Revised Date: 07/ Accessibility Information and Tips Title: Tetanic Ca transient differences between slow- and fast-twitch mouse skeletal muscle fibres: a Authors: Calderón, [email protected] Tetanic Ca transients were classified as morphology type I (MT-I) or type II (MT-II) according to their shape. Under normal circumstances our fast-twitch muscle fibers become smaller We warm-up for about five minutes at a slow pace (running) or with. Looking to build endurance? What about power? Do dreams of being an all-star hitter or marathon runner need to be dashed if twitch ratios.
Fast Twitch vs. Slow Twitch Muscle Fibers | Jeff Galloway
Myoglobin release from the damaged muscle can lead to acute renal failure. All statins have been associated with adverse muscle events [ 5 ].
Statins lower the concentration of low-density lipoprotein cholesterol and very-low-density lipoprotein cholesterol in people with elevated triglycerides. Many patients cannot reach this at low doses, so they tend to use high doses of statin.
The risk of myopathy is increased with high doses [ 3 ]. The mechanism determining muscle damage is not clear [ 6 ]. There are several possible mechanisms such as depletion of secondary metabolic intermediates and induction of apoptosis, have been proposed for statin-induced myopathy [ 7 ]. In the markets atorvastatin is available in 10, 20, 40, and 80 mg tablets.
The aim of the present study was to test the effect of different doses of atorvastatin on the skeletal muscles of male albino rat and the possible mechanisms involved in this effect by using histological, histochemical and immunohistochemical methods.
The study was dealing with the skeletal muscle tissues of adult male albino rats. Twenty four male albino rats at the age weeks, weighting grams, specific pathogens free were used. Animals were housed in a clean plastic cage in an air conditioned room under a 12 h light dark cycle. All animals became acclimatized for at least 7 days before the outset of the study and were given food and water ad-libitum and were kept at constant humidity and temperature.
The experiment was approved by the ethical committee for animal handling for research work in Minia University. Each dose was freshly dissolved in distilled water before the oral intake. Experimental design Animals were randomly divided into four groups six rats eachthe control group author included 6 rats were received distilled water and the treated groups received atorvastatin dissolved in distilled water by a gastric tube at different doses for 8 weeks.
Rats from all groups were sacrificed after 8 weeks by decapitation under light halothane anesthesia. Skeletal muscle tissue samples were obtained for tissue preparation. The vastus medialis muscle of the right limb was obtained and divided into two parts.
The other part was rapidly put in the cryostat for Succinic dehydrogenase and Acetyl choline esterase histochemical study. All the histological and the histochemical Bancroft and Garblo [ 9 ].
Immunohistochemical staining was performed using polyclonal rabbit antibodies anti-cleaved caspase 3 which was obtained from sigma aldrich and monoclonal mouse antibodies anti-myosin fast twitch type II heavy-chain myosin which was obtained from thermo scientific. Immunohistochemistry for both was performed on paraffin sections [ 10 ]. Sections were deparaffinized, hydrated then washed in 0. Endogenous peroxidases were blocked by treatment with H2O2 in methanol.
The sections were incubated with the diluted primary antibodies for cleaved caspase 3 1: Sections then were washed 3 times each for 5 minutes in buffer and incubated for further 30 minutes with biotinylated secondary antibodies diluted 1: Following further 30 minutes incubation with Vectastain ABC kits Avidin, Biotinylated horse radish peroxidase Complex and washing for 10 minutes, the substrate, diaminobenzidine tetra hydrochloride DAB in distilled water was added for min.
The slides were lightly counterstained by hematoxylin. For anti-cleaved caspase 3 positive control human tonsil slides were stained. The positive immunoreactivity for anti-myosin fast twitch type II heavy-chain myosin appeared as brown stained cytoplasm of the immunoreactive cells.
The positive immunoreactivity for anti-cleaved caspase 3 appeared as brown cytoplasmic or nuclear staining.
Fast Twitch vs. Slow Twitch Muscle Fibers
Negative control slides were prepared by the same steps except they were incubated with the antibody diluent instead of primary antibody.
Photography Slides were photographed using Olympus digital camera. Images were saved as jpg and processed using Adobe Photoshop 7 to standardize brightness, contrast and background color. Morphometric analysis The procedures utilized a hardware consisting of a high-resolution color digital camera mounted on an Olympus BX51 microscope and connected to a computer.
Quantitative data were collected for 2 parameters: Three different sections of the same animal were used. They were counted in the 40 high power fields. The percentage of caspase-3 positive fiberscontrol tonsil slides were stained was determined in 10 different adjacent non overlapped fields the number of caspase-3 positive was divided by the total number of fibers at the same fields.
Results Morphological study Examination of H and E stained longitudinal sections LS of the muscle tissue of the control group revealed that the muscle fibers were long, non-branching, striated and cylinder with acidophilic sarcoplasm. Their nuclei were multiple, elongated, vesicular and peripherally located just beneath the sarcolemma Some satellite cells were noticed on the surface of the myofibers and fibroblast like cells appeared within the endomysium Figure 1A.
In transverse section TSthe skeletal muscle fibers appeared polygonal with acidophilic sarcoplasm and peripherally located nuclei. The muscle fibers are grouped into bundles. Each bundle is surrounded by a connective tissue sheath perimysium. Each muscle fiber is surrounded by endomysium Figure 1B.Muscle Fibers: Changing Your Muscle Type- Thomas DeLauer
Inflammatory cellular infiltration started through the endomysium Figure 2A. Some muscle fibers became rounded with loss of the polygonal appearance. Their nuclei appeared rounded central instead of their peripheral position.
A Photomicrograph of rat skeletal muscle tissue of the control group showing A. Bundles of non branching cylindrical shaped muscle fibers with acidophilic sarcoplasm thin arrowsand multiple elongated vesicular nuclei peripherally located beneath the sarcolemma thick arrows.
Notice the smaller nuclei of satellite cells curved arrows and the flat nuclei of fibroblasts in the endomysium arrow heads. Inset showing cross striations. TS of rat skeletal muscle tissue of the control group showing polygonal shaped skeletal muscle fibers with acidophilic cytoplasm arrow and peripherally located nuclei arrow head.
The muscle fibers are separated by endomysium curved arrow. Notice the perimysium is seen between muscle bundles thick arrow.
A photomicrograph of rat skeletal muscle tissue of treated group II showing A. LS of muscle fibers with inflammatory cellular infiltration thick arrows and splitting of muscle fibers arrow heads.
Notice the central nuclei arrow. TS of the muscle fibers showing rounding of some fibers thick arrows and rounded internal nuclei arrows.
Notice muscle fiber splitting arrow heads and fragmentation of the sarcoplasm of some muscle fibers curved arrow.
KEEPING FIT: To avoid fast-twitch muscle loss, add interval training to your regimen
Some myofibers had prominent euchromatic nuclei that were linearly arranged and often surrounded by more satellite cells. Myonuclear changes were also observed in many fibers. These changes were in the form of nuclear enlargement, irregular shapes and clumping.
Internal nuclei were also common Figures 3A and 3B. Inflammatory cellular infiltration was also noticed Figure 3A There was variation in the fiber size. Few muscle fibers appeared hypertrophied with ill defined outlines but most of the fibers still keep their normal appearance. Some of the enlarged fibers appeared splitted and others showed fragmentation of their cytoplasm Figure 3C.
A photomicrograph of rat skeletal muscle tissue of treated group III showing A. LS of muscle fibers with inflammatory cellular infiltration thick arrowssplitting of muscle fibers arrow heads and mild wavy appearance of myofibrils curved arrow.
Notice the central nuclei arrows. Myofibers with linearly arranged euchromatic nuclei black arrowMany satellite cells blue arrows. Notice myonuclear changes in the form of nuclear enlargement red arrow and irregular shapes white arrow. TS of muscle fibers showing rounded internal nuclei arrowssplitted muscle fiber thick arrows and fragmentation of sarcoplasm of some muscle fibers stars. Their myofibrils became extensively wavy Figure 4A Inflammatory cellular infiltration was also noticed in-between the myofibers Figures 4B and 4C.
There was marked variation in the fiber size and most of the myofibers lost their polygonal appearance and appeared swollen. This obscured the endomysium between the deformed myofibers Figures 4B and 4C. The degenerated muscle fibers appear swollen with pale stained sarcoplasm that was extensively fragmented Figures 4A and 4C. Some myofibers had prominent euchromatic nuclei that were linearly arranged and often surrounded by more satellite cells Figure 4D.
In the Glees stained sections of the control group, the nerve fibers showed a continuous uniform impregnation of the silver stain while the myoneural junctions appeared as a hen leg appearance Figure 5A. In Group II, There was considerable damage of the nerve fibers. This appeared in the form of the breakup of the silver impregnation in comparison with the uniform staining of the control group.
Thinning of the nerve fibers was noticed in some areas along their length Figure 5B. The degenerated nerve fibers became markedly thin and appeared as ghosts.
Silver droplets appeared around the degenerated nerve fiber. Many nerve fibers showed disorganized neurofibrils with breakup of the silver impregnation of this degenerated nerve. Histochemical studies for detection of succinic dehydrogenase enzyme SDH activity showed that the transverse section TS of the muscular tissue of the control group was consisting mostly of lightly stained type II with few deeply stained type Ithe type II fibers are large while type I fibers are small.
