Recovery of DNA barcodes from blackfly museum specimens (Diptera: Simuliidae) using primer sets that target a variety of sequence lengths

In this study, we evaluated the efficacy of various primers for the purpose of DNA barcoding old, pinned museum specimens of blackflies (Diptera: Simuliidae). We analysed 271 pinned specimens representing two genera and at least 36 species. Due to the age of our material, we targeted overlapping DNA fragments ranging in size from 94 to 407 bp. We were able to recover valid sequences from 215 specimens, of which 18% had 500‐ to 658‐bp barcodes, 36% had 201‐ to 499‐bp barcodes and 46% had 65‐ to 200‐bp barcodes. Our study demonstrates the importance of choosing suitable primers when dealing with older specimens and shows that even very short sequences can be diagnostically informative provided that an appropriate gene region is used. Our study also highlights the lack of knowledge surrounding blackfly taxonomy, and we briefly discuss the need for further phylogenetic studies in this socioeconomically important family of insects.     

Self-association of coilin reveals a common theme in nuclear body localization

We have found that coilin, the marker protein for Cajal bodies (coiled bodies, CBs), is a self-interacting protein, and we have mapped the domain responsible for this activity to the amino-terminus. Together with a nuclear localization signal, the self-interaction domain is necessary and sufficient for localization to CBs. Overexpression of various wild-type and mutant coilin constructs in HeLa cells results in disruption of both CBs and survival motor neurons (SMN) gems. Additionally, we have identified a cryptic nucleolar localization signal (NoLS), within the coilin protein, which may be exposed in specific coilin phospho-isoforms. The implications of these findings are discussed in light of the fact that other proteins known to localize within nuclear bodies (e. g., PML, SMN and Sam68) can also self-associate. Thus protein self-interaction appears to be a general feature of nuclear body marker proteins.     

Stable baselines of temporal turnover underlie high beta diversity in tropical arthropod communities

While the high species diversity of tropical arthropod communities has often been linked to marked spatial heterogeneity, their temporal dynamics have received little attention. This study addresses this gap by examining spatio‐temporal variation in the arthropod communities of a tropical montane forest in Honduras. By employing DNA barcode analysis and Malaise trap sampling across 4 years and five sites, 51,596 specimens were assigned to 8,193 presumptive species. High beta diversity was linked more strongly to elevation than geographic distance, decreasing by 12% when only the dominant species were considered. When sampling effort was increased by deploying more traps at a site, beta diversity only decreased by 2%, but extending sampling across years decreased beta diversity by 27%. Species inconsistently detected among years, likely transients from other settings, drove the low similarity in species composition among traps only a few metres apart. The dominant, temporally persistent species substantially influenced the cyclic pattern of change in community composition among years. This pattern likely results from divergence–convergence dynamics, suggesting a stable baseline of temporal turnover in each community. The overall results establish that large sample sizes are necessary to reveal species richness, but are not essential for quantifying beta diversity. This study further highlights the need for standardized methods of sampling and species identification to generate the comparative data required to evaluate biodiversity change in space and time.     

Maximal eccentric and concentric strength discrepancies between young men and women for dynamic resistance exercise

Although research has demonstrated that isokinetic eccentric (ECC) strength is 20-60% greater than isokinetic concentric (CON) strength, few data exist comparing these strength differences in standard dynamic resistance exercises. The purpose of the study was to determine the difference in maximal dynamic ECC and CON strength for 6 different resistance exercises in young men and women. Ten healthy young men (mean +/- SE, 25.30 +/- 1.34 years), and 10 healthy young women (mean +/- SE, 23.40 +/- 1.37 years) who were regular exercisers with resistance training experience participated in the study. Two sessions were performed to determine CON and ECC 1 repetitions maximum for latissimus pull-down (LTP), leg press (LP), bench press (BP), leg extension (LE), seated military press (MP), and leg curl (LC) exercises. Maximal ECC and maximal CON strength were determined on weight stack machines modified to isolate ECC and CON contractions using steel bars and pulleys such that only 1 type of contraction was performed. Within 2 weeks, participants returned and completed a retest trial in a counterbalanced fashioned. Test-retest reliability was excellent (r = 0.99) for all resistance exercise trials. Men demonstrated 20-60% greater ECC than CON strength (LTP = 32%, LP = 44%, BP = 40%, LE = 35%, MP = 49%, LC = 27%). Women's strength exceeded the proposed parameters for greater ECC strength in 4 exercises, p < 0.05 (LP = 66%, BP = 146%, MP = 161%, LC = 82%). The ECC/CON assessment could help coaches capitalize on muscle strength differences in young men and women during training to aid in program design and injury prevention and to enhance strength development.     

