J. Karasinski

Training‐induced acceleration of O2 uptake on‐kinetics precedes muscle mitochondrial biogenesis in humans

•  What is the central question of this study? A few weeks of endurance training accelerate the oxygen uptake () on‐kinetics in humans. The main aim of the present study was to determine whether the acceleration of on‐kinetics obtained by a short period of moderate‐intensity training can be explained by an intensification of mitochondrial biogenesis. •  What is the main finding and its importance? We demonstrated that 5 weeks of moderate‐intensity training accelerates the on‐kinetics during moderate‐intensity cycling in the absence of enhanced mitochondrial biogenesis or capillarization in the trained muscles. We postulate that in the early stages of training an intensification of ‘parallel activation’ of oxidative phosphorylation could account for the shortening of the on‐transient.

Polymorphism of myosin isoenzymes and myosin heavy chains in histochemically typed skeletal muscles of the roach (Rutilus rutilus L., Cyprinidae, fish)

Abstract 1. 1. Muscle fibre types were identified histochemically by their actomyosin ATPase and SDH activities. 2. 2. Several myosin isoforms and a distict type of myosin heavy chain (MHC) were detected in red and white skeletal muscles as revealed by pyrophosphate and SDS gel electrophoreses. 3. 3 Results of an electrophoretic analysis of myosins are discussed in the light of their histochemical and functional properties.

Diversity of native myosin and myosin heavy chain in fish skeletal muscles

Abstract 1. 1. Polymorphism of native myosin and myosin heavy chain (MHC) of fish skeletal muscles was analysed by pyrophosphate and SDS-gel electrophoreses. 2. 2. Depending on the species, three or four myosin isoforms were detected in the white muscle, one or two isoforms in the pure red muscle, and four isomyosins were found in the red muscle composed of red and pink (intermediate) fibres. 3. 3. It is suggested that all main types of fish muscle fibre (red, intermediate and white) differ in myosin isoform content. 4. 4. Myosin heavy chain of the red muscle is a distinct protein from that of the white muscle. However, structural differences between these proteins vary among species.

Myosin isoenzymes of fish hearts

1. Myosin extracted from ventricular and atrial muscles of some fish species were analysed by native and SDS gel electrophoresis. 2. Within the single heart, distinct types of native myosin were present in ventricular and atrial tissues. 3. Ventricular and atrial isomyosins contained two classes of light chain subunits. 4. The present results support the suggestion that the presence of multiple molecular forms of myosin in the heart is a common property of all vertebrates.

Mechanisms of Attenuation of Pulmonary V'O2 Slow Component in Humans after Prolonged Endurance Training.

In this study we have examined the effect of prolonged endurance training program on the pulmonary oxygen uptake (V’O2) kinetics during heavy-intensity cycling-exercise and its impact on maximal cycling and running performance. Twelve healthy, physically active men (mean±SD: age 22.33±1.44 years, V’O2peak 3198±458 mL ∙ min-1) performed an endurance training composed mainly of moderate-intensity cycling, lasting 20 weeks. Training resulted in a decrease (by ~5%, P = 0.027) in V’O2 during prior low-intensity exercise (20 W) and in shortening of τp of the V’O2 on-kinetics (30.1±5.9 s vs. 25.4±1.5 s, P = 0.007) during subsequent heavy-intensity cycling. This was accompanied by a decrease of the slow component of V’O2 on-kinetics by 49% (P = 0.001) and a decrease in the end-exercise V’O2 by ~5% (P = 0.005). An increase (P = 0.02) in the vascular endothelial growth factor receptor 2 mRNA level and a tendency (P = 0.06) to higher capillary-to-fiber ratio in the vastus lateralis muscle were found after training (n = 11). No significant effect of training on the V’O2peak was found (P = 0.12). However, the power output reached at the lactate threshold increased by 19% (P = 0.01). The power output obtained at the V’O2peak increased by 14% (P = 0.003) and the time of 1,500-m performance decreased by 5% (P = 0.001). Computer modeling of the skeletal muscle bioenergetic system suggests that the training-induced decrease in the slow component of V’O2 on-kinetics found in the present study is mainly caused by two factors: an intensification of the each-step activation (ESA) of oxidative phosphorylation (OXPHOS) complexes after training and decrease in the ‘‘additional” ATP usage rising gradually during heavy-intensity exercise.

Myosin isoforms in selected muscle fibre types of the pond loach Misgurnus fossilis L.

Abstract The main types of muscle fibre in the pond loach lateral musculature—red, intermediate and white, distinguished histochemically by myofibrillar ATPase activity—differ in the composition of their native myosin isoforms. However, each of these fibre types expresses a single myosin heavy chain (MHC) of similar electrophoretic mobility. The small diameter fibres (referred to also as tonic-like) are distinct in myofibrillar ATPase activity and seem to contain the unique type of MHC, which suggests unique contractile properties for this fibre type.

