105 research outputs found
A new Robertsonian translocation in Holstein-Friesian cattle
A new Robertsonian translocation was found in a cow of the Holstein-Friesian breed. GTG-banding allowed us to elucidate the anomaly as a centric fusion between chromosomes 19 and 21. CBG-banding demonstrated that the translocated chromosome was dicentric. Cytogenetic investigation of the relatives of the translocated animal revealed two other carriers.Une nouvelle translocation robertsonienne a Ă©tĂ© mise en Ă©vidence chez une vache de race Holstein. La coloration en bandes GTG nous a permis dâidentifier les chromosomes impliquĂ©s dans la translocation. Il sâagit des chromosomes 19 et 21. La coloration en bandes CBG montre que le chromosome transloquĂ© est dicentrique. Une analyse cytogĂ©nĂ©tique des apparentĂ©s de lâanimal porteur a permis de mettre en Ă©vidence aux autres animaux porteurs
An Allosteric Inhibitory Site Conserved in the Ectodomain of P2X Receptor Channels
P2X receptors constitute a gene family of cation channels gated by extracellular ATP. They mediate fast ionotropic purinergic signaling in neurons and non-excitable cell types in vertebrates. The highly calcium-permeable P2X4 subtype has been shown to play a significant role in cardiovascular physiology, inflammatory responses and neuro-immune communication. We previously reported the discovery of a P2X4-selective antagonist, the small organic compound BX430, with submicromolar potency for human P2X4 receptors and marked species-dependence (Ase et al., 2015). The present study investigates the molecular basis of P2X4 inhibition by the non-competitive blocker BX430 using a structural and functional approach relying on mutagenesis and electrophysiology. We provide evidence for the critical contribution of a single hydrophobic residue located in the ectodomain of P2X4 channel subunits, Ile312 in human P2X4, which determines blockade by BX430. We also show that the nature of this extracellular residue in various vertebrate P2X4 orthologs underlies their specific sensitivity or resistance to the inhibitory effects of BX430. Taking advantage of high-resolution crystallographic data available on zebrafish P2X4, we used molecular dynamics simulation to model the docking of BX430 on an allosteric binding site around Ile315 (zebrafish numbering) in the ectodomain of P2X4. We also observed that the only substitution I312D (human numbering) that renders P2X4 silent by itself has also a profound silencing effect on all other P2X subtypes tested when introduced at homologous positions. The generic impact of this aspartate mutation on P2X function indicates that the pre-TM2 subregion involved is conserved functionally and defines a novel allosteric inhibitory site present in all P2X receptor channels. This conserved structure-channel activity relationship might be exploited for the rational design of potent P2X subtype-selective antagonists of therapeutic value
P2Y12 expression and function in alternatively activated human microglia
Objective: To investigate and measure the functional significance of altered P2Y12 expression in the context of human microglia activation. Methods: We performed in vitro and in situ experiments to measure how P2Y12 expression can influence disease-relevant functional properties of classically activated (M1) and alternatively activated (M2) human microglia in the inflamed brain. Results: We demonstrated that compared to resting and classically activated (M1) human microglia, P2Y12 expression is increased under alternatively activated (M2) conditions. In response to ADP, the endogenous ligand of P2Y12, M2 microglia have increased ligand-mediated calcium responses, which are blocked by selective P2Y12 antagonism. P2Y12 antagonism was also shown to decrease migratory and inflammatory responses in human microglia upon exposure to nucleotides that are released during CNS injury; no effects were observed in human monocytes or macrophages. In situ experiments confirm that P2Y12 is selectively expressed on human microglia and elevated under neuropathologic conditions that promote Th2 responses, such as parasitic CNS infection. Conclusion: These findings provide insight into the roles of M2 microglia in the context of neuroinflammation and suggest a mechanism to selectively target a functionally unique population of myeloid cells in the CNS
