Hemodynamic stability ensured by a low dose, low volume, unilateral hypobaric spinal block: modification of a technique.

We report the case of an 89-year-old female with a history of arterial hypertension, intermittent rapid atrial fibrillation and severe aortic valve stenosis, suffering from femoral neck fracture. Hyperbaric unilateral spinal anesthesia is a known technique to obtain stable hemodynamics combined with the possibility of continuous neurologic evaluation and preservation of cognitive functions. Because a hyperbaric unilateral technique can be very painful in case of traumatic hip fracture, a low dose, low volume, unilateral hypobaric spinal block may be an adequate alternative. In the present case report, a unilateral hypobaric spinal anesthesia was performed using 5 mg of bupivacaine in a 1.5 mL volume and a slow and steady, "air-buffered", directed injection technique, to allow an urgent hip arthroplasty. During surgery the patient was kept in the lateral recumbent position. Hemodynamics remained stable throughout the entire procedure without any need for vasoconstrictors. The impact of aortic valve stenosis combined with atrial fibrillation on anesthetic management and our considerations to opt for a unilateral hypobaric spinal anesthesia are discussed.

The role of renal sympathetic nerves in experimental chronic cyclosporine nephropathy.

BACKGROUND: Sympathetic nervous system hyperactivity has been postulated to play a major role in the intense intrarenal vasospasm and hypertension provoked by cyclosporine. It has been argued that the denervated renal allograft may be partially protected from the tubulointerstitial fibrosis associated with chronic cyclosporine administration compared with innervated kidneys in extrarenal transplantation. METHODS: Utilizing a model of chronic cyclosporine nephropathy in which striped fibrosis develops in the uninephrectomized salt-depleted rat, the effect of renal denervation on renal structure and function was examined. Sprague-Dawley rats maintained on a low-salt diet underwent uninephrectomy and contralateral renal denervation or sham denervation, followed by cyclosporine 15 mg/kg daily by injection. RESULTS: After 21 days, glomerular filtration was markedly depressed and linear zones of tubular atrophy and interstitial fibrosis had developed compared with vehicle-treated control animals (P<0.001). However, there was no significant difference in either renal function or structure between denervated and sham-operated animals treated with cyclosporine. CONCLUSION: We conclude that renal sympathetic neural hyperactivity is not important in the development of chronic cyclosporine nephropathy.

Cyclopentenyl cytosine inhibits cytidine triphosphate synthetase in paediatric acute non-lymphocytic leukaemia: a promising target for chemotherapy.

Cytidine triphosphate (CTP) synthetase is a key enzyme in the anabolic pathways of cytosine and uracil ribonucleotide metabolism. The enzyme catalyses the conversion of uridine triphosphate (UTP) into CTP, and has a high activity in various malignancies, which has led to the development of inhibitors of CTP synthetase for therapeutic purposes. We studied both CTP synthetase activity and ribonucleotide concentrations in leukaemic cells of 12 children suffering from acute non-lymphocytic leukaemia (ANLL), and performed incubation experiments with cyclopentenyl cytosine (CPEC), a nucleoside analogue that is capable of inhibiting CTP synthetase. The CTP synthetase activity in ANLL cells (5.1+/-2.3 nmol CTP/mg/h) was significantly higher compared with granulocytes of healthy controls (0.6+/-0.4 nmol CTP/mg/h, P=0.0002), but was not different from the CTP synthetase activity in non-malignant CD34+ bone marrow cells (5. 6+/-2.4 nmol CTP/mg/h). Major shifts were observed in the various ribonucleotide concentrations in ANLL cells compared with granulocytes: the absolute amount of ribonucleotides was increased with a substantial rise of the CTP (2.4 versus 0.4 pmol/microg protein, P=0.0007) and UTP (8.7 versus 1.6 pmol/microg protein, P=0. 0007) concentrations in ANLL cells compared with granulocytes. Treatment of ANLL cells in vitro with CPEC induced a major depletion (77% with 2.5 microM of CPEC) in the concentration of CTP, whilst the concentrations of the other ribonucleotides remained unchanged. Therefore, the high activity of CTP synthetase in acute non-lymphocytic leukaemic cells can be inhibited by CPEC, which provides a key to a new approach for the treatment of ANLL.

Adenocarcinoma of the colon metastasizing to the foot masquerading as osteomyelitis.

The authors report an unusual case of adenocarcinoma of the colon metastasizing to the foot. The initial diagnosis of osteomyelitis based on clinical, radiographic, and radionuclide uptake findings led to improper prolonged treatment, resulting in a major complication. A diagnostic biopsy of the involved bone is essential in any case in which the clinical diagnosis is uncertain.

