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Biomedical subjects

A Besarab

Publications and source records attributed to A Besarab.

At least 73 records · Page 4Linked to original sources
PubMed1981

Diagnostic and prognostic significance of an increase in fractional protein clearance ratio before and during rejection of renal transplant.

We measured prospectively changes in fractional protein clearance ratio (CPr/CCr) in 21 live-related (LR) and 41 cadaver donor (CD) renal transplants before and during onset of first rejections. Fifty-three recipients manifested a rejection within the first post-transplant month. Fractional protein clearance increased in all patients during rejection. An increase in CPr/CCr prior to other evidence of impending rejection, and therefore clinically useful, required at least a 10-day rejection-free interval dated from onset of diuresis (whether diuresis was immediate or delayed by acute tubular necrosis (ATN)). Twenty-three of 25 nonantilymphocyte globulin (ALG)-treated CD transplants manifested clinical and laboratory signs of the first rejection episode prior to the 10th day of diuresis compared with 5 of 21 LR and none of 16 ALG-treated CD transplants. Persistence of elevated CPr/CCr despite treatment forecast graft loss (11 of 13), whereas a decrease in this ratio was associated with ultimate reversal of the rejection process.

Graft Rejection↗
PubMed1981

Effect of albumin and free calcium concentrations on calcium binding in vitro.

In vivo equilibrium dialysis studies were performed to define further the characteristics of calcium binding to bovine albumin. The concentration range for albumin (1 to 9 g/dl) as well as ultrafilterable calcium (0.5 to 2.5 mM) studied encompassed those that might be ordinarily encountered in most clinical situations. Major differences in the regressions of total calcium on ultrafilterable calcium occurred at albumin concentrations of 1, 2, and 9 g/dl but only small differences at albumin concentrations between 3, 5 and 7 g/dl. When albumin concentration was kept constant, the amount of calcium bound to albumin varied directly with ultrafilterable calcium. At any constant ultrafilterable calcium concentration albumin bound calcium varied inversely with the albumin concentrations when albumin was greater than 3 g/dl. Analysis of the data to determine association constants and molar calcium to albumin binding ratios showed that both parameters were dependent on the absolute albumin concentrations. Our results indicate that calcium binding to albumin is a complex process characterised by multiple binding sites whose affinity and binding capacity are variable. These properties suggest that correction of total serum calcium using clinical formulations with fixed calcium to albumin binding ratios may be inappropriate, particularly in hypoalbuminaemic states.

Calcium↗
PubMed1981

Increased absolute calcium binding to albumin in hypoalbuminaemia.

The amount of calcium bound to protein was measured in 30 patients with differing diseases and varying degrees of hypoalbuminaemia. Total serum calcium increased directly with both serum albumin and ultrafilterable calcium concentrations. The estimated amount of calcium bound per gram of albumin varied inversely with the albumin concentration, decreasing from 2.1 to 1.0 mg calcium/g albumin as albumin concentration increased from 1.7 to 3.1 g/dl. Circulating parathyroid hormone (PTH) concentrations varied inversely with measured ultrafilterable calcium concentrations. The frequency of raised PTH concentrations decreased as serum albumin increased. Use of a conventional correction factor for albumin binding (0.88 mg calcium bound per gram of albumin) to calculate corrected total calcium led to major errors in estimating ultrafilterable calcium in these patients. The PTH concentrations in turn correlated with the degree of deviation between estimated and measured ultrafilterable calcium concentrations. Ionised calcium was low in seven of ten additional hypoalbuminaemic patients studied whereas correction of total calcium for albumin indicated normocalcaemia in all. Thus correction of total calcium in patients with hypoalbuminaemia by formulae which use a fixed binding ration of calcium to albumin may give an erroneous impression of normocalcaemia. The increase in calcium binding ratio during hypoalbuminaemia needs to be considered during assessment of calcium status in these patients.

Calcium↗
PubMed1981

Effect of erythrocytes and globulin on renal functions of the isolated rat kidney.

