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The Human Immune System Seen from a Biomedical Engineering Viewpoint
Published in Robert B. Northrop, Endogenous and Exogenous Regulation and Control of Physiological Systems, 2020
Immune system autacoids (also known as immunocytokines), including the interleukins, interferons, tumor necrosis factors, prostaglandins, and chemokines, are secreted by immune system cells and diverse somatic cells. These signaling substances must bind to receptor proteins on their target cells. After binding, specific internal biochemical processes are initiated, leading to events such as cell growth, differentiation, clonal expansion, and production of receptor proteins and other immunocytokines. Autacoid receptors and other immune system cell surface molecules are generally classified as cluster of differentiation (CD) antigens. Over 182 CD molecules have been described.169 For example, CD127 found on bone marrow lymphoid precursor cells, pro-B-cells, mature T-cells, and monocytes is the IL7 receptor; CD25 found on activated T-cells, B-cells, and monocytes is the receptor for IL2; and CD37 found on mature B- and T-cells and myeloid cells has unknown function.
Proteins and Proteomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
Many proteins are involved in the process of cell signaling and signal transduction. Some proteins such as insulin are extracellular proteins that transmit a signal from the cell in which they were synthesized to other cells in distant tissues (Figure 3.1). Others are membrane proteins that act as receptors whose main function is to bind a signaling molecule and induce a biochemical response in the cell. Many receptors have a binding site exposed on the cell surface and an effector domain within the cell, which may have enzymatic activity or may undergo a conformational change detected by other proteins within the cell. Antibodies are protein components of the adaptive immune system whose main function is to bind antigens, or foreign substances in the body, and target them for destruction. Antibodies can be secreted into the extracellular environment or anchored in the membranes of specialized B cells known as plasma cells. Whereas enzymes are limited in their binding affinity for their substrates by the necessity of conducting their reaction, antibodies have no such constraint. An antibody’s binding affinity to its target is extraordinarily high.
Concepts in EMF Biointeraction
Published in Jitendra Behari, Radio Frequency and Microwave Effects on Biological Tissues, 2019
Signal transduction could be of two types: extracellular or intracellular. The former of the two is an example common to the endocrine, immune, and nervous system of mammals. Cells produce mediators (e.g., ligands and hormones) that can be detected by other cells via specific receptors located at the periphery of the cell on the plasma membrane and which induces responses in these cells. The signal can be transmitted inside the cell via a change in conformation of the receptor. This transformation may initiate various intracellular pathways via secondary messengers. Here either the ligand penetrates into the cell to bind to a cytoplasmic receptor, which will then generally act at the nuclear level as a transcription factor, or it binds to the extracellular part of a transmembrane receptor, thus modifying its conformation including the intracellular part of the receptor will have an increased enzymatic activity or bind to other proteins (e.g., kinases or G proteins). These reactions induce intracellular signaling such as protein phosphorylation cascades, which trigger specific cellular responses of the cell: Signal transduction has three stages: communication, transduction, and signaling. RF exposures affect calcium ion concentrations, intracellular gap junctions, and the clustering of receptors at the cell surface.
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
Drugs generally do not create a new effect, but rather, activate or inhibit a specific receptor-related activity. Receptors are sites to which specific ligands bind, thereby altering the cell's biochemical activity. An agonist binds to a receptor and activates a sequence of events that leads to a response. An antagonist binds to a receptor to inhibit the action, without initiating any effect itself. Drugs conferring a short duration of receptor activation generally interact via weaker bonds (ionic, hydrogen or van der Waals), whereas long-duration or irreversible drug–receptor interactions may form stronger bonds, such as covalent bonds. A drug’s ability to affect a specific receptor is related to its affinity and efficacy, which are parameters determined by its chemical structure. Affinity is defined as the probability of a drug occupying its target receptor upon interaction. Efficacy is defined as the extent to which a drug activates a receptor, resulting in a cellular response also known as drug effect (Buxton & Benet, 2013; Page & Maddison, 2008; Raj & Raveendran, 2019).
Liquid crystal and photoluminescent properties of a series of symmetrical 1,2-bis(4-alkoxybenzylidene)hydrazines bearing long-tails of hydrocarbon chain
Published in Liquid Crystals, 2021
Ahmed Jasim M. Al-Karawi, Al-Ameen Bariz OmarAli, Adil A. Awad, Giscard Doungmo, Huayna Terraschke
Synthesis of azine compounds (1,2-disubstituted hydrazines) as rod-like-shaped mesogenic materials with photoluminescence properties is very interesting, since this type of compounds have in origin many other pharmacological and biological activities [23,24], specifically as antitumor, anti-inflammatory, anticonvulsant, antiviral or antidepressant agents. The major role of such compounds as binding molecules of biological receptors makes them suitable candidates for drug development [25]. In this work, 1,2-bis[4-(n-alkoxy)benzylidene]hydrazine (n-alkoxy: O(CH2)nH, n = 11–18 or 20), a symmetrical series of azines, were synthesised in a very simple, convenient and efficient procedure as a part of our continuing work in evaluating hydrophobic 1,2-disubstituted hydrazine compounds (symmetrical and asymmetrical azine-type derivatives) as photoluminescent liquid crystalline materials. The prepared compounds showed liquid crystalline properties as well as photoluminescent properties in the crystalline and liquid crystal states.
Windows of sensitivity to toxic chemicals in the development of reproductive effects: an analysis of ATSDR’s toxicological profile database
Published in International Journal of Environmental Health Research, 2018
Melanie C Buser, Henry G Abadin, John L Irwin, Hana R Pohl
Principal rules of toxicology discussed in our previous papers include: (1) the dose of the chemical, (2) time of exposure (sensitive window), and (3) species differences (Buser and Pohl 2015; Ingber and Pohl 2016). These variables are also critical for determining effects that tested chemicals may have on the development of the reproductive system. In regard to dose, it should be noted that chemicals that exhibit non-monotonic dose response curves (e.g. bisphenol A) could theoretically produce different windows of sensitivity in response to high and very low doses. These responses can result from several molecular mechanisms such as opposing effects induced by multiple receptors differing by their affinity, receptor desensitization, negative feedback with increasing dose, or dose-dependent metabolism modulation (Lagarde et al. 2015). However, such responses were not detected in this review. The understanding of non-monotonic dose responses stems from observing changing direction of effect over the range of doses examined within a study (Vandenberg et al. 2012). While it is possible that non-monotonic responses could potentially result in different effects following exposure at different time periods, this is not something that has been extensively studied and it is beyond the scope of the present review.