Abstract The dihydropyridine receptor (DHPR) in the skeletal muscle plasma membrane functions as a voltage sensor for excitation-contraction coupling. In the present work the expression and special features of DHPR were studied under various conditions. In order to localize and visualize the DHPRs, a method using fluorophore-conjugated dihydropyridine molecules as a probe was developed. In addition, different laboratory assays and electrophysiological measurements were used to study the expression of the myofibrillar proteins, force production of the muscle and conduction velocity of the plasma membrane. During the postnatal development of mouse skeletal muscle the density of DHPR increased. By the time of DHPR appearance, the expression of sodium channels had started and the typical assembly of basic structural components and membrane compartments was clearly detectable. According to the histochemical analysis, the DHPR was selectively expressed in type IIA muscle fibres of mouse. In addition to the fibre type specificity, the uneven distribution of DHPRs was also seen at the muscle level. The attenuation of the contraction force after addition of DHPR blocker was largest in muscles with a high percentage of type IIA fibres. In fish muscles, the distribution of DHPR was homogenous and the density between different fibre types was quite similar. In gastrocnemius muscle of mouse, the density and mRNA expression of DHPR increased significantly by 21.5 and 66.8%, respectively, after a 15-week aerobic exercise programme. The increase correlated significantly with the raise in % myosin heavy chain IIa isoform. In thigh and heart muscles, no significant changes were observed. In fish, the environmental change following hatchery release and downstream migration of 46.5 km induced an increase in the DHPR density in swimming muscles. Furthermore, a transition of phenotypic profile from fast-to-slow fibres was observed. Taken together, the present data provide evidence for the fact that the expression of DHPR increases during postnatal development. Moreover, the expression correlates with a specific fibre-type metabolism, thus having an impact on the overall contractile properties of the muscle. This is further manifested as an increase in the DHPR density after endurance training in mammalian as well as in fish muscle. In addition, a strong correlation exists between the level of muscle activity and the density of DHPR. / Tiivistelmä Poikkijuovaisen lihaksen solukalvolla esiintyvä dihydropyridiini (DHP) reseptori toimii jännitesensorina lihaksen ärsytys-supistus kytkennässä. Tässä työssä tutkittiin DHP reseptorin erityispiirteitä sekä erilaisten fysiologisten tekijöiden vaikutusta reseptorin ilmenemiseen. DHP reseptorien visualisointiin kehitettiin histologinen värjäysmenetelmä, jossa merkkiaineena toimi fluorofori-konjugoitu DHP molekyyli. Lisäksi työssä tutkittiin lihaksen proteiinien ekspressiota, lihaksen voimantuottoa sekä solukalvon johtonopeutta erilaisten määritysmenetelmien ja elektrofysiologisten mittausmenetelmien avulla. Tulokset osoittivat, että yksilönkehityksen aikana DHP reseptorien tiheys kasvoi hiiren poikkijuovaisessa lihaksessa. DHP reseptorien ekspression alkaessa natriumkanavat olivat jo ilmaantuneet solukalvolle ja lihassolun rakenne oli pitkälle erilaistunut. Histokemiallisten määritysten perusteella DHP reseptorin ekspressio oli selektiivistä. Reseptoreita esiintyi runsaimmin tyypin IIA soluissa. Reseptoriproteiinin solutyyppispesifisyys oli huomattavissa myös lihastasolla. Tulosten mukaan proteiinin salpaaja alensi lihaksen supistumisvoimaa erityisesti niissä hiiren lihaksissa, joiden solutyyppikoostumuksessa tyypillä IIA on suuri prosentuaalinen osuus. Kalan lihaksissa DHP reseptorit olivat homogeenisesti jakautuneet. Lisäksi reseptoritiheys oli samankaltainen eri solutyyppien välillä. 15 viikon aerobinen harjoittelu lisäsi sekä DHP reseptorin proteiini- että mRNA- ekspressiota tilastollisesti merkitsevästi (21,5 ja 66,8 %) hiiren kantalihaksessa. Ekspression kasvu korreloi merkitsevästi samanaikaisesti tapahtuneen myosiini isomuoto IIa määrän kasvun kanssa. Reisi- ja sydänlihaksessa merkittäviä muutoksia ei havaittu. Kalan uintilihaksissa DHP reseptorien tiheys kasvoi vapauttamisen jälkeisen ympäristön muutoksen ja 46,5 km pituisen vaelluksen jälkeen. Lisäksi lihasten solutyyppikoostumuksessa tapahtui muutos kohti hitaasti supistuvia solutyyppejä. Yhteenvetona voidaan todeta, että saatujen tulosten perusteella DHP reseptorien ekspressio kasvaa syntymän jälkeen hiiren poikkijuovaisessa lihaksessa. Solujen erilaistuessa ekspressio korreloi solutyyppimetabolian kanssa vaikuttaen edelleen lihaksen supistumisominaisuuksiin. Tästä johtuen myös kestävyysharjoittelun seurauksena DHP reseptorien määrä kasvaa sekä nisäkkään että kalan lihaksissa. Erityisesti lihaksen aktiivisuudella on merkitystä DHP reseptorin ekspressioon.