Tensile Deformation of Oriented Poly(Δ-caprolactone) and Its Miscible Blends with Poly(vinyl methyl ether)
The structural evolution of micromolded poly(Δ-caprolactone)
(PCL) and its miscible blends with noncrystallizable poly(vinyl
methyl ether) (PVME) at the nanoscale was investigated as a function of
deformation ratio and blend composition using in situ synchrotron smallangle
X-ray scattering (SAXS) and scanning SAXS techniques. It was
found that the deformation mechanism of the oriented samples shows a
general scheme for the process of tensile deformation: crystal block slips
within the lamellae occur at small deformations followed by a stressinduced
fragmentation and recrystallization process along the drawing
direction at a critical strain where the average thickness of the crystalline
lamellae remains essentially constant during stretching. The value of the
critical strain depends on the amount of the amorphous component
incorporated in the blends, which could be traced back to the lower
modulus of the entangled amorphous phase and, therefore, the reduced network stress acting on the crystallites upon addition of
PVME. When stretching beyond the critical strain the slippage of the fibrils (stacks of newly formed lamellae) past each other
takes place resulting in a relaxation of stretched interlamellar amorphous chains. Because of deformation-induced introduction of
the amorphous PVME into the interfibrillar regions in the highly oriented blends, the interactions between fibrils becomes
stronger upon further deformation and thus impeding sliding of the fibrils to some extent leading finally to less contraction of the
interlamellar amorphous layers compared to the pure PCLNational Natural Science Foundation of China (21204088 and 21134006). This
work is within the framework of the RCUK/EPSRC Science Bridges China project of UKâChina Advanced Materials Research Institute (AMRI)
Presynaptic Nicotinic α7 and Non-α7 Receptors Stimulate Endogenous GABA Release from Rat Hippocampal Synaptosomes through Two Mechanisms of Action
BACKGROUND: Although converging evidence has suggested that nicotinic acetylcholine receptors (nAChR) play a role in the modulation of GABA release in rat hippocampus, the specific involvement of different nAChR subtypes at presynaptic level is still a matter of debate. In the present work we investigated, using selective α7 and α4ÎČ2 nAChR agonists, the presence of different nAChR subtypes on hippocampal GABA nerve endings to assess to what extent and through which mechanisms they stimulate endogenous GABA release. METHODOLOGY/FINDINGS: All agonists elicited GABA overflow. Choline (Ch)-evoked GABA overflow was dependent to external Ca(2+), but unaltered in the presence of Cd(2+), tetrodotoxin (TTX), dihydro-ÎČ-erythroidine (DHÎČE) and 1-(4,4-Diphenyl-3-butenyl)-3-piperidinecarboxylic acid hydrochloride SKF 89976A. The effect of Ch was blocked by methyllycaconitine (MLA), α-bungarotoxin (α-BTX), dantrolene, thapsigargin and xestospongin C, suggesting that GABA release might be triggered by Ca(2+) entry into synaptosomes through the α7 nAChR channel with the involvement of calcium from intracellular stores. Additionally, 5-Iodo-A-85380 dihydrochloride (5IA85380) elicited GABA overflow, which was Ca(2+) dependent, blocked by Cd(2+), and significantly inhibited by TTX and DHÎČE, but unaffected by MLA, SKF 89976A, thapsigargin and xestospongin C and dantrolene. These findings confirm the involvement of α4ÎČ2 nAChR in 5IA85380-induced GABA release that seems to occur following membrane depolarization and opening calcium channels. CONCLUSIONS/SIGNIFICANCE: Rat hippocampal synaptosomes possess both α7 and α4ÎČ2 nAChR subtypes, which can modulate GABA release via two distinct mechanisms of action. The finding that GABA release evoked by the mixture of sub-maximal concentration of 5IA85380 plus sub-threshold concentrations of Ch was significantly larger than that elicited by the sum of the effects of the two agonists is compatible with the possibility that they coexist on the same nerve terminals. These findings would provide the basis for possible selective pharmacological strategies to treat neuronal disorders that involve the dysfunction of hippocampal cholinergic system
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