Pyrane to oxepane in one step: Highly regio‐ and stereoselective homologations dependent on the nature of carbonyl function and catalysts have been observed during the formation of enoxysilanes (see ...scheme). Trimethylsilyl trifluoromethanesulfonate (TMSOTf) and AlCl3 were identified as suitable catalysts to promote the homologation and ring‐enlargement.
Pyrane to oxepane in one step: Highly regio- and stereoselective homologations dependent on the nature of carbonyl function and catalysts have been observed during the formation of enoxysilanes. ...Trimethylsilyl trifluoromethanesulfonate (TMSOTf) and AlCl3 were identified as suitable catalysts to promote the homologation and ring-enlargement.
Group I metabotropic glutamate receptors, in particular mGluR5, have been implicated in various forms of synaptic plasticity that are believed to underlie declarative memory. We observed that mGluR5 ...specifically activated a channel containing TRPC1, an isoform of the canonical family of transient receptor potential (TRPC) channels highly expressed in CA1-3 regions of the hippocampus. TRPC1 is able to form tetrameric complexes with TRPC4 and/or TRPC5 isoforms. TRPC1/4/5 complexes have recently been involved in the efficiency of synaptic transmission in the hippocampus. We therefore used a mouse model devoid of TRPC1 expression to investigate the involvement of mGluR5-TRPC1 pathway in synaptic plasticity and memory formation.
mice showed alterations in spatial working memory and fear conditioning. Activation of mGluR increased synaptic excitability in neurons from WT but not from
mice. LTP triggered by a theta burst could not maintain over time in brain slices from
mice. mGluR-induced LTD was also impaired in these mice. Finally, acute inhibition of TRPC1 by Pico145 on isolated neurons or on brain slices mimicked the genetic depletion of
and inhibited mGluR-induced entry of cations and subsequent effects on synaptic plasticity, excluding developmental or compensatory mechanisms in
mice. In summary, our results indicate that TRPC1 plays a role in synaptic plasticity and spatial working memory processes.
Group I metabotropic glutamate receptors (mGluR) are involved in various forms of synaptic plasticity that are believed to underlie declarative memory. We previously showed that mGluR5 specifically ...activates channels containing TRPC1, an isoform of the canonical family of Transient Receptor Potential channels highly expressed in the CA1-3 regions of the hippocampus. Using a tamoxifen-inducible conditional knockout model, we show here that the acute deletion of the
gene alters the extinction of spatial reference memory. mGluR-induced long-term depression, which is partially responsible for memory extinction, was impaired in these mice. Similar results were obtained in vitro and in vivo by inhibiting the channel by its most specific inhibitor, Pico145. Among the numerous known postsynaptic pathways activated by type I mGluR, we observed that the deletion of
impaired the activation of ERK1/2 and the subsequent expression of Arc, an immediate early gene that plays a key role in AMPA receptors endocytosis and subsequent long-term depression.
The hormone adiponectin (ApN) is decreased in the metabolic syndrome, where it plays a key pathogenic role. ApN also exerts some anti-inflammatory effects on skeletal muscles in mice exposed to acute ...or chronic inflammation. Here, we investigate whether ApN could be sufficiently potent to counteract a severe degenerative muscle disease, with an inflammatory component such as Duchenne muscular dystrophy (DMD).
Mdx mice (a DMD model caused by dystrophin mutation) were crossed with mice overexpressing ApN in order to generate mdx-ApN mice; only littermates were used. Different markers of inflammation/oxidative stress and components of signaling pathways were studied. Global force was assessed by in vivo functional tests, and muscle injury with Evans Blue Dye (EBD). Eventually, primary cultures of human myotubes were used.
Circulating ApN was markedly diminished in mdx mice. Replenishment of ApN strikingly reduced muscle inflammation, oxidative stress, and enhanced the expression of myogenic differentiation markers along with that of utrophin A (a dystrophin analog) in mdx-ApN mice. Accordingly, mdx-ApN mice exhibited higher global force and endurance as well as decreased muscle damage as quantified by curtailed extravasation of EBD in myofibers. These beneficial effects of ApN were recapitulated in human myotubes. ApN mediates its protection via the adiponectin receptor 1 (AdipoR1, the main ApN receptor in muscle) and the AMPK-SIRT1-PGC-1α signaling pathway, leading to downregulation of the nuclear factor kappa B (NF-κB) and inflammatory genes, together with upregulation of utrophin.
Adiponectin proves to be an extremely powerful hormone capable of protecting the skeletal muscle against inflammation and injury, thereby offering novel therapeutic perspectives for dystrophinopathies.
We produced and analyzed mice deficient for Na/Ca exchanger 3 (NCX3), a protein that mediates cellular Ca(2+) efflux (forward mode) or Ca(2+) influx (reverse mode) and thus controls intracellular ...Ca(2+) concentration. NCX3-deficient mice (Ncx3(-/-)) present a skeletal muscle fiber necrosis and a defective neuromuscular transmission, reflecting the absence of NCX3 in the sarcolemma of the muscle fibers and at the neuromuscular junction. The defective neuromuscular transmission is characterized by the presence of electromyographic abnormalities, including low compound muscle action potential amplitude, a decremental response at low-frequency nerve stimulation, an incremental response, and a prominent postexercise facilitation at high-frequency nerve stimulation, as well as neuromuscular blocks. The analysis of quantal transmitter release in Ncx3(-/-) neuromuscular junctions revealed an important facilitation superimposed on the depression of synaptic responses and an elevated delayed release during high-frequency nerve stimulation. It is suggested that Ca(2+) entering nerve terminals is cleared relatively slowly in the absence of NCX3, thereby enhancing residual Ca(2+) and evoked and delayed quantal transmitter release during repetitive nerve stimulation. Our findings indicate that NCX3 plays an important role in vivo in the control of Ca(2+) concentrations in the skeletal muscle fibers and at the neuromuscular junction.
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