196,369 research outputs found
Neuromuscular Junction Dismantling in Amyotrophic Lateral Sclerosis
No full textNeuromuscular junction assembly and plasticity during embryonic, postnatal, and adult life are tightly regulated by the continuous cross-talk among motor nerve endings, muscle fibers, and glial cells. Altered communications among these components is thought to be responsible for the physiological age-related changes at this synapse and possibly for its destruction in pathological states. Neuromuscular junction dismantling plays a crucial role in the onset of Amyotrophic Lateral Sclerosis (ALS). ALS is characterized by the degeneration and death of motor neurons leading to skeletal muscle denervation, atrophy and, most often, death of the patient within five years from diagnosis. ALS is a non-cell autonomous disease as, besides motor neuron degeneration, glial cells, and possibly muscle fibers, play a role in its onset and progression. Here, we will review the recent literature regarding the mechanisms leading to neuromuscular junction disassembly and muscle denervation focusing on the role of the three players of this peripheral tripartite synapse
Glutamate at the vertebrate neuromuscular junction : from modulation to neurotransmission
No full textAlthough acetylcholine is the major neurotransmitter operating at the skeletal neuromuscular junction of many invertebrates and of vertebrates, glutamate participates in modulating cholinergic transmission and plastic changes in the last. Presynaptic terminals of neuromuscular junctions contain and release glutamate that contribute to the regulation of synaptic neurotransmission through its interaction with pre- and post-synaptic receptors activating downstream signaling pathways that tune synaptic efficacy and plasticity. During vertebrate development, the chemical nature of the neurotransmitter at the vertebrate neuromuscular junction can be experimentally shifted from acetylcholine to other mediators (including glutamate) through the modulation of calcium dynamics in motoneurons and, when the neurotransmitter changes, the muscle fiber expresses and assembles new receptors to match the nature of the new mediator. Finally, in adult rodents, by diverting descending spinal glutamatergic axons to a denervated muscle, a functional reinnervation can be achieved with the formation of new neuromuscular junctions that use glutamate as neurotransmitter and express ionotropic glutamate receptors and other markers of central glutamatergic synapses. Here, we summarize the past and recent experimental evidences in support of a role of glutamate as a mediator at the synapse between the motor nerve ending and the skeletal muscle fiber, focusing on the molecules and signaling pathways that are present and activated by glutamate at the vertebrate neuromuscular junction
Tailored Modifications of Poly (glycerol adipate) and Poly (diglycerol adipate) to Improve Drug Encapsulation
No full textSustainably derived poly(glycerol adipate) (PGA) delivers all the desirable features expected in a polymeric scaffold for drug-delivery, including biodegradability, biocompatibility, self-assembly into nanoparticles (NPs) and a functionalisable pendant group. Despite showing these advantages over commercial alkyl polyesters, PGA suffers from a series of key drawbacks caused by poor amphiphilic balance. This leads to weak drug-polymer interactions and subsequent low drug-loading in NPs, as well as low NPs stability [1].
Previously, we have shown as new functionalities can be introduced directly in the one-pot PGA enzymatic polymerisation without the need of further synthetic steps. By introducing 1,6-n-hexanediol (Hex), as hydrophobic diol, we managed to tune the amphiphilic balance of the new repetitive unit with consequent enhanced drug encapsulation [2].
In the present work, we further investigate the effect of amphiphilic balance variation upon physical
properties and drug interactions as well as self-assembly and NPs stability. We replaced glycerol with the more hydrophilic diglycerol, and then we adjusted the final amphiphilic balance of the polyester repetitive units by incorporating Hex. The produced materials have been extensively characterised, NPs have been produced and tested for their stability in different environments and for their ability to encode enhanced drug loading. Moreover, the novel materials have shown good biocompatibility in both in vitro and in vivo experiments.
[1] Swainson SME, Styliari ID, Taresco V, Garnett MC. Poly (glycerol adipate) (PGA), an Enzymatically
Synthesized Functionalizable Polyester and Versatile Drug Delivery Carrier: A Literature Update. Polymers (Basel). 2019, 11(10), 1561.
[2] P. L. Jacob, L. A. Ruiz Cantu, A. K. Pearce, Y. He, J. C. Lentz, J. C. Moore, F. Machado, G. Rivers, E.
