Effects of the non-native amphibian species Discoglossus pictus on the recipient amphibian community: niche overlap, competition and community organization

The painted frog, Discoglossus pictus, was introduced into the Iberian Peninsula 100 years ago and its distribution has steadily increased since then. We studied the effects of this non-native amphibian species on the native ones in the northeastern area of the peninsula. We compared amphibian assemblages in regions with and without D. pictus to estimate niche overlap between species. Additionally, we carried out a laboratory evaluation of the effects of competition between the non-native and the two native species with which it overlaps most commonly: Bufo calamita and Pelodytes punctatus. The presence of D. pictus larvae reduced the survival, body mass and activity of B. calamita, and increased time to metamorphosis. Furthermore, D. pictus showed the highest consumption rate while P. punctatus showed the lowest. One possible consequence of these competitive interactions is an alteration of species co-occurrence patterns in the recipient community on a regional scale. In the non-invaded area, the checkerboard score (C-score) of co-occurrence indicated that the community was structured, whereas the standardized C-score in the invaded area indicated that the community did not differ significantly from having a random structure. These results suggest that competition between native and non-native species can cause recipient communities to become less structured.     

Steady flow velocity measurements in a pulmonary artery model with varying degrees of pulmonic stenosis

Velocity and flow visualization studies were conducted in an adult size pulmonary artery model with varying degrees of valvular stenosis, using a two dimensional laser Doppler anemometer system. Velocity measurements in the main, left and right branches of the pulmonary artery revealed that as the degree of pulmonic stenosis increased, the jet type flow created by the valve hit the distal wall of the LPA farther downstream from the junction of the bifurcation. This in turn led to higher levels of turbulent and disturbed flow, and larger secondary flow motion in the LPA compared to the RPA. The high levels of turbulence measured in the main and left pulmonary arteries with the stenotic valves, could lead to the clinically observed phenomenon of post stenotic dilatation in the MPA extending into the LPA.     

Differential clinical efficacy of anti-CD4 monoclonal antibodies in rat adjuvant arthritis is paralleled by differential influence on NF-κB binding activity and TNF-α secretion of T cells

The aim of this study was to analyze the differential effects of three anti-CD4 monoclonal antibodies (mAbs) (with distinct epitope specifities) in the treatment of rat adjuvant arthritis (AA) and on T-cell function and signal transduction. Rat AA was preventively treated by intraperitoneal injection of the anti-CD4 mAbs W3/25, OX35, and RIB5/2 (on days -1, 0, 3, and 6, i.e. 1 day before AA induction, on the day of induction [day 0], and thereafter). The effects on T-cell reactivity in vivo (delayed-type hypersensitivity), ex vivo (ConA-induced proliferation), and in vitro (mixed lymphocyte culture) were assessed. The in vitro effects of anti-CD4 preincubation on T-cell receptor (TCR)/CD3-induced cytokine production and signal transduction were also analyzed. While preventive treatment with OX35 and W3/25 significantly ameliorated AA from the onset, treatment with RIB5/2 even accelerated the onset of AA by approximately 2 days (day 10), and ameliorated the arthritis only in the late phase (day 27). Differential clinical effects at the onset of AA were paralleled by a differential influence of the mAbs on T-cell functions, i.e. in comparison with OX35 and W3/25, the 'accelerating' mAb RIB5/2 failed to increase the delayed-type hypersentivity (DTH) to Mycobacterium tuberculosis, increased the in vitro tumor necrosis factor (TNF)-α secretion, and more strongly induced NF-κB binding activity after anti-CD4 preincubation and subsequent TCR/CD3-stimulation. Depending on their epitope specificity, different anti-CD4 mAbs differentially influence individual proinflammatory functions of T cells. This fine regulation may explain the differential efficacy in the treatment of AA and may contribute to the understanding of such treatments in other immunopathologies.     

Mitochondrial DNA and TLR9 drive muscle inflammation upon Opa1 deficiency

Opa1 participates in inner mitochondrial membrane fusion and cristae morphogenesis. Here, we show that muscle‐specific Opa1 ablation causes reduced muscle fiber size, dysfunctional mitochondria, enhanced Fgf21, and muscle inflammation characterized by NF‐κB activation, and enhanced expression of pro‐inflammatory genes. Chronic sodium salicylate treatment ameliorated muscle alterations and reduced the muscle expression of Fgf21. Muscle inflammation was an early event during the progression of the disease and occurred before macrophage infiltration, indicating that it is a primary response to Opa1 deficiency. Moreover, Opa1 repression in muscle cells also resulted in NF‐κB activation and inflammation in the absence of necrosis and/or apoptosis, thereby revealing that the activation is a cell‐autonomous process and independent of cell death. The effects of Opa1 deficiency on the expression NF‐κB target genes and inflammation were absent upon mitochondrial DNA depletion. Under Opa1 deficiency, blockage or repression of TLR9 prevented NF‐κB activation and inflammation. Taken together, our results reveal that Opa1 deficiency in muscle causes initial mitochondrial alterations that lead to TLR9 activation, and inflammation, which contributes to enhanced Fgf21 expression and to growth impairment.     

Quantitative trait loci for resistance to fish pasteurellosis in gilthead sea bream (Sparus aurata)

Fish pasteurellosis is a bacterial disease causing important losses in farmed fish, including gilthead sea bream, a teleost fish of great relevance in marine aquaculture. We report in this study a QTL analysis for resistance to fish pasteurellosis in this species. An experimental population of 500 offspring originating from eight sires and six dams in a single mass‐spawning event was subjected to a disease challenge with Photobacterium damselae subsp. piscicida (Phdp), the causative agent of fish pasteurellosis. A total of 151 microsatellite loci were genotyped in the experimental population, and half‐sib regression QTL analysis was carried out on two continuous traits, body length at time of death and survival, and for two binary traits, survival at day 7 and survival at day 15, when the highest peaks of mortality were observed. Two significant QTLs were detected for disease resistance. The first one was located on linkage group LG3 affecting late survival (survival at day 15). The second one, for overall survival, was located on LG21, which allowed us to highlight a potential marker (Id13) linked to disease resistance. A significant QTL was also found for body length at death on LG6 explaining 5–8% of the phenotypic variation.     

Life‐history traits of the stone loach Barbatula barbatula

The life‐history tactics of the stone loach Barbatula barbatula were studied in a Mediterranean‐type climate stream (Matarranya River) located in the Ebro River basin (north‐east Spain). Maximum observed ages were 2+ years in both sexes (1% of individuals), although only 0+ and 1+ year age groups were well represented. It is the lowest longevity reported for this species in its entire distribution. The seasonal growth period started in June and continued until November, but the pattern observed was different to northern populations. Barbatula barbatula in the Matarranya River was a multiple spawner, releasing small batches of oocytes between April and June. The fecundity of females was higher and the size of oocytes smaller in 1984 than in 1985. The relative fecundity (number of ripening and ripe oocytes g^?1 of fish) was lower than in northern European populations. The role of the particular environmental conditions of a Mediterranean stream was discussed in relation to the life‐history tactics of B. barbatula.