Relationships between fish feeding guild and trophic structure in English lowland shallow lakes subject to anthropogenic influence: implications for lake restoration

The shallow lakes of Eastern England have been subject to intense anthropogenic pressures including nutrient enrichment and fish stocking. We sought to determine the relationships between fish community structure and other ecosystem characteristics in 28 of these lakes through classification of fish species into piscivorous, zooplanktivorous and benthivorous feeding guilds according to the literature. Canonical correspondence analysis produced clear associations between fish and ecosystem characteristics that generally agreed with other theoretical (e.g. the alternative stable states hypothesis) and empirical studies, but with some important differences. There was a striking lack of relationships between nutrients and other variables, indicating the importance of top-down rather than bottom-up processes as a structuring force in the generally eutrophic study lakes. The presence of submerged (and shoreline) vegetation was associated with a diverse assemblage of apparently co-existing piscivorous (principally pike Esox lucius) and zooplanktivorous species. Perch Perca fluviatilis, a significant predator in other studies, was unimportant and argued to be limited by water quality in the extremely shallow lakes. In contrast, the benthivorous fish guild (principally carp Cyprinus carpio, bream Abramis brama and tench Tinca tinca) essentially represented the inverse of the potential pelagic associations between piscivores/zooplanktivores and vegetation. The introduction of large benthivores to many study lakes could have precipitated a loss of submerged vegetation through direct uprooting during foraging, with the effect of simplifying the fish community being most acute where littoral vegetation was limited by other anthropogenic factors. It is implied that attempts to promote or restore submerged vegetation in these lakes would best target benthivorous species.     

Translation of Sindbis virus 26S mRNA does not require intact eukariotic initiation factor 4G

The infection of baby hamster kidney (BHK) cells by Sindbis virus gives rise to a drastic inhibition of cellular translation, while under these conditions the synthesis of viral structural proteins directed by the subgenomic 26S mRNA takes place efficiently. Here, the requirement for intact initiation factor eIF4G for the translation of this subgenomic mRNA has been examined. To this end, SV replicons that contain the protease of human immunodeficiency virus type 1 (HIV-1) or the poliovirus 2A(pro) replacing the sequences of SV glycoproteins have been constructed. BHK cells electroporated with the different RNAs synthesize protein C and the corresponding protease at late times. Notably, the proteolysis of eIF4G by both proteases has little effect on the translation of the 26S mRNA. In addition, recombinant viable SVs were engineered that encode HIV-1 PR or poliovirus 2A protease under the control of a duplicated late promoter. Viral protein synthesis at late times of infection by the recombinant viruses is slightly affected in BHK cells that contain proteolysed eIF4G. The translatability of SV genomic 49S mRNA was assayed in BHK cells infected with a recombinant virus that synthesizes luciferase and transfected with a replicon that expresses poliovirus 2Apro. Under conditions where eIF4G has been hydrolysed significantly the translation of genomic SV RNA was deeply inhibited. These findings indicate a different requirement for intact eIF4G in the translation of genomic and subgenomic SV mRNAs. Finally, the translation of the reporter gene that encodes green fluorescent protein, placed under the control of a second duplicate late promoter, is also resistant to the cleavage of eIF4G. In conclusion, despite the presence of a cap structure in the 5' end of the subgenomic SV mRNA, intact eIF4G is not necessary for its translation.     

Two related,low-temperature-induced genes from Brassica napus are homologous to the human tumour bbc1 (breast basic conserved) gene

In order to identify genes involved in cold acclimation, we have constructed a cDNA library from Brassica napus (cv. Samouraï) cold-acclimated etiolated seedlings. By differential screening, a cDNA clone named pBnC24 (Brassica napus Cold), corresponding to a new cold-inducible plant gene, was isolated. Northern blot hybridizations using total RNA from acclimated and unacclimated seedlings confirmed that BnC24 represents a cold-regulated gene. In contrast with a number of cold-inducible plant genes, BnC24 does not seem to be responsive to abscisic acid (ABA). In addition, further screening of the cold-acclimated cDNA library using pBnC24 cDNA as a probe, allowed the isolation of a second type of homologous cDNA. Sequence analysis showed that the two BnC24 genes encode basic 24 kDa proteins, which are highly hydrophilic and rich in alanine, lysine and arginine. The nucleotide and deduced amino acid sequences of these clones do not show any homology with other previously described cold-induced plants genes. However they have strong homology with a recently discovered human tumour gene, bbc1 (breast basic conserved), which seems to be highly conserved in eukaryotes.     