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Background: The presence of muscular deficiency seems to be a major cause of back pain that requires counteractions. Considering that the autochthonous back muscles, responsible for straightening and stabilizing the spine, cannot be activated voluntarily, they can be strengthened only through specific training. The computer-supported test and training system (CTT) Centaur (BfMC GmbH, Leipzig, SN, Germany) seems well suited for this purpose. To show its potential as a reliable diagnostic and training tool, this study aimed to evaluate the test-retest reliability of this 3D spatial rotation device. Methods: A prospective pilot study was conducted in 20 healthy volunteers of both sexes. For test-retest reliability analysis, three measurements were performed with a two-day interval between each measurement. Each measurement consisted of a one-minute endurance test performed in eight different positions (transverse plane). During the test, the subject was tilted by 90° in the sagittal plane from a neutral, upright position. Meanwhile, the subject's level of upper body stabilization along the body axis was assessed. All trunk movements (momentum values) were quantified by a multicomponent force sensor and standardized relative to the subject's upper body mass. The range of motion was assessed by 95% confidence ellipse analysis. Here, all position-specific confidence ellipses for each measurement were merged to a summarized quantity. Finally, ICC analysis using a single-rating, absolute agreement, two-way mixed-effects model and a Bland-Altman plot was performed to determine the reliability. Results: Considering all measurements (t1, t2, t3), the ICC for reliability evaluation was 0.805, and the corresponding 95% confidence interval (CI) was [0.643, 0.910]. Moreover, the Bland-Altman plots for all three pairs of time points did not show significant differences. Conclusion: This study concludes that the CTT Centaur shows good test-retest reliability, indicating it can be used in clinical practice in the future.

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The physical exercise is fundamentally important for the individual's life and health. The physical inactivity and/or low physical conditioning, on the other hand, has been considered one of the risk factors of premature mortality with deleterious effects similar to other deseases, such as high blood pressure and dyslipidemia. Among the different types of exercises the resisted exercise (anaerobic) promotes positive changes in bodily composition, treatment and prevention of deseases in several populations, as well as improvement in physical aptitude. This modality is characterized by muscle tension (possessing or not articulated movement) against some resistance to muscle action. In that sense, na experiment was carried out with forty wistar rats divided into four groups weighing between 250g-300g. They were submitted to resisted exercise and it was administrated glucocorticoid (dexomenthasone 0,2 mg/kg/day). It was possible to observe that there was no significant difference in the rats' body weight under medication and trained. A gain in soleus muscle mass was evidenced after the training period (28,33% and 25,29% for the trained and dexa-trained control groups, respectively), as well as the decrease in perigonous fat (26,6% and 24% for the trained and dexa-trained control groups, respectively). The results suggest that resisted exercises improve the skeletical musculature and consequently the decrease in the fat mass. Moreover, the main finding of this study was the soleum muscle hypertrophy, which needs more studies that clarify such mechanism. / O exercício físico é de fundamental importância na vida e na saúde dos indivíduos. Dentre os diferentes tipos de exercícios, o exercício resistido promove alterações positivas na composição corporal, tratamento e prevenção de doenças em diversas populações assim como melhora na aptidão física. Esta modalidade é caracterizada pela tensão muscular (possuindo ou não movimento articular) contra alguma resistência a ação muscular. Objetivo do estudo consistiu em analisar os efeitos do exercício resistido na composição corporal dos ratos tratados com dexametasona. Foram utilizados 40 ratos