Drosophila Eph receptor guides specific axon branches of mushroom body neurons

The conserved Eph receptors and their Ephrin ligands regulate a number of developmental processes, including axon guidance. In contrast to the large vertebrate Eph/Ephrin family, Drosophila has a single Eph receptor and a single Ephrin ligand, both of which are expressed within the developing nervous system. Here, we show that Eph and Ephrin can act as a functional receptor-ligand pair in vivo. Surprisingly, and in contrast to previous results using RNA-interference techniques, embryos completely lacking Eph function show no obvious axon guidance defects. However, Eph/Ephrin signaling is required for proper development of the mushroom body. In wild type, mushroom body neurons bifurcate and extend distinct branches to different target areas. In Eph mutants, these neurons bifurcate normally, but in many cases the dorsal branch fails to project to its appropriate target area. Thus, Eph/Ephrin signaling acts to guide a subset of mushroom body branches to their correct synaptic targets.     

Novel thienopyrrole glycogen phosphorylase inhibitors: synthesis, in vitro SAR and crystallographic studies

Two series of novel thienopyrrole inhibitors of recombinant human liver glycogen phosphorylase a (GPa) which are effective in reducing glucose output from rat hepatocytes are described. Representative compounds have been shown to bind at the dimer interface site of the rabbit muscle enzyme by X-ray crystallography.     

Tri-substituted triazoles as potent non-nucleoside inhibitors of the HIV-1 reverse transcriptase

A new series of 1,2,4-triazoles was synthesized and tested against several NNRTI-resistant HIV-1 isolates. Several of these compounds exhibited potent antiviral activities against efavirenz- and nevirapine-resistant viruses, containing K103N and/or Y181C mutations or Y188L mutation. Triazoles were first synthesized from commercially available substituted phenylthiosemicarbazides, then from isothiocyanates, and later by condensing the desired substituted anilines with thiosemicarbazones.     

Feedback hypothesis and the effects of altered gravity on formation and function of gravireceptors of mollusks and fish

Popular hypothesis based on the idea of simple feedback mechanism that correlates gravity level and weight of test mass cannot explain the variety of the effects of altered gravity on development and function of gravireceptors. The reaction of organisms to the change of gravity depends on the gravisensitivity of the physical and chemical processes corresponding to specific phases of development and may have no relation to any feedback mechanisms of compensation of altered weight of the test mass. The present work analyzes the hypothesis of feedback and shows the ambiguity of possible effects of the altered gravity on formation and function of gravireceptors basing on the data from mollusks and fish.     

Bap31 enhances the endoplasmic reticulum export and quality control of human class I MHC molecules

The assembly of class I MHC molecules and their export from the endoplasmic reticulum (ER) is governed by chaperones and accessory proteins. We present evidence that the putative cargo receptor protein Bap31 participates in the transport and the quality control of human class I molecules. Transfection of the human adenocarcinoma cell line HeLa with yellow fluorescent protein-Bap31 chimeras increased surface levels of class I in a dose-dependent manner, by as much as 3.7-fold. The increase in surface class I resulted from an increase in the rate of export of newly synthesized class I molecules to the cell surface and from an increase in the stability of the exported molecules. We propose that Bap31 performs quality control on class I molecules in two distinct phases: first, by exporting peptide-loaded class I molecules to the ER/Golgi intermediate compartment, and second, by retrieving class I molecules that have lost peptides in the acidic post-ER environment. This function of Bap31 is conditional or redundant, because we find that Bap31 deficiency does not reduce surface class I levels. Overexpression of the Bap31 homolog, Bap29, decreases surface class levels in HeLa, indicating that it does not substitute for Bap31.     

Entropic folding pathway of human epidermal growth factor explored by disulfide scrambling and amplified collective motion simulations

Epidermal growth factor (EGF) regulates cell proliferation and differentiation by binding to the EGF receptor (EGFR) extra-cellular domains. Human EGF is a small, single-chain protein comprising three distinct loops (A, B, and C), which are connected by three disulfide bridges (Cys6-Cys20, Cys14-Cys31, and Cys33-Cys42). These disulfide bridges are essential for structural stability and biological activity. EGF was extensively studied by disulfide scrambling, an experimental technique for the conformational entrapment of intermediate states, which allows us to study the folding pathway of proteins containing disulfide bonds. The experimental results showed that there is a major 2-disulfide intermediate (denoted EGF-II) and that the native disulfide bonding pattern is less prevalent in one of the mutants. In this article, we investigated for the first time the solution conformations of wild-type EGF, EGF-II, and the mutant S9C through extensive molecular dynamics (MD) simulations in water using both the standard MD technique and a recently developed amplified-collective-motion (ACM) sampling method. Compared to standard MD simulations, we achieved a much more enhanced sampling by the ACM simulations, and the structures were sufficiently relaxed to estimate configurational entropies. The simulation results suggest a predominantly entropic folding pathway governed by the disorder of three functional loop regions. Although EGF-II exhibits two native disulfide bonds (Cys14-Cys31 and Cys33- Cys42), its large configurational entropy inhibits a direct transition to the native structure in the folding process. When Ser9 is mutated into Cys, a non-native disulfide bridge Cys9- Cys20 is slightly more favorable than the native Cys6-Cys20 because a less constrained N-terminus affords larger entropy. Isomers that are functionally less active also exhibit a more localized dynamics of the functional loop regions, which may suggest a possible mechanism for the modulation of EGF activity.     

