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Biomedical subjects

R Burrell

Publications and source records attributed to R Burrell.

At least 37 records · Page 2Linked to original sources
PubMed1981

Acute-phase reactants in experimental inhalation lung disease.

An investigation on the occurrence and role of acute-phase reactants in experimental inhalation lung disease (ILD) was undertaken. Using an experimental model of ILD in which rabbits are exposed to aerosols of appropriate fungal spores, haptoglobin analysis was compared with depressions in arterial oxygen tension (PaO2) with time following challenge. Haptoglobin values of rabbits exposed to single 30-min aerosol challenges of Aspergillus terreus, demonstrated a significant (two- to three fold) increase 24-48 hr after challenge. Haptoglobin elevation was found to be a more reliable and consistent indicator of pulmonary inflammation than depression of PaO2. In an effort to determine the role of haptoglobin in this response, acute phase reactant levels were elevated either actively or passively. When rabbits with augmented haptoglobin levels were exposed to aerosol challenges with A. terreus, the typical depressions in PaO2 at 1-4 hr postchallenge were not observed. This indicated the plasma containing elevated acute-phase reactants may be involved in limiting the pulmonary response that normally occurs following challenge. Haptoglobin was not found to bind to A. terreus spores in vitro.

Aerosols↗
PubMed1980

Mitogenic response to Micropolyspora faeni cell walls.

Three cell wall fractions, prepared from Micropolyspora faeni, were shown to be mitogenic for the splenic lymphocytes of unsensitized guinea pigs. This response peaked after 48 hr in culture and was dose dependent. Using enriched lymphocyte subpopulations obtained by column-separation techniques, it was shown that the most active cell wall fractions were primarily B cell mitogens. Physical, chemical, and enzymatic digestion studies indicated that the heat-stable mitogenic reactivity was associated with polypeptide and polysaccharide. The reactive material is, at least in part, peptidoglycan, as shown by the decrease in its mitogenic potential after lysozyme digestion. A possible host-related role for this mitogenic reactivity was discussed.

Animals↗
PubMed1978

Complement activation by cell wall fractions of Micropolyspora faeni.

The ability of several cell wall fractions of Micropolyspora faeni, a thermophilic actinomycete associated with farmer's lung disease, to activate complement is reported. Cell walls, obtained by mechanical disruption, were purified by enzyme treatment and chemical extractions. Fractions containing the most purified cell walls were most active in consuming complement, as measured by reduction of hemolytic complement levels of normal human serum. Cell wall fractions activated the alternative complement pathway, as shown by monitoring the conversion of C3 proactivator (factor B) to C3 activator (activated factor B) in the presence of specific cation chelators. Selective degradation of cell walls by lysozyme resulted in a decreased ability to consume complement and implicated peptidoglycan as the major complement-reactive component. The role of this nonspecific complement activation in relation to farmer's lung disease is discussed.

Cell Wall↗
PubMed1978

Mitogenicity of cell wall fractions of Micropolyspora faeni.

Cell wall fractions of Micropolyspora faeni, a causative agent of hypersensitivity pneumonitis, have been shown to possess non-specific mitogenic activity for guinea pig, rabbit and human lymphocytes. This activity was unrelated to endotoxin and may not be associated with peptidoglycan. This lymphocyte proliferation stimulus may play a role in the adjuvant properties of this organism and in the etiology of hypersensitivity lung disease.

Animals↗
PubMed1977

Production of thermophilic actinomycete-hay aerosols for use in experimental hypersensitivity pneumonitis.

An investigation of the factors that influence the production of dense aerosols of Micropolyspora faeni and Thermoactinomyces vulgaris from hay cultures revealed that the density, freshness, and moisture content of the hay were important influences. Dry aerosols were produced under optimum conditions from hay cultures of either actinomycete and from sterile hay for inhalation challenges to unimmunized rabbits. Depressions in arterial oxygen tensions and hemolytic complement were monitored after such challenge. This investigation showed that hay cultures are capable of inciting a hypersensitivity-like reaction in the lungs, even in the absence of immunization to the organisms contained within the hay, but the entire hypersensitivity reaction cannot be attributed to M. faeni and T. vulgaris alone. Hay itself or other microbial or chemical components appear to have some heat-stable component that possibly contributes to the pathogenesis of the disease.

Aerosols↗
PubMed1977

Improved methods of producing precipitating aspergillus antigens.

Improved methods for producing Aspergillus fumigatus antigens capable of giving sensitive and reproducible results by counterimmunoelectrophoresis (CIEP) are described. Among the factors investigated were the source of casein hydrolysate used for N source, method of incubating the CIEP slide following a run, effect of freeze pressing and lyophilization, age of culture and ratio of C to N source in the medium.

Antigens, Fungal↗
PubMed1977

III. Mediators of allergic reactions. Endogenous and exogenous stimulating or suppressor substances. Mediators of experimental hypersensitivity pneumonitis.

