We explore the collider relevance of a charge-radius coupling among light mesons in composite Higgs models. In particular, we focus of a coupling of the photon to the composite Higgs and a composite ...singlet, arising from isospin violation in the underlying theory. This coupling offers a deep probe of the composite nature of the Higgs mechanism, being sensitive to the electromagnetic and weak isospin structure of its constituents. The main collider effect consists in the production of the Higgs boson in association with a light composite pseudo-scalar. We present an exploratory cut-and-count analysis at hadron colliders, like the LHC, showing that an efficient background suppression can be achieved. More sophisticated techniques, however, are necessary to select a sufficient number of signal events, due to the small production rates. This justifies further investigation of this channel, which is highly complementary to other searches for compositeness in the Higgs sector.
A better understanding of the mechanisms underlying neuronal death in cerebral ischemia is required for the development of stroke therapies. Here we analyze the contribution of the ...tropomyosin-related kinase B (TrkB) neurotrophin receptor to excitotoxicity, a primary pathological mechanism in ischemia, which is induced by overstimulation of glutamate receptors of the N-methyl-D-aspartate type. We demonstrate a significant modification of TrkB expression that is strongly associated with neurodegeneration in models of ischemia and in vitro excitotoxicity. Two mechanisms cooperate for TrkB dysregulation: (1) calpain-processing of full-length TrkB (TrkB-FL), high-affinity receptor for brain-derived neurotrophic factor, which produces a truncated protein lacking the tyrosine-kinase domain and strikingly similar to the inactive TrkB-T1 isoform and (2) reverse regulation of the mRNA of these isoforms. Collectively, excitotoxicity results in a decrease of TrkB-FL, the production of truncated TrkB-FL and the upregulation of TrkB-T1. A similar neuro-specific increase of the TrkB-T1 isoform is also observed in stroke patients. A lentivirus designed for both neuro-specific TrkB-T1 interference and increased TrkB-FL expression allows recovery of the TrkB-FL/TrkB-T1 balance and protects neurons from excitotoxic death. These data implicate a combination of TrkB-FL downregulation and TrkB-T1 upregulation as significant causes of neuronal death in excitotoxicity, and reveal novel targets for the design of stroke therapies.
Omnivory is important in determining species interactions and weakening possible trophic cascade effects. The present study is focused on determining if an indirect effect of fish presence (trophic ...cascade effect) can be observed regardless of a high abundance of omnivores. With this aim a field experiment was carried out in a Mediterranean salt marsh. The natural top predator of these systems is a small and endangered fish, the Iberian toothcarp (Aphanius iberus). We wanted to assess if the presence of this fish could trigger a trophic cascade in the aquatic community. Six mesocosms were installed in a salt marsh lagoon without A. iberus presence, for two months. Twenty adult females of A. iberus were added to three mesocosms (fish treatment), while the other three were used as control (without any A. iberus addition). Physical and chemical water characteristics, as well as aquatic invertebrate samples (from bacteria to amphipoda, the largest organisms detected beside fish) were collected at the begining and the end of the experiment. To assess the trophic position of organisms, stable isotope analyses were used (13C and 15N). Our results show that the presence of A. iberus produces a trophic cascade even though only two trophic levels were differentiated by the stable isotope analysis. Body size appears to be determinant, since trophic interactions observed within the food web were mainly body-size dependent. Moreover, an unexpected positive but weak effect of A. iberus on macrophyte biomass was observed, caused probably by the decrease of small phytoplankton abundance. This effect may suppose an advantage for A. iberus, since macrophytes provide refuge and a food supply for this small fish.
► A small fish produces a trophic cascade on plankton of a Mediterranean salt marsh. ► Omnivory has an important role in these food webs. ► The trophic cascade is a result of size-dependent interactions amongst organisms. ► Aphanius iberus has weak but positive effect on macrophyte biomass.
Jellyfish can act as planktonic top predators, and their effects may cause drastic changes in the plankton structure of marine and freshwater systems. However, the top predator effects may not ...necessarily be the same in species-poor habitats as they are in species-rich habitats. The present study analyses the effects of the small lacunae jellyfish Odessia maeotica in a species-poor habitat, Mediterranean salt marshes in the wetlands of Emporda (NE Iberian Peninsula). A field experiment was carried out in March 2008 to assess the direct and indirect effects of O. maeotica on plankton composition. Our results show that the presence of O. maeotica changed the plankton composition through top-down effects. Changes were strong in zooplankton, because O. maeotica can suppress almost the entire trophic level of large zooplankton (>50 km). Weak indirect effects on phytoplankton composition were observed as well. When O. maeotica was present, changes in the relative abundance of the phytoplankton species were found, but there was no net increase in phytoplankton biomass. Our results suggest that these weak indirect effects may be the result of trophic cascade effects coupled with the oligotrophic conditions of these salt marshes. Thus, trophic cascade effects lead to an increase in ciliate biomass, and these ciliates would feed on small algae (jellyfish-copepods-ciliates-small algae), while oligotrophic conditions would prevent increases in algal biomass.
