Gaster, M., P. Poulsen, A. Handberg, H. D. Schrøder, and H. Beck-Nielsen. Direct evidence of fiber type-dependent GLUT-4 expression in human skeletal muscle. Am J Physiol Endocrinol Metab 278: E910–E916, 2000.—GLUT-4 expression in individual fibers of human skeletal muscles in younger and older adults was studied. Furthermore, the dependency of insulin-stimulated glucose uptake on fiber type di...

1. A method of isolation of individual afferent fibers from muscle has yielded a representative sample of the fibers which comprise groups 1 (12 to 20 micro) and II (4 to 12 micro) of the afferent fiber diameter distribution of muscle nerves in cat. 2. Afferent fibers from muscle stretch receptors account for groups I and II of the afferent diameter spectrum of muscle nerves to soleus and media...

In skeletal muscle fibers, action potentials elicit contractions by releasing calcium ions (Ca(2+)) from the sarcoplasmic reticulum. Experiments on individual mouse muscle fibers micro-injected with a rapidly responding fluorescent Ca(2+) indicator dye reveal that the amount of Ca(2+) released is three- to fourfold larger in fast-twitch fibers than in slow-twitch fibers, and the proportion of t...

We have previously shown that the N-terminal sequence AcEEED of alpha-smooth-muscle actin causes the loss of alpha-smooth-muscle actin from stress fibers and a decrease in cell contractility when introduced in myofibroblasts as a cell-penetrating fusion peptide. Here, we have investigated the function of this sequence on stress fiber organization in living cells, using enhanced green fluorescen...

Repetitive muscle contraction is associated with increased superoxide production in skeletal muscle. 1-8 There is considerable evidence that muscle fatigue during prolonged exercise is associated with oxidant stress in muscle fibers, and that this stress is indeed partially responsible for the fatigue. Thus, pharmacological strategies which depress the antioxidant defenses of muscle fibers acce...

The fine structure of the lateral rectus muscle in the rhesus monkey was compared with that of the palmar interosseus muscle. Since the interosseus possessed muscle spindles, it was classified into extraand intrafusal muscle fibers. Although both of these fibers corresponded to the twitch fiber, the intrafusal fibers were smaller in diameter (15 to 30(i) than the extrafusal (50 to 60fi), and bo...

The objective of this study was to determine the effects of postmortem muscle pH and temperature declines on the actomyosin ATPase activity of muscle fibers expressing different MyHC isoforms. Using a quantitative histochemical procedure to determine ATPase activity, the maximum actomyosin ATPase activity was determined on individual fibers classified by MyHC expression. Samples were collected ...

Individual skeletal muscles in the animal body are heterogeneous, as each is comprised of different fiber types. Type I muscle fibers are rich with mitochondria, and have high oxidative metabolisms while type IIB fibers have few mitochondria and high glycolytic metabolic capacity. Peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), a transcriptional co-activator that regul...

Muscle fibers are dynamic structures capable of altering their phenotype under various pathological conditions. The aim of the present study was to investigate the influence of long-lasting diabetes mellitus on the process of muscle regeneration in the skeletal muscle. Wistar rats were made diabetic by a single intraperitoneal injection of streptozotocin (STZ). The regeneration process in the s...

Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniqu...