Cannabinoid Receptor CB2 Modulates Axon Guidance

Navigation of retinal projections towards their targets is regulated by guidance molecules and growth cone transduction mechanisms. Here, we present in vitro and in vivo evidences that the cannabinoid receptor 2 (CB₂R) is expressed along the retino-thalamic pathway and exerts a modulatory action on axon guidance. These effects are specific to CB₂R since no changes were observed in mice where the gene coding for this receptor was altered (cnr2 ^−/−). The CB₂R induced morphological changes observed at the growth cone are PKA dependent and require the presence of the netrin-1 receptor, Deleted in Colorectal Cancer. Interfering with endogenous CB₂R signalling using pharmacological agents increased retinal axon length and induced aberrant projections. Additionally, cnr2 ^−/− mice showed abnormal eye-specific segregation of retinal projections in the dorsal lateral geniculate nucleus (dLGN) indicating CB₂R’s implication in retinothalamic development. Overall, this study demonstrates that the contribution of endocannabinoids to brain development is not solely mediated by CB₁R, but also involves CB₂R.     

Accounting for environmental variation in co‐occurrence modelling reveals the importance of positive interactions in root‐associated fungal communities

Understanding the role of interspecific interactions in shaping ecological communities is one of the central goals in community ecology. In fungal communities, measuring interspecific interactions directly is challenging because these communities are composed of large numbers of species, many of which are unculturable. An indirect way of assessing the role of interspecific interactions in determining community structure is to identify the species co‐occurrences that are not constrained by environmental conditions. In this study, we investigated co‐occurrences among root‐associated fungi, asking whether fungi co‐occur more or less strongly than expected based on the environmental conditions and the host plant species examined. We generated molecular data on root‐associated fungi of five plant species evenly sampled along an elevational gradient at a high arctic site. We analysed the data using a joint species distribution modelling approach that allowed us to identify those co‐occurrences that could be explained by the environmental conditions and the host plant species, as well as those co‐occurrences that remained unexplained and thus more probably reflect interactive associations. Our results indicate that not only negative but also positive interactions play an important role in shaping microbial communities in arctic plant roots. In particular, we found that mycorrhizal fungi are especially prone to positively co‐occur with other fungal species. Our results bring new understanding to the structure of arctic interaction networks by suggesting that interactions among root‐associated fungi are predominantly positive.     

Higher host plant specialization of root‐associated endophytes than mycorrhizal fungi along an arctic elevational gradient

How community‐level specialization differs among groups of organisms, and changes along environmental gradients, is fundamental to understanding the mechanisms influencing ecological communities. In this paper, we investigate the specialization of root‐associated fungi for plant species, asking whether the level of specialization varies with elevation. For this, we applied DNA barcoding based on the ITS region to root samples of five plant species equivalently sampled along an elevational gradient at a high arctic site. To assess whether the level of specialization changed with elevation and whether the observed patterns varied between mycorrhizal and endophytic fungi, we applied a joint species distribution modeling approach. Our results show that host plant specialization is not environmentally constrained in arctic root‐associated fungal communities, since there was no evidence for changing specialization with elevation, even if the composition of root‐associated fungal communities changed substantially. However, the level of specialization for particular plant species differed among fungal groups, root‐associated endophytic fungal communities being highly specialized on particular host species, and mycorrhizal fungi showing almost no signs of specialization. Our results suggest that plant identity affects associated mycorrhizal and endophytic fungi differently, highlighting the need of considering both endophytic and mycorrhizal fungi when studying specialization in root‐associated fungal communities.     

The role of omega6 to omega3 ratio in development and progression of age-related macular degeneration

