Muscle development or myogenesis is a complex and regulated process, the end result of which is the formation of a multinucleated myofiber. Significant control of skeletal muscle development depends upon the muscle basic helix-loop-helix (bHLH) gene family known as myogenic regulatory factor (MRF), which includes MyoD, Myf-5, myogenin, and MRF4 (Parker M.H. et al., 2003) (Fig. 1), and the negative helix-loop-helix (HLH) regulators, Inhibitor of differentiation proteins (Ids) (Hasskarl J. and Munger K. 2002). MyoD and Myf5 serve as early myogenic regulatory factors and they mark the myoblast commitment to differentiation. It has been shown that expression of MyoD in non-muscle fibroblast cells can convert them to myogenic cells by activating
other downstream MRFs, like MRF4 and myogenin (Tapscott S.J. et al., 1988). Myogenin acts later in development and plays an essential role in the terminal differentiation of myotubes in vivo (Rudnicki M.A. and Jaenisch R. 1995). While expression of MyoD or Myf5 commits a cell to the myogenic lineage, expression of MyoD is more effective at initiating differentiation. MRF4 appears to have a role as a determination factor in a subset of myocytes in the early somite and as a differentiation factor in later muscle fibers (Parker M.H. et al., 2006). Once the MRFs are activated, these bHLH transcription factors function as heterodimers with the ubiquitously expressed bHLH E proteins to activate the terminal differentiation program by regulating the transcription of many genes, including those encoding the contractile proteins and muscle-specific enzymes, as well as a number of miRNAs (Buckingham M. and Rigby W.J. 2014). MRF and E protein dimerization is dependent upon the relative abundance of each transcription factor
The skeletal and ultimate cardiac muscle fibers are affected by DMD. The disease starts by affecting the lower port...
16. Describe two evolutionary consequences if the process of crossing over in meiosis ceased to occur. If crossing over in meiosis ceased to occur there would be less genetic variations and no diversity among a species. This would essentially mean that a species would not be able to adapt to an issue that could arise in the future, meaning that its species could potentially become extinct due to climate change or other arising events.
Every day we use our skeletal muscle to do simple task and without skeletal muscles, we will not be able to do anything. Szent-Gyorgyi (2011) muscle tissue contraction in rabbit’s muscles and discovered that ATP is a source for muscle contraction and not ADP. He proposed a mechanism to cellular respiration and was later used by Sir Hans Krebs to investigate the steps to glucose catabolism to make ATP. In this paper, I will be discussing the structure of muscle fibers and skeletal muscles, muscle contraction, biomechanics, and how glucose and fat are metabolized in the skeletal muscles.
Within skeletal muscle there are extremely small structures that form the muscle and allow contractions and movement to occur (epimysium, perimysium, endomysium, fascicles, fiber, sarcomere, sarcoplasmic reticulum and t tubules). These structures all play a role in protecting, connecting and transporting substances throughout the muscle fibers. They are also the main contributors to movement.
Dystrophin is part of a complex structure involving several other protein components. The "dystrophin-glycoprotein complex" helps to anchor the structural skeleton (cytoskeleton) within the muscle cells, through the outer membrane (sarcolemma) of each cell, to the tissue framework (extracellular matrix) that surrounds each cell (Straube and Campbell, 1997). Due to defects in this assembly, contraction of the muscle leads to disruption of the outer membrane of the muscle cells and eventual weakening and wasting of the muscle
This condition is said to start within the sacromeric proteins, as past studies has called this disorder ‘the disease of the sacromere’ 6. The muscle around the left ventricle is so strong that is does not relax enough after contraction to regenerate blood back into the heart 5. Hypertrophic cardiomyopathy was discovered in approximately 50% of young individuals who died suddenly 5. A recent study observed the genes associated with hypertrophic cardiomyopathy. Within 20 sacromere and myofilament related genes, there were 1400 mutations noted in HCM 6. The mutations within the sacromere prevent normal shortening that causes the muscle to contract stronger, reducing relaxation. However, all the mutated genes are not proven to cause hypertrophy. The MYH7 gene seems to be the most frequent as 25-35% of patients with mild or severe HCM had this gene present 6. Despit...
