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Biomedical subjects

D Sheppard

Publications and source records attributed to D Sheppard.

At least 109 records · Page 6Linked to original sources
PubMed1990

Complete amino acid sequence of a novel integrin beta subunit (beta 6) identified in epithelial cells using the polymerase chain reaction.

The integrin family of adhesion receptors consists of several heterodimeric glycoproteins, each composed of one alpha and one beta subunit. Three different mammalian beta subunits, beta 1, beta 2, and beta 3, have been sequenced, but recent evidence suggests the existence of several others. Amplification of guinea pig airway epithelial cell cDNA with oligonucleotide primers designed to recognize consensus integrin beta subunit sequences led to the identification of a novel partial cDNA sequence. Clones containing portions of this sequence were used to screen cDNA libraries constructed from the human pancreatic carcinoma cell line FG-2 and identified a series of overlapping clones encoding the full-length sequence of the human homologue of this protein. This sequence of 788 amino acids is 43, 38, and 47% identical to the sequences of beta 1, beta 2, and beta 3, respectively. Features shared between this novel protein and the previously sequenced beta subunits include the positions of all 56 cysteine residues in the extracellular domain, the single putative transmembrane domain, and the short putative cytoplasmic domain. However, a unique 11-amino acid extension at the carboxyl terminus, not present in any of the other beta subunits, is suggestive of distinctive interactions with cytoplasmic components. Comparison of the human and guinea pig sequences reveals a high degree (94%) of cross-species conservation. Because this protein is clearly distinct from the two other recently described integrins beta 4 and beta 5, we propose to designate it beta 6.

Amino Acid Sequence↗
PubMed1990

Acid fog-induced bronchoconstriction. The role of hydroxymethanesulfonic acid.

Hydroxymethanesulfonate (HMSA), the bisulfite (HSO3-) adduct of formaldehyde (CH2O), is a common constituent of California acid fogs. HMSA, most stable in a fog pH range of 3 to 5, dissociates at 6.6, the pH of the fluid lining human airways. The dissociation of inhaled HMSA should theoretically generate sulfur dioxide and CH2O, both of which have bronchoconstrictor potential. Thus, we hypothesized that HMSA may have a specific bronchoconstrictor effect independent of its strength as an acid. To determine whether HMSA has such an effect, 19 subjects with mild to moderate asthma were studied using two different protocols. Initially, a mouthpiece study was performed in which 9 subjects, on 2 separate days, inhaled five aerosols containing either sequentially increasing concentrations (0, 30, 100, 300, and 1000 microM) of HMSA in 50 microM sulfuric acid (H2SO4) or 50 microM H2SO4 alone. The subjects inhaled each aerosol for 3 min during tidal breathing at rest. Specific airway resistance (SRaw) was measured before and after each 3-min exposure. There were no significant differences in the mean changes in SRaw among the various aerosol exposures. To confirm this lack of bronchoconstrictor effect of HMSA, we then performed a chamber study in which 10 freely breathing, intermittently exercising subjects were exposed to fog containing either 1 mM HMSA in 5 mM H2SO4 or 5 mM H2SO4 alone for 1 h. SRaw was measured before, during, and at the end of the 1-h exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1989

Epithelium removal alters responsiveness of guinea pig trachea to substance P.

Removal of epithelium from mammalian tracheae has been shown to enhance responsiveness to a variety of contractile and relaxant agents. One of the most dramatic shifts reported has been for guinea pig tracheal tissue denuded of epithelium and treated with substance P. We investigated whether this shift in responsiveness was because of 1) removal of an epithelium-associated enzyme, neutral endopeptidase, which degrades substance P and 2) loss of an epithelium-derived noncyclooxygenase relaxant factor. Using a muscle bath preparation we performed concentration-response curves with substance P and acetylcholine on indomethacin-treated tissues with and without intact epithelium and with and without pretreatment with the neutral endopeptidase inhibitor, phosphoramidon. Epithelium removal potentiated the mean agonist concentration calculated to causes 30% of the maximal contractile response by 148-fold for substance P and by 7-fold for acetylcholine. Phosphoramidon potentiated the contractile response to substance P, but not to acetylcholine, by both the epithelium-intact and denuded tissues (P less than 0.05). However, the degree of enhancement by phosphoramidon was much greater in the intact tissues. With phosphoramidon treatment, therefore, the difference in responsiveness to substance P between the intact and denuded tissues was reduced from 148-fold to 18-fold. This effect of phosphoramidon suggests that the hyperresponsiveness to substance P of epithelium-denuded airway tissue is largely because of removal of neutral endopeptidase. Because all tissues were treated with indomethacin, the leftward shifts in substance P and in acetylcholine responsiveness induced by epithelium removal further suggest that an epithelium-derived noncyclooxygenase factor other than neutral endopeptidase also modulates the contractile response to substance P and to acetylcholine.

