The effects of interleukin-8 on airway smooth muscle contraction in cystic fibrosis

<p>Abstract</p> <p>Background</p> <p>Many cystic fibrosis (CF) patients display airway hyperresponsiveness and have symptoms of asthma such as cough, wheezing and reversible airway obstruction. Chronic airway bacterial colonization, associated with neutrophilic inflammation and high levels of interleukin-8 (IL-8) is also a common occurrence in these patients. The aim of this work was to determine the responsiveness of airway smooth muscle to IL-8 in CF patients compared to non-CF individuals.</p> <p>Methods</p> <p>Experiments were conducted on cultured ASM cells harvested from subjects with and without CF (control subjects). Cells from the 2^ndto 5^thpassage were studied. Expression of the IL-8 receptors CXCR1 and CXCR2 was assessed by flow cytometry. The cell response to IL-8 was determined by measuring intracellular calcium concentration ([Ca²⁺]_i), cell contraction, migration and proliferation.</p> <p>Results</p> <p>The IL-8 receptors CXCR1 and CXCR2 were expressed in both non-CF and CF ASM cells to a comparable extent. IL-8 (100 nM) induced a peak Ca²⁺release that was higher in control than in CF cells: 228 ± 7 versus 198 ± 10 nM (p < 0.05). IL-8 induced contraction was greater in CF cells compared to control. Furthermore, IL-8 exposure resulted in greater phosphorylation of myosin light chain (MLC₂₀) in CF than in control cells. In addition, MLC₂₀expression was also increased in CF cells. Exposure to IL-8 induced migration and proliferation of both groups of ASM cells but was not different between CF and non-CF cells.</p> <p>Conclusion</p> <p>ASM cells of CF patients are more contractile to IL-8 than non-CF ASM cells. This enhanced contractility may be due to an increase in the amount of contractile protein MLC₂₀. Higher expression of MLC₂₀by CF cells could contribute to airway hyperresponsiveness to IL-8 in CF patients.</p

Eggshell morphology and gekkotan life-history evolution

Eggshell structure is related to fundamental aspects of embryonic development (via water and gas exchange), adult ecology and behavior (via nest site selection), and demography (via effects on survival). We compared life-history characteristics between gekkotans that lay rigid- versus parchment- shelled eggs to determine if evolutionary shifts in eggshell structure are associated with life-history evolution. Ancestral gekkotans laid parchment-shelled eggs, with rigid-shelled eggs evolving later. Clutch size in oviparous gekkotans is fixed at one or two eggs, and this characteristic eliminates an egg size versus clutch size tradeoff as a life-history strategy. We found that species laying rigid-shelled eggs exhibit (1) smaller eggs relative to adult body size, (2) smaller hatchlings relative to the size of the egg, (3) earlier embryonic stage at oviposition, (4) longer incubation periods, and (5) smaller adult body sizes than species laying parchment-shelled eggs. These patterns hold when accounting for phylogenetic relatedness, and are not explained by geographic distributions of climate and habitat. In general, our data support the hypothesis that the spherical shapes of rigid-shelled eggs limit their size (volume), which in turn has restricted hatchling size and adult body size. In contrast, while parchment-shelled eggs are similarly constrained in width, elongate shapes allow egg sizes, and hence hatchling sizes, to increase relative to adult body sizes. Finally, the evolution of rigid-shelled eggs may have allowed gekkotans to become so successful; over 1,000 species lay rigid-shelled eggs, as compared to about 200 species that lay eggs exhibiting the ancestral parchment-shelled condition

Evolutionary success of prokaryotes

How can the evolutionary success of prokaryotes be explained ? How did they manage to survive conditions that have fluctuated, with drastic events over 3.5 billion years ? Which significant metabolisms and mechanisms have appeared over the course of evolution that have permitted them to survive the most inhospitable conditions from the physicochemical point of view ? In a 'Red Queen Race', prokaryotes have always run sufficiently fast to adapt to constraints imposed by the environment and the other living species with which they have established interactions. If the criterion retained to define the level of evolution of an organism is its capacity to survive and to yield the largest number of offsprings, prokaryotes must be considered highly evolved organisms