Inhibition of Virulence Factors of <Emphasis Type="Italic">Candida</Emphasis> spp. by Different Surfactants

Candida yeasts are opportunistic pathogens responsible for infections in immunocompromised individuals. Among the virulence factors present in these yeasts we can mention the ability to adhere to host cells, exoenzyme production and germ tube formation. Several compounds, such as antifungal agents, plants extracts, protein inhibitors and surfactants, have been tested regarding their capacity in inhibit Candida spp. virulence factors. Among these compounds, a significant lower number of works are focused on the inhibition action caused by different types of surfactant. The present work aimed to evaluate the effect generated by the surfactants cetyltrimethylammonium chloride (CTAC), sodium dodecyl sulfate (SDS), N-hexadecyl-N–N′-dimethyl-3-ammonio-1-propane-sulfonate (HPS) and octylphenoxypolyethoxyethanol (Triton X-100) on the viability, adhesion ability and exoenzyme production by Candida species. CTAC and HPS were capable to inhibit Candida spp. growth at very low concentrations. All surfactants demonstrated to be capable to inhibit the adhesion of Candida species to buccal epithelial cells (BEC) and the proteinase production. On the other hand, the phospholipase production remained unaltered after the treatment with these compounds. The present data denote that cationic and zwitterionic surfactants are interesting prototypes of inhibitory agents against Candida spp., which is probably associated with the cationic punctual charge of both surfactants. The results are discussed in details in agreement with recent reports from literature.     

Impacts of soil temperature,phenology and plant community composition on invertebrate herbivory in a natural warming experiment

Species and community-level responses to warming are well documented, with plants and invertebrates known to alter their range, phenology or composition as temperature increases. The effects of warming on biotic interactions are less clearly understood, but can have consequences that cascade through ecological networks. Here, we used a natural soil temperature gradient of 5–35°C in the Hengill geothermal valley, Iceland, to investigate the effects of temperature on plant community composition and plant–invertebrate interactions. We quantified the level of invertebrate herbivory on the plant community across the temperature gradient and the interactive effects of temperature, plant phenology (i.e. development stage) and vegetation community composition on the probability of herbivory for three ubiquitous plant species, Cardamine pratensis, Cerastium fontanum and Viola palustris. We found that the percentage cover of graminoids and forbs increased, while the amount of litter decreased, with increasing soil temperature. Invertebrate herbivory also increased with soil temperature at the plant community level, but this was underpinned by different effects of temperature on herbivory for individual plant species, mediated by the seasonal development of plants and the composition of the surrounding vegetation. This illustrates the importance of considering the development stage of organisms in climate change research given the variable effects of temperature on susceptibility to herbivory at different ontogenetic stages.     

Illuminating the evolutionary history of liverworts (Marchantiophyta)—towards a natural classification

The phylogenetic relationships of liverworts were reconstructed using the sequence data of four genome regions including rbcL, rps4 and trnL‐F of the chloroplast and 26S large subunit ribosomal rRNA gene of the nucleus, and 90 characters of morphological, ultrastructural and developmental aspects. The taxa sampled consisted of 159 species including 135 liverworts (108 genera, 54 families and 29 suborders), 13 mosses, two hornworts, seven vascular plants and two charophyte algae. Analyses based on maximum parsimony using both direct optimization (POY) and static alignment (NONA), as well as Bayesian inference (MrBayes) were done. All the data sets were analyzed simultaneously. Our study confirms that liverworts compose a monophyletic group which consists of three classes. The class Treubiopsida including both Treubia and Haplomitrium is resolved as the earliest diverging liverwort lineage. Blasia and the complex thalloids are assigned to the Marchantiopsida, under which Blasiidae and Marchantiidae are divided. Marchantiidae include Sphaerocarpales and Marchantiales. The simple thalloid and leafy liverworts form the Jungermanniopsida, which is further divided to subclasses Pelliidae subclassis nov., Metzgeriidae and Jungermanniidae. Metzgeriidae here is defined to include only Metzgeriaceae, Aneuraceae and Vandiemeniaceae, and is the sister group to the leafy liverworts. The leafy liverworts Jungermanniidae include the orders Pleuroziales, Porellales and Jungermanniales. It is assumed that the Porellales and the Jungermanniales have split early, at least in the Jurassic period. In the Porellales, the diversification rate may have remained relatively constant for long periods of time but speeding up only recently within some of the families, associated with an explosive radiation of angiosperms. The Jungermanniales are most probably a recently diversified group which has attained the greatest profusion of structure and the most remarkable diversity of leaf development and protective devices for maturing sporophytes. A detailed classification scheme for liverworts is presented. © The Willi Hennig Society 2006.     

Effects of weaning age and formic acid-based feed additives on pigs from weaning to slaughter

