Biomedical subjects
A G Wasserstein
Publications and source records attributed to A G Wasserstein.
Nephrolithiasis: acute management and prevention.
The primary care physician has a responsibility not only to recognize and treat acute stone passage but to ensure that the patient with recurrent stones has metabolic evaluation and appropriate preventive care. Renal colic is typically severe, radiates to the groin, is associated with hematuria, and may cause ileus. About 90% of stones that cause renal colic pass spontaneously. The patient with acute renal colic should be treated with fluids and analgesics and should strain the urine to recover stone for analysis. Highgrade obstruction or failure of oral analgesics to relieve pain may require hospitalization; a urinary tract infection in the setting of an obstruction is a urologic emergency requiring immediate drainage, usually with a ureteral stent. Several approaches are available when stones do not pass spontaneously, including extracorporeal shock wave lithotripsy, percutaneous lithotripsy, and ureteroscopic laser lithotripsy. Calcium stone disease has a lifetime prevalence of 10% in men and causes significant morbidity. Renal failure is unusual. Stone types include calcium oxalate, uric acid, struvite, and cystine. Stone analysis is particularly important when a noncalcareous constituent is identified. The majority of patients with nephrolithiasis will have recurrence, so prevention is a high priority. High fluid intake is a mainstay of prevention. Metabolic evaluation will indicate other appropriate preventive measures, which may include dietary salt and protein restriction, and use of thiazide diuretics, neutral phosphate, potassium citrate, allopurinol, and magnesium salts. Dietary calcium restriction may worsen oxaluria and negative calcium balance (osteoporosis).
Membranous glomerulonephritis.
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Death and the internal milieu: Claude Bernard and the origins of experimental medicine.
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Changing patterns of medical practice: protein restriction for chronic renal failure.
The use of dietary protein restriction for renal failure has fluctuated during the past 125 years. These fluctuations reflect not only the state of medical knowledge but also social, economic, and cultural factors. Factors inhibiting use of dietary treatment have been its status as an aspect of hygiene rather than as active therapy; the opinions of dominant practitioners and scientists around midcentury, including a presumption that renal adaptation to a high-protein diet must be appropriate; fear of malnutrition and a cultural belief in the virtue of dietary protein; unwillingness by physicians and patients to restrict consumption or lifestyle; and professional identification with the technologies of dialysis and renal transplantation. Factors promoting dietary treatment have been rediscovery of previous work on protein-induced renal injury; a sense that homeostatic compensations could have adverse consequences; federal incentives to curb consumption of scarce resources such as renal dialysis; and the integration of research on, and therapeutic use of diet into scientific medicine. A large ongoing study of dietary protein restriction to limit renal injury will add to our knowledge of this treatment; its application will surely be informed by social and cultural considerations.
Toward a romantic science: the work of Oliver Sacks.
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Controlled study of renal osteodystrophy in patients undergoing dialysis. Improved response to continuous ambulatory peritoneal dialysis compared with hemodialysis.
To assess the effect of different dialysis modalities on renal osteodystrophy, a controlled study was performed in six patients undergoing continuous ambulatory peritoneal dialysis and six hemodialysis-treated patients. All patients were enrolled at the initiation of dialysis, and age, sex, cause of renal failure, prior treatment of renal osteodystrophy, and baseline serum and bone histologic variables were similar in the two groups. After initial blood samples and bone biopsy specimens (with double-tetracycline labels) were obtained, renal osteodystrophy in both groups received comparable treatment with aluminum hydroxide to maintain serum phosphorus levels between 3.5 and 5.5 mg/dl, and with calcium carbonate and calcitriol to maintain total serum calcium levels between 10 and 11 mg/dl. Blood and bone samples were obtained again after nine months. All patients were asymptomatic at the beginning and end of the study. Phosphorus values were well controlled, and total calcium increased similarly in both groups. Although ionized calcium levels increased in both groups, the final level was higher in hemodialysis-treated patients than in patients undergoing continuous ambulatory peritoneal dialysis (2.82 +/- 0.07 meq/liter and 2.5 +/- 0.05 meq/liter, respectively; p = 0.005). Amino-terminal parathyroid hormone levels normalized in both groups, and histologic improvement of osteitis fibrosa occurred in a similar proportion of patients in both groups; however, quantitative improvement was greater in the hemodialysis-treated patients. Osteomalacia, assessed qualitatively and by dynamic histomorphometric measurements, was ameliorated to a much greater degree in patients undergoing continuous ambulatory peritoneal dialysis compared with hemodialysis-treated patients. Bone aluminum staining was absent in all biopsy specimens. Overall, bone histologic findings improved to a greater degree in patients undergoing continuous ambulatory peritoneal dialysis. When patients undergoing continuous ambulatory peritoneal dialysis or hemodialysis and receiving similar treatment for renal osteodystrophy were compared, patients treated with continuous ambulatory peritoneal dialysis appeared to have a greater improvement in their metabolic bone disease.
