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M Daudon

Publications and source records attributed to M Daudon.

At least 37 records · Page 2Linked to original sources
PubMed1999

Inhibitory effect of bikunin on calcium oxalate crystallization in vitro and urinary bikunin decrease in renal stone formers.

Two proteins of 17 and 24 kDa, respectively, which were immunologically related to bikunin, were purified from urine of healthy men, using in the last step a trypsin CNBr-sepharose affinity column. These proteins strongly inhibited calcium oxalate (CaOx) crystallization in two in vitro models. In the first model, the presence of 8 microg/ml protein in a medium containing 0.76 mM CaCl2 (with 45Ca) and 0.76 mM ammonium oxalate inhibited the crystallization process by 80%, as estimated by supernatant radioactivity after 60 min of incubation. A similar inhibition was observed in the second turbidimetric model, where the CaOx crystallization kinetics were followed for 10 min at 620 nm in a medium containing 4 mM CaCl2 and 0.5 mM Na2Ox. These proteins were used as standard protein for the development of an enzyme-linked immunosorbent assay (ELISA) in urine. Mean (+/-SEM) urinary bikunin concentration in 18 healthy subjects was 5.01 +/- 0.91 microg/ml. This was a concentration range of strong inhibitory activity in vitro. Bikunin values were nearly 50% lower (2.54 +/- 0.42 microg/ml, P=0.007) in 31 CaOx renal stone formers (having weddelite crystals in their first morning urine) than in the healthy volunteers. A correlation was found between urinary bikunin and alpha-1 microglobulin concentrations in the control group (y=0.73x + 1.09, r2=0.8) while no such correlation existed in the lithiasis group. In conclusion, bikunin exerts a strong inhibitory action of CaOx crystallization in vitro. Its involvement in urinary CaOx crystallization of stone formers is highly probable, based on the significant decrease in its urinary concentration in the majority of stone formers studied.

Adult↗
PubMed1999

Alpha-1-microglobulin: inhibitory effect on calcium oxalate crystallization in vitro and decreased urinary concentration in calcium oxalate stone formers.

In the past few years, alpha-1-microglobulin (alpha1m) has been copurified from human urine with bikunin, a potent inhibitor of calcium oxalate (CaOx) crystallization in vitro. In this study, we have purified alpha1m without bikunin contamination and investigated its possible role in CaOx crystallization by in vitro and in vivo studies. Alpha-1m was purified with an anti-alpha1m antibodies CNBr-activated sepharose column. Two molecular species of alpha1m of respectively 30 and 60 kDa were purified. For each protein, two blots of 30 and 60 kDa cross-reacted with anti-alpha1m antibodies, suggesting that these two forms were derived one from the other. Both protein species inhibited CaOx crystallization in a dose-dependent manner in two in vitro tests. In the first test, the presence of alpha1m of 30 kDa (8 microg/ml) in a medium containing 0. 76 mM CaCl(2) (with (45)Ca) and 0.76 mM Ox(NH(4))(2) inhibited CaOx crystallization by 38% as estimated by supernatant radioactivity after 1 h of agitation. In the second test, CaOx kinetics were examined for 3 to 10 min in a turbidimetric model at 620 nm. The presence of alpha1m of 30 kDa in a medium containing 4 mM CaCl(2) and 0.5 mM Na(2)Ox inhibited CaOx crystallization by 41.5%, as estimated by the slope modification of turbidimetric curve. Alpha-1m can be considered as another inhibitor of urinary CaOx crystal formation, as shown by the present in vitro studies. Using an ELISA assay, we found that urinary alpha1m concentration was significantly lower in 31 CaOx stone formers than in 18 healthy subjects (2.95 +/- 0.29 vs 5.34 +/- 1.08 mg/l respectively, P = 0.01). The decreased concentration of alpha1m in CaOx stone formers could be responsible in these patients, at least in part, for an increased risk of CaOx crystalluria.

Adolescent↗
PubMed1999

Urolithiasis in Tunisian children: a study of 120 cases based on stone composition.

