Biomedical subjects

D B Jacoby

Publications and source records attributed to D B Jacoby.

61 records · Page 4Linked to original sources

PubMed1988

Influenza infection causes airway hyperresponsiveness by decreasing enkephalinase.

Ferret tracheal segments were infected with human influenza virus A/Taiwan/86 (H1N1) in vitro. After 4 days, the smooth muscle contractile responses to acetylcholine and to substance P were measured. The response to substance P was markedly accentuated, with a threefold increase in force of contraction at a substance P concentration of 10(-5) M, the highest concentration tested. In contrast, the response to acetylcholine was not affected by viral infection. Histological examination of tissues revealed extensive epithelial desquamation. Activity of enkephalinase (neutral metallo-endopeptidase, EC.3.4.24.11), an enzyme that degrades substance P, was decreased by 50% in infected tissues. Inhibiting enkephalinase activity by pretreating with thiorphan (10(-5) M) increased the response to substance P to the same final level in both infected and control tissues. Inhibiting other substance P-degrading enzymes including kininase II (angiotensin-converting enzyme), serine proteases, and aminopeptidases did not affect the response to substance P. Inhibiting cyclooxygenase and lipoxygenase activity using indomethacin and BW 755c did not affect hyperresponsiveness to substance P. Pretreating tissues with antagonists of alpha-adrenoceptors, beta-adrenoceptors, and H1 histamine receptors (phentolamine 10(-5) M, propranolol 5 X 10(-6) M, and pyrilamine 10(-5) M, respectively) had no effect on substance P-induced contraction. These results demonstrate that infection of ferret airway tissues with influenza virus increases the contractile response of airway smooth muscle to substance P. This effect is caused by decreased enkephalinase activity in infected tissues.

Animals↗

PubMed1988

Effect of human eosinophil major basic protein on ion transport in dog tracheal epithelium.

Eosinophil major basic protein (MBP) is a granule-associated cytotoxic protein found in sputum and deposited on airway tissues of patients with acute asthma. We therefore studied the effect of human MBP on ion transport in dog tracheal epithelium. We mounted the posterior tracheal membranes of mongrel dogs in Ussing chambers and measured potential differences across the membranes and short-circuit current. Using 22Na+ and 36Cl- as tracers, we determined net ion movements. The addition of MBP (5 X 10(-6) M) to the mucosal, but not to the serosal, side of the membranes produced an increase in short-circuit current from 2.25 +/- 0.19 (mean +/- SE) to 2.78 +/- 0.23 muEq.cm-2h-1 (p less than 0.0001) and in net chloride secretion from 1.57 +/- 0.22 to 2.31 +/- 0.24 muEq.cm-2h-1 (p less than 0.01). There was no change in net sodium movement. Pretreatment with indomethacin (10(-5) M) attenuated, but did not abolish, the increase in short-circuit current. After exposure to MBP, prostaglandin E2 release into the serosal bathing solution increased from 10.0 +/- 4.2 to 17.0 +/- 6.9 ng.cm-2h-1 (p less than 0.05). The results of this study indicate that MBP simulates prostaglandin E2 production and chloride secretion by dog tracheal epithelium. Thus, eosinophils in the airways, through release of MBP, may affect mucociliary clearance by changing the volume and composition of respiratory tract fluid.

Animals↗

PubMed1988

The effects of epithelial cell supernatant on contractions of isolated canine tracheal smooth muscle.

Airway epithelial cells produce mediators that play a role in regulating airway smooth muscle function. This study was designed to examine the effects of epithelial-derived products on contraction of airway smooth muscle. To avoid biochemical and physical changes that may be produced by stripping epithelium from tracheal smooth muscle, we examined the effect of products from pure cultured tracheal epithelial cells on intact dog tracheal smooth muscle. When bradykinin (10(-5) M) was added to dog epithelial cells in culture and the supernatant was added to strips of isolated tracheal smooth muscle, contractile responses to electrical field stimulation were significantly inhibited. Pretreatment of the epithelial cells with indomethacin (5.6 x 10(-6) M) inhibited this effect. Bradykinin placed directly on the canine smooth muscle had no effect on resting tension or on the response to electrical field stimulation. Contractions of the smooth muscle to exogenous acetylcholine were unaffected by supernatants from either indomethacin-treated or untreated cells stimulated with bradykinin (10(-5) M) compared to time controls. We conclude that bradykinin stimulates the release of a cyclooxygenase-dependent inhibitory factor from airway epithelial cells. This factor is likely to be prostaglandin E2, which is generated by the epithelial cells in response to bradykinin stimulation and inhibits smooth muscle contraction induced by electrical field stimulation. Although the mechanism of this inhibition is unknown, the normal response to exogenous acetylcholine is consistent with the hypothesis that prostaglandin E2 acts by inhibiting cholinergic neurotransmitter release at a prejunctional site.

