black (N = 26), white (N = 26) and Overseas Chinese (N = 32) college students were surveyed with Zung's Self-rating Depression Scale (SDS). With the exception of two items where marginally significant differences were found, there were no quantitative differences in the results across these ethnic groups. Inter-item analyses, factor analyses and comparison of factor profiles indicated that the items clustered in different configurations for the three groups. The factors contributing the most variances differed in their item contents across the ethnic groups: a mixture of affective and somatic complaints characterizes the black group; existential and cognitive concerns characterize the white group and somatic complaints characterize the Overseas Chinese group. Discussion was focused on issues concerning cultural conception of psychological difficulties, communication styles used to communicate these difficulties and situational variables affecting performances on psychological diagnostic tests.

Adaptation, Psychological↗
PubMed1985

Specific cleavages of DNA by ascorbate in the presence of copper ion or copper chelates.

The DNA-cleavage specificity of ascorbate in the presence of copper ion is analyzed with end-labeled pBR322 DNA fragments. The nonenzymatic reaction of Cu(II)/ascorbate and DNA shows certain degrees of cleavage preference toward purine-containing short segments in the labeled DNA under mild conditions (at 0 degrees C and 10 min). The segments of pyrimidine clusters are least susceptible to cleavage. The DNA scission cannot be detected in the absence of metal ions, and is greatly diminished in the presence of EDTA and metal-chelating peptide. It is more specific than the nuclease-like scission activity induced by cuprous-phenanthroline complex. This scission activity in relation to the antiviral and antitumor activities of vitamin C reported in the literature deserves a crucial consideration.

Ascorbic Acid↗
PubMed1984

Pulmonary NAD+-linked 15-hydroxyprostaglandin dehydrogenase activity is decreased by cigarette smoking.

Male rats were exposed to freshly generated cigarette smoke once daily for 4 to 13 weeks. Inhalation of smoke was verified by elevated level of carboxyhemoglobin. NAD+-dependent 15-hydroxyprostaglandin dehydrogenase activity, the key enzyme responsible for biological inactivation of prostaglandins, was found to decrease in lung but not in kidney or stomach following cigarette smoke exposure. The consequence of impaired pulmonary metabolism of prostaglandins and thromboxane may result in alteration of vascular homeostasis and subsequently lead to cardiovascular disorders commonly found in smokers.

Animals↗
PubMed1984

Changes in prostacyclin and thromboxane biosynthesis and their catabolic enzyme activity in kidneys of aging rats.

The effects of aging on the prostacyclin and thromboxane biosynthesis and prostaglandin catabolic enzyme activity in rat kidney were investigated. The prostacyclin biosynthesis, using arachidonic acid as substrate, was the greatest in young kidneys (2 months old) and then progressively decreased in mature (12 months old) and old (24 months old) kidneys, while thromboxane biosynthetic activity showed no significant change as a function of age. When prostaglandin H2 was used as substrate, the prostacyclin and thromboxane biosynthesis showed similar results as when arachidonic acid was used as substrate; the prostacyclin biosynthesis progressively decreased and thromboxane biosynthesis showed no significant change as a function of age. The fatty acid cyclooxygenase in kidney was measured by a specific radioimmunoassay. No significant change in renal fatty acid cyclooxygenase as a function of age was found. Thus, we concluded that the progressive decrease in renal prostacyclin biosynthesis as a function of age is due to a defect in prostacyclin synthetase in aged kidneys. The prostaglandin catabolic enzyme, NAD+-dependent 15-hydroxyprostaglandin dehydrogenase, in kidneys was also investigated. The enzyme activity progressively decreased as a function of age, which suggested a decrease in the metabolism of thromboxane A2 in aged kidneys. The present results, indicating a decrease in renal prostacyclin biosynthesis and renal 15-hydroxyprostaglandin dehydrogenase activity with aging, might contribute to a plausible explanation of the progressive decrease in renal functions in the elderly.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Characterization of human growth hormone from acromegalic pituitary tumors.

Human growth hormone (HGH) was extracted from acromegalic pituitary tumors at pH 10.5 and precipitated with ammonium sulfate at 20-40% saturation. It was purified on a Sephadex G-100 column to yield monomeric HGH. The tumor-HGH was indistinguishable from the authentic one in polyacrylamide gel electrophoresis at pH 8.3 or in the presence of sodium dodecyl sulfate, high-performance liquid chromatography, radioimmunoassay, peptide map, amino acid composition and N-terminal partial amino acid sequence. The tumor-HGH is active in the tibia assay and bodyweight gain test in hypophysectomized rats with comparable potency to that of the authentic sample.

Acromegaly↗
PubMed1983

Estradiol suppresses electrically-induced arterial thrombosis by increasing prostaglandin biosynthesizing activity of the aorta in rats.

The anti-thrombotic effect of estradiol was studied using an electrically induced thrombus model in rats. Estradiol treatment significantly inhibited the thrombus formation induced by electric shock. In the meantime, a stimulation of prostacyclin biosynthesis by estradiol in aortas was found. This is the first report showing the correlation between the effects of the estradiol on the thrombus formation in an experimental model and on the prostacyclin production by aortas in the same animal system.

Animals↗
PubMed1983

Cigarette smoking stimulates lipoxygenase but not cyclooxygenase pathway in platelets.

Male rats were exposed to freshly generated cigarette smoke once daily for 4 to 8 weeks. Inhalation of smoke was verified by elevated level of carboxyhemoglobin. Arachidonate metabolism through lipoxygenase and cyclooxygenase pathways in platelets was determined. Cigarette smoking increased 12-lipoxygenase activity significantly without affecting the cyclooxygenase pathway. In view of platelet-leukocyte interactions and potent chemotactic activity of 12-HETE for aortic smooth muscle cell migration, increased 12-lipoxygenase activity may predispose individuals to atherosclerosis, thromboembolism and emphysema commonly found in smokers.

Animals↗
PubMed1983

Polyamide thin-layer chromatography of phosphorylated tyrosine, threonine, and serine.

One-dimensional thin-layer chromatography on polyamide plates offers an easy and rapid identification of O-phosphotyrosine. The thin-layer plate is developed for 30 min in 5% propionic acid containing 0.013%-0.025% sodium dodecyl sulfate. O-Phosphotyrosine, with Rf = 0.54, can be well separated from O-phosphothreonine and O-phosphoserine, which comigrate at Rf = 0.72.

Chromatography, Thin Layer↗
PubMed1983

Aortic smooth muscle cell migration caused by platelet-derived growth factor is mediated by lipoxygenase product(s) of arachidonic acid.

The relation between platelet-derived growth factor (PDGF)-induced smooth muscle cell migration, measured in Boyden chambers, and cellular arachidonic acid cascade was studied by using rat aortic smooth muscle cells. Partially purified PDGF stimulated cell migration significantly at a concentration of 1.33-133.0 micrograms/ml. Treatment of the cells with 10(-4)M of 5,8,11,14-eicosatetraynoic acid, an inhibitor of lipoxygenase and cyclooxygenase, and 10(-4)M of caffeic acid, a specific inhibitor of lipoxygenase, caused a significant suppression of PDGF-induced cell migration. Treatment with indomethacin, an inhibitor of cyclooxygenase, did not affect cell migration. These data indicate the involvement of a lipoxygenase product(s) of arachidonic acid in PDGF-associated smooth muscle cell migration.

Animals↗