The aim of this study is to investigate possible connection between omega-6/omega-3 fatty acid ratio and development and progression of Age-Related Macular Degeneration (ARMD). We examined 125 patients diagnosed with ARMD and divided into 5 groups of 25 patients according to CARMS (Clinical Age-Related Maculopathy Staging System). Control group consists of 51 patients with similar ages, without ARMD. All of them underwent stereobiomicroscopy, fundus photography and fluorescein angiography. Dietary fatty acids intake was measured using food frequency questionnaire (FFQ). The FFQ was based on previously validated questionnaire (DIETQ, Tinuviel Software, Warington, Ches, UK) and FFQ2 from Blue MountainEye Study. The data were analysed using food nutritient dana from McCance and Widdowson's Food Composition Tables, supplemented with a food fatty acid content database (Foodbase, London, UK). We noticed statistically significant difference between omega-6/omega-3 ratio in neovascular ARMD (stage 5) and all other groups including control group (p = 0.000020). The ratio in Stage 5 was about 11:1 like in Western diet. Stage 4-geographic atrophy (GA) has statistically significant difference in o-mega-6/omega-3 ratio compared with stage 1 (p = 0.000571), stage 2 (p = 0.000112) and stage3 (p = 0.000430). The ratio in first three groups is about 7-7.5:1 (greater then Mediteran-4-5:1, but lower then Western Diet-10-20:1). There is no statistically significant difference between first three stages (p > 0.05) and stage 4 and control group (p = 0.172388). Omega-6/omega-3 ratio is connected with development of neovascular ARMD. Decreased ratio protects against neovascular ARMD. On the contrary, GA seems to be connected with prolonged sunlight exposure (the ratio is about 6:1). It is good to know that changing nutrition habits someone can prevent development of severe neovascular form of ARMD because intravitreal anti-VEGF therapy limitations.     

The role of the spectral domain ocular coherence tomography in detection of age-related macular degeneration

Age-related macular degeneration (ARMD) is one of the most common causes of the vision loss and blindness in developed countries. Among other harmful effects, exposure to the UV radiation is the most prominent factor for the development of the disorder. Using the method of SD OCT (Spectral Domain Ocular Coherence Tomography) we performed measurement of the neurosensory retinal thickness of 19 eyes of low vision patients from the population of Primorsko-Goranska County of Republic of Croatia, with dry form of the terminal macular degeneration. These results we compared with control measurements performed on 28 eyes of healthy, normal vision subjects from same County. We determined following parameters: central foveal thickness (CFT), macular volume (MV) and mean foveal thickness (MFT) in the both groups. Results showed statistically significant reduction of CFT in the group of normal vision female patients when compared to males, while any significant difference of CFT between total groups of normal vision individuals and low vision patients was not detected. Furthermore, we noticed statistically significant (p < 0.000001) decrease of the MV in the group of the low vision patients in comparison to healthy subjects and statistically significant (p < 0.000001) reduction of the MFT of the low vision patients when compared to normal vision individuals. In our study we detected the absence of any significant difference of the CFT between healthy and low vision population, what looks like controversial finding, because neurosensory retina in the ARMD is thin and atrophic, but on the other side it is known that fixation point in low vision patients is translocated from the damaged fovea to extrafoveal region, usually above the fovea, where neurosensory retina is of the normal thickness, but with the less sensitivity. Furthermore, our results suggest possible connection of higher incidence of ARMD with lower CFT in females. Owing to the thicker neurosensory retina in males and better protection, damaging effect of the UV irradiation, which is the proven factor of ARMD development, is smaller. From the evolutionary point of view it is possible that males in all vertebrates have more resistant macula because during the evolutionary process they have spent much more time outside in the sunlight than females.     

Discovery of highly potent, nonsteroidal 17β-hydroxysteroid dehydrogenase type 1 inhibitors by virtual high-throughput screening

17β-Hydroxysteroid dehydrogenase type 1 (17β-HSD1) catalyzes the formation of the potent proliferation-stimulating hormone estradiol, and it is thus involved in the development of hormone-dependent breast cancer. Due to its high substrate specificity and the known relationships between its overexpression and disease incidence, 17β-HSD1 is considered an attractive target for drug development. Here, we have used structure-based virtual high-throughput screening to successfully identify potent nonsteroidal 17β-HSD1 inhibitors. Computational screening of a drug-like database containing 13 million compounds identified hits with a 2-benzylidenebenzofuran-3(2H)-one scaffold that we show to be highly potent 17β-HSD1 inhibitors. The most potent in the series, compound 1, showed an IC(50) of 45nM in our 17β-HSD1 inhibition assay, and also showed good selectivity for 17β-HSD1 over 17β-HSD2.     

