171 research outputs found
Strenuous exercise triggers a life-threatening response in mice susceptible to malignant hyperthermia
No full textIn humans, hyperthermic episodes can be triggered by halogenated anesthetics [malignant hyperthermia (MH) susceptibility] and by high temperature [environmental heat stroke (HS)]. Correlation between MH susceptibility and HS is supported by extensive work in mouse models that carry a mutation in ryanodine receptor type-1 (RYR1Y522S/WT) and calsequestrin-1 knockout (CASQ1-null), 2 proteins that control Ca2+ release in skeletal muscle. As overheating episodes in humans have also been described during exertion, here we subjected RYR1Y522S/WT and CASQ1-null mice to an exertional-stress protocol (incremental running on a treadmill at 34°C and 40% humidity). The mortality rate was 80 and 78.6% in RYR1Y522S/WT and CASQ1-null mice, respectively, vs. 0% in wild-type mice. Lethal crises were characterized by hyperthermia and rhabdomyolysis, classic features of MH episodes. Of importance, pretreatment with azumolene, an analog of the drug used in humans to treat MH crises, reduced mortality to 0 and 12.5% in RYR1Y522S/WT and CASQ1-null mice, respectively, thanks to a striking reduction of hyperthermia and rhabdomyolysis. At the molecular level, azumolene strongly prevented Ca2+dependent activation of calpains and NF-kB by lowering myoplasmic Ca2+ concentration and nitro-oxidative stress, parameters that were elevated in RYR1Y522S/WT and CASQ1-null mice. These results suggest that common molecular mechanisms underlie MH crises and exertional HS in mice.—Michelucci, A., Paolini, C., Boncompagni, S., Canato, M., Reggiani, C., Protasi, F. Strenuous exercise triggers a life-threatening response in mice susceptible to malignant hyperthermia
Structural differentiation of skeletal muscle fibers in the absence of innervation in humans.
No full textProc Natl Acad Sci U S A. 2007 Dec 4;104(49):19339-44. Epub 2007 Nov 27.
Structural differentiation of skeletal muscle fibers in the absence of innervation in humans.
Boncompagni S, Kern H, Rossini K, Hofer C, Mayr W, Carraro U, Protasi F.
Source
Interuniversitary Institute of Miology, Centro Scienze dell'Invecchiamento, Università degli Studi G. d'Annunzio, I-66013 Chieti, Italy.
Abstract
The relative importance of muscle activity versus neurotrophic factors in the maintenance of muscle differentiation has been greatly debated. Muscle biopsies from spinal cord injury patients, who were trained with an innovative protocol of functional electrical stimulation (FES) for prolonged periods (2.4-9.3 years), offered the unique opportunity of studying the structural recovery of denervated fibers from severe atrophy under the sole influence of muscle activity. FES stimulation induced surprising recovery of muscle structure, mass, and force even in patients whose muscles had been denervated for prolonged periods before the beginning of FES training (up to 2 years) and had almost completely lost muscle-specific internal organization. Ninety percent (or more) of the fibers analyzed by electron microscopy showed a striking recovery of the ultrastructural organization of myofibrils and Ca(2+)-handling membrane systems. This functional/structural restoration follows a pattern that mimics some aspects of normal muscle differentiation. Most importantly, the recovery occurs in the complete absence of motor and sensory innervation and of nerve-derived trophic factors, that is, solely under the influence of muscle activity induced by electrical stimulation.
PMID:
18042706
[PubMed - indexed for MEDLINE]
PMCID: PMC2148291
Free PMC Articl
Role of the JP45-Calsequestrin Complex on Calcium Entry in Slow Twitch Skeletal Muscles
No full textWe exploited a variety of mouse models to assess the roles of JP45-CASQ1 (CASQ, calsequestrin) and JP45-CASQ2 on calcium entry in slow twitch muscles. In flexor digitorum brevis (FDB) fibers isolated from JP45-CASQ1-CASQ2 triple KO mice, calcium transients induced by tetanic stimulation rely on calcium entry via La3+- and nifedipine-sensitive calcium channels. The comparison of excitation-coupled calcium entry (ECCE) between FDB fibers from WT, JP45KO, CASQ1KO, CASQ2KO, JP45-CASQ1 double KO, JP45-CASQ2 double KO, and JP45-CASQ1-CASQ2 triple KO shows that ECCE enhancement requires ablation of both CASQs and JP45. Calcium entry activated by ablation of both JP45-CASQ1 and JP45-CASQ2 complexes supports tetanic force development in slow twitch soleus muscles. In addition, we show that CASQs interact with JP45 at Ca2+ concentrations similar to those present in the lumen of the sarcoplasmic reticulum at rest, whereas Ca2+ concentrations similar to those present in the SR lumen after depolarization-induced calcium release cause the dissociation of JP45 from CASQs. Our results show that the complex JP45-CASQs is a negative regulator of ECCE and that tetanic force development in slow twitch muscles is supported by the dynamic interaction between JP45 and CASQs
Atrophy-resistant fibers in permanent peripheral denervation of human skeletal muscle
No full textNeurol Res. 2008 Mar;30(2):137-44.
