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L J Mandel

Publications and source records attributed to L J Mandel.

At least 55 records · Page 3Linked to original sources
PubMed1988

Clinical significance and pathogenesis of hyperbilirubinemia associated with Staphylococcus aureus septicemia.

PURPOSE: Our goal was to examine the clinical significance of hyperbilirubinemia in patients with Staphylococcus aureus endocarditis. In addition, preliminary data concerning the possible mechanism of cholestasis observed during S. aureus septicemia are presented. PATIENTS AND METHODS: This study had two parts: a clinical investigation and a laboratory investigation. In the former, patients with endocarditis were identified through chart review. Those with admission total serum bilirubin levels of 2.0 mg/dl or greater were considered to have hyperbilirubinemia. In the latter investigation, the hepatic storage capacity and transport maximum for sulfobromophthalein (BSP), an organic dye that is rapidly taken up and excreted by the liver, were determined by measuring the change in serum concentration and the corresponding hepatic removal rate at various BSP infusion rates. Measurements were conducted before and after the infusion of Escherichia coli-derived lipopolysaccharide in some rabbits, after the infusion of resuspended S. aureus in others, and after the infusion of lipoteichoic acid in the remainder. RESULTS: Eleven of 47 consecutive patients with S. aureus endocarditis were noted to have hyperbilirubinemia without clinical or laboratory evidence of hepatic bacterial infection. Compared with the remaining 36 patients, these 11 patients had a significantly lower mean platelet count and a higher serum creatinine level and white blood cell count. Although none of the 47 patients were hypotensive on admission, four of the 11 hyperbilirubinemic patients died of overwhelming sepsis, compared with two of the 36 remaining patients (p less than 0.05). When one of the clinical isolates of S. aureus or lipoteichoic acid was infused into conscious rabbits, there was a marked decrease in the hepatic transport maximum and an increase in the relative hepatic storage capacity of sulfobromophthalein. Similar changes were noted following the administration of lipopolysaccharide. CONCLUSION: Our data suggest that the presence of hyperbilirubinemia in patients with S. aureus sepsis may identify persons at high risk of dying from overwhelming sepsis. It further suggests that lipoteichoic acid may play an important role in causing defective hepatic excretory function that is responsible for hyperbilirubinemia.

Adult↗
PubMed1988

Intracellular distribution and depletion of glutathione in rabbit renal proximal tubules.

The intracellular compartmentation of glutathione (GSH) in rabbit renal proximal tubules under various conditions was examined using the digitonin fractionation technique. Tubules with GSH contents similar to those found in vivo (13.4 +/- 0.8 nmol . mg protein-1) and with decreasing amounts of GSH had an apparently constant mitochondrial GSH pool of 1.9 +/- 0.1 nmol . mg protein-1. This renal mitochondrial GSH pool is similar in size to that of hepatic mitochondria and represents 10 to 15 percent of the total cellular GSH. Using phorone and diethyl maleate to decrease tubular GSH concentrations, the cytosolic GSH pool could be depleted without affecting the mitochondrial GSH pool. Depletion of the cytosolic GSH pool and decreases in the mitochondrial pool of up to 42 percent were not associated with mitochondrial dysfunction nor loss of tubular viability.

Animals↗
PubMed1988

Determination of sulfobromophthalein excretion in rabbits.

The excretion of sulfobromophthalein (BSP) is determined by hepatic uptake (storage capacity) and secretion (transport maximum). We calculated the BSP excretion data in six rabbits by measuring the rate of rise of BSP at various infusion rates. The relative storage capacity was determined to be 0.34 +/- 0.13 mg.mg-1.dl-1.kg-1. The transport maximum was calculated to be 0.91 +/- 0.12 mg.min-1.kg-1. These results compare closely with previously reported results using more direct measurements that require anesthesia and surgical cannulation of the biliary tree. Repeated studies were easily performed. Our method provides a reliable and simple technique to study the effects of various conditions or substances on BSP excretion in conscious, unanesthetized rabbits.

Animals↗
PubMed1988

Metabolic substrate utilization by rabbit proximal tubule. An NADH fluorescence study.

The effects of various short-chain fatty acids, carboxylic acids, and amino acids on NADH fluorescence and oxygen consumption (QO2) of rabbit proximal tubule suspensions were determined. The short-chain fatty acids were the most effective substrates in increasing NADH fluorescence and QO2, followed by the carboxylic acids and amino acids. All of the substrates tested that increased NADH fluorescence proportionally increased QO2. This implies that the primary effect of these substrates was to increase QO2 by increasing the delivery of reducing equivalents to NAD and not by stimulating ATP hydrolysis directly. The relative affinity of several substrates to increase NADH fluorescence was also determined. The short-chain fatty acids had the highest affinity (10 microM range) followed by the carboxylic acids (100 microM range). These data demonstrate that the metabolic rate and NADH redox state of the renal cortical cell is very sensitive to the type of metabolic substrate available.

