Muscle activation strategies during strength training with heavy loading vs. repetitions to failure

Going to failure, or not, has probably been one of the most debated issues during the history of strength training. However, few studies have directly compared the physiological effect of failure vs. nonfailure strength training. The purpose of this study was to evaluate muscle activation strategies with electromyography (EMG) during heavy repetitions vs. repetitions to failure with lighter resistance. Fifteen healthy untrained women performed a set with heavy loading (3 repetition maximum [RM]) and a set of repetitions to failure with lower resistance (～15 RM) during lateral raise with elastic tubing. Electromyographic amplitude and median power frequency of specific shoulder and neck muscles were analyzed, and the BORG CR10 scale was used to rate perceived loading immediately after each set of exercise. During the failure set, normalized EMG was significantly lower during the first repetition and significantly higher during the latter repetitions compared with the heavy 3-RM set (p < 0.05). Normalized EMG for the examined muscles increased throughout the set to failure in a curvilinear fashion--e.g., for the trapezius from 86 to 124% maximal voluntary contraction (p < 0.001)--and reached a plateau during the final 3-5 repetitions before failure. Median power frequency for all examined muscles decreased throughout the set to failure in a linear fashion, indicating progressively increasing fatigue. In conclusion, going to complete failure during lateral raise is not necessary to recruit the entire motor unit pool in untrained women--i.e., muscle activity reached a plateau 3-5 repetitions from failure with an elastic resistance of approximately 15 RM. Furthermore, strengthening exercises performed with elastic tubing seem to be an efficient resistance exercise and a feasible and practical alternative to traditional resistance equipment.     

Solution structure of C-terminal Escherichia coli translation initiation factor IF2 by small-angle X-ray scattering

Initiation of protein synthesis in bacteria involves the combined action of three translation initiation factors, including translation initiation factor IF2. Structural knowledge of this bacterial protein is scarce. A fragment consisting of the four C-terminal domains of IF2 from Escherichia coli was expressed, purified, and characterized by small-angle X-ray scattering (SAXS), and from the SAXS data, a radius of gyration of 43 +/- 1 A and a maximum dimension of approximately 145 A were obtained for the molecule. Furthermore, the SAXS data revealed that E. coli IF2 in solution adopts a structure that is significantly different from the crystal structure of orthologous aIF5B from Methanobacterium thermoautotrophicum. This crystal structure constitutes the only atomic resolution structural knowledge of the full-length factor. Computer programs were applied to the SAXS data to provide an initial structural model for IF2 in solution. The low-resolution nature of SAXS prevents the elucidation of a complete and detailed structure, but the resulting model for C-terminal E. coli IF2 indicates important structural differences between the aIF5B crystal structure and IF2 in solution. The chalice-like structure with a highly exposed alpha-helical stretch observed for the aIF5B crystal structure was not found in the structural model of IF2 in solution, in which domain VI-2 is moved closer to the rest of the protein.     

Effects of Chemical Cues on Foraging in Damselfly Larvae, <Emphasis Type="Italic">Enallagma antennatum</Emphasis>

Animals experiencing a trade-off between predation risk and resource acquisition must accurately predict ambient levels of predation risk to maximize fitness. We measure this trade-off explicitly in larvae of the damselfly Enallagma antennatum, comparing consumption rates in the presence of chemical cues from predators and injured prey. Damselflies distinguished among types of chemical cues based on species of prey injured or eaten. Injured coexisting heterospecific and unknown heterospecific chemical cues did not reduce foraging relative to starved predator cues, while cues arising from predators eating a coexisting heterospecific did decrease foraging. This study shows a cost in terms of reduced foraging in response to chemical cues and further defines the ability of prey to respond discerningly to chemical cues.     

Internalization and degradation of receptor bound C-reactive protein by U-937 cells: induction of H2O2 production and tumoricidal activity

The presence of a membrane receptor for C-reactive protein (CRP-R) on the human monocytic cell line U-937 was the basis for determining the metabolic fate of the receptor-bound ligand and the functional response of the cells to CRP. Internalized [125I]CRP was measured by removing cell surface-bound [125I]CRP with pronase. Warming cells to 37 degrees C resulted in the internalization of approx. 50% of the receptor-bound [125I]CRP or receptor-bound [125I]CRP-PC-KLH complexes. U-937 cells degraded about 25% of the internalized [125I]CRP into TCA-soluble radiolabeled products. The lysosomotrophic agents (chloroquine, NH4Cl) greatly decreased the extent of CRP degradation without altering binding or internalization. In addition, a pH less than 4.0 resulted in dissociation of receptor-bound [125I]CRP. Treatment of U-937 cell with monensin, a carboxylic ionophore which prevents receptor recycling, resulted in accumulation of internalized [125I]CRP. Therefore, it appears that the CRP-R complex is internalized into an endosomal compartment where the CRP is uncoupled from its receptor and subsequently degraded. CRP initiated the differentiation of the U-937 cells so that they acquired the ability to produce H2O2 and also display in vitro tumoricidal activity. The results support the concept that internalization and degradation of CRP leads to the activation of monocytes during inflammation.     

