China
Africa
Explore chapters and articles related to this topic
Pathophysiology of Fluorosis and Calcium Dose Prediction for Its Reversal in Children: Mathematical Modeling, Analysis, and Simulation of Three Clinical Case Studies
Published in P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas, Advanced Studies in Experimental and Clinical Medicine, 2021
Suja George, A. B. Gupta, Mayank Mehta, Akshara Goyal
The presence of increased PTH in the blood stream is responsible for the following two major body mechanisms: Significant Loss of Bone Mass: Bone loss is due to increase in the number of osteoblasts and the increase of their activity [9, 10] which causes the stimulation of bone resorption and depletion of bone mass as well as its formation. Osteoclast is a type of bone cell that resorbs bone tissue. Under the normal conditions, where there is an increase in bone resorption, it gets coupled with an effective compensatory increase in an equal magnitude of bone formation and therefore no net bone mass is depleted in the skeletal system. However, during the adjustor mechanism if there is a demand to mobilize calcium from skeletal system to counteract the effects of hypocalcemia, then the bone coupling process gets compromised.Depletion of Bone Formation: It has been reported that despite the effectiveness in a significant increase in bone resorption, bone formation decreased and was significantly inhibited due to PTH [9]. Therefore, the combination of various combined actions such as calcium depletion, bone resorption and decrease in its formation led to a significant loss of bone mass [9].
Biochemistry of Exercise Training: Effects on Bone
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Panagiota Klentrou, Rozalia Kouvelioti
Bone is a dynamic tissue, which responds to various signals, including chemical, mechanical, electrical, and magnetic stimuli. Information is transferred across the cell's cytoplasm to the nucleus via binding of a signal ligand to either cell membrane receptors or intracellular receptors (cytoplasmic or nuclear, respectively). There are three types of bone cells: osteoblasts, osteocytes, and osteoclasts. Osteogenic cells are not specialized and derive from mesenchyme embryonic tissue, the tissue from which all connective tissues are formed (69). These cells differentiate into osteoblasts during bone development and repair, in the embryonic stage and in injury, respectively (21). Osteoblasts are the major bone formation cells that initiate calcification, regulate osteoclasts, make the extracellular matrix of bone tissue and produce osteoid, the uncalcified organic matrix of bone. Osteoblasts are approximately 15–30 microns in size and are cuboidal-shaped. They have a large nucleus localized in the bottom half of the cytoplasm, an abundant endoplasmic reticulum, enlarged Golgi apparati, and collagen-containing secretory vesicles. They are responsible for the laying down of new matrix (collagen and hydroxyapatite) on bone surfaces in the process of bone formation and play a critical role in the regulation of bone turnover. They also synthesize and secrete collagen protein to form the osteoid, which then becomes calcified through the depositing of hydroxyapatite by the osteoblasts (90).
Management of osteoporotic proximal intertrochanteric/subtrochanteric femoral fractures
Published in Peter V. Giannoudis, Thomas A. Einhorn, Surgical and Medical Treatment of Osteoporosis, 2020
Avadhoot Kantak, George Tselentakis
To understand how excessive bone resorption and inadequate formation result in skeletal fragility, it is necessary to understand the process of bone remodeling, which is the major activity of bone cells in the adult skeleton. The bone remodeling or bone multicellular units (BMUs) described many years ago by Frost (39) can occur either on the surface of trabecular bone as irregular Howship lacunae or in cortical bone as relatively uniform cylindrical haversian systems. The process begins with the activation of hematopoietic precursors to become osteoclasts, which normally requires an interaction with cells of the osteoblastic lineage. Because the resorption and reversal phases of bone remodeling are short and the period required for osteoblastic replacement of the bone is long, any increase in the rate of bone remodeling will result in a loss of bone mass. Moreover, the larger number of unfilled Howship lacunae and haversian canals will further weaken the bone. Excessive resorption can also result in complete loss of trabecular structures, so that there is no template for bone formation. Thus, there are multiple ways in which an increase in osteoclastic resorption can result in skeletal fragility. However, high rates of resorption are not always associated with bone loss, for example, during the pubertal growth spurt. Hence, an inadequate formation response during remodeling is an essential component of the pathogenesis of osteoporosis (38).