Acetylcholine↗
PubMed1989

Potential bronchoconstrictor stimuli in acid fog.

Acid fog is complex and contains multiple stimuli that may be capable of inducing bronchoconstriction. These stimuli include sulfuric and niric acids, the principal inorganic acids present; sulfites, formed in the atmosphere as a reaction product of sulfur dioxide and water droplets; fog water itself, a hypoosmolar aerosol; the organic acid hydroxymethanesulfonate, the bisulfite adduct of formaldehyde; and gaseous pollutants, e.g., sulfur dioxide, oxides of nitrogen, ozone. Given this complexity, evaluation of the respiratory health effects of naturally occurring acid fog requires assessment of the bronchoconstrictor potency of each component stimulus and possible interactions among these stimuli. We summarize the results of three studies that involve characterization of the bronchoconstrictor potency of acid fog stimuli and/or their interaction in subjects with asthma. The results of the first study indicate that titratable acidity appears to be a more important stimulus to bronchoconstriction than is pH. The results of the second study demonstrate that sulfite species are capable of inducing bronchoconstriction, especially when inhaled at acid pH. The results of the third study suggest that acidity can potentiate hypoosmolar fog-induced bronchoconstriction.

Acid Rain↗
PubMed1988

Arachidonic acid metabolites do not mediate toluene diisocyanate-induced airway hyperresponsiveness in guinea pigs.

Arachidonic acid metabolites have previously been demonstrated to mediate the airway hyperresponsiveness observed in guinea pigs and dogs after exposure to ozone. Guinea pigs were treated with indomethacin (a cyclooxygenase inhibitor), U-60,257 (piriprost, a 5-lipoxygenase inhibitor), or BW775c (a lipoxygenase and cyclooxygenase inhibitor) and exposed to air or 3 ppm TDI. Airway responsiveness to acetylcholine aerosol was examined 2 h after exposure. In control animals, the provocative concentration of acetylcholine which caused a 200% increase in pulmonary resistance over baseline (PC200) was significantly less (p less than 0.05) after exposure to TDI (8.6 +/- 2.0 mg/ml, geometric mean + geometric SE, n = 10) than after exposure to air (23.9 + 2.5 mg/ml, n = 14). The airway responsiveness to acetylcholine in animals treated with indomethacin or piriprost and exposed to TDI was not different from that of control animals exposed to TDI. Treatment with BW755c enhanced the airway hyperresponsiveness observed in animals exposed to TDI without altering the PC200 of animals exposed to air. The PC200 of animals treated with BW755c and exposed to TDI (2.3 + 0.8 mg/ml, n = 8) was significantly lower than the PC200 of control animals exposed to TDI (p less than 0.025). These results suggest that products of arachidonic acid metabolism are not responsible for TDI-induced airway hyperresponsiveness in guinea pigs. BW755c, however, appears to potentiate the TDI-induced airway hyperresponsiveness to acetylcholine by an as yet unidentified mechanism.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1988

Mechanisms of acute increases in airway responsiveness caused by environmental chemicals.

Inhalation of inhaled environmental chemicals has long been recognized as a cause of acute increases in airway responsiveness. Extensive studies of the mechanisms of action of two of these chemicals, ozone and toluene diisocyanate, have been conducted during the past decade. The results of these studies suggest that acute airway inflammation plays an important role in the effect of inhaled chemicals but that the specific aspects of the inflammatory response that lead to the development of airway hyperresponsiveness are different for different stimuli and among different mammalian species. These observations suggest that in vivo airway hyperresponsiveness can arise via several different mechanisms and is thus not likely to reflect a single underlying defect.

Air Pollutants↗
PubMed1988

Tumor necrosis factor inhibits a polymorphonuclear leukocyte-dependent airway edema in guinea pigs.

