Oligodendrocyte ablation affects the coordinated interaction between granule and Purkinje neurons during cerebellum development

Oligodendrocytes (OLs) are the glial cells of the central nervous system (CNS) classically known to be devoted to the formation of myelin sheaths around most axons of the vertebrate brain. We have addressed the role of these cells during cerebellar development, by ablating OLs in vivo. Previous analyses had indicated that OL ablation during the first six postnatal days results into a striking cerebellar phenotype, whose major features are a strong reduction of granule neurons and aberrant Purkinje cells development. These two cell types are highly interconnected during cerebellar development through the production of molecules that help their proliferation, differentiation and maintenance. In this article, we present data showing that OL ablation has major effects on the physiology of Purkinje (PC) and granule cells (GC). In particular, OL ablation results into a reduction of sonic hedgehog (Shh), Brain Derived Neurotrophic Factor (BDNF), and Reelin (Rln) expression. These results indicate that absence of OLs profoundly alters the normal cerebellar developmental program.     

Toward molecular dissection of PrPC-PrPSc interactions

Direct interaction between endogenous cellular prion protein (PrP(C)) and misfolded, disease-associated (PrP(Sc)) conformers is a key event in prion propagation, which precedes templated conversion of PrP(C) into nascent PrP(Sc) and prion infectivity. Although almost none of the molecular details of this pivotal process are understood, the persistence of individual prion strains suggests that assembly of the prion replicative complex is mechanistically precise. To systematically map defined regions of PrP(C) sequence that bind tightly to PrP(Sc), we have generated a comprehensive panel of over 45 motif-grafted antibodies containing overlapping peptide grafts collectively spanning PrP residues 19-231. Grafted antibody binding experiments, performed under stringent conditions, clearly identified only three distinct and independent high affinity PrP(Sc) recognition motifs. The first of these binding motifs lies at the very N-terminal region of the mature PrP molecule within PrP-(23-33); the second motif lies within PrP-(98-110); and the third is contained within PrP-(136-158). Mutational analyses of these PrP(Sc)-binding regions revealed that reactivity of the 23-33 and 98-110 segments are largely dependent upon the presence of multiple positively charged amino acid residues. These studies yield new insight into critical peptidic components composing one side of the prion replicative interface.     

Highly pathogenic H5N1 avian influenza: entry pathways into North America via bird migration

Given the possibility of highly pathogenic H5N1 avian influenza arriving in North America and monitoring programs that have been established to detect and track it, we review intercontinental movements of birds. We divided 157 bird species showing regular intercontinental movements into four groups based on patterns of movement-one of these groups (breed Holarctic, winter Eurasia) fits well with the design of the monitoring programs (i.e., western Alaska), but the other groups have quite different movement patterns, which would suggest the importance of H5N1 monitoring along the Pacific, Atlantic, and Gulf coasts of North America.     

Decline in self-renewal factors contributes to aging of the stem cell niche in the Drosophila testis

Aging is characterized by compromised organ and tissue function. A decrease in stem cell number and/or activity could lead to the aging-related decline in tissue homeostasis. We have analyzed how the process of aging affects germ line stem cell (GSC) behavior in the Drosophila testis and report that significant changes within the stem cell microenvironment, or niche, occur that contribute to a decline in stem cell number over time. Specifically, somatic niche cells in testes from older males display reduced expression of the cell adhesion molecule DE-cadherin and a key self-renewal signal unpaired (upd). Loss of upd correlates with an overall decrease in stem cells residing within the niche. Conversely, forced expression of upd within niche cells maintains GSCs in older males. Therefore, our data indicate that age-related changes within stem cell niches may be a significant contributing factor to reduced tissue homeostasis and regeneration in older individuals.     

