Lipid nanopores can form a stable, ion channel-like conduction pathway in cell membrane

Cell permeabilization by electric pulses (EPs), or electroporation, has been well established as a tool to indiscriminately increase membrane flows of water solutes down the concentration and voltage gradients. However, we found that EPs of nanosecond duration (nsEPs) trigger formation of voltage-sensitive and inward-rectifying membrane pores. NsEP-treated cells remain mostly impermeable to propidium, suggesting that the maximum pore size is ∼1 nm. The ion-channel-like properties of nsEP-opened nanopores vanish if they break into larger, propidium-permeable “conventional” pores. However, nanopores can be stable for many minutes and significantly impact cell electrolyte and water balance. Multiple nsEPs cause fast cell swelling and blebbing, whereas opening of larger pores with digitonin abolishes swelling and causes blebs to implode. The lipid nature of nsEP-opened nanopores is confirmed by fast externalization of phosphatidylserine residues. Nanopores constitute a previously unexplored ion transport pathway that supplements classic ion channels but is distinctly different from them.     

Hypertrophy is induced during the in vitro chondrogenic differentiation of human mesenchymal stem cells by bone morphogenetic protein-2 and bone morphogenetic protein-4 gene transfer

Introduction  

The present study compares bone morphogenetic protein (BMP)-4 and BMP-2 gene transfer as agents of chondrogenesis and hypertrophy in human primary mesenchymal stem cells (MSCs) maintained as pellet cultures.     

Combined effects of patch size and plant nutritional quality on local densities of insect herbivores

Plant–insect interactions occur in spatially heterogeneous habitats. Understanding how such interactions shape density distributions of herbivores requires knowledge on how variation in plant traits (e.g. nutritional quality) affects herbivore abundance through, for example, affecting movement rates and aggregation behaviour. We studied the effects of plant patch size and herbivore-induced differences in plant nutritional quality on local densities of insect herbivores for two Brassica oleracea cultivars, i.e. white cabbage and Brussels sprouts. Early season herbivory as a treatment resulted in measurable differences in glucosinolate concentrations in both cultivars throughout the season. Herbivore induction and patch size both influenced community composition of herbivores in both cultivars, but the effects differed between species. Flea beetles (Phyllotreta spp.) were more abundant in large than in small patches, and this patch response was more pronounced on white cabbage than on Brussels sprouts. Herbivore-induction increased densities in all patches. Thrips tabaci was also more abundant in large patches and densities of this species were higher on Brussels sprouts than on white cabbage. Thrips densities were lower on induced than on control plants of both cultivars and this negative effect of induction tended to be more pronounced in large than in small patches. Densities of the cabbage moth (Mamestra brassicae) were lower on Brussels sprouts than on white cabbage and lower on herbivore-induced than on uninduced plants, with no effect of patch size. No clear effects of patch size and induction were found for aphids. This study shows that constitutive and herbivore-induced differences in plant traits interact with patch responses of insect herbivores.     

Genotyping of Giardia duodenalis Cysts by New Real-Time PCR Assays for Detection of Mixed Infections in Human Samples