The staining is granular throughout the fibers Figure 6A. In group II, some of the low oxidative fast twitch fibers type II had central and eccentric loss of staining, while the high oxidative slow twitch fibers type I were not affected Figure 6B.
In group III, both two types of the muscle fibers were affected. Many low oxidative fast twitch fibers type II showed central and eccentric loss of staining. The high oxidative slow twitch fibers type I showed decrease in the intensity of staining in the center Figure 6C. In group IV the low oxidative fast twitch fibers type II had large areas of complete loss of staining, while the highly oxidative slow twitch fibers type I showed eccentric loss of staining Figure 6D.
AChE was detected at the motor end plate regions in the different groups. They were distributed along the border of the muscle fibers. NMJ appeared smaller in size, less compacted and lighter in staining in group IV when compared with the previous groups Figure 7D. Immunohistochemical study of muscle tissues using myosin fast twitch type II heavy chain antibody showed that skeletal muscle tissue from the control group had a positive reaction in the form of fine brown granules, the two types of muscle fibers could be demonstrated the more numerous immunopositive type II fast twitch fibers and the less numerous slow twitch muscle fibers type I that remained unstained Figure 8A.
For the negative control, slides were prepared from skeletal muscle tissue Figure 8B. In group II, splitting of some of the immunopositive type II fibers with sparing of the negative immunoreactive type I fibers was noticed Figure 8C. In group III many type II fibers appeared degenerated with fragmented cytoplasm while the type I fibers retained their normal histological appearance Figure 8D.
Both immunopositive and immunonegative fibers were affected in group IV. Extensive fragmentation of the sarcoplasm appeared in the immunopositive type II fibers while some immunonegative type I fibers showed splittting Figure 8E. Positive control slides prepared from human tonsil demonstrated the positive reaction of caspase 3 in the form of fine brown granules Figure 9A. For the negative control, slides were prepared from skeletal muscle tissue Figure 9B.
Sections of the control group I showed no detectable immunolabeling for activated caspase 3 in the skeletal muscle sections Figure 10A. In group II, there was obvious high immunoreactivity for activated caspase 3 in the cytoplasm of the rounded muscle fibers. Some immunopositive muscle fibers showed splitting and some nuclei were positively stained Figure 10B. Few muscle fibers showed negative immunoreactivity. A photomicrograph of rat skeletal muscle tissue of treated group IV showing A.
Wavy myofibrils curved arrows with areas of fragmented sarcoplasm stars. Notice pale acidophilic sarcoplasm of the degenerated fibers circles. Both techniques can be practiced in any aerobic activity, including running, cycling, stepping, rowing and elliptical machines.
I suggest starting with interval training, which can be individually progressed in a variety of protocols. Essentially, interval training segments your endurance exercise session into alternating periods of lower effort slower-paced and higher effort faster-paced performance. For example, instead of running on the treadmill at 6 miles per hour for 20 minutes, you could run at 7 miles per hour for 4 minutes, then run at 5 miles per hour for 4 minutes, alternating faster and slower segment throughout your minute training session.
As you become more fit you could progress to even faster intervals, such as 2 minutes at 8 miles per hour, followed by 2 minutes at 4 miles per hour, again alternating higher-effort and lower-effort segments throughout a minute workout.
Of course, the faster the running speed the more involvement of fast-twitch muscle fibers. However, to maximize the impact on your fast-twitch muscle fibers you need to approach sprinting speed, which is not recommended for treadmill training. My preference is to perform two yard sprints or fast strides after I complete my outdoor runs.
This is an exhilarating way to finish my endurance exercise and it provides an excellent training stimulus for my fast-twitch muscle fibers. Of course, I cool-down gradually after the sprints.
You can apply the same interval training and sprinting principles to other aerobic activities such as stationary cycling. For example, instead of pedaling 70 RPMs at watts for 20 minutes, you could alternately pedal same cadence at watts for 3 minutes, then at 75 watts for 3 minutes throughout your cycling session. As for sprinting, you could finish your workout with a couple brief bouts 15 seconds of fast pedaling 90 RPMs at an even higher resistance watts.
It is not necessary to do interval training or sprinting every workout. In addition to stimulating your fast-twitch muscle fibers, interval training is more effective than steady-state exercise for enhancing cardiovascular endurance.
Although your short sprinting segments will not increase your aerobic capacity, they provide the best training stimulus to your fast-twitch muscle fibers for improved power performance.
It is more challenging physiologically and psychologically to do interval training and sprinting. However, the benefits in terms of physical fitness and activity performance are well worth the effort.