The influence of nicotine on granulocytic differentiation – Inhibition of the oxidative burst and bacterial killing and increased matrix metalloproteinase-9 release

Background  

Neutrophils leave the bone marrow as terminally differentiated cells, yet little is known of the influence of nicotine or other tobacco smoke components on neutrophil differentiation. Therefore, promyelocytic HL-60 cells were differentiated into neutrophils using dimethylsulfoxide in the presence and absence of nicotine (3-(1-methyl-2-pyrrolidinyl) pyridine). Differentiation was evaluated over 5 days by monitoring terminal differentiation markers (CD11b expression and formazan deposition); cell viability, growth phase, kinetics, and apoptosis; assessing cellular morphology and ultrastructure; and conformational changes to major cellular components. Key neutrophil effector functions (oxidative burst, bacterial killing, matrix metalloproteinase release) were also examined.     

Exploiting host compensatory responses: the 'must' of manipulation?

Parasite-induced alterations of the host phenotype have been reported in many systems. These changes are traditionally categorized into three kinds of phenomena: secondary outcomes of infection with no adaptive value, host adaptations that reduce the detrimental consequences of infection and parasitic adaptations that facilitate transmission. However, this categorization is a simple view, and host modifications should be considered as co-evolved traits, rather than a total takeover. Here, we present a novel scenario of manipulation, which has considerable potential to resolve issues that are specific to the evolution of behavioural alterations induced by parasites. It is proposed that certain parasites affect fitness-related traits in their hosts to trigger host compensatory responses because these responses can meet the transmission objectives of parasites.     

Amphioxus postembryonic development reveals the homology of chordate metamorphosis

Most studies in evolution are centered on how homologous genes, structures, and/or processes appeared and diverged. Although historical homology is well defined as a concept, in practice its establishment can be problematic, especially for some morphological traits or developmental processes. Metamorphosis in chordates is such an enigmatic character. Defined as a spectacular postembryonic larva-to-adult transition, it shows a wide morphological diversity between the different chordate lineages, suggesting that it might have appeared several times independently. In vertebrates, metamorphosis is triggered by binding of the thyroid hormones (THs) T(4) and T(3) to thyroid-hormone receptors (TRs). Here we show that a TH derivative, triiodothyroacetic acid (TRIAC), induces metamorphosis in the cephalochordate amphioxus. The amphioxus TR (amphiTR) mediates spontaneous and TRIAC-induced metamorphosis because it strongly binds to TRIAC, and a specific TR antagonist, NH3, inhibits both spontaneous and TRIAC-induced metamorphosis. Moreover, as in amphibians, amphiTR expression levels increase around metamorphosis and are enhanced by THs. Therefore, TH-regulated metamorphosis, mediated by TR, is an ancestral feature of all chordates. This conservation of a regulatory network supports the homology of metamorphosis in the chordate lineage.     

The Chikungunya threat: an ecological and evolutionary perspective

Chikungunya virus (CHIKV) is an emerging mosquito-borne alphavirus. Although primarily African and zoonotic, it is known chiefly for its non-African large urban outbreaks during which it is transmitted by the same vectors as those of Dengue viruses. Unlike Dengue viruses, CHIKV displays a re-emergence pattern that closely depends on long-distance migrations including recent re-immigrations from African (putatively zoonotic) sources. Genus-based differences also emerged when comparing the evolution of Dengue-related (Flaviviruses) and of CHIKV-related (Alphaviruses) arboviruses. In this review, we discuss current information on CHIKV genetics, ecology and human infection. Further investigations on African CHIKV ecology and the differences between Flavivirus and Alphavirus members in adaptive changes and evolutionary constraints are likely to help delineate the potential of further CHIKV (re-)emergence.     

Changes in the decapod fauna of an Arctic fjord during the last 100 years (1908–2007)

Whereas Arctic benthic decapods are not a species-rich group, they can dominate the local epifauna and play important roles in the ecosystem. We studied the decapod fauna from Isfjorden (Svalbard, Norway, 78°N) by sampling from 22 stations and comparing with 50 and 100-year-old data from the same localities. Our data provide no evidence of changes in the species composition of decapods during the last 50 years. Hence, we do not observe the poleward shift of species found in several pelagic communities in the North Atlantic. However, there is statistical evidence for changes in the community structure between 1908 and both 1958 and 2007. The main change is a shift towards communities more dominated by the spider crab Hyas araneus and the hermit crab Pagurus pubescens in 2007, and with a corresponding decrease in the two shrimp species Lebbeus polaris and Spirontocaris spinus. These shrimps are specialist predators compared to the more opportunistic, scavenging crabs. We argue that increased disturbance levels may be a causal factor behind the observed community change, with likely sources of disturbance including trawling and climatic fluctuations.     

The vastus lateralis neuromuscular activity during all-out cycling exercise

ObjectiveThe objective of this work was to study modifications in motor control through surface electromyographic (sEMG) activity during a very short all-out cycling exercise.MethodsTwelve male cyclists (age 23 ± 4 years) participated in this study. After a warm-up period, each subject performed three all-out cycling exercises of 6 s separated by 2 min of complete rest. This protocol was repeated three times with a minimum of 2 days between each session. The braking torque imposed on cycling motion was 19 N m. The sEMG of the vastus lateralis was recorded during the first seven contractions of the sprint. Time–frequency analysis of sEMG was performed using continuous wavelet transform. The mean power frequency (MPF, qualitative modifications in the recruitment of motor units) and signal energy (a quantitative indicator of modifications in the motor units recruitment) were computed for the frequency range 10–500 Hz.ResultssEMG energy increased (P ? 0.05) between contraction number 1 and 2, decreased (P ? 0.05) between contraction number 2 and 3 then stabilized between contraction number 3 and 7 during the all-out test. MPF increased (P ? 0.05) during the all-out test. This increase was more marked during the first two contractions.ConclusionsThe decrease in energy and the increase in the sEMG MPF suggest a large spatial recruitment of motor units (MUs) at the beginning of the sprint followed by a preferential recruitment of faster MUs at the end of the sprint, respectively.