Vibration attraction response is a plastic trait in blind Mexican tetra (Astyanax mexicanus), variable within subpopulations inhabiting the same cave

Animals evolve their sensory systems and foraging behaviours to adapt and colonize new and challenging habitats such as the dark cave environment. Vibration attraction behaviour (VAB) gives fish the ability to locate the source of a water disturbance in the darkness. VAB evolved in the blind Mexican cave tetra, Astyanax mexicanus. VAB is triggered in cavefish by vibration stimuli peaking at 35 Hz, which is within the main spectrum of water fluctuations produced by many prey crustaceans and insects. VAB has a genetic component and is correlated to an increased number of head mechanosensory neuromasts in the eye orbital region when compared to surface fish. Previous competitive prey capture assays have supported the advantage of VAB for foraging in the dark. Despite its putative adaptive function, VAB has been described as absent in some Astyanax cave populations (Tinaja and Molino) but present in others (Pachón, Piedras, Toro and Sabinos). Here we have tested the occurrence of VAB in the field and in multiple cave populations using a vibrating device in natural pools. Our results confirmed the presence of VAB in caves such as Pachón, Toro and Sabinos but showed that VAB is also present in the Tinaja and Molino cave populations, previously reported as VAB-negative in laboratory experiments. Thus, VAB is available throughout the range of hypogean A. mexicanus. However, and most notably, within a given cave the levels of VAB were highly variable among different pools. Fish at one pool may express no VAB, while fish at another nearby pool of the same cave may actively show VAB. While a variety of environmental conditions may foster this diversity, we found that individuals inhabiting pools with a high abundance of organic matter have reduced expression of VAB. In contrast, in pools with little organic debris where fish probably depend more on hunting than on scavenging, VAB is enhanced. Our results suggest that expression of VAB is a plastic trait whose variability can depend on local conditions. Such plasticity may be required within and among caves where high environmental variability between pools results in a diverse availability of food.     

The SSV-Seq 2.0 PCR-Free Method Improves the Sequencing of Adeno-Associated Viral Vector Genomes Containing GC-Rich Regions and Homopolymers

Adeno-associated viral vectors (AAV) are efficient engineered tools for delivering genetic material into host cells. The commercialization of AAV-based drugs must be accompanied by the development of appropriate quality control (QC) assays. Given the potential risk of co-transfer of oncogenic or immunogenic sequences with therapeutic vectors, accurate methods to assess the level of residual DNA in AAV vector stocks are particularly important. An assay based on high-throughput sequencing (HTS) to identify and quantify DNA species in recombinant AAV batches is developed. Here, it is shown that PCR amplification of regions that have a local GC content >90% and include successive mononucleotide stretches, such as the CAG promoter, can introduce bias during DNA library preparation, leading to drops in sequencing coverage. To circumvent this problem, SSV-Seq 2.0, a PCR-free protocol for sequencing AAV vector genomes containing such sequences, is developed. The PCR-free protocol improves the evenness of the rAAV genome coverage and consequently leads to a more accurate relative quantification of residual DNA. HTS-based assays provide a more comprehensive assessment of DNA impurities and AAV vector genome integrity than conventional QC tests based on real-time PCR and are useful methods to improve the safety and efficacy of these viral vectors.     

Toward a Generalised Tensegrity Model Describing the Mechanical Behaviour of the Cytoskeleton Structure

The control of many cell functions including growth, migration and mechanotransduction, depends crucially on stress-induced mechanical changes in cell shape and cytoskeleton (CSK) structure. Quantitative studies have been carried out on 6-bar tensegrity models to analyse several mechanical parameters involved in the mechanical responses of adherent cells (i.e. strain hardening, internal stress and scale effects). In the present study, we attempt to generalize some characteristic mechanical laws governing spherical tensegrity structures, with a view of evaluating the mechanical behaviour of the hierarchical multi-modular CSK-structure. The numerical results obtained by studying four different tensegrity models are presented in terms of power laws and point to the existence of unique and constant relationships between the overall structural stiffness and the local properties (length, number and internal stress) of the constitutive components.     

Synthesis of imidazole-containing analogues of farnesyl pyrophosphate and evaluation of their biological activity on protein farnesyltransferase

With the aim of creating new bisubstrate inhibitors of protein farnesyltransferase (FTase), new carboxylic farnesyl pyrophosphate analogues have been designed and synthesized. The original structures are built around three elements: a prenyl moiety, a 1,4-diacid motif and an imidazole ring. All the compounds were evaluated for their ability to inhibit FTase and compared with the corresponding derivatives lacking the imidazole ring, synthesized for that purpose. These new compounds are not bisubstrate inhibitors probably because the imidazole ring is not in the right position to interact with the zinc atom. However these derivatives display FPP competitive inhibition with a good activity in the carboxylic farnesyl pyrophosphate analogues series.     