Of the seven genetic groups, or assemblages, currently recognized in the Giardia duodenalis species complex, only assemblages A and B are associated with human infection, but they also infect other mammals. Recent investigations have suggested the occurrence of genetic exchanges among isolates of G. duodenalis, and the application of assemblage-specific PCR has shown both assemblages A and B in a significant number of human infections. In this work, three real-time quantitative (qPCR) assays were developed to target the G. duodenalis triose phosphate isomerase, glutamate dehydrogenase, and open reading frame C4 sequences. Primers were designed to allow the specific amplification of the DNA of assemblage A or B and to generate products distinguishable by their melting curves or, after qPCR, by their sequences, sizes, or restriction patterns. The assays showed full specificity and detected DNA from a single trophozoite (4 to 8 target copies). We applied these assays, as well as a TaqMan assay that targets the β-giardin gene, to genomic DNA extracted from 30 human stools and to Giardia cysts purified by immunomagnetic capture from the same samples. Simultaneous detection of both assemblages was observed in a large number of DNAs extracted from stools, and experiments on the cysts purified from the same samples showed that this was essentially attributable to mixed infections, as only one assemblage was detected when dilutions of cysts were tested. In a few cases, detection of both assemblages was observed even when single cysts were tested. This result, which suggests the presence of recombinants, needs to be confirmed using more accurate methods for cyst separation and enumeration. The assays described in this study can be used to detect Giardia cysts infectious to humans in samples from animals and in water and food.Giardia duodenalis (syn. Giardia intestinalis and Giardia lamblia) is the only species within the genus Giardia that infects humans, although it is also found in other mammals, including pets and livestock (1). The infection has a global distribution and, with an estimated 2.8 × 10⁸ cases per year, represents the most common gastrointestinal parasitic infection of humans in developed countries (20). In Asia, Africa, and Latin America, about 200 million people have symptomatic giardiasis, with some 500,000 new cases reported each year (35). Several characteristics of G. duodenalis influence the epidemiology of infection: (i) in humans, the infective dose is about 10 to 100 cysts; (ii) cysts are immediately infectious when excreted in feces and can be transmitted by person-to-person or animal-to-animal contact; (iii) cysts are remarkably stable and can survive for weeks to months in the environment; and (iv) environmental contamination can lead to the contamination of drinking water and food (6, 32).A considerable amount of data has shown that G. duodenalis should be considered a species complex whose members show little variation in their morphology yet can be assigned to at least seven distinct assemblages (A to G) based on genetic analyses (7, 34). The analysis of more than a thousand human isolates from different geographical locations, examined by PCR amplification of DNA extracted directly from feces, has demonstrated that in almost all cases, only G. duodenalis assemblages A and B are associated with human infections (6). The prevalence of each assemblage varies considerably from country to country; assemblage B seems more common overall, but no strong conclusions can be drawn from current data. The remaining assemblages (C to G) are likely to be host specific, as assemblages C and D have been identified in dogs, cats, coyotes, and wolves; assemblage E in cattle, sheep, goats, pigs, water buffaloes, and muflons; assemblage F in cats; and assemblage G in rats.The epidemiology of human giardiasis is further complicated by the occurrence of mixed infections and the possibility of genetic exchanges between isolates of assemblage A (10) or even between isolates of assemblages A and B (21, 33). Ideally, genotyping should be performed on single cysts, as this allows a distinction between mixed infections and recombinants. To reach this technically demanding high level of sensitivity and specificity, real-time quantitative PCR (qPCR) appears to be a promising technique.This work describes the development of new qPCR assays that, through the use of assemblage-specific primers, allow the specific and simultaneous detection of DNAs of assemblages A and B. The application of these assays to DNA extracted from human stools and to cysts purified from the same samples is described.     

Only one independent genetic association with rheumatoid arthritis within the KIAA1109-TENR-IL2-IL21 locus in Caucasian sample sets: confirmation of association of rs6822844 with rheumatoid arthritis at a genome-wide level of significance

Introduction

To investigate whether accelerated hand bone mineral density (BMD) loss is associated with progressive joint damage in hands and feet in the first year of rheumatoid arthritis (RA) and whether it is an independent predictor of subsequent progressive total joint damage after 4 years.

Methods

In 256 recent-onset RA patients, baseline and 1-year hand BMD was measured in metacarpals 2-4 by digital X-ray radiogrammetry. Joint damage in hands and feet were scored in random order according to the Sharp-van der Heijde method at baseline and yearly up to 4 years.

Results

68% of the patients had accelerated hand BMD loss (>-0.003 g/cm²) in the first year of RA. Hand BMD loss was associated with progressive joint damage after 1 year both in hands and feet with odds ratios (OR) (95% confidence intervals [CI]) of 5.3 (1.3-20.9) and 3.1 (1.0-9.7). In univariate analysis, hand BMD loss in the first year was a predictor of subsequent progressive total joint damage after 4 years with an OR (95% CI) of 3.1 (1.3-7.6). Multivariate analysis showed that only progressive joint damage in the first year and anti-citrullinated protein antibody positivity were independent predictors of long-term progressive joint damage.

Conclusions

In the first year of RA, accelerated hand BMD loss is associated with progressive joint damage in both hands and feet. Hand BMD loss in the first year of recent-onset RA predicts subsequent progressive total joint damage, however not independent of progressive joint damage in the first year.