The composition of urinary stones in children depends on socioeconomic conditions and hygiene, geographical area, and dietary habits. We analyzed urinary stones from 120 consecutive Tunisian children (81 males, 39 females) aged 5 months to 15 years. The stone was located in the upper urinary tract in 91 cases (76%). Stone analysis included both a morphological examination and an infrared analysis of the nucleus and the inner and peripheral layers. The main components of bladder calculi were whewellite (69%) and struvite (22%), whereas the main component of upper urinary tract calculi was whewellite (67%). The nucleus of bladder stones was composed of ammonium urate (45%), struvite (28%), cystine (10%), and carbapatite (7%). The nucleus of kidney and ureteral calculi was mainly composed of ammonium urate (38%), whewellite (24%), carbapatite (13%), or struvite (11%). Based on stone composition, urinary tract infection was involved in the nucleation or growth of a third of calculi. Endemic urolithiasis involving simultaneous nutritional, metabolic, and infectious factors, and defined by its nucleus composed of ammonium urate without struvite, represented 40% of cases. Exclusive metabolic factors - including genetic diseases such as primary hyperoxaluria, cystinuria, and hypercalciuria - were responsible for less than 25% of cases.

Adolescent↗
PubMed1999

Treatment of cystinuria.

Cystine urolithiasis is the only clinical expression of cystinuria, an autosomal recessive genetic defect of the transepithelial transport of cystine and other dibasic amino acids in the kidney. Stones form due to the increased excretion of cystine, which is poorly soluble at normal urine pH. Cystine stones are often resistant to extracorporeal shock wave lithotripsy, so that percutaneous surgery or ureteroscopy are the preferred techniques of stone extraction. Medical preventative treatment is based on high diuresis (>/=1.5 l/m(2) per day) well distributed throughout the day and night, and urine alkalinization up to pH 7.5 by means of sodium bicarbonate and/or potassium citrate. When these basal measures are ineffective at preventing stone recurrence or dissolving pre-existing stones, sulfhydryl agents such as D-penicillamine or tiopronin, which form highly soluble mixed disulfides with cystine moieties, are to be added to urine dilution and alkalinization, especially when cystine excretion is in excess of 750 mg/day (3 mmol/day). Frequent clinical and ultrasound follow-up is needed to encourage patient compliance and assess efficacy and tolerance of treatment.

Adult↗
PubMed1999

Nucleation of calcium oxalate crystals by albumin: involvement in the prevention of stone formation.

BACKGROUND: Urine is supersaturated in calcium oxalate, which means that it will contain calcium oxalate crystals that form spontaneously. Their size must be controlled to prevent retention in ducts and the eventual development of a lithiasis. This is achieved, in part, by specific inhibitors of crystal growth. We investigated whether promoters of crystal nucleation could also participate in that control, because for the same amount of salt that will precipitate from a supersaturated solution, increasing the number of crystals will decrease their average size and facilitate their elimination. METHODS: Albumin was purified from commercial sources and from the urine of healthy subjects or idiopathic calcium stone formers. Its aggregation properties were characterized by biophysical and biochemical techniques. Albumin was then either attached to several supports or left free in solution and incubated in a metastable solution of calcium oxalate. Kinetics of calcium oxalate crystallization were determined by turbidimetry. The nature and efficiency of nucleation were measured by examining the type and number of neoformed crystals. RESULTS: Albumin, one of the most abundant proteins in urine, was a powerful nucleator of calcium oxalate crystals in vitro, with the polymers being more active than monomers. In addition, nucleation by albumin apparently led exclusively to the formation of calcium oxalate dihydrate crystals, whereas calcium oxalate monohydrate crystals were formed in the absence of albumin. An analysis of calcium oxalate crystals in urine showed that the dihydrate form was present in healthy subjects and stone formers, whereas the monohydrate, which is thermodynamically more stable and constitutes the core of most calcium oxalate stones, was present in stone formers only. Finally, urinary albumin purified from healthy subjects contained significantly more polymers and was a stronger promoter of calcium oxalate nucleation than albumin from idiopathic calcium stone formers. CONCLUSIONS: Promotion by albumin of calcium oxalate crystallization with specific formation of the dihydrate form might be protective, because with rapid nucleation of small crystals, the saturation levels fall; thus, larger crystal formation and aggregation with subsequent stone formation may be prevented. We believe that albumin may be an important factor of urine stability.