Antileishmanial activities and mechanisms of action of indole-based azoles

Two 3-(α-azolylbenzyl)indoles were evaluated against Leishmania amastigotes. Both compounds proved to be very active against intracellular and axenic amastigotes. The IC₅₀ values of the imidazole derivative, PM17, and the triazole analogue, PM19, against L. mexicana axenic amastigotes, were 4.4 ± 0.1 and 6.4 ± 0.1 μM, respectively. Against intracellular amastigotes, PM17 produced a 66% decrease of leishmanial burden at 1 μM and PM19 had an IC₅₀ of 1.3 μM. In a Balb/c mice model of L. major leishmaniasis, administration of PM17 led to a clear-cut parasite burden reduction: 98.9% in the spleen, 79.0% in the liver and 49.9% in the popliteal node draining the cutaneous lesion. As anticipated, it was brought to the fore that PM17 decreases ergosterol biosynthesis leading to membrane fungal cell alterations. Moreover it was proved that this imidazole antifungal agent induces a parasite burden-correlated decrease in interleukine-4 production both in the splenocyte and the popliteal node of the mouse.     

Apodemia mormo in Canada: population genetic data support prior conservation ranking

Like many species, the Mormon Metalmark butterfly (Apodemia mormo) has been given conservation ranking in Canada based on limited data. This species is widespread across western North America, but has only two populations in Canada: an “endangered” population in the Similkameen valley of British Columbia, and a “threatened” population in Grasslands National Park (GNP) in Saskatchewan. Here we present genetic data from 1498 base pairs of the cytochrome oxidase I gene sequence and six novel microsatellite loci in order to assess (1) whether the two populations are related, (2) the degree to which they are genetically diverse and demographically stable, and (3) what their relationships are to the nearest unranked populations of A. mormo across the Canada-United States border. Our principal conclusion is that the two populations are not closely related genetically. We also found that the British Columbia population is genetically depauperate and, with the exception of the nearest neighboring populations across the border, not recently genetically connected to other populations in the Pacific Northwest. In comparison, the Saskatchewan population is genetically diverse, and gene flow occurs with several other eastern populations. Population structure was not detected within either the British Columbia or the Saskatchewan populations. This research supports the prior conservation rankings of both populations and provides new insight that will help to inform future management decisions for the Canadian populations of this charismatic butterfly.     

The Use of Biatain Ag in Hard-to-Heal Venous Leg Ulcers: Meta-Analysis of Randomised Controlled Trials

Background

Venous leg ulcers are common, troublesome, and their failure to heal is often related to a heavy bio-burden. Ionized silver has both anti-inflammatory and antimicrobial properties. The ulcer healing properties of the silver releasing foam dressing Biatain Ag has been examined in 4 randomized controlled trials (RCTs).

Aim

To evaluate ulcer healing through a meta-analytic approach after treatment with either Biatain Ag or a non-active dressing.

Patients and Methods

685 subjects with pure or mixed hard-to-heal venous leg ulcers were included in the meta-analysis.

Results

Biatain Ag showed a significant treatment effect (p<0.0001), responder rate (p<0.001), and healing rate (p = 0.002).

Conclusion

The meta-analysis of the 4 RCTs provided statistical significant evidence to support the use of Biatain Ag dressing in treatment of hard-to-heal venous leg ulcers.     

Influence of Ovarian Hormones on Cortical Spreading Depression and Its Suppression by L-kynurenine in Rat

Migraine is sexually dimorphic and associated in 20–30% of patients with an aura most likely caused by cortical spreading depression (CSD). We have previously shown that systemic L-kynurenine (L-KYN), the precursor of kynurenic acid, suppresses CSD and that this effect depends on the stage of the estrous cycle in female rats. The objectives here are to determine the influence of ovarian hormones on KCl-induced CSD and its suppression after L-KYN by directly modulating estradiol or progesterone levels in ovariectomized rats. Adult female rats were ovariectomized and subcutaneously implanted with silastic capsules filled with progesterone or 17β-estradiol mixed with cholesterol, with cholesterol only or left empty. Two weeks after the ovariectomy/capsule implantation, the animals received an i.p. injection of L-KYN (300 mg/kg) or NaCl as control. Thirty minutes later CSDs were elicited by applying KCl over the occipital cortex and recorded by DC electrocorticogram for 1 hour. The results show that both estradiol and progesterone increase CSD frequency after ovariectomy. The suppressive effect of L-KYN on CSD frequency, previously reported in normal cycling females, is not found anymore after ovariectomy, but reappears after progesterone replacement therapy. Taken together, these results emphasize the complex role of sex hormones on cortical excitability. The CSD increase by estradiol and, more surprisingly, progesterone may explain why clinically migraine with aura appears or worsens during pregnancy or with combined hormonal treatments.