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Kidney Response To Acidosis

Renin-angiotensin-aldosterone

Renin-angiotensin-aldosterone

Molecules that are dissolved in water may dissociate into charged ions. An acid is a substance that increases the number of H+ ions in a solution. A base is a substance that decreases the number of H+ ions in a solution. The concentration of H+ ions in a solution can be measured and is called the pH of the solution. The pH of a solution can be measured using a scale that ranges from 0 to 14. A solution of pH = 7 is neutral, a solution of pH lower than 7 is acidic, and a solution of pH greater than 7 is basic (alkaline). The number of H+ ions increases as the pH number decreases (and vice versa). The difference between two successive numbers on the pH scale represents a ten-fold difference in the H+ ion concentration because the scale is a logarithmic scale (log of base 10). For example, a solution with a pH of 2 has 10 times more H+ ions as a solution with a pH of 3. A solution with a pH of 2 has 100 times more H+ ions as a solution with a pH of 4. Metabolism and Clinical Conditions Can Change the pH of Body Fluids Such as Blood Blood pH is normally 7.35-7.45. Sometimes, however, blood pH decreases to below 7.35 and becomes acidic. This occurs normally from the byproducts released during metabolism such as carbon dioxide (CO2), sulfuric acid, lactic acid, etc. The blood may also become acidic in patients suffering from emphysema, asthma, bronchitis, pneumonia, and pulmonary edema. In these cases, carbon dioxide increases in the blood since it cannot effectively diffuse out of the lungs. This results in a condition known as acidosis. Acidosis means that the hydrogen ions are increased ( pH is decreased). How the Body Returns the pH of the Blood Back to Normal: The body uses 3 different mechanisms to return the pH back to normal when the blood becomes acidic or alkaline: Continue reading >>

Metabolic Acidosis

Metabolic Acidosis

Metabolic acidosis is a condition that occurs when the body produces excessive quantities of acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low (less than 7.35) due to increased production of hydrogen ions by the body or the inability of the body to form bicarbonate (HCO3−) in the kidney. Its causes are diverse, and its consequences can be serious, including coma and death. Together with respiratory acidosis, it is one of the two general causes of acidemia. Terminology : Acidosis refers to a process that causes a low pH in blood and tissues. Acidemia refers specifically to a low pH in the blood. In most cases, acidosis occurs first for reasons explained below. Free hydrogen ions then diffuse into the blood, lowering the pH. Arterial blood gas analysis detects acidemia (pH lower than 7.35). When acidemia is present, acidosis is presumed. Signs and symptoms[edit] Symptoms are not specific, and diagnosis can be difficult unless the patient presents with clear indications for arterial blood gas sampling. Symptoms may include chest pain, palpitations, headache, altered mental status such as severe anxiety due to hypoxia, decreased visual acuity, nausea, vomiting, abdominal pain, altered appetite and weight gain, muscle weakness, bone pain, and joint pain. Those in metabolic acidosis may exhibit deep, rapid breathing called Kussmaul respirations which is classically associated with diabetic ketoacidosis. Rapid deep breaths increase the amount of carbon dioxide exhaled, thus lowering the serum carbon dioxide levels, resulting in some degree of compensation. Overcompensation via respiratory alkalosis to form an alkalemia does not occur. Extreme acidemia leads to neurological and cardia Continue reading >>

Disorders Of Acid-base Balance: New Perspectives

Disorders Of Acid-base Balance: New Perspectives

Disorders of Acid-Base Balance: New Perspectives 75 Francis Street, MRB-4, Boston, MA 02115 (USA) Background: Disorders of acid-base involve the complex interplay of many organ systems including brain, lungs, kidney, and liver. Compensations for acid-base disturbances within the brain are more complete, while limitations of compensations are more apparent for most systemic disorders. However, some of the limitations on compensations are necessary to survival, in that preservation of oxygenation, energy balance, cognition, electrolyte, and fluid balance are connected mechanistically. Summary: This review aims to give new and comprehensive perspective on understanding acid-base balance and identifying associated disorders. All metabolic acid-base disorders can be approached in the context of the relative losses or gains of electrolytes or a change in the anion gap in body fluids. Acid-base and electrolyte balance are connected not only at the cellular level but also in daily clinical practice. Urine chemistry is essential to understanding electrolyte excretion and renal compensations. Key Messages: Many constructs are helpful to understand acid-base, but these models are not mutually exclusive. Electroneutrality and the close interconnection between electrolyte and acid-base balance are important concepts to apply in acid-base diagnoses. All models have complexity and shortcuts that can help in practice. There is no reason to dismiss any of the present constructs, and there is benefit in a combined approach. The hydrogen ion concentration of body fluids is maintained within a narrow range for purposes of regulating normal metabolic and enzymatic processes and critical functions such as fertilization, growth, cell volume regulation, and protein synthesis. Since the [H+] i Continue reading >>

Final Flashcards | Quizlet

Final Flashcards | Quizlet

Which of the following substances is not normally found in filtrate? Hint 1. Think about how a coffee filter works. C. nitrogenous waste particles, such as urea Blood cells and large particles, such as proteins, are not allowed to filter through a healthy __________. What is the primary driving force (pressure) that produces glomerular filtration? Hint 1. What was the primary driving force for filtration from a capillary? B. hydrostatic pressure of blood (blood pressure) B. hydrostatic pressure of blood (blood pressure) Which of the following would only be found in the glomerular filtrate if the glomerular membrane were damaged? Hint 1. If a filter is damaged, it would let particles through that it normally would not filter. If the osmotic pressure in the glomerular capillaries increased from 28 mm Hg to 35 mm Hg, would net filtration increase or decrease? Hint 1. Proteins in the plasma would increase the osmotic pressure of the blood. True/False: osmotic pressure opposes filtration, increasing osmotic pressure would decrease net filtration. Calculate the net filtration pressure if capillary hydrostatic pressure is 60 mm Hg, capillary osmotic pressure is 25 mm Hg, and capsular hydrostatic pressure is 10 mm Hg. Hint 1. Remember that hydrostatic pressure pushes water away and osmotic pressure draws water in. The ________ is a capillary plexus that parallels the nephron loop (loop of Henle). The step in kidney function where fluid is forced out of the blood is __________. Typical renal blood flow is about ________ ml/min under resting conditions. Sympathetic stimulation of the kidney can do all of the following, except B. produce powerful vasoconstriction of the afferent arterioles. E. increase the glomerular filtration rate. E. increase the glomerular filtration rate. Th Continue reading >>

Renal Response To Acid-base Imbalance

Renal Response To Acid-base Imbalance

The kidneys respond to acid-base disturbances by modulating both renal acid excretion and renal bicarbonate excretion. These processes are coordinated to return the extracellular fluid pH, and thus blood pH, to normal following a derangement. Below we discuss the coordinated renal response to such acid-base disturbances. Acidosis refers to an excess extracellular fluid H+ concentration and thus abnormally low pH. The overall renal response to acidosis involves the net urinary excretion of hydrogen, resorption of nearly all filtered bicarbonate, and the generation of novel bicarbonate which is added to the extracellular fluid. Processes of renal acid excretion result in both direct secretion of free hydrogen ions, thus acidifying the urine, as well as secretion of hydrogen in the form of ammonium. These mechanisms are molecularly coupled to the generation of fresh bicarbonate, which is added to the extracellular fluid. Additionally, as discussed in renal bicarbonate excretion, nearly all filtered bicarbonate is resorbed and thus its urinary loss is minimized. Together, these processes slowly reduce ECF hydrogen ions and increase ECF bicarbonate concentrations, thus gradually raising blood pH to its normal value. Alkalosis refers to a insufficient extracellular fluid H+ concentration and thus abnormally high pH. The overall response to alkalosis involves reduced urinary secretion of hydrogen and the urinary excretion of filtered bicarbonate. Renal acid excretion is minimized in the context of alkalosis, thus preventing further increases in the ECF pH. Instead, renal bicarbonate excretion is increased, resulting in loss of bicarbonate from the extracellular fluid, and an alkalinization of the urine. Together these processes reduce ECF bicarbonate concentrations and in doin Continue reading >>