Acetylcholine↗

PubMed1987

Induction of a rapidly responsive hepatic gene product by thyroid hormone requires ongoing protein synthesis.

The regulation of a gene, designated spot 14, which is rapidly induced in rat liver in response to 3,5,3'-triiodo-L-thyronine (T3) was studied as a model for exploring the molecular basis of thyroid hormone action. The time course of induction of the nuclear precursor to spot 14 mRNA after intramuscular injection of T3 displayed a very short lag period of between 10 and 20 min. The rapidity of this effect suggests that the induction in gene expression occurs as a primary response to the hormone-receptor interaction. The protein synthesis inhibitor cycloheximide injected 15 min before T3 completely blocked the accumulation of nuclear precursor RNA 30 min after T3 treatment. Emetine, an inhibitor of protein synthesis which acts by a different mechanism than cycloheximide, also blocked the induction of the spot 14 nuclear precursor RNA. The increased rate of spot 14 gene transcription observed after T3 treatment, as measured by nuclear run-on assay, was similarly completely abolished in the presence of cycloheximide. In addition, ongoing protein synthesis was required for maintaining spot 14 nuclear precursor RNA at induced levels in animals previously treated with T3. On the other hand, cycloheximide had no effect on T3 uptake or binding to the nuclear receptor during the 45-min time frame studied. The paradox of the rapid kinetics of induction and the requirement of ongoing protein synthesis may be explained by a protein with an extremely short half-life which is necessary for T3 induction of the spot 14 gene.

Animals↗

PubMed1987

Regulation of chloride secretion in dog tracheal epithelium by protein kinase C.

The effects of stimulating protein kinase C on Cl- secretion across dog tracheal epithelium were investigated. The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), and the synthetic diacylglycerol, 1-oleolyl-2-acetylglycerol (OAG), which stimulate protein kinase C (PKC), both stimulated short-circuit current (Isc) with Kd of 10 nM and 1 microM, respectively. In Cl(-)-free solution, the increases in Isc were virtually abolished, suggesting that these compounds stimulate Cl- secretion, a hypothesis confirmed for TPA by measurement of 36Cl- fluxes. The stimulations of Cl- secretion were not sensitive to indomethacin, nor were cAMP levels elevated during stimulation. In addition to its transient stimulatory effect, TPA at high doses caused the eventual lowering of the base-line Isc and a block of subsequent stimulation by cAMP-mediated agonists. This was probably not the result of toxicity or an effect on adenylate cyclase or on cAMP-dependent protein kinase. Cell extracts from both cultured and native dog tracheal epithelial cells showed strong PKC activities. These results suggest that PKC may play a role in regulating Cl- secretion across dog tracheal epithelium.

1-Methyl-3-isobutylxanthine↗

PubMed1986

Ion transport across cat and ferret tracheal epithelia.

Sheets of trachea from ferret and cat were mounted in Ussing chambers and continuously short circuited. Under resting conditions, in both the cat and ferret there was little or no Cl secretion, and Na absorption accounted for most of the short-circuit current (Isc). Ouabain (10(-4) M, serosal bath) reduced Isc to zero in 30-60 min. This decline was matched by a decrease in net Na absorption. Amiloride (10(-4) M, luminal bath) caused a significant decrease in Isc and conductance (G) in both species. Bumetanide (10(-4) M, serosal bath) had negligible effects on Isc and G. In both species, isoproterenol increased Isc by stimulating Cl secretion. Methacholine induced equal amounts of Na and Cl secretion, with little change in Isc. In the cat, prostaglandins E2 and F2 alpha and bradykinin increased Isc, responses which were abolished in Cl-free medium. In open-circuited cat tissues, Na flux from the serosal to mucosal side was measured simultaneously with the secretion of nondialyzable 35S. Prostaglandins E1, E2, and F2 alpha, histamine, bradykinin, methacholine and isoproterenol all increased both Na and 35S-mucin secretion.

Amiloride↗

PubMedDate not supplied

Eosinophil-associated inflammation in bronchial asthma: a connection to the nervous system.

Evidence exists that eosinophil cationic proteins damage respiratory epithelium in bronchial asthma. Furthermore, the degree of eosinophilia in the blood and the lung is related to bronchial hyperreactivity. The eosinophil might increase airway irritability by increasing vagal responsiveness. Sensitized challenged guinea pigs develop M2 muscarinic receptor cholinergic dysfunction which is abolished by injection of heparin or polyglutamate and both the eosinophil granule major basic protein and the eosinophil peroxidase act as allosteric M2 receptor antagonists. Thus, eosinophil-associated pulmonary inflammation in asthma may enhance vagally mediated bronchoconstriction.

Animals↗