China 
Africa 
Explore chapters and articles related to this topic
Cell Components and Function
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Ion channels are membrane-spanning proteins that form pores that allow ion transport. These channels are selective and conduct ions across electrochemical gradients at a high rate. External signals cause ion channels to undergo conformational changes. Depending on the signal, the ion channels may ‘open’ or ‘close’, a process called gating. The gate is a region of the protein channel that prevents ion flow in the closed state. Ion channels may be (i) ligand-gated (gating mediated by a neurotransmitter or chemical binding to sensor region of the channel), (ii) voltage-gated (membrane potential changes near channel) or (iii) mechanosensitive (activation by pressure, stretch or temperature).
Freeze Fracture in Lung Research
Published in Joan Gil, Models of Lung Disease, 2020
Further specialized membrane structures include orthogonal arrays of particles (OAP) that have been observed in the basal plasma membrane of pneumocytes in turtles and frogs and in human type I pneumocytes (Bartels and Miragall, 1986). Such orthogonal arrays appeared to be absent from pneumocytes in other mammalian species, but were present in the basal plasma membrane of airway epithelial cells in a variety of species (Inoue and Hogg, 1977; Gordon, 1985). The number of particles per OPA ranged from 4 to 40 in lower vertebrates and from 4 to 24 in humans (Bartels and Miragall, 1986). It is interesting that their number appeared to increase substantially following acute or chronic exposure to NO2 (Gordon, 1985). Although a possible role in the regulation of ion transport has been suggested, their function is at present unclear.
Effect of Transport on Distribution of Radioions and Radiometabolites
Published in Lelio G. Colombetti, Biological Transport of Radiotracers, 2020
(1) One of the main roles of ion-transport systems is that of feeding and regulating metabolism, and (2) that ion transport, through establishment of ionic gradients, can be directly utilized to drive other transport systems.73
Efficient simulations of stretch growth axon based on improved HH model
Published in Neurological Research, 2023
Xiao Li, Xianxin Dong, Xikai Tu, Hailong Huang
The axon starts the second stage of growth when the growth cone reaches the target cell and creates a synaptic connection with it. During this stage, integrated axons crossing increasingly distant body regions are subjected to continuous mechanical tension [24]. The modified HH axon model simulates the generation and propagation of action potentials evoked by mechanical stimuli successfully. Traction stimulation is administered rapidly in the center of the axon, and the resulting action potential propagates in two directions. After mechanical traction stimulation, the axon grows in length, diameter, and area of the membrane. Due to the fact that the number of ion channels on the membrane is directly proportional to its area, the ion transport speed of the cell membrane rises, resulting in a decrease in membrane resistance. The shift in membrane capacitance is illustrated in Figure 5, when stretch growth axons are triggered again by mechanical strain. Within 1 ms, the membrane capacitance rapidly increases from the constant value.
Solanaceae glycoalkaloids: α-solanine and α-chaconine modify the cardioinhibitory activity of verapamil
Published in Pharmaceutical Biology, 2022
Szymon Chowański, Magdalena Winkiel, Monika Szymczak-Cendlak, Paweł Marciniak, Dominika Mańczak, Karolina Walkowiak-Nowicka, Marta Spochacz, Sabino A. Bufo, Laura Scrano, Zbigniew Adamski
Nevertheless, SGAs affect not only passive but also active ion transport. For example, α-solanine was found to inhibit active calcium transport in a rat duodenum (Michalska et al. 1985), and α-chaconine or α-solanine decreased the transepithelial active transport of sodium ions in frog skin (Blankemeyer et al. 1995, 1997). Moreover, the above data suggest that SGAs might act both in channels ion transporter-dependent and ion transporter-independent ways. Moreover, SGAs interact with cell membrane cholesterol. α-Solanine and α-chaconine can form tubular structures within cell membrane monolayers in artificial phospholipid vesicles, increasing the permeability of membrane structures for different ions (Keukens et al. 1995, 1996). Thus, the effects of SGAs on ion balance might change the cell membrane potential and thus modulate the activity of excitable cells, including myocardial cells. Blankemeyer et al. (1998) showed that solasonine and solamargine decrease the cell membrane potential (hyperpolarization) in frog embryo cells. If the same occurs in myocardial cells, it could explain the cardioinhibitory properties of SGAs.
In vitro study of the effects of DC electric fields on cell activities and gene expression in human choriocarcinoma cells
Published in Electromagnetic Biology and Medicine, 2021
Jinxin Chen, Linbo Guan, Ping Fan, Xinghui Liu, Rui Liu, Yu Liu, Huai Bai
All cell types and intracellular organelles maintain transmembrane electrical potentials owing to asymmetric ion transport. For instance, in human adipose tissue-derived stem cells, there are channels for a Ca2+-activated k+ current, transient outward k+ current, delayed rectifier-like k+ current, and tetrodotoxin-sensitive transient inward Na+ current (Bai et al. 2007). In trophoblast cells, there are several types of molecules on the cell membrane that may be associated with TEP production. These molecules include Na-K pumps (Na-K ATPase) and Na-H exchangers. Based on the above reports and the present finding that choriocarcinoma cells are responsive to EF signals, we speculate that EF might exert a profound influence on the choriocarcinoma cell function via direct activation of ion channels.