Acid-base Balance

Acid-base Balance

pH, Buffers, Acids, and Bases Acids dissociate into H+ and lower pH, while bases dissociate into OH− and raise pH; buffers can absorb these excess ions to maintain pH. Learning Objectives Explain the composition of buffer solutions and how they maintain a steady pH Key Takeaways A basic solution will have a pH above 7.0, while an acidic solution will have a pH below 7.0. Buffers are solutions that contain a weak acid and its a conjugate base; as such, they can absorb excess H+ ions or OH– ions, thereby maintaining an overall steady pH in the solution. pH is equal to the negative logarithm of the concentration of H+ ions in solution: pH = −log[H+]. Key Terms alkaline: having a pH greater than 7; basic acidic: having a pH less than 7 buffer: a solution composed of a weak acid and its conjugate base that can be used to stabilize the pH of a solution Self-Ionization of Water Hydrogen ions are spontaneously generated in pure water by the dissociation (ionization) of a small percentage of water molecules into equal numbers of hydrogen (H+) ions and hydroxide (OH−) ions. The hydroxide ions remain in solution because of their hydrogen bonds with other water molecules; the hydrogen ions, consisting of naked protons, are immediately attracted to un-ionized water molecules and form hydronium ions (H30+). By convention, scientists refer to hydrogen ions and their concentration as if they were free in this state in liquid water. The concentration of hydrogen ions dissociating from pure water is 1 × 10−7 moles H+ ions per liter of water. The pH is calculated as the negative of the base 10 logarithm of this concentration: pH = −log[H+] The negative log of 1 × 10−7 is equal to 7.0, which is also known as neutral pH. Human cells and blood each maintain near-neutral pH. p Continue reading >>

Renal Regulation Of Metabolic Acidosis And Alkalosis

Renal Regulation Of Metabolic Acidosis And Alkalosis

1. 06/21/14 1 Normal Acid-Base Balance • Normal pH 7.35-7.45 • Narrow normal range • Compatible with life 6.8 - 8.0 ___/______/___/______/___ 6.8 7.35 7.45 8.0 Acid Alkaline 2. 06/21/14 2 PH Scale 3. 06/21/14 3 Acid & Base • Acid: • An acid is "when hydrogen ions accumulate in a solution" • It becomes more acidic • [H+] increases = more acidity • CO2 is an example of an acid. Base: A base is chemical that will remove hydrogen ions from the solution Bicarbonate is an example of a base. 4. 06/21/14 4 Acid and Base Containing Food: • To maintain health, the diet should consist of 60% alkaline forming foods and 40% acid forming foods. To restore health, the diet should consist of 80% alkaline forming foods and 20% acid forming foods. • Generally, alkaline forming foods include: most fruits, green vegetables, peas, beans, lentils, spices, herbs,seasonings,seeds and nuts. • Generally, acid forming foods include: meat, fish, poultry, eggs, grains, and legumes. 5. 06/21/14 5 Citric Acid And Lactic Acid Although both citric acid and lactic acid are acids BUT Citric acid leads to Alkalosis while Lactic acid to Acidosis due to metabolism 6. 06/21/14 6 Acidoses & Alkalosis • An abnormality in one or more of the pH control mechanisms can cause one of two major disturbances in Acid-BaseAcid-Base balance – AcidosisAcidosis – AlkalosisAlkalosis 7. 06/21/14 7 Acidosis • Acidosis is excessive blood acidity caused by an overabundance of acid in the blood or a loss of bicarbonate from the blood (metabolic acidosis), or by a buildup of carbon dioxide in the blood that results from poor lung function or slow breathing (respiratory acidosis). • Blood acidity increases when people ingest substances that contain or produce acid or when the lungs do not expel enou Continue reading >>

Natalies Casebook| Tag

Natalies Casebook| Tag

Most of the acid in the body is buffered by the carbon dioxide/bicarbonate (CO2/HC03-) system: The partial pressure of CO2 (P a CO 2 ) is regulated by the lungs and changes in alveolar ventilation, whereas the plasma concentration of HC03- is regulated by the kidneys. Indeed, the pH of blood is simply a constant plus the ratio of HC03- to P a CO 2 . More simply, we can think of pH varying in proportion to this ratio, or more simply what the kidneys are doing relative to the lungs. What matters is the ratio, not the absolute values of HC03- and P a CO 2 . The body may compensate for a disturbance in one with an alteration in the other. So, you may encounter a patient with very odd HC03-, but an equally odd P a CO 2 and a relatively normal pH. What is going on here is compensation there is an unresolved acid-base irregularity but the body is managing to compensate. When we are thinking about the overall role of the kidney in acid-base regulation, we can simplify the work of all the component parts into a simple model that ignores the complex anatomy and different functional components of this organ. Such a model is not helpful in understanding diseases of the kidney, but is satisfactory for our needs here. The way the kidney regulates H+ ions is by regulating whether HC03- is added to blood or allowed to be excreted into the urine. So: 1. In acidaemia, urine is acid, not because H+ has been secreted into the urine, but because filtered HC03- has been removed. 2. In alkalaemia, urine is basic, because filtered HC03- has been allowed to stay in the urine, not because H+ has been removed. Neither of these is truly an active response to the change in pH of blood, but rather what happens to the existing mechanics of the regulation of HC03- when the concentration of plasma H+ Continue reading >>

How The Kidneys Regulate Acid Base Balance

How The Kidneys Regulate Acid Base Balance

Acid-Base Balance Everyday processes like walking, the digestion of food, and the overall metabolism in your body produce a lot of acid as a byproduct. Because of this, you'd be a giant walking lemon if it wasn't for your kidneys. What I mean is, like a lemon, you'd be filled with acid if your kidneys weren't there to help you regulate your body's pH through something we call acid-base balance. This is a process whereby receptors are able to determine the pH of your body and blood and do something about it if it's too acidic or too basic. If an imbalance in the pH is detected by your lungs, buffers, or kidneys, your body springs into action to take care of the problem. In this lesson, we'll focus in on how the kidneys help to control the acid-base balance in your body. Protons and Buffers Whereas the buffers in your body and your lungs are involved in the rapid adjustment of your blood's pH, the kidneys adjust the pH more slowly. Under normal conditions, the kidney's main role in acid-base balance is through the excretion of acid in the form of hydrogen (H+) ions. The kidneys secrete excess hydrogen ions primarily in the proximal tubule. The interesting thing to note is that while the proximal tubule secretes a lot of acid, the tubular fluid's pH remains virtually unchanged. This is because buffers filtered by the glomerulus, including phosphate and bicarbonate, help to minimize the acidity of the tubular fluid. In fact, what's really cool is that the pH of the tubular fluid, by the time it reaches the collecting duct, is about 7.4, which is exactly the pH of normal blood. The Collecting Duct However, by the time urine is excreted out of the body, it can be acidic, basic, or neutral. This is because the end-all, be-all gatekeeper in determining the final pH of urine is Continue reading >>

Proximal Tubule Function And Response To Acidosis

Proximal Tubule Function And Response To Acidosis

Proximal Tubule Function and Response to Acidosis *Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado; and Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical Center, Dallas, Texas Dr. Norman P. Curthoys, Department of Biochemistry and Molecular Biology, Colorado State University, Campus Delivery 1870, Fort Collins, CO 80523-1870; or Dr. Orson W. Moe, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390. Email: Norman.Curthoys{at}Colostate.edu or orson.moe{at}utsouthwestern.edu The human kidneys produce approximately 160170 L of ultrafiltrate per day. The proximal tubule contributes to fluid, electrolyte, and nutrient homeostasis by reabsorbing approximately 60%70% of the water and NaCl, a greater proportion of the NaHCO3, and nearly all of the nutrients in the ultrafiltrate. The proximal tubule is also the site of active solute secretion, hormone production, and many of the metabolic functions of the kidney. This review discusses the transport of NaCl, NaHCO3, glucose, amino acids, and two clinically important anions, citrate and phosphate. NaCl and the accompanying water are reabsorbed in an isotonic fashion. The energy that drives this process is generated largely by the basolateral Na+/K+-ATPase, which creates an inward negative membrane potential and Na+-gradient. Various Na+-dependent countertransporters and cotransporters use the energy of this gradient to promote the uptake of HCO3 and various solutes, respectively. A Na+-dependent cotransporter mediates the movement of HCO3 across the basolateral membrane, whereas various Na+-independent passive transporters accomplish the export of various other solut Continue reading >>