Adult↗
PubMed1999

Crystalline phase differentiation in urinary calcium phosphate and magnesium phosphate calculi.

UNLABELLED: Phosphates are encountered as the main components in about 15% of urinary calculi. Except for struvite, no specific correlations have been found between the crystalline phase of the phosphates and the cause of nephrolithiasis. OBJECTIVE: The relationship between aetiological factors and crystalline phases or carbonate rate in calcium phosphate stones were assessed. MATERIAL AND METHODS: From a series of 1148 phosphate calculi, we investigated the relationship between composition and aetiological factors. RESULTS: Carbapatite was the most frequent crystalline phase (74.0%). It was associated with many possible causes, including hypercalciuria, hypocitraturia, primary hyperparathyroidism, tubular acidosis, medullary sponge kidney and chronic urinary tract infection. The carbonate rate of carbapatite may be of clinical interest because carbonate rates above 15% are frequently related to urinary tract infection with urea-splitting bacteria. Conversely, the carbonate rate was commonly less than 10% in cases of carbapatite induced by metabolic disorders. Among other phosphates, brushite was found in hypercalciuric states and primary hyperparathyroidism and whitlockite in cases of urinary tract infection by non-urease-producing bacteria. CONCLUSION: Identification of crystalline phases and measurement of carbonate rate in calcium phosphate calculi is of clinical interest for identifying stone aetiology.

Acidosis↗
PubMed1999

[Correlations between crystalluria and composition of calculi].

UNLABELLED: The successful fragmentation of kidney stones by means of extracorporeal shock wave lithotripsy partly depends on stone composition. In case of incomplete or coarse fragmentation, multiple urological procedures following ESWL may be necessary for removal of obstructive fragments. It is difficult to be sure that a given stone will be successfully destroyed. X-ray examinations before treatment are useful to classify calculi as calcium stones or not. Nevertheless, such investigations are often not sufficient to identify the main crystalline phases which form the stone and that can make it either resistant or friable to ESWL. OBJECTIVE: The aim of this study was to compare crystalluria and stone composition in patients with kidney calculi. MATERIAL AND METHODS: Seventy-five untreated patients (54 males, 21 females) were included. Their first morning urine was collected three days before surgical removal of the stone. Urine samples were kept at 4 degrees C during 48 hours before examination. RESULTS: Crystalluria occurred in 97.3% of urine specimens. Weddellite was the most frequent crystalline species found in urine (66.2%), followed by carbapatite (33.1%) and whewellite (23.1%). When compared to stone composition, crystalluria was mainly made of weddellite in urines from 68% of patients with weddellite-rich calculi. Stones from patients presenting with whewellite crystals in urine were mainly composed of whewellite in 88.9% of cases. Struvite stones were associated with struvite and carbapatite crystalluria in 85.7% of cases. CONCLUSION: Crystalluria studies could be of clinical interest to predict the main crystalline phase of calcium-containing stones in order to define the best procedures for stone removal.

Adult↗
PubMed1999

[Drug-induced urinary calculi in 1999].

Drug-induced urolithiasis are observed in 1.6% of the urinary calculi in France. Drugs crystals are identified in two thirds of these stones. Other drugs are responsible for stones which have an apparent metabolic origin (one third of the cases). Stone analysis using physical methods such as infrared spectroscopy is needed to unambiguously identify stones containing drugs. The inquiry is an important step to identify lithogenetic drugs which do not crystallize in the stones. The main substances which were identified in stones over the past decade were indinavir monohydrate (31.4%), triamterene (11.1%), sulphonamides (10.5%) and amorphous silica (4.5%). The main drugs involved in the nucleation and growth of metabolic stones were calcium and vitamin D supplementation (15%) and long-term treatment with carbonic anhydrase inhibitors (8%). Stone prevention is based on drug withdrawal or change in dosage with additional measures including an increase of diuresis and, if necessary, changes in the urine pH.