Myosin isoenzymes of amphibian hearts

Cardiac myosins of 10 amphibian species were analysed by electrophoresis. Depending on the species, ventricles and atria contained one or two isomyosins. There were components similar to V2 or V1 of the rat and migrating faster. In the same heart, ventricular and atrial isomyosins were similar or tissue specific. It is suggested that the presence of multiple molecular forms of myosin in the heart is a common property of all vertebrates.

Contractile properties of motor units and expression of myosin heavy chain isoforms in rat fast-type muscle after volitional weight-lifting training.

Dynamic resistance training increases the force and speed of muscle contraction, but little is known about modifications to the contractile properties of the main physiological types of motor units (MUs) that contribute to these muscle adaptations. Although the contractile profile of MU muscle fibers is tightly coupled to myosin heavy chain (MyHC) protein expression, it is not well understood if MyHC transition is a prerequisite for modifications to the contractile characteristics of MUs. In this study, we examined MU contractile properties, the mRNA expression of MyHC, parvalbumin, and sarcoendoplasmic reticulum Ca2+ pump isoforms, as well as the MyHC protein content after 5 wk of volitional progressive weight-lifting training in the medial gastrocnemius muscle in rats. The training had no effect on MyHC profiling or Ca2+-handling protein gene expression. Maximum force increased in slow (by 49%) and fast (by 21%) MUs. Within fast MUs, the maximum force increased in most fatigue-resistant and intermediate but not most fatigable MUs. Twitch contraction time was shortened in slow and fast fatigue-resistant MUs. Twitch half-relaxation was shortened in fast most fatigue-resistant and intermediate MUs. The force-frequency curve shifted rightward in fast fatigue-resistant MUs. Fast fatigable MUs fatigued less within the initial 15 s while fast fatigue-resistant units increased the ability to potentiate the force within the first minute of the standard fatigue test. In conclusion, at the early stage of resistance training, modifications to the contractile characteristics of MUs appear in the absence of MyHC transition and the upregulation of Ca2+-handling genes.

Skeletal Muscle Myosin Heavy Chain Isoform Content in Relation to Gonadal Hormones and Anabolic-catabolic Balance in Trained and Untrained Men

Abstract Grandys, M, Majerczak, J, Karasinski, J, Kulpa, J, and Zoladz, JA. Skeletal muscle myosin heavy chain isoform content in relation to gonadal hormones and anabolic-catabolic balance in trained and untrained men. J Strength Cond Res 26(12): 3262–3269, 2012—Gonadal hormones and anabolic-catabolic hormone balance have potent influence on skeletal muscle tissue, but little is known about their action with regard to myosin heavy chain (MHC) transformation in humans. We investigated the relationship between skeletal muscle MHC isoform content in the vastus lateralis muscle and basal testosterone (T) concentration in 3 groups of subjects: endurance trained (E), sprint/strength trained (S), and untrained (U) young men. We have also determined basal sex hormone–binding globulin and cortisol (C) concentrations in untrained subjects to examine the relationship between MHC composition and the anabolic-catabolic hormone balance. Moreover, basal free testosterone (fT) and bioavailable testosterone (bio-T) concentrations were calculated for this subgroup. Despite significant differences in MHC isoform content (69.4 ± 2.39%, 61.4 ± 8.04%, and 37.5 ± 13.80% of MHC-2 for groups S, U, and E, respectively, Kruskal-Wallis: H = 18.58, p < 0.001), the T concentration was similar in the three groups of subjects (18.84 ± 5.73 nmol·L−1, 18.60 ± 5.73 nmol·L−1, and 20.73 ± 4.06 nmol·L−1 for U, E, and S groups, respectively, Kruskal-Wallis: H = 1.11, p > 0.5). We have also found that in the U group, type 2 MHC in the vastus lateralis muscle is positively correlated with basal fT:C ratio (r = 0.63, p = 0.01). It is concluded that the differences in the training history and training specificity can be distinguished with regard to the MHC composition but not with regard to the basal T concentration. Simultaneously, it has been shown that MHC isoform content in human vastus lateralis muscle may be related to basal anabolic-catabolic hormone balance, and this hypothesis needs further investigation.

Myosin polymorphism in fish cardiac muscles

Abstract 1. 1. Native myosin and myosin heavy chain of ventricular and atrial muscles of some teleost species were analysed electrophoretically. 2. 2. The presence of single isoforms of native myosin and myosin heavy chain in the whole ventricle of carp, tench, pike and rainbow trout suggests that both layers of ventricular myocardium (compact and spongious) express similar, or even the same, myosin. 3. 3. Ventricle and atrium contain distinct isoforms of native myosin and/or myosin heavy chain. It is suggested that differences in MHC content in ventricular and atrial myocardium may imply different contractile properties of these muscles.