The enterotoxin gene (cpe) of Clostridium perfringens can be chromosomal or plasmid-borne

The location of the cpe gene, encoding the enterotoxin responsible for food poisoning in humans, has been studied in a series of enterotoxigenic Ciostridium perfringens strains by means of pulsed field gel electrophoresis of genomic DNA. The cpe gene was found at the same chromosomal locus in strains associated with food poisoning in humans and was shown to be linked to a repetitive sequence, the Hin dlll repeat, and an open reading frame, ORF3, that may be part of an insertion sequence. In contrast, when the strains originated from domesticated livestock cpe was located on a large episome where it was often close to a copy of the transposable element IS 1151. In these cases, the Hin dlll repeat was not linked to the cpe gene although this was generally preceded by ORF3.     

Ants impact the composition of the aquatic macroinvertebrate communities of a myrmecophytic tank bromeliad

In an inundated Mexican forest, 89 out of 92 myrmecophytic tank bromeliads (Aechmea bracteata) housed an associated ant colony: 13 sheltered Azteca serica, 43 Dolichoderus bispinosus, and 33 Neoponera villosa. Ant presence has a positive impact on the diversity of the aquatic macroinvertebrate communities (n = 30 bromeliads studied). A Principal Component Analysis (PCA) showed that the presence and the species of ant are not correlated to bromeliad size, quantity of water, number of wells, filtered organic matter or incident radiation. The PCA and a generalized linear model showed that the presence of Azteca serica differed from the presence of the other two ant species or no ants in its effects on the aquatic invertebrate community (more predators). Therefore, both ant presence and species of ant affect the composition of the aquatic macroinvertebrate communities in the tanks of A. bracteata, likely due to ant deposition of feces and other waste in these tanks.     

Cell motility measurements with an automated microscope system

The motility of 3T3 cells has been studied using a newly developed automated microscope system which is capable of recognizing live unstained cells growing in tissue culture. A large number of individual cells can be rapidly identified and characterized and their precise positions recorded. All cells can be revisited automatically every few minutes, and the new cell positions can be determined. Quantitative data from up to 1 000 cells can then be obtained, and cell movement parameters like cell speed, distance travelled, direction of movement, etc., can be measured for individual cells and for the whole cell population. In addition, for any number of chosen cells, high-resolution digitized images can be taken for further morphological studies, including acquisition of images of individual cells.     

Esa1, an Arabidopsis mutant with enhanced susceptibility to a range of necrotrophic fungal pathogens, shows a distorted induction of defense responses by reactive oxygen generating compounds

An Arabidopsis thaliana mutant, esa1, that shows enhanced susceptibility to the necrotrophic pathogens Alternaria brassicicola, Botrytis cinerea and Plectosphaerella cucumerina, but has wild-type levels of resistance to the biotrophic pathogens Pseudomonas syringae pv. tomato and Peronospora parasitica. The enhanced susceptibility towards necrotrophic pathogens correlated with a delayed induction of phytoalexin accumulation and delayed induction of the plant defensin gene PDF1.2 upon inoculation with pathogens. Two reactive oxygen generating compounds, paraquat and acifluorfen, were found to cause induction of both phytoalexin accumulation and PDF1.2 expression in wild-type plants, but this induction was almost completely abolished in esa1. This finding suggests that esa1 may somehow be involved in transduction of signals generated by reactive oxygen species.     

3D nuclear organization of telomeres in the Hodgkin cell lines U-HO1 and U-HO1-PTPN1: PTPN1 expression prevents the formation of very short telomeres including "t-stumps"

Background  

In cancer cells the three-dimensional (3D) telomere organization of interphase nuclei into a telomeric disk is heavily distorted and aggregates are found. In Hodgkin's lymphoma quantitative FISH (3D Q-FISH) reveals a major impact of nuclear telomere dynamics during the transition form mononuclear Hodgkin (H) to diagnostic multinuclear Reed-Sternberg (RS) cells. In vitro and in vivo formation of RS-cells is associated with the increase of very short telomeres including "t-stumps", telomere loss, telomeric aggregate formation and the generation of "ghost nuclei".     

Schwartz Formula: Is One k-Coefficient Adequate for All Children?

Background/Objective

Plasma-creatinine-based equations to estimate the glomerular filtration rate are recommended by several clinical guidelines. In 2009, Schwartz et al. adapted the traditional Schwartz equation to children and adolescents but did not find different k-coefficients between children and adolescents (k = 36.5 for all patients). We reevaluated the coefficient of the 2009-Schwartz formula according to sex and age in a pediatric population.

Patients/Methods

We used linear mixed-effects models to reestimate the 2009-Schwartz k-coefficient in 360 consecutive French subjects aged 1 to 18 years referred to a single centre between July 2003 and July 2010 (965 measurements). We assessed the agreement between the estimated glomerular filtration rate obtained with the new formula (called Schwartz-Lyon) and the rate measured by inulin clearance. We then compared this agreement to the one between the measured glomerular filtration rate and 2009-Schwartz formula, first in the French then in a Swedish cohort.

Results

In Schwartz-Lyon formula, k was estimated at 32.5 in boys <13 years and all girls and at 36.5 in boys aged ≥13 years. The performance of this formula was higher than that of 2009-Schwartz formula in children <13 years. This was first supported by a statistically significant reduction of the overestimation of the measured glomerular filtration rate in both cohorts, by better 10% and 30% accuracies, and by a better concordance correlation coefficient.

Conclusions

The performance and simplicity of Schwartz formula are strong arguments for its routine use in children and adolescents. The specific coefficient for children aged <13 years further improves this performance.     

Presence of effector CD8+ T cells in hepatitis C virus-exposed healthy seronegative donors.

CTL responses against multiple hepatitis C virus (HCV) epitopes were detected in 7 of 29 (24.1%) healthy family members (HFM) persistently exposed to chronically HCV-infected patients (HCV-HFM). These precursor CTL were at very low or undetectable frequencies, as determined by limiting dilution analysis. However, when HCV-specific effector CD8+ T cells, freshly isolated from PBMC of HCV-HFM, were assessed by a sensitive enzyme-linked immunospot assay, their frequencies were severalfold higher than those of precursor CTL. These results indicate that the two assays detect two functionally distinct T cell populations and that the effector cells are not assayed by the 51Cr-release assay. Furthermore, the combination of cell depletion and enzyme-linked immunospot analyses showed that the effector cells were confined into a CD8+ CD45RO+ CD28- population. The persistence of effector CD8+ T cells specific for both the structural and nonstructural viral proteins in uninfected HCV-HFM, suggest that: 1) an immunological memory is established upon a subclinical infection without any evidence of hepatitis, in a large cohort of HCV-exposed individuals; 2) because these cells required neither restimulation nor the addition of particular cytokines in vitro for differentiating in effectors, they should be capable of prompt HCV-specific effector function in vivo, possibly providing antiviral protection; and 3) the maintenance of effector T cell responses may be sustained by persisting low-level stimulation induced by inapparent infections.