Intravenously administered endotoxin inhibits the polymorphonuclear leukocyte (PMN)-dependent airway edema produced in guinea pigs exposed to toluene diisocyanate (TDI). Tumor necrosis factor (TNF) is produced in vivo by peripheral blood monocytes and tissue macrophages stimulated with endotoxin and has been shown to activate PMN's and vascular endothelial cells. To determine whether the inhibition of airway edema is mediated by TNF, guinea pigs were treated with intravenous saline or 75,000 U/kg recombinant human TNF 1.5 h before exposure to air or 3 ppm TDI for 1 h. Animals were then injected intravenously with 50 mg/kg Evans blue dye as a marker of protein extravasation. Saline-treated animals exposed to TDI had a significant increase in tracheal Evans blue dye extravasation (85 +/- 6.5 micrograms dye/g trachea, mean +/- SE) compared with saline-treated animals exposed to air (31.3 +/- 2.5, P less than 0.001). The tracheal extravasation of Evans blue dye was significantly inhibited (P less than 0.05) in TDI-exposed animals treated with TNF (64.7 +/- 7.5). Neither heat-inactivated TNF (104.9 +/- 9.5) nor TNF neutralized with a monoclonal antibody against TNF (99.7 +/- 17.9) inhibited TDI-induced airway edema. In addition, treatment with 15,000 U/kg (99.9 +/- 21.3) or 150,000 U/kg (103.2 +/- 17.6) interleukin 1, a monokine also produced in response to endotoxin, did not prevent airway edema. These results suggest that TNF released in response to endotoxin mediates endotoxin's inhibition of a PMN-dependent airway edema.

Animals↗
PubMed1988

Phosphoramidon potentiates the increase in lung resistance mediated by tachykinins in guinea pigs.

This study was designed to evaluate the role of endogenous enkephalinase in regulating bronchoconstrictor responses in guinea pigs. We evaluated the effects of phosphoramidon, an enkephalinase inhibitor, on the increases in lung resistance (RL) caused by exogenous substance P and inhaled capsaicin (an agent thought to provoke bronchoconstriction in guinea pigs by stimulating the release of tachykinins from afferent nerve endings). In 6 of 6 animals, phosphoramidon potentiated the substance P-induced increase in RL (RL increased 380 +/- 100% [mean +/- SEM] before phosphoramidon and 1,300 +/- 400% afterward, p less than 0.025). In 4 of 4 animals, the repeated administration of a single dose of substance P after saline did not result in potentiation of the increase in RL caused by substance P. Similarly, in 6 animals exposed to inhaled capsaicin, phosphoramidon significantly increased capsaicin responsiveness when compared to 6 capsaicin-exposed animals not treated with phosphoramidon. Phosphoramidon-induced augmentation of the airway responsiveness to substance P and to capsaicin was not simply the result of a nonspecific increase in airway smooth muscle responsiveness because phosphoramidon failed to potentiate the bronchoconstrictor response to inhaled acetylcholine. These results suggest the enkephalinase plays an important role in modulating in vivo bronchoconstrictor responses to substance P in guinea pigs. Therefore, alterations in enkephalinase activity could contribute to in vivo alterations in bronchoconstrictor responsiveness.

Acetylcholine↗
PubMed1988

Acidity potentiates bronchoconstriction induced by hypoosmolar aerosols.

Naturally occurring fogs are usually hypoosmolar with respect to body fluids and can be quite acidic. Because both hypoosmolarity and acidity can cause bronchoconstriction, we studied whether there was a positive interaction between these stimuli in 12 subjects with asthma. We administered the following aerosols: hypoosmolar saline (30 mOsm) at pH 5.5, 3 hypoosmolar acids (0.005 M H2SO4, 0.01 M HNO3 and a 1:1 mixture of 0.005 M H2SO4 and 0.01 M HNO3, all 30 mOsm) at pH 2, and isoosmolar 0.005 M H2SO4 (300 mOsm) at pH 2. Each aerosol was administered on a separate day and was inhaled through a mouthpiece during tidal breathing. Specific airway resistance (SRaw) was measured before and after the subjects inhaled aerosols delivered at as much as 5 doubling nebulizer outputs. For each aerosol challenge, an output-response curve was generated, and the nebulizer output required to increase SRaw by 100% above baseline (PO100) was calculated. Mean values of PO100 were significantly lower for each of the hypoosmolar acids than for hypoosmolar saline (1.65 + 0.43 g/min [mean + SEM] for saline compared with 0.95 + 0.11, 1.05 + 0.20, and 0.90 + 0.14 for H2SO4, HNO3, and a 1:1 mixture of the two; all p values less than 0.025). Mean values of PO100 did not differ among the 3 acids studied. For 7 of 12 subjects, all 3 acids caused a leftward shift in the output-response curve from the curve generated for hypoosmolar saline aerosol. Isoosmolar H2SO4 did not increase SRaw by 100% in any subjects, even at the maximal nebulizer output that delivered a concentration of H2SO4 in excess of 40 mg/m3.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

