Biomedical subjects

A Aryana

Publications and source records attributed to A Aryana.

6 recordsLinked to original sources

PubMed1996

Impaired activation of adenylyl cyclase in lung of the Basenji-greyhound model of airway hyperresponsiveness: decreased numbers of high affinity beta-adrenoceptors.

1. To evaluate mechanisms involved in the impaired beta-adrenoceptor stimulation of adenylyl cyclase in tissues from the Basenji-greyhound (BG) dog model of airway hyperresponsiveness, we compared agonist and antagonist binding affinity of beta-adrenoceptors, beta-adrenoceptor subtypes, percentage of beta-adrenoceptors sequestered, and coupling of the beta-adrenoceptor to Gs alpha in lung membranes from BG and control mongrel dogs. We found that lung membranes from the BG dog had higher total numbers of beta-adrenoceptors with a greater percentage of receptors of the beta 2 subtype as compared to mongrel lung membranes. 2. Agonist and antagonist binding affinity and the percentage of beta-adrenoceptors sequestered were not different in BG and mongrel dog lung membranes. However, the percentage of beta-adrenoceptors in the high affinity state for agonist was decreased in BG lung membranes suggesting an uncoupling of the receptor from Gs alpha. 3. Impaired coupling between the beta-adrenoceptor and G protein documented by the decreased numbers of beta-adrenoceptors in the high affinity state in BG lung membranes, is a plausible explanation for the reduced stimulation of adenylyl cyclase and the resultant reduction in airway smooth muscle relaxation in this model.

Adenylyl Cyclases↗

PubMed1995

Reduced adenylyl cyclase activation with no decrease in beta-adrenergic receptors in basenji greyhound leukocytes: relevance to beta-adrenergic responses in airway smooth muscle.

Mononuclear leukocytes (MNLs) have been used as a model of beta-adrenergic responsiveness of airway smooth muscle, but the relevance of this model remains controversial. The basenji greyhound (BG) dog model of airway hyperresponsiveness shares some features with human asthma, and airway smooth muscle shows a selective impairment in isoproterenol-stimulated adenylyl cyclase activity. In this study, MNL membranes were obtained from these same dogs, and the beta-adrenergic receptor-adenylyl cyclase cascade function was compared with that in airway smooth muscle. beta-Adrenergic receptor numbers and affinities for iodine 125-cyanopindolol were similar in the two dog groups (receptor numbers [Bmax] = 441 +/- 101 and 447 +/- 61 fmol/mg protein and dissociation constant [Kd] = 269 +/- 44 and 312 +/- 60 pmol/L for mongrel and BG MNLs, respectively). Quantities of the Gs alpha protein were not different in the membranes as determined by immunoblotting. Stimulation of adenylyl cyclase by isoproterenol (100 mumol/L) was impaired in MNL membranes of BG membranes (22% +/- 4% increase over guanosine triphosphate [10 mumol/L]) compared with mongrel membranes (47% +/- 8.6% increase over guanosine triphosphate [10 mumol/L], p < 0.05). Stimulation of adenylyl cyclase by prostaglandin E1 (10 mumol/L), NaF (10 mmol/L), or forskolin (10 mumol/L) did not differ in membranes from the two groups. No difference was found in the lymphocyte subsets in the two groups as determined by flow cytometry. These findings are qualitatively similar to studies of trachealis muscle membranes from these same dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗

PubMed1995

Expression of muscarinic receptor subtypes and M2-muscarinic inhibition of adenylyl cyclase in lung.

The relative distribution and absolute quantities of muscarinic receptor subtypes m1, m2, m3, and m4 were determined in membranes of canine trachealis muscle, bronchi, and lung parenchyma by immuno-precipitation with receptor subtype-specific rabbit polyclonal antisera. Additionally, the functional coupling of muscarinic receptors to the inhibition of adenylyl cyclase was related to the presence of m2-muscarinic receptors in each region. Immunoprecipitation identified more total muscarinic receptors in trachealis muscle than in bronchi or lung. m2-Muscarinic receptor predominated in tracheal muscle (372 +/- 85 fmol/mg protein) with fewer m3 receptors (48 +/- 5 fmol/mg protein). Bronchi contained 6.6 +/- 2.0 and 9.2 +/- 1.8 fmol/mg protein of m2 and m3 receptors, respectively. Lung parenchyma contained 13.9 +/- 3.9 fmol/mg protein of m3 receptors. Adenylyl cyclase activity increased in response to guanosine triphosphate and isoproterenol in membranes from all three lung regions, but muscarinic-mediated inhibition of adenylyl cyclase occurred only in trachealis membranes. These studies provide the first quantitative assessment of muscarinic receptor subtypes in different regions of the lung and relate the ability to measure muscarinic inhibition of adenylyl cyclase to the presence of m2 receptors.

