A new route for chitosan immobilization onto polyethylene surface

Low-density polyethylene (LDPE) belongs to commodity polymer materials applied in biomedical applications due to its favorable mechanical and chemical properties. The main disadvantage of LDPE in biomedical applications is low resistance to bacterial infections. An antibacterial modification of LDPE appears to be a solution to this problem. In this paper, the chitosan and chitosan/pectin multilayer was immobilized via polyacrylic acid (PAA) brushes grafted on the LDPE surface. The grafting was initiated by a low-temperature plasma treatment of the LDPE surface. Surface and adhesive properties of the samples prepared were investigated by surface analysis techniques. An antibacterial effect was confirmed by inhibition zone measurements of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The chitosan treatment of LDPE led to the highest and most clear inhibition zones (35mm(2) for E. coli and 275mm(2) for S. aureus).     

Light induced transmembrane proton gradient in artificial lipid vesicles reconstituted with photosynthetic reaction centers

Photosynthetic reaction center (RC) is the minimal nanoscopic photoconverter in the photosynthetic membrane that catalyzes the conversion of solar light to energy readily usable for the metabolism of the living organisms. After electronic excitation the energy of light is converted into chemical potential by the generation of a charge separated state accompanied by intraprotein and ultimately transmembrane proton movements. We designed a system which fulfills the minimum structural and functional requirements to investigate the physico/chemical conditions of the processes: RCs were reconstituted in closed lipid vesicles made of selected lipids entrapping a pH sensitive indicator, and electron donors (cytochrome c? and K?[Fe(CN)?]) and acceptors (decylubiquinone) were added to sustain the photocycle. Thanks to the low proton permeability of our preparations, we could show the formation of a transmembrane proton gradient under illumination and low buffering conditions directly by measuring proton-related signals simultaneously inside and outside the vesicles. The effect of selected ionophores such as gramicidin, nigericin and valinomycin was used to gain more information on the transmembrane proton gradient driven by the RC photochemistry.     

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.     

The immunoregulatory role of CD4⁺ FoxP3⁺ CD25⁻ regulatory T cells in lungs of mice infected with Bordetella pertussis

The identification of regulatory T (Treg) cells was originally based on CD25 expression; however, CD25 is also expressed by activated effector T cells. FoxP3 is a more definitive marker of Treg cells, and CD4(+) FoxP3(+) CD25(+) T cells are considered the dominant natural Treg (nTreg) population. It has been suggested that certain CD4(+) FoxP3(+) Treg cells do not express CD25. In this study, we used a murine model of respiratory infection with Bordetella pertussis to examine the role of Treg cells in protective immunity in the lung. We first demonstrated that CD4(+) FoxP3(+) CD25(-) cells are the dominant Treg population in the lung, gut and liver. Pre-activated lung CD4(+) FoxP3(+) CD25(-) cells suppressed CD4(+) effector T cells in vitro, which was partly mediated by IL-10 and not dependent on cell contact. Furthermore, CD4(+) FoxP3(+) CD25(-) IL-10(+) T cells were found in the lungs of mice at the peak of infection with B. pertussis. The rate of bacterial clearance was not affected by depletion of CD25(+) cells or in IL-10-deficient (IL-10(-/-) ) mice, but was compromised in CD25-depleted IL-10(-/-) mice. Our findings suggest that IL-10-producing CD4(+) FoxP3(+) CD25(-) T cells represent an important regulatory cell in the lung.     

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.     

Olfactory response of Typhlodromus pyri (Acari: Phytoseiidae) to synthetic methyl salicylate in laboratory bioassays

The herbivore‐induced plant volatile (HIPV) methyl salicylate (MeSA) is widely present in the chemical profile of several plant species and is known to attract natural enemies, including predatory mites. In this study, the response of Typhlodromus pyri, a key predator of pest mites in west coast vineyards, to synthetically produced MeSA was tested using a Y‐tube olfactometer in laboratory bioassays. Six doses ranging from 0.002 to 200 μg of MeSA diluted in 0.1 ml hexane were tested. Significantly higher proportions of T. pyri preferred MeSA at doses 0.02, 0.2 and 20 μg. No differences in response to MeSA were detected at the highest (200 μg), intermediate (2 μg) and lowest (0.002 μg) doses. Mite response to MeSA was a function of dose when fitting polynomial and logistic regression models using dose and square of the log dose prediction factors. Results indicate that synthetic MeSA may be applied to attract predatory arthropod populations in vineyards to enhance biological control of pest mites.     

Rapid and dissimilar response of ammonia oxidizing archaea and bacteria to nitrogen and water amendment in two temperate forest soils

Biochemical processes relevant to soil nitrogen (N) cycling are performed by soil microorganisms affiliated with diverse phylogenetic groups. For example, the oxidation of ammonia, representing the first step of nitrification, can be performed by ammonia oxidizing bacteria (AOB) and, as recently reported, also by ammonia oxidizing archaea (AOA). However, the contribution to ammonia oxidation of the phylogenetically separated AOA versus AOB and their respective responsiveness to environmental factors are still poorly understood. The present study aims at comparing the capacity of AOA and AOB to momentarily respond to N input and increased soil moisture in two contrasting forest soils. Soils from the pristine Rothwald forest and the managed Schottenwald forest were amended with either NH(4)(+)-N or NO(3)(-)-N and were incubated at 40% and 70% water-filled pore space (WFPS) for four days. Nitrification rates were measured and AOA and AOB abundance and community composition were determined via quantitative PCR (qPCR) and terminal restriction length fragment polymorphism (T-RFLP) analysis of bacterial and archaeal amoA genes. Our study reports rapid and distinct changes in AOA and AOB abundances in the two forest soils in response to N input and increased soil moisture but no significant effects on net nitrification rates. Functional microbial communities differed significantly in the two soils and responded specifically to the treatments during the short-term incubation. In the Rothwald soil the abundance and community composition of AOA were affected by the water content, whereas AOB communities responded to N amendment. In the Schottenwald soil, by contrast, AOA responded to N addition. These results suggest that AOA and AOB may be selectively influenced by soil and management factors.     

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.