The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
Mitchell L Halperin - One of the best experts on this subject based on the ideXlab platform.
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dogmas and controversies in the handling of nitrogenous wastes Excretion of nitrogenous wastes in human subjects
The Journal of Experimental Biology, 2004Co-Authors: Kamel S. Kamel, Surinder Cheemadhadli, Mohammad A Shafiee, Mitchell L HalperinAbstract:Two major nitrogenous waste products, urea and ammonium (NH4+), are produced in humans when proteins are oxidized, and in this manuscript their Excretions are examined from two perspectives. First, the specific physiology of each nitrogenous waste is reviewed and the current dogmas summarized. Second, their Excretions are considered in the context of integrative physiology, i.e. the need to ensure that the urine composition is appropriate to minimize the risk of kidney stone formation. After the latter analysis, weak links in our understanding of the overall physiology become apparent and a conundrum is defined. The conundrum for the Excretion of urea focuses on the fact that urea is not an effective osmole in the medullary-collecting duct when vasopressin acts. As a result, it appears that urinary urea cannot prevent a large decline in the urine flow rate and thereby minimize the risk of forming kidney stones in electrolyte-poor urine. The conundrum for the Excretion of NH4+ is: high rates of NH4+ Excretion require a low urine pH, yet a pH ∼6.0 must be maintained in order to reduce the risk of precipitating uric acid in the urine. Possible ways of resolving these conundrums require novel physiological interpretations.
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studies on the pathophysiology of the low urine ph in patients with uric acid stones
Kidney International, 2002Co-Authors: Kamel S. Kamel, Surinder Cheemadhadli, Mitchell L HalperinAbstract:Studies on the pathophysiology of the low urine pH in patients with uric acid stones. Background A very low urine pH is the major risk factor for uric acid stone formation. Methods A subgroup of patients with a history of uric acid stones and a persistently low urine pH ( 4 + ) and sulfate (SO 4 2- ) Excretions, patients were divided into two groups. Results The first group ( N = 2) excreted 173 and 139% more NH 4 + than SO 4 2- . Their daily urinary unmeasured anion Excretion was higher than their calculated net diet alkali input (38 and 61 vs. 24 and 49 mEq, respectively). In the second group ( N = 12), NH 4 + Excretion was 69 ± 5% that of SO 4 2- . In 2 of 12, decreased renal ammoniagenesis was suspected due to a plasma potassium of 5.3mmol/L and/or a lower GFR (65 and 59 L/day); these patients had an extremely low citrate Excretion (3 and 1 mEq/day). In contrast, citrate Excretion was not low in the remaining 10 patients (10.4 ± 1.3 mEq/day). Conclusions Patients in group 1 needed a higher NH 4 + Excretion possibly because of a H + load from excessive renal Excretion of organic anions. We speculate that an alkaline proximal tubular cell pH could be the basis for the low NH 4 + and high citrate Excretions in 10 of 12 patients in group 2. Dietary factors and/or a molecular lesion may contribute to their pathophysiology.
Michael J. Dillon - One of the best experts on this subject based on the ideXlab platform.
