157 research outputs found
In vivo acetylcholine receptor expression induced by calcitonin gene-related peptide in rat soleus muscle
No full textWe applied calcitonin gene-related peptide (CGRP) by continuous perfusion of the extrajunctional surface of the adult rat soleus muscle in vivo. We obtained this through a fine polyethylene catheter connected to an Alzet pump implanted in the animal. The perfusion induced a local acetylcholine receptor accumulation in the membrane of the muscle fibres starting with a delay of one to two days, provided a chronic conduction block of soleus innervation was concomitantly present. The effect was prominent, being higher than that following denervation. The lack of acetylcholine receptor accumulation observed in sham perfused animals and the co-administration of CGRP and its competitive antagonist peptide, hCGRP(8-37), eliminates the possibility that the response to CGRP application represents an inflammatory reaction to foreign bodies instead of a specific effect of the peptide.We suggest that CGRP may act on the extrajunctional membrane of muscle fibres to help induce acetylcholine receptor accumulation after appropriate receptors for the peptide are re-expressed due to muscle paralysis. Whilst this is compatible with a role of CGRP in synaptogenesis, a recent study showed that alpha-CGRP(-/-) mutant mice have normal neuromuscular junction development. However, given the redundancy of factors involved in acetylcholine receptor accumulation, further experiments on multiple knock-outs need to be performed before a final conclusion is reached about the physiological significance of CGRP
Analysis of antibody microarrays high throughput data: from data processing to network inference. The case of B-cell chronic lymphocytic leukemia.
No full textA particular category of protein arrays, namely antibody microarrays, is becoming increasingly important in proteomic research. Consistent developments in the least few years led to the possibility to detect expression and phosphorylation level of hundreds of proteins at once in biological samples with unprecedented sensitivity, still unmatched by other methods, such as mass-spec. Being a relatively new technique, and considering the wealth of information potentially generated, the antibody microarrays approach requires ad-hoc strategies in terms of signal quantification and filtering, data normalization, statistical analysis and functional interpretation. In this study, several aspects are discussed, with particular focus on the antibody microarrays technology developed by the company Kinexus, CA USA.A meaningful example of the application of the discussed criteria is presented, in the context of a large study of human leukemia samples we performed, including 34 B-cell chronic lymphocytic leukemia and 10 healthy human subjects before and after stimulation with the chemokine CXCL12, analyzed by means of 44 arrays monitoring over 800 antibodies, also including about 300 antibodies detecting phosphosites. Comparison strategies and network analysis approaches are described. We used the network analysis platform Cytoscape (http://www.cytoscape.org/) along with plugins developed by our group (PesCa, CentiScaPe, www.cbcm.it) to highlight key pathways suggested by array data. Particular emphasis is given to the impact of microarray data on proteins network reconstruction and understanding of fundamental biological processes
Physical activity and anodal-transcranial direct current stimulation: a synergistic approach to boost motor cortex plasticity
No full textThe application of anodal-transcranial direct current stimulation (A-tDCS) over the primary motor cortex (M1) increases its structural and functional plasticity, as also physical exercise. Combining both interventions has a boosting effect, thus revealing a crucial role of the brain state during stimulation. Although brain slice and anesthetized animal studies support this, further investigation in awake animals is necessary. In the present study, we analyzed the effects of coupling A-tDCS with low-intensity physical activity on the mouse M1 structural and functional plasticity. C57BL/6 mice were monolaterally treated with M1 A-tDCS while walking on a rotarod or at rest. To assess the impact of our interventions, we analyzed both motor cortices for changes in neuronal activation, dendritic spine density, and functional synchronisation as measured by local field potential coherence. The combination of physical activity and M1 stimulation revealed a synergistic interhemispheric effect on cortical activation in both layers II/III and V, not present when using a single type of intervention. These data were accompanied by increased M1-M1 synchrony in the low-theta frequency, a hallmark of motor network activity in mice. Dendritic spine density revealed an effect of the combo, which was significantly higher only in layer II/III, accompanied by increased post-synaptic density protein 95 expression in the same area. Based on our findings, we propose that the efficacy of tDCS hinges on brain state rather than being merely a direct causal factor. The observed outcomes contribute to a deeper comprehension of the mechanisms governing structural and functional reorganisation within the motor cortex under physiological conditions, with potential implications for research on learning, memory, and neurological disorders such as stroke
The use of in vivo direct drug application to assess neural regulation of muscle properties.