Case-control study of risk factors for idiopathic calcium nephrolithiasis.
We compared epidemiological risk factors and urine excretion of calcium, phosphate, uric acid, urea nitrogen, sodium, potassium, and fluid volume in recurrent idiopathic calcium stone-formers and in a control group of age- and sex-matched normal volunteers. Stone-formers were less likely than normal subjects to have followed a low-calorie diet, but body weight did not differ between the two groups. Daily urine calcium excretion was a graded risk factor for stone formation throughout its range. Daily urine urea nitrogen and potassium excretion were lower in stone-formers than in controls, but excretion of uric acid, sodium, phosphate, and creatinine did not differ. However, there were positive associations between urine calcium excretion and the urine excretion of sodium, urea nitrogen, uric acid, phosphate, and creatinine in stone-formers; and these associations were significantly stronger than in normal subjects. We conclude that urine calcium excretion is a major risk factor for idiopathic calcium stone formation, but cannot confirm such a role for urine uric acid excretion. Total dietary protein intake may be lower in stone-formers than in controls. However, stone-formers may be more sensitive than normal subjects to the calciuric effects of protein and sodium. A strong association of urine calcium excretion with urine phosphate excretion in stone-formers is probably independent of dietary protein intake.
Sleep apnea in hemodialysis patients: the lack of testosterone effect on its pathogenesis.
After the discovery of sleep apnea in 2 patients receiving chronic maintenance hemodialysis, we decided to survey all 29 male patients undergoing outpatient dialysis for symptoms suggestive of sleep apnea. 12 of 29 (41%) had positive clinical histories. 8 of these patients consented to undergo all-night polysomnography. 6 were found to have sleep apnea which was primarily obstructive in type. Recent information has implicated testosterone administration in the development of obstructive sleep apnea. Therefore, polysomnography was performed in 5 of the patients both on and off weekly testosterone injections which they were receiving to stimulate erythropoiesis. There was no change in sleep complaints or a decrease in the number of apneas and hypopneas off therapy. Sleep apnea should be considered in symptomatic male dialysis patients. Its causation is presently unknown but it does not appear to be solely related to the administration of testosterone.
Potassium secretion in the rabbit proximal straight tubule.
The renal handling of potassium is generally thought to involve proximal reabsorption and distal secretion. To evaluate transport in the pars recta, we perfused S2 and S3 segments from superficial and juxtamedullary proximal straight tubules isolated from the rabbit kidney. The data indicate net potassium secretion in the isolated perfused perfused proximal straight tubule (PST). K+ secretion (JK, pmol X mm-1 X min-1) was -2.51 +/- 0.53 in superficial PST S2 segments, -2.80 +/- 1.05 in superficial PST S3 segments, and -1.36 +/- 0.84 in juxtamedullary PST. Secretion was inhibited by 10(-5) M ouabain in the bath in superficial S2 and S3 segments. When a solution resembling late proximal tubular fluid was perfused in superficial PST, JK fell from -3.86 +/- 1.77 to -0.45 +/- 0.63 pmol X mm-1 X min-1. When luminal flow rate was varied in the physiologic range in individual superficial S2 and S3 segments, JK varied directly; K+ secretion increased by -0.5 pmol X mm-1 X min-1 per 1 nl X min-1 increment in luminal flow, while collected K+ concentration did not vary significantly. When a favorable bath-to-lumen K+ gradient (10 vs. 5 mM) was imposed, K+ secretion was markedly enhanced; when an equal but oppositely directed gradient was imposed, net K+ reabsorption was observed. These data are consistent with a gradient-limited process. In midcortical tubule segments (S2 and S3), 10(-3) M amiloride in perfusate inhibited net K+ secretion from -2.77 +/- 0.52 to -0.18 +/- 1.08 pmol X mm-1 X min-1 and fluid absorption from 0.42 +/- 0.10 to 0.18 +/- 0.05 nl X mm-1 X min-1. Net K+ secretion in S2 and S3 segments of PST may contribute to previously reported K+ secretion prior to the bend of Henle's loop. The magnitude of this process in vivo is uncertain in the absence of measurements of interstitial K+ concentration in the milieu of the PST.