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Biomedical subjects

W C Chang

Publications and source records attributed to W C Chang.

At least 289 records · Page 16Linked to original sources
PubMed1980

Stimulation of prostaglandin cyclooxygenase and prostacyclin synthetase activities by estradiol in rat aortic smooth muscle cells.

The effects of estradiol on the arachidonic acid pool and prostacyclin biosynthetic activity in rat aortic smooth muscle cells were studied. Estradiol has no significant effect on the distribution of [14C]arachidonic acid in cells with respect to prostacyclin production assay, the endogenous fatty acid (specifically, arachidonic acid) composition of cellular phospholipid fractions and cellular phospholipase (or/and lipase) activities. However, estradiol significantly stimulates both prostaglandin cyclooxygenase and prostacyclin synthetase activities of cells, and induction of new protein biosynthesis is involved in the effect of estradiol on the stimulation of prostacyclin biosynthetic activity.

Animals↗
PubMed1980

Age-related decrease in prostacyclin biosynthetic activity in rat aortic smooth muscle cells.

Prostaglandin biosynthetic activity in cultured rat aortic smooth muscle cells was investigated as a function of age by both intact cell and cell-free homogenate assays. The total cyclooxygenase activity for prostaglandin biosynthesis is the same in cells from young and old rats. However, cells from young rats proceduce more prostacyclin than prostaglandin E2, and cells from old rats produce more prostaglandin E2 than prostacyclin. Age-related decrease in prostacyclin biosynthesis is also found when protaglandin H2 is used as substrate. Lower prostacyclin and higher prostaglandin E2 biosynthetic activity in aortic smooth muscle cells from aged rats may contribute to the direct explanation of pathogenesis of spontaneous atherosclerosis and artial thrombosis in aged humans and other mammals.

Aging↗
PubMed1980

In Vitro biosynthesis of adipocyte proteins having the characteristics of glucocorticoid receptors.

A quantitative method for the measurement of putative glucocorticoid receptor biosynthesis in rat adipocytes is described. The method utilizes the incorporation of radioactive amino acids into newly synthesized putative receptor proteins and their subsequent separation from other labeled proteins by affinity chromatography. Dexamethasone and deoxycorticosterone-Sepharose are used as affinity adsorbants. Specific binding of radioactive putative receptors to these gels is time- and protein concentration-dependent, and is abolished by exposure of cells to cycloheximide, pretreatment of adipocyte cytosol preparations with unlabeled steroids or incubation of cytosols at 37C for 4 h. Specifically bound radioactivity, which represents about 10% of the radioactivity initially associated with affinity adsorbants can be quantitatively eluted under rigidly defined conditions including high ionic strength. Specifically eluted material, which comprises up to 50% of total eluted radioactivity sediments at 3.8 S in sucrose gradients containing 1 M KCl, and electrophoretically migrates on 0.1% SDS gels in single band with a molecular weight of about 50 000. The sedimentation coefficient is comparable to that of the native adipocyte cytosol receptor not subject to affinity chromatography (3.7 S). Under low ionic-strength conditions most of the native receptor sediments at 8 S. The molecular weight of 50 000 is in the range of those reported for glucocorticoid receptors of liver (45 000---66 000 for monomers). The properties of the protein or proteins measured in the present system are therefore consistent with the current state of knowledge regarding glucocorticoid receptors in adipocytes.

Adipose Tissue↗
PubMed1980

Stimulation of prostacyclin biosynthetic activity by estradiol in rat aortic smooth muscle cells in culture.

Effects of estradio on cell proliferation and prostacyclin biosynthetic activity in cultured rat aortic smooth muscle cells are investigated. Prostacyclin is the major product formed from arachidonic acid by the cells, both in a cell-free homogenate system and in intact cells. When cells are treated with estradiol, no effect on cell proliferation is observed. However, a significantly stimulatory effect on prostacyclin biosynthetic activity in cells is evident. The maximal effect of estradiol on the stimulation of prostacyclin biosynthetic activity is observed after 5-day treatment of the cells with estradiol at its physiological concentration (10(-9) M). Our results support the idea that estradiol would be a protective hormone in atherosclerotic heart disease.

Adenosine Diphosphate↗
PubMed1980

Elastinolytic activity in the rat aortic smooth muscle cells in culture.

Elastinolytic activity was examined in cultured rat aortic smooth muscle cells, using Congo Red elastin as a substrate. Elastinolytic activity was demonstrated in the soluble fraction of sonicated smooth muscle cells, with an optimal pH around 10.0. The soluble fraction also showed elastase-like esterolytic activity against the synthetic substrate, N-succinyl-trialanyl-paranitroanilide.

Animals↗
PubMed1980

beta-Endorphin omission analogs: dissociation of immunoreactivity from other biological activities.

