Browsing by Author "Joumaa, Venus"

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    5th Rocky Mountain Muscle Symposium
    (Faculty of Kinesiology, 2023-05-19) Joumaa, Venus; Hessel, Anthony; Nishikawa, Kiisa; Millard, Matthew; Han, Seong-won; Bell, Kaylyn; Leonard, Tim; Kaya, Motoshi; Corr, David; Swank, Douglas; Corvelyn, Marlies; Sahani, Ridhi; Mazara, Nicole; Moo, Eng Kuan; Granzier, Henk; Oldshue, Ashley; Adkins, Amy; Loya, Amy; Boldt, Kevin; Desloovere, Kaat; Fukutani, Atsuki; Martino, Giovanni; De Beukelaer, Nathalie; Horslen, Brian; Agen, Anouk; Costamanga, Domiziana; Swank, Doug; Holt, Natalie
    Proceedings from the 4th Rocky Mountain Muscle Symposium, Canmore Nordic Centre, June 19-21, 2023.
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    Calcium sensitivity of residual force enhancement in rabbit skinned fibers
    (American Journal of Physiology, 2014-08-15) Joumaa, Venus; Herzog, Walter
    Isometric force after active stretch of muscles is higher than the purely isometric force at the corresponding length. This property is termed residual force enhancement. Active force in skeletal muscle depends on calcium attachment characteristics to the regulatory proteins. Passive force has been shown to influence calcium attachment characteristics, specifically the sarcomere length dependence of calcium sensitivity. Since one of the mechanisms proposed to explain residual force enhancement is the increase in passive force that results from engagement of titin upon activation and stretch, our aim was to test if calcium sensitivity of residual force enhancement was different from that of its corresponding purely isometric contraction and if such a difference was related to the molecular spring titin. Force-pCa curves were established in rabbit psoas skinned fibers for reference and residual force-enhanced states at a sarcomere length of 3.0 μm 1) in a titin-intact condition, 2) after treatment with trypsin to partially eliminate titin, and 3) after treatment with trypsin and osmotic compression with dextran T-500 to decrease the lattice spacing in the absence of titin. The force-pCa curves of residual force enhancement were shifted to the left compared with their corresponding controls in titin-intact fibers, indicating increased calcium sensitivity. No difference in calcium sensitivity was observed between reference and residual force-enhanced contractions in trypsin-treated and osmotically compressed trypsin-treated fibers. Furthermore, calcium sensitivity after osmotic compression was lower than that observed for residual force enhancement in titin-intact skinned fibers. These results suggest that titin-based passive force regulates the increase in calcium sensitivity of residual force enhancement by a mechanism other than reduction of the myofilament lattice spacing.
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    Gaining New Understanding of Sarcomere Length Nonuniformities in Skeletal Muscles
    (2023-09-28) Li, Meng; Herzog, Walter; Syme, Douglas; Joumaa, Venus
    Sarcomere lengths are non-uniform on all structural levels of mammalian skeletal muscle. These non-uniformities have been associated with a variety of mechanical properties, including residual force enhancement and depression, creep, increased force capacity, and extension of the plateau of the force-length relationship. However, the nature of sarcomere length non-uniformities has not been explored systematically. The purpose of this study was to determine the properties of sarcomere length non-uniformities in active and passive muscle. Single myofibrils of rabbit psoas (n=20; with 412 individual sarcomeres) were subjected to three activation/deactivation cycles at short, intermediate, and long sarcomere lengths of 2.7, 3.2, and 3.6 µm respectively, and individual sarcomere lengths were measured at 4 passive and 3 active points during the activation/deactivation cycles. The primary results were that sarcomere length non-uniformities did not occur randomly but were governed by some structural and/or contractile properties of the sarcomeres and that sarcomere length non-uniformities differed greatly between the active and passive state. We propose that the mechanisms that govern the systematic sarcomere lengths non-uniformities observed in active and passive muscle are associated with the variable number of contractile proteins and the variable number and stiffness of titin filaments in individual sarcomeres.