Using a physiologic model of hypersensitivity pneumonitis where depressions of arterial oxygen tension in unimmunized rabbits are monitored following aerosol challenge with Aspergillus terreus spores, attempts were made to assess the nature of the cellular and pharmacologic mediators of the impairment. Unlike normal animals no PaO2 depressions were obtained following aerosol challenge in either rabbits deficient in C6 or in rabbits made thrombocytopenic with antiplatelet serum. Such aerosols were also shown to produce platelet count depressions of up to 45% in normal rabbits. Finally, in vitro evidence of histamine release was obtained following incubation of Aspergillus extract, platelets and autologous serum from unimmunized rabbits. It was concluded that Aspergillus-induced pulmonary disease may be initiated by platelet release of mediators such as histamine stimulated by nonspecific complement activation.

Aerosols↗
PubMed1976

The role of precipitins and complement activation in the etiology of allergic lung disease.

An experimental model of allergic lung disease has been described that is monitored by analysis of arterial oxygen tension following aerosol challenge with antigen. Rabbits immunized to a classical soluble antigen, human serum albumin (HSA), to the point where severe Arthus skin reactivity was demonstrable, were aerosol-challenged with antigen. Arterial oxygen tension measurements made on pre- and post-challenge samples yielded early, late, and continuous response patterns, reminiscent of those obtained in humans following provocation testing. Aerosol challenge of unimmunized animals with HSA resulted in no change from baseline conditions. Unimmunized rabbits exposed to small and massive (10X) aerosols of Aspergillus spores also demonstrated various postchallenge depressions in arterial oxygen tension as well as decreased levels in hemolytic complement activity, depending on the species of fungus and dose of spores used. Unimmunized animals pretreated with cobra venom factor in a manner known to achieve complement depletion failed to respond with altered arterial oxygen tensions following similar aerosol challenge. It is postulated that although precipitins may play a role in artificial disease initiated by soluble antigens, nonspecific complement activation may be more important in understanding the etiology of spontaneous disease in humans brought about by inhalation of moldy particulate matter.

Administration, Intranasal↗
PubMed1976

Induction of fibrogenesis by lung antibody-treated macrophages.

Using a modification of an in vitro model of fibrogenesis, lung connective tissue antibodies have been shown to stimulate macrophages to release a collagen stimulating factor acting on fibroblast target cells. This stimulation was measured by increased hydroxyproline production from fibroblasts that had reached stationary growth phase. In subcytotoxic amounts, this antibody had no such effect directly on fibroblasts. These findings further illustrate the value of studying fibrogenesis by the in vitro method.

Animals↗
PubMed1976

The effect of respiratory immunization on cell-mediated immune effector cells of the lung.

In order to understand the mechanisms of cellular immune injury in hypersensitivity pneumonitis, the effect of type of antigen on cell-mediated immunity in guinea-pigs receiving respiratory immunization was studied. Lymphocytes obtained by pulmonary lavage were compared with those from peritoneal exudate following immunization with either a soluble protein, human serum albumin, or a particulate suspension of Thermoactinomyces vulgaris. Assays were obtained without mixing cells from these two sources. Statistically significant increases (13-22%) in the number of alveolar rosette-forming cells (RFC) were found in the animals immunized with either antigen, but only the particulate T. vulgaris was also capable of inducing a systemic increase of such cells. That this increase in RFC could be due to specifically reactive lymphocytes was demonstrated by the production of antigen-stimulated macrophage migration inhibition. Some evidence was obtained that indicated that T. vulgaris could act both as a non-specific B-cell stimulant and a specific T-cell activator. The concept of a hypothetical pulmonary 'barrier' is discussed which must be overcome to induce systemic immune responses following respiratory immunization. T. vulgaris must be added to the list of known agents or means for overcoming this 'barrier'.

Aerosols↗
PubMed1975

Effects of clonidine on baroreceptor function in anesthetized dogs.

The effects of clonidine (15-30 mug/kg i.v.) on carotid sinus and other baroreceptors were investigated in anesthetized dogs. In 14 control dogs, right carotid sinus pressure was controlled by retrograde perfusion through the common carotid artery at constant flow with femoral arterial blood. Graded reductions in heart rate and blood pressure induced by graded increases in carotid sinus pressure were prevented, whereas reflex bradycardias associated with norepinephrine pressor activity were potentiated by clonidine. Norepinephrine-induced bradycardia, although reduced, still persisted after chronic bilateral sinusectomy and these responses were also potentiated by clonidine. In contrast, clonidine did not potentiate reflex bradycardia in dogs 20 days after aortic stripping. In intact dogs, clonidine inhibited the response to bilateral carotid artery occlusion and to carotid sinus nerve stimulation. These studies suggest that clonidine can inhibit carotid sinus baroreceptor function and simultaneously potentiate other, presumably aortic, baroreceptor activity.

Anesthesia↗