Atrophy-resistant fibers in permanent peripheral denervation of human skeletal muscle.
Biral D, Kern H, Adami N, Boncompagni S, Protasi F, Carraro U.
Source
Italian C.N.R. Institute of Neuroscience, and Laboratory of Translational Myology, Interdepartmental Research Center of Myology, c/o Department of Biomedical Sciences, University of Padova, I-35121 Padova, Italy.
Abstract
OBJECTIVE:
Human muscle fibers usually undergo severe atrophy/degeneration as a result of long-term peripheral denervation. However, some biopsies from paraplegic patients suffering complete conus cauda syndrome display the presence of a small percentage of muscle fibers with a very large diameter (big fibers). The objective of the present study is to determine if these big fibers are the result of residual innervation/reinnervation, or if instead they are fibers resistant to atrophy.
METHODS:
Human muscle biopsies were harvested from the vastus lateralis of spinal cord injury (SCI) patients affected by complete lower motor neuron lesion (LML). The specimens were either processed for light microscopy or embedded for electron microscopy (EM).
RESULTS:
Our results indicate that the big fibers are neither the results of residual innervation or sparse reinnervation. In spite of the fact that the extrasynaptic NCAM immunostaining disappear a few months after SCI, the big fibers are characterized by positive molecular markers of denervation, that is, the differential labeling of their dystrophin molecule by anti-C and anti-N terminals antibodies. Furthermore, the EM analysis shows that these cells present the peculiar ultrastructural disarrangements of the contractile apparatus and of the internal membrane systems characteristic of 'peripheral denervation'. No fibers presenting large areas of cross-striation were found. The EM analysis provides the final evidence that these big fibers are muscle fibers which are indeed denervated, very different from normal and/or disused (e.g. upper motor neuron lesion) muscle fibers.
DISCUSSION:
Although these large muscle fibers are surprisingly more frequent in human muscle biopsies after 3 years from SCI than earlier, it remains to be determined whether their presence in some biopsies but not in others is caused by sampling, or is related to other factors such as to subjects' background genetics, or the extent of passive stretching induced by different rehabilitation strategies.
PMID:
18397604
[PubMed - indexed for MEDLINE
Improper Remodeling of Organelles Deputed to Ca 2+ Handling and Aerobic ATP Production Underlies Muscle Dysfunction in Ageing
No full textProper skeletal muscle function is controlled by intracellular Ca2+ concentration and by efficient production of energy (ATP), which, in turn, depend on: (a) the release and re-uptake of Ca2+ from sarcoplasmic-reticulum (SR) during excitation–contraction (EC) coupling, which controls the contraction and relaxation of sarcomeres; (b) the uptake of Ca2+ into the mitochondrial matrix, which stimulates aerobic ATP production; and finally (c) the entry of Ca2+ from the extracellular space via store-operated Ca2+ entry (SOCE), a mechanism that is important to limit/delay muscle fatigue. Abnormalities in Ca2+ handling underlie many physio-pathological conditions, including dysfunction in ageing. The specific focus of this review is to discuss the importance of the proper architecture of organelles and membrane systems involved in the mechanisms introduced above for the correct skeletal muscle function. We reviewed the existing literature about EC coupling, mitochondrial Ca2+ uptake, SOCE and about the structural membranes and organelles deputed to those functions and Finally, we summarized the data collected in different, but complementary, projects studying changes caused by denervation and ageing to the structure and positioning of those organelles: a. denervation of muscle fibers—an event that contributes, to some degree, to muscle loss in ageing (known as sarcopenia)—causes misplacement and damage: (i) of membrane structures involved in EC coupling (calcium release units, CRUs) and (ii) of the mitochondrial network; b. sedentary ageing causes partial disarray/damage of CRUs and of calcium entry units (CEUs, structures involved in SOCE) and loss/misplacement of mitochondria; c. functional electrical stimulation (FES) and regular exercise promote the rescue/maintenance of the proper architecture of CRUs, CEUs, and of mitochondria in both denervation and ageing. All these structural changes were accompanied by related functional changes, i.e., loss/decay in function caused by denervation and ageing, and improved function following FES or exercise. These data suggest that the integrity and proper disposition of intracellular organelles deputed to Ca2+ handling and aerobic generation of ATP is challenged by inactivity (or reduced activity); modifications in the architecture of these intracellular membrane systems may contribute to muscle dysfunction in ageing and sarcopenia
Stable muscle atrophy in long-term paraplegics with complete upper motor neuron lesion from 3- to 20-year SCI.
