Interspecies hormonal interactions between man and the domestic dog (Canis familiaris)

To date, hormonal influence in interspecies interaction has not been examined. In a study of a dog agility competition among human/dog teams, men's pre-competition basal testosterone (T) levels were positively related to changes in dogs' cortisol levels from pre- to post-competition, but only among losing teams. Furthermore, pre-competition basal T in men on losing teams predicted more than half of the variance in dogs' cortisol change. This relationship was mediated through men's punitive and affiliative behaviors towards their dogs immediately after competition. Men's T change was also a significant predictor of dogs' change in cortisol such that men who experienced greater decreases in T after a loss were associated with dogs that experienced greater increases in cortisol. In winning teams, men's pre-competition T and T changes were unrelated to dogs' cortisol changes. These results are discussed in light of T as a proxy for dominance motivation as well as T's relation to stress across the species boundary.     

Robust and fast whole brain mapping of the RF transmit field B1 at 7T

In-vivo whole brain mapping of the radio frequency transmit field B(1) (+) is a key aspect of recent method developments in ultra high field MRI. We present an optimized method for fast and robust in-vivo whole-brain B(1) (+) mapping at 7T. The method is based on the acquisition of stimulated and spin echo 3D EPI images and was originally developed at 3T. We further optimized the method for use at 7T. Our optimization significantly improved the robustness of the method against large B(1) (+) deviations and off-resonance effects present at 7T. The mean accuracy and precision of the optimized method across the brain was high with a bias less than 2.6 percent unit (p.u.) and random error less than 0.7 p.u. respectively.     

Auditory processing across the sleep-wake cycle: simultaneous EEG and fMRI monitoring in humans

We combined fMRI and EEG recording to study the neurophysiological responses associated with auditory stimulation across the sleep-wake cycle. We found that presentation of auditory stimuli produces bilateral activation in auditory cortex, thalamus, and caudate during both wakefulness and nonrapid eye movement (NREM) sleep. However, the left parietal and, bilaterally, the prefrontal and cingulate cortices and the thalamus were less activated during NREM sleep compared to wakefulness. These areas may play a role in the further processing of sensory information required to achieve conscious perception during wakefulness. Finally, during NREM sleep, the left amygdala and the left prefrontal cortex were more activated by stimuli having special affective significance than by neutral stimuli. These data suggests that the sleeping brain can process auditory stimuli and detect meaningful events.     

rac regulates its effector phospholipase Cgamma2 through interaction with a split pleckstrin homology domain

Several isoforms of phospholipase C (PLC) are regulated through interactions with Ras superfamily GTPases, including Rac proteins. Interestingly, of two closely related PLCgamma isoforms, only PLCgamma(2) has previously been shown to be activated by Rac. Here, we explore the molecular basis of this interaction as well as the structural properties of PLCgamma(2) required for activation. Based on reconstitution experiments with isolated PLCgamma variants and Rac2, we show that an unusual pleckstrin homology (PH) domain, designated as the split PH domain (spPH), is both necessary and sufficient to effect activation of PLCgamma(2) by Rac2. We also demonstrate that Rac2 directly binds to PLCgamma(2) as well as to the isolated spPH of this isoform. Furthermore, through the use of NMR spectroscopy and mutational analysis, we determine the structure of spPH, define the structural features of spPH required for Rac interaction, and identify critical amino acid residues at the interaction interface. We further discuss parallels and differences between PLCgamma(1) and PLCgamma(2) and the implications of our findings for their respective signaling roles.     

Crystallization of deoxyhemoglobin S by fiber alignment and fusion.

Fibers of deoxyhemoglobin S obtained directly from lysed sickled red blood cells have been compared with fibers from chromatographically pure deoxyhemoglobin S solutions of known chemical composition. Electron micrographs of negatively stained specimens reveal that the molecular packing within the fibers remains largely invariant with changes in pH, ionic strength, Mg²⁺ concentration, 2,3-diphosphoglycerate concentration, temperature or the method of deoxygenation.When solutions of chromatographically pure deoxyhemoglobin S are stirred, the fibers align into well defined fascicles. After several hours of stirring, long needles and twisted ribbons develop and in a relatively short time replace the fascicles in solution. With continued stirring all forms are replaced by small crystals. By use of electron microscopy and low-angle X-ray diffraction we have found these crystals to have cell parameters indistinguishable from those of crystals grown in polyethylene glycol and citrate/phosphate buffer at pH 5 to 6 (Wishner et al., 1975a).Our evidence indicates that crystal formation in stirred solutions of deoxyhemoglobin S is the result of a progressive alignment and fusion of the fibers, and that the molecular arrangement within the fibers is closely related to that within the crystal. The remarkable pH invariance of the molecular packing within the fiber and crystal structures is consistent with the dominance of hydrophobic bonding between molecules. The β6-valine contact observed by Wishner et al. (1975b) is apparently the pathological contact responsible for the polymerization of deoxyhemoglobin S in vivo. On the basis of our observations and knowledge of the crystal structure we propose that the deoxyhemoglobin S fiber consists of eight molecular double strands, four of which run in each direction along the length of the fiber.     

DON calibrant: Towards the production of certified B-trichothecene calibrants

Within an EC-funded project calibrants with certified concentrations of Deoxynivalenol (DON), 3-Acetyl-Deoxynivalenol (3-Ac-DON), 15-Acetyl-Deoxynivalenol (15-Ac-DON) and Nivalenol (NIV) in acetonitrile have been produced. So far the project has led to improved isolation and purification of the solid toxins fromFusarium cultures. In addition, conditions for the production, ampouling and transport of the toxin solutions have been optimised. Further investigations should lead to knowledge about storage conditions and internationally accepted molar absorption coefficients for DON, 3-Ac-DON, 15-Ac-DON and NIV in acetonitrile. The intercomparison study which is currently carried out will also help to support knowledge and experience exchange between laboratories in the field ofFusarium mycotoxin analysis.     

Structural and mechanistic insights into ras association domains of phospholipase C epsilon

Ras proteins signal to a number of distinct pathways by interacting with diverse effectors. Studies of ras/effector interactions have focused on three classes, Raf kinases, ral guanylnucleotide-exchange factors, and phosphatidylinositol-3-kinases. Here we describe ras interactions with another effector, the recently identified phospholipase C epsilon (PLCepsilon). We solved structures of PLCepsilon RA domains (RA1 and RA2) by NMR and the structure of the RA2/ras complex by X-ray crystallography. Although the similarity between ubiquitin-like folds of RA1 and RA2 proves that they are homologs, only RA2 can bind ras. Some of the features of the RA2/ras interface are unique to PLCepsilon, while the ability to make contacts with both switch I and II regions of ras is shared only with phosphatidylinositol-3-kinase. Studies of PLCepsilon regulation suggest that, in a cellular context, the RA2 domain, in a mode specific to PLCepsilon, has a role in membrane targeting with further regulatory impact on PLC activity.     

Predicting direct protein interactions from affinity purification mass spectrometry data

Background  

Affinity purification followed by mass spectrometry identification (AP-MS) is an increasingly popular approach to observe protein-protein interactions (PPI) in vivo. One drawback of AP-MS, however, is that it is prone to detecting indirect interactions mixed with direct physical interactions. Therefore, the ability to distinguish direct interactions from indirect ones is of much interest.