1,309 research outputs found
Nonadditive Genetic Effects in Animal Behavior
Heritabilities, commonly used to predict evolutionary potential, are notoriously low for behaviors. Apart from strong contributions of environmental variance in reducing heritabilities, the additive genetic components can be very low, especially when they are camouflaged by nonadditive genetic effects. We first report the heritabilities of courtship traits in founderâflush and control populations of the housefly (Musca domestica L.). We estimated the heritability of each male and female display through the regression of the courtships involving daughters and sons (with randomly selected mates) onto the âmidparentalâ courtship values of their parents. Overall, the average heritability was significantly higher for the parentâdaughter assays than for the parentâson assays. We attributed the low (even negative) heritabilities to genotypeâbyâenvironment interactions whereby the maleâs behavior is influenced by the âenvironmentâ of his mating partnerâs preferences for the display, generating epistasis through indirect genetic effects. Moreover, bottlenecked lines had up to 800% of the heritability of the controls, suggesting âconversionâ of additive genetic variance from nonadditive components. Second, we used lineâcross assays on separate populations that had been selected for divergence in mating behavior to identify dominance and epistasis through heterosis and outbreeding depression in courtship. Finally, our literature review confirms the prevalence of such low heritabilities (i.e., a conservative mean of 0.38) and nonadditive genetics in other behavioral repertoires (64% of the studies). We conclude that animal behavior is especially prone to the gamut of quantitative genetic complexities that can result in negative heritabilities, negative selection responses, inbreeding depression, conversion, heterosis, and outbreeding depression
NF-kB functions in synaptic signaling and behavior
Ca^(2+)-regulated gene transcription is essential to diverse physiological processes, including the adaptive plasticity associated with learning. We found that basal synaptic input activates the NF-kB transcription factor by a pathway requiring the Ca^(2+)/calmodulin-dependent kinase CaMKII and local submembranous Ca^(2+) elevation. The p65:p50 NF-kB form is selectively localized at synapses; p65-deficient mice have no detectable synaptic NF-kB. Activated NF-kB moves to the nucleus and could directly transmute synaptic signals into altered gene expression. Mice lacking p65 show a selective learning deficit in the spatial version of the radial arm maze. These observations suggest that long-term changes to adult neuronal function caused by synaptic stimulation can be regulated by NF-kB nuclear translocation and gene activation
Experimental Fracture Model versus Osteotomy Model in Metacarpal Bone Plate Fixation
Introduction. Osteotomy or fracture models can be used to evaluate mechanical properties of fixation techniques of the hand skeleton in vitro. Although many studies make use of osteotomy models, fracture models simulate the clinical situation more realistically. This study investigates monocortical and bicortical plate fixation on metacarpal bones considering both aforementioned models to decide which method is best suited to test fixation techniques. Methods. Porcine metacarpal bones (n = 40) were randomized into 4 groups. In groups I and II bones were fractured with a modified 3-point bending test. The intact bones represented a further control group to which the other groups after fixation were compared. In groups III and IV a standard osteotomy was carried out. Bones were fixated with plates monocortically (group I, III) and bicortically (group II, IV) and tested for failure. Results. Bones fractured at a mean maximum load of 482.8âNâ±â104.8âN with a relative standard deviation (RSD) of 21.7%, mean stiffness was 122.3â±â35âN/mm. In the fracture model, there was a significant difference (P = 0.01) for maximum load of monocortically and bicortically fixed bones in contrast to the osteotomy model (P = 0.9). Discussion. In the fracture model, because one can use the same bone for both measurements in the intact state and the bone-plate construct states, the impact of inter-individual differences is reduced. In contrast to the osteotomy model there are differences between monocortical and bicortical fixations in the fracture model. Thus simulation of the in vivo situation is better and seems to be suitable for the evaluation of mechanical properties of fixation techniques on metacarpals
Optimization of Material Contrast for Efficient FIBâSEM Tomography of Solid Oxide Fuel Cells
Focused ion beam (FIB) â scanning electron microscopy (SEM) serial sectioning tomography has become an important tool for threeâdimensional microstructure reconstruction of solid oxide fuel cells (SOFC) to obtain an understanding of fabricationârelated effects and SOFC performance. By sequential FIB milling and SEM imaging a stack of crossâsection images across all functional SOFC layers was generated covering a large volume of 3.5·10 ÎŒm. One crucial step is image segmentation where regions with different image intensities are assigned to different material phases within the SOFC. To analyze all relevant SOFC materials, it was up to now mandatory to acquire several images by scanning the same region with different imaging parameters because sufficient material contrast could otherwise not be achieved. In this work we obtained highâcontast SEM images from a single scan to reconstract all functional SOFC layers consisting of a Ni/YOâdoped ZrO (YDZ) cermet anode, YDZ electrolyte and (La,Sr)MnO/YDZ cathode. This was possible by using different, simultaneous readâout detectors installed in a stateâofâtheâart scanning electron microscope. In addition, we used a deterministic approach for the optimization of imaging parameters by employing Monte Carlo simulations rather than trialâandâerror tests. We also studied the effect of detection geometry, detecting angle range and detector type
Effect of Yttrium (Y) and Zirconium (Zr) Doping on the Thermodynamical Stability of the Cubic Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe0.2O<sub>3-ÎŽ</sub> Phase
Electronic sculpting of ligand-GPCR subtype selectivity:the case of angiotensin II
GPCR subtypes possess distinct functional
and pharmacological profiles,
and thus development of subtype-selective ligands has immense therapeutic
potential. This is especially the case for the angiotensin receptor
subtypes AT1R and AT2R, where a functional negative control has been
described and AT2R activation highlighted as an important cancer drug
target. We describe a strategy to fine-tune ligand selectivity for
the AT2R/AT1R subtypes through electronic control of ligand aromatic-prolyl
interactions. Through this strategy an AT2R high affinity (<i>K</i><sub>i</sub> = 3 nM) agonist analogue that exerted 18,000-fold
higher selectivity for AT2R versus AT1R was obtained. We show that
this compound is a negative regulator of AT1R signaling since it is
able to inhibit MCF-7 breast carcinoma cellular proliferation in the
low nanomolar range
Control of primary productivity and the significance of photosynthetic bacteria in a meromictic kettle lake.
During 1986 planktonic primary production and controlling factors were investigated in a small (A0 = 11.8 · 103 m2, Zmax = 11.5 m) meromictic kettle lake (Mittlerer Buchensee). Annual phytoplankton productivity was estimated to ca 120 gC · mâ2 · aâ1 (1,42 tC · lakeâ1 · aâ1). The marked thermal stratification of the lake led to irregular vertical distributions of chlorophylla concentrations (Chla) and, to a minor extent, of photosynthesis (Az). Between the depths of 0 to 6 m low Chla concentrations (< 7 mg · mâ3) and comparatively high background light attenuation (kw = 0,525 mâ1, 77% of total attenuation due to gelbstoff and abioseston) was found. As a consequence, light absorption by algae was low (mean value 17,4%) and self-shading was absent.
Because of the small seasonal variation of Chla concentrations, no significant correlation between Chla and areal photosynthesis (A) was observed. Only in early summer (JuneâJuly) biomass appears to influence the vertical distribution of photosynthesis on a bigger scale. Around 8 m depth, low-light adapted algae and phototrophic bacteria formed dense layers. Due to low ambient irradiances, the contribution of these organisms to total primary productivity was small. Primary production and incident irradiance were significantly correlated with each other (r2 = 0.68). Although the maximum assimilation number (Popt) showed a clear dependence upon water temperature (Q10 = 2.31), the latter was of minor importance to areal photosynthesis
- âŠ