Hydrogen bond supramolecular self-assembly in nickel(II) dithiophosphates, Ni[S2P(OR)2]2, R = sec-Bu, iso-Bu, and their bis(pyrazole) adducts

The reaction between nickel(II) nitrate and potassium phosphorus-1,1-dithiolates (di-sec-butyl and di-iso-butyl) in methanol yields 2:1 complexes which were characterized by FT-IR and NMR spectroscopy. 2:1 pyrazole adducts of both compounds were also obtained.The X-ray diffraction analysis of the compounds reveals square planar, four-coordination geometry for the homoleptic compounds and a six-coordinated distorted octahedral geometry for the adducts. In Ni[S₂P(OBu^s)₂]₂ the molecules are associated through C-H?O hydrogen bonds (2.652 Å), and in Ni[S₂P(OBuⁱ)₂]₂ the molecules are associated through C-H?S hydrogen bonds (2.948 Å). The pyrazole adducts are associated through N-H?O bonds and N-H?S bonds from the pyrazole nitrogen atoms, to form supramolecular assemblies. Thus, Ni[S₂P(OBu^s)₂(Pz)₂]₂ (Pz = pyrazole) forms bi-dimensional layers through N-H?O and N-H?S bonds (2.502 and 2.965 Å, respectively), whereas Ni[S₂P(OBuⁱ)₂(Pz)₂]₂ forms linear chains with N-H?S bonds 2.728 Å. The dithiophosphato groups behave as isobidentate chelating ligands.     

Inhibition of messenger RNA synthesis by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole without its detectable accumulation in mouse T-lymphoma cells

Two lines of evidence were obtained which indicate that inhibition of mRNA formation does not require the detectable accumulation of 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB), a halogenated analog of adenosine. First, the extent of inhibition by DRB of the formation of cytoplasmic poly(A)⁺ RNA was as rapid and severe (>90% inhibition) in wild-type mouse lymphoma cells (S49) as in mutant cells (AE₁), derived from S49, which were deficient in the transport of purine and pyrimidine nucleosides. Second, the accumulation of [³H]DRB was measured directly and compared to the accumulation of [³H]adenosine. Whereas S49 cells accumulated [³H]adenosine in a linear manner, neither S49 nor AE₁ cells accumulated [³H]DRB to a significant extent. This suggests that inhibition of mRNA synthesis by DRB may (1) require the transport and intracellular accumulation of only minute amounts of DRB, or (2) result from secondary event(s) triggered by interaction of DRB with a surface membrane component.     

Opposing organizing forces of deposit-feeding marine communities

We contend that a range of phenomena characterizing temperate deposit-feeding communities in low-energy environments is strongly organized by two principal opposing forces: (1) spatially localized inputs of detritus or new recruits, leading to a mosaic of initial patches, with subsequent impacts on spatio-temporal variation of species with limited mobility; and (2) the impact of mobile consumers, which move to spatially localized resources and thereby exert major controls over comparatively larger spatial scales. Surface deposit feeders react differently from deep feeders, in terms of spatio-temporal population change. The two opposing community control forces, combined with responses of deposit feeder functional groups, have potentially different effects on community structure. Mobile consumers, often acting as keystone species, may move to localized patches created by the bottom-up force of food input or by localized recruitment of prey. Their mobility, combined with predicted optimal foraging behavior, would usually produce a spatially homogenizing force, leading to reduced spatial variation in community composition. By contrast, spatially localized inputs of resources, if dominant, would always lead to strong spatial heterogeneity. Dominance of complex space–time variation in detrital enrichment would lead to strong spatio-temporal complexity in macrofauna if the response of recruiting larvae and rapidly growing small invertebrate populations was immediate and keyed to localized food input. The ability of mobile consumers to locate detritus, combined with the spatial distribution and overall input rate of detritus, should determine the balance of surface and deep-feeding deposit feeders. The opposing force approach can be applied to communities generally.     

Nasopharyngeal carcinoma-associated Epstein-Barr virus-encoded oncogene latent membrane protein 1 potentiates regulatory T-cell function

Sequence variation in the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) oncogene structure may affect antigen-presenting cell (APC) function of infected B cells and immune escape by EBV-specific T cells and thus contribute to the development of malignancy. Normal B cell-associated LMP1 (B-LMP1) upregulates B cell APC function through activation of the necrosis factor (NF)-kappaB subunit, RelB. We examined the ability of B-LMP1 and a nasopharyngeal carcinoma-associated LMP1 (NPC-LMP1) to modulate B cell APC function and T-cell responses. B lymphoma cells transfected with NPC-LMP1 stimulated resting T cells in mixed lymphocyte reaction less efficiently than B-LMP1 transfectants. Unexpectedly, antigen presentation to CD4(+) T helper cells was reduced owing to potentiation of regulatory T-cell function by NPC-LMP1 transfectants, which produce increased levels of interleukin-10, rendering CD4(+) T cells hyporesponsive. Thus, after primary EBV infection, T cells may escape activation by NPC-LMP1. These observations have important implications for the establishment of EBV-associated malignancy in the context of infection with tumour-associated EBV LMP1 variants.     

