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R Robert Schellenberg

Publications and source records attributed to R Robert Schellenberg.

6 recordsLinked to original sources
PubMed2004

On the terminology for describing the length-force relationship and its changes in airway smooth muscle.

The observation that the length-force relationship in airway smooth muscle can be shifted along the length axis by accommodating the muscle at different lengths has stimulated great interest. In light of the recent understanding of the dynamic nature of length-force relationship, many of our concepts regarding smooth muscle mechanical properties, including the notion that the muscle possesses a unique optimal length that correlates to maximal force generation, are likely to be incorrect. To facilitate accurate and efficient communication among scientists interested in the function of airway smooth muscle, a revised and collectively accepted nomenclature describing the adaptive and dynamic nature of the length-force relationship will be invaluable. Setting aside the issue of underlying mechanism, the purpose of this article is to define terminology that will aid investigators in describing observed phenomena. In particular, we recommend that the term "optimal length" (or any other term implying a unique length that correlates with maximal force generation) for airway smooth muscle be avoided. Instead, the in situ length or an arbitrary but clearly defined reference length should be used. We propose the usage of "length adaptation" to describe the phenomenon whereby the length-force curve of a muscle shifts along the length axis due to accommodation of the muscle at different lengths. We also discuss frequently used terms that do not have commonly accepted definitions that should be used cautiously.

Animals↗
PubMed2002

Interleukin-3, but not granulocyte-macrophage colony-stimulating factor and interleukin-5, inhibits apoptosis of human basophils through phosphatidylinositol 3-kinase: requirement of NF-kappaB-dependent and -independent pathways.

Basophils are key effector cells of allergic reactions. Although proinflammatory cytokines, such as interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-5, inhibit eosinophil apoptosis in vitro, little is known about basophil apoptosis, and the signalling mechanisms required for basophil survival remain undefined. To address this issue, we used a novel negative-selection system to isolate human basophils to a purity of > 95%, and evaluated apoptosis by morphology using light and transmission electron microscopy, and by annexin-V binding and propidium iodide incorporation using flow cytometry. In this study, we demonstrated that the spontaneous rate of apoptotic basophils was higher than that of eosinophils as, at 24 hr, 57.6 +/- 4.7% of basophils underwent apoptosis compared with 39.5 +/- 3.8% of eosinophils. In addition, basophil cell death was significantly inhibited when cultured with IL-3 for 48 hr (84.6 +/- 4.9% vehicle-treated cells versus 40.9 +/- 3.9% IL-3-treated cells). IL-3 also up-regulated basophil CD69 surface expression. The effects of IL-3 on apoptosis and CD69 surface expression of human basophils were completely blocked by LY294002 (LY), a potent inhibitor of phosphatidylinositol 3-kinase (PI3-K), but only partially inhibited by lactacystin, a proteasome inhibitor that prevents degradation of IkappaB and NF-kappaB translocation. These observations reveal the novel finding that IL-3 prevents basophil apoptosis through the activation of PI3-K, which is only partially NF-kappaB dependent. As basophils are active participants in allergic reactions and IL-3 is one of the abundant proinflammatory cytokines in secretions from allergic tissue, we suggest that IL-3-mediated inhibition of basophil apoptosis may exacerbate the inflammation associated with allergic disorders.

Antigens, CD↗
PubMed2002

Tissue elastance influences airway smooth muscle shortening: comparison of mechanical properties among different species.

We have observed striking differences in the mechanical properties of airway smooth muscle preparations among different species. In this study, we provide a novel analysis on the influence of tissue elastance on smooth muscle shortening using previously published data from our laboratory. We have found that isolated human airways exhibit substantial passive tension in contrast to airways from the dog and pig, which exhibit little passive tension (<5% of maximal active force versus approximately 60% for human bronchi). In the dog and pig, airway preparations shorten up to 70% from Lmax (the length at which maximal active force occurs), whereas human airways shorten by only approximately 12% from Lmax. Isolated airways from the rabbit exhibit relatively low passive tension (approximately 22% Fmax) and shorten by 60% from Lmax. Morphologic evaluation of airway cross sections revealed that 25-35% of the airway wall is muscle in canine, porcine, and rabbit airways in contrast to approximately 9% in human airway preparations. We postulate that the large passive tension needed to stretch the muscle to Lmax reflects the high connective tissue content surrounding the smooth muscle, which limits shortening during smooth muscle contraction by imposing an elastic load, as well as by causing radial constraint.