Acetylcholine↗

PubMed1995

Basenji-greyhound dog: increased m2 muscarinic receptor expression in trachealis muscle.

Airway smooth muscle from asthmatic humans and from the Basenji-greyhound dog (BG) dog is hyporesponsive to beta-adrenergic agonist stimulation. Because adenylyl cyclase is under dual regulation in airway smooth muscle, we compared muscarinic receptor-coupled inhibition of adenylyl cyclase in airway smooth muscle from BG and mongrel dogs. Inhibition of forskolin-stimulated adenylyl cyclase activity by the muscarinic M2 agonist oxotremorine was greater in airway smooth muscle membranes from BG compared with mongrel controls. Quantitative immunoprecipitation studies showed increased numbers of m2 but not m3 muscarinic receptors in the BG airway smooth muscle. The enhanced ability of muscarinic agonists to inhibit adenylyl cyclase in BG airway smooth muscle may be due to the greater numbers of muscarinic m2 receptors, which may account in part for impaired airway smooth muscle relaxation in the BG model of airway hyperresponsiveness.

Adenylyl Cyclase Inhibitors↗

PubMed1995

Direct effects of inhaled nitric oxide on canine peripheral airways.

The effects of nitric oxide on peripheral airways in vivo, and whether these effects occur via direct or indirect mechanisms, are unknown. We studied effects of inhaled nitric oxide on histamine-constricted canine peripheral airways in the presence or absence of atropine and an inhibitor of guanylyl cyclase, methylene blue. Peripheral resistance (Rp) was measured by using a wedged-bronchoscope technique in anesthetized dogs. A stable baseline Rp was established. Histamine was infused intravenously, and increasing concentrations of nitric oxide (50-500 ppm) were delivered through the bronchoscope. In separate experiments, histamine was infused intravenously in the presence or absence of atropine (0.2 mg/kg iv) or methylene blue (20 mg/min iv). When Rp stabilized, nitric oxide (500 ppm) was delivered. Nitric oxide partially reversed histamine-induced bronchoconstriction in a dose-dependent fashion (maximum of 42 +/- 3% reduction at 500 ppm; n = 5; P < 0.01) that did not differ in the presence or absence of atropine. Methylene blue blocked the effect of nitric oxide on histamine-induced constriction (n = 6; P = 0.45). These findings suggest that high concentrations of nitric oxide produce small but significant bronchodilation of peripheral airways through a mechanism independent of the cholinergic neural pathway. The mechanism of action appears to involve activation of guanylyl cyclase.

Administration, Inhalation↗

PubMed1993

Sequence requirements for myosin gene expression and regulation in Caenorhabditis elegans.

Four Caenorhabditis elegans genes encode muscle-type specific myosin heavy chain isoforms: myo-1 and myo-2 are expressed in the pharyngeal muscles; unc-54 and myo-3 are expressed in body wall muscles. We have used transformation-rescue and lacZ fusion assays to determine sequence requirements for regulated myosin gene expression during development. Multiple tissue-specific activation elements are present for all four genes. For each of the four genes, sequences upstream of the coding region are tissue-specific promoters, as shown by their ability to drive expression of a reporter gene (lacZ) in the appropriate muscle type. Each gene contains at least one additional tissue-specific regulatory element, as defined by the ability to enhance expression of a heterologous promoter in the appropriate muscle type. In rescue experiments with unc-54, two further requirements apparently independent of tissue specificity were found: sequences within the 3' non-coding region are essential for activity while an intron near the 5' end augments expression levels. The general intron stimulation is apparently independent of intron sequence, indicating a mechanistic effect of splicing. To further characterize the myosin gene promoters and to examine the types of enhancer sequences in the genome, we have initiated a screen of C. elegans genomic DNA for fragments capable of enhancing the myo-2 promoter. The properties of enhancers recovered from this screen suggest that the promoter is limited to muscle cells in its ability to respond to enhancers.

Animals↗