No full textSpinal Cord. 2008 Apr;46(4):293-304. Epub 2007 Oct 23.
Stable muscle atrophy in long-term paraplegics with complete upper motor neuron lesion from 3- to 20-year SCI.
Kern H, Hofer C, Mödlin M, Mayr W, Vindigni V, Zampieri S, Boncompagni S, Protasi F, Carraro U.
Source
Department of Physical Medicine, Ludwig Boltzmann Institute of Electrostimulation and Physical Rehabilitation, Wilhelminenspital, Vienna, Austria.
Abstract
STUDY DESIGN:
Unrandomized trial.
OBJECTIVES:
To investigate the structural and functional relationships and the progression of muscle atrophy up to 20 years of spastic paraplegia.
SETTING:
Clinical follow-up in Vienna, Austria; muscle biopsies analyzed by light microscopy in Padova and by electron microscopy (EM) in Chieti, Italy.
METHODS:
Force was measured as knee extension torque; trophism by computer tomography scan; tissue composition and fiber morphology by histopathology and EM.
RESULTS:
In the long-term group of patients (17.0+/-2.6 years), force and size of thigh muscles were only slightly different from those of mid-term subjects (2.2+/-0.5 years). Histology and ultrastructure confirm that the difference in average size of muscle fibers between long-term and mid-term paralyzed leg muscles is actually very small. In addition, muscle fibers maintain the striated appearance characteristic of normal skeletal fibers even after 14-20 years of paralysis. Ultrastructural alterations of the activating and metabolic machineries, and the presence of fibers with lower motor neuron denervation features, may explain the low-force output and the reduced endurance of paretic muscles.
CONCLUSION:
The stable muscle atrophy that characterizes long-lasting spastic paraplegia suggests that there are no upper-time limits to begin a training program based on functional electrical stimulation.
PMID:
17955034
[PubMed - indexed for MEDLINE
Sull’ordine sequenziale di protasi e apodosi in italiano e russo nel corpus parallelo del NKRJa
No full textLo scopo di questo lavoro è verificare la posizione di protasi e apodosi in italiano e russo nel corpus parallelo italiano-russo del Corpus nazionale della lingua russa (Nacional’nyj Korpus Russkogo Jazyka - NKRJa) composto da testi scritti italiani e russi con le rispettive traduzioni. Per concentrare l’analisi sulla lingua contemporanea sono stati selezionati i soli testi di partenza pubblicati dal 1980 a oggi: si tratta per lo più di articoli di giornale, articoli del periodico della Camera di Commercio Italo-Russa, saggi scientifici e opere letterarie o estratti. La raccolta dei dati è stata effettuata cercando la congiunzione "se" nella sezione italiano-russo e "esli" nella sezione russo-italiano al fine di reperire i periodi ipotetici indipendentemente dalle diverse sottocategorie: sono infatti inclusi i bi-affermativi e i costrutti con protasi esprimente una condizione per la realizzazione dell’azione linguistica.
Nel contributo si propone una sintesi dei principali studi sull’ordine di comparsa delle frasi sovraordinate e subordinate, sulla sua rilevanza testual-discorsiva e su alcune tendenze e differenze interlinguistiche, per passare poi a descrivere l’ordine di comparsa di protasi e apodosi in italiano e in russo sulla base dei dati del corpus parallelo del NKRJa considerando anche la resa nei testi tradotti.The aim of this paper is to study the position of protasis and apodosis in Italian and Russian based on the data collected from the Russian-Italian parallel corpus. The use of parallel corpora for the analysis of interclausal and textual phenomena represents an innovative and fruitful approach.
The study is carried out on a subcorpus of texts published from 1980 to the present day. The texts consist primarily of newspaper articles, articles from the Russian-Italian Chamber of Commerce reviews, scientific essays and literary works or extracts.
The data were collected by searching for the conditional conjunction "se" in Italian source texts and "esli" in Russian source texts. All the subtypes of conditional constructions were thus considered, including the bi-affermative and those in which the protasis consists of a condition for the realisation of the linguistic act expressed by the apodosis (meta-discourse function).
The first part consists in a summary of all the main studies dealing with the order of main and subordinate clauses, on its textual-discursive relevance and on some interlinguistic trends and differences.