Acetazolamide↗
PubMed1998

A stable animal model of diet-induced calcium oxalate crystalluria.

Twenty male Wistar rats, weighing 150 g, were placed in metabolic cages on a 30% sucrose diet for 7 days, before allocation to two groups: a control group (n = 5) and a lactose group (n = 15). They received respectively a 30% sucrose diet or a 30% lactose diet for 8 weeks, each containing 0.67% calcium and 0.38% phosphorus. After 4 (T1) and 8 (T2) weeks, the serum calcium (Ca) and citrate levels were significantly (P < 0.01) higher in rats fed the lactose diet. Serum alkaline phosphatase activity was increased in the lactose group (P < 0.01) at T1 and T2. The lactose-rich diet induced an increase in urinary Ca excretion at T1 and T2; citrate excretion was only enhanced at T2 (P < 0.001). No difference between the two groups was observed in urinary oxalate (Ox) excretion or creatinine clearance. Crystalluria analysis revealed a marked number (>300/mm3 at T1 and T2) of calcium oxalate dihydrate crystals (COD) in rats fed the lactose-rich diet, whereas no COD crystals were observed in sucrose-fed control rats at any time point. The formation of COD crystals in lactose-fed rats was related to an increase in calcium oxalate (CaOx) product (pCaOx), which was respectively 12.6 vs 3.9 at T1 and 10.5 vs 1.8 at T2, and an increase in CaOx ratio (Ca/Ox), which was 99.1 vs 7.5 and 67.5 vs 18.5 at T1 and T2, respectively. The high pCaOx and Ca/Ox ratios in the lactose group were due to hypercalciuria, in agreement with the number and the type of crystals. The present experimental model confirms that the ingestion of a 30% lactose diet increases urinary Ca excretion without changing urinary Ox excretion and shows for the first time that it induces a stable and marked crystalluria composed of COD. Such a non-nephrotoxic and stable model is of interest for the study of CaOx crystal formation secondary to hypercalciuria, and thus afterwards eventually for CaOx nephrolithiasis.

Animals↗
PubMed1998

Infrared spectroscopy in the evaluation of the process of calcification of valvular bioprostheses.

BACKGROUND: The methods currently used to analyze the process of calcification of bioprostheses give only global information on calcium deposition. We investigated the potential advantage of infrared spectroscopy, which makes it possible to analyze the various components of the calcification process, ie, lipids, proteins, and calcium deposits. METHODS: Sixty porcine aortic leaflets were fixed in 0.6% glutaraldehyde and then subsequently implanted in 10-day-old Wistar rats. The valve leaflets were removed 2, 7, 14, 21, 35, and 56 days after implantation. RESULTS: Before implantation infrared spectroscopic analysis revealed the presence of proteins only. On day 2 after implantation, all valves showed minor lipid deposits. On day 7, amorphous calcium phosphate was detected. Between days 7 and 14, crystalline forms of calcium phosphate appeared and amorphous calcium phosphate progressively changed into carbapatite over the 56-day period. CONCLUSIONS: Infrared spectroscopy yields valuable additional information on the nature and kinetics of the various components of glutaraldehyde-treated tissues after implantation. It may prove to be important in the evaluation of new techniques of calcium mitigation.

Animals↗
PubMed1998

Crystalluria: a clinically useful investigation in children with primary hyperoxaluria post-transplantation.

Primary hyperoxaluria type I (PH I) is a congenital error of metabolism that can be manifested by an increased oxalate production, and ultimately result in kidney failure. After a combined liver/kidney transplantation, children with PH I have persistent excretion of oxalate that causes crystal formation in the urinary tract, and could result in systemic oxalosis and eventual graft failure. We speculated that crystalluria may be predictive of this nephrolithogenic tendency and thus investigated the effect of an intensive therapeutic strategy to prevent crystal formation in 13 children at our hospital. Oxalate crystal volume (OCV) measurements were performed at regular intervals for 36 months, and compared with urine supersaturation measurements. We found that crystalluria with the OCV measurement is non-invasive, easily performed, and gives feedback on the efficacy of PH I therapy within one hour. Further study is needed to determine whether this method is a better predictor of nephrocalcinosis than is supersaturation alone.