Amino Acids↗
PubMed1988

Mechanisms whereby exogenous adenine nucleotides improve rabbit renal proximal function during and after anoxia.

When a suspension of rabbit proximal tubules is subjected to anoxia, ATP falls by 80-90% during 40 min of anoxia, and upon reoxygenation (reox) the cells only recover 25-50% of their initial ATP. Addition of Mg-ATP (magnesium chloride-treated ATP), Mg-ADP, or Mg-AMP (five aliquots of 200 nmol/ml added 10 min apart) during anoxia causes complete recovery of ATP levels, and respiratory and transport function after 40 min of reox. Similar additions of adenosine (ADO), or inosine (INO), or Mg-ATP only during reox are less effective. Lactate dehydrogenase (LDH) release after 40 min of anoxia is 30-40% under control conditions, only 10-15% when adenine nucleotides or ADO are added during anoxia, and 20% when INO is added, suggesting that these additions may stabilize the plasma membrane during anoxia and help preserve cellular integrity. During reox, recovery may depend on the entry of ATP precursors and, therefore, we explored the mechanism whereby exogenous ATP increases the intracellular ATP content. Additions of Mg-ATP, Mg-ADP, or Mg-AMP to continuously oxygenated tubules increase cellular ATP content three- to fourfold in 1 h. The added ATP and ADP are rapidly degraded to AMP, and more slowly to ADO, INO, and hypoxanthine. Furthermore, the ATP-induced increase in cellular ATP is abolished by the exogenous addition of adenosine deaminase, which converts extracellular ADO to INO. These results suggest that the increase in cellular ATP requires extracellular ADO. The ADO obtained from the breakdown of AMP may be preferentially transported into the renal cells to be resynthesized into cellular AMP and ATP.

Adenine Nucleotides↗
PubMed1987

Mitochondrial toxicity of 2-bromohydroquinone in rabbit renal proximal tubules.

2-Bromohydroquinone (BHQ) is a nephrotoxic metabolite of bromobenzene and a model toxic hydroquinone. The primary goal of these studies was to determine whether BHQ produces toxicity in rabbit renal proximal tubules by inhibiting mitochondrial function. BHQ induces a specific sequence of cellular events. Initially there was decrease in tubular glutathione content followed by a decrease in nystatin-stimulated ouabain-sensitive respiration. A decrease in cell viability, as measured by a decrease in lactate dehydrogenase retention, was late event. Associated with the decrease in respiration was a decrease in intracellular ATP content. Probing of mitochondrial function in the tubule revealed that BHQ did inhibit mitochondrial function in a somewhat selective manner. State 3 respiration was inhibited prior to changes in the rate of electron flow through cytochrome c-cytochrome oxidase. It is postulated that BHQ may initially inhibit state 3 respiration by inhibiting the adenine nucleotide translocator and/or the F1-ATPase.

Adenosine Monophosphate↗
PubMed1987

A mechanism of S-(1,2,3,4,4-pentachloro-1,3-butadienyl)-L-cysteine toxicity to rabbit renal proximal tubules.

S-(1,2,3,4,4-Pentachloro-1,3-butadienyl)-L-cysteine (PCBC) has been identified as the penultimate compound responsible for hexachlorobutadiene-induced nephrotoxicity. The primary goal of these studies was to determine the mechanism of PCBC-induced toxicity in rabbit renal proximal tubules by examining the early changes in tubular physiology. PCBC (20-500 microM) induced a specific sequence of toxic events. Following 15 min of exposure, 200 microM PCBC increased basal (25%) and ouabain-insensitive (78%) respiration. This was followed by a decrease in basal (46%), nystatin-stimulated (54%), and ouabain-insensitive (21%) respiration and a decrease in glutathione content (79%). Finally, there was a decrease in cell viability as measured by a decrease in LDH retention at 60 min. Direct probing of mitochondrial function revealed that the initial increase in respiration resulted from the uncoupling of oxidative phosphorylation, while the late changes in respiration appeared to result from gross mitochondrial damage characterized by inhibited state 3 respiration, inhibited cytochrome c-cytochrome oxidase, and inhibited electron transport. Studies utilizing tubules with decreased glutathione content revealed that glutathione plays little if any role in the early events of PCBC-induced toxicity. These results suggest that PCBC-induced mitochondrial dysfunction may initiate the renal proximal tubule injury.

