Local-scale species-energy relationships in fish assemblages of some forested streams of the Bolivian Amazon

Productivity (trophic energy) is one of the most important factors promoting variation in species richness. A variety of species-energy relationships have been reported, including monotonically positive, monotonically negative, or unimodal (i.e. hump-shaped). The exact form of the relationship seems to depend, among other things, on the spatial scale involved. However, the mechanisms behind these patterns are still largely unresolved, although many hypotheses have been suggested. Here we report a case of local-scale positive species-energy relationship. Using 14 local fish assemblages in tropical forested headwater streams (Bolivia), and after controlling for major local abiotic factors usually acting on assemblage richness and structure, we show that rising energy availability through leaf litter decomposition rates allows trophically specialized species to maintain viable populations and thereby to increase assemblage species richness. By deriving predictions from three popular mechanistic explanations, i.e. the 'increased population size', the 'consumer pressure', and the 'specialization' hypotheses, our data provide only equivocal support for the latter.     

Anticipative management for coral reef ecosystem services in the 21st century

Under projections of global climate change and other stressors, significant changes in the ecology, structure and function of coral reefs are predicted. Current management strategies tend to look to the past to set goals, focusing on halting declines and restoring baseline conditions. Here, we explore a complementary approach to decision making that is based on the anticipation of future changes in ecosystem state, function and services. Reviewing the existing literature and utilizing a scenario planning approach, we explore how the structure of coral reef communities might change in the future in response to global climate change and overfishing. We incorporate uncertainties in our predictions by considering heterogeneity in reef types in relation to structural complexity and primary productivity. We examine 14 ecosystem services provided by reefs, and rate their sensitivity to a range of future scenarios and management options. Our predictions suggest that the efficacy of management is highly dependent on biophysical characteristics and reef state. Reserves are currently widely used and are predicted to remain effective for reefs with high structural complexity. However, when complexity is lost, maximizing service provision requires a broader portfolio of management approaches, including the provision of artificial complexity, coral restoration, fish aggregation devices and herbivore management. Increased use of such management tools will require capacity building and technique refinement and we therefore conclude that diversification of our management toolbox should be considered urgently to prepare for the challenges of managing reefs into the 21st century.     

Manipulation of the Anoxic Metabolism in Escherichia coli by ArcB Deletion Variants in the ArcBA Two-Component System

Bioprocesses conducted under conditions with restricted O₂ supply are increasingly exploited for the synthesis of reduced biochemicals using different biocatalysts. The model facultative anaerobe Escherichia coli has elaborate sensing and signal transduction mechanisms for redox control in response to the availability of O₂ and other electron acceptors. The ArcBA two-component system consists of ArcB, a membrane-associated sensor kinase, and ArcA, the cognate response regulator. The tripartite hybrid kinase ArcB possesses a transmembrane, a PAS, a primary transmitter (H1), a receiver (D1), and a phosphotransfer (H2) domain. Metabolic fluxes were compared under anoxic conditions in a wild-type E. coli strain, its ΔarcB derivative, and two partial arcB deletion mutants in which ArcB lacked either the H1 domain or the PAS-H1-D1 domains. These analyses revealed that elimination of different segments in ArcB determines a distinctive distribution of d-glucose catabolic fluxes, different from that observed in the ΔarcB background. Metabolite profiles, enzyme activity levels, and gene expression patterns were also investigated in these strains. Relevant alterations were observed at the P-enol-pyruvate/pyruvate and acetyl coenzyme A metabolic nodes, and the formation of reduced fermentation metabolites, such as succinate, d-lactate, and ethanol, was favored in the mutant strains to different extents compared to the wild-type strain. These phenotypic traits were associated with altered levels of the enzymatic activities operating at these nodes, as well as with elevated NADH/NAD⁺ ratios. Thus, targeted modification of global regulators to obtain different metabolic flux distributions under anoxic conditions is emerging as an attractive tool for metabolic engineering purposes.     

Effects of low-calcium reperfusion and adenosine on diastolic behavior during the transitory systolic overshoot of the stunned myocardium in the rabbit

