Effects of <Emphasis Type="Italic">Bythotrephes longimanus</Emphasis> (Crustacea,Cladocera) on the abundance,morphology, and prey community of <Emphasis Type="Italic">Leptodora kindtii</Emphasis> (Crustacea,Cladocera)

We hypothesized that native Leptodora kindtii would be shorter and have smaller feeding baskets in central Ontario lakes with greater abundances of small-bodied zooplankton prey, and that differences in zooplankton size among lakes could be attributed to the invasive cladoceran Bythotrephes longimanus. We evaluated these conjectures by comparing size metrics of Leptodora and the size of their preferred cladoceran prey in lakes invaded or not by Bythotrephes. Leptodora was less abundant in invaded lakes, but were smaller bodied with smaller feeding baskets only in lakes with long invasion histories. Small cladoceran abundance was greater in non-invaded lakes and was directly related to Leptodora abundance although not to Leptodora size. Mean Leptodora body size declined with increasing abundance of Bythotrephes. We evaluated three possible explanations for these patterns in Leptodora—(a) competition with Bythotrephes for zooplankton prey, (b) direct predation by Bythotrephes, and (c) size-selective predation by fish. While we were unable to unequivocally distinguish among these hypotheses, our observations are most consistent with predation by Bythotrephes changing zooplankton community composition and size structure in a manner that is detrimental to Leptodora. Our results indicate that Bythotrephes invasion may trigger more complex and subtle changes in food webs than previously thought.     

HIV/simian immunodeficiency virus (SIV) accessory virulence factor Vpx loads the host cell restriction factor SAMHD1 onto the E3 ubiquitin ligase complex CRL4DCAF1

The sterile alpha motif and HD domain-containing protein-1 (SAMHD1) inhibits infection of myeloid cells by human and related primate immunodeficiency viruses (HIV and SIV). This potent inhibition is counteracted by the Vpx accessory virulence factor of HIV-2/SIVsm viruses, which targets SAMHD1 for proteasome-dependent degradation, by reprogramming cellular CRL4(DCAF1) E3 ubiquitin ligase. However, the precise mechanism of Vpx-dependent recruitment of human SAMHD1 onto the ligase, and the molecular interfaces on the respective molecules have not been defined. Here, we show that human SAMHD1 is recruited to the CRL4(DCAF1-Vpx) E3 ubiquitin ligase complex by interacting with the DCAF1 substrate receptor subunit in a Vpx-dependent manner. No stable association is detectable with DCAF1 alone. The SAMHD1 determinant for the interaction is a short peptide located distal to the SAMHD1 catalytic domain and requires the presence of Vpx for stable engagement. This peptide is sufficient to confer Vpx-dependent recruitment to CRL4(DCAF1) and ubiquitination when fused to heterologous proteins. The precise amino acid sequence of the peptide diverges among SAMHD1 proteins from different vertebrate species, explaining selective down-regulation of human SAMHD1 levels by Vpx. Critical amino acid residues of SAMHD1 and Vpx involved in the DCAF1-Vpx-SAMDH1 interaction were identified by mutagenesis. Our findings show that the N terminus of Vpx, bound to DCAF1, recruits SAMHD1 via its C terminus to CRL4, in a species-specific manner for proteasomal degradation.     

Effects of red bull energy drink on repeated sprint performance in women athletes

Energy drinks are frequently consumed by athletes prior to competition to improve performance. This study examined the effect of Red Bull™ on repeated sprint performance in women athletes. Fifteen collegiate soccer players participated, with mean age, height, and body mass equal to 19.5 ± 1.1 year, 168.4 ± 5.8 cm, and 63.4 ± 6.1 kg, respectively. After performing a familiarization trial, subjects performed three sets of eight bouts of the modified t test after ingestion of 255 mL of placebo or Red Bull 1 h pre-exercise in a randomized, placebo-controlled crossover design. Throughout testing, sprint time, heart rate (HR), and rating of perceived exertion (RPE) were continuously obtained. Repeated measures analysis of variance was used to examine differences in variables between drink conditions. Across athletes, t test time ranged from 10.4 to 12.7 s. Mean sprint time was similar (p > 0.05) between Red Bull (11.31 ± 0.61 s) and placebo (11.35 ± 0.61 s). HR and RPE increased (p < 0.05) during the bouts, but there was no effect (p > 0.05) of Red Bull on either variable versus placebo. Findings indicate that 255 mL of Red Bull containing 1.3 mg/kg of caffeine and 1 g of taurine does not alter repeated sprint performance, RPE, or HR in women athletes versus placebo. One serving of this energy drink provides no ergogenic benefit for women athletes engaging in sprint-based exercise.     

