Comparison of molecular and morphological data on St Helena: Elaphoglossum

The endemic elaphoglossoid ferns, Elaphoglossum dimorphum, E. nervosum and Microstaphyla furcata of St Helena, form a closely related group within section Lepidoglossa when analysed phylogenetically using sequences from the chloroplast trnL intron (partial) and trnL-F intergenic spacer. Microstaphyla furcata, traditionally placed in its own genus, is clearly shown to belong to Elaphoglossum confirming the previous transfer of this species to Elaphoglossum as E. bifurcatum. There is hardly any trnL-F sequence divergence between the species, in fact sequences of E. nervosum and E. dimorphum are identical. These results are consistent with the possible origin of E. dimorphum as a hybrid between E. bifurcatum and E. nervosum or with the view that the three species are the result of a recent radiation. The potential conflict between phylogenetic and morphological distinctness in determining species conservation priorities is discussed.     

Toll-like receptor 4 deficiency: Smaller infarcts,but nogain in function

Backgound  

It has been reported that Toll-like receptor 4 (TLR4) deficiency reduces infarct size after myocardial ischemia/reperfusion (MI/R). However, measurement of MI/R injury was limited and did not include cardiac function. In a chronic closed-chest model we assessed whether cardiac function is preserved in TLR4-deficient mice (C3H/HeJ) following MI/R, and whether myocardial and systemic cytokine expression differed compared to wild type (WT).     

Distinct Contributions of the Dorsolateral Prefrontal and Orbitofrontal Cortex during Emotion Regulation

The lateral prefrontal and orbitofrontal cortices have both been implicated in emotion regulation, but their distinct roles in regulation of negative emotion remain poorly understood. To address this issue we enrolled 58 participants in an fMRI study in which participants were instructed to reappraise both negative and neutral stimuli. This design allowed us to separately study activations reflecting cognitive processes associated with reappraisal in general and activations specifically related to reappraisal of negative emotion. Our results confirmed that both the dorsolateral prefrontal cortex (DLPFC) and the lateral orbitofrontal cortex (OFC) contribute to emotion regulation through reappraisal. However, activity in the DLPFC was related to reappraisal independently of whether negative or neutral stimuli were reappraised, whereas the lateral OFC was uniquely related to reappraisal of negative stimuli. We suggest that relative to the lateral OFC, the DLPFC serves a more general role in emotion regulation, perhaps by reflecting the cognitive demand that is inherent to the regulation task.     

Coupled Diffusion of Peripherally Bound Peptides along the Outer and Inner Membrane Leaflets

Transmembrane signaling implies that peripheral protein binding to one leaflet be detected by the opposite leaflet. Therefore, protein recruitment into preexisting cholesterol and sphingolipid rich platforms may be required. However, no clear molecular picture has evolved about how these rafts in both leaflets are connected. By using planar lipid bilayers, we show that the peripheral binding of a charged molecule (poly-lysine, PLL) is detected at the other side of the bilayer without involvement of raft lipids. The diffusion coefficient, D_P, of PLL differed by a factor of √2 when PLL absorbed to one or to both leaflets of planar membranes. Fluorescence correlation spectroscopy showed that the changes of the lipid diffusion coefficient, D_M, were even more pronounced. Although D_M remained larger than D_P on PLL binding to the first membrane leaflet, D_M dropped to D_P on PLL binding to both leaflets, which indicated that the lipids sandwiched between two PLL molecules had formed a nanodomain. Due to its small area of ∼20 nm² membrane electrostriction or leaflet interaction at bilayer midplane can only make a small contribution to interleaflet coupling. The tendency of the system to maximize the area where the membrane is free to undulate seems to be more important. As a spot with increased bending stiffness, the PLL bound patch in one leaflet attracts a stiffening additive on the other leaflet. That is to say, instead of suppressing undulations in two spots, two opposing PLL molecules migrate along a membrane at matching positions and suppress these undulations in a single spot. The gain in undulation energy is larger than the energy required for the alignment of two small PLL domains in opposite leafs and their coordinated diffusion. We propose that this type of mechanical interaction between two membrane separated ligands generally contributes to transmembrane signaling.     

Kinetics of Oxygen Release from ORC

Oxygen release compounds (ORC) are one possibility to enhance aerobic degradation in contaminated aquifers. However, some applications have been reported where oxygen concentrations did not meet expectations, this was attributed to ground water composition, e.g., high pH. Column experiments have been performed and the measurements were interpreted using a numerical model to investigate oxygen release kinetics from ORC in more detail. Because the zero-order rate law recommended by the manufacturer did not reflect the measurements, a more complex kinetic scheme was developed. The simulations show a minor influence of inorganic ground water constituents on oxygen release from ORC in the columns due to buffering by mineral precipitation, but an enhanced oxygen release if aerobic degradation takes place. If ORC is applied as socks, the impact of inorganic ground water composition increases compared to the application in column experiments. A simple quadratic equation is provided to estimate oxygen release rate from the buffer capacity of the ground water versus increasing pH—a parameter easily determinable in the laboratory. For slightly mineralized waters with high pH, this equation forecasts decreased oxygen release, but no total inhibition of oxygen release.     

Structure and occurrence of perisinusoidal stellate cells in the liver of lactating dairy cows

The structure and occurrence of liver stellate cells were studied in healthy, mildly and severely ketotic lactating dairy cows. In addition, the stellate cells in five clinically healthy lactating cows, each sampled at five different occasions after parturition, were studied. Liver samples were obtained by percutaneous needle biopsy, immediately fixed in 3% glutaraldehyde and processed for light and electron microscopy. The volume fractions of stellate cells and hepatocytic fat were estimated. Bovine stellate cells contained one, often large lipid droplet, not surrounded by a membrane. The cells had a well-developed Golgi apparatus and rough endoplasmic reticulum. Morphological indications for collagen synthesis by the cells were found. The results also suggest that a direct exchange of material between hepatocytes and stellate cells is possible. The volume fraction of stellate cells was decreased and the fraction of hepatocytic fat increased in severely ketotic cows as compared to the other groups. A negative correlation between the volume fractions of hepatocytic fat and stellate cells was significant. Hepatocytic fat decreased significantly after parturition, but an increase in the volume fraction of stellate cells was not significant.