A twisted tRNA intermediate sets the threshold for decoding

Putting together consistent cryo-EM structure, transient kinetic and mutant tRNA suppressor data, it appears that a deformed or waggling aminoacyl-tRNA is the critical transitional structure examined by the ribosome during decoding at the A site. The unusual conformation may be required for effective proofreading of the codon-anticodon complex.     

Correlation between molecular markers and adaptively significant genetic variation in Bromus tectorum (Poaceae), an inbreedingannual grass

Single sequence repeat (SSR) and amplified fragment length polymorphic (AFLP) molecular marker genotypes in cheatgrass (Bromus tectorum) were compared to published data on phenotypic variation in seed dormancy, vernalization requirement, and resistance to the pathogen Ustilago bullata. Several features of cheatgrass facilitated this study: it is a recent invader in the western United States, has considerable phenotypic polymorphism, and is an obligate self-pollinator. Forty self-pollinating lines from four populations common to the three phenotypic data sets were analyzed for molecular genetic variation using seven SSR loci and 31 AFLP loci. We examined correlations between distance matrices using the Mantel test for each pair of studies. The two molecular data sets were significantly correlated (r = 0.636). The AFLP markers often distinguished among several lines with identical SSR genotypes. The AFLP data were also significantly correlated with the phenotypic data (r values from 0.4640 to 0.5658), but the SSR data were much more highly correlated (r values from 0.677 to 0.844). The difference between molecular marker systems was especially notable when an outlier population from Potosi Pass, Nevada, was excluded from the analysis. These results suggest that SSR markers may be good surrogates for phenotypic traits in population genetic studies of strongly inbreeding species such as cheatgrass.     

Iliopsoas and gluteal muscles are asymmetric in tennis players but not in soccer players

Purpose

To determine the volume and degree of asymmetry of iliopsoas (IL) and gluteal muscles (GL) in tennis and soccer players.

Methods

IL and GL volumes were determined using magnetic resonance imaging (MRI) in male professional tennis (TP) and soccer players (SP), and in non-active control subjects (CG) (n = 8, 15 and 6, respectively).

Results

The dominant and non-dominant IL were hypertrophied in TP (24 and 36%, respectively, P<0.05) and SP (32 and 35%, respectively, P<0.05). In TP the asymmetric hypertrophy of IL (13% greater volume in the non-dominant than in the dominant IL, P<0.01) reversed the side-to-side relationship observed in CG (4% greater volume in the dominant than in the contralateral IL, P<0.01), whilst soccer players had similar volumes in both sides (P = 0.87). The degree of side-to-side asymmetry decreased linearly from the first lumbar disc to the pubic symphysis in TP (r = −0.97, P<0.001), SP (r = −0.85, P<0.01) and CG (r = −0.76, P<0.05). The slope of the relationship was lower in SP due to a greater hypertrophy of the proximal segments of the dominant IL. Soccer and CG had similar GL volumes in both sides (P = 0.11 and P = 0.19, for the dominant and contralateral GL, respectively). GL was asymmetrically hypertrophied in TP. The non-dominant GL volume was 20% greater in TP than in CG (P<0.05), whilst TP and CG had similar dominant GL volumes (P = 0.14).

Conclusions

Tennis elicits an asymmetric hypertrophy of IL and reverses the normal dominant-to-non-dominant balance observed in non-active controls, while soccer is associated to a symmetric hypertrophy of IL. Gluteal muscles are asymmetrically hypertrophied in TP, while SP display a similar size to that observed in controls. It remains to be determined whether the different patterns of IL and GL hypertrophy may influence the risk of injury.     

Variation in multiple traits of vegetative and reproductive seagrass tissues influences plant–herbivore interactions

Plant–herbivore interactions have strong ecological and evolutionary consequences, but have been traditionally overlooked in marine higher plants. Despite recent advances in seagrass ecology that highlight the importance of herbivory, the mechanisms that regulate the feeding behaviour of seagrass consumers remain largely unknown. Herbivores have been shown to reduce the sexual reproductive success of seagrasses through direct consumption of inflorescences and seeds, but we know little about intraspecific variation in susceptibility to grazing of different seagrass tissues. We contrasted the relative palatability of reproductive and vegetative tissues of the temperate seagrass Posidonia oceanica in the field, and we assessed the feeding preferences among these tissues of the main consumers of the plant, the fish Sarpa salpa and the urchin Paracentrotus lividus. Moreover, we identified the plant traits that explained the observed feeding behaviour. We provide strong evidence for herbivore selectivity among seagrass tissues. In the field, 70–90% of inflorescences were damaged by herbivores compared to 3–60% of leaves of similar age. In feeding assays, the urchin P. lividus showed over a twofold preference for reproductive tissue at various stages of development. By contrast, we detected no feeding activity on either leaves or inflorescences from the fish S. salpa, which is known to migrate to deeper waters soon after flowering starts and during the period of fruit maturation. Despite being the preferred food of urchins, inflorescences were chemically defended, had higher levels of phenolics and lower nutrient and calorific content than leaves. We experimentally demonstrated that leaf structural defences are the primary factor in determining urchin feeding preferences. Removal of plant structure results in a drastic shift in urchin selectivity towards the most nutritious and less chemically defended leaf tissue, indicating that multiple mechanisms of defence to herbivory may coexist in seagrasses.     

