Melanin‐based coloration covaries with fluctuating asymmetry,nutritional state and physiological stress response in common snipe

Adaptative significance of melanin‐based coloration in birds remains poorly recognized. It has been suggested that genes responsible for melanin synthesis may have pleiotropic effect on several physiological and behavioural functions, including immune defence. For this reason, we could expect that the expression of melanin‐based plumage coloration should covary with different condition‐related phenotypic traits via regulation of pathogen/parasite resistance. The aim of this study was to test this hypothesis in common snipe Gallinago gallinago, a species that exhibits conspicuous variation in the black eumelanism of underwing plumage. The study was conducted in central Poland, where common snipe were captured during autumn migration. We found that after accounting for the effects of age, sex and date of capture, underwing coloration correlated with nutritional state of snipes, as more extensively melanised individuals had higher plasma concentrations of triglycerides, total protein and albumin. Dark underwing coloration was also associated with lower heterophil/lymphocyte (H/L) ratio, suggesting better resistance of eumelanic individuals to physiological stress. Finally, adult males with darker underwings had lower asymmetry in wing shape (wingtip convexity), which indicated their higher developmental stability. In conclusion, melanin‐based coloration may be considered an honest indicator of phenotypic quality in common snipe.     

Micelle‐enhanced spectrofluorimetric method for determination of sitagliptin and identification of potential alkaline degradation products using LC‐MS

A novel, quick, simple and highly sensitive spectrofluorimetric method was developed and validated for the determination of sitagliptin (SG) in its pharmaceutical formulations. The proposed method is based on investigation of the fluorescence spectral behavior of sitagliptin in an SDS micellar system. In an aqueous solution of phosphate buffer pH 4.0, the fluorescence intensity of SG in the presence of SDS was greatly enhanced, by 200%, i.e. twofold enhancement. The fluorescence intensity of SG was measured at 300 nm after excitation at 270 nm. The method showed good linearity in the range 0.03–10.0 µg/mL with a good correlation coefficient (r = 0.9998). The limits of detection and quantitation values were 5.31 and 16.1 ng/mL, respectively. The proposed method was successfully applied to the analysis of SG in its single and co‐formulated commercial tablets; the results were in good agreement with those obtained using a reference method. Application of the proposed method was extended to stability studies of SG after exposure to different forced degradation conditions according to the ICH guidelines, such as acidic, alkaline, thermal, photo‐ and oxidative stress. The chemical structure of certain potential degradation products (DPs) were investigated using LC‐MS. Copyright © 2013 John Wiley & Sons, Ltd.     

Synaptically Released Matrix Metalloproteinase Activity in Control of Structural Plasticity and the Cell Surface Distribution of GluA1-AMPA Receptors

Synapses are particularly prone to dynamic alterations and thus play a major role in neuronal plasticity. Dynamic excitatory synapses are located at the membranous neuronal protrusions called dendritic spines. The ability to change synaptic connections involves both alterations at the morphological level and changes in postsynaptic receptor composition. We report that endogenous matrix metalloproteinase (MMP) activity promotes the structural and functional plasticity of local synapses by its effect on glutamate receptor mobility and content. We used live imaging of cultured hippocampal neurons and quantitative morphological analysis to show that chemical long-term potentiation (cLTP) induces the permanent enlargement of a subset of small dendritic spines in an MMP-dependent manner. We also used a superresolution microscopy approach and found that spine expansion induced by cLTP was accompanied by MMP-dependent immobilization and synaptic accumulation as well as the clustering of GluA1-containing AMPA receptors. Altogether, our results reveal novel molecular and cellular mechanisms of synaptic plasticity.     

Use of Label-free Optical Biosensors to Detect Modulation of Potassium Channels by G-protein Coupled Receptors

Ion channels control the electrical properties of neurons and other excitable cell types by selectively allowing ions to flow through the plasma membrane¹. To regulate neuronal excitability, the biophysical properties of ion channels are modified by signaling proteins and molecules, which often bind to the channels themselves to form a heteromeric channel complex^2,3. Traditional assays examining the interaction between channels and regulatory proteins require exogenous labels that can potentially alter the protein''s behavior and decrease the physiological relevance of the target, while providing little information on the time course of interactions in living cells. Optical biosensors, such as the X-BODY Biosciences BIND Scanner system, use a novel label-free technology, resonance wavelength grating (RWG) optical biosensors, to detect changes in resonant reflected light near the biosensor. This assay allows the detection of the relative change in mass within the bottom portion of living cells adherent to the biosensor surface resulting from ligand induced changes in cell adhesion and spreading, toxicity, proliferation, and changes in protein-protein interactions near the plasma membrane. RWG optical biosensors have been used to detect changes in mass near the plasma membrane of cells following activation of G protein-coupled receptors (GPCRs), receptor tyrosine kinases, and other cell surface receptors. Ligand-induced changes in ion channel-protein interactions can also be studied using this assay. In this paper, we will describe the experimental procedure used to detect the modulation of Slack-B sodium-activated potassium (K_Na) channels by GPCRs.     