A tachykinin receptor antagonist inhibits and an inhibitor of tachykinin metabolism potentiates toluene diisocyanate-induced airway hyperresponsiveness in guinea pigs.

We have previously shown that tachykinin depletion or antagonism prevented the increase in airway responsiveness to inhaled acetylcholine caused by exposure to toluene diisocyanate (TDI) in awake guinea pigs. To insure that the effects of tachykinins were not limited to the extrathoracic airways and were not dependent on effects of TDI on baseline airway caliber, we determined airway responsiveness to acetylcholine inhaled through a tracheostomy in anesthetized and ventilated guinea pigs that were exposed to TDI or air after treatment with the tachykinin antagonist spantide, the tachykinin metabolism inhibitor phosphoramidon, or the vehicles for each drug. When these drugs were administered before and during TDI exposure, spantide significantly inhibited the TDI-induced increase in acetylcholine responsiveness and phosphoramidon significantly potentiated this effect, whereas neither drug altered acetylcholine responsiveness in air-exposed animals. To determine whether tachykinins were exerting their effect primarily during TDI exposure or during the subsequent acetylcholine challenge, we also examined the effect of each drug on acetylcholine responsiveness when the drugs were given after TDI exposure. At that time, spantide did not inhibit TDI-induced acetylcholine hyperresponsiveness and phosphoramidon did not potentiate it. Neither drug nor TDI increased pulmonary resistance measured through a tracheostomy in these anesthetized and ventilated animals. These results suggest that the TDI-induced increase in acetylcholine responsiveness is mediated by release of tachykinins into the intrathoracic airways during exposure to TDI.

Acetylcholine↗
PubMed1988

Toluene diisocyanate increases airway responsiveness to substance P and decreases airway neutral endopeptidase.

Substance P and related tachykinins contribute to the airway hyperresponsiveness caused by toluene diisocyanate (TDI) in guinea pigs. Neutral endopeptidase (NEP) is an important modulator of substance P-induced responses. To test the hypothesis that exposure to TDI would increase responsiveness to substance P by inhibiting activity of this enzyme, we determined the dose of substance P required to increase pulmonary resistance by 200% above baseline (PD200) before and after administration of the pharmacologic inhibitor phosphoramidon in guinea pigs studied 1 h after a 1-h exposure to air or 3 ppm TDI. TDI exposure increased responsiveness to substance P significantly. However, phosphoramidon caused a significantly greater leftward shift of the substance P dose-response curve in air-exposed animals than it did in TDI-exposed animals, so that after phosphoramidon, mean values of PD200 in animals exposed to air or TDI did not differ. Tracheal NEP activity was significantly less after exposure to TDI than after exposure to air, whereas activity in the esophagus was the same in both groups. These results suggest that TDI exposure increases the bronchoconstrictor responsiveness of guinea pigs to substance P, in large part through inhibition of airway NEP.

Airway Resistance↗
PubMed1988

Equivalence of continuous flow nebulizer and metered-dose inhaler with reservoir bag for treatment of acute airflow obstruction.