Lack of Exercise of "Moderate to Vigorous" Intensity in People with Low Levels of Physical Activity Is a Major Discriminant for Sociodemographic Factors and Morbidity

Introduction

The aim is to examine the differences between participation at low and zero moderate to vigorous physical activity (MVPA) in relation to their trends and associations with known socio-demographic and health factors. We hypothesised that the number of people at zero MVPA level could be rising despite a parallel increase in the population meeting the recommended MVPA level. We also hypothesised that graded associations of sociodemographic and health factors exist across MVPA levels.

Methods

Two independent population-based samples (n = 4320 [2004] and n = 2176 [1997]), were recruited with a stratified and random sampling procedure and interviewed at home by professional interviewers. The MVPA was assessed by validated questionnaire. The participants were classified into three MVPA levels: zero, low and recommended MVPA. The trend of each MVPA level was analysed with the standardized prevalence ratios. Correlates of low and zero MVPA levels were examined using multinomial logistic regression.

Results

The population at zero and recommended MVPA levels rose between 1997–2004 by 12% (95% CI, 5–20%) and 7% (95% CI,−4–19%) respectively, while the population at low MVPA level decreased. At zero MVPA level, associative patterns were observed with sociodemographic and health factors which were different when compared to the population at low MVPA level.

Conclusions

Despite the slight increase of population meeting the recommended MVPA level, a higher trend of increase was observed at zero MVPA level. Both recommended and low MPVA levels increased their participation by absorbing participants from the low MVPA level. The sociodemographic profile of those with low MVPA was more similar to the population at recommended MVPA than at zero MVPA level. Methodological implications about the combination of light and moderate-intensity PA could be derived. The prevention of decline in actual low MVPA could change the trend of increase in the population at zero MVPA level, particularly among young adults.     

Effects of Heat Shock on Resistance to Parasitoids and on Life History Traits in an Aphid/Endosymbiont System

Temperature variation is an important factor determining the outcomes of interspecific interactions, including those involving hosts and parasites. This can apply to variation in average temperature or to relatively short but intense bouts of extreme temperature. We investigated the effect of heat shock on the ability of aphids (Aphis fabae) harbouring protective facultative endosymbionts (Hamiltonella defensa) to resist parasitism by Hymenopteran parasitoids (Lysiphlebus fabarum). Furthermore, we investigated whether heat shocks can modify previously observed genotype-by-genotype (G x G) interactions between different endosymbiont isolates and parasitoid genotypes. Lines of genetically identical aphids possessing different isolates of H. defensa were exposed to one of two heat shock regimes (35°C and 39°C) or to a control temperature (20°C) before exposure to three different asexual lines of the parasitoids. We observed strong G x G interactions on parasitism rates, reflecting the known genetic specificity of symbiont-conferred resistance, and we observed a significant G x G x E interaction induced by heat shocks. However, this three-way interaction was mainly driven by the more extreme heat shock (39°C), which had devastating effects on aphid lifespan and reproduction. Restricting the analysis to the more realistic heat shock of 35°C, the G x G x E interaction was weaker (albeit still significant), and it did not lead to any reversals of the aphid lines'' susceptibility rankings to different parasitoids. Thus, under conditions feasibly encountered in the field, the relative fitness of different parasitoid genotypes on hosts protected by particular symbiont strains remains mostly uncomplicated by heat stress, which should simplify biological control programs dealing with this system.     

Alarm scent-marking during predatory attempts in the Cabrera vole (Microtus cabrerae Thomas, 1906)

The alarm pheromones often released by animals under stressful situations seem to elicit behavioral changes in conspecifics, which in the appropriate context can be viewed as anti-predatory responses. However, the releasing of alarm pheromones associated with predatory events has not been demonstrated in mammals. In the current study with wild-caught Cabrera voles, we carried out experiments in the laboratory and in the field to assess the release of alarm pheromones in scent-marks during simulated predatory events and disclose their effects on conspecifics. We first conducted an assay wherein voles where let to scent-mark a clean substrate in the absence of disturbance (control) and under the simulation of predatory events. Contrarily to the control, no fecal boli were released and the area marked with urine was significantly larger during the predatory simulation. In a subsequent assay, we assessed the voles’ preference between urine-marks released under predatory simulation and in control conditions. Voles showed a significant preference by control substrates. Finally, a third assay was carried out in the vole’s habitat wherein the individual activity was monitored by radio-tracking before and after placement of urine-marks obtained during the conditions described above. The vole’s activity was only reduced near the urine-marks released during the simulated predatory events. The results suggest that: (1) during predatory attempts, Cabrera voles release an alarm pheromone in their urine-marks; (2) the putative alarm pheromone reduces the voles’ activity in the surroundings of the marked area; (3) the putative alarm pheromone persists in the field affecting conspecifics’ activity for several days.     