Quantitative determination of the macrolide antibiotic tulathromycin in plasma and broncho-alveolar cells of foals using tandem mass spectrometry

The long-acting antibiotic tulathromycin is on the marked for treatment of pulmonary infection of cattle, swine and horses. To measure disposition and distribution of tulathromycin in foals, a high throughput method was developed for horse plasma (calibration range: 0.006-0.8 microg/mL) and broncho-alveolar cells (calibration range: 0.1-4.0 microg/10(9)cells) using tandem mass spectrometry. Tulathromycin was extracted from plasma and broncho-alveolar fluid using cation exchange cartridges with acetonitrile/ammonia (95:5, v/v). The chromatography was performed isocratically with a mobile phase consisting of 5 mM ammonium formiate buffer/acetonitrile (30:70, v/v). The mass spectrometer operated in selected ion mode with atmospheric pressure chemical ionization to monitor the respective MH+ ions m/z 577.3 for tulathromycin and m/z 679.3 for the internal standard roxithromycin. All quality parameters fulfilled the international criteria for bioanalytical method validation and were successfully applied to the determination of tulathromycin in plasma of foals and broncho-alveolar cells. In foals, tulathromycin after intramuscular administration was rapidly absorbed, widely distributed and slowly eliminated. It cumulated manifold in broncho-alveolar cells.     

Mechanical response and conformational changes of alpha-actinin domains during unfolding: a molecular dynamics study

Alpha-actinin is a cytoskeleton-binding protein involved in the assembly and regulation of the actin filaments. In this work molecular dynamics method was applied to investigate the mechanical behaviour of the human skeletal muscle α-actinin. Five configurations were unfolded at an elongation speed of 0.1 nm/ps in order to investigate the conformational changes occurring during the extension process. Moreover, a sensitivity analysis at different velocities was performed for one of the R2–R3 spectrin-like repeat configuration extracted in order to evaluate the effect of the pulling speed on the mechanical behaviour of the molecule. Two different behaviours were recognized with respect to the pulling speed. In particular, at speed higher than 0.025 nm/ps a continuous rearrangement without evident force peaks was obtained, on the contrary at lower speed evident peaks in the range 500–750 pN were detected. R3 repeat resulted more stable than R2 during mechanical unfolding, due to the lower hydrophobic surface available to the solvent. The characterization of the R2–R3 units can be useful for the development of cytoskeleton network models based on stiffness values obtained by analyses performed at the molecular level.     

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.     

Yeast functional genomic screens lead to identification of a role for a bacterial effector in innate immunity regulation

Numerous bacterial pathogens manipulate host cell processes to promote infection and ultimately cause disease through the action of proteins that they directly inject into host cells. Identification of the targets and molecular mechanisms of action used by these bacterial effector proteins is critical to understanding pathogenesis. We have developed a systems biological approach using the yeast Saccharomyces cerevisiae that can expedite the identification of cellular processes targeted by bacterial effector proteins. We systematically screened the viable yeast haploid deletion strain collection for mutants hypersensitive to expression of the Shigella type III effector OspF. Statistical data mining of the results identified several cellular processes, including cell wall biogenesis, which when impaired by a deletion caused yeast to be hypersensitive to OspF expression. Microarray experiments revealed that OspF expression resulted in reversed regulation of genes regulated by the yeast cell wall integrity pathway. The yeast cell wall integrity pathway is a highly conserved mitogen-activated protein kinase (MAPK) signaling pathway, normally activated in response to cell wall perturbations. Together these results led us to hypothesize and subsequently demonstrate that OspF inhibited both yeast and mammalian MAPK signaling cascades. Furthermore, inhibition of MAPK signaling by OspF is associated with attenuation of the host innate immune response to Shigella infection in a mouse model. These studies demonstrate how yeast systems biology can facilitate functional characterization of pathogenic bacterial effector proteins.     

Edible zombis: fresh fish and the industry of cosmetic corpses

Doing research on fishery commodities in Portugal led us to an enigma: for a dead fish to be fresco (fresh) it must be alive. This paradox manifests at a popular, commercial, and legal level. It denotes the interruption of the difference between being dead and being alive in the commodity form. In Portugal, we suggest, the commercialization of peixe fresco (fresh fish) is based on the production and consumption of edible ‘zombis’: seafood corpses technologically and symbolically crafted as undead. An open concept, ‘edible zombis’ is part of an experimental vocabulary that foregrounds the productive agency of undeadness, both biological and commercial, in the seafood economic complex. It relates to the ordinary practice of necromancy in the commodity-based world. Edible zombis are commodity fetishes that fetishize their producers and consumers, suspending them from the capitalist system in which they live.