Length, orientation, and plant host influence the mutation frequency in microsatellites.

Microsatellites are simple, tandem DNA repeats that represent unstable regions of the genome. They undergo frequent changes in tract length by base additions or deletions due to DNA polymerase slippage during replication. To characterize factors affecting the frequency of spontaneous mutations occurring in microsatellites in plants, a reporter system was used in Arabidopsis thaliana and tomato (Lycopersicon esculentum). The beta-glucuronidase (GUS) reporter system was used to measure the mutation frequency in various microsatellites (G(7), G(10), G(13), G(16), and C(16)) in somatic tissues. Our results indicate that this frequency increases with the number of repeats: a G(16) tract was almost 80-fold more mutable than a G(7) tract. Furthermore, the frequency of mutations depends on repeat orientation, as G(16) was 3-fold more mutable than C(16). The mutation rate was also found to differ markedly in Arabidopsis and tomato for an identical microsatellite. Indeed, Arabidopsis showed a 5-fold higher mutation frequency than tomato with the same G(7) reporter construct. Finally, mutation in a G(16) tract was frequent enough that mutations transmitted germinally to the next generation could be detected at a relatively high frequency.     

Pleiotropic QTL on chromosome 12q23-q24 influences triglyceride and high-density lipoprotein cholesterol levels: the HERITAGE family study

To determine whether a common quantitative trait locus (QTL) influences the variation of fasting triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) levels, we used a bivariate multipoint linkage analysis with 654 polymorphic markers in 99 white and 101 black families. The phenotypes were investigated under two conditions: at baseline and after a 20-week exercise training intervention. A maximum genome-wide bivariate LOD score of 3.0 (p = 0.00010) was found on chromosome 12q23-q24, located within the IGF1 gene (insulin-like growth factor 1, at 107 cM) for TG and HDL-C at baseline in whites. This bivariate linkage peak is considerably higher than the univariate linkage results at the same chromosome location for either trait (for TG, LOD = 2.07, p = 0.00108; for HDL-C, LOD = 2.04, p = 0.00101). The genetic correlations between baseline TG and HDL-C levels were -0.14 for the residual and -0.33 for the QTL components. Moreover, association analysis showed that TG, HDL-C, and IGF1 are significantly associated (p = 0.04). In conclusion, these results suggest that a QTL on chromosome 12q23-q24 influences the variation of plasma TG and HDL-C levels. Further investigation should confirm whether IGF1 or another nearby gene is responsible for the concomitant variation in TG and HDL-C levels.     

DNA synthesized at pachytene in Lilium: A non-divergent subclass of moderately repetitive sequences

Moderately repetitive sequences of Lilium DNA synthesized during pachytene consist of families that have a considerably lower divergence than those of total genomic middle repeat DNA, the latter having an average divergence of 10%. 80% of the sequences synthesized during the early phase of pachytene and 100% of those synthesized during the latter phase of pachytene reassociate with perfect or near-perfect fidelity. Except for the small amount of DNA synthesized during early pachytene, pachytene middle repeat sequences are non-divergent and thus constitute a distinctive subset of total moderately repetitive DNA. The modal length of pachytene and total middle repeat sequences are similar. In contrast to earlier measurements based on isotope incorporation, the modal length is of the order of 1500–2000 base pairs, ten times the previously estimated size. Calculations based on the new length lead to the conclusion that pachytene middle repeat sequences account for 1% of the genome.     

