Species traits and catchment‐scale habitat factors influence the occurrence of freshwater mussel populations and assemblages

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Systematic Dissection of the Metabolic-Apoptotic Interface in AML Reveals Heme Biosynthesis to Be a Regulator of Drug Sensitivity

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Acquisition and voxelwise analysis of multi-subject diffusion data with tract-based spatial statistics

There is much interest in using magnetic resonance diffusion imaging to provide information on anatomical connectivity in the brain by measuring the diffusion of water in white matter tracts. Among the measures, the most commonly derived from diffusion data is fractional anisotropy (FA), which quantifies local tract directionality and integrity. Many multi-subject imaging studies are using FA images to localize brain changes related to development, degeneration and disease. In a recent paper, we presented a new approach, tract-based spatial statistics (TBSS), which aims to solve crucial issues of cross-subject data alignment, allowing localized cross-subject statistical analysis. This works by transforming the data from the centers of the tracts that are consistent across a study's subjects into a common space. In this protocol, we describe the MRI data acquisition and analysis protocols required for TBSS studies of localized change in brain connectivity across multiple subjects.     

Neuromechanics: an integrative approach for understanding motor control

Neuromechanics seeks to understand how muscles, sense organs,motor pattern generators, and brain interact to produce coordinatedmovement, not only in complex terrain but also when confrontedwith unexpected perturbations. Applications of neuromechanicsinclude ameliorating human health problems (including prosthesisdesign and restoration of movement following brain or spinalcord injury), as well as the design, actuation and control ofmobile robots. In animals, coordinated movement emerges fromthe interplay among descending output from the central nervoussystem, sensory input from body and environment, muscle dynamics,and the emergent dynamics of the whole animal. The inevitablecoupling between neural information processing and the emergentmechanical behavior of animals is a central theme of neuromechanics.Fundamentally, motor control involves a series of transformationsof information, from brain and spinal cord to muscles to body,and back to brain. The control problem revolves around the specifictransfer functions that describe each transformation. The transferfunctions depend on the rules of organization and operationthat determine the dynamic behavior of each subsystem (i.e.,central processing, force generation, emergent dynamics, andsensory processing). In this review, we (1) consider the contributionsof muscles, (2) sensory processing, and (3) central networksto motor control, (4) provide examples to illustrate the interplayamong brain, muscles, sense organs and the environment in thecontrol of movement, and (5) describe advances in both roboticsand neuromechanics that have emerged from application of biologicalprinciples in robotic design. Taken together, these studiesdemonstrate that (1) intrinsic properties of muscle contributeto dynamic stability and control of movement, particularly immediatelyafter perturbations; (2) proprioceptive feedback reinforcesthese intrinsic self-stabilizing properties of muscle; (3) controlsystems must contend with inevitable time delays that can simplifyor complicate control; and (4) like most animals under a varietyof circumstances, some robots use a trial and error processto tune central feedforward control to emergent body dynamics.     

In vitro evaluation of native entomopathogenic fungi and neem (Azadiractha indica) extracts on Spodoptera frugiperda

The control of Spodoptera frugiperda is based on synthetic insecticides, so some alternatives are the use of entomopathogenic fungi (EF) and neem extract. The objective of the study was to evaluate in vitro effectiveness of native EF and neem extracts on S. frugiperda larvae. Six EF were identified by DNA sequencing of ITS regions from three EF (Fusarium solani, Metarrhizium robertsii, Nigrospora spherica and Penicillium citrinum). They were evaluated in concentrations of 1 × 10⁸ spores/ mL. In addition, a second bioassay was carried out evaluating only F. solani, M. robertsii and N. sphaerica and the addition of vegetable oil. On the other hand, extraction of secondary metabolites from neem seed (Azadirachta indica) was carried out by performing, mass (g) and solvent volume (mL ethanol and water) combinations, which were subjected to microwaves and ultrasound. Subsequently, these extracts were evaluated in concentrations of 3%, 4% and 5%. A survival analysis was performed for each of the bioassays. With respect to the results of the first bioassay, F. solani obtained a probability of survival of 0.476 on the seventh day, while in the second bioassay, M. robertsii obtained 0.488 survival probability. This suggests that the expected percentage of larvae that stay alive on the sixth day is 48.8%. However, in the evaluation of the neem extract the combination 1:12/70% to 4% caused 84% mortality of larvae. The use of native HE and neem extracts has potential for the control of S. frugiperda.     

ATP interaction with the open state of the K(ATP) channel

The mechanism of ATP-sensitive potassium (K(ATP)) channel closure by ATP is unclear, and various kinetic models in which ATP binds to open or to closed states have previously been presented. Effects of phosphatidylinositol bisphosphate (PIP2) and multiple Kir6.2 mutations on ATP inhibition and open probability in the absence of ATP are explainable in kinetic models where ATP stabilizes a closed state and interaction with an open state is not required. Evidence that ATP can in fact interact with the open state of the channel is presented here. The mutant Kir6.2[L164C] is very sensitive to Cd2+ block, but very insensitive to ATP, with no significant inhibition in 1 mM ATP. However, 1 mM ATP fully protects the channel from Cd2+ block. Allosteric kinetic models in which the channel can be in either open or closed states with or without ATP bound are considered. Such models predict a pedestal in the ATP inhibition, i.e., a maximal amount of inhibition at saturating ATP concentrations. This pedestal is predicted to occur at >50 mM ATP in the L164C mutant, but at >1 mM in the double mutant L164C/R176A. As predicted, ATP inhibits Kir6.2[L164C/R176A] to a maximum of approximately 40%, with a clear plateau beyond 2 mM. These results indicate that ATP acts as an allosteric ligand, interacting with both open and closed states of the channel.     

p53 unfolding detected by CD but not by tryptophan fluorescence

Full-length human p53 protein was examined using tryptophan fluorescence and circular dichroism spectroscopy (CD) to monitor unfolding. No significant alteration in tryptophan fluorescence for the tetrameric protein was detectable over a wide range of either urea or guanidine hydrochloride concentrations, in contrast to results with the isolated DNA binding domain [Bullock et al. (1997) Proc. Natl. Acad. Sci. USA 94, 14338]. Under similar denaturant conditions, CD demonstrated significant protein unfolding for the full-length wild-type protein, with increased apparent structure loss compared to that detected during thermal denaturation [Nichols and Matthews (2001) Biochemistry 40, 3847]. Examination of X-ray structures containing two of the four tryptophan residues of a p53 monomer suggested local environments consistent with quenched fluorophores. Exploration of p53 fluorescence using potassium iodide as a quencher confirmed that these fluorophores are already substantially quenched in the native structure, and this quenching is not relieved during protein unfolding.