No full textSkeletal muscle is a convenient model system for studying basic questions on the neural regulation of synaptogenesis and of many properties of sarcolemma and contractile apparatus. The study of the neural signals involved in a particular regulation and of the mediating intracellular pathways, requires the chronic application of drugs, second messengers, antibodies, trophic factors and the like. The most common way of application is in vitro treatment of muscle cell lines or primary myotube cultures. As an alternative to tissue culture, we developed a technique for in vivo application of the agents under study directly on skeletal muscle. An initial surgical step secures the tip of a fine polyethylene catheter (≤250 μm) onto the proximal surface of the adult rat soleus muscle. The onset of perfusion of the solution containing the agent, however, starts only 10–15 days later, pushed by an implanted Alzet pump connected to the catheter. After chronic in vivo treatment for the appropriate number of days, the muscle is processed as needed. We used various agents which are known to affect muscle fibre acetylcholine receptor regulation, namely, CGRP, tetrodotoxin, and KCl and obtained results which demonstrate the full effectiveness of this way of application
Paralysis of innervated and reinnervated muscles equally affects contractile properties as does permanent denervation
No full textThe effects of long lasting (4--5 weeks) nerve conduction block and denervation were compared by investigating contractile, morphological and histochemical properties of slow (soleus) and fast (EDL) rat skeletal muscles. The block was based on improved perfusion techniques of the sciatic nerve with a tetrodotoxin (TTX) solution delivered at doses adequate to obtain maximal effects in the muscles. The TTX-inactivated axons retained normal histological and physiological properties such as the ability to evoke full contractile responses, to regenerate, and to completely reinnervate muscle. In spite of their intact innervation or of their full reinnervation, the TTX-paralysed muscles underwent weight loss, fibre atrophy and reduction in force output quantitatively indistinguishable from those following denervation. The same was true for all other contractile parameters tested, that is, twitch speed, twitch to tetanus ratio, post-tetanic potentiation, endurance, and fibre type composition. The results indicate the fundamental role of activity as a regulatory signal for muscle contractile properties, while they do not support the notion of a participation of chemical, activity-independent factors in this regulatio
Activity-dependent vs neurotrophic modulation of acetylcholine receptor expression: evidence from rat soleus and extensor digitorum longus muscles confirms the exclusive role of activity
No full textEvoked electrical muscle activity suppresses the transcription of mRNAs for acetylcholine receptors in extrajunctional myonuclei. Muscle denervation or disuse release such inhibition and extrajunctional receptors appear. However, in soleus muscles paralyzed with nerve-applied tetrodotoxin, a restricted perijunctional region has been described where myonuclei remain inhibited, a finding attributed to nerve-derived trophic factor(s). Here, we reinvestigate extrajunctional acetylcholine receptor expression in soleus and extensor digitorum longus muscles up to 90 days after denervation or up to 20 days of disuse, to clarify the role of trophic factors, if any. The perijunctional region of soleus muscles strongly expressed acetylcholine receptors during the first 2-3 weeks of denervation. After 2-3 months this expression had disappeared. No perijunctional expression was seen after paralysis by tetrodotoxin or botulinum toxin A. In contrast, the extensor digitorum longus never displayed suppressed perijunctional acetylcholine receptor expression after any treatment, suggesting that it is an intrinsic property of soleus muscles. Soleus denervation only transiently removed the suppression, and its presence in long-term denervated soleus muscles contradicts any contribution from nerve-derived trophic factor(s). In conclusion, our results confirm that evoked electrical activity is the physiological factor controlling the expression of acetylcholine receptors in the entire extrajunctional membrane of skeletal muscles. This article is protected by copyright. All rights reserved
Early application of ipsilateral cathodal-tDCS in a mouse model of brain ischemia results in functional improvement and perilesional microglia modulation
No full textEarly stroke therapeutic approaches rely on limited options, further characterized by a narrow therapeutic time window. In this context, the application of transcranial direct current stimulation (tDCS) in the acute phases after brain ischemia is emerging as a promising non-invasive tool. Despite the wide clinical application of tDCS, the cellular mechanisms underlying its positive effects are still poorly understood. Here, we explored the effects of cathodal tDCS (C-tDCS) 6 h after focal forelimb M1 ischemia in Cx3CR1GFP/+ mice. C-tDCS improved motor functionality of the affected forelimb, as assessed by the cylinder and foot-fault tests at 48 h, though not changing the ischemic volume. In parallel, histological analysis showed that motor recovery is associated with decreased microglial cell density in the area surrounding the ischemic core, while astrocytes were not affected. Deeper analysis of microglia morphology within the perilesional area revealed a shift toward a more ramified healthier state, with increased processes' complexity and a less phagocytic anti-inflammatory activity. Taken together, our findings suggest a positive role for early C-tDCS after ischemia, which is able to modulate microglia phenotype and morphology in parallel to motor recovery
Editorial: Non-invasive brain stimulation techniques in neurological and neuropsychiatric disorders: Physiological and molecular evidence
No full text[no abstract available
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