Repair after a muscle is damaged happens through the division of certain cells who then fuse to existing, undamaged muscle fibers to correct the damage. Different muscle types take different amounts of time to heal and regenerate after it has been damaged. Smooth muscle cells can regenerate with the greatest capacity due to their ability to divide and create many more cells to help out. While cardiac muscle cells hardly regenerate at all due to the lack of specialized cells that aid in repair and regeneration. In skeletal muscle, satellite cells aid in helping restoration after injury. Along with muscles, tendons are very important structures within the human body, and they to can be damaged. However, tendon repair involves fibroblast cells cross-linking collagen fibers that aid in not only reinforcing structural support, but also mechanical support as well (“Understanding Tendon Injury,” 2005). While quite different from muscle repair, tendon repair involves the similarity of reestablishing d...
...re out how get only one gene in the right cell, how to keep the gene from impairing any other functions and how to get the gene to produce the right amount of protein. Some researchers are trying a different approach; that of myoblast transfer therapy. This school of thought attempts to fuse healthy, immature muscle cells with dystrophic cells to make hybrid muscles that function normally. Unfortunately, initial tests have not fared very well because the injected myoblasts do not seem to travel very far from the injection site. The last type of research deals with a protein called utrophin. It is hoped that this protein could functionally take over for dystrophin. Scientists are trying to discover a chemical that will upregulate utrophin production without disrupting anything else in the body.
Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere. The best proposed model for understanding contraction is the sliding filament model of muscle contraction. Actin and myosin fibers overlap in a contractile motion towards each other. Myosin filaments have club-shaped heads that project toward the actin filaments.
New cells are often produced in the body during growth and development. In addition, new cells also develop as the body repairs and remodels its tissues after an injury. These new cells come from mesenchymal stem cells (MSCs), which are considered as multipotent cells. MSCs are found in various parts of the body during growth and development, but in adults, they are present in the bone marrow, where they later differentiate, mature and migrate to become more specialized cells with unique functions. These cells' potential to develop into bone cells, cartilage cells, muscle cells and fat cells makes their role in regeneration, repair and remodelling important, especially when the body undergoes the normal process of aging or recovers from disease or injury.
Cardiac muscle is a type of involuntary muscle found only in the walls of the heart, specifically the myocardium. Cardiac muscles contract automatically to tighten the walls of the heart in a rhythmic fashion. The heart beats nonstop about 100,000 times each day. Smooth muscle is a type of involuntary muscle found within the walls of blood vessels such as in small arteries and veins. Smooth muscle is also found in the urinary bladder, uterus, male and female reproductive tracts, gastrointestinal tract, and the respiratory tract. Skeletal muscles are voluntarily controlled and are attached to bones by tendons. Skeletal muscles also vary considerably in size and shape. They range from extremely tiny strands such as in the muscle of the middle ear as large like in the muscles of the thigh. The three individual muscle types also serve five main functions. The five basic functions are movement, organ protection, pumping blood, aiding digestion, and ensuring blood flow.
Sarcopenia is considered to be the degenerative loss of skeletal muscle mass and it’s functioning due to aging (Waters, Baumgartner & Garry 2000). It is linked to muscle atrophy which is shortening of the muscle. It can be mostly noticed in fast twitch fibres which usually fatigue easily and provide a larger amount of force in comparison to slow twitch fibres. Sarcopenia is usually ...
It is estimated that 1 out of every 5,600-7,700 boys ages 5-24 have Duchene or Becker muscular dystrophy. (“Data & Statistics,” 2012 April 6) Muscular dystrophy is a group of genetic diseases defined by muscle fibers that are unusually susceptible to damage. There are several different types of muscular dystrophy some of which shorten the affected person’s lifespan. (“Muscular dystrophy: Types and Causes of each form,” n.d.) There is a long history of the disorder but until recently there wasn’t much knowledge of the cause. (“Muscular Dystrophy: Hope through Research,” 16 April 2014) Symptoms are obvious and can be seen as soon as a child starts walking. (“Muscular Dystrophy,” 2012 January 19) Although muscular dystrophy mostly affects boys, girls can get it too. (“Muscular Dystrophy,” 2012 January 19) There is no cure for muscular dystrophy but there are several types of therapy and most types of muscular dystrophy are still fatal. (“Muscular Dystrophy: Hope through Research,” 16 April 2014)
Meiosis is a specialized form of nuclear division in which there two successive nuclear divisions (meiosis I and II) without any chromosome replication between them. Each division can be divided into 4 phases similar to those of mitosis (pro-, meta-, ana- and telophase). Meiosis occurs during the formation of gametes in animals.
Muscle tissues grow by means of physical activity in the same way they are able to become more well-defined (with regards to physical