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In the present study intermediate-density lipoproteins (IDL) and very-low-density lipoproteins (VLDL) composition, structure, and mass were analysed in fasting uraemic patients on continuous ambulatory peritoneal dialysis (CAPD) ( = 12) and on haemodialysis (HD) ( = 15), and in 15 healthy volunteers. All the groups were matched for sex, age, and time on dialysis. Both groups of patients had elevated very-low-density lipoprotein levels, CAPD patients four and HD group three times that of control. We found a fourfold and a twofold increase in the concentration of IDL cholesterol in the CAPD and HD group respectively when they were compared with the control group. Both groups of patients present an increased VLDL mass. The CAPD group showed a four-fold increase in IDL mass compared with the control group, which indicated a preponderance of large size and suggested that defective IDL clearance was involved. The IDL composition of the CAPD patients was significantly different from that of the HD patients: a twofold increase in IDL mass was observed in the CAPD patients if compared with HD patients. We report new data concerning the metabolism of triglyceride-rich lipoproteins in CAPD treated patients, which confirm the adverse effect of CAPD on serum lipids. [ABSTRACT FROM PUBLISHER]

Background: Cystinuria is a heritable disorder of amino acid transport characterized by the defective transport of cystine and the dibasic amino acids through the brush border epithelial cells of the renal tubule and intestine tract. Three types of cystinuria (I, II, and III) have been described based on the urinary excretion of cystine and dibasic amino acids in obligate heterozygotes. The SLC3A1 gene coding for an amino acid transporter named rBAT is responsible for type I cystinuria, whereas the SLC7A9 gene coding for a subunit (b0,+AT) of rBAT is involved in determining non-type I (types II and III) cystinuria.Methods: The SLC3A1 gene sequence was investigated in a sample of seven type I/type I, three type I/non-type I, six type I/untyped, and four untyped unrelated cystinuric patients by RNA single-strand conformation polymorphism (RNA-SSCP).Results: Eight new point mutations (S168X, 765+1G>T, 766-2A>G, R452Q, Y461X, S547W, L564F, and C673W) and seven previously reported mutations were detected. These new mutations increase the number of mutated alleles so far characterized in SLC3A1 to 62.Conclusions: We have found SLC3A1 mutations in 0.739 of the type I chromosomes studied. The relatively high proportion of uncharacterized type I chromosomes suggests either that there may be mutations not yet found in SLC3A1 or that many of the assigned type I chromosomes in mixed type I/non-type I patients may have mutations in SLC7A9. If the hypothesis is excluded in the future, we believe that a third gene may be involved in cystinuria. [ABSTRACT FROM AUTHOR]

Cystinuria is a common recessive disorder of renal reabsorption of cystine and dibasic amino acids that results in urolithiasis of cystine. Cystinuria is caused by defects in the amino acid transport system b0,+ (i.e. the rBAT/b0,+AT heteromeric complex). Mutations in SLC3A1, encoding rBAT, cause cystinuria type A, characterized by a silent phenotype in heterozygotes (phenotype I). Mutations in SLC7A9, encoding b0,+AT, cause cystinuria type B, in which heterozygotes in most cases hyperexcrete cystine and dibasic amino acids (phenotype non-I). To facilitate in vivo investigation of b0,+AT in cystinuria, Slc7a9 knockout mice have been generated. Expression of b0,+AT protein is completely abolished in the kidney of Slc7a9-/- mice ('Stones'). In contrast, Stones expressed significant amounts of rBAT protein, which is covalently linked to unidentified light subunit(s). Stones mice present a dramatic hyperexcretion of cystine and dibasic amino acids, while Slc7a9+/- mice show moderate but significant hyperexcretion of these amino acids (phenotype non-I). Forty-two per cent of Stones mice develop cystine calculi in the urinary system. Calculi develop during the first month of life and grow throughout the life span of the animals. Histopathology in kidney reveals typical changes for urolithiasis (tubular and pelvic dilatation, tubular necrosis, tubular hyaline droplets and chronic interstitial nephritis). The fact that some Stones mice, generated in a mixed genetic background, develop cystine calculi from an early age, while others do not develop them in their first year of life, suggests the involvement of modifier genes in the lithiasis phenotype. Thus, Stones provide a valid model of cystinuria which can be used in the study of genetic, pharmacological and environmental factors involved in cystine urolithiasis.

Recent developments in the genetics and physiology of cystinuria do not support the traditional classification, which is based on the excretion of cystine and dibasic amino acids in obligate heterozygotes. Mutations of only two genes (SLC3A1 and SLC7A9), identified by the International Cystinuria Consortium (ICC), have been found to be responsible for all three types of the disease. The ICC set up a multinational database and collected genetic and clinical data from 224 patients affected by cystinuria, 125 with full genotype definition. Amino acid urinary excretion patterns of 189 heterozygotes with genetic definition and of 83 healthy controls were also included. All SLC3A1 carriers and 14% of SLC7A9 carriers showed a normal amino acid urinary pattern (i.e., type I phenotype). The rest of the SLC7A9 carriers showed phenotype non-I (type III, 80.5%; type II, 5.5%). This makes the traditional classification imprecise. A new classification is needed: type A, due to two mutations of SLC3A1 (rBAT) on chromosome 2 (45.2% in our database); type B, due to two mutations of SLC7A9 on chromosome 19 (53.2% in this series); and a possible third type, AB (1.6%), with one mutation on each of the above-mentioned genes. Clinical data show that cystinuria is more severe in males than in females. The two types of cystinuria (A and B) had a similar outcome in this retrospective study, but the effect of the treatment could not be analyzed. Stone events do not correlate with amino acid urinary excretion. Renal function was clearly impaired in 17% of the patients.