Anuric renal failure from massive bilateral renal hematoma following extracorporeal shock wave lithotripsy.

We report a case of large bilateral perirenal and intrarenal hematoma formation leading to prolonged anuria in the absence of obstruction following extracorporeal shock wave lithotripsy. With conservative management, including the need for hemodialysis support, renal function gradually returned. A mechanism for this patient's anuric renal failure is postulated and caution is advised when considering simultaneous bilateral extracorporeal shock wave lithotripsy in patients with a potential risk of bleeding.

Determination of CTP synthetase activity in crude cell homogenates by a fast and sensitive non-radiochemical assay using anion-exchange high-performance liquid chromatography.

A non-radiochemical assay procedure for CTP synthetase was developed in which CTP is detected at 280 nm after separation with anion-exchange HPLC. A complete separation of all nucleoside triphosphates was achieved within 11 min and the minimum amount of CTP which could be accurately determined proved to be 5 pmol. Therefore, our assay procedure is ten-fold more sensitive compared to the frequently used radiochemical assays. The assay was linear with time and protein concentration, although at low protein concentration a lag phase was observed. An amount of 2 x 10(6) cells was already sufficient to determine the specific activity of CTP synthetase in HL-60 cells, lymphocytes and in lymphoblasts obtained from pediatric patients suffering from acute lymphoblastic leukemia.

Hyperbaric oxygen enhances the effects of meta-iodobenzylguanidine (MIBG) on energy metabolism and lipid peroxidation in the human neuroblastoma cell line SK-N-BE(2C).

In this paper we report the effects of the combination of MIBG (a structural analogue of norepinephrine, used in its radio iodinated form for the diagnosis and therapy of neuroblastoma) and hyperbaric oxygen on the human neuroblastoma cell line SK-N-BE(2c). Exposure of the neuroblastoma cells to hyperbaric oxygen conditions enhanced the effects of MIBG on cell proliferation, lipid peroxidation and energy metabolism of the cell line. Cell proliferation and energy metabolism were further decreased and lipid peroxidation further increased. Enhancement of the effects of MIBG by HBO may provide an explanation for the positive effects on the cumulative survival curve observed when stage IV neuroblastoma patients were treated with the combination of [131I] MIBG and HBO.

Meta-iodobenzylguanidine (MIBG) inhibits malate and succinate driven mitochondrial ATP synthesis in the human neuroblastoma cell line SK-N-BE(2c).

In this paper, we report on our studies of the effects of MIBG, a structural analogue of norepinephrine, on SK-N-BE(2c) cells. In micromolar concentrations, MIBG caused almost complete inhibition of the proliferation of SK-N-BE(2c) cells. In intact SK-N-BE(2c) cells, addition of MIBG led to a decrease of the ATP to ADP ratio. A progressive increase of the lactate to pyruvate ratio (due to increased lactate production) was observed after incubation of the cells with glucose and increasing concentrations of MIBG. In cells treated with digitonin, MIBG inhibited malate driven ATP synthesis. Comparable inhibition of ATP synthesis with succinate as a substrate required higher concentrations of MIBG. These results indicate that, apart from inhibition of complex I, MIBG was capable of inhibiting at least one other complex of the respiratory chain. Although maximal inhibition of ATP synthesis was observed at a concentration of 10 microM, optimal inhibition of cell proliferation occurred at a MIBG concentration > 25 microM. This suggests that MIBG also influences other cellular processes apart from mitochondrial ATP synthesis, resulting in additional inhibition of cell proliferation.

A fast and novel assay of CTP synthetase. Evidence for hysteretic properties of the mammalian enzyme.

A novel assay of CTP synthetase was developed which allows the processing of large numbers of samples. The amount of glutamate produced by CTP synthetase was determined with glutamate dehydrogenase and the NAD analogue acetyl-pyridine-adenine dinucleotide was used to shift the initial unfavourable equilibrium towards the formation of a-ketoglutarate. The amount of glutamate determined with the assay was comparable to that of CTP. The assay proved to be linear with time up to 90 min and protein concentrations up to 520 micrograms/ml. However, at low protein concentrations as well as at early time points a lag phase was observed. This hysteretic phenomenon of CTP synthetase may be due to the association-dissociation equilibrium that exists between the various polymerisation states of the enzyme.

Experimental nephrotoxicity, hepatotoxicity and pharmacokinetics of cyclosporin G versus cyclosporin A.

