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Biomedical subjects

C M Yang

Publications and source records attributed to C M Yang.

At least 145 records · Page 8Linked to original sources
PubMed1987

The effect of estrogen on luteinizing hormone-releasing hormone binding sites in hypothalamic membranes.

The binding sites for [125I]LHRH were characterized in membranes from the hypthalamus and the effect of estrogen on the binding characteristics was studied in ovariectomized female rats. The radioligand, [125I]LHRH, was found to bind specifically to membranes from the hypothalamus at a maximal level, with an optimal temperature of 0 degrees C and a pH between 7 and 8. The binding was enhanced by NaCl at a concentration of 0.1-0.2 M. The specifically bound [125I]LHRH was only displaced by LHRH, but not by sodium iodide (NaI), bovine serum albumin and other hormones, such as thyrotropin-releasing hormone, bradykinin, oxytocin, prolactin, luteinizing hormone and growth hormone. The divalent metal ions, copper (Cu2+) and mercury (Hg2+), inhibited the specific binding of [125I]LHRH completely, whereas magnesium (Mg2+) and calcium (Ca2+) caused a decrease in binding. As revealed from Scatchard plot analysis, the binding sites for [125I]LHRH in the hypothalamus had a dissociation constant of 0.40 +/- 0.03 microM and the maximum number of binding sites was 98.55 +/- 4.34 pmol/mg protein. Treatment of female rates (ovariectomized for 3 weeks) with 4 micrograms of estradiol benzoate caused a statistically significant decrease in the maximal number of binding sites without any significant effect on the dissociation constant. However, the direct addition of estradiol hemisuccinate to the membrane preparations had no statistically significant effect on the specific binding of [125I]LHRH. The present study provides the evidence that estrogen decreases the density of binding sites for [125I]LHRH in the hypothalamus in vivo.

Animals↗
PubMed1987

Protected methionine supplementation with extruded blend of soybeans and soybean meal for dairy cows.

Methionine may be the first amino acid limiting milk production in early lactation cows. To evaluate this further, 23 high producing Holstein cows (9 multiparous and 14 primiparous) were fed an extruded blend of soybeans and soybean meal (40:60) without or with 15 g of added DL-methionine as 50 g of ruminally protected methionine product during wk 4 to 16 postpartum. Cows were fed a 15.8% crude protein total mixed ration consisting of 30% (dry basis) corn silage, 15% alfalfa hay, and 55% concentrate mix. Covariant-adjusted yields of milk (35.3 and 33.9 kg/d) and solids-corrected milk (29.3 and 28.2 kg/d) were lower for cows fed ruminally protected methionine, whereas yields of 4% fat-corrected milk (28.2 and 27.4 kg/d) were similar. Percentages of fat (2.68 and 2.69) and solids-not-fat (8.82 and 8.83) were similar, and percentages of protein (2.86 and 2.90) were higher from cows fed supplemental methionine. Dry matter intakes (20.5 and 21.6 kg/d) were higher for cows fed ruminally protected methionine. Methionine concentrations in arterial and venous serum were elevated slightly by feeding supplemental methionine. Although methionine was still the first-limiting amino acid as calculated by two different methods, supplementation of this diet with ruminally protected methionine did not increase production of early lactation cows.

Animal Feed↗
PubMed1986

Enhancement of A23187-induced production of the slow-reacting substance on peripheral leukocytes from subjects with asthma.

Peripheral polymorphonuclear leukocytes and mononuclear leukocytes from normal subjects and subjects with asthma were studied for their production of slow-reacting substance (SRS) after nonimmunologic stimulation with the calcium ionophore A23187. The amount of SRS generated was determined in both polymorphonuclear leukocyte fractions and mononuclear leukocyte fractions from four groups of subjects: 10 with extrinsic asthma, five with mixed-type asthma, 10 with intrinsic asthma, and 10 normal control subjects. In either cell type, the SRS produced was much more in cells from subjects with extrinsic asthma and less in cells from subjects with the mixed-type asthma, intrinsic asthma, and the normal subjects in order of decreasing quantity. These results indicate the amount of SRS generated by nonimmunologic stimulation with calcium ionophore is related to the degree of atopy and suggest the existence of an intrinsic cellular defect in cells from subjects with atopic asthma in addition to the effects of higher serum levels of IgE antibodies.

Adult↗
PubMed1986

Biochemical characteristics of muscarinic cholinoreceptors in swine tracheal smooth muscle.