Evaluation of a hydrogel-fiber composite for ACL tissue engineering

The anterior cruciate ligament (ACL) is necessary for normal knee stability and movement. Unfortunately the ACL is also the most frequently injured ligament of the knee with severe disruptions requiring surgical intervention. In response to this, tissue engineering has emerged as an option for ACL replacement and repair. In this study we present a novel hydrogel-fibrous scaffold as a potential option for ACL replacement. The scaffold was composed of PLLA fibers, in a previously evaluated braid-twist structure, combined with a polyethylene glycol diacrylate (PEGDA) hydrogel to improve viscoelastic properties. Both hydrogel concentration (10%, 15%, and 20%) and amount of hydrogel (soaking the fibrous scaffold in hydrogel solution or encasing the scaffold in a block of hydrogel) were evaluated. It was found that the braid-twist scaffold had a greater porosity and larger number of pores above 100 μm than braided scaffolds with the same braiding angle. After testing for their effects on swelling, fiber degradation, and protein release, as well as viscoelastic and tensile testing (when combined with fibrous scaffolds), it was found that the composite scaffold soaked in 10% hydrogel had the best chemical release and mechanical properties. The optimized structure behaved similarly to natural ligament in tension with the addition of the hydrogel decreasing the ultimate tensile stress (UTS), but the UTS was still comparable to natural ACL. In addition, cellular studies showed that the hydrogel-PLLA fiber composite supported fibroblast growth.     

The rational strategies for detecting developmental dysplasia of the hip at the age of 4-6 months old infants: a prospective study

Using ultrasound in evaluation of infant's hip development can reduce surgical procedures, hospitalization and late presentation of developmental dysplasia of the hip (DDH). The increasing incidence of DDH after ultrasound examination is observed and published by many authors. In a prospective study, radiograph of every single ultrasonographic positive hip in infants older than three months, was taken and analyzed in order to see whether it affects infants splintage rate in treating DDH. In a period of 30 months, clinical and simple static ultrasonographic examinations according to Graf were performed on 1430 consecutive infant hips in patients aged between 4 and 6 months. Sonographic positive hips were radiographed and acetabular index (AI) values on simple AP radiographs were analyzed. The sonographic DDH incidence was 51.75 per 1000 hips (51.75 per thousand). After X-ray examination of all 74 ultrasonographic positive hips, only 44 remained abnormal and required treatment indicating a true DDH incidence of 30.77 per 1000 hips (30.77 per thousand). The difference in incidence per ultrasonographic and X-ray positive hips is statistically significant p < 0.01 (t = 5,536). The rational approach in detection of DDH in a child more than 3 months old is to do radiographic assessment of every sonographic positive hip.     

Inferring gene function from evolutionary change in signatures of translation efficiency

Background

The genetic code is redundant, meaning that most amino acids can be encoded by more than one codon. Highly expressed genes tend to use optimal codons to increase the accuracy and speed of translation. Thus, codon usage biases provide a signature of the relative expression levels of genes, which can, uniquely, be quantified across the domains of life.

Results

Here we describe a general statistical framework to exploit this phenomenon and to systematically associate genes with environments and phenotypic traits through changes in codon adaptation. By inferring evolutionary signatures of translation efficiency in 911 bacterial and archaeal genomes while controlling for confounding effects of phylogeny and inter-correlated phenotypes, we linked 187 gene families to 24 diverse phenotypic traits. A series of experiments in Escherichia coli revealed that 13 of 15, 19 of 23, and 3 of 6 gene families with changes in codon adaptation in aerotolerant, thermophilic, or halophilic microbes. Respectively, confer specific resistance to, respectively, hydrogen peroxide, heat, and high salinity. Further, we demonstrate experimentally that changes in codon optimality alone are sufficient to enhance stress resistance. Finally, we present evidence that multiple genes with altered codon optimality in aerobes confer oxidative stress resistance by controlling the levels of iron and NAD(P)H.

Conclusions

Taken together, these results provide experimental evidence for a widespread connection between changes in translation efficiency and phenotypic adaptation. As the number of sequenced genomes increases, this novel genomic context method for linking genes to phenotypes based on sequence alone will become increasingly useful.