Cyclosporin G (CsG) is an analogue of cyclosporin A (CsA) with strong immunosuppressive activity. We compared these two drugs in a rat model in which salt depletion promotes irreversible renal interstitial fibrosis with renal dysfunction in animals given CsA for three weeks. When both drugs were given in the same dosage on a weight basis (15 mg/kg/day, subcutaneously), CsA blood levels were higher than CsG (3305 vs. 1824 ng/ml, P < 0.001). This could be explained by a higher CsG clearance (6.4 vs. 4.3 ml/min/kg in CsA, P < 0.0001) resulting in smaller CsG area under the curve. There was also lower renal and hepatic CsG tissue concentrations. CsA induced a dramatic decrease in GFR, 0.14 in CsA versus 0.67 ml/min/100 g in control, P < 0.001, and increased urinary excretion of N-acetyl beta-D-glucosaminidase (NAG), 21 in CsA versus 13 IU/gCr in control rats, P < 0.001. CsG-treated and control rats had similar GFR and urinary NAG. When CsA dosage was decreased to 7.5 mg/kg blood levels were similar to those found with CsG 15 mg/kg. CsA at this dose caused a reduced GFR (0.29 ml/min/100 g) and an increased urinary NAG (20 IU/gCr) (P < 0.01 vs. control for both). Both dosages of CsA induced considerable cortical and medullary injury (interstitial fibrosis and tubular atrophy), more severe than the histological damage found in CsG-treated rats. Neither drug promoted significant changes in liver function or histology.(ABSTRACT TRUNCATED AT 250 WORDS)

Nephrotoxicity of immunosuppressive drugs.

Acute and chronic nephrotoxicity frequently limits the therapeutic benefits of immunosuppressive therapy for transplant and autoimmune indications. The clinical aspects, pathophysiology, and relevant pharmacology of current and future immunosuppressive drugs are reviewed in this paper. Insights gained from experimental models of chronic nephrotoxicity associated with tubulointerstitial fibrosis are presented.

Nephrotoxicity of immunosuppressive drugs.

Drugs used to modify the immune response in solid organ transplantation or autoimmune disease may cause dose-related nephrotoxicity. Cyclosporine, FK506, cyclosporine G, and rapamycin have all been studied experimentally and to a more limited extent in patients. This paper summarizes this literature using data from clinically relevant animal models.

Surgical management of painful polycystic kidneys.

In patients with symptomatic PKD who have failed medical management, surgical intervention is a reasonable option, providing long-term pain relief in the majority of patients. Individuals for whom this approach is indicated are usually narcotic dependent or disabled by pain. Cyst decompression surgery does not appear to significantly retard or arrest progressive renal insufficiency. On the other hand, widespread fears that cyst decompression might hasten renal failure are clearly unfounded. The application of newer laparoscopic techniques to this problem may allow for a wider range of symptomatic patients to realize the benefits of cyst decompression.

Dissociation of glomerular filtration rate from tubulointerstitial fibrosis in experimental chronic cyclosporine nephropathy: role of sodium intake.

In addition to its well-recognized ability to provoke acute renal dysfunction by promoting intense renal vasoconstriction, cyclosporine produces a chronic tubulointerstitial nephropathy characterized by striped interstitial fibrosis in humans. With a model of chronic cyclosporine nephropathy in which striped fibrosis develops in the uninephrectomized salt-depleted rat, the relationship between renal functional impairment and structural changes was studied during cyclosporine treatment and after its withdrawal in order to ascertain the natural history of this lesion. Groups of uninephrectomized rats maintained on a salt-depleted (-NaCl) or salt-replete (+NaCl) diet were treated with cyclosporine, 15 mg/kg per day, or vehicle by sc injection. GFR and morphology were assessed at 14 and 28 days of treatment and at intervals up to 28 days after drug withdrawal. Although GFR was similarly depressed in cyclosporine-treated animals on either diet (P < 0.001 versus vehicle), tubulointerstitial injury was largely confined to cyclosporine-treated rats on the -NaCl diet (P < 0.001 versus cyclosporine/+NaCl and vehicle). At 28 days after the withdrawal of cyclosporine, there was a marked discordance between renal structure and function in the cyclosporine/-NaCl group as GFR returned toward normal (P > 0.05 versus cyclosporine/+NaCl) but prominent tubulointerstitial injury persisted and, in some instances, even progressed (P < 0.001 versus cyclosporine/+NaCl and vehicle). Thus, sodium intake emerges as an important determinant of structural tubulointerstitial changes, whereas reductions in GFR during cyclosporine therapy are equivalent in sodium-depleted or sodium-replete animals.

Clinical management of autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a common systemic genetic disease which comprises 8 to 10% of patients treated by dialysis and transplantation. Breakthroughs in molecular genetics and cell biology have led to new insights into cyst formation and growth. Until the specific genetic defects are identified, the management of this disorder will necessarily be empiric. This paper discusses current management strategies in ADPKD focusing on hypertension, hematuria, pain and infection. Special considerations for management of end-stage renal failure in patients with ADPKD are also reviewed.