We assessed the effects in isolated perfused rat kidneys of adding globulin or erythrocytes to Krebs-Henseleit bicarbonate perfusate with albumin as its principal source of colloid osmotic pressure during 3 h of perfusion. Colloid osmotic pressure varied between 11 and 58 mmHg. Bovine or human immunoglobulin substituted in part for albumin produced vasodilation, whereas rat erythrocytes added to albumin at a 5% hematocrit caused vasoconstriction. Inclusion of both globulin and erythrocytes in the perfusate was associated with an intermediate response. Kidneys perfused with albumin alone showed progressive decline in GFR, increasing vascular resistance, and increasing proteinuria correlating with kidney weight gain during perfusion. Onset of GFR and resistance changes were delayed and their magnitude decreased by increasing oncotic pressure. Estimated glomerular filtrate protein concentration of albumin-perfused kidneys progressively increased from 20 to 150 mg/dl. The presence of erythrocytes or globulin in the perfusate prevented the increase in vascular resistance and reduced the degree of decrease in GFR seen with albumin alone in the perfusate and reduced the time-dependent increase in proteinuria by 80%. The effects of globulin and erythrocytes on proteinuria were additive. The prevention of changes in hemodynamics, glomerular filtration, macromolecular clearance, subcapsular fluid accumulation, and organ weight gain for up to 5 h of perfusion by adding erythrocytes and globulins to the albumin perfusate suggest that these agents may be necessary for preventing interstitial edema and for maintaining renal function in vitro.

Animals↗
PubMed1981

Suppression of secondary hyperparathyroidism by propranolol in renal failure patients.

Renal osteodystrophy in part due to secondary hyperparathyroidism, is one of the major unresolved problems affecting patients on chronic hemodialysis. In addition, evidence has shown that parathyroid hormone (PTH) is toxic to other organ systems besides bone. The results of a prospective study on the effect of propranolol in reducing PTH levels in chronic renal failure patients on hemodialysis are reported. Propranolol administration reduced PTH levels by over 50-75%. The levels of calcium, phosphorus, alkaline phosphatase and hematocrit were variable, but patients with severe derangements in these measurements also seemed to benefit from propranolol. It should now be determined by larger and longer studies whether these biochemical improvements can be translated into clinical benefits.

Alkaline Phosphatase↗
PubMed1979

Prostaglandin E and hypercalcemia in breast carcinoma: only a tumor marker? A need for perspective.

Prostaglandin E concentrations were measured in a patiet with breast carcinoma, hypercalcemia, undetectable parathyroid hormone (PTH) and no evidence of bone metastases. Catheterization of the drainage bed of her tumor documented production of E series prostaglandins. Treatment with the largest recommended doses of indomethacin for 10 days failed to lower her plasma prostaglandin E (PGE) concentrations or to correct the hypercalcemia, but it normalized urinary excretion of PGE. Subsequent chemotherapy reduced prostaglandin concentrations toward normal values concomitant with a reduction of clinically estimated tumor burden. During this period of time, serum calcium concentrations had no consistent relationship to the plasma PGE levels. We suggest that PGE merely reflected the tumor burden of this patient and did not directly contribute to the genesis of her hypercalcemia. The pertinent literature relating PGE and hypercalcemia is reviewed.

Antineoplastic Agents↗
PubMed1979

Excretion and metabolism of catecholamines by the isolated perfused rat kidney.