wistar divididos em quatro grupos (SS-salina sedentário, ST-salina treinado, DS- dexa sedentário, DT- dexa treinado), pesando entre 250-300g, acondicionados em caixas com acesso livre a água e comida e em sistema ciclo claro-escuro. Os grupos treinados (ST e DT) foram submetidos ao exercício resistido e os grupos DS e DT administrado glicocorticoide (dexametasona 0,2 mg/kg/dia). Foi possível observar que não houve diferença significativa no peso corporal nos ratos sob medicação e treinados. Um ganho de massa muscular do sóleo foi evidenciada após o período de treinamento (28,33% e 25,29%, para os grupos controle treinado e dexa treinado, respectivamente), assim como a diminuição da gordura perigonadal (26,6% e 24%, para os grupos controle treinado e dexa treinado, respectivamente). Os resultados sugerem que o exercício resistido melhora a musculatura esquelética e consequentemente a diminuição da massa gorda. Além disso, o principal achado deste estudo foi a hipertrofia do músculo sóleo. / São Cristóvão, SE

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Collision avoidance systems have become an integrated part of modern vehicles and aim to avoid accidents or mitigate the crash severity for the occupant. For example, the autonomous emergency braking system influences the pre-crash state of the occupant in sitting posture, stress state, or velocity. The occupant might try to retain its posture by activating muscles, which induce muscle bracing and could counteract the movement of the occupant in the pre-crash phase.  Therefore, it is essential to study the influence of active musculature on occupant response in pre-crash and crash events. A finite element human body model (HBM) with and without closed-loop muscle activation control was used to simulate the occupant response during those events. Comparing the HBM responses & head kinematics reveal an influence of muscle bracing in the evasive braking manoeuvre. Simulating the pre-crash and in-crash phase in two stages can provide multiple benefits. However, the correlation between a single-stage simulation (baseline) and a two-stage simulation needs to be investigated. The baseline simulation uses an active HBM to model an occupant during an evasive braking manoeuvre and the muscles are deactivated when entering the frontal impact phase. The parameters of the final pre-crash state, which are needed to mimic the baseline’s response when transitioning from the pre-crash to the in-crash event are investigated in this study. For that reason, sitting position, stress state and velocity are transferred respectively to the initial passive in-crash HBM state. The simulations enabled the comparison of occupant response and calculation of cross-correlation. Each retainment strategy gave a good cross-correlation with the baseline simulation. / Kollisionsundvikande system har blivit en viktig del i moderna fordon där syftet är att undvika olyckor samt att minska allvarhetsgraden av olyckor för de åkande. Ett exempel är nödbromssystem som kan påverka den åkandes initiala tillstånd direkt före en krock som, till exempel, sittposition, spänningstillstånd, eller initial hastighet inför krock. Den åkande kan försöka att bibehålla sin hållning genom att aktivera sina muskler vilket påverkar rörelsen av dess kropp under för-krocks fasen. Det är därför viktigt att studera hur aktiva muskler påverkar rörelsen av kroppen hos den åkande under både före krocksfasen och själva krockfasen. En finit element humanmodell (HBM) med och utan reglerad muskelaktivitet används för att prediktera responsen hos den åkande i båda faserna. En jämförelse mellan simuleringarna visar att aktiva muskler kan påverka åkandekinematiken under bromsningsförloppet. Att simulera fasen före krock och fasen under krock i två steg kan medföra flera fördelar. Korrelationen mellan en enkelstegssimulering (originalsimulering) och en tvåstegssimulering måste dock studeras. Som originalsimulering används en aktiv HBM för att modellera den åkande under för-krocksfasen där den reglerade muskelaktiviteten inaktiveras under krockfasen. I denna studie undersöks den åkandes initiala tillstånd före krocken som behövs för att efterlikna originalsimulerings respons vid övergången från för-krocksfasen till krockfasen. Av den anledningen mappas det passiva HBM-tillståndet till det slutliga tillståndet av före krocksfasen för sittposition, spänningstillstånd respektive hastighet. Simuleringarna möjliggjorde en jämförelse av åkande respons och beräkning av korskorrelation. Varje mappningsstrategi gav en bra korskorrelation med originalsimuleringen.