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The cell and tissues
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
There are two broad types of transport across plasma membranes. The first is passive transport, which, by its very nature, does not require any energy input. Passive transport can be subdivided into four categories; diffusion, facilitated diffusion, osmosis and filtration.
Toxicokinetics
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
The simplest mechanism for the transportation of molecules involves diffusion, defined as the transport of molecules across a semi-permeable membrane. The most common pathway of diffusion is passive transport. In passive transport, molecules are transported from an area of high to low solute concentration—that is, down the concentration gradient. It is not an energy-dependent process, and no electrical gradient is generated. Lipophilic molecules, small ions, and electrolytes generally gain access through membrane compartments by passive diffusion, since they are not repelled by the phospholipid bilayer of the cell membrane. Most passive diffusion processes, however, are not molecularly selective.
Overview of the cardiovascular system
Published in Neil Herring, David J. Paterson, Levick's Introduction to Cardiovascular Physiology, 2018
Neil Herring, David J. Paterson
Diffusion is a ‘passive’ transport process, in the sense that it is driven by the rapid, random thermal motion of molecules, not by metabolic pumps. When a concentration gradient is present, the randomly directed step movements of individual solute molecules result in a net movement down the concentration gradient, i.e. a net diffusive transport (Figure 1.1).
Therapeutic effects of Bombax ceiba flower aqueous extracts against loperamide-induced constipation in mice
Published in Pharmaceutical Biology, 2023
Liuping Wang, Shiyuan Xie, Xuan Jiang, Caini Xu, Youqiong Wang, Jianfang Feng, Bin Yang
Aquaporins are mainly expressed in the intestinal canal (Sun et al. 2020), which mediate the passive transport of free water across biofilm, thereby maintaining the homeostasis of the intracellular and extracellular environment (Matsuzaki et al. 2004). Moreover, the abnormal expression of aquaporins in the gastrointestinal tract is related to the occurrence of some diseases, such as constipation, gastritis, diarrhoea and gastric cancer (Liu et al. 2020). AQP3 is an important aquaporin located in the colon and is permeable to water (Li and Wang 2017). Previously studies have revealed the relationship between AQP3 and constipation, particularly morphine-induced constipation (Kon et al. 2015), promotes AQP3 expression level in the colon and subsequently increases water absorption from the luminal side to vasculature, which dries and hardens stool (Ikarashi et al. 2016). In the present study, the expression level of AQP3 was detected and the results showed that phenolphthalein and BCE relieve the symptoms of loperamide-induced constipation by decreasing the level of AQP3 in the colon of mice. However, the precise mechanisms remain to be further elucidated.
Toxicological profile of lipid-based nanostructures: are they considered as completely safe nanocarriers?
Published in Critical Reviews in Toxicology, 2020
Asaad Azarnezhad, Hadi Samadian, Mehdi Jaymand, Mahsa Sobhani, Amirhossein Ahmadi
Transmission through the CM is either passive or active. In the passive transport, an ion or molecule moves in the direction of the electrochemical gradient or its concentration. This type of transfer is performed without the assistance of energy (ATP) and is occurred in two ways: simple and facilitated diffusion. However, the active transport uses energy to transfer ion or molecule against the concentration of electrochemical gradient (Murphy 2009; Singh et al. 2009). Polar or charged biomolecules that cannot pass through the hydrophobic plasma membrane are internalized by a form of active transport which is called endocytosis. Broadly speaking, the internalization routs can be classified as nonspecific pathways including: (i) pinocytosis (cellular drinking that involve small pinocytic vesicles (≈100 nm)) or (ii) macropinocytosis involving large vacuole formation (0.2–0.5 μm), as well as specific pathways such as (iii) clathrin- or caveolin-mediated endocytosis (the protein-coat-driven route) or (iv) phagocytosis of objects larger than 0.5 μm by specialized phagocytes (Tan et al. 2019).
Activated human astrocyte-derived extracellular vesicles modulate neuronal uptake, differentiation and firing
Published in Journal of Extracellular Vesicles, 2020
Yang You, Kathleen Borgmann, Venkata Viswanadh Edara, Satomi Stacy, Anuja Ghorpade, Tsuneya Ikezu
Interleukin-1β (IL-1β) is a classic pro-inflammatory cytokine and regulates the inflammatory response to brain injury. It is primarily produced by microglia and astrocytes in the CNS and one of the critical regulators for induction of reactive astrocyte phenotype [5]. IL-1β stimulation of astrocytes initiates nuclear factor kappa B (NFκB) signalling, resulting in increased expression of neurotoxins, such as glutamate and nitric oxide, ensuring neurodegeneration [6,7]. In addition, IL-1β also up-regulates Fas ligand in reactive astrocytes to induce neuronal apoptosis [8]. It remains largely unknown how glial molecules are transmitted to neurons. Previous evidence suggested several mechanisms might be involved in this process, including exocytosis, diffusion and active/passive transport [9]. Recent advancements indicate that extracellular vesicles (EVs) might play an important role in glia-neuron communication during neurodegenerative states or inflammation [10].