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Pharmaceutical industry By the 1890s, the profound effect of adrenal extracts on many different tissue types had been discovered, setting off a search both for the mechanism of chemical signalling and efforts to exploit these observations for the development of new drugs. The blood pressure raising and vasoconstrictive... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Following the work of Henry Dale and George Barger at Burroughs-Wellcome, academic chemist Gordon Alles synthesized amphetamine and tested it in asthma patients in 1929. The drug proved to have only modest anti-asthma effects but produced sensations of exhilaration and palpitations. Amphetamine ... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Phenobarbital was among the most widely used drugs for the treatment of epilepsy through the 1970s, and as of 2014, remains on the World Health Organizations list of essential medications. The 1950s and 1960s saw increased awareness of the addictive properties and abuse potential of barbiturates... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Walden of Eli Lilly and Company found that careful adjustment of the pH of the extract allowed a relatively pure grade of insulin to be produced. Under pressure from Toronto University and a potential patent challenge by academic scientists who had independently developed a similar purification ... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Arsphenamine proved to be the first effective treatment for syphilis, a disease which prior to that time was incurable and led inexorably to severe skin ulceration, neurological damage, and death. Ehrlich's approach of systematically varying the chemical structure of synthetic compounds and meas... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry and British government-led consortium of pharmaceutical companies during the Second World War. Early progress toward the development of vaccines occurred throughout this period, primarily in the form of academic and government-funded basic research directed toward the identification of the patho... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry To the extent that such laws did exist, enforcement was lax. In the United States, increased regulation of vaccines and other biological drugs was spurred by tetanus outbreaks and deaths caused by the distribution of contaminated smallpox vaccine and diphtheria antitoxin. The Biologics Control A... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry In response to this episode, the U.S. Congress passed the Federal Food, Drug, and Cosmetic Act of 1938, which for the first time required pre-market demonstration of safety before a drug could be sold, and explicitly prohibited false therapeutic claims. The aftermath of World War II saw an explo... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry The report concluded that "it appears that the use of antibiotics, early diagnosis, and other factors have limited the epidemic spread and thus the number of these diseases which have occurred". The study further examined mortality rates for eight common diseases for which antibiotics offered ef... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry It was later determined that SV40 was present as a contaminant in polio vaccine lots that had been administered to 90% of the children in the United States. The contamination appears to have originated both in the original cell stock and in monkey tissue used for production. In 2004 the United S... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Early developments in the field of treating hypertension included quaternary ammonium ion sympathetic nervous system blocking agents, but these compounds were never widely used due to their severe side effects, because the long-term health consequences of high blood pressure had not yet been est... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry In the ensuring years other classes of antihypertensive drug were developed and found wide acceptance in combination therapy, including loop diuretics (Lasix/furosemide, Hoechst Pharmaceuticals, 1963), beta blockers (ICI Pharmaceuticals, 1964) ACE inhibitors, and angiotensin receptor blockers. A... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry The availability of a convenient form of temporary contraceptive led to dramatic changes in social mores including expanding the range of lifestyle options available to women, reducing the reliance of women on men for contraceptive practice, encouraging the delay of marriage, and increasing pre-... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Without approval from the FDA, the firm distributed Kevadon to over 1,000 physicians there under the guise of investigational use. Over 20,000 Americans received thalidomide in this "study," including 624 pregnant patients, and about 17 known newborns suffered the effects of the drug. The thalid... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Mevastatin was never marketed, because of its adverse effects of tumors, muscle deterioration, and sometimes death in laboratory dogs. P. Roy Vagelos, chief scientist and later CEO of Merck & Co, was interested, and made several trips to Japan starting in 1975. By 1978, Merck had isolated lovast... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry A great deal of early-stage drug discovery has traditionally been carried out by universities and research institutions. Drug development refers to activities undertaken after a compound is identified as a potential drug in order to establish its suitability as a medication. Objectives of drug d... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry In 2010 18 NMEs (New Molecular Entities) were approved and three biologics by the FDA, or 21 in total, which is down from 26 in 2009 and 24 in 2008. On the other hand, there were only 18 approvals in total in 2007 and 22 back in 2006. Since 2001, the Center for Drug Evaluation and Research has a... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry According to Forbes, by 2010 development costs were between $4 billion to $11 billion per drug. Some of these estimates also take into account the opportunity cost of investing capital many years before revenues are realized (see Time-value of money). Because of the very long time needed for dis... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry US congress signed into law a bill which requires phase II and phase III clinical trials to be registered by the sponsor on the clinicaltrials.gov website run by the NIH. Drug researchers not directly employed by pharmaceutical companies often look to companies for grants, and companies often lo... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry In contrast to this viewpoint, an article and associated editorial in the New England Journal of Medicine in May 2015 emphasized the importance of pharmaceutical industry-physician interactions for the development of novel treatments, and argued that moral outrage over industry malfeasance had u... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry On 26 February 2020, the US Health and Human Services Secretary (former pharmaceutical CEO Alex Azar, known for the doubling of the price of insulin while he was at Eli Lilly) testified before the House Energy and Commerce Committee. At this meeting Azar repeatedly refused to say that any corona... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry " The 6 March Coronavirus Preparedness and Response Supplemental Appropriations Act, 2020 originally allowed the US government to bring in compulsory licensing where prices are excessive; after lobbying, this was removed, and a provision was added to prevent the US government from taking any act... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Remdesivir is a candidate for treating COVID-19; at the time the status was granted, fewer than 200,000 Americans had COVID-19, but numbers were climbing rapidly as the COVID-19 pandemic reached the US, and crossing the threshold soon was considered inevitable. Remdesivir was developed by Gilead... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry TAG also started started the "Time for $5" campaign. Analogous tests for hepatitis C virus (another RNA virus) cost from 50 US cents (for five-minute antibody tests) to US$5 (for more complex genome tests similar to Cepheid's). Widespread testing with these cheap tests has been critical to elimi... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Postmarketing surveillance ensures that after marketing the safety of a drug is monitored closely. In certain instances, its indication may need to be limited to particular patient groups, and in others the substance is withdrawn from the market completely. The FDA provides information about app... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry A product must pass the threshold for cost-effectiveness if it is to be approved. Treatments must represent 'value for money' and a net benefit to society. There are special rules for certain rare diseases ("orphan diseases") in several major drug regulatory territories. For example, diseases in... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry The best-selling drug ever, Lipitor, averaged $13 billion annually and netted $141 billion total over its lifetime before Pfizer's patent expired in November 2011. IMS Health publishes an analysis of trends expected in the pharmaceutical industry in 2007, including increasing profits in most sec... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry , the value of prescriptions increased over the period of 1995 to 2005 by 3.4 billion annually, a 61 percent increase. Retail sales of prescription drugs jumped 250 percent from $72 billion to $250 billion, while the average price of prescriptions more than doubled from $30 to $68. Advertising i... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry There has been increasing controversy surrounding pharmaceutical marketing and influence. There have been accusations and findings of influence on doctors and other health professionals through drug reps including the constant provision of marketing 'gifts' and biased information to health profe... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry Meta-analyses have shown that psychiatric studies sponsored by pharmaceutical companies are several times more likely to report positive results, and if a drug company employee is involved the effect is even larger. Influence has also extended to the training of doctors and nurses in medical sch... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry In the first quarter of 2017, the health products and pharmaceutical industry spent $78 million on lobbying members of the United States Congress. Ben Goldacre has argued that regulators – such as the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK, or the Food and Drug Admi... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry It affects individuals and public and private insurers. There are several different schemes used to defraud the health care system which are particular to the pharmaceutical industry. These include: Good Manufacturing Practice (GMP) Violations, Off Label Marketing, Best Price Fraud, CME Fraud, M... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry On 2 July 2012, GlaxoSmithKline pleaded guilty to criminal charges and agreed to a $3 billion settlement of the largest health-care fraud case in the U.S. and the largest payment by a drug company. The settlement is related to the company's illegal promotion of prescription drugs, its failure to... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry In 2001, the WTO adopted the Doha Declaration, which indicates that the TRIPS agreement should be read with the goals of public health in mind, and allows some methods for circumventing pharmaceutical monopolies: via compulsory licensing or parallel imports, even before patent expiration. In Mar... | https://en.wikipedia.org/wiki?curid=560876 |