Fish predation has an important role structuring benthic and planktonic assemblages in shallow waters. Habitat complexity may mitigate the effect of fish predation, thus reducing prey–predator ...encounters and prey capture ability. In this respect, benthic organisms may be less affected by predation than planktonic organisms because macrophytes would increase habitat complexity, thus providing a physical refuge. However, certain small fish may move and live within vegetation, resulting in an increase in prey–predator encounters, and so physical refuges provided by macrophytes would be less effective. To test the effects of small fish on aquatic invertebrates, we performed a field experiment using mesocosms in a Mediterranean salt marsh, using
Aphanius iberus as the small fish species (<
5
cm) and
Ruppia cirrhosa as the dominant macrophyte. Although,
A. iberus preys on benthic and planktonic organisms, it has traditionally been described as a benthic species. Hence, a stronger effect on benthos is expected if habitat complexity does not reduce the predation ability of this small fish. We therefore analyzed and compared the strength of the effects of
A. iberus on both benthic and planktonic organisms. The fish was found to have stronger effects on planktonic than benthic organisms. The presence of
A. iberus was coincident with a decline in the abundance of large water-column invertebrates such as gammarids and jellyfish, and an increase in the abundance of medium-sized plankton. The total biomass of the benthic assemblage increased when
A. iberus was present. These results suggest that aquatic invertebrates of Mediterranean salt marshes may use macrophytes as refuge from small fish species.
► Predation of an omnivorous small fish (
Aphanius iberus) is important in plankton and benthos of Mediterranean salt marsh. ►
A. iberus has more effects on plankton than on benthos because habitat complexity allows to avoid fish predation. ► Presence of
A. iberus changes diversity and size structure of plankton.
Conservation biology is mainly interested in prioritizing sites on the basis of their high biodiversity. Although species richness is a commonly used criterion, it does not take other crucial aspects ...of identifying conservation priority sites into account, such as rarity or taxonomic distinctness. Additionally, management efforts are usually focused on the conservation of a small number of species, mainly vertebrates. However, the biodiversity patterns of these faunal groups and the main factors which determine them cannot be generalized to other faunal groups (e.g. aquatic invertebrates). Therefore, the objectives of the present study are: (1) to compare the response of 11 biodiversity metrics in order to know which ones are redundant, (2) to identify key environmental factors for biodiversity, and (3) to find out whether sites with high biodiversity values also have a good habitat condition and high protection status. The study was done at assemblage level (crustaceans and insects) in 91 wetlands in the NE Iberian Peninsula. Regression tree models were used to identify the key factors influencing biodiversity, including water, wetland and landscape characteristics as explanatory variables. Generalized Linear models were used to establish the relationship between biodiversity metrics and protection status and habitat condition. The results obtained by the two sampled seasons were compared. Conductivity was the main factor influencing biodiversity metrics. Positive significant relationships were found between some biodiversity metrics and wetland habitat condition, whereas there were none for protection status, indicating the inadequacy of conservation policies to protect wetland aquatic invertebrate biodiversity.
The aim of this study was to evaluate and compare the dynamics of plant, crustacean, and coleopteran assemblages living in Mediterranean temporary wetlands. We measured assemblage parameters (species ...richness, diversity and abundance) and succession rates during the hydroperiod for each assemblage analysed. Moreover, the species were classified according to their affinity to the temporary aquatic habitats in order to study if each assemblage had similar patterns among species groups of habitat affinity. Only among plants, the temporary water species were dominant in terms of species richness, diversity or abundance. Cross-taxon congruence between plants and crustaceans, previously reported, was not confirmed when temporal succession was taken into account, suggesting different temporal patterns for the studied taxa. Plants showed the lowest level of successional changes and significant differences between local and regional diversity. In contrast, coleopterans had the highest level of successional changes and a different relationship between local and regional diversity, with regard to the hydroperiod phase. Finally, crustaceans had intermediate levels of successional changes and the relationship between the local and regional diversity during the hydroperiod was dependent on the type of organism (generalist vs. temporary water species). All of this gave evidence of the difficulties to use one taxonomic group in order to elucidate the ecological patterns of other groups.