The aims of the present study were to determine whether the transitory systolic overshoot (TSO) that occurs in the early reperfusion (R) of the stunned myocardium is accompanied by diastolic alterations, and to determine whether the R with low Ca2+ Krebs-Henseleit's solution or with adenosine modifies these alterations. Isolated-isovolumic rabbit hearts were divided in 3 groups (G). G1 (n = 11) was perfused with Krebs-Henseleit's solution, subjected to 15 min of global ischemia and 30 min R; G2 (n = 10) was reperfused during the first 10 min with Krebs-Henseleit's solution [Ca2+] = 1 mmol/L, which was increased in the perfusate to 1.5 mmol/L up to 20 min R and at 2.5 mmol/L from 20 to 30 min R. G3 (n = 12) was perfused with Krebs-Henseleit's solution with adenosine (0.03 microg x kg(-1) x min(-1)) from 10 min before ischemia and during all R. Left ventricular (LV) +dP/dtmax (mmHg/s), LV end diastolic pressure (LVEDP, mmHg), and 1 relaxation index (t(1/2)) were measured in preischemic state, at 30, 50, 60, 70, 90, and 120 s R, and then at 5 and 30 min R. The +dP/dtmax recovered to 621 +/- 77 mmHg/s (p > 0.05), 346 +/- 31 mmHg/s (p < 0.05 vs. G1), and 533 +/- 76 mmHg/s (p > 0.05) from preischemic value of 730 +/- 39, 690 +/- 32, and 758 +/- 57 in G1, G2, and G3, respectively. The LVEDP in G1 and G3 increased early in the R, and it was negatively correlated with the +dP/dtmax (r = -0.63, p = 0.0369; and r = -0.71, p = 0.0090, respectively). The R with low Ca2+ abolished this correlation and attenuated the TSO phase. The correlation between LVEDP and +dP/dtmax in G1 and G3 and the lack of correlation in G2 suggests there are common mechanisms for the systolic and diastolic alterations during the TSO phase that are possibly related to Ca2+ overload but not with the vascular tone.     

Recent Emergence of Clonal Group O25b:K1:H4-B2-ST131 ibeA Strains among Escherichia coli Poultry Isolates,Including CTX-M-9-Producing Strains,and Comparison with Clinical Human Isolates

To discern the possible spread of the Escherichia coli O25b:H4-ST131 clonal group in poultry and the zoonotic potential of avian strains, we made a retrospective search of our strain collection and compared the findings for those strains with the findings for current strains. Thus, we have characterized a collection of 19 avian O25b:H4-ST131 E. coli strains isolated from 1995 to 2010 which, interestingly, harbored the ibeA gene. Using this virulence gene as a criterion for selection, we compared those 19 avian strains with 33 human O25b:H4-ST131 ibeA-positive E. coli strains obtained from patients with extraintestinal infections (1993 to 2009). All 52 O25b:H4-ST131 ibeA-positive E. coli strains shared the fimH, kpsMII, malX, and usp genes but showed statistically significant differences in nine virulence factors, namely, papGIII, cdtB, sat, and kpsMII K5, which were associated with human strains, and iroN, kpsMII K1, cvaC, iss, and tsh, which were associated with strains of avian origin. The XbaI macrorestriction profiles of the 52 E. coli O25b:H4-ST131 ibeA-positive strains revealed 11 clusters (clusters I to XI) of >85% similarity, with four clusters including strains of human and avian origin. Cluster VII (90.9% similarity) grouped 10 strains (7 avian and 3 human strains) that mostly produced CTX-M-9 and that also shared the same virulence profile. Finally, we compared the macrorestriction profiles of the 12 CTX-M-9-producing O25b:H4-ST131 ibeA strains (7 avian and 5 human strains) identified among the 52 strains with those of 15 human O25b:H4-ST131 CTX-M-14-, CTX-M-15-, and CTX-M-32-producing strains that proved to be negative for ibeA and showed that they clearly differed in the level of similarity from the CTX-M-9-producing strains. In conclusion, E. coli clonal group O25b:H4-ST131 ibeA has recently emerged among avian isolates with the new acquisition of the K1 capsule antigen and includes CTX-M-9-producing strains. This clonal group represents a real zoonotic risk that has crossed the barrier between human and avian hosts.Strains of the extensively antimicrobial-resistant Escherichia coli clonal group of sequence type (ST) 131 (ST131) belonging to serotype O25b:H4 have recently been recognized to be important human pathogens worldwide (9, 33). Although it is commonly associated with the dissemination of CTX-M-15 extended-spectrum cephalosporin resistance, E. coli O25b:H4-ST131 also occurs as a fluoroquinolone (FQ)-resistant but cephalosporin-susceptible pathogen (5, 22, 26, 27). Currently, it is assumed that O25b:H4-ST131 strains circulate not only among humans but also among animal hosts (13, 21, 37), which would contribute to the ongoing global emergence of O25b:H4-ST131, in the case of regular transmission between animals and humans. Even though CTX-M-15 is the most widely distributed extended-spectrum beta-lactamase (ESBL) linked to this clonal group, other, different variants of CTX-M have recently been reported, such as CTX-M-9, CTX-M-14, and CTX-M-32 (4, 34, 36, 39). Noteworthy was the detection, for the first time on poultry farms, of this clonal group producing CTX-M-9 that had macrorestriction profiles and virulence genes very similar to those observed in clinical human isolates (10).Extraintestinal pathogenic E. coli (ExPEC) strains, which include avian pathogenic E. coli (APEC) and human uropathogenic E. coli (UPEC), septicemic E. coli, and newborn meningitis-causing E. coli (NMEC) strains, exhibit considerable genome diversity and have a wide range of virulence-associated factors (12, 18). While infections caused by APEC strains initially start as a respiratory tract disease which evolves to a systemic infection of the internal organs and, finally, to sepsis, the most frequent origin of human sepsis is urinary tract infection (UTI), especially pyelonephritis (2, 3, 11). However, APEC strains have been recognized to share common traits with human isolates (29, 30, 31), including the K1 capsule antigen (23, 24, 29) and the ibeA gene (14). In addition, retail chicken products have been found to carry nalidixic-resistant ExPEC strains (17, 19), and although it is drug susceptible, an E. coli strain belonging to the O25b:H4-ST131 clonal group has even recently been detected in retail chicken (41), supporting the urgent necessity for the implementation of food control measures.The aim of the present study was to discern the possible spread of the O25b:H4-ST131 clonal group, especially CTX-M-9-producing strains, in poultry and the zoonotic potential of avian isolates. For this purpose, we made a retrospective search of our human and avian strain collections and compared the findings for those strains with the findings for current strains. Identification of this emerging clone among avian sources and comparison of the clone with clinical human isolates will shed new light on the epidemiology of the O25b:H4-ST131 clonal group.     