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    Intermittent stretch training of rabbit plantarflexor muscles increases soleus mass and serial sarcomere number
    (American Physiology Society, 2015-06-15) De Jaeger, Dominique; Joumaa, Venus; Herzog, Walter
    In humans, enhanced joint range of motion is observed after static stretch training and results either from an increased stretch tolerance or from a change in the biomechanical properties of the muscle-tendon unit. We investigated the effects of an intermittent stretch training on muscle biomechanical and structural variables. The left plantarflexors muscles of seven anesthetized New Zealand (NZ) White rabbits were passively and statically stretched three times a week for 4 wk, while the corresponding right muscles were used as nonstretched contralateral controls. Before and after the stretching protocol, passive torque produced by the left plantarflexor muscles as a function of the ankle angle was measured. The left and right plantarflexor muscles were harvested from dead rabbits and used to quantify possible changes in muscle structure. Significant mass and serial sarcomere number increases were observed in the stretched soleus but not in the plantaris or medial gastrocnemius. This difference in adaptation between the plantarflexors is thought to be the result of their different fiber type composition and pennation angles. Neither titin isoform nor collagen amount was modified in the stretched compared with the control soleus muscle. Passive torque developed during ankle dorsiflexion was not modified after the stretch training on average, but was decreased in five of the seven experimental rabbits. Thus, an intermittent stretching program similar to those used in humans can produce a change in the muscle structure of NZ White rabbits, which was associated in some rabbits with a change in the biomechanical properties of the muscle-tendon unit.
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    Mechanical Adaptations of Skinned Cardiac Muscle in Response to Dietary-Induced Obesity During Adolescence in Rats
    (Canadian Science Publishing, 2020-03-05) Boldt, Kevin; Joumaa, Venus; Herzog, Walter; MacDonald, Graham
    Childhood obesity is a major risk factor for heart disease during adulthood, independent of adulthood behaviours. Therefore, it seems that childhood obesity leads to partly irreversible decrements in cardiac function. Little is known about how obesity during maturation affects the mechanical properties of the heart. The purpose of this study was to evaluate contractile properties in developing hearts from animals with dietary-induced obesity (high-fat high-sucrose diet (HFHS)). We hypothesized that obesity induced during adolescence results in decrements in cardiac contractile function. Three-week old rats (n=16) were randomized into control (chow) or dietary-induced obesity (HFHS) groups. Following 14 weeks on the diet, skinned cardiac trabeculae fibre bundle testing was performed to evaluate active and passive force, maximum shortening velocity, and calcium sensitivity. Rats in the HFHS group had significantly larger body mass and total body fat percentage. There were no differences in maximal active or passive properties of hearts between groups. Hearts from HFHS group rats had significantly slower maximum shortening and lower calcium sensitivity than controls. Decreased shortening velocity and calcium sensitivity in hearts of obese animals may constitute increased risk of cardiac disease in adulthood. Novelty Bullets • Cardiac muscle from animals exposed to an obesogenic diet during development had lower shortening velocity and calcium sensitivity than those from animals fed a chow diet. • These alterations in mechanical function may be a mechanism for the increased risk of cardiac disease observed in adulthood.
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    The mechanical and biochemical properties of tail tendon in a rat model of obesity: effect of moderate exercise and prebiotic fibre supplementation
    (2019-05-09) Rios, Jaqueline Lourdes; Ko, Loretta; Joumaa, Venus; Liu, Shuyue; Diefenthaeler, Fernando; Sawatsky, Andrew; Hart, David A.; Reimer, Raylene A.; Herzog, Walter
    The worldwide trajectory of increasing obesity rates is a major health problem precipitating a rise in the prevalence of a variety of co-morbidities and chronic diseases. Tendinopathy, in weight and non-weight bearing tendons, in individuals with overweight or obesity has been linked to metabolic dysfunction resulting from obesity. Exercise and dietary fibre supplementation (DFS) are common countermeasures to combat obesity and therefore it seems reasonable to assume that they might protect tendons from structural and mechanical damage in a diet-induced obesity (DIO) model. The purpose of this study was to determine the effects of a DIO, DIO combined with moderate exercise, DIO combined with DFS (prebiotic oligofructose), and DIO combined with moderate exercise and DFS on the mechanical and biochemical properties of the rat tail tendon. Twenty-four male Sprague-Dawley rats, fed a high-fat/high-sucrose diet were randomized into a sedentary, a moderate exercise, a DFS, or a moderate exercise combined with DFS group for 12 weeks. Additionally, six lean age-matched animals were included as a sedentary control group. DIO in combination with exercise alone and with exercise and DFS reduced the Young's Modulus but not the collagen content of the rat tail tendons compared to lean control animals. However, no differences in the mechanical and biochemical properties of the rat tail tendon were detected between the DIO and the lean control group, suggesting that DIO by itself did not impact the tail tendon. It seems that longer DIO exposure periods may be needed to develop overt differences in our DIO model.