4.5 Respiratory Acidosis - Compensation

4.5 Respiratory Acidosis - Compensation

Acid-Base Physiology 4.5.1 The compensatory response is a rise in the bicarbonate level This rise has an immediate component (due to a resetting of the physicochemical equilibrium point) which raises the bicarbonate slightly. Next is a slower component where a further rise in plasma bicarbonate due to enhanced renal retention of bicarbonate. The additional effect on plasma bicarbonate of the renal retention is what converts an "acute" respiratory acidsosis into a "chronic" respiratory acidosis. As can be seen by inspection of the Henderson-Hasselbalch equation (below), an increased [HCO3-] will counteract the effect (on the pH) of an increased pCO2 because it returns the value of the [HCO3]/0.03 pCO2 ratio towards normal. pH = pKa + log([HCO3]/0.03 pCO2) 4.5.2 Buffering in Acute Respiratory Acidosis The compensatory response to an acute respiratory acidosis is limited to buffering. By the law of mass action, the increased arterial pCO2 causes a shift to the right in the following reaction: CO2 + H2O <-> H2CO3 <-> H+ + HCO3- In the blood, this reaction occurs rapidly inside red blood cells because of the presence of carbonic anhydrase. The hydrogen ion produced is buffered by intracellular proteins and by phosphates. Consequently, in the red cell, the buffering is mostly by haemoglobin. This buffering by removal of hydrogen ion, pulls the reaction to the right resulting in an increased bicarbonate production. The bicarbonate exchanges for chloride ion across the erythrocyte membrane and the plasma bicarbonate level rises. In an acute acidosis, there is insufficient time for the kidneys to respond to the increased arterial pCO2 so this is the only cause of the increased plasma bicarbonate in this early phase. The increase in bicarbonate only partially returns the extracel Continue reading >>

Response To Disturbances

Response To Disturbances

The body tries to minimize pH changes and responds to acid-base disturbances with body buffers, compensatory responses by the lungs and kidney (to metabolic and respiratory disturbances, respectively) and by the kidney correcting metabolic disturbances. Body buffers: There are intracellular and extracellular buffers for primary respiratory and metabolic acid-base disturbances. Intracellular buffers include hemoglobin in erythrocytes and phosphates in all cells. Extracellular buffers are carbonate (HCO3–) and non-carbonate (e.g. protein, bone) buffers. These immediately buffer the rise or fall in H+. Compensation: This involves responses by the respiratory tract and kidney to primary metabolic and respiratory acid-base disturbances, respectively. Compensation opposes the primary disturbance, although the laboratory changes in the compensatory response parallel those in the primary response. This concept is illustrated in the summary below. Respiratory compensation for a primary metabolic disturbance: Alterations in alveolar ventilation occurs in response to primary metabolic acid-base disturbances. This begins within minutes to hours of an acute primary metabolic disturbance. Note that complete compensation via this mechanism may take up to 24 hours. Renal compensation for a primary respiratory disturbance: Here, the kidney alters excretion of acid (which influences bases as well) in response to primary respiratory disturbances. This begins within hours of an acute respiratory disturbance, but take several days (3-5 days) to take full effect. Correction of acid-base changes: Correction of a primary respiratory acid-base abnormality usually requires medical or surgical intervention of the primary problem causing the acid-base disturbance, e.g. surgical relief of a colla Continue reading >>

Renal Physiology Acid-base Balance

Renal Physiology Acid-base Balance

Sort Your patient's blood pH is too low (acidosis), caused by metabolic acidosis. After examining the patient, you find that the urine bicarbonate levels are too low (H+ is being reabsorbed) and blood carbon dioxide levels are too high (too much blood acid); What does this mean? Based on the patient's pCO2 levels are they compensating or not? This means that the original problem of a low bicarbonate level needs to be compensated for by the lungs, which need to hyperventilate, expelling more CO2 (an acid). Since this patient's pCO2 levels are also high (not expelling enough acid), they are NOT compensating. Patient's blood pH is too high (alkalosis). This can be caused by either respiratory or metabolic alkalosis. Let's say it is metabolic alkalosis. What do you need to check to see if patient is compensating? If bicarbonate levels are high (too much base) and blood CO2 levels are high (too much acid), what do the lungs need to do to compensate? What does the patient's elevated Pco2 levels tell you? Patients partial pressure of Carbon dioxide and bicarbonate Take shallower breaths to prevent loss of acid Patient is compensating Patient's blood pH is too high (alkalosis). This can be caused by either respiratory or metabolic alkalosis. Let's say it is metabolic alkalosis. What do you need to check to see if patient is compensating? If bicarbonate levels are high (too much base) and blood CO2 levels are low (too little acid), what do the lungs need to do to compensate? Since the patient's pCO2 level is low, this tells you what? Patients pCO2 and bicarbonate Take shallower breaths to prevent loss of acid Not compensating Continue reading >>

