Effect of growth hormone therapy on nitric oxide formation in cystic fibrosis patients.

Airway nitric oxide production is decreased in cystic fibrosis. As growth hormone therapy has been shown to increase nitric oxide production in growth hormone-deficient patients, it may also affect nitric oxide production in patients with cystic fibrosis. The objective of the present study was to investigate the effect of growth hormone therapy on systemic and airway nitric oxide formation in patients with cystic fibrosis. Nitric oxide metabolites in serum and urine, amino acid concentrations in serum and sputum, as well as exhaled nitric oxide, were measured in children with cystic fibrosis before, during and after 1 yr of treatment with human growth hormone. Nitric oxide metabolite concentrations increased significantly in serum and urine during the treatment period. Serum amino acid concentrations (including l-arginine, the substrate for nitric oxide synthases) also increased during treatment. The systemic bioavailability of l-arginine for nitric oxide synthases, expressed as ratio of l-arginine/l-ornithine+lysine, remained unchanged. In contrast, l-arginine concentrations in sputum decreased significantly during growth hormone treatment, as did exhaled nitric oxide levels. Treatment with growth hormone in children with cystic fibrosis decreases exhaled nitric oxide by reducing the concentration of l-arginine in the airways.

Unusual manifestation of posttransplant lymphoproliferative disorder in the esophagus.

Early manifestations of posttransplant lymphoproliferative disorders (PTLD) are mainly associated with a primary Epstein-Barr virus (EBV) infection. Rapid increases in peripheral blood EBV DNA load are supposed to reliably predict PTLD. We report a boy who 6 months after living-related kidney transplantation presented with an extranodal esophageal manifestation of PTLD. Despite a primary EBV infection with tonsillitis, the peripheral blood EBV DNA remained low, hiding the progression to PTLD.

Multi-exon deletions of the PKHD1 gene cause autosomal recessive polycystic kidney disease (ARPKD).

BACKGROUND: Autosomal recessive polycystic kidney disease (ARPKD) is caused by mutations in the PKHD1 (polycystic kidney and hepatic disease 1) gene on chromosome 6p12, a large gene spanning 470 kb of genomic DNA. So far, only micromutations in the 66 exons encoding the longest open reading frame (ORF) have been described, and account for about 80% of mutations. OBJECTIVE: To test the hypothesis that gross genomic rearrangements and mutations in alternatively spliced exons contribute to a subset of the remaining disease alleles. METHODS: Using DHPLC for alternatively spliced exons and quantitative real time polymerase chain reaction to detect genomic imbalances, 58 ARPKD patients were screened, of whom 55 were known to harbour one PKHD1 point mutation in the longest ORF. RESULTS: Three different heterozygous PKHD1 deletions and several single nucleotide changes in alternatively spliced exons were identified. The detected partial gene deletions are most likely pathogenic, while a potential biological function of the alterations identified in alternatively spliced exons must await the definition of transcripts containing alternative exons and their predicted reading frames. CONCLUSIONS: Gross PKHD1 deletions account for a detectable proportion of ARPKD cases. Screening for major genomic PKHD1 rearrangements will further improve mutation analysis in ARPKD.

Oral L-arginine supplementation in cystic fibrosis patients: a placebo-controlled study.

Exhaled nitric oxide (eNO) is decreased in cystic fibrosis (CF). The effect of oral L-arginine, the precursor of enzymatic nitric oxide (NO) formation, on airway NO in patients with CF was studied. In a pilot study, oral L-arginine was given in a single dose of 200 mg x kg(-1) body weight to eight healthy controls and eight CF patients. Subsequently, the same L-arginine dose was given to 10 patients with CF (five females) t.i.d. for 6 weeks in a randomised double-blind placebo-controlled crossover study. A single dose of oral L-arginine resulted in a 5.5-fold increase of L-arginine in plasma and a 1.3-fold increase of L-arginine in sputum after 2 h. Maximum eNO, within 3 h of L-arginine intake, increased significantly in both CF patients (5.4+/-2.1 ppb versus 8.3+/-3.5 ppb) and controls (18.0+/-8.1 ppb versus 26.4+/-12.3 ppb). Supplementation of L-arginine for 6 weeks resulted in a sustained increase in eNO compared to placebo (9.7+/-5.7 ppb versus 6.3+/-3.1 ppb). An effect of L-arginine supplementation on forced expiratory volume in one second was not observed. These data indicate that airway nitric oxide formation in cystic fibrosis patients can be augmented with oral L-arginine supplementation.

Search for mutations in SLC1A5 (19q13) in cystinuria patients.