Antioxidant-Like Effects and Protective Action of Transcranial Magnetic Stimulation in Depression Caused by Olfactory Bulbectomy

We studied the effects of transcranial magnetic stimulation (TMS, 60 Hz and 0.7 mT for 4 h/day for 14 days) on oxidative and cell damage caused by olfactory bulbectomy (OBX) in Wistar rats. The levels of lipid peroxidation products and caspase-3 were enhanced by OBX, whereas it prompted a reduction in reduced glutathione (GSH) content and antioxidative enzymes activities. The treatment with TMS reverted towards normality the biomarkers indicative of oxidative stress and apoptosis. In conclusion, our data show that TMS induced a protection against cell and oxidative damage induced by OBX, as well as they support the hypothesis that oxidative stress may play an important role in depression.     

A combined RT‐PCR and dot‐blot hybridization method reveals the coexistence of SJNNV and RGNNV betanodavirus genotypes in wild meagre (Argyrosomus regius)

Aims: To detect the possible coexistence of striped jack nervous necrosis virus (SJNNV) and red‐spotted grouper nervous necrosis virus (RGNNV) genotypes in a single fish, a methodology based on the combination of PCR amplification and blot hybridization has been developed and applied in this study. Methods and Results: The degenerate primers designed for the PCR procedure target the T4 region within the capsid gene, resulting in the amplification of both genotypes. The subsequent hybridization of these amplification products with two different specific digoxigenin‐labelled probes resulted in the identification of both genotypes separately. The application of the RT‐PCR protocol to analyse blood samples from asymptomatic wild meagre (Argyrosomus regius) specimens has shown a 46·87% of viral nervous necrosis virus carriers. The combination of RT‐PCR and blot hybridization increases the detection rate up to 90·62%, and, in addition, it has shown the coexistence of both genotypes in 18 out of the 32 specimens analysed (56·25%). Conclusions: This study reports the coexistence of betanodaviruses belonging to two different genotypes (SJNNV and RGNNV) in wild fish specimens. Significance and Impact of the Study: This is the first report demonstrating the presence of SJNNV and RGNNV genotypes in the same specimen. This study also demonstrates a carrier state in this fish species for the first time.     

Males and females gonad fatty acids of the sea urchins Paracentrotus lividus and Arbacia lixula (Echinodermata)

The aim of this study was to analyze male and female gonad fatty acids of two sea urchin species, Paracentrotus lividus and Arbacia lixula, from the south coast of Spain. Additionally, we investigated possible differences between two locations. The ovaries of both species showed higher percentages of 14:0, 16:0, 16:1n-7, 18:2n-6, 18:3n-3 and 18:4n-3 than testes and lower levels of 18:0, 22:1n-9, 20:4n-6 and 22:5n-3. In P. lividus but not in A. lixula, the level of 20:5n-3 was higher in testes than in ovaries. These differences between sexes probably indicate different requirements of males and females during gametogenesis although the presence of a large number of gametes in the mature gonad may also have influences on fatty acid composition. Significant differences in gonad fatty acid profiles where also found when individuals of P. lividus collected at a location of the Mediterranean region were compared with specimens collected at the Atlantic coast. The most remarkable changes were the lower levels of 14:0, 18:1n-7, 20:1n-9, 20:4n-6 and 22:4n-6 and the higher values of 20:1n-11, 20:5n-3 and 22:6n-3 found in males and females of the Mediterranean specimens compared to those of the Atlantic coast. These differences probably reflect the differences in potential food sources at each location.