Animals↗
PubMed1987

Renal metabolism and acute renal failure.

We briefly review what appear to be the most important elements responsible for renal cell injury during and after oxygen deprivation. Recent studies in numerous laboratories have vastly improved our understanding of the changes in cell function that occur during ischemia and yet, the underlying mechanisms by which tubule damage and cell death occur remain elusive. We attempt to separate the effects that occur during ischemia or anoxia from those occurring during reperfusion (reoxygenation). These are not always separable, especially because it appears that ischemia initiates a series of complex events that may only become manifested during reperfusion. Ischemia-induced renal dysfunctions are clearly multifactorial events that will require major efforts to unravel.

Acute Kidney Injury↗
PubMed1987

Fluorescent measurements of intracellular free calcium in isolated toad urinary bladder epithelial cells.

Sodium-calcium exchange has been suggested to play a pivotal role in the regulation of cytosolic free calcium (Caf) by epithelial cells. Using isolated epithelial cells from the toad urinary bladder, Caf has been measured using the intracellular Ca-sensitive fluorescent dyes Fura 2 and Quin 2. Dye loading did not alter cell viability as assessed by measurements of ATP and ADP content or cell oxygen consumption. When basal Caf was examined over a wide range of cell dye content (from 0.04 to 180 nmol dye/mg protein) an inverse relationship was observed. At low dye content, Caf was 300-380 nM and, as dye content was increased, Caf progressively fell to 60 nM. Using low dye content cells, in which minimal alteration in Ca steady state would be expected, the role for plasma membrane Na-Ca exchange was examined using either medium sodium substitution or ouabain. While medium sodium substitution increased Caf, prolonged treatment with ouabain had no effect on Caf despite a clear increase in cell sodium content. The lack of effect of ouabain suggests that Na-Ca exchange-mediated Ca efflux plays a minimal role in the regulation of basal Caf. However, exchange-mediated Ca efflux may play a role in Caf regulation when cytosolic calcium is elevated.

Animals↗
PubMed1987

Na+-K+-ATPase activity in medullary thick ascending limb during short-term anoxia.

Na+-K+-ATPase activity was measured in a suspension of rabbit medullary thick ascending limb tubules under oxygenated and anoxic conditions. Oxygenated, K-depleted tubules rapidly take up added extracellular potassium accompanied by a simultaneous increase in oxygen consumption. The ATP/O2 ratio was 12.5 +/- 0.7, suggesting a tight coupling between oxidative metabolism (6 ATP/O2) and Na+-K+-ATPase activity (2 K/ATP). On reaching anoxia, the tubules released potassium into the medium, but this rate was accelerated by the addition of ouabain, which indicated that the Na+-K+-ATPase was still operative in anoxia. Because 10 min of anoxia led to only a 15.7% decline in potassium content, a new steady state of potassium uptake and leakage must be reached during anoxia. Anaerobic metabolism maintained 73% of cellular ATP during 10 min of anoxia. Exposure of anoxic tubules to iodoacetate produced a 57% decline in ATP levels and a 33% decline in potassium content, which indicated that glycolysis is an important pathway in supplying energy during anaerobiosis.

Acute Disease↗
PubMed1986

Binding of 3H-phenamil, an irreversible amiloride analog, to toad urinary bladder: effects of aldosterone and vasopressin.

Phenamil, an analog of amiloride, has previously been shown to bind specifically to sodium channels in toad bladder (J.L. Garvin et al., J. Membrane Biol. 87:45-54, 1985). In this paper, 3H-phenamil was used to measure sodium channel density in both isolated epithelial cells and intact bladders. From the specific binding to intact bladders, a channel density of 455 +/- 102 channels/micron2 was calculated. No correlation between specific binding and the magnitude of irreversible inhibition of short-circuit current was found. Pretreatment of intact bladders with 1 mg/ml trypsin reduced specific binding to isolated cells by 82 +/- 5%. In isolated cells, neither aldosterone nor vasopressin had any significant effect on specific phenamil binding. It is inferred that phenamil binds to both open and closed channels which may be either in the mucosal membrane or in the submembrane space. Finally, and rather surprisingly, we found that 3H-phenamil binds irreversibly to the basolateral membrane at concentrations as low as 4 X 10(-7) M. Therefore, care must be used in interpreting binding studies with amiloride or its analog at such concentrations.

Aldosterone↗
PubMed1986

Potassium transport in the rabbit renal proximal tubule: effects of barium, ouabain, valinomycin, and other ionophores.