Mutations in the rBAT and b(0,+)AT genes cause type I and non-type I cystinuria, respectively. The disulfide-linked rBAT-b(0,+)AT heterodimer mediates high-affinity transport of cystine and dibasic amino acids (b(0,+)-like activity) in heterologous cell systems. However, the significance of this heterodimer for cystine reabsorption is unknown, as direct evidence for such a complex in vivo is lacking and the expression patterns of rBAT and b(0,+)AT along the proximal tubule are opposite. We addressed this issue by biochemical means. Western blot analysis of mouse and human kidney brush-border membranes showed that rBAT and b(0,+)AT were solely expressed as heterodimers of identical size and that both proteins coprecipitated. Moreover, quantitative immunopurification of b(0,+)AT followed by SDS-PAGE and mass spectrometry analysis established that b(0,+)AT heterodimerizes exclusively with rBAT. Together with cystine reabsorption data, our results demonstrate that a decreasing expression gradient of heterodimeric rBAT-b(0,+)AT along the proximal tubule is responsible for virtually all apical cystine reabsorption. As a corollary of the above, there should be an excess of rBAT expression over that of b(0,+)AT protein in the kidney. Indeed, complete immunodepletion of b(0,+)AT did not coprecipitate >20-30% of rBAT. Therefore, another rBAT-associated subunit may be present in latter parts of the proximal tubule.

Objective: Although residual lithiasis after the application of shock waves is a situation that coexists with the procedure, in some cases it can be considered to be a failure of ESWL. The natural history and outcome of 244 cases of residual renal stone followed over a 5-year period are analyzed, and the approach based on a pre-established classification is discussed., Methods: Of 1,407 patients treated by ESWL for renal lithiasis during 1995, 244 cases with a renal calculus larger than 3 mm were followed for a period of 5 years after treatment and evaluated by clinical, radiological, ultrasound and analytical methods., Results: At 3 months post-ESWL, 1,013 cases (72%) were completely stone-free and 394 (28%) showed residual stone; of these, 244 (62%) had residual stone fragments greater than 3 mm. At 5 years, 190 (78%) remained stable and the remaining 54 (22%) showed stone regrowth that warranted additional treatments: 52 ESWL, 1 PNL and 1 partial nephrectomy. Despite the retreatments, only 42% became completely stone-free., Conclusions: A classification of residual renal stone can be established based on the data obtained to orient the approach in each case, although the frequency of residual stone can be reduced by the appropriate indication of ESWL. Once a renal stone has formed retreatments with ESWL cannot ensure complete elimination of the stone.

Objective: Cystine renal stone is the only clinical consequence of cystinuria, an autosomal recessive hereditary disease that affects an average of 1 out of 7,000 newborns, and whose geographical distribution varies significantly. The diagnosis and treatment of this condition is reviewed in the light of the advances in genetics and molecular biology., Methods: The evolution of current knowledge about this disease is reviewed., Results/conclusions: The advances over the last 8 years have led to the characterization, at the present time, of two genes responsible for this disease, which demonstrates its polygenic origin. By phenotype, cystinuria can be classified into two types: type 1 and non-type 1. Both types show genetic and biochemical, but not clinical differences. From the therapeutic viewpoint, the main objective is to eliminate existing calculi and, above all, prevent recurrence by acting on the pathophysiologic mechanisms of renal cystine. Experience shows that despite the correct use of our current therapeutic armamentarium and the application of the general guidelines discussed in this paper, some cystinuric patients still maintain an important stone-forming activity. Patient clinical evaluation and a genetic study of both patient and family will be decisive for phenotyping.

Cystinuria (MIM 220100) is a common recessive disorder of renal reabsorption of cystine and dibasic amino acids. Mutations in SLC3A1, encoding rBAT, cause cystinuria type I (ref. 1), but not other types of cystinuria (ref. 2). A gene whose mutation causes non-type I cystinuria has been mapped by linkage analysis to 19q12-13.1 (Refs 3,4). We have identified a new transcript, encoding a protein (bo, +AT, for bo,+ amino acid transporter) belonging to a family of light subunits of amino acid transporters, expressed in kidney, liver, small intestine and placenta, and localized its gene (SLC7A9) to the non-type I cystinuria 19q locus. Co-transfection of bo,+AT and rBAT brings the latter to the plasma membrane, and results in the uptake of L-arginine in COS cells. We have found SLC7A9 mutations in Libyan-Jews, North American, Italian and Spanish non-type I cystinuria patients. The Libyan Jewish patients are homozygous for a founder missense mutation (V170M) that abolishes b o,+AT amino-acid uptake activity when co-transfected with rBAT in COS cells. We identified four missense mutations (G105R, A182T, G195R and G295R) and two frameshift (520insT and 596delTG) mutations in other patients. Our data establish that mutations in SLC7A9 cause non-type I cystinuria, and suggest that bo,+AT is the light subunit of rBAT.