The tritiated muscarinic cholinoreceptor antagonist quinuclidinyl benzilate, [3H]QNB, was used to characterize the muscarinic receptors associated with homogenized membrane of the smooth muscle from swine trachea. Based on receptor binding assays, the homogenate had specific, saturable, high-affinity receptors for [3H]QNB. Specific binding was time- and temperature-dependent. The association of [3H]QNB with the muscarinic receptor reached equilibrium much sooner at 37 degrees C than 25 degrees C at a [3H]QNB concentration of 180 pM (30 min and 2 h, respectively). Equilibrium at both temperatures was attained within 5 min at a [3H]QNB concentration of 1800 pM. All remaining experiments were performed at 37 degrees C. Binding was saturable with respect to [3H]QNB and tissue concentrations. Analysis of binding isotherms yielded an apparent equilibrium dissociation constant (KD) of 51 +/- 20 pM and a maximum receptor density (Bmax) of 2.17 +/- 0.27 pmole/mg protein. The Hill coefficient for [3H]QNB binding was 1.07 +/- 0.16. The association (K1) and dissociation (K-1) rate constants were determined to be (5.51 +/- 0.16) X 10(8) M-1 min-1 and (1.41 +/- 0.18) X 10(-2) min-1, respectively. KD calculated from the ratio of K1 and K-1 was 26.3 +/- 3.8 pM; this value is close to the value of KD calculated from Scatchard plots of binding isotherms. The density of muscarinic receptor binding sites was 10-fold greater in tracheal smooth muscle than in tracheal epithelium (0.20 +/- 0.03 pmole/mg protein). There is no difference between weanling and young adult swine in the density of muscarinic receptors in tracheal smooth muscle. The nonselective muscarinic antagonists atropine, scopolamine and quinuclidinyl benzilate (QNB) competitively inhibited [3H]QNB binding to the homogenate with Hill coefficients of 0.9-1.0 and inhibition constants (Ki) of nanomolar range. Competition with selective muscarinic antagonists pirenzepine and 3-quinuclidinyl xanthene-9-carboxylate (QNX) gave Ki values, 0.26 M and 0.78 nM, respectively, and Hill coefficients of approximately 1. There was a single population of [3H]QNB binding sites of the M2 subtype for all tested muscarinic antagonists. Competition with selective muscarinic agonists pilocarpine and carbachol yielded Ki values of micromolar range, Hill coefficients of less than 1, and revealed the existence of two binding sites (P less than 0.01).

Animals↗
PubMed1984

Isolation, chemical structure, acute toxicity, and some physicochemical properties of territrem C from Aspergillus terreus.

Territrem C, a new tremorgenic mycotoxin (C28H32O9; molecular weight, 512.20) was isolated from the chloroform extract of rice cultures of Aspergillus terreus 23-1, which also produces territrems A and B. Isolation, acute toxicity, and some physicochemical properties of territrem C are discussed in this paper. The spectral and chemical evidence indicated that the structural difference between territrem C and territrem B (C29H34O9) was in their phenyl moieties: a 4-hydroxy-3,5-dimethoxy phenyl group in territrem C and a 3,4,5-trimethoxy phenyl group in territrem B. It was also demonstrated that territrem B was obtained by methylation of territrem C with dimethyl sulfate.

Animals↗
PubMed1984

[Characterization of slow reacting substance of anaphylaxis in asthmatic sputum].

Sputum from asthmatics contained a mediator similar to slow reacting substance of anaphylaxis (SRS-A), capable of inducing contraction of guinea pig ileum. This mediator possessed the major characteristics of SRS-A, including stability in both neutral and alkaline solutions, lability in boiling acidic solution, destruction by arylsulfatase, inhibition by FPL 55712 and resistance to diphenhy dramine . Thus, we proved that the "SRS-A like" mediator was in fact SRS-A. The activity of histamine in these patients' sputa could be inhibited only by diphenhydramine, but could not be altered by any of the other treatments noted above.

Adult↗
PubMed1983

The design and implementation of a regional economic-demographic simulation model.

The management of urban growth patterns in the United States in order to maximize the benefits of public and private investments in urban areas is examined. The authors present "the results of a modelling design effort to link a hybrid regional input-output model to demographic, labor force and energy models for use in planning in the San Francisco Bay Region. Extensive use of system feedback is a major component of this research effort. Summary results of the model outputs are presented...."

Americas↗
PubMed1980

Pharmacological comparison of bPTH-(1-34) and other hypotensive peptides in the dog.

The purpose of the present study was to compare the potency, effectiveness and duration of action of synthetic bPTH-(1-34) with those of other known hypotensive peptides in the anesthetized dog. Of sixteen peptides tested in the present study only 8 were demonstrated to possess hypotensive activity. While bPTh-(1-34) was one of the least potent of the hypotensive peptides, it was equal to or greater than the other peptides in terms of effectiveness and duration of action. Of all the peptides studied, substance P and eledosin were the most potent in terms of their hypotensive action. It is suggested that perhaps substance P and eledoisin might act at a different site or through different mechanisms than do vasoactive intestinal peptide (V.I.P.), corticotropin inhibiting peptide (C.I.P.), neurotensin, xenopsin, bradykinin and bPTH-(1-34).

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Effects of ethanol on glutathione conjugation in rat liver and lung.

The ability of ethanol to alter glutathione (GSH) conjugation and its dependence upon duration of administration were investigated in rats in correlation with lipid peroxidation and the induction of microsomal enzymes. Significant decreases in hepatic GSH and glutathione-S-transferase (GST) activity in both liver and lung were found in rats treated acutely with ethanol (4 g/kg body weight 6 hr prior to killing). These decreases were accompanied by an increased loss of both GSH and GST into the plasma and increased hepatic lipid peroxidation. On the other hand, there was a dose-dependent increase in hepatic GSH after chronic administration of ethanol in drinking water (5 and 10%) for 3 weeks. This increase in hepatic GSH may be due to increased synthesis of GSH in the liver. No significant induction of GST by chronic ethanol treatment was observed in either organ. Ethanol was compared with the well-known inducers phenobarbital and beta-naphthoflavone. Although there was some evidence of increases in lipid peroxidation and/or microsomal enzyme activity with the inducers, no simple link between these increases and the induction of GST activity was identified.

Animals↗