Effect of garlic powder on the growth of commensal bacteria from the gastrointestinal tract

Garlic (Allium sativum) is considered one of the best disease-preventive foods. We evaluated in vitro the effect of a commercial garlic powder (GP), at concentrations of 0.1% and 1% (w/v), upon the viability of representative gut bacteria. In pure culture studies, Lactobacillus casei DSMZ 20011 was essentially found to be resistant to GP whereas a rapid killing effect of between 1 and 3 log CFU/ml reduction in cell numbers was observed with Bacteroides ovatus, Bifidobacterium longum DSMZ 20090 and Clostridium nexile A2-232. After 6h incubation, bacterial numbers increased steadily and once the strains became resistant they retained their resistant phenotype upon sub-culturing. A colonic model was also used to evaluate the effect of GP on a mixed bacterial population representing the microbiota of the distal colon. Lactic acid bacteria were found to be more resistant to GP compared to the clostridial members of the gut microbiota. While for most bacteria the antimicrobial effect was transient, the lactobacilli showed a degree of resistance to garlic, indicating that its consumption may favour the growth of these beneficial bacterial species in the gut. Garlic intake has the potential to temporarily modulate the gut microbiota.     

Thyroid function in pregnancy

Iodine is required for the production of thyroid hormones. Normal thyroid function during pregnancy is important for both the mother and developing fetus. This review discusses the changes in thyroid physiology that occur during pregnancy, the significance of thyroid function tests and thyroid antibody titers assessed during pregnancy, and the potential obstetric complications associated with maternal hypothyroidism.     

Inhibition of hepatitis C virus NS5A by fluoro-olefin based γ-turn mimetics

The HCV non-structural protein NS5A has been established as a viable target for the development of direct acting antiviral therapy. From computational modeling studies strong intra-molecular hydrogen bonds were found to be a common structural moiety within known NS5A inhibitors that have low pico-molar replicon potency. Efforts to reproduce these γ-turn-like substructures provided a novel NS5A inhibitor based on a fluoro-olefin isostere. This fluoro-olefin containing inhibitor exhibited picomolar activity (EC(50)=79 pM) against HCV genotype 1b replicon without measurable cytotoxicity. This level of activity is comparable to the natural peptide-based inhibitors currently under clinic evaluation, and demonstrates that a peptidomimetic approach can serve as a useful strategy to produce potent and structurally unique inhibitors of HCV NS5A.     

Synthesis and biological activity of 2-aminothiazoles as novel inhibitors of PGE2 production in cells

This Letter presents the synthesis and biological evaluation of a collection of 2-aminothiazoles as a novel class of compounds with the capability to reduce the production of PGE(2) in HCA-7 human adenocarcinoma cells. A total of 36 analogs were synthesized and assayed for PGE(2) reduction, and those with potent cellular activity were counter screened for inhibitory activity against COX-2 in a cell free assay. In general, analogs bearing a 4-phenoxyphenyl substituent in the R(2) position were highly active in cells while maintaining negligible COX-2 inhibition. Specifically, compound 5l (R(1)=Me, R(2)=4-OPh-Ph, R(3)=CH(OH)Me) exhibited the most potent cellular PGE(2) reducing activity of the entire series (EC(50)=90 nM) with an IC(50) value for COX-2 inhibition of >5 μM in vitro. Furthermore, the anti-tumor activity of analog 1a was analyzed in xenograft mouse models exhibiting promising anti-cancer activity.     

Reassessing the folding of the KIX domain: Evidence for a two‐state mechanism

The debate about the presence and role of intermediates in the folding of proteins has been a critical issue, especially for fast folders. One of the classical methodologies to identify such metastable species is the “burst-phase analysis,” whereby the observed signal amplitude from stopped-flow traces is determined as a function of denaturant concentration. However, a complication may arise when folding is sufficiently fast to jeopardize the reliability of the stopped-flow technique. In this study, we reassessed the folding of the KIX domain from cAMP Response Element-Binding (CREB)-binding protein, which has been proposed to involve the formation of an intermediate that accumulates in the dead time of the stopped flow. By using an in-house-built capillary continuous flow with a 50-μs dead time, we demonstrate that this intermediate is not present; the problem arose because of the instrumental limitation of the standard stopped flow to assess very fast refolding rate constants (e.g., ≥500 s⁻¹).     

Lithium treatment of APPSwDI/NOS2-/- mice leads to reduced hyperphosphorylated tau, increased amyloid deposition and altered inflammatory phenotype

Lithium is an anti-psychotic that has been shown to prevent the hyperphosphorylation of tau protein through the inhibition of glycogen-synthase kinase 3-beta (GSK3β). We recently developed a mouse model that progresses from amyloid pathology to tau pathology and neurodegeneration due to the genetic deletion of NOS2 in an APP transgenic mouse; the APPSwDI/NOS2-/- mouse. Because this mouse develops tau pathology, amyloid pathology and neuronal loss we were interested in the effect anti-tau therapy would have on amyloid pathology, learning and memory. We administered lithium in the diets of APPSwDI/NOS2-/- mice for a period of eight months, followed by water maze testing at 12 months of age, immediately prior to sacrifice. We found that lithium significantly lowered hyperphosphorylated tau levels as measured by Western blot and immunocytochemistry. However, we found no apparent neuroprotection, no effect on spatial memory deficits and an increase in histological amyloid deposition. Aβ levels measured biochemically were unaltered. We also found that lithium significantly altered the neuroinflammatory phenotype of the brain, resulting in enhanced alternative inflammatory response while concurrently lowering the classical inflammatory response. Our data suggest that lithium may be beneficial for the treatment of tauopathies but may not be beneficial for the treatment of Alzheimer's disease.