The excretion and metabolism of labeled epinephrine and norepinephrine by the isolated, perfused rat kidney were studied. The excretion of both catecholamines significantly exceeded the amount filtered, thus providing direct evidence of net tubular secretion. Renal clearance of epinephrine was significantly greater than that of norepinephrine. Tubular secretion was a linear function of the concentration of unbound catecholamine in the medium with no demonstrable tubular maximum at the concentrations studied. The isolated kidney removed catecholamines from the medium by metabolism as well as excretion in the urine. O-Methylation was the major metabolic route and O-methylated metabolites were rapidly excreted and concentrated in urine. Preferential excretion and metabolism of epinephrine were confirmed in double-label experiments in which [14C]epinephrine and [3H]norepinephrine were perfused together. The ratio of 14C:3H in urine exceeded that in perfusion medium for total radioactivity as well as for catecholamines and O-methylated amines. The present study thus provides direct evidence for (a) net tubular secretion of epinephrine and norepinephrine with a direct relationship between secretion and medium concentration; (b) significant renal metabolism of both epinephrine and norepinephrine with O-methylation as the major metabolic route; and (c) preferential excretion and metabolism of epinephrine.

Animals↗
PubMed1978

A possible role for propranolol in the treatment of renal osteodystrophy.

The effect of propranolol upon parathyroid hormone (P.T.H) concentrations was investigated in patients undergoing chronic haemodialysis. 9 patients receiving propranolol for the treatment of hypertension or angina pectoris were compared with 25 similar patients not taking the drug. P.T.H. and alkaline phosphatase concentrations were lower in patients receiving propranolol and there was less radiological evidence of renal osteodystrophy in these patients. Prospective studies are needed to determine whether propranolol may be helpful as an adjunct to other therapy in reversing or preventing renal osteodystrophy.

Adolescent↗
PubMed1978

Mechanisms of hypercalcemia in malignancy.

Various hormones have been implicated in the genesis of hypercalcemia in patients with malignancy. Ectopic secretion of PTH by tumor has been documented in only a few patients; rather, elevated levels of circulating iPTH have been presumed to reflect tumor production of hormone in most patients. Small fragments of PTH, as well as polypeptides larger than native PTH, have been described; their biological roles are unclear. The pattern of immunoreactivity, however, has been used to differentiate patients with ectopic hyperparathyroidism from patients with concomitant primary hyperparathyroidism. Vitamin D-like sterols produced by breast cancer seldom reach plasma levels necessary for physiological effects. Members of the prostaglandin family have been proposed to induce hypercalcemia through osteoclast activation or alteration of the immune system and also to affect the frequency of bone metastases. At present, no direct evidence is available to prove a direct role for these effects and prostaglandins are most useful as possible indicators of disease activity.

Bone Neoplasms↗
PubMed1978

Symptomatic hypocalcemia following combined calcitonin and mithramycin therapy for hypercalcemia due to malignancy.

Three patients with malignant disease received the usual recommended doses of mithramycin and calcitonin, either concurrently or concomitantly, because of severe life-threatening hypercalcemia. All three patients developed severe, symptomatic hypocalcemia. The mechanisms for this phenomenon are discussed. A possible synergism between calcitonin and mithramycin may prove to be hazardous in such patients and this possibility must be kept in mind when these agents are being considered as a combination treatment for hypercalcemia.

Calcitonin↗
PubMed1977

Effect of catecholamines on tubular function in the isolated perfused rat kidney.

Addition of norepinephrine or epinephrine to the isolated rat kidney perfused at constant pressure resulted in an increase in sodium reabsorption and the excretion of a dilute urine with an increase in free water clearance. Vasopressin reversed the fall in urinary osmolarity but not the diminution in sodium excretion. The urinary changes produced by catecholamines were blocked by propranolol but not by phenoxybenzamine, suggesting that they were mediated, at least in part, by beta receptors. Similar though less pronounced changes in sodium excretion and urinary osmolarity were produced by isoproterenol and phenylephrine, while the combination of these drugs induced marked dilution of the urine. The results suggest that circulating catecholamines or adrenergic nerves innervating the kidney directly influence renal tubular function and might, therefore, participate in the regulation of sodium and water excretion by the kidneys.

Animals↗
PubMed1976

Reversible renal failure following bilateral renal artery occlusive disease. Clinical features, pathology, and the role of surgical revascularization.