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Tubular proteinuria in reflux nephropathy: post ureteric re-implantation
Pediatric Nephrology, 1996Co-Authors: Chulananda D. A. Goonasekera, Vanita Shah, Michael J. DillonAbstract:We studied urine protein Excretion in 55 adults with reflux nephropathy (median age 26.9 years) who had had normal blood pressure, renal function and ureteric reimplantation in childhood. Urine retinol binding protein (RBP), N -acetyl-β- d -glucosaminidase (NAG), albumin, bacteriuria, systolic blood pressure, glomerular filtration rate (GFR), peripheral plasma renin activity (PRA) and the degree of renal scarring were measured in each subject; 20 had bilateral and 35 unilateral renal scarring; 5 were hypertensive and none were in renal failure. Urinary NAG and RBP Excretions were significantly greater in the study group than in 34 healthy controls (median age 29.7 years). Within the study group, NAG Excretion significantly correlated with PRA ( P =0.02). RBP Excretion correlated with PRA, systolic blood pressure and the laterality (bilateral vs. unilateral) of scarring ( P
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tubular proteinuria in reflux nephropathy post ureteric re implantation
Pediatric Nephrology, 1996Co-Authors: Chulananda D. A. Goonasekera, Vanita Shah, Michael J. DillonAbstract:We studied urine protein Excretion in 55 adults with reflux nephropathy (median age 26.9 years) who had had normal blood pressure, renal function and ureteric reimplantation in childhood. Urine retinol binding protein (RBP), N-acetyl-β-d-glucosaminidase (NAG), albumin, bacteriuria, systolic blood pressure, glomerular filtration rate (GFR), peripheral plasma renin activity (PRA) and the degree of renal scarring were measured in each subject; 20 had bilateral and 35 unilateral renal scarring; 5 were hypertensive and none were in renal failure. Urinary NAG and RBP Excretions were significantly greater in the study group than in 34 healthy controls (median age 29.7 years). Within the study group, NAG Excretion significantly correlated with PRA (P=0.02). RBP Excretion correlated with PRA, systolic blood pressure and the laterality (bilateral vs. unilateral) of scarring (P<0.01). Urinary albumin Excretion correlated with systolic blood pressure (P=0.03). We conclude that increase urinary protein, especially NAG and RBP Excretion, occur late after ureteric re-implantation in reflux nephropathy independent of GFR. Its association with PRA supports the concept of segmental perfusion and filtration as an important mechanism that may explain the above findings.
Martine Duclos - One of the best experts on this subject based on the ideXlab platform.
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training and 24 hr urinary catecholamine Excretion
International Journal of Sports Medicine, 2009Co-Authors: Edith Filaire, M. Rouveix, Martine DuclosAbstract:We examined the effects of 28 weeks of training on 24-hr urinary catecholamine Excretion and mood (evaluated using the Recovery-Stress Questionnaire for Athletes RESTQ-Sport) among seven national young female tennis players. Data were collected after a 1-month rest (September, T (1)), 3 months after T1(T2) and 7 months after T1(T3). Standardized Stress and Standardized Recovery scores and RESTQ-Index were computed. The training load increased by 161 % between T1 and T2 and by 55 % between T2 and T3. The performance (wins/total number of matches) decreased throughout the study. Urinary catecholamine Excretion presented an U-shaped curve with a significant increase in 24-hr urinary catecholamine Excretions, and epinephrine/norepinephrine ratio from T1 to T2 (T1 vs. T2: epinephrine: + 100 %, p < 0.05; norepinephrine: + 30 %, p < 0.05. Then, at T3, urinary catecholamine Excretions and the epinephrine/norepinephrine ratio decreased significantly to values lower than the values observed at T1. A decrease in RESTQ-Index throughout the study was mainly based on a large increase in the Standardized Stress score. Changes in specific stress and recovery scales of the RESTQ-Sport for athletes and changes in catecholamine values indicated a state of heavy training stress and incomplete recovery at the end of the study.
Kamel S. Kamel - One of the best experts on this subject based on the ideXlab platform.
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dogmas and controversies in the handling of nitrogenous wastes Excretion of nitrogenous wastes in human subjects
The Journal of Experimental Biology, 2004Co-Authors: Kamel S. Kamel, Surinder Cheemadhadli, Mohammad A Shafiee, Mitchell L HalperinAbstract:Two major nitrogenous waste products, urea and ammonium (NH4+), are produced in humans when proteins are oxidized, and in this manuscript their Excretions are examined from two perspectives. First, the specific physiology of each nitrogenous waste is reviewed and the current dogmas summarized. Second, their Excretions are considered in the context of integrative physiology, i.e. the need to ensure that the urine composition is appropriate to minimize the risk of kidney stone formation. After the latter analysis, weak links in our understanding of the overall physiology become apparent and a conundrum is defined. The conundrum for the Excretion of urea focuses on the fact that urea is not an effective osmole in the medullary-collecting duct when vasopressin acts. As a result, it appears that urinary urea cannot prevent a large decline in the urine flow rate and thereby minimize the risk of forming kidney stones in electrolyte-poor urine. The conundrum for the Excretion of NH4+ is: high rates of NH4+ Excretion require a low urine pH, yet a pH ∼6.0 must be maintained in order to reduce the risk of precipitating uric acid in the urine. Possible ways of resolving these conundrums require novel physiological interpretations.