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    Mechanical and Structural Remodeling of Cardiac Muscle Following Aerobic and Resistance Exercise Training in Rats
    (2020-05-07) Boldt, Kevin; Joumaa, Venus; Turnbull, Jeannine; Fedak, Paul; Herzog, Walter
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    Proceedings of the 4th Rocky Mountain Muscle Symposium
    (2019-07-27) Joumaa, Venus; Hessel, Anthony; Nishikawa, Kiisa; Millard, Matthew; Han, Seong-won; Bell, Kaylyn; Leonard, Tim; Corr, David; Swank, Douglas; Corvelyn, Marlies; Sahani, Ridhi; Mazara, Nicole; Moo, Eng Kuan; Lieber, Rick; Kaya, Motoshi; Granzier, Henk; Oldshue, Ashley; Adkins, Amy; Loya, Amy; Boldt, Kevin; Desloovere, Kaat; Fukutani, Atsuki; Martino, Giovanni; De Beukelaer, Nathalie; Horslen, Brian; Agten, Anouk; Costamagna, Domiziana; Lee, Sabrina; Schwaner, Marie Janneke; Abbott, Emily; Binder-Markey, Benjamin; Siebert, Tobias; Lin, David; Fontana, Heiliane de Brito; Daley, Monica; Hahn, Daniel; Evangelidis, Pavlos; Knaus, Katherine; Smith, Ian; Deloovere, Kat; Kawakami, Yasuo; Hodson-Tole, Emma; Oliveira, Liliam; Ichinose, Hoshizora; Tillin, Neale; Raiteri, Brent; Seiberl, Wolfgang; Vaz, Marco; Cruz-Montecinos, Carlos; Griffiths, Robert; MacIntosh, Brian; Lourdes Rios, Jacqueline; Bossuyt, Fransiska
    Proceedings from the 4th Rocky Mountain Muscle Symposium, Canmore Nordic Centre, July 27-29, 2019
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    Relationship of muscle morphology to hip displacement in cerebral palsy: a pilot study investigating changes intrinsic to the sarcomere
    (2019-06-21) Larkin-Kaiser, Kelly A; Howard, Jason J; Leonard, Timothy; Joumaa, Venus; Gauthier, Luke; Logan, Karl; Orlik, Benjamin; El-Hawary, Ron; Herzog, Walter
    Abstract Background Cerebral palsy (CP) is the most common cause of childhood disability, typified by a static encephalopathy with peripheral musculoskeletal manifestations—most commonly related to spasticity—that are progressive with age. Hip displacement is one of the most common manifestations, observed to lead to painful degenerative arthritis over time. Despite the key role that spasticity-related adductor muscle contractures are thought to play in the development of hip displacement in CP, basic science research in this area to date has been limited. This study was initiated to correlate hip adductor muscle changes intrinsic to the sarcomere—specifically, titin isoforms and sarcomere length—to the severity of hip displacement in children with spastic cerebral palsy. Methods Single gracilis muscle biopsies were obtained from children with CP (Gross Motor Function Classification System (GMFCS) III-V; n = 10) who underwent adductor muscle release surgery for the treatment of hip displacement. Gel electrophoresis was used to estimate titin molecular weight. Sarcomere lengths were measured from muscle fascicles using laser diffraction. The severity of hip displacement was determined by measuring by Reimers migration percentage (MP) from anteroposterior pelvic x-rays. Correlation analyses between titin, sarcomere lengths, and MP were performed. Results The mean molecular weight of titin was 3588 kDa. The mean sarcomere length was 3.51 μm. Increased MP was found to be associated with heavier isoforms of titin (R2 = 0.65, p < 0.05) and with increased sarcomere lengths (R2 = 0.65, p < 0.05). Heavier isoforms of titin were also associated with increased sarcomere lengths (R2 = 0.80, p < 0.05). Conclusions Our results suggest that both larger titin isoforms and sarcomere lengths are positively correlated with increased severity of hip displacement and may represent adaptations in response to concomitant increases in spasticity and muscle shortening. Trial registration As this study does not report the results of a health care intervention on human participants, it has not been registered.