Two hundred and forty piglets were used in a 2 x 6 factorial experiment to study the effects of weaning age (26 or 36 d) and four formic acid-based feed additives on the performance of pigs from weaning to slaughter. Either formic acid (F) or a mixture of formic acid, propionic acid, and potassium sorbate (FPS) or a mixture of formic acid, propionic acid, and sodium benzoate (FPB) or formic acid in a diatomaceous earth carrier (FD) were added to the diets of weaned piglets (from weaning to 60 d of age) and growing (18-46 kg) and finishing pigs (46-107 kg) to provide 8, 6, and 6 g acid per kg feed, respectively. The negative control treatment's (C) diets contained no growth promoters, whereas the positive control treatment's weaner and grower diets were supplemented with 40 mg/kg of avilamycin (A). The piglets weaned at the age of 26 and 36 d weighed 7.6 and 10.7 kg at weaning (p < 0.001), and 18.5 and 17.9 kg at the age of 60 d (p > 0.05), respectively. There was a weaning age x feed additive interaction in the weight gain of piglets after weaning (p < 0.05). The weight gain of piglets weaned on day 26 was enhanced by A, FPS, and FD (p < 0.05), and that of piglets weaned on day 36 by A and FPB (p < 0.05). The feed conversion ratio was not affected by weaning ages but was decreased in groups A, F, FBS, and FPB (p < 0.05). The severity of post-weaning diarrhoea was less in groups A, F, FPS, and FD than in C (p < 0.05). In piglets weaned on day 26, faecal water content and the total Escherichia coli count were highest 9 d after weaning. The total E. coli count was reduced only by FD (p < 0.05). Increased faecal water content was characterized by increased faecal Na+ and decreased K+ concentrations. Weaning age did not influence performance or carcass quality in the growing-finishing pigs. Feed additives did not affect weight gain in the growing pigs, but FPS and FPB enhanced weight gain during finishing period and total fattening (p < 0.05). In summary, the pigs' growth performance from weaning to slaughter was not affected by weaning age but it was enhanced by mixtures of formic and propionic acids with small amounts of sorbate or benzoate.     

In vitro gap-directed translesion DNA synthesis of an abasic site involving human DNA polymerases epsilon, lambda, and beta

DNA polymerase (pol) ε is thought to be the leading strand replicase in eukaryotes, whereas pols λ and β are believed to be mainly involved in re-synthesis steps of DNA repair. DNA elongation by the human pol ε is halted by an abasic site (apurinic/apyrimidinic (AP) site). In this study, we present in vitro evidence that human pols λ, β, and η can perform translesion synthesis (TLS) of an AP site in the presence of pol ε, likely by initiating the 3'OHs created at the lesion by the arrested pol ε. However, in the case of pols λ and β, this TLS requires the presence of a DNA gap downstream from the product synthesized by the pol ε, and the optimal gap for efficient TLS is different for the two polymerases. The presence of gaps did not affect the TLS capacity of human pol η. Characterization of the reaction products showed that pol β inserted dAMP opposite the AP site, whereas gap filling synthesis by pol λ resulted in single or double deletions opposite the lesion. The synthesis up to the AP site by pol ε and the subsequent TLS by pols λ and β are not influenced by human processivity factor proliferating cell nuclear antigen and human single-stranded DNA-binding protein replication protein A. The bypass capacity of pol λ at the AP site is greatly reduced when a truncated form of the enzyme, which has lost the BRCA1 C-terminal and proline-rich domains, is used. Collectively, our in vitro results support the existence of a mechanism of gap-directed TLS at an AP site involving a switch between the replicative pol ε and the repair pols λ and β.     

Micro‐fungi and invertebrate herbivores on birch trees: fungal mediated plant–herbivore interactions or responses to host quality?

We studied interactions between microfungi and herbivores sharing a host tree. In a series of experiments and field observations over a 3‐year period, we compared phenotypic and genetic correlations of fungal frequencies and performance of invertebrate herbivores growing on mature half‐sib progenies of mountain birches (Betula pubescens ssp. czerepanovii) in two environments, a forested river valley and an adjacent higher‐elevation mountain birch woodland. We found little support for direct relation between fungal frequencies and performance of herbivore species. Instead, genetic correlations, particularly between autumnal moth (Epirrita autumnata) and rust fungus (Melampsoridium betulinum), suggest that herbivore performance may be caused by (1) genetic differences in plant quality for fungi and herbivores, or (2) genetic differences in responses to environmental conditions.     

The Formation of Otoliths in the Frog Rana esculenta. Scanning Electron Microscopic and X-Ray Diffraction Studies

Two crystal forms of calcium carbonate were observed: calcite (utricle) and aragonite (saccule, lagena, endolymphatic sac). The first step in otolith formation is the appearance of organic structures in the macula. The subsequent step is characterized by fast growing primitive crystals with a prismatic habitus that successively transform into adult or mature crystals. With the metamorphosis, the aragonite crystals of the endolymphatic organ show clear signs of erosion that can be related to a process of CaCO₃ mobilization from such deposits.     

The BUME method: a novel automated chloroform-free 96-well total lipid extraction method for blood plasma

Lipid extraction from biological samples is a critical and often tedious preanalytical step in lipid research. Primarily on the basis of automation criteria, we have developed the BUME method, a novel chloroform-free total lipid extraction method for blood plasma compatible with standard 96-well robots. In only 60 min, 96 samples can be automatically extracted with lipid profiles of commonly analyzed lipid classes almost identically and with absolute recoveries similar or better to what is obtained using the chloroform-based reference method. Lipid recoveries were linear from 10-100 μl plasma for all investigated lipids using the developed extraction protocol. The BUME protocol includes an initial one-phase extraction of plasma into 300 μl butanol:methanol (BUME) mixture (3:1) followed by two-phase extraction into 300 μl heptane:ethyl acetate (3:1) using 300 μl 1% acetic acid as buffer. The lipids investigated included the most abundant plasma lipid classes (e.g., cholesterol ester, free cholesterol, triacylglycerol, phosphatidylcholine, and sphingomyelin) as well as less abundant but biologically important lipid classes, including ceramide, diacylglycerol, and lyso-phospholipids. This novel method has been successfully implemented in our laboratory and is now used daily. We conclude that the fully automated, high-throughput BUME method can replace chloroform-based methods, saving both human and environmental resources.