A classification of compounds in American Sign Language: an evaluation of the Bisetto and Scalise framework

Cross-linguistic comparisons of compounds are difficult because of the varied criteria and terms used by different linguists (Scalise and Bisetto 2009). To address this problem, Scalise and Bisetto proposed a universal three-level classification of compound types. Although several researchers have shown that American Sign Language (ASL) has compound signs, a classification of compound types in ASL has not been completed. All of the potential compounds in an ASL dictionary (Costello 1994) were identified, then verified as compounds with the help of a fluent deaf signer by applying standard tests for composition. These compounds were then classified using the Scalise and Bisetto classification. We found that Scalise and Bisetto??s three-level hierarchical classification successfully captured cross-category relationships among subtypes of compounds but fails to predict the existence of one type of compound attested in ASL. In our revised classification, a?consistent set of criteria is used at each level, resulting in a classification that is both conceptually simpler and empirically more adequate. The second tier category for hierarchical compounds are bifurcated into the categories expressed predicate and unexpressed predicate, according to whether each predicate in a compound??s semantic structure is expressed by one of the overt constituents. The revision has the further advantage of allowing us to avoid any reference to word class/grammatical category in applying our taxonomy, a goal that we show to be desirable on both theoretical and empirical grounds.     

Deletion of ripA alleviates suppression of the inflammasome and MAPK by Francisella tularensis

Francisella tularensis is a facultative intracellular pathogen and potential biothreat agent. Evasion of the immune response contributes to the extraordinary virulence of this organism although the mechanism is unclear. Whereas wild-type strains induced low levels of cytokines, an F. tularensis ripA deletion mutant (LVSΔripA) provoked significant release of IL-1β, IL-18, and TNF-α by resting macrophages. IL-1β and IL-18 secretion was dependent on inflammasome components pyrin-caspase recruitment domain/apoptotic speck-containing protein with a caspase recruitment domain and caspase-1, and the TLR/IL-1R signaling molecule MyD88 was required for inflammatory cytokine synthesis. Complementation of LVSΔripA with a plasmid encoding ripA restored immune evasion. Similar findings were observed in a human monocytic line. The presence of ripA nearly eliminated activation of MAPKs including ERK1/2, JNK, and p38, and pharmacologic inhibitors of these three MAPKs reduced cytokine induction by LVSΔripA. Animals infected with LVSΔripA mounted a stronger IL-1β and TNF-α response than that of mice infected with wild-type live vaccine strain. This analysis revealed novel immune evasive mechanisms of F. tularensis.     

Two silicone nontoxic fouling release coatings: Hydrosilation cured PDMS and CaCO3 filled,ethoxysiloxane cured RTV11

Two silicone coatings have been evaluated for barnacle adhesion. One coating is an unfilled hydrosilation cured polydimethylsiloxane (PDMS) network, while the other is a room temperature vulcanized (RTV), filled, ethoxysiloxane cured PDMS elastomer, RTV11^?. The adhesion strength of one species of barnacle, Balanus eburneus, to the hydrosilation coatings is in the range of 0.37–0.60 kg cm^‐2 while the corresponding range for RTV11 is 0.64–0.90 kg cm^‐2. The easier release of B. eburneus from the hydrosilation cured network compared to RTV11 is discussed in relationship to differences in bulk and surface properties. Preliminary results suggest bulk modulus may be the most important parameter in determining barnacle adhesion strength. In light or mechanical property analysis, a re‐evaluation of surface properties and chemical stability is presented.     

Visual contrast detection by a single channel versus probability summation among channels

It is now generally accepted that the human visual system consists of subsystems (channels) that may be activated in parallel. According to some models of detection, detection is by probability summation among channels, while in other models it is assumed that detection is by a single channel that may even be tuned specifically to the stimulus pattern (detection by a matched filter). So far, arguments in particular for the hypothesis of probbbility summation are based on plausibility considerations and on demonstrations that the data from certain detection experiments are compatible with this hypothesis. In this paper it is shown that linear contrast interrelationship functions together with a property of a large class of distribution functions (strict log-concavity or logconvexity on the relevant set of contrasts/intensities) uniquely point to detection by a single channel. In particular, models of detection by probability summation based on Quick's Model are incompatible with linear contrast interrelationship functions. Sufficient (and observable) conditions for the strict logconcavity/log-convexity of distribution functions are presented.