Mechanotransduction, which is the process by which cells converts mechanical stimuli to biochemical signaling cascades, is involved in the homeostasis of numerous tissues. The mechanotransduction of oscillatory shear stress by bone resident cells has gained special attention because of its role in regulating bone formation, remodeling and disease. Mechanical forces, especially, fluid shear stress has been observed to induce several cellular responses in osteoblastic cells, including intracellular calcium influx, stress fiber formation, ATP, nitric oxide and prostaglandin E2 release, MAPK activation and gene expression changes 1–5. In particular, there is intense interest in identifying the primary molecular mechanism of the osteoblast sensing and corresponding responding to the shear stress because its discovery may lead to clinical interventions in osteoporosis, osteoarthritis and other disease related to mechanobiology.
Mechanobiology is defined as the study of the entire process of sensation, transduction and attendant changes in cell phenotypes. Here we define “mechanosensor” as cellular structure that responds to mechanical stress and initiates mechanotransduction in response to shear stress without involving chemical second messengers. Because mechanical linkages from the cell surface to lateral, internal, and basal parts of the cell redistribute forces imposed on the cell surface, many structure could serve as mechanosensors. In order to understand the mechanism of the initiation of shear modulation of osteoblast function, there have been many studies searching for primary shear sensors. In this chapter, we address the hypothesis of considering the whole cell as a mechanosensor. Cell shape distortion or deformation by she...
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...ization of the cytoskeletal elements. Only intercompartmental directed movement of the raft domains forms lipid raft clusters, that act as a platform for the activation of several raft associated proteins 25. Physiologic oscillatory shear stress at 0.2-0.5 Hz induces directed movements of raft domains for the formation of raft cluster and thus supports our earlier finding on osteoblast activation at the same shear stress. Our observations in this present work imply that, lipid rafts dynamics spatially regulate the dynamics of actin cytoskeleton and corresponding cellular traction force. Collectively, our experiments showed the dynamic characteristics of lipid raft movements that regulate mechanotransduction in osteoblasts and indicated the importance of characterization of lipid raft dynamics to decipher other lipid raft associated cell membrane events more deeply.
The Stavelot Triptych is stunning in its complexity and artistry. It was created by unknown artists, around mid-12th century, possibly for Abbot Wibald, in modern-day Mosan, Belgium. This artwork is currently on display in the Jerusalem exhibit at the MET. The Stavelot Triptych not only tells the story of the True Cross, but it shows the division of the Roman Empire, division of Christianity and the artistic differences between the East and the West. This formal analysis will express how the structure/shape, color, line, composition and techniques/ textures contribute to the meaning of the triptych.
An osteoblast is a “baby” bone cell whose main job is to secrete osteoid which forms the hardened, or calcified, bone matrix. Osteocytes are formed from osteoblasts. Osteocytes are the mature bones cells that have been completely differentiated. They are found in the lacunae of hard bone and have a spider-like appearance due to their canaliculi. Osteoclasts are a different type of cell formed from the mesenchymal cells. These cells are not related to osteoblasts or osteocytes. Their job is to basically “eat” the bone to create cavities and other hallow spaces during bone remodeling. Finally, the cells form differentiate to form fibroblasts and fibrocytes. These fibroblasts and fibrocytes secrete and form the matrix for fibrous connective tissue which is an essential component of the
...st the sacrolemma will depolarized, thus activation potentials along the T-tubules. This signal will transmit from along the T-tubules to sarcroplasmic reticulum's terminal sacs. Next, sarcoplasmic reticulum will release the calcium into the sarcroplasm leading to the next second event called contraction. The released calcium ions will now bind to troponin. This will cause the inhibition of actin and mysoin interaction to be released. The crossbridge of myosin filaments that are attached to the actin filaments, thus causing tension to be exerted and the muscles will shorten by sliding filament mechanism. The last event is called Relaxation. After the sliding of the filament mechanism, the calcium will be slowly pumped back into the scaroplasmic reticulum. The crossbridges will detach from the filaments. The inhibition of the actin and myosin will go back to normal.
Bone contains an inorganic component composed of mineral salts, primarily calcium and potassium, and an organic component made of collagen, a complex protein that is found in various forms in bone and other connective tissues. According to Wolff’s Law, bone is capable of adjusting its strength in proportion to the amount of stress placed on it. When young, healthy people participate in exercise programs for extended periods of time, their bones can become more dense through increased deposition of mineral salts and the number of collagen fibers. On the other hand, if bones are not subjected to mechanical stresses, as in individuals with sedentary lifestyle or
Osteogenesis imperfecta, also known as “brittle bones disease,” is a rare genetic disorder that affects the body’s production of type I collagen, which is the major protein of the body’s connective tissue. Generally, people affected with OI either have too little of type I collagen, or the quality of it is poor. Collagen defects account for about 85%.1 However, proteins in the bones may be affected in some of the more uncommon forms of OI. Because of this defect, people with OI have fragile bones, which break easily without an apparent cause.
