A computational study of atomic oxygen-doped silicon carbide nanotubes

We investigated the properties of atomic oxygen-doped (O-doped) models of representative (6,0) and (4,4) silicon carbide nanotubes (SiCNTs) by density functional theory (DFT) calculations of isotropic and anisotropic chemical shielding (CS) parameters of Si-29, O-17 and C-13 atoms for the optimized structures. The calculated parameters indicated the effects of O-doping on the electronic environments of the first neighboring atoms of the doped sites. Comparing the results of the zigzag and armchair models also indicated that the latter model detects more effects of the O-doping than the former one.     

Establishing Embryonic Mouse Neural Stem Cell Culture Using the Neurosphere Assay

In mammalians, stem cells acts as a source of undifferentiated cells to maintain cell genesis and renewal in different tissues and organs during the life span of the animal. They can potentially replace cells that are lost in the aging process or in the process of injury and disease. The existence of neural stem cells (NSCs) was first described by Reynolds and Weiss (1992) in the adult mammalian central nervous system (CNS) using a novel serum‐free culture system, the neurosphere assay (NSA). Using this assay, it is also feasible to isolate and expand NSCs from different regions of the embryonic CNS. These in vitro expanded NSCs are multipotent and can give rise to the three major cell types of the CNS. While the NSA seems relatively simple to perform, attention to the procedures demonstrated here is required in order to achieve reliable and consistent results. This video practically demonstrates NSA to generate and expand NSCs from embryonic day 14-mouse brain tissue and provides technical details so one can achieve reproducible neurosphere cultures. The procedure includes harvesting E14 mouse embryos, brain microdissection to harvest the ganglionic eminences, dissociation of the harvested tissue in NSC medium to gain a single cell suspension, and finally plating cells in NSA culture. After 5-7 days in culture, the resulting primary neurospheres are passaged to further expand the number of the NSCs for future experiments.Download video file.^{(69M, mov)}     

Proteomic analysis of the Mexican lime tree response to "Candidatus Phytoplasma aurantifolia" infection

"Candidatus Phytoplasma aurantifolia" is the causative agent of witches' broom disease in the Mexican lime tree (Citrus aurantifolia L.), and is responsible for major tree losses in Southern Iran and Oman. The pathogen is strictly biotrophic, and, therefore, completely dependent on living host cells for its survival. The molecular basis of compatibility and disease development in this system is poorly understood. We applied a proteomics approach to analyse gene expression in Mexican limes infected with "Ca. Phytoplasma aurantifolia". Leaf samples were collected from healthy and infected plants and were analysed using 2-DE coupled with MS. Among 800 leaf proteins that were detected reproducibly in eight biological replicates of healthy and eight biological replicates of infected plants, 55 showed a significant response to the disease. MS resulted in identification of 39 regulated proteins, which included proteins that were involved in oxidative stress defence, photosynthesis, metabolism, and the stress response. Our results provide the first proteomic view of the molecular basis of the infection process and identify genes that could help inhibit the effects of the pathogen.     

Purification of immature neuronal cells from neural stem cell progeny

Large-scale proliferation and multi-lineage differentiation capabilities make neural stem cells (NSCs) a promising renewable source of cells for therapeutic applications. However, the practical application for neuronal cell replacement is limited by heterogeneity of NSC progeny, relatively low yield of neurons, predominance of astrocytes, poor survival of donor cells following transplantation and the potential for uncontrolled proliferation of precursor cells. To address these impediments, we have developed a method for the generation of highly enriched immature neurons from murine NSC progeny. Adaptation of the standard differentiation procedure in concert with flow cytometry selection, using scattered light and positive fluorescent light selection based on cell surface antibody binding, provided a near pure (97%) immature neuron population. Using the purified neurons, we screened a panel of growth factors and found that bone morphogenetic protein-4 (BMP-4) demonstrated a strong survival effect on the cells in vitro, and enhanced their functional maturity. This effect was maintained following transplantation into the adult mouse striatum where we observed a 2-fold increase in the survival of the implanted cells and a 3-fold increase in NeuN expression. Additionally, based on the neural-colony forming cell assay (N-CFCA), we noted a 64 fold reduction of the bona fide NSC frequency in neuronal cell population and that implanted donor cells showed no signs of excessive or uncontrolled proliferation. The ability to provide defined neural cell populations from renewable sources such as NSC may find application for cell replacement therapies in the central nervous system.     