Potassium fluxes in a suspension of rabbit proximal tubules were monitored using a potassium-sensitive extracellular electrode. Ouabain (10(-4) M) and barium (5 mM) were used to selectively quantitate the potassium efflux pathway (105 +/- 5 nmol K+ X mg protein-1 X min-1) and the sodium pump-related potassium influx (108 +/- 7), respectively. These equal and opposite fluxes suggest that potassium accumulation in the cell occurs mainly through the sodium pump and that potassium efflux occurs mainly through barium-sensitive potassium channels. Thus the activity of the sodium pump (Na,K-ATPase) in the basolateral membrane of the proximal tubule is balanced by the efflux of potassium, presumably across the basolateral membrane, which has a high potassium permeability. In addition, the effect of valinomycin and other ionophores was examined on potassium fluxes and several metabolic parameters [oxygen consumption (QO2), ATP content]. The addition of valinomycin to the tubules produced a net efflux of potassium which was quantitatively equivalent to the efflux produced by the addition of ouabain. The valinomycin-induced efflux was mainly due to the activity of valinomycin as a mitochondrial uncoupler, which indirectly inhibited the sodium pump by allowing a rapid reduction of the intracellular ATP. Amphotericin, nystatin, and monensin all produced large net releases of intracellular potassium. The action of the ionophores could be localized to the plasma or mitochondrial membrane and classified into three groups, as follows: those which demonstrated full mitochondrial uncoupler activity (FCCP, valinomycin), those which had no uncoupler activity (amphotericin B, nystatin); and those which displayed partial uncoupler activity (monensin, nigericin).

Animals↗
PubMed1986

Heterogeneity of calcium compartmentation: electron probe analysis of renal tubules.

The objective of this study has been to determine the intracellular localization of calcium in cryofixed, cryosectioned suspensions of kidney proximal tubules using quantitative electron probe X-ray microanalysis. Two populations of cells have been identified: 1) "Viable" cells, representing the majority of cells probed, are defined by their relatively normal K/Na concentration ratio of approximately 4:1. Their measured Ca content is 4.1 +/- 1.4 (SEM) mmol/kg dry wt in the cytoplasm and 3.1 +/- 1.1 mmol/kg dry wt in the mitochondria, or an average cell calcium content of approximately 3.8 mmol/kg dry wt. 2) "Nonviable" cells, defined by the presence of dense inclusions in their mitochondria and a K/Na concentration ratio of approximately 1. The Ca content is 15 +/- 2 mmol/kg dry wt in the cytoplasm and 685 +/- 139 mmol/kg dry wt in the mitochondria of such cells. Assuming 25 to 30% of the cell volume is mitochondrial, the overall calcium content of such nonviable cells is approximately 210 mmol/kg dry wt. The presence of these inclusions in 4 to 5% of the cells would account for the average total Ca content measured in perchloric acid extracts of isolated proximal tubule suspensions (approximately equal to 18 nmol/mg protein or 12.6 mmol/kg dry wt). Whole kidney tissues display a large variability in total Ca content (4.5 to 18 nmol/mg protein, or 3.4 to 13.5 mmol/kg dry wt), which could be accounted for by inclusions in 0 to 4% of the cells. The electron probe X-ray microanalysis (EPXMA) data conclusively demonstrate that the in situ mitochondrial Ca content of viable cells from the kidney proximal tubule is low and support the idea that mitochondrial Ca may regulate dehydrogenase activity but probably does not normally control cytosolic free Ca.

Animals↗
PubMed1986

Primary active sodium transport, oxygen consumption, and ATP: coupling and regulation.

Several metabolic aspects of primary active transport have been explored in this communication. One emphasized theme entailed the need to investigate the properties of the mitochondria and the active transport systems within the intact cell. Several methodological and conceptual approaches were described that permitted such an analysis. The answers provided were sometimes qualitative or quantitative. Qualitative information was provided regarding the cytosolic signal linking active transport with respiration, suggesting that the cytosolic ADP concentration was an important element in that link. The intact renal cell was found to work normally at 50 to 60% of its maximal respiratory capacity, indicating that sufficient reserve capacity was present for increased metabolic demands. Several examples were described in which a combination of qO2 measurements and/or optical techniques were used to differentiate between effects of agents which act primarily on transport or metabolic events. Finally, the control of transport by metabolism was discussed, primarily emphasizing the role of ATP and Pi. One of the overall conclusions from these studies is that, in general, the mitochondria and the transport systems seem to display similar properties in the intact cell as they do in isolated form. However, uncertainties concerning the cellular microenvironment surrounding the mitochondria and the plasma membrane transporters have produced some interesting surprises concerning their function in the intact cell. More quantitative information on the energy compartmentation of the renal cell would be helpful to clarify numerous aspects of metabolic function.

Adenosine Diphosphate↗