Fixation de l'acide phosphorique sur le calcaire des sols

Conclusion Les expériences ci-dessus nous montrent que le P₂O₅ des solutions du sol à faible concentration se fixent sur les grains calcaire de la terre arable non par précipitation, mais par un phénomène d'adsorption.L'acide phosphorique ainsi fixé peut repasser en solution par le phénomène inverse de désorption pour être mis a la disposition des plantes lorsque le titre de la solution du sol en P₂O₅ s'appauvrit.Lorsqu'on ajoute au sol des engrais phosphates, la concentration en P₂O₅ autour des grains d'engrais peut ëtre suffisamment élevée pour qu'il y ait précipitation de phosphate gélatineux autour des granules d'engrais.Mais ces précipités se redissolvent au moins partiellement dans les solutions du sol et se fixent sur les grains calcaire suivant le processus que nous venons d'indiquer.     

Roles of double-strand breaks, nicks, and gaps in stimulating deletions of CTG.CAG repeats by intramolecular DNA repair

A series of plasmids harboring CTG.CAG repeats with double-strand breaks (DSB), single-strand nicks, or single-strand gaps (15 or 30 nucleotides) within the repeat regions were used to determine their capacity to induce genetic instabilities. These plasmids were introduced into Escherichia coli in the presence of a second plasmid containing a sequence that could support homologous recombination repair between the two plasmids. The transfer of a point mutation from the second to the first plasmid was used to monitor homologous recombination (gene conversion). Only DSBs increased the overall genetic instability. This instability took place by intramolecular repair, which was not dependent on RuvA. Double-strand break-induced instabilities were partially stabilized by a mutation in recF. Gaps of 30 nt formed a distinct 30 nt deletion product, whereas single strand nicks and gaps of 15 nt did not induce expansions or deletions. Formation of this deletion product required the CTG.CAG repeats to be present in the single-stranded region and was stimulated by E.coli DNA ligase, but was not dependent upon the RecFOR pathway. Models are presented to explain the intramolecular repair-induced instabilities and the formation of the 30 nt deletion product.     

Functional properties of the apical Na+-K+-2Cl- cotransporter isoforms.

The bumetanide-sensitive Na(+):K(+):2Cl(-) cotransporter (BSC1) is the major pathway for salt reabsorption in the apical membrane of the mammalian thick ascending limb of Henle. Three isoforms of the cotransporter, known as A, B, and F, exhibit axial expression along the thick ascending limb. We report here a functional comparison of the three isoforms from mouse kidney. When expressed in Xenopus oocytes the mBSC1-A isoform showed higher capacity of transport, with no difference in the amount of surface expression. Kinetic characterization revealed divergent affinities for the three cotransported ions. The observed EC(50) values for Na(+), K(+), and Cl(-) were 5.0 +/- 3.9, 0.96 +/- 0.16, and 22.2 +/- 4.8 mm for mBSC1-A; 3.0 +/- 0.6, 0.76 +/- 0.07, and 11.6 +/- 0.7 mm for mBSC1-B; and 20.6 +/- 7.2, 1.54 +/- 0.16, and 29.2 +/- 2.1 mm for mBSC1-F, respectively. Bumetanide sensitivity was higher in mBSC1-B compared with the mBSC1-A and mBSC1-F isoforms. All three transporters were partially inhibited by hypotonicity but to different extents. The cell swelling-induced inhibition profile was mBSC1-F > mBSC1-B > mBSC1-A. The function of the Na(+):K(+):2Cl(-) cotransporter was not affected by extracellular pH or by the addition of metolazone, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), or R(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1-H-indenyl-5-yl)-oxy]acetic acid (DIOA) to the extracellular medium. In contrast, exposure of oocytes to HgCl(2) before the uptake period reduced the activity of the cotransporter. The effect of HgCl(2) was dose-dependent, and mBSC1-A and mBSC1-B exhibited higher affinity than mBSC1-F. Overall, the functional comparison of the murine apical renal-specific Na(+):K(+):2Cl(-) cotransporter isoforms A, B, and F reveals important functional, pharmacological, and kinetic differences, with both physiological and structural implications.