Pharmaceutical industry In 2016, GlaxoSmithKline (the worlds 6th largest Pharmaceutical) announced that it would be dropping its patents in poor countries so as to allow independent companies to make and sell versions of its drugs in those areas, thereby widening the public access to them. GlaxoSmithKline published a l... | https://en.wikipedia.org/wiki?curid=560876 |
Cyanohydrin A cyanohydrin is a functional group found in organic compounds in which a cyano and a hydroxy group are attached to the same carbon atom. The general formula is RC(OH)CN, where R is H, alkyl, or aryl. Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids. Cyanohydrins c... | https://en.wikipedia.org/wiki?curid=561018 |
Cyanohydrin Glycolonitrile, also called hydroxyacetonitrile or formaldehyde cyanohydrin, is the organic compound with the formula HOCHCN. It is the simplest cyanohydrin, being derived from formaldehyde. | https://en.wikipedia.org/wiki?curid=561018 |
Brillouin zone In mathematics and solid state physics, the first is a uniquely defined primitive cell in reciprocal space. In the same way the Bravais lattice is divided up into Wigner–Seitz cells in the real lattice, the reciprocal lattice is broken up into Brillouin zones. The boundaries of this cell are given by pla... | https://en.wikipedia.org/wiki?curid=562067 |
Brillouin zone A related concept is that of the irreducible Brillouin zone, which is the first reduced by all of the symmetries in the point group of the lattice (point group of the crystal). The concept of a was developed by Léon Brillouin (1889–1969), a French physicist. Several points of high symmetry are of special... | https://en.wikipedia.org/wiki?curid=562067 |
Basal metabolic rate (BMR) is the rate of energy expenditure per unit time by endothermic animals at rest. It is reported in energy units per unit time ranging from watt (joule/second) to ml O/min or joule per hour per kg body mass J/(h·kg). Proper measurement requires a strict set of criteria be met. These criteria in... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate BMR typically declines by 1–2% per decade after age 20, mostly due to loss of fat-free mass, although the variability between individuals is high. The body's generation of heat is known as thermogenesis and it can be measured to determine the amount of energy expended. BMR generally decreases with ... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate Studies of energy metabolism using both methods provide convincing evidence for the validity of the respiratory quotient (RQ), which measures the inherent composition and utilization of carbohydrates, fats and proteins as they are converted to energy substrate units that can be used by the body as ... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate "islandica") increases its BMR by about 40% before migrating northward. This is because of the energetic demand of long-distance flights. The increase is likely primarily due to increased mass in organs related to flight. The end destination of migrants affects their BMR: yellow-rumped warblers mig... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate This group was measured via simultaneously direct and indirect calorimetry and had standardized daily meals and sedentary schedule in order to prevent the increase from being manipulated by change in food intake or activity level. A 2011 study conducted by the Mandya Institute of Medical Sciences f... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate The chief functions of the hypothalamus are: All of these functions taken together form a survival mechanism that causes us to sustain the body processes that BMR measures. Several equations to predict the number of calories required by humans have been published from the early 20th–21st centuries.... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate The Cunningham formula is commonly cited to predict RMR instead of BMR; however, the formulas provided by Katch-McArdle and Cunningham are the same. where ℓ is the lean body mass ("LBM" in kg) where f is the body fat percentage. According to this formula, if the woman in the example has a body fat ... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate Additionally, this study reports a case where two individuals with the same lean body mass of 43 kg had BMRs of 1075 kcal/day (4.5 MJ/day) and 1790 kcal/day (7.5 MJ/day). This difference of 715 kcal/day (67%) is equivalent to one of the individuals completing a 10 kilometer run every day. However, ... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate The breakdown of proteins into amino acids is an example of catabolism, while the formation of proteins from amino acids is an anabolic process. Exergonic reactions are energy-releasing reactions and are generally catabolic. Endergonic reactions require energy and include anabolic reactions and the... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate Consequently, during the complete oxidation of a glucose molecule, six molecules of carbon dioxide and six molecules of water are produced and six molecules of oxygen are consumed. The overall equation for this reaction is: Because the gas exchange in this reaction is equal, the respiratory quotien... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate Unlike fat the body has no storage deposits of protein. All of it is contained in the body as important parts of tissues, blood hormones, and enzymes. The structural components of the body that contain these amino acids are continually undergoing a process of breakdown and replacement. The respirat... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate ) At rest approximately 70% of the ATP produced is derived from fats and 30% from carbohydrates. Following the onset of activity, as the intensity of the exercise increases, there is a shift in substrate preference from fats to carbohydrates. During high intensity aerobic exercise, almost 100% of t... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate Resistance training if time is available is also helpful in post-exercise metabolism, but it is an adjunctive factor because the body needs to heal sufficiently between resistance training episodes, whereas with aerobic training, the body can accept this every day. RMR and BMR are measurements of d... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate Additionally, the life span of houseflies can be extended by preventing physical activity. This theory has been bolstered by several new studies linking lower basal metabolic rate to increased life expectancy, across the animal kingdom—including humans. Calorie restriction and reduced thyroid hormo... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate When ME is 100%, MR = W^3/4; this is popularly known as quarter power scaling, a version of allometric scaling that is premised upon unrealistic estimates of biological efficiency. The equation reveals that as ME drops below 20%, for W < one gram, MR/MPLS increases so dramatically as to endow W wit... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate Weight training can have a longer impact on metabolism than aerobic training, but there are no known mathematical formulas that can exactly predict the length and duration of a raised metabolism from trophic changes with anabolic neuromuscular training. A decrease in food intake will typically lowe... | https://en.wikipedia.org/wiki?curid=562788 |
Basal metabolic rate The anaerobic threshold is defined as the energy utilization level of heart rate exertion that occurs without oxygen during a standardized test with a specific protocol for accuracy of measurement, such as the Bruce Treadmill protocol (see metabolic equivalent of task). With four to six weeks of ta... | https://en.wikipedia.org/wiki?curid=562788 |
Paracrine signaling is a form of cell signaling or cell-to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse over a relatively short distance (local action), as opposed to cell signaling b... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling In order for paracrine factors to successfully induce a response in the receiving cell, that cell must have the appropriate receptors available on the cell membrane to receive the signals, also known as being competent. Additionally, the responding cell must also have the ability to be mechanistical... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling Phenotype and survival of mice after knockout of some FGFR genes: through fibroblast growth factors and its respective receptors utilizes the receptor tyrosine pathway. This signaling pathway has been highly studied, using "Drosophila" eyes and human cancers. Binding of FGF to FGFR phosphorylates th... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling Activation of Ras has the potential to initiate three signaling pathways downstream of Ras: Ras→Raf→MAP kinase pathway, PI3 kinase pathway, and Ral pathway. Each pathway leads to the activation of transcription factors which enter the nucleus to alter gene expression. of growth factors between nearb... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling In addition to RTK pathway, fibroblast growth factors can also activate the Jak-STAT signaling cascade. Instead of carrying covalently associated tyrosine kinase domains, Jak-STAT receptors form noncovalent complexes with tyrosine kinases of the Jak (Janus kinase) class. These receptors bind are for... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling Thus, the inability of the rib cage to expand prevents the newborn's breathing. Research on paracrine signaling through the Jak-STAT pathway revealed its potential in activating invasive behavior of ovarian epithelial cells. This epithelial to mesenchymal transition is highly evident in metastasis. ... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling Members of the Hedgehog protein family act by binding to a transmembrane "Patched" receptor, which is bound to the "Smoothened" protein, by which the Hedgehog signal can be transduced. In the absence of Hedgehog, the Patched receptor inhibits Smoothened action. Inhibition of Smoothened causes the Cu... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling In addition, therapy-induced Hedgehog pathway activation has been shown to be necessary for progression of Prostate Cancer tumors after androgen deprivation therapy. This connection between the Hedgehog signaling pathway and human cancers may provide for the possible of therapeutic intervention as t... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling In its active state the Dishevelled protein inhibits the activity of the glycogen synthase kinase 3 (GSK3) enzyme. Normally active GSK3 prevents the dissociation of β-catenin to the APC protein, which results in β-catenin degradation. Thus inhibited GSK3, allows β-catenin to dissociate from APC, acc... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling The noncanonical Wnt/Ca pathway regulates intracellular calcium levels. Again Wnt binds and activates to Frizzled. In this case however activated Frizzled causes a coupled G-protein to activate a phospholipase (PLC), which interacts with and splits PIP into DAG and IP. IP can then bind to a receptor... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling Many developmental processes are under its control including gastrulation, axis symmetry of the body, organ morphogenesis, and tissue homeostasis in adults. All TGF-β ligands bind to either Type I or Type II receptors, to create heterotetramic complexes. The TGF-β pathway regulates many cellular pro... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling Specific TGF-β ligands will result in the activation of either the SMAD2/3 or the SMAD1/5 R-SMADs. For instance, when activin, Nodal, or TGF-β ligand binds to the receptors, the phosphorylated receptor complex can activate SMAD2 and SMAD3 through phosphorylation. However, when a BMP ligand binds to ... | https://en.wikipedia.org/wiki?curid=563093 |