Osteoporosis is a serious disease that leads to a faster than normal loss of the bone density, which puts the bone at a higher risk for fractures. In order to understand the causes of Osteoporosis, it is important to understand how bones are formed. Bone is a living tissue that is made mainly of collagen, calcium phosphate, and calcium carbonate. The mixture of collagen and calcium gives the bone strength and flexibility. The body deposits new bones and removes old ones; moreover, there are two types of bone cells that control the reproduction of bones. Cells called osteoclasts breakdown bone tissues thus, damaging the bone. Once the damaged bone is removed, cells called osteoblasts, use minerals including calcium and phosphate from the blood stream to make new healthy bone tissues. In order for osteoblasts and osteoclasts to work properly, hormones such us thyroid, estrogen, testosterone, and growth hormones are
...act to vertical force production is not hindered. However this was not seen by Babbert et al. (1996), as movement disintegration was not present in the SJ and toe off location in CMJ and SJ remained the same.
Osteopetrosis is a rare, genetic disease that causes extremely dense and brittle bones. This is because individuals affected with osteopetrosis do not have normal osteoclasts, which bones need to work correctly. Healthy bones require properly functioning osteoblasts and osteoclasts. Osteoblasts are responsible for making new bones and osteoclasts are bone cells that are responsible for bone resorption, which is the breaking down of bones and providing space for new bone marrow to grow. An individual with osteopetrosis has osteoclasts that do not function properly, therefore their bones are not healthy (Stocks, Wang, Thompson, Stocks, & Horwitz, 1998).
The term biomechanics means the study of the structure and function of biological systems using the methods of mechanics. Biomechanics studies the process of kinematics and develops artificial limbs and footwear specifically to aid the body in performance. The study of biomechanics also includes the stress testing on crash dummies in car accidents and any sport where stress is placed on the body in order to produce performance. The type of stress specifically is the joint stimulation and bone modeling stress.
The most common musculoskeletal disorder and a major cause of disability in people over 65 years is osteoarthritis (OA) (Felson DT et al, 1987) (1). According to World Health Organization (WHO) report, OA of knee is more likely to become the fourth most important cause of disability in women, and the eighth most important cause in men (Murray CJL, Lopez AD, 1997)(2) . Primary prevention of knee OA has become a major health care aim and a clear understanding of the risk factors is required to design preventive strategies. Many investigations reported obesity, previous history of knee injury, sedentary life style, hand OA (Heberden’s nodes), and a familial history of the disease are major risk factors for OA of knee (Cyrus Cooper et al, 2000) (3). In spite of recent advancements the causes and pathogenesis of knee OA remains largely unknown (A Teichtahl, A Wluka, F M Cicuttini, 2003) (4) but however there is increasing research interest in the contribution of biomechanical variables on progression and management of the disease (Andriacchi TP, 1991) (5).
Describe the microscopic features of osseous tissue that help long bones withstand compressive forces without breaking.
According to Smithson, Walmart can expand its markets to new and emerging markets especially in the third world countries, which can significantly increase its revenues. Secondly, the company can reform is employment practices and improve the quality standard and in doing so, attract more customers and improve its brand image. On the other hand, the company faces threats such as the rising healthy lifestyle trend I that the company in most cases does not provide customers with healthy goods. At the same time, the company can capitalize on this aspect and increase its revenues. Aggressive competition from other discount retailers such as Target creates a great threat to the company (Smithson, 2015).
Bone Homeostasis is the bones regulation spefic process Inorder to allow the body to function properly.
The cytoskeleton is a highly dynamic intracellular platform constituted by a three-dimensional network of proteins responsible for key cellular roles as structure and shape, cell growth and development, and offering to the cell with "motility" that being the ability of the entire cell to move and for material to be moved within the cell in a regulated fashion (vesicle trafficking)’, (intechopen 2017). The cytoskeleton is made of microtubules, filaments, and fibres - they give the cytoplasm physical support. Michael Kent, (2000) describes the cytoskeleton as the ‘internal framework’, this is because it shapes the cell and provides support to cellular extensions – such as microvilli. In some cells it is used in intracellular transport. Since the shape of the cell is constantly changing, the microtubules will also change, they will readjust and reassemble to fit the needs of the cell.
A familiar lesson in elementary history might be that a conquered people will generally acculturate into the dominant culture of their conquerors. However, the process of how these two cultures interact is often not that simple. For example, the term transculturation was coined in the 1940s by sociologist Fernando Oritz to describe the process by which a conquered people choose and select what aspects of the dominant culture they will assume (Pratt 589). Unlike acculturation, transculturation recognizes the power of the subordinate culture to create its own version of the dominant culture. In an essay entitled, "The Arts of the Contact Zone," author Mary Louise Pratt argues that transculturation does not have to be confined to the social spaces where disparate cultures intersect; it can be extended to everyday situations, such as the classroom. However, though Pratt recognizes that transculturation can take place on a very personal level, she still fails to discuss the emotional nature of transculturation. An analysis of Derek Walcott's poem, "A Far Cry from Africa," using scholar Homi Bhabha's concept of "mimicry" will give a deeper understanding of Pratt's vision of transculturation by redefining it as a process of personal struggle by which each individual in a subordinate group is moved to choose and select which aspects of the dominant culture he or she will assume.