Effect of different types of conditioning contraction on upper body postactivation potentiation

Muscle contractions preceding an activity can result in increased force generation (postactivation potentiation [PAP]). Although the type of muscular contractions could affect subsequent strength and power performance, little information exists on their effects. The purpose of this study was to examine PAP effects produced by isometric (ISO), concentric (CON), eccentric (ECC), or concentric-eccentric (DYN) conditioning contractions on upper body force and power performance. Ten male, competitive rugby players (mean ± SD: age 20.4 ± 0.8 years, height 177.0 ± 8.1 cm, body mass 90.2 ± 13.8 kg) performed a ballistic bench press throw (BBPT) followed by a 10-minute rest and one of the conditioning contractions. After a 12-minute rest, the subjects performed another BBPT (post-BBPT). The conditioning contractions, applied on separate days and in counterbalanced randomized order, were a 7-second isometric barbell bench press for ISO and 1 set of 3 bench press repetitions at 3 repetition maximum for CON, ECC, and DYN (each repetition lasting 2 seconds for CON and ECC, overall execution time <7 seconds for DYN). Peak power (Ppeak), peak force (Fpeak), maximum distance (Dmax) and rate of force development (RFD) were measured using a linear position transducer. Electromyography (EMG) of the pectoralis major and triceps brachii was also recorded. The ISO produced significantly higher Ppeak (587 ± 116 and 605 ± 126 W for pre- and post-BBPT, respectively; p < 0.05). No significant differences in Ppeak were revealed for CON, ECC, and DYN (p > 0.05), and no significant differences existed in Fpeak, Dmax, and RFD for ISO, CON, ECC, and DYN (p > 0.05). Finally, EMG was not significantly different between pre- and post-BBPT for any of the conditioning contractions (p > 0.05). Isometric contractions appear to be the only conditioning contractions increasing upper body power output after long resting periods.     

Molecular markers reconstruct the invasion history of variable leaf watermilfoil (<Emphasis Type="Italic">Myriophyllum heterophyllum</Emphasis>) and distinguish it from closely related species

Genetic variation is increasingly recognized as an important factor influencing the establishment and spread of introduced species, and depends on both the introduction history and partitioning of genetic variation within and among potential source populations. We examine patterns of genetic variation in native and introduced populations of variable leaf watermilfoil, Myriophyllum heterophyllum, using chloroplast (trnL-F) and ribosomal (ITS) DNA sequences, as well as amplified fragment length polymorphisms (AFLPs). We identify a strong phylogeographic break distinguishing populations located on the Atlantic Coastal Plain (ACP) versus other (“Continental”) portions of the native range. Within these distinct biogeographic regions, we also find genetic variation to be strongly partitioned among populations as analysis of molecular variance (AMOVA) partitioned 91 and 75% of cpDNA and ITS diversity among populations, respectively. We demonstrate that the introduced ranges of variable leaf watermilfoil (northeastern and western US) result from multiple independent introductions from a variety of source populations, including lineages from both the ACP and Continental portions of the native range. In addition, we used our molecular markers to demonstrate that variable leaf watermilfoil is genetically distinct from three closely-related species that it is morphologically similar to. In particular, we demonstrate that M. heterophyllum is clearly distinct from a morphologically similar native species in the western US, M. hippuroides—whose distinctiveness from M. heterophyllum has been questioned—and therefore confirm the introduction of M. heterophyllum in the western US. Furthermore, we provide the first evidence for hybridization between these two species. Finally, our molecular markers identify previously unrecognized genetic variation in these four species, and therefore demonstrate the need for further taxonomic investigation.     

Opposing roles for membrane bound and soluble Fas ligand in glaucoma-associated retinal ganglion cell death

Glaucoma, the most frequent optic neuropathy, is a leading cause of blindness worldwide. Death of retinal ganglion cells (RGCs) occurs in all forms of glaucoma and accounts for the loss of vision, however the molecular mechanisms that cause RGC loss remain unclear. The pro-apoptotic molecule, Fas ligand, is a transmembrane protein that can be cleaved from the cell surface by metalloproteinases to release a soluble protein with antagonistic activity. Previous studies documented that constitutive ocular expression of FasL maintained immune privilege and prevented neoangeogenesis. We now show that FasL also plays a major role in retinal neurotoxicity. Importantly, in both TNFα triggered RGC death and a spontaneous model of glaucoma, gene-targeted mice that express only full-length FasL exhibit accelerated RGC death. By contrast, FasL-deficiency, or administration of soluble FasL, protected RGCs from cell death. These data identify membrane-bound FasL as a critical effector molecule and potential therapeutic target in glaucoma.     

Camptothecin-somatostatin conjugates inhibit the growth of small cell lung cancer cells

The effects of camptothecin-somatostatin (CPT-SS) conjugates were investigated on small cell lung cancer (SCLC) cells. CPT was coupled to a SS agonist (SSA), c(Cys-Phe-DTrp-Lys-Thr-Cys)Thr-NH2 using the built in nucleophile assisted-releasing group (L1) N-methyl-aminoethyl-Gly-Dser-Nle-Dtyr-Dser or (L2) aminoethyl-Gly-Dser-Nle-Dtyr-Dser. The resulting CPT-L1-SSA and CPT-L2-SSA inhibited the specific binding of [125I-Tyr11]SS to NCI-H69 cell membranes with IC50 values of 0.2 and 2.1 nM, respectively. [125I]CPT-L1-SSA was internalized by SCLC cells at 37 degrees C but not at 4 degrees C. CPT-L1-SSA and CPT-L2-SSA inhibited in a dose-dependent manner the increase in adenylylcyclase activity caused by 25 microM forskolin. In vitro, 0.3 microM CPT-L1-SSA half-maximally inhibited the clonal growth of SCLC cells and 1 microM CPT-L1-SSA strongly inhibited 3H-thymidine incorporation into DNA and trypan-blue exclusion. These results suggest that CPT conjugated peptides such as CPT-L1-SSA may prove useful for exploring the efficacy of receptor-directed cytotoxicity to inhibit the proliferation of SCLC cells.     

