Home About us Contact
|
Home About us Contact | ||
|
|
||
Important Stimulus (important + stimulus)
Selected AbstractsBehavior and physiology of mechanoreception: separating signal and noiseINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 1 2009John C. MONTGOMERY Abstract The mechanosensory lateral line is found in all aquatic fish and amphibians. It provides a highly sensitive and versatile hydrodynamic sense that is used in a wide range of behavior. Hydrodynamic stimuli of biological interest originate from both abiotic and biotic sources, and include water currents, turbulence and the water disturbances caused by other animals, such as prey, predators and conspecifics. However, the detection of biologically important stimuli often has to occur against a background of noise generated by water movement, or movement of the fish itself. As such, separating signal and noise is "of the essence" in understanding the behavior and physiology of mechanoreception. Here we discuss general issues of signal and noise in the lateral-line system and the behavioral and physiological strategies that are used by fish to enhance signal detection in a noisy environment. In order for signal and noise to be separated, they need to differ, and we will consider those differences under the headings of: frequency and temporal pattern; intensity discrimination; spatial separation; and mechanisms for the reduction of self-generated noise. We systematically cover the issues of signal and noise in lateral-line systems, but emphasize recent work on self-generated noise, and signal and noise issues related to prey search strategies and collision avoidance. [source] Do cities export biodiversity?DIVERSITY AND DISTRIBUTIONS, Issue 1 2008Traffic as dispersal vector across urban, rural gradients ABSTRACT Urban areas are among the land use types with the highes richness in plant species. A main feature of urban floras is the high proportion of non-native species with often divergent distribution patterns along urban,rural gradients. Urban impacts on plant species richness are usually associated with increasing human activity along rural-to-urban gradients. As an important stimulus of urban plant diversity, human-mediated seed dispersal may drive the process of increasing the similarity between urban and rural floras by moving species across urban,rural gradients. We used long motorway tunnels as sampling sites for propagules that are released by vehicles to test for the impact of traffic on seed dispersal along an urban,rural gradient. Opposite lanes of the tunnels are separated by solid walls, allowing us to differentiate seed deposition associated with traffic into vs. out of the city. Both the magnitude of seed deposition and the species richness in seed samples from two motorway tunnels were higher in lanes leading out of the city, indicating an ,export' of urban biodiversity by traffic. As proportions of seeds of non-native species were also higher in the outbound lanes, traffic may foster invasion processes starting from cities to the surrounding landscapes. Indicator species analysis revealed that only a few species were confined to samples from lanes leading into the city, while mostly species of urban habitats were significantly associated with samples from the outbound lanes. The findings demonstrate that dispersal by traffic reflects different seed sources that are associated with different traffic directions, and traffic may thus exchange propagules along the urban,rural gradient. [source] Insights into Serotonin Signaling Mechanisms Associated with Canine Degenerative Mitral Valve DiseaseJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2010M.A. Oyama Little is known about the molecular abnormalities associated with canine degenerative mitral valve disease (DMVD). The pathology of DMVD involves the differentiation and activation of the normally quiescent mitral valvular interstitial cell (VIC) into a more active myofibroblast phenotype, which mediates many of the histological and molecular changes in affected the valve tissue. In both humans and experimental animal models, increased serotonin (5-hydroxytryptamine, 5HT) signaling can induce VIC differentiation and myxomatous valve damage. In canine DMVD, numerous lines of evidence suggest that 5HT and related molecules such as transforming growth factor-, play a critical role in the pathogenesis of this disease. A variety of investigative techniques, including gene expression, immunohistochemistry, protein blotting, and cell culture, shed light on the potential role of 5HT in the differentiation of VIC, elaboration of myxomatous extracellular matrix components, and activation of mitogen-activated protein kinase pathways. These studies help support a hypothesis that 5HT and its related pathways serve as an important stimulus in canine DMVD. This review describes the pathological characteristics of canine DMVD, the organization and role of the 5HT pathway in valve tissue, involvement of 5HT in human and experimental models of valve disease, avenues of evidence that suggest a role for 5HT in naturally occurring DMVD, and finally, a overarching hypothesis describing a potential role for 5HT in canine DMVD. [source] Effects of Cyclic Hydrostatic Pressure on the Metabolism of Human Osteoarthritic Chondrocytes Cultivated in a Collagen GelARTIFICIAL ORGANS, Issue 2 2007Karsten Gavénis Abstract:, Among other parameters, the application of mechanical force may provide an important stimulus in modulating the structure and function of tissue-engineered articular cartilage. We developed a cultivation chamber in which six collagen type-I gel samples, seeded with human osteoarthritic chondrocytes, can be cultivated simultaneously. A cyclic hydrostatic pressure of up to 40 kPa with a frequency of 0.0125 Hz was applied, and cultivation was performed for 1, 4, 7, or 14 days. Histological examinations revealed a spheroidal cell morphology in the treatment group. In contrast, control samples of the same patients represented a more fibroblastic appearance. Collagen type-II (col-II) protein was found in the very pericellular region of all investigated samples; the col-II content did not obviously vary between the control and treatment groups. In the treatment group, col-II and aggrecan gene expression were elevated. A spectrophotometric quantification of proteoglycan concentrations in media supernatants revealed a statistically significant enhancement in the treatment group. [source] The topical glucocorticoids beclomethasone dipropionate and fluticasone propionate inhibit human T-cell allergen-induced production of IL-5, IL-3 and GM-CSF mRNA and proteinCLINICAL & EXPERIMENTAL ALLERGY, Issue 1 2001N. Powell T-cell production of eosinophil-active cytokines (IL-5, IL-3, GM-CSF) is thought to be fundamental to asthma pathogenesis. Inhaled aeroallergens may be one important stimulus for T-cell cytokine production in asthma. To compare the potency and efficacy of the topical anti-asthma glucocorticoids beclomethasone dipropionate (BDP) and fluticasone propionate (FP) in inhibiting allergen-driven peripheral blood T-cell proliferation and production of IL-3, IL-5 and GM-CSF mRNA and protein. Peripheral blood mononuclear cells from six atopic asthmatics sensitized to house dust mite (HDM) were cultured in the presence of HDM and serial dilutions of BDP or FP in vitro. Cellular proliferation (7 days) and culture supernatant cytokine concentrations (6 days) were measured by uptake of tritiated thymidine and ELISA, respectively. Cytokine mRNA expression (24 h) was measured in three subjects using a quantitative PCR technique. Both BDP and FP inhibited allergen-induced T-cell proliferation, expression of IL-3, IL-5 and GM-CSF mRNA, and secretion of the corresponding proteins in a concentration-dependent fashion. FP was considerably more potent, but not more efficacious, in exerting these actions. Both BDP and FP have the potential markedly to inhibit allergen-induced T-cell production of asthma-relevant cytokines. This activity is effected at the level of T-cell proliferation and cytokine gene transcription. These properties may be key features of the anti-asthma activity of these drugs. The greater potency of FP in vitro may be responsible for its greater clinical potency. [source] | |||||||||||||