We examined muscle spindles in the posterior cricoarytenoid (PCA) muscle of the marmoset. The spindle capsule contained only one intrafusal muscle fiber which did not form a typical aggregation of equatorial nuclei such as bags and chains. The intrafusal fiber was innervated by sensory endings which branched and arranged irregularly. These sensory endings lay on the surface of the fiber in shal...

PURPOSE To examine the effect of α-actinin-3 deficiency due to homozygosity for the ACTN3 577X-allele on contractile and morphological properties of fast muscle fibers in non-athletic young men. METHODS A biopsy was taken from the vastus lateralis of 4 RR and 4 XX individuals to test for differences in morphologic and contractile properties of single muscle fibers. The cross-sectional area of...

OBJECTIVE We investigated whether alterations of glycolytic and oxidative enzyme capacity in skeletal muscle of patients with type 2 diabetes pertain to specific muscle fibers and are associated with changes in muscle fiber composition. RESEARCH DESIGN AND METHODS Vastus lateralis muscle was obtained by percutaneous biopsy from 10 patients with type 2 diabetes and 15 age- and BMI-matched heal...

The aim of this study was to determine whether capillarity in the denervated and reinnervated rat extensor digitorum longus muscle (EDL) is scaled by muscle fiber oxidative potential. We visualized capillaries adjacent to a metabolically defined fiber type and estimated capillarity of fibers with very high oxidative potential (O) vs fibers with very low oxidative potential (G). Capillaries and ...

The effects of long-term (over several years) anabolic androgen steroids (AAS) administration on human skeletal muscle are still unclear. In this study, seventeen strength training athletes were recruited and individually interviewed regarding self-administration of banned substances. Ten subjects admitted having taken AAS or AAS derivatives for the past 5 to 15 years (Doped) and the dosage and...

Introduction The organization of skeletal muscle fibers, or muscle architecture, strongly determines the muscle’s maximum force capacity [1]. Diffusion tensor imaging (DTI), widely used in brain studies, has recently emerged as an attractive tool for investigating the microstructure of skeletal muscle. In this latter, DTI provides information about the water molecules self-diffusion which is re...

Fluorescence polarization was used to examine orientation changes of two rhodamine probes bound to myosin heads in skeletal muscle fibers. Chicken gizzard myosin regulatory light chain (RLC) was labeled at Cys108 with either the 5- or the 6-isomer of iodoacetamidotetramethylrhodamine (IATR). Labeled RLC (termed Cys108-5 or Cys108-6) was exchanged for the endogenous RLC in single, skinned fibers...

The maximum tetanic tension (Po) generated by a skeletal muscle is determined by its functional cross-sectional area (CSA) and its specific tension (tension/CSA). Measurements of average fiber length (normalized to a sarcomere length of 2.2 micron), muscle mass, and approximate angle of pinnation of muscle fibers within a muscle were taken from 26 different guinea pig hindlimb muscles and were ...

BAGBY, GREGORY J., WALTER L. SEMBROWICH, AND PHILIP D. GOLLNICK. Myosin A TPase and fiber composition from trained and untrained rat skeletal muscle. Am. J. Physiol. 223(6): 1415-1417. 1972.-Myosin ATPase and fiber composition were determined in the gastrocnemius muscle of sedentary, endurance-trained, and sprint-trained rats. The endurance training was running in motordriven wheels 60 min/day ...

The purpose of this investigation was to characterize the effects of marathon training on single muscle fiber contractile function in a group of recreational runners. Muscle biopsies were obtained from the gastrocnemius muscle of seven individuals (22 +/- 1 yr, 177 +/- 3 cm, and 68 +/- 2 kg) before, after 13 wk of run training, and after 3 wk of taper. Slow-twitch myosin heavy chain [(MHC) I] a...