Apebende, M. R. Fernandez, I. Francolini, R. Wildman, S. M. Howdle and V. Taresco, Polymer (Guildf)., 2021, 228, 123912
Metals recovery from printed circuit boards: the pursuit of environmental and economic sustainability
No full textThe possible optimization of metal recovery from Printed Circuit Boards (PCBs) and Central Processing Units (CPUs) has been investigated. Usual practice is to primarily recover metals with the highest market price. In contrast, the present work shows how strategic considerations of the value share (%) of metals content and data regarding the environmental impact of their recovery can instruct about the best strategies to adopt, pointing at the metals to be recovered as a priority depending on the case. An accurate PCBs’ characterization carried out through microwave digestion with a mixture of HNO3, HF and HCl, is a first essential step of the procedure. Then metals are recovered through chemical leaching with different chemical substances, exploiting both chemical and physical steps. In particular, a proposal to improve environmental and economic sustainability of the PCBs’ treatment is presented, which contrary to expectations first considers the recovery of Cu, Pb and Sn by leaching with 6M HNO3, followed only later by the recovery of gold and other precious metals. Although unusual, the recovery procedure can be adapted accordingly, allowing more profits, easier management and higher metals recovery rates
Funzionalizzazione e caratterizzazione chimico-fisica di matrici polimeriche a carattere anfifilico
No full textPolimeri amfifilici sono stati ottenuto per funzionalizzazione di un polimero commerciale, l'etilen vinil alcol 40/40. In particolare i gruppi alcolici del polimero sono stati funzionalizzati rispettivamente con capriloilcloruro, lauroilcloruro e stearilcloruro, per introdurre catene idrofobiche a diversa lunghezza. I polimeri ottenuti sono stati caratterizzati mediante analisi termica e prove di rigonfiamento in acqua. I supporti sviluppati possono essere sviluppati per l'immobilizzazione di enzimi ad interesse industriale
Volume CLEM and conventional EM: a dual approach to investigate the mechanism of neuronal dysfunction in Angelman Syndrome
No full textAngelman Syndrome (AS) is a rare neurodevelopmental disorder arising from the loss of the maternal copy of UBE3A, a paternally imprinted gene at neuronal level. Similarly to AS, other neurological defects due to an unproper UBE3A dosage are directly associated with alterations in brain development and synapse ultrastructure. The nanometric resolution of electron microscopy (EM) has proven essential for studying their outcome at the network level and establishing meaningful correlations between synapses geometrical features and their function. To explore whether UBE3A loss effect on the developing connectome was cell-autonomous, we in-utero electroporated CRISPR/Cas9 constructs to silence the endogenous UBE3A expression in a subset of layer 2/3 pyramidal neurons of the mouse somatosensory cortex. By creating z-confined NIRB marks we were able to relocate dendrites of interest and analyze spines complexity three-dimensionally from volumetric SBF-SEM datasets. Furthermore, we exploited conventional EM to examine excitatory synapses structure in the cortical circuit of a classic AS model pan-neuronally depleted from UBE3A expression. We identified pre-synaptic compartment defects that seem to diminish over time to make room for later changes in the post-synapse. Overall, the combined use of these two models should help clarify whether the defects originate within the neurons or their wider network
Endoplasmic reticulum architecture: structures in flux
No full textThe endoplasmic reticulum (ER) is a dynamic pleiomorphic organelle containing continuous but distinct subdomains. The diversity of ER structures parallels its many functions, including secretory protein biogenesis, lipid synthesis, drug metabolism and Ca2+ signaling. Recent studies are revealing how elaborate ER structures arise in response to subtle changes in protein levels, dynamics, and interactions as well as in response to alterations in cytosolic ion concentrations. Subdomain formation appears to be governed by principles of self-organization. Once formed, ER subdomains remain malleable and can be rapidly transformed into alternative structures in response to altered conditions. The mechanisms that modulate ER structure are likely to be important for the generation of the characteristic shapes of other organelles
Development Of Smart Polydiacetylene Micelles For In Vitro And In Vivo Tracking
No full textPolydiacetylenes (PDAs) are conjugated polymers that can form highly ordered structures with unique chromatic features. PDAs are typically obtained by polymerisation of diacetylene (DA) monomers using ultraviolet (UV) light irradiation without the need of any initiators, which generates a polymeric backbone with alternating C=C and C≡C bonds (one-yne), giving a blue non-fluorescent PDAs. Several stimuli, such as pH, temperature and ligand-receptor interaction, can induce a red-shift and weakly fluorescent colorimetric transition that makes PDAs a very interesting system in the field of sensors and drug delivery systems [1,2].
