D. A. Rickaby

Alkaline Serine Proteinase from Aspergillus fumigatus Has Synergistic Effects on Asp-f-2-Induced Immune Response in Mice

Background: Exposure to Aspergillus fumigatus allergens results in the sensitization and the development of allergic bronchopulmonary aspergillosis in susceptible individuals. Aspergillus antigen consists of a number of chemically diverse components and their cumulative or synergistic effect may result in disease. When mice were challenged with individual recombinant allergens, there was only reduced inflammation and immunological responses compared to the whole antigen. Various enzymes identified from A. fumigatus have been thought to cause airway damage. In the present study, we evaluated the effect of exposure to Asp f 13, an alkaline serine proteinase, and Asp f 2 in mice. Methods: BALB/c mice were challenged intranasally with Asp f 2 and Asp f 13 alone and in combination. The antibody response, pulmonary inflammation, and airway hyperreactivity were studied. Results: Results demonstrated no major difference in antibody response and airway responses among the different groups. The inflammatory responses in the lungs, however, showed marked differences in the various groups. Conclusion: In spite of the similar immunological responses in the different groups of mice studied, the results demonstrate enhanced inflammation in the lungs of mice exposed to a combination of both allergens. Allergens with proteinase activity have been found to be involved in airway inflammation and remodeling, which may also apply for Aspergillus-induced allergy.

Immune Response and Airway Reactivity in Wild and IL–4 Knockout Mice Exposed to Latex Allergens

Background: Natural rubber latex has been reported as a major cause of allergy and asthma in a number of individuals. One of the occupational groups most affected by latex allergy are the health care workers who are frequently exposed to natural rubber latex products in their patient care activities. The immunopathogenesis of latex allergy is not well understood. In order to understand the immune mechanism in latex allergy, we have developed a mouse model of latex allergy. Methods: Both wild–type and IL–4 knockout BALB/c mice were challenged intranasally with latex proteins and their immune responses, lung pathology, and airway reactivity were evaluated. Results: The total serum IgE and latex specific IgE, IgG1, and peripheral blood and lung eosinophil levels in wild type BALB/c mice were enhanced by the latex exposure, while no IgE or eosinophil were detected in IL–4 knockout mice. Latex–specific IgG1 levels in the sera were lower in IL–4 knockout animals compared to wild mice. However, latex–specific IgG2a antibody was higher in all the IL–4 knockout mice compared to wild type mice. Both the wild type and IL–4 knockout animals developed increased airway resistance after antigen challenge when compared to control animals, although the airway resistance response of IL–4 knockout animals was attenuated compared to the wild–type animals. The histology of the lungs of these two groups of animals was similar. Conclusion: In spite of the differences in the immune responses in the two groups of mice, there were comparable lung inflammatory responses, suggesting a multifactorial pathogenetic mechanism.

A Murine Model of Latex Allergy-Induced Airway Hyperreactivity

Abstract. Sensitization to latex proteins can cause immediate IgE mast cell-mediated reactions. Health care workers have been found to be particularly at risk because of high exposure. Latex allergy can be produced in mice as demonstrated by IgE and eosinophil responses. Thus the mouse is a potential animal model for studying this disease, but the airway response to latex sensitization in mice has not been evaluated previously. In the present study, we immunized BALB/c mice intranasally with nonammoniated latex proteins. Animals were anesthetized, and lung mechanics were evaluated plethysmographically. Changes in pulmonary conductance (GL) and compliance (Cdyn) were measured in response to a nonspecific challenge with methacholine or to a direct challenge with intravenous latex antigen. Latex sensitization resulted in elevated levels of IgE and latex-specific IgG1 as well as interstitial infiltrates consistent with an allergic response. The methacholine dose-response ED50 for GL was 116.4 μg for the control mice and fell significantly to 20.9 μg for latex-sensitized mice. The ED50 calculated for Cdyn was also significantly lower after latex sensitization. The GL in latex-sensitized mice challenged with latex antigen fell significantly from a prechallenge value of 1.87 ± 0.41 (S.E.) to 0.198 ± 0.03 ml · s−1· cmH2O after latex antigen challenge. The results indicate that latex-sensitized mice did exhibit increased airway reactivity in the methacholine challenge test. The latex allergic response in mice is unique in that direct challenge with latex antigen itself also resulted in a significant airway response.