Animals↗
PubMed1999

Leukemia inhibitory factor (LIF) and LIF receptor in human lung. Distribution and regulation of LIF release.

The distribution and regulation of leukemia inhibitory factor (LIF) and its receptor (LIFR) in human lung tissue is unknown. We recently found that LIF was immunolocalized to several cell types in human airways, and that exogenous LIF modulated neural and contractile responses of explanted airways. The present study aimed to determine the cellular distribution and regulation of gene transcripts for LIF and LIFR in human lung, and measured the release of LIF in response to anti-immunoglobulin (Ig)E, interleukin (IL)-1beta, and IL-6. Exposure of human lung to IL-1beta (100 pg/ml) resulted in the rapid induction of LIF messenger RNA (mRNA) (1 h) and subsequent protein release (6 h). Similar results were observed when lung tissue was exposed to anti-IgE (6 U/ml). Gene transcripts for LIF were observed in nine pulmonary cell types, with the greatest expression occurring in fibroblasts. LIFR transcripts were also widely expressed in these cell types. In cultures of nontransformed epithelial cells, lung fibroblasts, and airway smooth-muscle cells, IL-1beta (100 pg/ml) induced the rapid accumulation of LIF mRNA and protein release, with fibroblasts liberating the greatest amount. IL-6 also induced the expression of LIF mRNA and release of LIF in airway smooth-muscle cells, whereas exogenous LIF itself had no effect. Expression of LIFR mRNA was not influenced by exposure to IL-1beta or LIF in any of the cell lines used. These results highlight the widespread distribution and rapid release of LIF in human lung tissue and, in conjunction with our previous report, suggest that this cytokine may play an important role in lung inflammatory processes and neuroimmune interactions.

Bronchi↗
PubMedDate not supplied

The role of omalizumab in the treatment of severe allergic asthma.

BACKGROUND: A novel anti-immunoglobulin E (anti-IgE) therapy for asthma, omalizumab, has been approved for use in Canada. OBJECTIVE: To review the basic and clinical data for omalizumab, and to examine its possible role for asthma management in Canada. METHODS: A literature search from 1960 to 2006 was conducted in MEDLINE to identify studies of omalizumab. In addition, abstracts from recent respiratory and allergy scientific meetings were sought, and any unpublished data were requested from the manufacturer. A consensus panel of respiratory and allergy specialists reviewed and summarized the data, and derived a set of recommendations for omalizumab use. RESULTS: Omalizumab is a humanized monoclonal antibody designed to bind to the C epsilon 3 domain of the IgE molecule, forming soluble immune complexes that are cleared by the reticuloendothelial system. Subcutaneous injections, given at two- or four-week intervals at the recommended dose, result in a rapid decrease in free circulating IgE levels. In two phase III clinical trials of 1405 adult and adolescent patients with moderate to severe asthma maintained on moderate doses of inhaled corticosteroids (ICS), omalizumab reduced exacerbation rates compared with placebo, and was associated with improved symptoms and a greater corticosteroid-sparing effect. In a trial of 419 patients with severe disease that was uncontrolled despite the use of high-dose ICS and concurrent long-acting beta2-agonists, severe exacerbations were 50% less frequent in omalizumab-treated patients than in control subjects. Retrospective analyses have identified the characteristics of patients most likely to respond to omalizumab treatment. RECOMMENDATIONS: Omalizumab may be considered as a potential adjunctive therapy in atopic patients with severe asthma uncontrolled by conventional therapy with optimal doses of ICS and appropriate adjunctive therapy (eg, long-acting beta2-agonists). Typically, patients are identified by the need for frequent short course or continuous oral corticosteroids. Therapy should be initiated only after review by a specialist to confirm the diagnosis and that conventional therapy is optimal.

Anti-Asthmatic Agents↗