Three patients with severe hypertension and rapidly progressive oliguric renal failure who required dialysis were found by aortography to have bilateral renal artery occlusion or stenosis. Each had peripheral arteriosclerosis or an abdominal bruit. Following renal artery reconstructive surgery, all three patients recovered nearly normal renal function in 3 to 12 weeks, though mild hypertension persisted in two patients. The common findings of a normal-sized kidney with collateral blood flow and nearly normal histological features were predictive of recovery of renal function. Prolonged postoperative oliguria in two patients may have been due to increased preglomerular vascular resistance mediated by the renin-angiotensin system.

Acute Kidney Injury↗
PubMed1976

Multiple pumps for sodium reabsorption by the perfused kidney.

Several distinct transport mechanisms responsible for sodium reabsorption by the rat kidney can be identified by studying the function of isolated perfused kidneys. Approximately one-half of the fractional sodium reabsorption by the isolated perfused rat kidney appears to depend on Na-K-adenosine triphosphatase (AT-Pase) and is inhibited by ouabain. About 10 to 20% is associated with the reabsorption of bicarbonate and is blocked by acetazolamide. This fraction of transported sodium is unaffected by ouabain and therefore does not involve Na-K-ATPase. Neither furosemide nor ethacrynic acid produce further inhibition of sodium reabsorption in a kidney already exposed to ouabain and acetazolamide. Most of the residual transport of sodium is inhibited by cooling the perfused kidney, suggesting that it is powered by metabolic rather than physical sources of energy.

Acetazolamide↗
PubMed1975

Bicarbonate and sodium reabsorption by the isolated perfused kidney.

The role of bicarbonate reabsorption and of transtubular chloride gradients in the bulk reabsorption of sodium and water by renal tubules can be tested in the isolated perfused kidney by perfusing with a medium from which bicarbonate has been omitted. Perfusion of the isolated rat kidney with an artificial medium in which bicarbonate is replaced by chloride results in a fall in fractional reabsorption of sodium from 97 to 84%. Stepwise restoration of bicarbonate concentration in the perfusion medium to 25 meq/liter is associated with a parallel recovery of sodium reabsorption to control levels. Inhibition of bicarbonate reabsorption with acetazolamide produces a slightly smaller reduction in sodium reabsorption (97-89%), an effect not seen in the absence of bicarbonate. Acetazolamide greatly increases phosphate excretion and free water clearance in a way consistent with suppression of proximal tubular reabsorption. By contrast, simple omission of bicarbonate from the perfusing medium does not alter phosphaturia or free water clearance. Reabsorption of bicarbonate appears to account for a fraction of sodium reabsorption roughly equivalent to the proportion of sodium associated stoichiometrically with bicarbonate in the glomerule filtrate. The data do not support the hypothesis that the development of a transtubular chloride gradient is critically important for the reabsorption of a large fraction of the glomerular filtrate.

Acetazolamide↗
PubMed1975

Potassium transport by the isolated perfused kidney.

Rat kidneys perfused outside of the body with an artificial medium are able to increase their fractional excretion of potassium in response to a rising concentration of potassium in the medium but never show net secretion of potassium. By contrast, isolated perfused kidneys from chronically potassium-loaded rats regularly secrete potassium in excess of the amount filtered. Ouabain completely blocks the secretion of potassium by these isolated kidneys, suggesting that Na-K-ATPase mediates potassium secretion by potassium-adapted rats. Neither sodium deprivation, pretreatment with deoxycorticosterone, nor pretreatment with methylprednisolone prepared the kidney to secrete potassium, despite stimulation of Na-K-ATPase activity in cortex or outer medulla. Potassium loading was the only maneuver tested that increased the activity of Na-Katpase in the inner medulla (white papilla) and also produced potassium secretion by the isolated kidney. Surgical ablation of the papilla abolished the net secretion of potassium normally seen in perfused kidneys of potassium-adapted rats, thus underlining the importance of the papilla in the process of potassium adaptation.

Adaptation, Physiological↗