Adolescent↗
PubMed1998

Identification of crystals in kidneys of AIDS patients treated with foscarnet.

Three acquired immune deficiency syndrome patients given foscarnet to treat cytomegalovirus retinitis developed renal failure with crystal deposits within the renal glomeruli. We identified these crystals as a mixture of sodium salt, calcium salt, and a mixed salt containing both sodium and calcium ions. This composition has not been previously reported. Foscarnet can complex available ionized calcium and secondarily precipitate in glomeruli. The percentage of complexing depends on calcium concentration in serum and the poor calcium salt solubility.

AIDS-Related Opportunistic Infections↗
PubMed1997

[Urinary calculi and crystalluria in HIV+ patients treated with indinavir sulfate].

OBJECTIVES: Anti-proteases, a new class of anti-HIV drugs used in combination with reverse transcriptase inhibitors have led to spectacular improvement in the patients' clinical status. Since April 1996, indinavir is the most widely prescribed anti-protease in France. PATIENTS AND METHODS: From July 1996 to July 1997, we analyzed 46 spontaneously expulsed stones in 45 HIV+ patients (35 men and 10 women; age range 25 to 64 years) given indinavir in combination with other drugs since one week to ten months. Only six patients were known to have a past history of renal lithiasis. RESULTS: Forty-one calculi contained indinavir monohydrate (INDM) identified by mass spectrometry and infrared spectrophotometry. INDM was the only component excepting proteins in 39/45 calculi. In the 12 others, other compounds were also identified. Among the 114 urine samples collected 2 to 3 hours after an 800 mg dose of indinavir, 38 (33%) monohydrate indinavir crystals, identified by infrared microscopy. Mean urinary pH was significantly higher than in samples without INDM crystals (6.53 +/- 0.68 versus 5.96 +/- 0.71, p < 0.001). CONCLUSION: Two measures could possibly reduce the risk of crystalization: administration of urine acidifiers and increased fluid intake to raise diuresis. Alkalinisation is not indicated. Long-term increased fluid intake should be preferred over acidification which could be reserved solely for the treatment of drug-induced lithiasis.

Adult↗
PubMed1997

[Urinary calculi in children: contribution of anamnesis, biological exploration and physical analysis of calculi to the etiological diagnosis].

BACKGROUND: It is always of importance to define the cause of urinary calculi disease in children to prevent recurrence and possible impairing of renal function. Nevertheless, etiology is not always easy to prove and must be deduced from both clinical and biological arguments. PATIENTS AND METHODS: The aim of this prospective study including 39 Tunisian children with urinary stones was to identify etiology and stone risk factors and detail the part of clinical and biological data and results of physical analysis of stones in determining the cause of the stone. RESULTS: In 31 cases among 39, clinical and biological data were not sufficient to identify clearly the stone etiology. When considering the structure and stone composition, the cause of the stone could be determined in 97.4% of the cases. An inherited disease was found responsible for the stone in 11 children, urinary tract infection in 13 cases, idiopathic hypercalciuria in nine cases and a nutritional deficiency disease in seven cases. In one case, polycystic kidney disease with metabolic risk factors could explain the stone process. No precise etiology was found in one case. Among infection stones, struvite stones could be related to urea-splitting bacteria while other calculi, containing whitlockite and protein matrix could be related to other micro-organisms. Earlier severe chronic diarrhoea episodes were noted in six among seven children presenting stones with a nucleus mainly composed of ammonium urate. CONCLUSION: Clinical data, biological data from both urine and blood of the patients and also the structure and composition of the stones are needed to identify the cause of urinary calculi. Such a procedure could provide the stone etiology in most cases.

Adolescent↗