Renal Response To Metabolic Acidosis: Role Of Mrna Stabilization

Renal Response To Metabolic Acidosis: Role Of Mrna Stabilization

Renal response to metabolic acidosis: Role of mRNA stabilization Hend Ibrahim , Ph.D., Yeon J. Lee , Ph.D., and Norman P. Curthoys , Ph.D. Department of Biochemistry and Molecular Biology Colorado State University Fort Collins, CO 80523-1870 Direct Correspondence to: Dr. Norman P. Curthoys, Department of Biochemistry and Molecular Biology, Campus Delivery 1870, Colorado State University, Fort Collins, CO 80523-1870. Phone: (970) 491-3123, FAX: (970) 491-0494, [email protected] The publisher's final edited version of this article is available at Kidney Int See other articles in PMC that cite the published article. The renal response to metabolic acidosis is mediated, in part, by increased expression of the genes encoding key enzymes of glutamine catabolism and various ion transporters that contribute to the increased synthesis and excretion of ammonium ions and the net production and release of bicarbonate ions. The resulting adaptations facilitate the excretion of acid and partially restore systemic acid-base balance. Much of this response may be mediated by selective stabilization of the mRNAs that encode the responsive proteins. For example, the glutaminase mRNA contains a direct repeat of 8-nt AU-sequences that function as a pH-response element (pH-RE). This element is both necessary and sufficient to impart a pH-responsive stabilization to chimeric mRNAs. The pH-RE also binds multiple RNA binding proteins, including -crystallin, AUF1 and HuR. The onset of acidosis initiates an ER-stress response that leads to the formation of cytoplasmic stress granules. -crystallin is transiently recruited to the stress granules and concurrently, HuR is translocated from the nucleus to the cytoplasm. Based upon the cumulative data, a mechanism for the stabilization of Continue reading >>

Acid-base Balance Flashcards | Quizlet

Acid-base Balance Flashcards | Quizlet

Acid-base balance is an important determinant of protein ______ & ______ structure, function (When pH goes out of normal range these proteins are denatured ) All enzymatic functions are sensitive to this ion Relationship between respiratory system & acid-base balance -Determines affinity of Hb for O2, in alveolar capillaries - release in tissue capillaries -Respiratory rate directly affected by [H+] in resp center of brainstem + carotid body for rapid regulation of pH and pCO2 -Variations in alveolar ventilation volume cause acidosis and alkalosis Relationship b/w digestive system & acid-base balance -Acid in stomach hydrolyzes protein molecules -Digestive enzymes in stomach dependent on low pH to function (trypsin) -Alkaline secretions of biliary and pancreatic ducts neutralize gastric secretions -Enzymes in duodenum/sb act in a neutral pH environment (amylase lipase) Relationship b/w excretory system & acid-base balance -Acid , -Phos, -SO4 excreted from body by kidneys -Kidneys play role in long term (>24o) pH control -Rate of acid excretion dependent on degree of renal function and hormonal factors -At 37oC [H+] and [OH-] are both 100 nanomoles/L or 0.0000001 moles/L 7.35 to 7.45 (slightly alkaline not neutral) -Inversely related (negative in logarithm equation important) [H+] in plasma higher than normal (already slightly alkaline) quantity of Acid or Alkali required to return the plasma in-vitro to a normal pH (7.4) under standard conditions difference between commonly measured anions and cations i.e unmeasured anions such as lactate, oxalic acid increased in anion gap metabolic acidosis Role of intracellular and extracellular buffer, respiratory, and renal mechanisms in maintaining normal blood pH -Because the lungs can eliminate this it's called respiratory acid Continue reading >>

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