Paracrine signaling Members of the BMP family were originally found to induce bone formation, as their name suggests. However, BMPs are very multifunctional and can also regulate apoptosis, cell migration, cell division, and differentiation. They also specify the anterior/posterior axis, induce growth, and regulate hom... | https://en.wikipedia.org/wiki?curid=563093 |
Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. For the exterior of the cell, typical values of membrane potential, normally given in units of millivolts and denoted as mV, range from –40 mV to –80 ... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Signals are generated by opening or closing of ion channels at one point in the membrane, producing a local change in the membrane potential. This change in the electric field can be quickly affected by either adjacent or more distant ion channels in the membrane. Those ion channels can then open or ... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential They include numerous types of ion channels, some of which are chemically gated and some of which are voltage-gated. Because voltage-gated ion channels are controlled by the membrane potential, while the membrane potential itself is influenced by these same ion channels, feedback loops that allow for... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential It is conventional in electronics to assign a voltage of zero to some arbitrarily chosen element of the circuit, and then assign voltages for other elements measured relative to that zero point. There is no significance in which element is chosen as the zero point—the function of a circuit depends on... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Note that the definition allows for an arbitrary constant of integration—this is why absolute values of voltage are not meaningful. In general, electric fields can be treated as conservative only if magnetic fields do not significantly influence them, but this condition usually applies well to biolog... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential This mixing occurs because of the difference in their concentrations. The region with high concentration will diffuse out toward the region with low concentration. To extend the example, let solution A have 30 sodium ions and 30 chloride ions. Also, let solution B have only 20 sodium ions and 20 chlo... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Therefore, positive sodium ions will be less likely to travel to the now-more-positive B solution and remain in the now-more-negative A solution. The point at which the forces of the electric fields completely counteract the force due to diffusion is called the equilibrium potential. At this point, t... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential The conductance of a pure lipid bilayer is so low, on the other hand, that in biological situations it is always dominated by the conductance of alternative pathways provided by embedded molecules. Thus, the capacitance of the membrane is more or less fixed, but the resistance is highly variable. The... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential In most cases, an ion channel is permeable only to specific types of ions (for example, sodium and potassium but not chloride or calcium), and sometimes the permeability varies depending on the direction of ion movement. Ion pumps, also known as ion transporters or carrier proteins, actively transpor... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential If the numbers of each type of ion were equal, the sodium–potassium pump would be electrically neutral, but, because of the three-for-two exchange, it gives a net movement of one positive charge from intracellular to extracellular for each cycle, thereby contributing to a positive voltage difference.... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential In particular, ion pumps play no significant role in the repolarization of the membrane after an action potential. Another functionally important ion pump is the sodium-calcium exchanger. This pump operates in a conceptually similar way to the sodium-potassium pump, except that in each cycle it excha... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Channel pores can be either open or closed for ion passage, although a number of channels demonstrate various sub-conductance levels. When a channel is open, ions permeate through the channel pore down the transmembrane concentration gradient for that particular ion. Rate of ionic flow through the ch... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Other ion channels open and close with mechanical forces. Still other ion channels—such as those of sensory neurons—open and close in response to other stimuli, such as light, temperature or pressure. Leakage channels are the simplest type of ion channel, in that their permeability is more or less co... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Neurotransmitter receptors are activated by ligands that appear in the extracellular area, but there are other types of ligand-gated channels that are controlled by interactions on the intracellular side. Voltage-gated ion channels, also known as "voltage dependent ion channels", are channels whose p... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential The reversal potential (or "equilibrium potential") of an ion is the value of transmembrane voltage at which diffusive and electrical forces counterbalance, so that there is no net ion flow across the membrane. This means that the transmembrane voltage exactly opposes the force of diffusion of the io... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential In order for a neuron to eventually adopt its full adult function, its potential must be tightly regulated during development. As an organism progresses through development the resting membrane potential becomes more negative. Glial cells are also differentiating and proliferating as development prog... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Calcium ion is also the most important second messenger in excitable cell signaling. Activation of synaptic receptors initiates long-lasting changes in neuronal excitability. Thyroid, adrenal and other hormones also regulate cell excitability. Many cell types are considered to have an excitable membr... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential The capacitance is determined by the properties of the lipid bilayer, and is taken to be fixed. Each of the four parallel pathways comes from one of the principal ions, sodium, potassium, chloride, and calcium. The voltage of each ionic pathway is determined by the concentrations of the ion on each s... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential In most cases, changes in the conductance of ion channels occur on a faster time scale, so an RC circuit is not a good approximation; however, the differential equation used to model a membrane patch is commonly a modified version of the RC circuit equation. When the membrane potential of a cell goes... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential The three ions that appear in this equation are potassium (K), sodium (Na), and chloride (Cl). Calcium is omitted, but can be added to deal with situations in which it plays a significant role. Being an anion, the chloride terms are treated differently from the cation terms; the intracellular concent... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential The resting potential in excitable cells (capable of producing action potentials) is usually near -60 mV—more depolarized voltages would lead to spontaneous generation of action potentials. Immature or undifferentiated cells show highly variable values of resting voltage, usually significantly more p... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential As an apparent result, potassium permeability becomes similar to that for sodium ions, which places resting potential in-between the reversal potentials for sodium and potassium as discussed above. The reduced leakage currents also mean there is little need for active pumping in order to compensate, ... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential Thus, opening Na channels shifts the membrane potential toward the Na reversal potential, which is usually around +100 mV. Likewise, opening K channels shifts the membrane potential toward about –90 mV, and opening Cl channels shifts it toward about –70 mV (resting potential of most membranes). Thus,... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential A current with a reversal potential below threshold, such as a typical K current, is considered inhibitory. A current with a reversal potential above the resting potential, but below threshold, will not by itself elicit action potentials, but will produce subthreshold membrane potential oscillations.... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential In this case, potassium carries about 20 times more current than sodium, and thus has 20 times more influence over "E" than does sodium. However, consider another case—the peak of the action potential. Here, permeability to Na is high and K permeability is relatively low. Thus, the membrane moves to ... | https://en.wikipedia.org/wiki?curid=563161 |
Membrane potential These changes in the membrane potential enable communication with other cells (as with action potentials) or initiate changes inside the cell, which happens in an egg when it is fertilized by a sperm. In neuronal cells, an action potential begins with a rush of sodium ions into the cell through sodiu... | https://en.wikipedia.org/wiki?curid=563161 |
Crystalloluminescence is the effect of luminescence produced during crystallization. The phenomena was first reported in the 1800s from the rapid crystallization of potassium sulfate from an aqueous solution. | https://en.wikipedia.org/wiki?curid=563728 |
Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in microelectronics and related struc... | https://en.wikipedia.org/wiki?curid=563847 |
Electromigration Since reliability is critically important for space travel, military purposes, anti-lock braking systems, medical equipment like Automated External Defibrillators and is even important for personal computers or home entertainment systems, the reliability of chips (ICs) is a major focus of research effo... | https://en.wikipedia.org/wiki?curid=563847 |
Electromigration Currents are also reduced due to lower supply voltages and shrinking gate capacitances. However, as current reduction is constrained by increasing frequencies, the more marked decrease in cross-sectional areas (compared to current reduction) will give rise to increased current densities in ICs going fo... | https://en.wikipedia.org/wiki?curid=563847 |
Electromigration In the late 1980s, one line of Western Digital's desktop drives suffered widespread, predictable failure 12–18 months after field usage. Using forensic analysis of the returned bad units, engineers identified improper design-rules in a third-party supplier's IC controller. By replacing the bad componen... | https://en.wikipedia.org/wiki?curid=563847 |
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