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The cell and tissues
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
The difference in concentration between areas of high and low concentration is called the concentration gradient. It is this difference in concentration that creates diffusion. The concentration may simply refer to the number of atoms or molecules in a given volume or may refer to the electrical concentration. Examples of diffusion would be the movement of dissolved oxygen from the alveoli of the lungs to the blood in the capillaries surrounding the alveoli. The movement of carbon dioxide in the opposite direction is also achieved by diffusion. The diffusion across the alveoli is dependent on the distance (the diffusion pathway). If this is extended for any reason, e.g., if there is inflammation or scarring from previous episodes of injury and healing, then the distance across the diffusion pathway is extended, which can seriously affect the supply of oxygen and the removal of carbon dioxide.
Glaucoma
Published in Mostafa Khalil, Omar Kouli, The Duke Elder Exam of Ophthalmology, 2019
Omar Kouli, Rizwan Malik, Stewart Gillan
The ciliary body is made from the pars plicata anteriorly and pars plana posteriorly. The aqueous humour is formed by the ciliary processes in the pars plicata.There are three mechanisms of secretion: Diffusion: Due to a concentration gradient.Ultrafiltration: Pressure gradient between oncotic and hydrostatic pressures (capillary versus intraocular pressures).Active (∼80%): Active transport is mediated by transmembrane aquaporin activated by Na+/K+ ATPase enzyme and carbonic anhydrase enzyme.Control of aqueous secretion is controlled by the sympathetic (adrenergic innervation) system. β2 receptor stimulation increases aqueous secretion; however, α2 receptor stimulation decreases aqueous secretion.
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
Osmosis is the net movement of water through a semipermeable membrane down its own concentration gradient from an area of high water concentration to an area of low water concentration. Water is a small, polar molecule that can easily diffuse across plasma membranes through small intermolecular spaces. This movement of water across cell membranes in some tissues (e.g., kidney) may be significantly facilitated by the presence of a group of membrane proteins that form channels referred to as aquaporins.
Advance in placenta drug delivery: concern for placenta-originated disease therapy
Published in Drug Delivery, 2023
Miao Tang, Xiao Zhang, Weidong Fei, Yu Xin, Meng Zhang, Yao Yao, Yunchun Zhao, Caihong Zheng, Dongli Sun
Transporter-mediated uptake is divided into facilitated diffusion and active transport. Facilitated diffusion allows certain compounds to cross the placenta without energy. Active transport is an energy-dependent process that usually proceeds against a concentration gradient. The major superfamily of transporters found in the placenta are the SLC and ABC transporters (Al-Enazy et al., 2017; Staud et al., 2012). For instance, organic anion transporters are a family of transporters in the placenta, mediating transport in the maternal-fetal interface for metabolites, waste products, and hormones (Lofthouse et al., 2018). Similarly, transporters such as amino acid transporters, glucose transporters, and transferrin can deliver specific substrates across the placenta (Illsley, 2000; Parkkila et al., 1997). For example, iron is transported across the placenta through transferrin receptor-mediated endocytosis (Parkkila et al., 1997).
Development and evaluation of a drug-in-adhesive transdermal delivery system for delivery of olanzapine
Published in Expert Opinion on Drug Delivery, 2022
Skin has been extensively studied and established as a promising route for topical and transdermal delivery of various therapeutic agents [17]. A moderately lipophilic drug having log P of about 1 to 3 and a molecular weight less than 500 Da can permeate passively into the skin and then diffuse out of the skin into the systemic circulation [17]. OZP is a molecule with log P of 2.9 and molecular weight of 312.4 Da, hence can be delivered transdermally via passive permeation. As a part of preliminary studies, we conducted in vitro permeation testing for OZP using dermatomed porcine ear skin. In vitro permeation testing indicated successful passive permeation, but the amount of drug delivered did not meet the desired target delivery. Concentration gradient remains one of the significant factors affecting the performance of topical or transdermal products [18]. The permeation of drugs into and across skin increases with an increase in the degree of saturation owing to an increased concentration gradient [19]. This underlined the importance of the degree of saturation of the drug in a topical or transdermal formulation and formed the basis of using a 90% saturated solution of OZP in the vehicles used as donor solutions for IVPT studies.
Synergistic inhibitory effect of Smo inhibitor jervine and its combination with decitabine can target Hedgehog signaling pathway to inhibit myelodysplastic syndrome cell line
Published in Hematology, 2021
Fang Zhao, Jie Wang, Liu Yao, Yu-ting Qin, Niluopaer Tuerxun, Huan Wang, Ming Jiang, Jian-ping Hao
In this study, the concentration gradient of Jervine and DAC was selected based on relevant literature reports and preliminary test results [18]. The logarithmic growth phase cells were inoculated into 96-well plates at 5 × 104 cells/mL, and 100μl cell suspension was inoculated per well. The experiment was divided into a blank control group, an experimental control group, and jervine (0, 1, 5, 10 μmol/L) and, DAC (0, 2, 5, 10μmol/L) treatment group, each group has set up 3 replicate holes. After culturing for 24, 48, and 72 h, add 10μl CCK8solution to each well, then continue the incubation for 4 h at 37°C, and 5% CO2 saturated humidity was maintained. Then, we used a microplate reader to detect the absorbance at 450 nm wavelength, and perform 3 independent repeat experiments, calculate changes in the cells vitality. Record and draw a histogram: draw a histogram with the drug concentration on the horizontal axis and the proliferation rate on the vertical axis. Take the blank control group without cells and the only medium, add 0 μmol/L jervine, 0 μmol/L DAC as the control group, the proliferation rate was calculated as [(absorbance value of the experimental group-absorbance value of the blank group) / (absorbance value of the control group -the absorbance value of the blank group)] × 100%.