To elucidate whether SLC1A5 is involved in the aetiology of cystinuria, we screened two non-type I cystinuria families without detectable mutations inSLC7A9 (and SLC3A1) but compatible with linkage to 19q13 for genomic variants in SLC1A5. Despite evidence for an involvement of SLC1A5 in the aetiology of cystinuria, we could not identify any mutation in this gene in the two families. With SLC1A5, a further candidate gene for cystinuria can be excluded as being involved in the pathogenesis of this disease in these two families. Of course, there remains the possibility that other genes are involved in cystinuria; further molecular studies will clarify the complex nature of this disorder.

Pathomechanisms and the diagnosis of arterial hypertension in pediatric renal allograft recipients.

Arterial hypertension is common in pediatric renal allograft recipients. While the causes are multifactorial, including chronic graft rejection, immunosuppressive therapy, and renal vascular disorders, the effect of hypertension on renal allograft function is detrimental. As in adults, if not treated early and aggressively, hypertension may lead to cardiovascular damage and graft failure. Pathophysiological changes in the arteries and kidney af-ter renal transplantation and the impact of receptor regulation have not been studied extensively in children. For identifying children with hypertension following renal transplantation casual blood pressure measurements do not accurately reflect average arterial blood pressure and circadian blood pressure rhythm. Ambulatory 24-h blood pressure monitoring should regularly be applied in trans-plant patients. The purpose of this review is to analyze pathophysiological aspects of risk factors for arterial hypertension and underline the importance of regular blood pressure monitoring and early therapeutic intervention.

Medical and surgical aspects of pediatric renal transplantation using living donors.

The outcomes of 19 consecutive living-donor renal transplants (LD-RTx) was compared with 41 cadaveric grafts (CD-RTx) performed at our institution using basiliximab, cyclosporine, and prednisone as standard immunosuppression. LD-RTx significantly shortened the waiting time on dialysis. However, patient survival (100% in both groups), 1-year graft survival (94.7% vs 90%), and rejection-free graft survival (76.9% vs 73.5%) was not significantly different. LD-RTx showed better glomerular filtration rates in the early phase after transplantation, a difference that faded with time. Graft function was similar after 1 and 2 years. LD grafts with double renal arteries were used successfully in four cases; heparin therapy was administered to avoid graft thrombosis. A significantly greater number of lymphoceles was observed with LD grafts (7/19 vs 1/41, P < .01). In conclusion with improved immunosuppression producing better results with CD grafts, the advantages of LD-RTx have vanished. LD grafts with double arteries may be used successfully and LD-RTx allows a shorter dialysis period. The high incidence of lymphoceles in our series awaits further evaluation.

The impact of cyclosporine on the development of immunosuppressive therapy--pediatric transplantation using cyclosporine.

Cyclosporine A (CsA) was introduced to pediatric renal transplantation more than 20 years ago, and it has greatly improved graft survival and made transplantation the treatment of choice for children with end-stage renal failure. Exposure to CsA was shown to be highly variable among transplant recipients. Therefore, major efforts have been employed to monitor CsA blood levels. The widely used trough levels had never been formally validated, and every center had defined its own target values. With the advanced microemulsion formula of CsA, drug exposure became more predictable, but scientifically evaluated monitoring concepts are still lacking. Monitoring the absorption phase using single time points (eg, 2 hours after ingestion) is promising, as shown in adult trials. In pediatric transplant recipients, randomized clinical trials have to be implemented urgently to fully exploit the potential of CsA in the prevention of graft rejection while minimizing toxicity. Although newer immunosuppressive drugs have been developed, further studies should be undertaken to define the role of CsA in combination protocols.

Genetic variations of the SLC7A9 gene: allele distribution of 13 polymorphic sites in German cystinuria patients and controls.

Cystinuria is a hereditary disorder of cystine and dibasic amino acid transport across the luminal membrane of renal tubules and intestine, resulting in recurrent nephrolithiasis. While mutations in the SLC3A1 gene cause type I cystinuria, patients with non-type I cystinuria carry mutations in the SLC7A9 gene. Both gene products form the renal amino acid transporter rBAT/b0,+AT affected in cystinuria. In the present study a total of 59 patients with different ethnic background were screened for sequence variations in SLC7A9, out of these 32 were of German origin. For determination of allele frequencies of detected polymorphisms, 58 healthy German controls were investigated. Molecular-genetic analysis was performed using single-strand conformation polymorphism analysis, restriction assays and sequencing. Allele frequencies were analyzed statistically for the detected polymorphisms. In addition to the 6 already known variants we identified 7 new polymorphisms. Statistical analyses showed a significantly different distribution of alleles between German patients and German controls in case of the polymorphisms c. 147C>T (exon 2), c.386C>T (exon 3), IVS3+22T>G, c.584C>T (exon 4), c.610T>C (exon 4), c.692C>T (exon 5), c.852C>A (exon 6) and c.872C>T (exon 6). In summary, our results show that cystinuria is a complex disease which is not only caused by mutations in SLC7A9 and SLC3A1, but also influenced by other modifying factors such as variants in SLC7A9.