Stage-Specific Effects of Androgens and Estradiol-17beta on the Development of Late Primary and Early Secondary Ovarian Follicles of Coho Salmon (Oncorhynchus kisutch) In Vitro

An in vitro system was used to analyze the effects of sex steroids on the development of primary (late perinucleolar stage) and early secondary, previtellogenic (early cortical alveolus stage) ovarian follicles of coho salmon cultured for up to 21 days. Late perinucleolar-stage follicles increased significantly in size after 7 days of treatment with low concentrations of 11-ketotestosterone (11-KT), a nonaromatizable androgen. An androgen receptor antagonist (flutamide) inhibited this growth-promoting effect, and the highest concentration resulted in atresia of follicles, implicating androgens as survival factors at this stage. Testosterone (T) was less effective than 11-KT in promoting growth, but blocking aromatization with exemestane resulted in a growth response similar to that of 11-KT. Estradiol-17beta (E2) had no effect on growth at this stage. After 21 days of culture, E2 was the most potent steroid in increasing the number of follicles containing cortical alveoli and the number of cortical alveoli within those follicles. At the early cortical alveolus stage, low doses of E2 promoted growth and strongly stimulated synthesis of cortical alveoli, actions that were inhibited by an estrogen receptor antagonist (tamoxifen). 11-KT displayed moderate growth-promoting effects, and 11-KT and T stimulated moderate to substantial increases in abundance of cortical alveoli. This study shows that the predominant role of androgens is the promotion of growth of late perinucleolar-stage follicles, while E2 stimulates both the growth and accumulation of cortical alveoli in early cortical alveolus-stage follicles.     

Nanoparticle assembly for sensitive DNA detection using SERRS

SERRS (surface-enhanced resonance Raman scattering) is a vibrational technique, whereby a relatively weak Raman scattering effect is enhanced through the use of a visible chromophore and a roughened metal surface. The direct analysis of DNA by SERRS requires the modification of a nucleic acid sequence to incorporate a chromophore, and adsorption of the modified sequence on to a roughened metal surface. Aggregated metallic nanoparticles are commonly used in the analysis of dye-labelled DNA by SERRS, allowing for detection levels that rival those gained from standard fluorescence-based techniques. In the present paper, we report on how SERRS can be exploited for the analysis of clinically relevant DNA samples. We also report on the ability of nanoparticles to aggregate as the result of a biologically significant event, as opposed to the use of an external charge-modifying agent. The self-assembly of metallic nanoparticles is shown to be a promising new technique in the move towards extremely sensitive methods of DNA analysis by SERRS.     

An Alternative Ionic Conductivity Mechanism for Plastic Crystalline Salt–Lithium Salt Electrolyte Mixtures

The phase behavior and ionic conductivity of tetraethylammonium bis(trifluoromethane‐sulfonyl)imide (Et₄NTFSI) salt mixtures with LiTFSI have been examined. In addition, the phase behavior and crystal structure of neat LiTFSI is also reported. Two (1‐x) Et₄NTFSI‐(x) LiTFSI (x = 0.50 and 0.67, where x is the mol fraction) mixed‐salt crystalline phases form. Large variations in ionic conductivity are observed; these are attributed to solid‐solid phase transitions of the neat Et₄NTFSI salt creating disordered plastic crystalline phases and the formation of a low‐melting eutectic composition between the neat Et₄NTFSI salt and the 1/1 Et₄NTFSI/LiTFSI (x = 0.50) phase. Although Et₄NTFSI and LiTFSI melt at 102 and 234 °C, respectively, the two salts form a eutectic system with a melting temperature of 32 °C. Based upon the findings reported, a new conductivity mechanism is proposed for plastic crystalline salt‐lithium salt electrolytes which is not ascribed to solid‐state diffusion/conduction.     

Common variants at 9p21 and 8q22 are associated with increased susceptibility to optic nerve degeneration in glaucoma

Optic nerve degeneration caused by glaucoma is a leading cause of blindness worldwide. Patients affected by the normal-pressure form of glaucoma are more likely to harbor risk alleles for glaucoma-related optic nerve disease. We have performed a meta-analysis of two independent genome-wide association studies for primary open angle glaucoma (POAG) followed by a normal-pressure glaucoma (NPG, defined by intraocular pressure (IOP) less than 22 mmHg) subgroup analysis. The single-nucleotide polymorphisms that showed the most significant associations were tested for association with a second form of glaucoma, exfoliation-syndrome glaucoma. The overall meta-analysis of the GLAUGEN and NEIGHBOR dataset results (3,146 cases and 3,487 controls) identified significant associations between two loci and POAG: the CDKN2BAS region on 9p21 (rs2157719 [G], OR = 0.69 [95%CI 0.63–0.75], p = 1.86×10⁻¹⁸), and the SIX1/SIX6 region on chromosome 14q23 (rs10483727 [A], OR = 1.32 [95%CI 1.21–1.43], p = 3.87×10⁻¹¹). In sub-group analysis two loci were significantly associated with NPG: 9p21 containing the CDKN2BAS gene (rs2157719 [G], OR = 0.58 [95% CI 0.50–0.67], p = 1.17×10⁻¹²) and a probable regulatory region on 8q22 (rs284489 [G], OR = 0.62 [95% CI 0.53–0.72], p = 8.88×10⁻¹⁰). Both NPG loci were also nominally associated with a second type of glaucoma, exfoliation syndrome glaucoma (rs2157719 [G], OR = 0.59 [95% CI 0.41–0.87], p = 0.004 and rs284489 [G], OR = 0.76 [95% CI 0.54–1.06], p = 0.021), suggesting that these loci might contribute more generally to optic nerve degeneration in glaucoma. Because both loci influence transforming growth factor beta (TGF-beta) signaling, we performed a genomic pathway analysis that showed an association between the TGF-beta pathway and NPG (permuted p = 0.009). These results suggest that neuro-protective therapies targeting TGF-beta signaling could be effective for multiple forms of glaucoma.