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    Stiffness of Hip Adductor Myofibrils is decreased in Children with Spastic Cerebral Palsy
    (Elsevier, 2019-02-23) Leonard, Timothy R.; Howard, Jason J.; Larkin-Kaiser, Kelly A.; Joumaa, Venus; Logan, Karl J.; Orlik, Benjamin; El-Hawary, Ron; Gauthier, Luke E.; Herzog, Walter
    Cerebral palsy (CP) is the result of a static brain lesion which causes spasticity and muscle contracture. The source of the increased passive stiffness in patients is not understood and while whole muscle down to single muscle fibres have been investigated, the smallest functional unit of muscle (the sarcomere) has not been. Muscle biopsies (adductor longus and gracilis) from pediatric patients were obtained (CP n=9 and control n=2) and analyzed for mechanical stiffness, in-vivo sarcomere length and titin isoforms. Adductor longus muscle was the focus of this study and the results for sarcomere length showed a significant increase in length for CP (3.6µm) compared to controls (2.6µm). Passive stress at the same sarcomere length for CP compared to control was significantly lower in CP and the elastic modulus for the physiological range of muscle was lower in CP compared to control (98.2kPa and 166.1kPa, respectively). Our results show that CP muscle at its most reduced level (the myofibril) is more compliant compared to normal , which is completely opposite to what is observed at higher structural levels (single fibres, muscle fibre bundles and whole muscle). It is noteworthy that at the in vivo sarcomere length in CP, the passive forces are greater than normal, purely as a functional of these more compliant sarcomeres operating at long lengths. Titin isoforms were not different between CP and non-CP adductor longus but titin:nebulin was reduced in CP muscle, which may be due to titin loss or an over-expression of nebulin in CP muscles.
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    The Effects Of Increased Stimulation On Sarcomere Number
    (2016) Engel, Maria; Herzog, Walter; Joumaa, Venus; Syme, Douglas; Schmidt, Tannin; Butterfield, Timothy
    Tabary et al. (1981) accelerated serial sarcomere loss by applying electrical stimulation, resulting in a 25% decrease in sarcomere number (SN) in the guinea pig soleus muscle within 12 hours. A duplication of these results was attempted in our laboratory. Rabbit lower hind limb muscles were stimulated for 10 hours continuously. As a result, muscles lost approximately 25% of sarcomeres in series. During laser diffraction analysis, it was observed that the first order diffraction band was wider in experimental compared to control muscles, implying some form of non-uniformity within the fascicle. Therefore, sarcomere length non-uniformity and structural disorganization was analyzed using light microscopy. Electrical stimulation indeed caused an increase in SL nonuniformity. In an attempt to examine the possibility of sarcomere loss in a more clinically relevant environment, muscle morphology and SN was analyzed in the genetically spastic mouse. The gastrocnemius muscle was shorter, but SN was generally unchanged.
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    The three filament model of skeletal muscle stability and force production
    (Tech Science Press, 2012-01) Herzog, Walter; Leonard, Timothy R.; Joumaa, Venus; DuVall, Michael M.; Panchangam, Appaji
    Ever since the 1950s, muscle force regulation has been associated with the cross-bridge interactions between the two contractile filaments, actin and myosin. This gave rise to what is referred to as the "two-filament sarcomere model". This model does not predict eccentric muscle contractions well, produces instability of myosin alignment and force production on the descending limb of the force-length relationship, and cannot account for the vastly decreased ATP requirements of actively stretched muscles. Over the past decade, we and others, identified that a third myofilament, titin, plays an important role in stabilizing the sarcomere and the myosin filament. Here, we demonstrate additionally how titin is an active participant in muscle force regulation by changing its stiffness in an activation/force dependent manner and by binding to actin, thereby adjusting its free spring length. Therefore, we propose that skeletal muscle force regulation is based on a three filament model that includes titin, rather than a two filament model consisting only of actin and myosin filaments consisting only of actin and myosin filaments