Oliver, GD, Washington, JK, Barfield, JW, Gascon, SS, and Gilmer, G. Quantitative analysis of proximal and distal kinetic chain musculature during dynamic exercises. J Strength Cond Res 32(6): ...1545-1553, 2018-Proximal to distal sequencing for the dynamic movement of throwing is dependent on the movement and stability of the lumbopelvic-hip complex (LPHC) and scapula. Although the need for proximal stability for distal mobility has been vastly documented, pre-throwing programs tend to focus on the traditional rotator cuff activation exercises before long toss. Thus, it was the purpose of this study to describe muscle activations of LPHC stabilizing musculature (bilateral gluteus medius and maximus) and scapular stabilizing musculature (dominant side latissimus dorsi, lower trapezius, upper trapezius, and serratus anterior) during 5 kinetic chain exercises that could be implemented in a throwing program. It was hypothesized that both the LPHC and the scapular stabilizing musculature would exhibit moderate to high activation during all the selected kinetic chain exercises. Nineteen healthy college students (23.2 ± 7.2 years; 176.7 ± 17.9 cm; 78.0 ± 28.6 kg) participated. Surface electromyography was used to measure muscle activity in the LPHC and scapular stabilizing musculature during 5 kinetic chain exercises. A nonparametric Friedman test revealed significantly different muscle activations as a factor of exercise for each muscle, χ(18) = 417.220, p < 0.001. The 5 kinetic chain exercises successfully elicited moderate to high muscle activation in all musculature, except the upper trapezius. Because greater muscle activation of the LPHC and scapular stabilizers are crucial during a throwing task, these exercises are recommended for pre-throwing program implementation because they efficiently prepare the stabilizing musculature for lengthy or strenuous throwing tasks, resulting in a potential decrease in injury susceptibility.
The purpose of this study was to examine how lumbopelvic-hip complex (LPHC) stability, via knee valgus, affects throwing kinematics during a team handball jump shot.
LPHC stability was classified ...using the value of knee valgus at the instant of landing from the jump shot. If a participant displayed knee valgus of 17° or greater, they were classified as LPHC unstable. Stable and unstable athletes’ throwing mechanics were compared.
Twenty female team handball athletes (26.5±4.7years; 1.75±0.04m; 74.4±6.4kg; experience level: 4.8±4.1 years) participated. An electromagnetic tracking system was used to collect kinematic data while participants performed three 9-m jump shots. The variables considered were kinematics of the pelvis, trunk, and shoulder; and segmental speeds of the pelvis, torso, humeral, forearm, and ball velocities. Data were analyzed across four events: foot contact, maximum shoulder external rotation, ball release, and maximum shoulder internal rotation.
Statistically significant differences were found between groups in pelvis, trunk, humerus, and forearm velocities at all events (p≤0.05). Specifically, the unstable group displayed significantly slower speeds.
These findings suggest the difference in throwing mechanics are affected by LPHC instability for this select group of female team handball athletes. These differences infer an increased risk of injury in the upper and lower extremities when landing from a jump shot because of the energy losses throughout the kinetic chain and lack of utilization of the entire chain. It is recommended that further investigations also consider muscle activation throughout the throwing motion.
The N-methyl-D-aspartate receptor (NMDAR) is central to physiological and pathological functioning of neurons. Although promising results are beginning to be obtained in the treatment of dementias, ...clinical trials with NMDAR antagonists for stroke, trauma and neurodegenerative disorders, such as Hungtinton's disease, have failed before. In order to design effective therapies to prevent excitotoxic neuronal death, it is critical to characterize the consequences of excessive NMDAR activation on its expression and function. Previous data have reported partial downregulation of the NR1 and NR2B receptor subunits in response to excitotoxicity and cerebral ischemia. However, the effect of NMDAR overactivation on NR2A, a subunit fundamental to synaptic transmission and neuronal survival, is still elusive. In this study, we report the rapid and extensive proteolytic processing of NR2A, together with the scaffolding protein postsynaptic density-95 (PSD-95), induced by excitotoxic stimulation of cortical neurons in vitro and by transient focal cerebral ischemia. Processing of the C terminus of NR2A is irreversibly induced by brief agonist exposure of NR2B-containing receptors, and requires calcium influx and the activity of calpain, also responsible for PSD-95 cleavage. The outcome is a truncated NR2A subunit that is stable and capable to interact with NR1 at the surface of neurons, but lacking the structural domains required for association with scaffolding, downstream signaling and cytoskeletal proteins. Therefore, a rapid and significant uncoupling of synaptic NMDARs from downstream survival pathways is expected to occur during ischemia. This novel mechanism induced by excitotoxicity helps to explain the failure of most therapies based on NMDAR antagonists.
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