Background: The use of preoperative imaging in patients with hyperparathyroidism remains controversial. The aim of this study is to assess the usefulness of the double-phase 99mTc-sestamibi scintigraphy in the diagnosis of abnormal parathyroid glands in patients with primary hyperparathyroidism., Patients and Methods: We studied 60 patients presenting with primary hyperparathyroidism who were referred to surgery; four of them had been unsuccessfully operated. 99mTc-sestamibi scintigraphy were performed in all patients previously to surgery. Scintigraphic technique: planar imaging of the neck and thorax was done in the anterior view at 15 and 150 min postinjection of 740 MBq (20 mCi) of 99mTc-sestamibi., Results: Surgery found 57 adenomas (2.59 [SD, 5.84] g; range 0.160-40), 6 hyperplastic glands (0.34 [SD, 0.26] g) and one carcinoma 8.2 g. The 99mTc-sestamibi was able to localize correctly 60 out of 64 lesions (55/57 adenomas, 4/6 hyperplastic glands and 1/1 carcinoma) (global sensitivity of 94%, adenomas sensitivity of 96%, positive predictive value of 97% and specificity of 98%). Isotopic imaging detected the abnormal tissue in all patients who had undergone unsuccessful previous surgery. PTH (4 [SD, 1.51] pmol/l) and calcium postoperative serum levels (2.13 [SD, 0.22] mmol/l) showed curation of all patients., Conclusion: Double phase parathyroid scintigraphy with 99mTc-sestamibi is the method of choice to localize abnormal parathyroid glands.

Cystinuria is an autosomal recessive amino-aciduria where three urinary phenotypes have been described (I, II, and III). An amino acid transporter gene, SLC3A1 (formerly rBAT), was found to be responsible for this disorder. To assess whether mutations in SLC3A1 are involved in different cystinuria phenotypes, linkage with this gene and its nearest marker (D2S119) was analyzed in 22 families with type I and/or type III cystinuria. Linkage with heterogeneity was proved (alpha = 0.45; P < 0.008). Type I/I families showed homogeneous linkage to SLC3A1 (Zmax > 3.0 at theta = 0.00; alpha = 1), whereas types I/III and III/III were not linked. Our data suggest that type I cystinuria is due to mutations in the SLC3A1 gene, whereas another locus is responsible for type III. This result establishes genetic heterogeneity for cystinuria, classically considered as a multiallelic monogenic disease.

A cystinuria disease gene (rBAT) has been recently identified, and some mutations causing the disease have been described. The frequency of these mutations has been investigated in a large sample of 51 Italian and Spanish cystinuric patients. In addition, to identify new mutated alleles, genomic DNA has been analyzed by an accurate and sensitive method able to detect nucleotide changes. Because of the lack of information available on the genomic structure of rBAT gene, the study was carried out using the sequence data so far obtained by us. More than 70% of the entire coding sequence and 8 intron-exon boundaries have been analyzed. Four new mutations and seven intragenic polymorphisms have been detected. All mutations so far identified in rBAT belong only to cystinuria type I alleles, accounting for approximately 44% of all type I cystinuric chromosomes. Mutation M467T is the most common mutated allele in the Italian and Spanish populations. After analysis of 70% of the rBAT coding region, we have detected normal sequences in cystinuria type II and type III chromosomes. The presence of rBAT mutated alleles only in type I chromosomes of homozygous (type I/I) and heterozygous (type I/III) patients provides evidence for genetic heterogeneity where rBAT would be responsible only for type I cystinuria and suggests a complementation mechanism to explain the intermediate type I/type III phenotype.

Cystinuria is an amino acid disease due to a defect of intestinal and renal tubular transport of cystine and various basic amino acids (lysine, arginine and ornithine). The disease is transmitted horizontally according to an autosomal recessive pattern. The overall prevalence is one per 7,000 live births. It is the commonest hereditary disease affecting amino acid transport (MIM 220100). This disease is characterized by excessive urinary excretion of cystine and basic amino acids. From a clinical point of view, almost 50% of homozygotes will develop cystine renal stones with urinary tract infection, renal colic, partial or total obstruction of the urinary tract and possibly loss of renal function.

Cystinuria is a classic heritable aminoaciduria that involves the defective transepithelial transport of cystine and dibasic amino acids in the kidney and intestine. Six missense mutations in the human rBAT gene, which is involved in high-affinity transport of cystine and dibasic amino acids in kidney and intestine, segregate with cystinuria. These mutations account for 30% of the cystinuria chromosomes studied. Homozygosity for the most common mutation (M467T) was detected in three cystinuric siblings. Mutation M467T nearly abolished the amino acid transport activity induced by rBAT in Xenopus oocytes. These results establish rBAT as a cystinuria gene.