Relaxation Rate of Constituent Muscle-Fibre Types in Human Quadriceps

1979 ◽  
Vol 56 (1) ◽  
pp. 47-52 ◽  
Author(s):  
C. M. Wiles ◽  
A. Young ◽  
D. A. Jones ◽  
R. H. T. Edwards
Keyword(s):  
Relaxation Rate ◽  
Muscle Fibre ◽  
Human Subjects ◽  
Muscle Fibre Types ◽  
Muscle Fibres ◽  
Isometric Contractions ◽  
Type I ◽  
Type Ii ◽  
Fibre Type Composition

1. Muscle fibres may be subdivided into type I (with slow-twitch contractile properties) and type II (fast-twitch) depending on their myosin adenosine triphosphatase activity. In voluntary isometric contractions type I fibres are utilized at low forces (<20% of maximum) whereas type II fibres are recruited in addition at high forces. This physiological recruitment order has enabled us to measure the relaxation rate of type I and II fibres in vivo in normal human subjects. 2. Relaxation rate was measured in 16 subjects from low (10% of maximum) and maximum isometric quadriceps contractions and the muscle-fibre type composition determined from needle-biopsy specimens in 10 subjects. The relaxation rate of type II fibres was calculated to be twice as fast as that of type I. 3. It was not possible to estimate, from studies in 33 quadriceps muscles (25 normal subjects), the contribution of type II fibres to overall fibre area from the relaxation rate as determined from electrically stimulated isometric contractions.

scholarly journals Composition and cross-sectional area of muscle fibre types in relation to daily gain and lean and fat content of carcass in Landrace and Yorkshire pigs

1996 ◽  
Vol 5 (6) ◽  
pp. 593-600 ◽  
Author(s):  
Marita Ruusunen ◽  
Marja-Liisa Sevon-Aimonen ◽  
Eero Puolanne
Keyword(s):  
Muscle Fibre ◽  
Live Weight ◽  
Carcass Composition ◽  
Cross Sectional Area ◽  
Muscle Fibre Types ◽  
Muscle Fibres ◽  
Type I ◽  
Sectional Area ◽  
Cross Sectional ◽  
Yorkshire Pigs

The muscle fibre-type properties of longissimus were compared between Landrace and Yorkshire breeds and between the sexes in an attempt to shed light on the relationship of these histochemical parameters to animal growth and carcass composition. Muscle fibres were classified into three groups, type I, type lIA and type 11B, using the myosin ATPase method. At a given live weight, the cross-sectional area of type I fibres (CSA1) was smaller (p

scholarly journals PL-016 Endurance training, muscle fibre type composition and the maximal capacity for fat oxidation

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Chris Shaw ◽  
Courtney Swinton ◽  
Maria Gabriela Morales Scholz ◽  
Tasman Erftemeyer ◽  
Andrew Aldous ◽  
...  
Keyword(s):  
Muscle Fibre ◽  
Fibre Type ◽  
Fat Oxidation ◽  
Muscle Fibre Type ◽  
Muscle Fibres ◽  
Type I ◽  
Maximal Rate ◽  
Fibre Type Composition ◽  
Type Composition ◽  
Whole Muscle

Objective A greater capacity for fat oxidation in endurance trained athletes is linked to greater utilisation of intramuscular lipid (IMCL). IMCL breakdown occurs only in type I muscle fibres yet little is known about the fibre type specific abundance of lipid regulatory proteins. We explored the impact of endurance training on the maximal rate fat oxidation, muscle fibre type and muscle fibre type specific abundance of proteins regulating IMCL metabolism. Methods Endurance trained (n=7, 28 ± 3 years, VO2max62.6 ± 1.6 ml·min-1·kg-1) and untrained (n=8, 25 ± 1 years, VO2max44.9 ± 1.9 ml·min-1·kg-1) males performed an incremental exercise test to determine maximal fat oxidation rate. Muscle fibre type composition and fibre type-specific IMCL content was assessed with immunofluorescence microscopy and protein abundance was analysed with immunoblotting on pooled single muscle fibres and whole muscle. Results Endurance trained individuals displayed a higher peak fat oxidation rate (0.49 ± 0.05 vs. 0.20 ± 0.03 g·min-1, P<0.05), which correlated with type I fibre percentage (R = 0.83, P < 0.01) and VO2max (R = 0.78, P < 0.01). Type I muscle fibres from endurance trained individuals had a greater abundance of ATGL. In whole muscle, the endurance trained group had greater abundance of PLIN2, PLIN5 and ATGL compared to the untrained group (P < 0.05). Furthermore, autophagy flux measured as LC3-II/I ratio was higher in type I muscle fibres and LC3-II/I, lysosomal markers (LAMP2) and chaperone-mediated autophagy markers (LAMP2A) were all higher in whole muscle of endurance trained individuals (P < 0.05). Conclusions These results demonstrate that the maximal rate of fat oxidation is related to the proportion of type I muscle fibres. Furthermore, IMCL storage and the abundance of key proteins regulating lipid metabolism is fibre type specific and greater in endurance trained individuals. Muscle fibre type composition should be considered when investigating the regulation of IMCL utilisation and markers of autophagy.