PDAs systems are usually prepared using amphiphilic commercial monomers like 10,12 - pentacosadyinoic acid (PCDA) and 10,12 - tricosadyinoic acid (TCDA), with the addition in the final formulation of phospholipids [3] and/or water-soluble polymers [4], that can influence PDAs system sensitivity, stability and drug-released properties.
In the present project, we selected poly(glycerol adipate) (PGA) as a novel greener polymeric alternative to develop PDAs mixed-micelles. The addition of PGA will confer to the final formulations biodegradability and biocompatibility [5]. Furthermore, PGA can self-assembly into nanoparticles (NPs) in aqueous media using nanoprecipitation method, which is highly compatible with traditional process for the formation of PDAs [6]. Due to PGA low toxicity and possibility to produce active polymeric prodrugs by drug coupling to the PGA backbone, PDA/PGA mixed-micelles can be considered a potential platform intrinsically biodegradable which may facilitate in vivo and in vitro tracking of delivery systems [7].
[1] X. Qian and B. Stadler, Chem. Mater. 2019, 31(4), 1196-1222.
[2] F. Fang, F. Meng, L. Luo, Mater. Chem. Front. 2020, 4(4), 1089,1104
[3] G.P. Camilloto, C.G. Otoni, G.W.R. de Almeida, I.R.N de Oliveira, L.H.M. da Silva, A.C. dos Santos Pires, N. De F.F. Soares. ACS Food Sci. Technol. 2021, 1(5), 745-753.
[4] A. Pankaew, N. Traiphol, R. Traiphol, Colloids Surf. Physicochem. Eng. Asp. 2021, 608, 125626.
[5] P.L. JacobsL.A. Ruiz Cantu, A.K. Pearce, Y. He, J.C. Lentz, J.C. Moore, F.Machado, G.Rivers, E. Apebende, M.R. Fernandenz, I. Francolini, R. Wildman, S.M. Howdle, V. Taresco, Poly (Glycerol Adipate) (PGA) Backbone Modifications with a Library of Functional Diols: Chemical and Physical Effects. Polymer, 228, 123912
[6] P. Kallinteri, S. Higgins, G.A. Hutcheon, C.B. St Pourcain, M.C. Garnett. Biomacromolecules
Chromium(III) removal fromwastewater by chitosan flakes
No full textChitosan is very effective in removing metal ions through their adsorption. A preliminary investigation of the adsorption of chromium(III) by chitosan was carried out by means of batch tests as a function of contact time, pH, ion competition, and initial chromium(III) concentration. The rate of adsorption was rather rapid (t1/2 < 18 min) and influenced by the presence of other metal ions. The obtained data were tested using the Langmuir and Freundlich isotherm models and, based on R2 values, the former appeared better applicable than the latter. Chitosan was found to have an excellent loading capacity for chromium(III), namely 138.0 mg Cr per g of chitosan at pH = 3.8, but metal ions adsorption was strongly influenced by the pH. About 76% of the recovered chromium was then removed simply by washing the used chitosan with 0.1 M EDTA (Ethylenediaminetetraacetic acid) solution. This study demonstrates that chitosan has the potential to become an effective and low-cost agent for wastewater treatment (e.g., tannery waste) and in situ environmental remediation
Assessing the Tendency of Fluorescent Proteins to Oligomerize Under Physiologic Conditions
No full textSeveral fluorescent proteins (FPs) are prone to forming low-affinity oligomers. This undesirable tendency is exacerbated when FPs are confined to membranes or when fused to naturally oligomeric proteins. Oligomerization of FPs limits their suitability for creating fusions with proteins of interest. Unfortunately, no standardized method evaluates the biologically relevant oligomeric state of FPs. Here, we describe a quantitative visual assay for assessing whether FPs are sufficiently monomeric under physiologic conditions. Membrane-associated FP-fusion proteins, by virtue of their constrained planar geometry, achieve high effective concentrations. We exploited this propensity to develop an assay to measure FP tendencies to oligomerize in cells. FPs were fused on the cytoplasmic end of an endoplasmic reticulum (ER) signal-anchor membrane protein (CytERM) and expressed in cells. Cells were scored based on the ability of CytERM to homo-oligomerize with proteins on apposing membranes and restructure the ER from a tubular network into organized smooth ER (OSER) whorl structures. The ratio of nuclear envelope and OSER structures mean fluorescent intensities for cells expressing enhanced green fluorescent protein (EGFP) or monomeric green fluorescent protein (mGFP) CytERM established standards for comparison of uncharacterized FPs. We tested three FPs and identified two as sufficiently monomeric, while a third previously reported as monomeric was found to strongly oligomerize
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