Traditionally, patients with acute airflow obstruction are treated with bronchodilator aerosols delivered by continuous flow nebulizers. While bronchodilator administration with the metered dose inhaler (MDI) and reservoir or spacer attachment is as effective as administration with the nebulizer in most settings, the former has not been widely accepted for treatment of acute airway obstruction in the emergency room. We compared the efficacy of the continuous flow nebulizer to that of the MDI with InspirEase (reservoir spacer) in 75 patients (45 men and 30 women), ages 18-73 (chi 44 years) who presented to the emergency room with acute asthma and COPD. Subjects in each group (22 COPD and 53 asthma) were randomly assigned to treatment with three puffs of metaproterenol (0.65 mg/puff) via the MDI with InspirEase plus nebulizer with placebo, or placebo MDI with InspirEase plus nebulizer with 15 mg metaproterenol in double blind fashion. Either treatment was given three times at 30 min intervals. The FEV1 and dyspnea scores according to the Borg scale were measured at baseline, 30 min after the first treatment, and 30 min after the third. There was no significant outcome difference between the two treatments in either diagnostic group. There also was no significant outcome difference for patients with baseline FEV1 less than 0.9L. Serum theophylline levels, the need for concomitant therapy with corticosteroids, or additional emergency room therapy after the study, hospitalizations and treatment side effects did not differ between treatment groups. We conclude that there is no demonstrable advantage of a continuous flow nebulizer over an MDI with InspirEase for the treatment of acute airflow obstruction.

Adult↗
PubMed1987

Tachykinins mediate the acute increase in airway responsiveness caused by toluene diisocyanate in guinea pigs.

Exposing guinea pigs to toluene diisocyanate (TDI) causes an acute increase in airway responsiveness to inhaled acetylcholine. The mechanism of this increase in airway responsiveness is unknown. Capsaicin-sensitive afferent nerves and the tachykinins they release upon activation are important in controlling bronchomotor tone in guinea pigs. To determine whether tachykinins are important in TDI-induced airway hyperresponsiveness, we studied the effects of tachykinin depletion, using capsaicin, and competitive tachykinin antagonism, using (D-Arg1, D-Pro2, D-Trp7.9, Leu11) substance P, on TDI-induced airway hyperresponsiveness. In 9 of 9 untreated animals, TDI exposure caused a large and significant increase in airway responsiveness to acetylcholine. The mean concentration of acetylcholine required to decrease specific airway conductance by 50% below baseline (the PD50) was 1.51% before TDI exposure and 0.17% after TDI exposure (p less than 0.0005). Capsaicin treatment had no effect on the PD50 but prevented the TDI-induced increase in airway responsiveness in 10 of 12 animals. (The PD50 was 1.03% before TDI and 1.27% after TDI exposure.) Treatment with the tachykinin antagonist (D-Arg1, D-Pro2, D-Trp7.9, Leu11) substance P also abolished the TDI-induced increase in airway responsiveness in all 5 animals treated. Although TDI exposure also causes airway edema, the effect of capsaicin treatment on TDI-induced airway hyperresponsiveness did not result from prevention of airway edema. TDI exposure caused a marked increase in tracheal extravasation of intravenously administered Evans blue dye that was not prevented by capsaicin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1987

Symptomatic bronchoconstriction after short-term inhalation of sulfur dioxide.

We studied the relationship between duration and concentration of exposure in SO2-induced bronchoconstriction in 8 asthmatic subjects. On separate days, we administered SO2 in humidified air through a mouthpiece at 2 concentrations (0.5 and 1.0 ppm) for 3 time periods (1, 3, and 5 min) during eucapnic hyperpnea (60 L/min). Humidified air was administered for 5 min as a control. Bronchoconstriction was assessed by measurement of specific airway resistance (SRaw). The magnitude of the bronchoconstrictor response to both concentrations of SO2 increased progressively over the 3 time periods studied. The mean (+/- SE) increase in SRaw (in L x cm H2O/L/s) and percent increase above baseline (in parentheses) after each exposure to SO2 were as follows: 2.5 +/- 0.3 (34%) after 0.5 ppm for 1 min; 7.5 +/- 4.7 (93%) after 1.0 ppm for 1 min; 13 +/- 3.2 (173%) after 0.5 ppm for 3 min; 31.4 +/- 7.4 (395%) after 1.0 ppm for 3 min; 19.6 +/- 4.0 (234%) after 0.5 ppm for 5 min; 44.1 +/- 9.8 (580%) after 1.0 ppm for 5 min; 3.5 +/- 1.5 (46%) after humidified air for 5 min. For the group, the increases in SRaw caused by inhalation of both concentrations of SO2 for 1 min were small. However, 2 of 8 subjects did develop large increases in SRaw and chest tightness after inhalation of 1.0 ppm for 1 min. Seven of 8 subjects developed wheezing, chest tightness, or dyspnea and used an inhaled bronchodilator after inhalation of 0.5 ppm for 3 and 5 min and 1.0 ppm for 3 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