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Advances in Physiology Education Jun 2017Since the discovery of the composition and structure of the mammalian cell membrane, biologists have had a clearer understanding of how substances enter and exit the...
Since the discovery of the composition and structure of the mammalian cell membrane, biologists have had a clearer understanding of how substances enter and exit the cell's interior. The selectively permeable nature of the cell membrane allows the movement of some solutes and prevents the movement of others. This has important consequences for cell volume and the integrity of the cell and, as a result, is of utmost clinical importance, for example in the administration of isotonic intravenous infusions. The concepts of osmolarity and tonicity are often confused by students as impermeant isosmotic solutes such as NaCl are also isotonic; however, isosmotic solutes such as urea are actually hypotonic due to the permeant nature of the membrane. By placing red blood cells in solutions of differing osmolarities and tonicities, this experiment demonstrates the effects of osmosis and the resultant changes in cell volume. Using hemoglobin standard solutions, where known concentrations of hemoglobin are produced, the proportion of hemolysis and the effect of this on resultant hematocrit can be estimated. No change in cell volume occurs in isotonic NaCl, and, by placing blood cells in hypotonic NaCl, incomplete hemolysis occurs. By changing the bathing solution to either distilled water or isosmotic urea, complete hemolysis occurs due to their hypotonic effects. With the use of animal blood in this practical, students gain useful experience in handling tissue fluids and calculating dilutions and can appreciate the science behind clinical scenarios.
Topics: Animals; Erythrocytes; Hemolysis; Osmosis; Physiology; Sodium Chloride; Students; Urea
PubMed: 28526694
DOI: 10.1152/advan.00083.2016 -
Advances in Physiology Education Dec 2018Understanding osmolarity and tonicity is one of the more challenging endeavors undertaken by students of the natural sciences. We asked students who completed a course...
Understanding osmolarity and tonicity is one of the more challenging endeavors undertaken by students of the natural sciences. We asked students who completed a course in animal physiology to submit an essay explaining what they found most perplexing about this subject, and what in-class activities proved most useful to them. Students had difficulty distinguishing osmolarity from tonicity and determining tonicity based on the solution's composition. The most useful activities were questions requiring simultaneous consideration of both osmolarity and tonicity. Problems that require calculating osmotic concentration and the volumes of body fluid compartments after administration or loss of various solutions emphasize the significance of osmolarity and tonicity in the context of systemic homeostasis and clinical medicine. We hope that our approach to teaching osmolarity and tonicity will prove useful to physiology lecturers who are looking for new ways of introducing this complicated topic to their health professions students.
Topics: Animals; Cell Size; Humans; Learning; Osmolar Concentration; Osmosis; Physiology; Students, Health Occupations; Teaching
PubMed: 30303411
DOI: 10.1152/advan.00094.2018 -
Nature Cell Biology Sep 2020Ferroptosis is a regulated form of necrotic cell death that is caused by the accumulation of oxidized phospholipids, leading to membrane damage and cell lysis. Although...
Ferroptosis is a regulated form of necrotic cell death that is caused by the accumulation of oxidized phospholipids, leading to membrane damage and cell lysis. Although other types of necrotic death such as pyroptosis and necroptosis are mediated by active mechanisms of execution, ferroptosis is thought to result from the accumulation of unrepaired cell damage. Previous studies have suggested that ferroptosis has the ability to spread through cell populations in a wave-like manner, resulting in a distinct spatiotemporal pattern of cell death. Here we investigate the mechanism of ferroptosis execution and discover that ferroptotic cell rupture is mediated by plasma membrane pores, similarly to cell lysis in pyroptosis and necroptosis. We further find that intercellular propagation of death occurs following treatment with some ferroptosis-inducing agents, including erastin and C' dot nanoparticles, but not upon direct inhibition of the ferroptosis-inhibiting enzyme glutathione peroxidase 4 (GPX4). Propagation of a ferroptosis-inducing signal occurs upstream of cell rupture and involves the spreading of a cell swelling effect through cell populations in a lipid peroxide- and iron-dependent manner.
Topics: Cell Death; Cell Line, Tumor; Ferroptosis; HeLa Cells; Humans; Iron; MCF-7 Cells; Necrosis; Osmosis; Phospholipid Hydroperoxide Glutathione Peroxidase; U937 Cells
PubMed: 32868903
DOI: 10.1038/s41556-020-0565-1 -
Bacteriological Reviews Sep 1957
Topics: Bacteria; Enzymes; Membrane Transport Proteins; Osmosis; Permeability
PubMed: 13471457
DOI: 10.1128/br.21.3.169-194.1957 -
Ugeskrift For Laeger Dec 2019
Topics: Humans; Osmosis; Syndrome
PubMed: 31928622
DOI: No ID Found -
Peritoneal Dialysis International :... 2013
Topics: Aquaporin 1; Biological Transport; Humans; Osmosis; Peritoneal Dialysis; Water
PubMed: 24335118
DOI: 10.3747/pdi.2013.00237 -
Physiological Research Jul 2017The maintenance of plasma sodium concentration within a narrow limit is crucial to life. When it differs from normal physiological patterns, several mechanisms are... (Review)
Review
The maintenance of plasma sodium concentration within a narrow limit is crucial to life. When it differs from normal physiological patterns, several mechanisms are activated in order to restore body fluid homeostasis. Such mechanisms may be vegetative and/or behavioral, and several regions of the central nervous system (CNS) are involved in their triggering. Some of these are responsible for sensory pathways that perceive a disturbance of the body fluid homeostasis and transmit information to other regions. These regions, in turn, initiate adequate adjustments in order to restore homeostasis. The main cardiovascular and autonomic responses to a change in plasma sodium concentration are: i) changes in arterial blood pressure and heart rate; ii) changes in sympathetic activity to the renal system in order to ensure adequate renal sodium excretion/absorption, and iii) the secretion of compounds involved in sodium ion homeostasis (ANP, Ang-II, and ADH, for example). Due to their cardiovascular effects, hypertonic saline solutions have been used to promote resuscitation in hemorrhagic patients, thereby increasing survival rates following trauma. In the present review, we expose and discuss the role of several CNS regions involved in body fluid homeostasis and the effects of acute and chronic hyperosmotic challenges.
