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CelIs as physical objects
Published in A. Šiber, P. Ziherl, Cellular Patterns, 2018
The cell membrane is generally rather rough and laden with wrinkles, folds, protrusions, and pockets which may serve as an area reservoir. If the membrane is stretched, these features can unwrinkle so as to increase the effective exposed membrane area, thus accommodating deformations where this is needed. Such deformations are particularly prominent in neutrophil cells, a type of white blood cells of the immune system of vertebrates. During phagocytosis, i.e., engulfment of foreign material, bacteria, dead cells, etc., neutrophils spread around the particle that they are about to digest. In this process, they can double their effective area [6]. Also indicated in Figure 2.1 are microvilli, easily recognizable fingerlike protrusions. They are particularly prominent in some cell types such as the epithelial cells of small intestines where the presence and organization of microvilli in brush‐like structures immensely increases the area available for absorption. Microvilli are stabilized by the underlying cytoskeleton, that is, by protruding protein filaments which act as their scaffold. Not only microvilli, but the whole cell surface is supported by protein filaments whose dynamics and reorganization induce changes of cell shape and surface. These filaments can extend by incorporating more proteins in their structure, or they can shorten by partially disassembling and releasing some of the protein units. The cytoskeleton consists of three types of filaments made of different proteins and characterized by different radii: microtubules, intermediate filaments, and actin filaments. Microtubules are polymers of tubulin dimers and are the thickest of all, with a diameter of ≈ 25nm. Intermediate and actin filaments have diameters of ≈ 10 and 7 nm, respectively.
Biomedical Application of Membranes in Bioartificial Organs and Tissue Engineering
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
Thomas Groth, Xiao-Jun Huang, Zhi-Kang Xu
Kidney and liver consist of connective tissue, endothelial, and epithelial cells. Epithelial cells which represent the functional units, such as distal and proximal tubule cells in the kidney or hepatocytes in the liver, have a polar organization where the cell is separated into an apical and a baso-lateral region. Main morphological characteristic of epithelial cells is the presence of tight junctions and microvilli on the apical cell part, which are both related to transepithelial transport processes (Fromm and Hierholzer 1997). Tight junctions separate the basal and apical region preventing or controlling the exchange of solutes along concentration gradients. Microvilli on the apical cell surface increase the surface area for the uptake of substances and are an important feature of many epithelia as well. Typical epithelia have a planar structure with an underlying complex of basal membranes composed of different extracellular matrix proteins, such as collagen IV, fibronectin, laminin, etc. (Lodish et al. 1995). Figure 23.14 shows the typical morphology of a kidney epithelial cell with the presence of a tight junction between neighboring cells and microvilli on the apical region obtained by transmission electron microscopy.
Plant pharmacology: Insights into in-planta kinetic and dynamic processes of xenobiotics
Published in Critical Reviews in Environmental Science and Technology, 2022
Tomer Malchi, Sara Eyal, Henryk Czosnek, Moshe Shenker, Benny Chefetz
The rhizosphere continuum can be understood as an inside out gastrointestinal tract, with multiple analogies existing between these two systems (Alaoui-Sossé et al., 2004; Barberon & Geldner, 2014). Both systems are responsible for nutrient acquisition and functions related to immunity and defense. Both systems are analogous in terms of their functions and roles of their immense and diverse symbiotic microbiome. Furthermore, the formation and function of the microvilli in the small intestine are analogous to plant root hairs, as both structure increase surface area for nutrient absorption. These two systems function in different environments in terms of pH, oxygen levels and nutrient concentration and gradients (Mendes & Raaijmakers, 2015; Ramírez-Puebla et al., 2013). The absorption pathways, although described with different terminologies, are also analogous to each other (Buxton & Benet, 2013).
An assessment of copper, zinc and cadmium contamination and their ecotoxicological effects in O. mediterranea Costa, 1853 (Amphipoda, Talitridae)
Published in Chemistry and Ecology, 2019
Raja Jelassi, Chedliya Ghemari, Hajer Khemaissia, Maryline Raimond, Catherine Souty-Grosset, Karima Nasri-Ammar
As inventoried in other crustaceans species [27,36,60,61], the hepatopancreas of metals contaminated animals showed some significant alterations. The most significant changes due to the cadmium, the zinc and the copper exposures affected firstly the disorganisation of microvilli. These last undergo a progressive or a total destruction. This result was in accordance with the observation of Collins [58] highlighting that the microvilli border were the most affected ultrastructure in the F-, R- and B-cells of freshwater prawns. The same features were described in the terrestrial isopods species namely Porcellio scaber [33], Armadillidium vulgare and Porcellio laevis contaminated with a high concentration of Cd and lead [36] as well as in Ligia italica subjected to mercury contamination [62]. Ghadially [63], and Clifford and Witkus [64] highlighted that the shortening, destruction or reduction functionality of the microvilli border has an adverse effect on the absorption of nutrients by the hepatopancreas.
Microencapsulation of antioxidant phenolic compounds from green coffee
Published in Preparative Biochemistry and Biotechnology, 2019
Nivas M. Desai, Devendra J. Haware, K. Basavaraj, Pushpa S. Murthy
The intestinal absorption of dietary phenol from green coffee involves sequential steps: the breakdown of the food matrix to release its derivatives, dispersion, solubilization, and movement across the unstirred water layer adjacent to the microvilli and uptake by the cells of the intestinal mucosa and incorporation into chylomicrons.[20] The percent micellarable CGA in vitro was higher (71%) in encapsulated samples than non-encapsulated (Table 4).