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studies on the pathophysiology of the low urine ph in patients with uric acid stones
Kidney International, 2002Co-Authors: Kamel S. Kamel, Surinder Cheemadhadli, Mitchell L HalperinAbstract:Studies on the pathophysiology of the low urine pH in patients with uric acid stones. Background A very low urine pH is the major risk factor for uric acid stone formation. Methods A subgroup of patients with a history of uric acid stones and a persistently low urine pH ( 4 + ) and sulfate (SO 4 2- ) Excretions, patients were divided into two groups. Results The first group ( N = 2) excreted 173 and 139% more NH 4 + than SO 4 2- . Their daily urinary unmeasured anion Excretion was higher than their calculated net diet alkali input (38 and 61 vs. 24 and 49 mEq, respectively). In the second group ( N = 12), NH 4 + Excretion was 69 ± 5% that of SO 4 2- . In 2 of 12, decreased renal ammoniagenesis was suspected due to a plasma potassium of 5.3mmol/L and/or a lower GFR (65 and 59 L/day); these patients had an extremely low citrate Excretion (3 and 1 mEq/day). In contrast, citrate Excretion was not low in the remaining 10 patients (10.4 ± 1.3 mEq/day). Conclusions Patients in group 1 needed a higher NH 4 + Excretion possibly because of a H + load from excessive renal Excretion of organic anions. We speculate that an alkaline proximal tubular cell pH could be the basis for the low NH 4 + and high citrate Excretions in 10 of 12 patients in group 2. Dietary factors and/or a molecular lesion may contribute to their pathophysiology.
Chulananda D. A. Goonasekera - One of the best experts on this subject based on the ideXlab platform.
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Tubular proteinuria in reflux nephropathy: post ureteric re-implantation
Pediatric Nephrology, 1996Co-Authors: Chulananda D. A. Goonasekera, Vanita Shah, Michael J. DillonAbstract:We studied urine protein Excretion in 55 adults with reflux nephropathy (median age 26.9 years) who had had normal blood pressure, renal function and ureteric reimplantation in childhood. Urine retinol binding protein (RBP), N -acetyl-β- d -glucosaminidase (NAG), albumin, bacteriuria, systolic blood pressure, glomerular filtration rate (GFR), peripheral plasma renin activity (PRA) and the degree of renal scarring were measured in each subject; 20 had bilateral and 35 unilateral renal scarring; 5 were hypertensive and none were in renal failure. Urinary NAG and RBP Excretions were significantly greater in the study group than in 34 healthy controls (median age 29.7 years). Within the study group, NAG Excretion significantly correlated with PRA ( P =0.02). RBP Excretion correlated with PRA, systolic blood pressure and the laterality (bilateral vs. unilateral) of scarring ( P
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tubular proteinuria in reflux nephropathy post ureteric re implantation
Pediatric Nephrology, 1996Co-Authors: Chulananda D. A. Goonasekera, Vanita Shah, Michael J. DillonAbstract:We studied urine protein Excretion in 55 adults with reflux nephropathy (median age 26.9 years) who had had normal blood pressure, renal function and ureteric reimplantation in childhood. Urine retinol binding protein (RBP), N-acetyl-β-d-glucosaminidase (NAG), albumin, bacteriuria, systolic blood pressure, glomerular filtration rate (GFR), peripheral plasma renin activity (PRA) and the degree of renal scarring were measured in each subject; 20 had bilateral and 35 unilateral renal scarring; 5 were hypertensive and none were in renal failure. Urinary NAG and RBP Excretions were significantly greater in the study group than in 34 healthy controls (median age 29.7 years). Within the study group, NAG Excretion significantly correlated with PRA (P=0.02). RBP Excretion correlated with PRA, systolic blood pressure and the laterality (bilateral vs. unilateral) of scarring (P<0.01). Urinary albumin Excretion correlated with systolic blood pressure (P=0.03). We conclude that increase urinary protein, especially NAG and RBP Excretion, occur late after ureteric re-implantation in reflux nephropathy independent of GFR. Its association with PRA supports the concept of segmental perfusion and filtration as an important mechanism that may explain the above findings.