Macro-scale topology optimization for controlling internal shear stress in a porous scaffold bioreactor

Shear stress is an important physical factor that regulates proliferation, migration, and morphogenesis. In particular, the homeostasis of blood vessels is dependent on shear stress. To mimic this process ex vivo, efforts have been made to seed scaffolds with vascular and other cell types in the presence of growth factors and under pulsatile flow conditions. However, the resulting bioreactors lack information on shear stress and flow distributions within the scaffold. Consequently, it is difficult to interpret the effects of shear stress on cell function. Such knowledge would enable researchers to improve upon cell culture protocols. Recent work has focused on optimizing the microstructural parameters of the scaffold to fine tune the shear stress. In this study, we have adopted a different approach whereby flows are redirected throughout the bioreactor along channels patterned in the porous scaffold to yield shear stress distributions that are optimized for uniformity centered on a target value. A topology optimization algorithm coupled to computational fluid dynamics simulations was devised to this end. The channel topology in the porous scaffold was varied using a combination of genetic algorithm and fuzzy logic. The method is validated by experiments using magnetic resonance imaging readouts of the flow field.     

Synthesis and cytotoxicity of lupane-type triterpenoid glyceryl esters

A new series of betulinic acid and betulin derivatives were synthesized by introducing a D-glycerol moiety at the C-3 and/or C-28 positions of the lupane skeleton. The resulting glyceryl esters were evaluated in vitro for their cytotoxic activity against A549, DLD-1 and WS1 human cell lines. The structure-activity relationships study revealed that the incorporation of a glycerol unit at the C-3 or C-28 position of the lupane core resulted in compounds exhibiting potent cytotoxic activity together with decreased liposolubility.     

Species loss of stoneflies (Plecoptera) in the Czech Republic during the 20th century

1. Rapid expansion and intensification of anthropogenic activities in the 20th century has caused profound changes in freshwater assemblages. Unfortunately, knowledge of the extent and causes of species loss (SL) is limited due to the lack of reliable historical data. An unusual data set allows us to compare changes in the most sensitive of aquatic insect orders, the Plecoptera, at some 170 locations in the Czech Republic between two time periods, 1955–1960 and 2006–2010. Historical data (1890–1911) on assemblages of six lowland rivers allow us to infer even earlier changes. 2. Regional stonefly diversity decreased in the first half of the 20th century. Streams at lower altitudes lost a substantial number of species, which were never recovered. In the second half of the century, large‐scale anthropogenic pressure caused SL in all habitats, leading to a dissimilarity of contemporary and previous assemblages. The greatest changes were found at sites affected by organic pollution and a mixture of organic pollution and channelisation or impoundment. Colonisation of new habitats was observed in only three of the 80 species evaluated. 3. Species of moderate habitat specialisation and tolerance to organic pollution were most likely to be lost. Those with narrow specialisations in protected habitats were present in both historical and contemporary collections. 4. Contemporary assemblages are the consequence of more than a 100 years of anthropogenic impacts. In particular, streams at lower altitude and draining intensively exploited landscapes host a mere fragment of the original species complement. Most stonefly species are less frequently present than before, although their assemblages remain almost intact in near‐natural mountain streams. Our analyses demonstrate dramatic restriction of species ranges and, in some cases, apparent changes in altitudinal preference throughout the area.     

Using biofeedback while immersed in a stressful videogame increases the effectiveness of stress management skills in soldiers

This study assessed the efficacy of using visual and auditory biofeedback while immersed in a tridimensional videogame to practice a stress management skill (tactical breathing). All 41 participants were soldiers who had previously received basic stress management training and first aid training in combat. On the first day, they received a 15-minute refresher briefing and were randomly assigned to either: (a) no additional stress management training (SMT) for three days, or (b) 30-minute sessions (one per day for three days) of biofeedback-assisted SMT while immersed in a horror/first-person shooter game. The training was performed in a dark and enclosed environment using a 50-inch television with active stereoscopic display and loudspeakers. On the last day, all participants underwent a live simulated ambush with an improvised explosive device, where they had to provide first aid to a wounded soldier. Stress levels were measured with salivary cortisol collected when waking-up, before and after the live simulation. Stress was also measured with heart rate at baseline, during an apprehension phase, and during the live simulation. Repeated-measure ANOVAs and ANCOVAs confirmed that practicing SMT was effective in reducing stress. Results are discussed in terms of the advantages of the proposed program for military personnel and the need to practice SMT.