Description and Bionomics of Mesomermis camdenensis n. sp. (Mermithidae), a Parasite of Black Flies (Simuliidae)

Mesomermis camdenensis n. sp. is described from larvae of Simulium tuberosum (lundstroem) collected in Camden Valley Creek, Washington County, New York. This species possesses a barrel-shaped vagina, vulval flap. two short separate spicules, terminal mouth, six longitudinal chords, six cephalic papillae, large sexually dimorpbic anaphids, an esophagns of uniform width which extends for less than one-third of the body length, and a cone-shaped tail directed ventrally without appendage. Juveniles also are described and illustrated.A detailed morphological comparison with the mermithid M. flumenalis Welch is presented. The most pronounced morphological differences between these species are in the shape of the vulva, juvenile tail, and infective stage. Cross-mating trials support the integrity of the new species.The life cycle of M. camdenensis is closely synchronized with that of its primary host, S. tuberosum larvae. Infected S. tuberosum larvae were first collected in May. Emergence of postparasites from late instars took place from mid-June through mid-October. Sampling data indicate a lower susceptibility to infection among S. venuslum Say larvae.     

Effects of a Seven Day Overload-Period of High-Intensity Training on Performance and Physiology of Competitive Cyclists

Objectives

Competitive endurance athletes commonly undertake periods of overload training in the weeks prior to major competitions. This investigation examined the effects of two seven-day high-intensity overload training regimes (HIT) on performance and physiological characteristics of competitive cyclists.

Design

The study was a matched groups, controlled trial.

Methods

Twenty-eight male cyclists (mean ± SD, Age: 33±10 years, Mass 74±7 kg, VO₂ peak 4.7±0.5 L·min⁻¹) were assigned to a control group or one of two training groups for seven consecutive days of HIT. Before and after training cyclists completed an ergometer based incremental exercise test and a 20-km time-trial. The HIT sessions were ∼120 minutes in duration and consisted of matched volumes of 5, 10 and 20 second (short) or 15, 30 and 45 second (long) maximal intensity efforts.

Results

Both the short and long HIT regimes led to significant (p<0.05) gains in time trial performance compared to the control group. Relative to the control group, the mean changes (±90% confidence limits) in time-trial power were 8.2%±3.8% and 10.4%±4.3% for the short and long HIT regimes respectively; corresponding increases in peak power in the incremental test were 5.5%±2.7% and 9.5%±2.5%. Both HIT (short vs long) interventions led to non-significant (p>0.05) increases (mean ± SD) in VO₂ peak (2.3%±4.7% vs 3.5%±6.2%), lactate threshold power (3.6%±3.5% vs 2.9%±5.3%) and gross efficiency (3.2%±2.4% vs 5.1%±3.9%) with only small differences between HIT regimes.

Conclusions

Seven days of overload HIT induces substantial enhancements in time-trial performance despite non-significant increases in physiological measures with competitive cyclists.     

Activation of human furin precursor processing endoprotease occurs by an intramolecular autoproteolytic cleavage.

Human furin is a calcium-dependent serine endoprotease that can efficiently cleave many precursor proteins on the carboxyl side of the consensus cleavage sequence, -Arg-X-Lys/Arg-Arg-, both in vivo and in vitro. Analysis of furin proteins in extracts of cells infected with a vaccinia recombinant expressing human furin show that the enzyme is present as two prominent forms of 90 and 96 kDa. Because the structurally related bacterial subtilisins require endoproteolytic removal of the NH2-terminal pro-region by an autocatalytic intramolecular cleavage, we speculated that the size heterogeneity in the furin doublet similarly may result from a proteolytic removal of an NH2-terminal pro-region. Here we report identification of the 90-kDa furin NH2 terminus and, based on the reported sequence of the furin cDNA, demonstrate that this furin protein is derived from a larger precursor by an endoproteolytic cleavage on the COOH-terminal side of a consensus furin cleavage site, -Arg-Thr-Lys-Arg107-. Expression of mutant furin molecules containing an altered cleavage site (Arg104----Ala or Arg107----Gly) resulted in the production of only the 96-kDa furin protein. Assays of furin-dependent cleavage of a protein substrate in vitro showed that proteolytic activity was associated with the 90-kDa and not the 96-kDa furin protein, demonstrating that removal of the NH2-terminal pro-region is required for furin activity. Expression of a third furin construct containing a mutation of the active site aspartate (Asp153----Asn) similarly resulted in the expression of only the 96-kDa protein, suggesting that furin activation occurs by an autoproteolytic cleavage. Finally, the production of 90-kDa furin from either site-directed furin mutant could not be potentiated by overexpressing active furin, suggesting that the autoproteolytic activation was an intramolecular event.     