Morphological alterations and NO-synthase expression in the heart after continuous light exposure of rats

Although exposure to continuous light is associated with hypertension and modulates the outcome of ischemia-reperfusion injury, less attention has been paid to its effects on cardiac morphology. We investigated whether 4-week exposure of experimental rats to continuous 24 h/day light can modify cardiac morphology, with focus on heart weight, fibrosis and collagen I/III ratio in correlation with NO-synthase expression. Two groups of male adult Wistar rats were studied: controls exposed to normal light/dark cycle (12 h/day light, 12 h/day dark) and rats exposed to continuous light. After 4 weeks of treatment the absolute and the relative heart weights were determined and myocardial fibrosis and collagen type I/III ratio were evaluated using picrosirius red staining. Endothelial and inducible NO-synthase expression was detected immunohistochemically. The exposure of rats to continuous light resulted in an increase of body weight with proportionally increased heart weight. Myocardial fibrosis remained unaffected but collagen I/III ratio increased. Neither endothelial nor inducible NO-synthase expression was altered in light-exposed rats. We conclude that the loss of structural homogeneity of the myocardium in favor of collagen type I might increase myocardial stiffness and contribute to functional alterations after continuous light exposure.     

Contribution of two ionotropic purinergic receptors to ATP responses in submandibular gland ductal cells

The effect of extracellular ATP on salivary gland function was compared in wild-type (WT) and P2X(7) knockout (KO) mice. The increase in the intracellular concentration of calcium ([Ca(2+)](i)) in response to carbachol was similar in submandibular ductal cells of WT and KO mice. ATP and its analog, benzoyl-ATP, induced a sustained increase in the [Ca(2+)](i) in WT animals. In KO mice, ATP slightly and transiently increased the [Ca(2+)](i) and benzoyl-ATP had no effect. The response to ATP of WT but not KO mice was blocked by KN-62, Coomassie blue and magnesium. The small response of ATP observed in KO mice was completely blocked in the absence of extracellular calcium, unchanged by U73122 and potentiated by ivermectin indicating the probable involvement of a P2X(4) receptor. A RT-PCR and a Western blot confirmed the presence of these receptors in ducts of both WT and KO mice. ATP increased the permeability of the cells to ethidium bromide and stimulated a phospholipase A(2) activity in WT but not KO mice. Mice submandibular gland cells secreted IL-1beta but this secretion was not modified by ATP and was similar in both groups of animals. The volume of saliva provoked by pilocarpine and the concentration of proteins, sodium and chloride in this saliva was similar in both groups of animals. The concentration of potassium was higher in KO mice. We can conclude that the major purinergic receptors expressed in mice submandibular ductal cells are P2X(7) receptors but that P2X(4) receptors are also involved in some ATP effects.     

Integrins activate trimeric G proteins via the nonreceptor protein GIV/Girdin

Signal transduction via integrins and G protein–coupled receptors is critical to control cell behavior. These two receptor classes have been traditionally believed to trigger distinct and independent signaling cascades in response to extracellular cues. Here, we report a novel mechanism of integrin signaling that requires activation of the trimeric G protein Gαi by the nonreceptor guanine nucleotide exchange factor (GEF) GIV (also known as Girdin), a metastasis-associated protein. We demonstrate that GIV enhances integrin-dependent cell responses upon extracellular matrix stimulation and makes tumor cells more invasive. These responses include remodeling of the actin cytoskeleton and PI3K-dependent signaling, resulting in enhanced haptotaxis and invasion. We show that both GIV and its substrate Gαi3 are recruited to active integrin complexes and that tumor cells engineered to express GEF-deficient GIV fail to transduce integrin signals into proinvasive responses via a Gβγ-PI3K axis. Our discoveries delineate a novel mechanism by which integrin signaling is rewired during metastasis to result in increased tumor invasiveness.     

Pedaling power and speed production vs. technical factors and track difficulty in bicycle motocross cycling

Mateo, M, Blasco-Lafarga, C, and Zabala, M. Pedaling power and speed production vs. technical factors and track difficulty in BMX cycling. J Strength Cond Res 25(12): 3248-3256, 2011-This article analyzes whether there is a determined profile in the production of cyclic and acyclic periods in relation to the phases of a bicycle motocross (BMX) race and whether this profile is related to the variables, Difficulty of track and Techniques used. After an initial test for determining maximum pedaling power (Pmax), 9 athletes belonging to the Spanish national team completed 3 series of 3 different types of races: (a) Complete track without pedaling; (b) Track, pedaling only at the gate start; and (c) track with free pedaling. The triple test was carried out over 3 days and on different level tracks: (a) high difficulty (HD), (b) medium difficulty (MD), and (c) low difficulty (LD). Our results show that average peak power applied in the BMX race was 85.21 ± 2.15% Pmax, coming down to 73.02 ± 18.38% at the gate start and to 51.37 ± 15.84% on the first straight. On the other hand, mean power (MP) in the BMX race is 33.79 ± 8.60% MPmax, with statistically significant differences in relation to the difficulty of the track (p < 0.000; 0.009; higher in the easiest). The mean velocity developed is 34.21 ± 1.0 km·h with significant differences (p < 0.000) in relation to the difficulty of the track. Acyclic efforts accounted for 86.3%, and cyclic efforts accounted for the remaining 16.7% of the overall performance in the race, with differences in relation to the difficulty of the track (p ≤ 0.003). Both power profile and performance (measured as velocity) are dependent on the phases and techniques of the race and are significantly affected by the level of difficulty of the track. The greater the technical level of the track, the lesser the possibility of developing cyclic power and vice versa.