Efficacy and tolerability of interleukin-2 receptor blockade with basiliximab in pediatric renal transplant recipients.

Rejection remains a major threat in pediatric renal transplantation (Tx), causing graft failure and increased exposure to drugs. The new chimeric antibody, basiliximab, directed against the alpha-chain of the interleukin-2 receptor (IL-2R), has been shown to be effective in preventing rejection episodes in adult renal transplant recipients. In our single-center experience from Essen, Germany, we evaluated prospectively the efficacy and tolerability of basiliximab, in combination with cyclosporin A (CsA) and prednisone, in 38 unselected pediatric patients. Mean patient age at Tx was 10.1 yr. Twenty-eight children received a cadaveric organ and 10 children received living-related donor grafts. The 1-yr patient survival rate was 100% and the 1-yr graft survival rate was 95% (36/38 patients). No graft was lost as a result of immunological factors, and single rejection episodes were observed in eight patients (21%). Two of these rejections were steroid-resistant and responded to tacrolimus rescue therapy. The rate of infections was not enhanced; overt cytomegalovirus (CMV) disease was observed in two patients only. Malignancies have not been seen to date. The blockade of the alpha-chain of the IL-2R lasted for up to 6 weeks. We conclude that the addition of basiliximab to standard immunosuppression in pediatric renal transplant recipients is well tolerated and results in a low incidence of rejection. The simple mode of application and the lack of side-effects make basiliximab an especially useful adjunct in pediatric patients.

Renal polyamine excretion, tubular amino acid reabsorption and molecular genetics in cystinuria.

Cystinuria is an autosomal recessive disorder of the tubular and intestinal resorption of cystine, ornithine. lysine and arginine leading to nephrolithiasis. Three cystinuria types can be distinguished by the mode of inheritance (true recessive or intermediate) and by the pattern of the intestinal amino acid transport. In the present study phenotypes were assessed by the urinary excretion of amino acids related to creatinine, the percentage tubular amino acid reabsorption and the urinary excretion of polyamines as a possible indicator of the intestinal transport defect. However, our thorough phenotyping did not reveal more than two cystinuria types. Genotypes were examined in linkage analyses and single-strand conformation polymorphism-based mutation identification. The SLC3A1 mutations M467T and T216M were disease causing in our homozygous patients of type I cystinuria. We can show the association of type I cystinuria with SLC3A1 and of non-type I cystinuria with a yet unidentified gene on chromosome 19q13.1. Our phenotype and genotype analyses provide evidence for only two types of cystinuria in the investigated patient cohort.

Distal myopathy in nephropathic cystinosis.

In long-standing nephropathic cystinosis complications are observed in various organs. Distal myopathy was first described in detail in 1994. The prevalence was calculated to be 24%. We studied seven patients with nephropathic cystinosis with neurophysiological techniques. Only two patients complained of a distal muscle weakness but all showed signs of myopathy on electromyography, which was more pronounced in the distal muscles. Motor and sensory nerve conduction parameters were within normal ranges. One patient with the juvenile form of nephropathic cystinosis also had myopathy. We conclude that distal myopathy can be detected in nephropathic cystinosis even in the absence of clinically overt muscle weakness. Cystine-depleting therapy with cysteamine is recommended for all patients with cystinosis, even after renal transplantation, and the effect on the myopathy should be studied.

Color Doppler energy--a new technique to study tissue perfusion in renal transplants.

Information on renal tissue perfusion after transplantation remains important for renal allograft monitoring. Findings obtained by conventional Doppler sonography are limited to vascular resistance (RI). The new technique color Doppler energy (CDE) is Doppler angle independent, omits flow velocity and direction, and is proportional to the returning signal strength. The aim of our study was to standardize the application of this technique and to analyze the information obtained. Forty-six CDE studies were performed with an Acuson 128XP in 28 children (mean age 12.4+/-5.3 years) between 4 days and 10 years after renal transplantation. The most-reproducible information was obtained with a 5-MHz linear probe and a constant area of 2x3 cm (log compression 40 dB, filter 3). CDE provided a high-resolution cross-sectional display of perfused cortical tissue vessels. According to the density of signals, the perfusion could be grouped into six perfusion scores (PS). The interobserver concordance was more than 85%. No correlation was found between PS and RI or blood pressure. However, there was a significant correlation between PS and glomerular filtration rate (r=-0.78, P<0. 001). These first results demonstrate a significant relationship between PS and chronic rejection. Non-rejection-related functional impairment exhibited no decrease in PS. We conclude that our proposed standardized CDE renal study is observer independent. CDE is a promising new technique that provides information on renal allograft dysfunction that is different from classical color Doppler findings. Further studies will clarify its role in renal transplant monitoring and its ability to replace more-invasive techniques.