Effect of aerobic exercise on muscle structure and expression of proteins promoting hypertrophy and metabolism in aged rats

2020 ◽  
Vol 16 (5) ◽  
pp. 377-385
Author(s):  
W. Isobe ◽  
S. Murakami ◽  
T. Saito ◽  
S. Kumagai ◽  
M. Sakita
Keyword(s):  
Aerobic Exercise ◽  
Muscle Fibre ◽  
Cross Sectional Area ◽  
Muscle Fibre Types ◽  
Type I ◽  
Aged Rats ◽  
Sectional Area ◽  
Cross Sectional ◽  
Fibre Type Composition ◽  
Muscle Structure

Aging and physical inactivity lead to histochemical changes in muscles. The expression of many muscle proteins, including brain-derived neurotrophic factor (BDNF), silent information regulator of transcription 1 (SIRT1), and peroxisome proliferator-activated receptor γγ coactivator-1α (PGC-1a), declines with age. However, the effect of aerobic exercise on muscle structure and the expression profile of these proteins in elderly rats is unknown. Here, we investigated whether short-term aerobic exercise improves muscle structure and increases BDNF, SIRT1, and PGC-1a levels in aged rats. Ten male Wistar rats (95-week-old) were assigned to sedentary (SED) or exercise (Ex) groups. The Ex group performed running on a treadmill for 1 h, 6 times per week, for 2 weeks. The extensor digitorum longus muscles were removed to examine the muscle fibre type composition, cross-sectional area, and capillary-to-fibre (C/F) ratio. BDNF, SIRT1, and PGC-1a levels were evaluated by western blotting. Relative to the SED group, the Ex group showed increased proportion of Type I fibres (P<0.05), cross-sectional area of all muscle fibre types (P<0.05), succinate dehydrogenase activity (P<0.001), C/F ratio (P<0.05), and expression of BDNF, SIRT1, and PGC-1a (P<0.05).Thus, 2 weeks of aerobic exercise is sufficient to improve muscle histology and hypertrophic marker protein expression, indicating that it could prevent skeletal muscle atrophy in elderly rats.

scholarly journals Muscle Fibre Types and Their Relation to Meat Quality Traits in Pigs

2019 ◽  
Vol 50 (3) ◽  
pp. 164-170
Author(s):  
N. Lebedová ◽  
R. Stupka ◽  
J. Čítek ◽  
K. Zadinová ◽  
E. Kudrnáčová ◽  
...  
Keyword(s):  
Muscle Fibre ◽  
Meat Quality ◽  
Current Knowledge ◽  
Quality Parameters ◽  
Fibre Types ◽  
Muscle Fibre Types ◽  
Muscle Fibres ◽  
Fibre Type Composition ◽  
Intrinsic Factors ◽  
New Findings

Abstract The authors have been studying various characteristics of muscle fibres and their relationship to the meat quality parameters for many years. However, the conclusions drawn by researchers often differ. A higher proportion of glycolytic IIB fibres in pig muscles is usually related to paler meat with lower water holding capacity. On the other hand the relationship between muscle fibres and meat texture parameters is not clear. Studies using immunohistochemistry methods that allow a more detailed classification of individual muscle fibre types could bring new findings in this area. It would thus be possible to influence muscle fibre type composition in the muscle to achieve the desired meat quality using various extrinsic and intrinsic factors. The main aim of this review is to summarise current knowledge on the description of muscle fibres typology and the effect of their morphological traits on pork meat quality.

scholarly journals Histological characteristics of the musculus longissimus lumborum et thoracis muscle fibres in pigs in relation to selected RYR1, MYOG, MYOD1 and MYF6 genotypes