Effects of Fusarium culmorum head blight on mycotoxin accumulation and yield traits in barley doubled haploids

The susceptibility of barley doubled haploids (DH) to Fusarium head blight (FHB) was investigated. Heads of 24 DH lines (11 two-rowed and 13 six-rowed) derived from F₁ Maresi (two-rowed) × Pomo (six-rowed) hybrids were inoculated with a conidial suspension of the single isolate IPO348-01 of Fusarium culmorum. The experiment was carried out in three consecutive years (1996–98) in one location. The number of kernels per ear, 1000-kernel weight and kernel weight per ear were recorded in inoculated and control plots. In the infected kernels nivalenol (NIV) content and deoxynivalenol (DON) content were determined. The effects of genotype, year and genotype-year interaction on reduction of yield traits were significant. For mycotoxin content only genotype and year effects were found to be important. The average NIV concentration in kernels of inoculated lines ranged from 0.15 mg/kg in the two-rowed line MP7 to 6.36 mg/kg in the six-rowed line MP113. A low accumulation of DON was observed in the studied population (from 0.01 to 0.20 mg/kg). Generally, no significant differences in mycotoxin content were found between two-rowed and six-rowed genotypes. The line MP7 was found to be superior — with the lowest mycotoxin accumulation, and reduction in yield traits. Environmental conditions (years) affected DON and NIV level in kernels; however, the tendency to a lower or higher accumulation of mycotoxin in individual lines was stable over the years.     

The influence of coumestrol,zearalenone, and genistein administration on insulin receptors and insulin secretion in ovariectomized rats

The influence of phytoestrogens (genistein and coumestrol) and mycoestrogen (zearalenone) on insulin secretion, liver insulin receptors and some aspects of lipid and carbohydrate metabolism were investigated in this study. Ovariectomized rats were injected s.c. with the above mentioned compounds in the amount of 1 mg for three days. Coumestrol and zearalenone caused a significant increase in uterus weight, similar to the effects observed after estrone action, while this effect was not observed after the genistein injection. Blood insulin level was not changed after phyto- or mycoestrogen treatment. However, coumestrol and genistein significantly decreased the binding capacity of liver insulin receptors. These changes corresponded with alterations in glucose and free fatty acids profiles in blood, as well as with glycogen content in liver. The effects observed after genistein and coumestrol injections differed from those noticed in rats treated with zearalenone or estrone. On the basis of these results we conclude that metabolic effects of high doses of coumestrol and genistein in ovariectomized rats are partly mediated by changes in insulin sensitivity of the liver and that the action of plant estrogens on metabolism is, at least to the some degree, independent of their estrogen activity.     

Design and visualization of second‐generation cyanoisoindole‐based fluorescent strigolactone analogs

Strigolactones (SLs) are a family of terpenoid allelochemicals that were recognized as plant hormones only a decade ago. They influence a myriad of both above‐ and below‐ground developmental processes, and are an important survival strategy for plants in nutrient‐deprived soils. A rapidly emerging approach to gain knowledge on hormone signaling is the use of traceable analogs. A unique class of labeled SL analogs was constructed, in which the original tricyclic lactone moiety of natural SLs is replaced by a fluorescent cyanoisoindole ring system. Biological evaluation as parasitic seed germination stimulant and hypocotyl elongation repressor proved the potency of the cyanoisoindole strigolactone analogs (CISAs) to be comparable to the commonly accepted standard GR24. Additionally, via a SMXL6 protein degradation assay, we provided molecular evidence that the compounds elicit SL‐like responses through the natural signaling cascade. All CISAs were shown to exhibit fluorescent properties, and the high quantum yield and Stokes shift of the pyrroloindole derivative CISA‐7 also enabled in vivo visualization in plants. In contrast to the previously reported fluorescent analogs, CISA‐7 displays a large similarity in shape and structure with natural SLs, which renders the analog a promising tracer to investigate the spatiotemporal distribution of SLs in plants and fungi.     

Cycloheximide or puromycin can substitute for PDGF in inducing cellular DNA synthesis in quiescent 3T3 cells

A brief exposure of quiescent (Go) Swiss 3T3 mouse fibroblasts to inhibitors of protein synthesis can replace platelet-derived growth factor in the stimulation of cellular DNA synthesis. When 3T3 cells, after a 6 hr exposure to either cycloheximide or puromycin, are incubated with platelet-poor plasma, a significant percentage of cells enters DNA synthesis. Either inhibition of protein synthesis, or platelet poor plasma by themselves are totally ineffective. A possible mechanism by which inhibitors of protein synthesis may initiate cell cycle progression is through the activation of the c-myc gene.