Production of less chronic nephrotoxicity by cyclosporine G than cyclosporine A in a low-salt rat model.

Chronic tubulointerstitial nephropathy during long-term cyclosporine A (CsA) use has led to a search for equally effective but safer analogues. In this study we evaluated one of these analogues, cyclosporine G (CsG), in a rat model of chronic cyclosporine nephrotoxicity. CsG has immunosuppressive effects equivalent to CsA when dosed on a weight basis. Pair-fed Sprague-Dawley rats kept on a low-salt rice diet were given CsA 15 mg/kg, CsG 15 mg/kg, CsG 25 mg/kg, or vehicle subcutaneously. After 21 days, CsA animals had a lower glomerular filtration rate, measured by inulin clearance (0.16 +/- 0.04 ml/min/100 g) and higher serum creatinine (0.94 +/- 0.06 mg/dl) than CsG 15 mg/kg (GFR: 0.41 +/- 0.10 ml/min/100 g and serum creatinine: 0.68 +/- 0.09 mg/dl), CsG 25 mg/kg (GFR: 0.39 +/- 0.16 ml/min/100 g) or control rats (GFR: 0.62 +/- 0.06 ml/min/100 g; serum creatinine: 0.56 +/- 0.03 mg/dl), respectively (P < 0.05). The CsA group had considerable cortical and medullary injury (interstitial fibrosis and tubular atrophy), whereas both groups of CsG animals had more limited changes. Despite the same or larger doses of CsG on a weight basis, cyclosporine blood levels were significantly lower in CsG than CsA rats. We conclude that CsG, an analogue of cyclosporine with immunosuppressive activity equivalent to that of CsA, produced less nephrotoxicity in a model of chronic renal injury in rats, using both functional and structural parameters.

Application of simple chromatographic methods for the diagnosis of defects in pyrimidine degradation.

Recent findings suggest that inborn errors of pyrimidine catabolism are less rare than generally assumed. We propose a complete set of diagnostic methods for these disorders, suitable for the clinical chemistry laboratory, and present relevant reference data. Applications of thin-layer chromatography, high-performance liquid chromatography, and conventional cation-exchange amino acid analysis lead to detection of various defects in pyrimidine degradation, including the recently described deficiencies of dihydropyrimidine dehydrogenase and dihydropyrimidinase. We also illustrate the potential of the methods to analyze for the catabolites expected to be increased in the urine of patients with ureidopropionase deficiency. Possible pitfalls in the diagnosis and ways to prevent misdiagnosis are demonstrated. The methods offer possibilities for clinical chemistry laboratories to extend their diagnostic capacity to the new area of pyrimidine degradation defects.

Cyst fluid from human autosomal dominant polycystic kidneys promotes cyst formation and expansion by renal epithelial cells in vitro.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive renal enlargement, culminating in renal insufficiency in over one half of affected individuals. The highly variable onset and clinical course of ADPKD may be due to factors extrinsic to the genetically defined renal cysts. In this study, cyst fluid samples from 12 nonazotemic and 18 azotemic ADPKD subjects were examined for in vitro biologic activity that promotes cellular proliferation and the secretion of fluid by renal epithelial monolayers, two pathogenetic mechanisms that have critical roles in the formation and the rate of expansion of renal cysts. Cyst fluid added to culture medium (final concentrations, 1 to 20%) caused Madin-Darby canine kidney cells and human kidney cortex (HKC) cells derived from primary cultures to form cysts in Type I collagen matrix. Cyst fluid stimulated the net transepithelial secretion of fluid by polarized monolayers composed of these same cells. Absolute levels of fluid secretory activity determined by MDCK bioassay were correlated directly with the rate of fluid secretion by HKC cell monolayers and with the extent of cyst formation by MDCK and HKC cells embedded in collagen matrix. The secretory activity of urine was negligible; secretory activity was detectable in the serum of normal and ADPKD subjects, but the levels were much lower than in cyst fluid. cAMP agonists prostaglandins E1 and E2, arginine vasopressin, and 8-Br-cAMP stimulated fluid secretion by MDCK and HKC monolayers, but these substances did not cause HKC cells to form cysts in collagen matrix, whereas cyst fluid did. Among other naturally occurring growth factors and autacoids, only epidermal growth factor and transforming growth factor alpha stimulated cyst formation by HKC cells; however, the capacity of cyst fluid to stimulate fluid secretion was not affected by treatment with antiserum to epidermal growth factor. It was concluded that potent, and possibly unique, substances in the cyst fluids of individuals with ADPKD support and augment biologic processes in renal epithelial cells that may be important in the promotion of progressive cyst expansion.