Trees tolerate an extreme heatwave via sustained transpirational cooling and increased leaf thermal tolerance

Heatwaves are likely to increase in frequency and intensity with climate change, which may impair tree function and forest C uptake. However, we have little information regarding the impact of extreme heatwaves on the physiological performance of large trees in the field. Here, we grew Eucalyptus parramattensis trees for 1 year with experimental warming (+3°C) in a field setting, until they were greater than 6 m tall. We withheld irrigation for 1 month to dry the surface soils and then implemented an extreme heatwave treatment of 4 consecutive days with air temperatures exceeding 43°C, while monitoring whole‐canopy exchange of CO₂ and H₂O, leaf temperatures, leaf thermal tolerance, and leaf and branch hydraulic status. The heatwave reduced midday canopy photosynthesis to near zero but transpiration persisted, maintaining canopy cooling. A standard photosynthetic model was unable to capture the observed decoupling between photosynthesis and transpiration at high temperatures, suggesting that climate models may underestimate a moderating feedback of vegetation on heatwave intensity. The heatwave also triggered a rapid increase in leaf thermal tolerance, such that leaf temperatures observed during the heatwave were maintained within the thermal limits of leaf function. All responses were equivalent for trees with a prior history of ambient and warmed (+3°C) temperatures, indicating that climate warming conferred no added tolerance of heatwaves expected in the future. This coordinated physiological response utilizing latent cooling and adjustment of thermal thresholds has implications for tree tolerance of future climate extremes as well as model predictions of future heatwave intensity at landscape and global scales.     

Lipopolysaccharide biosynthesis genes discriminate between Rubus- and Spiraeoideae-infective genotypes of Erwinia amylovora

Comparative genomic analysis revealed differences in the lipopolysaccharide (LPS) biosynthesis gene cluster between the Rubus‐infecting strain ATCC BAA‐2158 and the Spiraeoideae‐infecting strain CFBP 1430 of Erwinia amylovora. These differences corroborate rpoB‐based phylogenetic clustering of E. amylovora into four different groups and enable the discrimination of Spiraeoideae‐ and Rubus‐infecting strains. The structure of the differences between the two groups supports the hypothesis that adaptation to Rubus spp. took place after species separation of E. amylovora and E. pyrifoliae that contrasts with a recently proposed scenario, based on CRISPR data, in which the shift to domesticated apple would have caused an evolutionary bottleneck in the Spiraeoideae‐infecting strains of E. amylovora which would be a much earlier event. In the core region of the LPS biosynthetic gene cluster, Spiraeoideae‐infecting strains encode three glycosyltransferases and an LPS ligase (Spiraeoideae‐type waaL), whereas Rubus‐infecting strains encode two glycosyltransferases and a different LPS ligase (Rubus‐type waaL). These coding domains share little to no homology at the amino acid level between Rubus‐ and Spiraeoideae‐infecting strains, and this genotypic difference was confirmed by polymerase chain reaction analysis of the associated DNA region in 31 Rubus‐ and Spiraeoideae‐infecting strains. The LPS biosynthesis gene cluster may thus be used as a molecular marker to distinguish between Rubus‐ and Spiraeoideae‐infecting strains of E. amylovora using primers designed in this study.     

The histone variant macroH2A1.1 is recruited to DSBs through a mechanism involving PARP1

The repair of DNA double-strand breaks (DSBs) requires remodeling of the local chromatin architecture to allow the repair machinery to access sites of damage. Here, we report that the histone variant macroH2A1.1 is recruited to DSBs. Cells lacking macroH2A1 have defective recruitment of 53BP1, defective activation of chk2 kinase and increased radiosensitivity. Importantly, macroH2A1.1 is not incorporated into nucleosomes at DSBs, but instead associates with the chromatin through a mechanism which requires PARP1 activity. These results reveal an unusual mechanism involving a direct association of macroH2A1.1 with PARylated chromatin which is critical for retaining 53BP1 at sites of damage.