Subcutaneous testosterone pellet therapy for reversal of male osteoporosis: a review and case report
Published in The Aging Male, 2023
Bruce Dorr, Ahmed Abdelaziz, Mickey Karram
Each year, more than 8 million men are diagnosed with osteoporosis or osteopenia [1]. Men with osteoporosis are treated with lifestyle modifications, drug therapy, and hormonal therapy if they have been diagnosed with testosterone deficiency (TD). However, normal testosterone ranges remain a somewhat controversial area. Integrity of our skeletal system is maintained by a remodeling process, which is regulated by three bone cell types: bone-forming osteoblasts, bone-resorbing osteoclasts, and mechanically sensitive osteocytes. These are under regulation by many processes, which involve testosterone and androgen receptors as well as the effect of estrogen receptors that are known to be influenced by testosterone levels. Osteoporosis risk factors are best documented in women due to the acute estrogen loss at menopause, but they also consistently lose testosterone similar to men. Fracture risk is higher in women, but men suffering from fractures carry a greater mortality risk over women [2,3]. Administrative therapy also plays a key role. Problems in both obtaining and maintaining effective testosterone levels to achieve the desired therapeutic effect are critical in the process and clinical outcome [4].
Irradiation affects the structural, cellular and molecular components of jawbones
Published in International Journal of Radiation Biology, 2022
Sridhar Reddy Padala, Bina Kashyap, Hannah Dekker, Jopi J. W. Mikkonen, Anni Palander, Nathalie Bravenboer, Arja M. Kullaa
Bone remodeling is a dynamic process; it occurs throughout the lifetime of an organism in a coordinated and tightly regulated manner in order to maintain a functional skeletal system. The bone remodeling process involves two opposing processes – bone resorption and bone formation (Mello et al. 2018) executed by three distinct cell types present in bone cells; osteoclasts, osteoblasts, and osteocytes. The physiological process of bone remodeling is based on the interactions not only between these cells but also multiple molecular agents including hormones, growth factors, and cytokines (Feng and McDonald 2011). Bone turnover is necessary to allow new bone to replace the existing bone, ensuring the adaptation of the newly formed bone to its microenvironment (Misch et al. 2001). Exposure to radiation causes a deterioration of the quantity and quality of bone by interfering with bone remodeling/turnover activity which ultimately impacts on the bone’s microstructure (Costa and Reagan 2019).
Green nanotechnology-based drug delivery systems for osteogenic disorders
Published in Expert Opinion on Drug Delivery, 2020
David Medina-Cruz, Ebrahim Mostafavi, Ada Vernet-Crua, Junjiang Cheng, Veer Shah, Jorge Luis Cholula-Diaz, Gregory Guisbiers, Juan Tao, José Miguel García-Martín, Thomas J. Webster
The skeletal system forms the internal framework of the human body, which is tasked with performing vital functions needed for survival, such as support, movement, protection, blood cell production, calcium storage and endocrine regulations. Along with cartilage, bone is one of the skeletal system’s tissues- a dynamic organ that is continuously undergoing remodeling processes, in order to maintain a healthy and life-long execution of essential skeletal functions [1,2]. Therefore, it is vital that the bone adjusts to different mechanical changes by varying environmental conditions. Bone tissue is made of three types of bone cells and while osteoblasts and osteocytes are actively involved in the formation of bone (mineralization), osteoclasts are tasked with the resorption of bone tissue. Bone is generally classified as either cortical or trabecular. While cortical bone is relatively denser, trabecular bone is the primary place of bone remodeling; and hence, trabecular bone is the main site for the appearance of bone disorders [3,4].