A mathematical model of indicator extraction by the pulmonary endothelium via saturation kinetics

Abstract When a bolus containing a nonpermeating indicator and an indicator which permeates the endothelial cell membrane by a saturable process is injected into the blood flowing into the lung, the instantaneous extraction ratio curves measured in the pulmonary venous outflow are asymmetric with respect to the nonpermeating indicator curve. If the bolus contains a sufficient quantity of the permeating indicator that the capillary concentration begins to saturate the transfort mechanism, the extraction ratio curves are concave upward as well. The purpose of this study was to determine whether a mathematical model which represents endothelial extraction by Michaelis-Menten kinetics could explain the time variation in the instantaneous extraction ratio curves. The venous concentration curves were assumed to be the result of the endothelial transfort and distributed capillary input and transit times. In addition, we evaluated a method for estimating the kinetic parameters ( K m and V max ) of the saturable transfort process in such an organ. The results of simulations indicate that the important features of the data can be reproduced by the model, and that useful estimates of the kinetic parameters will be obtained from linear multiple regression analysis of the venous concentration curves if the standard deviation of the capillary input time distribution is not less than that of the capillary transit time distribution.

The vascular site of action of hypoxia in the neonatal pig lung.

ABSTRACT: To determine the vascular site(s) of action of hypoxia in the neonatal pig, isolated lungs were perfused at a constant flow rate and left atrial pressure; arterial, venous, and double occlusions were performed. The distribution of the total pulmonary vascular resistance and the total dynamic vascular compliance were calculated using a model of the pulmonary circulation consisting of upstream, central, and downstream compliances and resistances upstream and downstream of central compliance. In addition, the static vascular compliance was measured by venous followed by arterial occlusion, and the total vascular volume was measured by dye-dilution. In this preparation during control conditions alveolar Po2 = 12 ± 2 kPa), total pulmonary vascular resistance was nearly evenly divided between resistance upstream and downstream of double occlusion pressure and total dynamic vascular compliance was concentrated mainly in the central compliance (7% upstream compliance, 82% central compliance, and 11% downstream compliance). Hypoxia (alveolar Po2 = 4 ± 1 kPa) increased both resistance upstream of double occlusion pressure (p < 0.005) and resistance downstream of double occlusion pressure (p < 0.02) and decreased central compliance (p < 0.005). Hypoxia also decreased total pulmonary blood volume (p < 0.02). These results suggest that in the pulmonary vasculature of the neonatal pig, hypoxia results mainly in 7) arterial constriction as evidenced by a large increase in upstream resistance and a decrease in total pulmonary blood volume and 2) a smaller but significant venous constriction. This venous constriction may have implications in the pathogenesis and therapy of pulmonary vascular diseases associated with hypoxia such as postasphyxiai lung disease and bronchopulmonary dysplasia.

Kinetics of serotonin uptake in the intact lung

The pulmonary endothelium is capable of removing and metabolizing serotonin (5HT) carried in the venous blood. Thus the lungs can influence the arterial concentrations of 5HT. In addition, there is evidence that changes in the lung uptake of 5HT might portend more serious endothelial damage wherein the barrier function of the endothelium is compromised. This has been a stimulus for finding methods for evaluating these endothelial functions. These methods must be able to distinguish changes in whole organ function which result from changes in perfusion (e.g., cardiac output, redistribution of flow, etc.) from those resulting from changes in the function of the endothelial cells. When a bolus containing radio-labeled 5HT and an unmetabolizable indicator which is confined to the vascular space is injected into the pulmonary artery, the pulmonary venous or systemic arterial concentration curves contain information about both the convective transport and endothelial cell process involved. Some of this information can be interpreted quantitatively using a simple mathematical model.

Influence of plasma protein on the inhibitory effects of indocyanine green and bromcresol green on pulmonary prostaglandin E1 extraction

1 The purpose of this study was to examine the influence of plasma protein on the inhibitory effects of the anionic dyes indocyanine green and bromcresol green on prostaglandin E1 (PGE1) uptake by the lungs. 2 Dog lung lobes were isolated and perfused with either autologous plasma or Krebs‐Ringer bicarbonate solution (KRB) containing no protein but with dextran used as a colloid. 3 PGE1 uptake was determined by injecting a bolus, containing radiolabeled PGE1 into the lobar artery and then analysing ethanolic extracts of the venous effluent for radioactivity in PGE1 and PGE1 metabolites by thin layer chromatography and scintillation counting. 4 When the lobes were perfused with KRB, bromcresol green at an average initial concentration of 28.5 μm, reduced PGE1 by an average of 56%. When the lobes were perfused with plasma, similar concentrations of bromcresol green reduced the uptake by less than 2%. 5 A similar result was obtained with indocyanine green, which at an average initial concentration of 17.5 μm reduced uptake by about 70% when the lobes were perfused with KRB, but when the lobes were perfused with plasma similar concentrations of the dye reduced uptake by less than 3.5%. 6 The results suggest that plasma protein binding interferes with the inhibitory effects of these dyes on PGE1 uptake in the lungs.

