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Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The innermost layer of the cornea is the endothelium. The origin of this layer is thought to be the neural crest cells.6,9,10 The endothelium is a single cell layer of hexagonal cells, 15 to 20 μm in diameter, attached to each other by terminal bars (Figure 6).5,6 In most species these cells are capable of mitosis only very early in life. The exception to this is the rabbit, in which the endothelium is capable of undergoing mitosis.10 The greatest cell density of the endothelial cells is in the neonate.10 Overall, their number per mm2 continues to decrease with age, first as they spread to cover the enlarging cornea and later as they decline with aging.6,10,11 Surprisingly, it would appear that the adult cornea of most species has a central endothelial cell density of approximately 2500 cells/mm2,10,11 Once damaged, endothelial cells repair defects through enlargement and spreading rather than by replacement. A minimum cell density of 1000 cells/mm2 appears to be required to maintain corneal deturgesence. In addition to the number of endothelial cells, it appears that the morphology correlates with function. With age comes an increase in variability in cell size and shape which correlate with a decrease in function.11,12
Nutrient Metabolism and Fetal Brain Development
Published in Emilio Herrera, Robert H. Knopp, Perinatal Biochemistry, 2020
George E. Shambaugh, Boyd E. Metzger, James A. Radosevich
Early reports on brain development in the rat described an orchestrated series of events. They are characterized by proliferative growth with an increase in cell number, largely in the cerebral cortex, followed by an increase in cell number in the cerebellum.49 By the fourteenth postnatal day, cell division slows while protein and weight continue to increase. The concept that brain growth proceeded through a phase of cell division with no change in cell size followed by a phase of cell division and enlargement with a final phase of cell enlargement was formulated.50 Later studies showed, however, that very early in development the mean cell size increases during the cell proliferation and that some cell multiplication continues until growth ceases. Since growth retardation during the phase of cell proliferation can result in a permanent loss in cell number,51 nutritional insult later in development might be predicted to result in just as much damage as earlier in development.52
Quantitative Evaluation of Minimal Injuries
Published in Joan Gil, Models of Lung Disease, 2020
Specific cell characteristics can be derived to assess the response of individual cell types to minimal injuries. While changes in tissue volumes and thicknesses may indicate the extent of an injury, they reveal little about the mechanism of injury. Changes in cell characteristics such as cell number, cell size, and cell shape can reveal individual cell susceptibility, cell ability to differentiate or regenerate, and relationships between cell populations as well as between cells and matrix components.
The discovery of berberine erythrocyte-hemoglobin self-assembly delivery system: a neglected carrier underlying its pharmacokinetics
Published in Drug Delivery, 2022
Qiuxia Yu, Minhua Li, Hanbin Chen, Lieqiang Xu, Juanjuan Cheng, Guoshu Lin, Yuhong Liu, Ziren Su, Xiaobo Yang, Yucui Li, Jiannan Chen, Jianhui Xie
Most current pharmacokinetics studies only focus on the concentration of free drugs in plasma (Zuo et al., 2006; Gong et al., 2014), while a study on the role of other major components in blood like erythrocyte is rare and insufficient. Indeed, among the cellular constituents of blood, the erythrocytes represent, by far, the largest population both in number and cell size. Erythrocytes have a remarkably long life span and a widespread circulation throughout the body, and have become a natural drug carrier with incomparable superiorities of biocompatibility and biodegradability (Szumiło, 2013; Koleva et al., 2020). Erythrocytes can quickly identify the targeted delivery including drug molecule, transport that to the target site and accumulate in the liver (Fan et al., 2012b). Hence, erythrocytes have currently been considered as an excellent site-targeted delivery system (Hamidi et al., 2007).
The balance between cell survival and death in the placenta: Do neurotrophins have a role?
Published in Systems Biology in Reproductive Medicine, 2022
Prachi Pathare-Ingawale, Preeti Chavan-Gautam
A continual balance of cell growth (increase in cell size and number) and cell death is essential throughout life for proper development and homeostasis of tissues (Mason and Rathmell 2011). The cells that receive the appropriate signals can survive and proliferate, while cells that fail to receive them, such as excess or damaged cells, undergo apoptosis or programmed cell death. The term ‘apoptosis’ describes a particular morphology of physiological cell death involving cell shrinkage, nuclear condensation, membrane blebbing, and cellular and nuclear fragmentation into membrane-bound apoptotic bodies (Kerr et al. 1972). Primarily, apoptosis is a mechanism involved in removing damaged or dysfunctional cells in response to exogenous or endogenous stimuli for maintaining the normal function of tissues (Norbury and Hickson 2001; D’Arcy 2019). Apoptosis is a normal feature of development and aging. It functions to maintain the shape and structure of tissues and organs and acts as a homeostatic mechanism to maintain cell populations (Elmore 2007). Likewise, apoptosis also plays an important role in the placenta’s normal development, function, and aging.
Evaluating the thermal performance of a balloon-based renal sympathetic denervation system with array electrodes: a finite element study
Published in Electromagnetic Biology and Medicine, 2021
Yanyan Cheng, Hongxing Liu, Zhen Tian, Meng Zhang, Youjun Liu, Qun Nan
The numerical method utilized in the model is a time-stepping 3D finite-volume scheme. A grid independence study was carried out to obtain the optimum number of mesh cells. Figure 4 shows that the computational results have little dependence on the grid numbers. A free tetrahedral mesh was used to discretize the physical domains of the model, which was divided into three parts: the abdomen (part 1); the blood and renal artery wall (part 2); and the balloon, catheter, guidewire, and electrodes (part 3). Corresponding numbers of mesh cells were 81289 at part 1, 135229, and 1097215 at part 2. In part 3, the mesh cells were 37173, 20929, 14540, and 13666, respectively. The minimum element size was 0.19 mm, the maximum cell size was 5 mm, and the average element size was 0.67 mm.