An analog of human beta-endorphine with omission of four residues at positions 11, 14, 20, and 22 has been synthesized. This analog and other synthetic analogs with deletion of a single amino acid at position 2, 5, 6, 10, 11, 12, 13, 15, or 22 have been assayed for analgesic potency, ileal opiate activity,opiate receptor-binding activity, andimmunoreactivity. Results show that deletion of a single amino acid of the beta-endorphin molecule outside of the enkephalin segment to give des-Gln11-, des-Thr12, des-Pro13-, des-Leu14-, des-Val15-, des-Asn20-, or des-Ile22-beta-endorphin markedly reduced or abolished the immunoreactivity yet gave substantial retention of opiate potencies. Deletion of a single amino acid of beta-endorphin within the enkephalin segment (des-Gly3- or des-Met5-beta-endorphin) did not markedly affect the immunoactivity; however, the opiate activities were abolished or markedly reduced. The data indicate a clear dissociation of immunoactivity from analgesic, ileal-opiate, and opiate receptor-binding activities.

Animals↗
PubMed1980

Human beta-endorphin: synthesis and characterization of analogs iodinated and tritiated at tyrosine residues 1 and 27.

Three tritiated analogs of human beta-endorphin have been prepared from their corresponding iodinated analogs. The iodinated analogs (diiodotyrosine at positions 1, 27 or 1 and 27) were synthesized by the solid-phase method and were found to have biological and physical properties which were altered when compared with the native molecule. Catalytic exchange of these iodinated analogs in the presence of tritium yielded tritiated human beta-endorphins having full biological activity and specific activity of 50-100 Ci/mmol. Both the iodinated and tritiated beta-endorphin analogs were shown to be homogeneous by chromatography on carboxymethylcellulose, partition chromatography, paper chromatography, amino acid analysis, electrophoresis, high performance liquid chromatography, and isoelectric focusing on polyacrylamide.

Amino Acid Sequence↗
PubMed1979

beta-Endorphin: synthesis of analogs modified at the carboxyl terminus with increased activites.

Three analogs of human beta-endorphin (beta h-EP) have been synthesized: [Gly31]beta h-EP, [Gly31]beta h-endorphinamide, and [Gly31]beta h-endorphinylglycine. All are more active than beta h-EP in both the guinea pig ileum bioassay and the opiate receptor binding assay. The last two analogs are about twice as active as beta h-EP in an assay for analgesia. Modification at position 31 and extension at the COOH terminus may afford a route toward analogs with even greater biological activity.

Analgesics↗
PubMed1979

Human beta-endorphin. Immunoreactivity of synthetic analogs with various chain lengths.

Immunoreactivity of synthetic human beta-endorphin analogs with various chain lengths has been examined using a specific radioimmunoassay. It was found that beta-endorphin-(1--21) and analogs of shortened chain exhibit no immunoreactivity, whereas beta-endorphin-(1--15) possesses significant in vitro opiate activity. It appears that immunoreactivity of beta-endorphin resides in the COOH-terminal segment of residues (22--31). The data also show the lack of correlation between opiate and immunological activities of beta-endorphin.

Amino Acid Sequence↗
PubMed1979

Synthesis of biological activity of human beta-endorphin analogs with disulfide bridges.

Three analogs of human beta-endorphin containing internal cystine bridges have been synthesized and their biological activities have been determined. It was found that the analogs with disulfide bridges between positions 17 and 26 or 11 and 26 retained full opiate activity as estimated by guinea ileum assay, whereas the analog with a cystine bridge between positions 7 and 26 showed reduced opiate activity. None of the analogs retained significant immunoactivity as revealed by radioimmunoassay.

Amino Acid Sequence↗
PubMed1978

Location of disulfide bridges in cardiotoxin from the venom of Formosan cobra (NAJA NAJA ATRA).

The location of the four disulfide bridges in cardiotoxin from the venom of the Formosan cobra, Naja naja atra, was determined by isolating cystine-containing peptides from the enzymic and partial acid hydrolyzates of the intact toxin. The results indicate that the disulfide bridges are formed by half cystine residues 3--21, 14--38, 42--53, and 54--59. The amino acid sequence at the position 48--49 was revised to -Leu-Val- instead of Val-Leu- as reported previously.

Amino Acid Sequence↗
PubMed1978

Synthesis and opiate activity of human beta-endorphin analogs with various chain lengths.

The synthesis of beta h-endorphin -(1--15), -(1--21), -(1--26), -(1--28) and -(1--29) have been accomplished by the solid-phase method. The opiate activities of the peptides were measured in the guinea pig ileum assay. Their relative potencies were beta h-endorphin (beta h-EP), 1.00; Met-enkephalin, 0.25: beta h-EP-(1--15), 0.17; beta H-EP-(1--21), 0.46; beta H-EP-(1-26), 0.48; beta h-EP-(1--28), 0.89; beta h-EP-(1--29), 1.04.

Amino Acid Sequence↗