Subsequently, the order of protasis and apodosis in Italian and Russian is described, based on the data collected from the corpus. Following this, the way in which conditional constructions are translated in Italian and Russian target texts is considered
Long-Term Exercise Reduces Formation of Tubular Aggregates and Promotes Maintenance of Ca2+ Entry Units in Aged Muscle
No full textTubular aggregates (TAs) in skeletal muscle fibers are unusual accumulation of sarcoplasmic reticulum (SR) tubes that are found in different disorders including TA myopathy (TAM). TAM is a muscular disease characterized by muscle pain, cramping, and weakness that has been recently linked to mutations in STIM1 and ORAI1. STIM1 and ORAI1 are the two main proteins mediating store-operated Ca2+ entry (SOCE), a mechanism activated by depletion of intracellular Ca2+ stores (e.g., SR) that allows recovery of Ca2+ from the extracellular space during repetitive muscle activity. We have recently shown that exercise triggers the formation of unique intracellular junctions between SR and transverse tubules named Ca2+ entry units (CEUs). CEUs promote colocalization of STIM1 with ORAI1 and improve muscle function in presence of external Ca2+. TAs virtually identical to those of TAM patients are also found in fast-twitch fibers of aging male mice. Here, we used a combination of electron and confocal microscopy, Western blotting, and ex vivo stimulation protocols (in presence or absence of external Ca2+) to evaluate the presence of TAs, STIM1-ORAI1 localization and expression and fatigue resistance of intact extensor digitorum longus (EDL) muscles in wild-type male adult (4-month-old) and aged (24-month-old) mice and in mice trained in wheel cages for 15 months (from 9 to 24 months of age). The results collected indicate that (i) aging causes STIM1 and ORAI1 to accumulate in TAs and (ii) long-term exercise significantly reduced formation of TAs. In addition, (iii) EDL muscles from aged mice exhibited a faster decay of contractile force than adult muscles, likely caused by their inability to refill intracellular Ca2+ stores, and (iv) exercise in wheel cages restored the capability of aged EDL muscles to use external Ca2+ by promoting maintenance of CEUs. In conclusion, exercise prevented improper accumulation of STIM1 and ORAI1 in TAs during aging, maintaining the capability of aged muscle to refill intracellular Ca2+ stores via SOCE
Coordinated incorporation of skeletal muscle dihydropyridine receptors and ryanodine receptors in peripheral couplings of BC3H1 cells.
No full textRapid release of calcium from the sarcoplasmic reticulum (SR) of skeletal muscle fibers during excitation-contraction (e-c) coupling is initiated by the interaction of surface membrane calcium channels (dihydropyridine receptors; DHPRs) with the calcium release channels of the SR (ryanodine receptors; RyRs, or feet). We studied the early differentiation of calcium release units, which mediate this interaction, in BC(3)H1 cells. Immunofluorescence labelings of differentiating myocytes with antibodies against alpha(1) and alpha(2) subunits of DHPRs, RyRs, and triadin show that the skeletal isoforms of all four proteins are abundantly expressed upon differentiation, they appear concomitantly, and they are colocalized. The transverse tubular system is poorly organized, and thus clusters of e-c coupling proteins are predominantly located at the cell periphery. Freeze fracture analysis of the surface membrane reveals tetrads of large intramembrane particles, arranged in orderly arrays. These appear concomitantly with arrays of feet (RyRs) and with the appearance of DHPR/RyS clusters, confirming that the four components of the tetrads correspond to skeletal muscle DHPRs. The arrangement of tetrads and feet in developing junctions indicates that incorporation of DHPRs in junctional domains of the surface membrane proceeds gradually and is highly coordinated with the formation of RyR arrays. Within the arrays, tetrads are positioned at a spacing of twice the distance between the feet, The incorporation of individual DHPRs into tetrads occurs exclusively at positions corresponding to alternate feet, suggesting that the assembly of RyR arrays not only guides the assembly of tetrads but also determines their characteristic spacing in the junction
Store-operated calcium entry: From physiology to tubular aggregate myopathy
No full textStore-Operated Ca2+ entry (SOCE) is recognized as a key mechanism in muscle physiology necessary to refill intracellular Ca2+ stores during sustained muscle activity. For many years the cell structures expected to mediate SOCE in skeletal muscle fibres remained unknown. Recently, the identification of Ca2+ Entry Units (CEUs) in exercised muscle fibres opened new insights into the role of extracellular Ca2+ in muscle contraction and, more generally, in intracellular Ca2+ homeostasis. Accordingly, intracellular Ca2+ unbalance due to alterations in SOCE strictly correlates with muscle disfunction and disease. Mutations in proteins involved in SOCE (STIM1, ORAI1, and CASQ1) have been linked to tubular aggregate myopathy (TAM), a disease that causes muscle weakness and myalgia and is characterized by a typical accumulation of highly ordered and packed membrane tubules originated from the sarcoplasmic reticulum (SR). Achieving a full understanding of the molecular pathways activated by alterations in Ca2+ entry mechanisms is a necessary step to design effective therapies for human SOCE-related disorders
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