Srf-dependent paracrine signals produced by myofibers control satellite cell-mediated skeletal muscle hypertrophy

Adult skeletal muscles adapt their fiber size to workload. We show that serum response factor (Srf) is required for satellite cell-mediated hypertrophic muscle growth. Deletion of Srf from myofibers and not satellite cells blunts overload-induced hypertrophy, and impairs satellite cell proliferation and recruitment to pre-existing fibers. We reveal a gene network in which Srf within myofibers modulates interleukin-6 and cyclooxygenase-2/interleukin-4 expressions and therefore exerts a paracrine control of satellite cell functions. In Srf-deleted muscles, in vivo overexpression of interleukin-6 is sufficient to restore satellite cell proliferation but not satellite cell fusion and overall growth. In contrast cyclooxygenase-2/interleukin-4 overexpression rescue satellite cell recruitment and muscle growth without affecting satellite cell proliferation, identifying altered fusion as the limiting cellular event. These findings unravel a role for Srf in the translation of mechanical cues applied to myofibers into paracrine signals, which in turn will modulate satellite cell functions and support muscle growth.     

Molecular etiology of atherogenesis--in vitro induction of lipidosis in macrophages with a new LDL model

Background

Atherosclerosis starts by lipid accumulation in the arterial intima and progresses into a chronic vascular inflammatory disease. A major atherogenic process is the formation of lipid-loaded macrophages in which a breakdown of the endolysomal pathway results in irreversible accumulation of cargo in the late endocytic compartments with a phenotype similar to several forms of lipidosis. Macrophages exposed to oxidized LDL exihibit this phenomenon in vitro and manifest an impaired degradation of internalized lipids and enhanced inflammatory stimulation. Identification of the specific chemical component(s) causing this phenotype has been elusive because of the chemical complexity of oxidized LDL.

Methodology/Principal Findings

Lipid “core aldehydes" are formed in oxidized LDL and exist in atherosclerotic plaques. These aldehydes are slowly oxidized in situ and (much faster) by intracellular aldehyde oxidizing systems to cholesteryl hemiesters. We show that a single cholesteryl hemiester incorporated into native, non-oxidized LDL induces a lipidosis phenotype with subsequent cell death in macrophages. Internalization of the cholesteryl hemiester via the native LDL vehicle induced lipid accumulation in a time- and concentration-dependent manner in “frozen" endolysosomes. Quantitative shotgun lipidomics analysis showed that internalized lipid in cholesteryl hemiester-intoxicated cells remained largely unprocessed in those lipid-rich organelles.

Conclusions/Significance

The principle elucidated with the present cholesteryl hemiester-containing native-LDL model, extended to other molecular components of oxidized LDL, will help in defining the molecular etiology and etiological hierarchy of atherogenic agents.     

Anti-atherogenic and anti-angiogenic activities of polyphenols from propolis

Propolis is a polyphenol-rich resinous substance extensively used to improve health and prevent diseases. The effects of polyphenols from different sources of propolis on atherosclerotic lesions and inflammatory and angiogenic factors were investigated in LDL receptor gene (LDLr?/?) knockout mice. The animals received a cholesterol-enriched diet to induce the initial atherosclerotic lesions (IALs) or advanced atherosclerotic lesions (AALs). The IAL or AAL animals were divided into three groups, each receiving polyphenols from either the green, red or brown propolis (250 mg/kg per day) by gavage. After 4 weeks of polyphenol treatment, the animals were sacrificed and their blood was collected for lipid profile analysis. The atheromatous lesions at the aortic root were also analyzed for gene expression of inflammatory and angiogenic factors by quantitative real-time polymerase chain reaction and immunohistochemistry. All three polyphenol extracts improved the lipid profile and decreased the atherosclerotic lesion area in IAL animals. However, only polyphenols from the red propolis induced favorable changes in the lipid profiles and reduced the lesion areas in AAL mice. In IAL groups, VCAM, MCP-1, FGF, PDGF, VEGF, PECAM and MMP-9 gene expression was down-regulated, while the metalloproteinase inhibitor TIMP-1 gene was up-regulated by all polyphenol extracts. In contrast, for advanced lesions, only the polyphenols from red propolis induced the down-regulation of CD36 and the up-regulation of HO-1 and TIMP-1 when compared to polyphenols from the other two types of propolis. In conclusion, polyphenols from propolis, particularly red propolis, are able to reduce atherosclerotic lesions through mechanisms including the modulation of inflammatory and angiogenic factors.