Gastro-intestinal exposure to latex antigens induce allergic responses in mice

Background: Natural rubber latex (NRL) has emerged as a major cause of respiratory allergy among specific exposed groups of individuals. Since latex allergens are dispersed in the environment it is conceivable that latex proteins are both inhaled and ingested. The mechanism of latex allergy and the immune responses following reexposure of latex allergens by the intranasal route was studied in a murine model of latex allergy developed by intragastric sensitization with NRL. Methods:BALB/c mice were sensitized intragastrically (‘ig’), intranasally (‘in’) or ‘ig’ followed by ‘in’ challenge with NRL allergens. The cellular and humoral immune responses, lung function and histological changes were determined. Results: Peripheral blood eosinophilia was observed in the ‘ig’ and ‘ig/in’-NRL-sensitized animals in comparison to normal controls (p < 0.05). The ‘ig’ group showed a marked increase over control mice in serum total IgE, NRL-specific IgG and IgG subclasses (p < 0.05). Increased levels of IL-4, IL-5, IL-10, and IL-13 were detected in ‘ig’-NRL-sensitized mice. Intranasal exposure with NRL after ‘ig’ sensitization further enhanced the cytokine levels. A tendency towards enhanced stimulation was determined in ‘ig’-sensitized mice; a significant difference was shown in the ‘ig/in’-group (p < 0.05). Increased airway hyperreactivity was found in ‘ig’-NRL-sensitized-mice (15.1 ± 2.5 vs. 8.9 ± 1.7 cm H2O·ml–1·s, p < 0.05). Mucus secretion from jejunal epithelium and eosinophilic infiltration into the jejunal lamina propria were observed in the ‘ig’-NRL-sensitized-mice. Conclusions:The results demonstrate that intragastric NRL sensitization did not induce specific tolerance, and additional intranasal exposure with latex allergens resulted in systemic allergic manifestations in the murine model.

Sites of Vasoactivity in the Pulmonary Circulation Evaluated Using a Low-Viscosity Bolus Method

Because of the importance of pulmonary capillary pressure in the fluid balance of the lungs and the propensity for various pulmonary vasomotor stimuli to cause constriction of pulmonary veins (Dawson, 1984), there has been considerable interest in methods for determining pulmonary capillary pressure and the arteriovenous sites of pulmonary vasoconstriction. A number of approaches have been used, and each approach has had advantages and disadvantages (Agostoni and Piiper, 1962; Bhattacharya and Staub, 1980; Brody et al., 1968; Bronikowski et al., 1985; Dawson et al., 1988; Gaar et al., 1967; Gable and Drake, 1978; Kadowitz et al., 1975; McDonald and Butler, 1967; Michel et al., 1984; Nagasaka et al., 1984; Piiper, 1970; Zhuang et al., 1983). Like several other methods, the low-viscosity bolus method has been an experimental method used in studies of pump-perfused lungs. In such studies it has the potential for providing some unique insights into the influence of vasomotion on the longitudinal distribution of pulmonary vascular resistance and intravascular pressure from pulmonary artery to pulmonary veins. The method, originally introduced by Piiper (1970), has been modified by Brody et al. (1968) and Grimm et al. (1977) and more recently by us (Dawson et al., 1988) in an attempt to improve resolution to take advantage of this potential.

Kinetics of Serotonin Uptake by the Dog Lung Is pH Independent in the Physiological Range

Abstract Given the strong pH dependence of platelet serotonin uptake, the many similarities between platelet and pulmonary endothelial serotonin uptake and the potential importance of a pH dependence on the interpretation of changes in pulmonary endothelial serotonin uptake in diseased lungs, we examined the influence of pH on the kinetics of serotonin uptake in isolated dog lung lobes using a multiple indicator technique. A range of pH values from about 7.2 to 8.0 were obtained by ventilating the lobes with gas containing different concentrations of CO2. Over the pH range studied, no significant changes in serotonin uptake were observed, nor were significant changes detected in the kinetic parameters, K m and V max, for the uptake process. The lack of a significant pH effect represents a difference between platelet and lung endothelial serotonin uptake. It also indicates that correlations between P CO2 and serotonin uptake which might occur in diseased lungs do not imply causality.