Topics: Animals; Blood Pressure; Body Fluids; Central Nervous System; Heart Rate; Homeostasis; Humans; Kidney; Nerve Net; Osmosis; Saline Solution, Hypertonic; Shock, Hemorrhagic
PubMed: 28248529
DOI: 10.33549/physiolres.933373 -
Cells & Development Dec 2021Lumen formation plays an essential role in the morphogenesis of tissues during development. Here we review the physical principles that play a role in the growth and... (Review)
Review
Lumen formation plays an essential role in the morphogenesis of tissues during development. Here we review the physical principles that play a role in the growth and coarsening of lumens. Solute pumping by the cell, hydraulic flows driven by differences of osmotic and hydrostatic pressures, balance of forces between extracellular fluids and cell-generated cytoskeletal forces, and electro-osmotic effects have been implicated in determining the dynamics and steady-state of lumens. We use the framework of linear irreversible thermodynamics to discuss the relevant force, time and length scales involved in these processes. We focus on order of magnitude estimates of physical parameters controlling lumen formation and coarsening.
Topics: Cytoskeleton; Extracellular Fluid; Morphogenesis; Osmosis; Physics
PubMed: 34339904
DOI: 10.1016/j.cdev.2021.203724 -
Biomechanics and Modeling in... Apr 2021We propose a continuum finite strain theory for the interplay between the bioelectricity and the poromechanics of a cell cluster. Specifically, we refer to a cluster of...
We propose a continuum finite strain theory for the interplay between the bioelectricity and the poromechanics of a cell cluster. Specifically, we refer to a cluster of closely packed cells, whose mechanics is governed by a polymer network of cytoskeletal filaments joined by anchoring junctions, modeled through compressible hyperelasticity. The cluster is saturated with a solution of water and ions. We account for water and ion transport in the intercellular spaces, between cells through gap junctions, and across cell membranes through aquaporins and ion channels. Water fluxes result from the contributions due to osmosis, electro-osmosis, and water pressure, while ion fluxes encompass electro-diffusive and convective terms. We consider both the cases of permeable and impermeable cluster boundary, the latter simulating the presence of sealing tight junctions. We solve the coupled governing equations for a one-dimensional axisymmetric benchmark through finite elements, thus determining the spatiotemporal evolution of the intracellular and extracellular ion concentrations, setting the membrane potential, and water concentrations, establishing the cluster deformation. When suitably complemented with genetic, biochemical, and growth dynamics, we expect this model to become a useful instrument for investigating specific aspects of developmental mechanobioelectricity.
Topics: Biomechanical Phenomena; Cells; Electrophysiological Phenomena; Gap Junctions; Intracellular Space; Models, Biological; Osmosis; Thermodynamics; Tight Junctions
PubMed: 33145723
DOI: 10.1007/s10237-020-01399-0 -
Water Research Apr 2020This study investigated the performance of two full-scale ion exchange (IX) systems, one point-of-entry (POE) reverse osmosis (RO) system and nine point-of-use (POU) RO...
This study investigated the performance of two full-scale ion exchange (IX) systems, one point-of-entry (POE) reverse osmosis (RO) system and nine point-of-use (POU) RO units for simultaneous removal of arsenic and several co-occurring contaminants from drinking water. The study was performed as part of the U.S. Environmental Protection Agency's Arsenic Treatment Demonstration Program. The IX systems, with strong base anionic (SBA) resins, effectively removed arsenic (As), nitrate (NO) and uranium (U) to below respective maximum contaminant levels and vanadium (V) and molybdenum (Mo) to below 2 μg/L. The useful run length, as determined by either 10-mg/L (as N) nitrate or 10-μg/L arsenic breakthrough, was approximately 400 bed volumes (BV) initially. However, it was decreased over time, e.g., by 15% in 13 months at one site and 33% in 7 months at another site, apparently caused by resin fouling due to the presence of 2-mg/L natural organic matter (NOM) in source waters. The use of dual resins ‒ an acrylic SBA resin underlain by a polystyrene SBA resin ‒ effectively removed NOM and allowed the system to perform at its baseline level through the 13-month study. Arsenic and nitrate peaking occurred when the resins were not regenerated timely. The removal of contaminants appeared to follow a selectivity sequence: U, Mo > V > SO > HAsO > NO > HCO. RO effectively removed arsenic, nitrate, antimony, uranium and vanadium, mostly with a >99% rejection rate. The POE RO coupled with dual plumbing (only treating a fraction of water for potable use) and POU RO in individual homes could be used as low-cost alternatives to traditional RO treatment.
Topics: Arsenic; Drinking Water; Ion Exchange; Osmosis; Water Pollutants, Chemical; Water Purification
PubMed: 31958595
DOI: 10.1016/j.watres.2019.115455