A computational investigation of kinetoplastid trans-splicing

Trans-splicing is an unusual process in which two separate RNA strands are spliced together to yield a mature mRNA. We present a novel computational approach which has an overall accuracy of 82% and can predict 92% of known trans-splicing sites. We have applied our method to chromosomes 1 and 3 of Leishmania major, with high-confidence predictions for 85% and 88% of annotated genes respectively. We suggest some extensions of our method to other systems.     

Using co-occurrence network structure to extract synonymous gene and protein names from MEDLINE abstracts

Background  

Text-mining can assist biomedical researchers in reducing information overload by extracting useful knowledge from large collections of text. We developed a novel text-mining method based on analyzing the network structure created by symbol co-occurrences as a way to extend the capabilities of knowledge extraction. The method was applied to the task of automatic gene and protein name synonym extraction.     

Valence and anion binding of bovine ribonuclease A between pH 6 and 8

Several studies have shown that divalent anion binding to ribonuclease A (RNase A) contributes to RNase A folding and stability. However, there are conflicting reports about whether chloride binds to or stabilizes RNase A. Two broad-zone experimental approaches, membrane-confined electrophoresis and analytical ultracentrifugation, were used to examine the electrostatic and electrohydrodynamic characteristics of aqueous solutions of bovine RNase A in the presence of 100 mM KCl and 10 mM Bis-Tris propane over a pH range of 6.00-8.00. The results of data analysis using a Debye-Huckel-Henry model, compared with expectations based on pK(A) values, are consistent with the binding of two chlorides by RNase A. The decreased protein valence resulting from anion binding contributes 2-3 kJ/mol to protein stabilization. This work demonstrates the utility of first-principle valence determinations to detect protein solution properties that might otherwise remain undetected.     

GENSTAT programs for performing Muir's alternative partitioning of genotype-by-environment interaction

Genotype-by-environment (GE) interaction exists when different cultivars or strains have different phenotypic responses to environmental variation (Merila and Fry 1998). The phenomenon is of major concern in plant breeding, as it can limit gains in selecting superior cultivars. In animal breeding, the problem is also an important issue because breeding stocks are developed by a few companies but are used worldwide (Lin and Togashi 2002).     

Enzyme-catalyzed mechanism of isoniazid activation in class I and class III peroxidases

There is an urgent need to understand the mechanism of activation of the frontline anti-tuberculosis drug isoniazid by the Mycobacterium tuberculosis catalase-peroxidase. To address this, a combination of NMR spectroscopic, biochemical, and computational methods have been used to obtain a model of the frontline anti-tuberculosis drug isoniazid bound to the active site of the class III peroxidase, horseradish peroxidase C. This information has been used in combination with the new crystal structure of the M. tuberculosis catalase-peroxidase to predict the mode of INH binding across the class I heme peroxidase family. An enzyme-catalyzed mechanism for INH activation is proposed that brings together structural, functional, and spectroscopic data from a variety of sources. Collectively, the information not only provides a molecular basis for understanding INH activation by the M. tuberculosis catalase-peroxidase but also establishes a new conceptual framework for testing hypotheses regarding the enzyme-catalyzed turnover of this compound in a number of heme peroxidases.     

Development of high affinity camptothecin-bombesin conjugates that have targeted cytotoxicity for bombesin receptor-containing tumor cells

Mammalian bombesin (BN) receptors are among those most frequently overexpressed by a number of common tumors including prostate, breast, lung, and colon cancers. The aim of this study was to develop a camptothecin-bombesin (CPT-BN) conjugate that interacts with all classes of BN receptors and possibly functions as a prodrug via a labile linker with site-specific cytotoxicity for cancer cells bearing these receptors. CPT was coupled to analogs of [D-Tyr6,beta-Ala11,Phe13,Nle14]BN-(6-14) (BA0) using carbamate linkers (L1 and L2) with built-in nucleophile-assisted releasing groups for intracellular cleavage of free cytotoxic agents. One conjugate, CPT-L2-BA3, bound to all three BN receptor classes with high affinity and functioned as a full agonist at each. 125I-CPT-L2-BA3 was rapidly internalized by cells expressing each BN receptor class and, using fluorescent imaging, was found to co-localize with BN receptors initially and later to be internalized in cytoplasmic compartments. HPLC analysis of internalized ligand showed that 40% was intact, 25% was metabolized by releasing free CPT, and 35% was metabolized to other breakdown products. CPT-L2-BA3 inhibited the growth of NCI-H1299 non-small cell lung cancer cells in 3-(4,5-dimethylthiazol-2-yl)-2.5-diphenyl-2H-tetrazolium bromide (MTT) and clonal growth assays. CPT-L2-BA3 was cytotoxic in an MTT assay for cells transfected with each class of BN receptor; however, it had significantly less effect in cells lacking BN receptors. These results indicate that CTP-L2-BA3 is a potent agonist that is cytotoxic for cells overexpressing any of the three BN receptor classes and functions as a prodrug for receptor-mediated cytoxicity. It therefore should be a useful prototype to explore the effectiveness of tumor-specific cytotoxicity delivery using a receptor-mediated mechanism.