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Effective Barrier (effective + barrier)
Selected AbstractsUltrastructural features of the process of wound healing after tail and limb amputation in lizardACTA ZOOLOGICA, Issue 3 2010L. Alibardi Abstract Alibardi, L. 2010. Ultrastructural features of the process of wound healing after tail and limb amputation in lizard.,Acta Zoologica (Stockholm) 91: 306,318 Wound healing and re-epitelization after amputation of tail and limb in lizard have been studied by electron microscopy to understand the cytological base of immunity to infection in this species. After 2 days post-amputation in both limb and tail stumps, numerous granulocytes are accumulated over the stump, and participate to the formation of the scab. Bacteria remain confined to the scab or are engulfed by leukocytes and migrating keratinocytes located underneath the scab. Bacteria are degraded within lysosomes present in these cells and are not observed among mesenchymal cells or in blood vessels of the regenerative blastema. Granulocytes, migrating keratinocytes, and later macrophages form an effective barrier responsible for limiting microbe penetration. The innate immunity in lizard is very effective in natural (dirty) condition and impedes the spreading of infection to inner tissues. While the complete re-epitelization of the tail stump underneath the scab requires 4,7 days, the same process in the limb requires 8,18 or more days post-amputation, depending from the level of amputation and the persistence of a protruding humerus or femurs on the stump surface. This delay produces the permanence of inflammatory cells such as granulocytes and macrophages in the limb stump for a much longer period than in the tail stump, a process that stimulates scarring. [source] Seasonal and inter-annual variability of the moisture sources for Alpine precipitation during 1995,2002INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2010Harald Sodemann Abstract This study presents a first quantitative climatology of the moisture sources for precipitation in the European Alps, covering a 7-year period from January 1995 to August 2002. Using a Lagrangian moisture source diagnostic and data from the ERA-40: European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis, the contribution of the following moisture sources to annual mean precipitation has been diagnosed: North Atlantic ocean 39.6%, Mediterranean 23.3%, North Sea and Baltic Sea 16.6%, and European land surface 20.8%. However, strong seasonal variability of the influence of various moisture sources is evident. Most notably, moisture transport to the Alps changes from an oceanic mode characterised by dominantly North Atlantic moisture sources during winter to a continental mode during summer with a marked contribution from Central European land areas. The method identifies inter-annual variability with respect to the location of the moisture sources in the North Atlantic, and the importance of precipitation recycling during summer. Despite the smoothed Alpine orography in the ERA-40 model, the Alps act as an effective barrier for meridional moisture transport, leading to distinct mean moisture source locations at their northern and southern slopes. The Northern Alps are predominantly influenced by the North Atlantic ocean and Central European land sources with a clear seasonality and limited monthly variability. In contrast, the Southern Alps receive a large fraction of precipitation from the Mediterranean with considerable month-to-month variability. Possible implications of these differences for precipitation extremes and stable isotopes in precipitation are discussed. Copyright © 2009 Royal Meteorological Society [source] Biogeography of the Amazon molly, Poecilia formosaJOURNAL OF BIOGEOGRAPHY, Issue 1 2002Ingo Schlupp Aim The unisexual Amazon molly (Poecilia formosa) is a clonal, all-female fish but depends on sperm of heterospecific males to trigger embryogenesis. Thus, one very important factor shaping its geographical range is the presence of suitable host males. Several species of the genus Poecilia from Central America, Mexico and the USA can provide sperm in the laboratory, but are not utilized as hosts in nature. Consequently the potential geographic range of the Amazon molly is much larger than the actual range. This raises the question of what is responsible for the biogeographical range of the Amazon molly? Location Southern USA, Mexico and Central America. Methods We review the current data available for the distribution of the Amazon molly. We further tested whether salinity might hinder the dispersal of the species. Results Amazon mollies tolerate marine conditions. We review the available data on recent and human influenced introductions of Amazon mollies. Main conclusions We argue that male preferences are not responsible for the current range. We propose that prevailing near-shore marine currents act as an effective barrier against further dispersal. Furthermore, we discuss recent changes in the biogeography of the Amazon molly. [source] Limits to gene flow in marine animals with planktonic larvae: models of Littorina species around Point Conception, CaliforniaBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2004PAUL A. HOHENLOHE Simulation models examined the process of gene flow in marine animals with planktonic larvae, and three factors that may influence it: ocean currents, planktonic period and spawning season. To focus on a realistic example, the models were based on measured ocean currents around Point Conception in southern California and the life histories of two intertidal gastropods, Littorina scutulata and L. plena. Results suggested that: (1) convergent ocean currents can create an effective barrier to gene flow that can be relaxed by temporal variation; (2) longer scales of temporal variation have a greater effect than shorter scales; (3) planktonic period has little effect above a minimum duration; and (4) an extended spawning season can eliminate gene flow barriers when currents vary seasonally. Failure of past studies to detect a phylogeographical boundary at Point Conception may be explained by extended spawning seasons and temporal variation at seasonal to millennial scales. These results fit a conceptual model of marine speciation in which short-lived, leaky barriers restrict gene flow, and divergence in a few genes may quickly produce reproductive isolation, resulting in cryptic sibling species. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 169,187. [source] The transplacental transfer of the macrolide antibiotics erythromycin, roxithromycin and azithromycinBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2000Gynaecology), Tuija Heikkinen Consultant (Obstetrics Objective To investigate the transplacental transfer of the macrolide antibiotics erythromycin, roxithromycin and azithromycin. Methods Twenty-one term placentas were obtained with maternal consent immediately after delivery and a two-hour nonrecirculating perfusion of a single placental cotyledon was performed. Erythromycin (2 ,g/mL), roxithromycin (2 ,g/mL) and azithromycin (0.3 ,g/mL) were infused to the maternal inflow at a constant rate, with antipyrine as a reference compound, and their appearance in the fetal circulation was followed. Drug concentrations were measured by high performance liquid chromatography for 120 min. Results The mean transplacental transfers (TPTss) for erythromycin, roxithromycin and azithromycin were 3.0%, 4.3% and 2.6%, respectively, calculated as the ratio between the steady state concentrations in fetal venous and maternal arterial sides. Similar results were obtained when the TPT was calculated as the absolute amount of drug transferred across the placenta during 2-hour perfusion (TPTA). No significant differences were found among the three macrolides in TPTSS (P= 0.39) or TPTA (P= 0.35). The TPTSS of erythromycin, roxithromycin and azithromycin were 41%, 35% and 32% of the freely diffusable reference compound antipyrine, respectively. Steady state was reached in 60 minutes in each perfusion indicating sufficient perfusion time. Conclusion The limited transplacental transfer of erythromycin, roxithromycin and azithromycin suggests compromised efficacy in the treatment of fetal infections. On the other hand, the placenta seems to produce an effective barrier reducing the fetal exposure when these three macrolides are used to treat maternal infections. [source] | ||||||||||