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Cell structure, function and adaptation
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
There are many theories and putative remedies for ageing, many of which may have some validity, but none of which is enough to explain the phenomenon. There is still uncertainty about how far ageing should be regarded as pathological and resisted or normal and accepted gracefully. Houseflies have a short lifespan, giant tortoises a long one. Humans, domestic animals, and birds are intermediate in lifespan and in size. The generation of hydrogen peroxide as a function of body mass is inversely proportional to life expectancy, suggesting that oxygen free radical generation may be a major determinant in acquiring wear-and-tear injury. For some cells, loss is irreplaceable, e.g. permanent cells such as neurons and cardiomyocytes, whereas other stable or labile cell populations may be regenerated, at least for a time. Oxygen free radicals damage proteins, membranes, RNA, DNA, and perhaps mitochondrial DNA, which is repaired less efficiently than nuclear DNA and codes for proteins involved in oxidative phosphorylation. Severe calorie restriction of laboratory rodents increases their lifespan by up to 50%. A sedentary lifestyle, such as that enjoyed by the giant tortoise, may also be important but sloth has its own disadvantages, as exemplified by its association with an increased risk of ischaemic heart disease (see Chapter 7).
The cell
Published in Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella, Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella
Repair by RegenerationWith regeneration, the injured tissue is repaired with the same tissue that was lost. A full return of function occurs and afterwards there is little or no evidence of the injury.Repair by regeneration can only occur in labile cells (cells that continue to divide throughout life) or stable cells (cells that have stopped dividing but can be induced to regenerate under appropriate conditions of injury). Examples of labile cells include those of the skin, oral cavity and bone marrow. Examples of stable cells include hepatocytes of the liver. Certain cell such as nerve cells and cardiac muscle cells are fixed cells and cannot undergo regeneration under any circumstances. These cell types are only capable of repairing injuries through connective tissue replacement.
Wound care
Published in Tor Wo Chiu, Stone’s Plastic Surgery Facts, 2018
Cells can be classified according to their proliferative potential: Labile cells divide and proliferate throughout life (M to G1 of the cell cycle), e.g. epithelia, bone marrow haematopoietic cells.Stable cells are normally quiescent but can be stimulated to replicate (G0 to G1), e.g. hepatocytes, endothelium, mesenchymal cells, e.g. osteoblasts.Permanent cells have left the cell cycle and cannot undergo mitosis (postnatally) and thus are never regained after loss, e.g. neurones, cardiac muscle.
Combination Therapy of Allopurinol and Dantrolene and Its Role In The Prevention of Experimental Ischemia Reperfusion Injury Of The Small Intestine
Published in Journal of Investigative Surgery, 2021
Beatriz Prieto-Moure, Dolores Cejalvo-Lapeña, Mariola Belda-Antolí, Carolina Padrón-Sanz, José Miguel Lloris-Cejalvo, José Miguel Lloris-Carsí
The bowel is composed of labile cells that are easily injured by ischemia. Later intestinal reperfusion results in additional damage to the mucosa. The enterocytes that are located at the tip of the villi are more sensitive to ischemia [28]. Our experimental model for investigating I/R injury in rat intestines and involving the superior mesenteric artery (SMA) has been well standardized. The period of I/R can be controlled, and the method can be applied equally to all experimental groups.