Bioluminescence regenerative cycle (BRC) system: theoretical considerations for nucleic acid quantification assays

A novel application of bioluminescence for nucleic acid quantification, the bioluminescence regenerative cycle (BRC), is described in theoretical terms and supported by preliminary experimental data. In the BRC system, pyrophosphate (PPi) molecules are released during biopolymerization and are counted and correlated to DNA copy number. The enzymes ATP-sulfurylase and firefly luciferase are employed to generate photons quantitatively from PPi. Enzymatic unity-gain positive feedback is implemented to amplify photon generation and to compensate for decay in light intensity by self-regulation. The cumulative total of photons can be orders of magnitude higher than in typical chemiluminescent processes. A system level theoretical model is developed, taking into account the kinetics of the regenerative cycle, contamination, and detector noise. Data and simulations show that the photon generation process achieves steady state for the time range of experimental measurements. Based on chain reaction theory, computations show that BRC is very sensitive to variations in the efficiencies of the chemical reactions involved and less sensitive to variations in the quantum yield of the process. We show that BRC can detect attomolar quantities of DNA (10(-18) mol), and that the useful dynamic range is five orders of magnitude. Sensitivity is not constrained by detector performance but rather by background bioluminescence caused by contamination by either PPi or ATP (adenosine triphosphate).     

Hyperprolactinemia after laparoscopic ovarian drilling: An unknown phenomenon

Background  

The effects of ovarian drilling on the serum levels of gonadotropins and androgens have been studied previously. The aim of this study is to evaluate the effects of ovarian drilling on the serum prolactin levels and its relation to ovulation in women with polycystic ovary syndrome.     

Modulation of the sensitivity of FimB recombination to branched-chain amino acids and alanine in Escherichia coli K-12

Phase variation of type 1 fimbriae of Escherichia coli requires the site-specific recombination of a short invertible element. Inversion is catalyzed by FimB (switching in either direction) or FimE (inversion mainly from on to off) and is influenced by auxiliary factors integration host factor (IHF) and leucine-responsive regulatory protein (Lrp). These proteins bind to sites (IHF site II and Lrp sites 1 and 2) within the invertible element to stimulate recombination, presumably by bending the DNA to enhance synapses. Interaction of Lrp with a third site (site 3) cooperatively with sites 1 and 2 (termed complex 1) impedes recombination. Inversion is stimulated by the branched-chain amino acids (particularly leucine) and alanine, and according to a current model, the amino acids promote the selective loss of Lrp from site 3 (complex 2). Here we show that the central portion of the fim invertible element, situated between Lrp site 3 and IHF site II, is dispensable for FimB recombination but that this region is also required for full amino acid stimulation of inversion. Further work reveals that the region is likely to contain multiple regulatory elements. Lrp site 3 is shown to bind the regulatory protein with low affinity, and a mutation that enhances binding to this element is found both to diminish the stimulatory effects of IVLA on FimB recombination and to inhibit recombination in the absence of the amino acids. The results obtained emphasize the importance of Lrp site 3 as a control element but also highlight the complexity of the regulatory system that affects this site.     

Genetic characterization of high-level gentamicin-resistant strains of Enterococcus faecalis in Iran

The prevalence of resistance to high levels of gentamicin among 182 isolates of Enterococcus faecalis from 2 Iranian hospitals was 42%. Gentamicin resistance was associated with conjugative plasmids (>70 kb) in most strains. Fingerprinting using EcoRI and HindIII showed genetic variation among these plasmids and gave evidence of nosocomial outbreaks and persistence of infection in different wards of the study hospitals, as well as transfer of plasmids between genetically diverse isolates. Using EcoRI, hospital-based specific plasmid fingerprints were detected for the isolates that had previously proved to be unrelated by multilocus enzyme electrophoresis, suggesting the persistence of related plasmids at each hospital, though minor changes in these related plasmids could be detected with HindIII.     

Novel anti-viability ceramide analogs: Design,synthesis, and structure–activity relationship studies of substituted (S)-2-(benzylideneamino)-3-hydroxy-N-tetradecylpropanamides

A group of novel l-serinamides, substituted (S)-2-(benzylideneamino)-3-hydroxy-N-tetradecylpropanamides (3a–o) and substituted (S)-2-(benzylamino)-3-hydroxy-N-tetradecyl propanamides (4c, 4i, 4l, and 4o), were synthesized as potential anti-tumor lead compounds. In vitro cell viability assay results indicate treatment with 3a–o compounds resulted in significant inhibition of cell viability in the chemoresistant breast cancer cell line, MCF-7TN-R. Compounds 3i and 3l, both ortho-substituted analogs, show the greatest efficacy with IC₅₀ values of 10.3 μM and 12.5 μM, respectively. The SAR analysis indicate that the imine functional group of 3a–o is critical for the cellular anti-viability effect, and the partial atomic charge (PAC) value of imine C atom is a valuable structural parameter for predicting the activity of these ceramide analogs.