2014 ◽  
Vol 83 (3) ◽  
pp. 233-237
Author(s):  
Roman Stupka ◽  
Jaroslav Čítek ◽  
Michal Šprysl ◽  
Monika Okrouhlá ◽  
Luboš Brzobohatý ◽  
...  
Keyword(s):  
Gene Polymorphism ◽  
Muscle Fibre ◽  
Fibre Types ◽  
Muscle Fibre Types ◽  
Muscle Fibres ◽  
Type I ◽  
Pcr Rflp ◽  
Longissimus Lumborum ◽  
Histological Characteristics

Histochemical and biochemical muscle fibre properties are the factors that influence the quantitative and qualitative characteristics of pork meat. The aim of the study was to assess the influence of genetic effects of selected genetic markers MyoD genes and RYR1 on the achieved indicators of muscle fibres in the musculus longissimus lumborum et thoracis (MLLT). The study included a total number of 216 hybrid pigs with the mean slaughter weight of 123 kg. Gene polymorphism was determined by the PCR-RFLP method. The gene polymorphism was determined in the RYR1, MYOD1, MYOG, and MYF6 genes. Muscle fibre types from MLLT were identified. Concerning the RYR1 gene, the study found that homozygous-dominant animals reached a lower number of type I (8.35 vs. 10.52; P < 0.05) and a higher number of IIA (3.66 vs. 2.10; P < 0.05) and a higher number of IIB (76.61 vs. 67.91; P < 0.05). The maximum number in all types of muscle fibres reached BB genotype of the MYOG gene (type I: 14.02; IIA: 18.47; IIB: 83.08; P < 0.05). The AA genotype of the MYOD1 gene showed the lowest (P < 0.05) number of muscle in all fibre types (type I: 9.20; IIA: 0.85; IIB: 69.23). The influence of individual genotypes of selected genes on the selected muscle fibre characteristics was proven. The obtained results confirm the possibility of affecting the quality of pork with genomic selection of MyoD genes family.

A delayed rectifier conductance in type I hair cells of the mouse utricle

1996 ◽  
Vol 76 (2) ◽  
pp. 995-1004 ◽  
Author(s):  
A. Rusch ◽  
R. A. Eatock
Keyword(s):  
Hair Cells ◽  
Time Course ◽  
Dissociation Constants ◽  
Resting Potential ◽  
Delayed Rectifier ◽  
Type I ◽  
Type Ii ◽  
Voltage Range ◽  
Average Maximum

1. Membrane currents of hair cells in acutely excised or cultured mouse utricles were recorded with the whole cell voltage-clamp method at temperatures between 23 and 36 degrees C. 2. Type I and II hair cells both had delayed rectifier conductances that activated positive to -55 mV. 3. Type I, but not type II, hair cells had an additional delayed rectifier conductance (gK,L) with an activation range that was unusually negative and variable. At 23-25 degrees C, V(1/2) values ranged from -88 to -62 mV in 57 cells. 4. gK,L was very large. At 23-25 degrees C, the average maximum chord conductance was 75 +/- 65 nS (mean +/- SD, n = 57; measured at -54 mV), or approximately 21 nS/pF of cell capacitance. 5. gK,L was highly selective for K+ over Na+ (permeability ratio PNa+/PK+:0.006), but unlike other delayed rectifiers, gK,L was significantly permeable to Cs+ (PCs+/PK+:0.31). gK,L was independent of extracellular Ca2+. 6. At -64 mV, Ba2+ and 4-aminopyridine blocked gK,L with apparent dissociation constants of 2.0 mM and 43 microM, respectively. Extracellular Cs+ (5 mM) blocked gK,L by 50% at -124 mV. Apamin (100 nM) and dendrotoxin (10 nM) has no effect. 7. The kinetic data of gK,L are consistent with a sequential gating model with at least two closed states and one open state. The slow activation kinetics (principal time constants at 23-25 degrees C:600-200 ms) had a thermal Q10 of 2.1. Inactivation (Q10:2.7) was partial at all temperatures. Deactivation followed a double-exponential time course and had a Q10 of 2.0. 8. At 23-25 degrees C, gK,L was appreciably activated at the mean resting potential of type I hair cells (-77 +/- 3.1 mV, n = 62), so that input conductances were often more than an order of magnitude larger than those of type II cells. If these conditions hold in vivo, type I cells would produce unusually small receptor potentials. Warming the cells to 36 degrees C produced parallel shifts in gK,L's activation range (0.8 +/- 0.3 mV/degrees C, n = 8), and in the resting potential (0.6 +/- 0.3 mV/degrees C, n = 4). Thus the high input conductances were not an artifact of unphysiological temperatures but remained high near body temperature. It remains possible that in vivo gK,L's activation range is less negative and input conductances are lower; the large variance in the voltage range of activation suggests that it may be subject to modulation.

scholarly journals Biological Relevance of Colony Morphology and Phenotypic Switching by Burkholderia pseudomallei

2006 ◽  
Vol 189 (3) ◽  
pp. 807-817 ◽  
Author(s):  
Narisara Chantratita ◽  
Vanaporn Wuthiekanun ◽  
Khaemaporn Boonbumrung ◽  
Rachaneeporn Tiyawisutsri ◽  
Mongkol Vesaratchavest ◽  
...  
Keyword(s):  
Burkholderia Pseudomallei ◽  
Vaccine Development ◽  
Colony Morphology ◽  
Phenotypic Switching ◽  
Type I ◽  
Type Ii ◽  
Altered Expression ◽  
Replication Fitness

ABSTRACT Melioidosis is a notoriously protracted illness and is difficult to cure. We hypothesize that the causative organism, Burkholderia pseudomallei, undergoes a process of adaptation involving altered expression of surface determinants which facilitates persistence in vivo and that this is reflected by changes in colony morphology. A colony morphotyping scheme and typing algorithm were developed using clinical B. pseudomallei isolates. Morphotypes were divided into seven types (denoted I to VII). Type I gave rise to other morphotypes (most commonly type II or III) by a process of switching in response to environmental stress, including starvation, iron limitation, and growth at 42°C. Switching was associated with complex shifts in phenotype, one of which (type I to type II) was associated with a marked increase in production of factors putatively associated with in vivo concealment. Isogenic types II and III, derived from type I, were examined using several experimental models. Switching between isogenic morphotypes occurred in a mouse model, where type II appeared to become adapted for persistence in a low-virulence state. Isogenic type II demonstrated a significant increase in intracellular replication fitness compared with parental type I after uptake by epithelial cells in vitro. Isogenic type III demonstrated a higher replication fitness following uptake by macrophages in vitro, which was associated with a switch to type II. Mixed B. pseudomallei morphologies were common in individual clinical specimens and were significantly more frequent in samples of blood, pus, and respiratory secretions than in urine and surface swabs. These findings have major implications for therapeutics and vaccine development.

Dye coupling between rat striatal neurons recorded in vivo: compartmental organization and modulation by dopamine

1994 ◽  
Vol 71 (5) ◽  
pp. 1917-1934 ◽  
Author(s):  
S. P. Onn ◽  
A. A. Grace
Keyword(s):  
Intravenous Administration ◽  
D2 Receptor ◽  
Type I ◽  
Type Ii ◽  
Dye Coupling ◽  
Striatal Neurons ◽  
Receptor Stimulation ◽  
D2 Agonist ◽  
Response Profile

1. The presence of dye coupling between striatal neurons was investigated using in vivo intracellular recording and dye injection in adult rats. In 17% of the cases in which a single striatal neuron was injected with Lucifer yellow, more than one labeled neuron was recovered. In control rats, this dye coupling was observed only between single pairs of medium spiny neurons and only when the neuron injected exhibited the Type II response profile as defined by paired-pulse stimulation of corticostriatal afferents. 2. After intravenous administration of the D1/D2 agonist apomorphine at a behaviorally effective dose (i.e., 0.1–0.3 mg/kg), an increase in the incidence (from 17% to 82% of injected cells) and extent (from 2 cells to 3–7 cells labeled per injection) of dye coupling was observed. This effect was mediated by D2 receptor stimulation because administration of the D2 agonist quinpirole caused similar alterations in the incidence and extent of dye coupling (66% coupled). In contrast, administration of the D1 agonist SKF 38393 or the D1 antagonist SCH 23390 did not result in any significant alteration in dye coupling. 3. In control rats, the entire somatodendritic regions of dye-coupled neurons were found to be localized within single matrix compartments of the striatum. However, after intravenous administration of apomorphine or quinpirole, clusters of dye-coupled neurons were found to extend across the patch/matrix boundary. Moreover, dye coupling was observed after injecting cells exhibiting either the Type I or the Type II response profile. 4. In response to D2 receptor stimulation, both the extent and the pattern of coupling between striatal neurons is altered, resulting in direct coupling between neurons that are otherwise functionally and anatomically segregated in the control animal.

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