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Biomedical subjects

A Bökenkamp

Publications and source records attributed to A Bökenkamp.

At least 19 recordsLinked to original sources
PubMed2005

[Schimke's immuno-osseous dysplasia as an explanation for the rare combination of disproportionately short stature and the nephrotic syndrome].

A 10-year-old Turkish boy with consanguineous parents was presented with a disproportionately short stature and a nephrotic syndrome. The mild form of Schimke's immuno-osseous dysplasia was diagnosed as the common cause. This rare, autosomal recessive osteochondrodysplasia is characterised by spondyloepiphyseal dysplasia, facial dysmorphism, T-cell immunodeficiency and progressive renal failure due to focal segmental glomerulosclerosis. In Schimke's immuno-osseous dysplasia, a severe early-onset form and a milder later-onset form can be distinguished on the basis of the clinical course. The patient was treated by fluid and salt restriction, enalapril and later also losartan, which led to a decrease in the proteinuria and an increase in serum albumin concentration. Two years later, the renal function was still normal.

Body Height↗
PubMed2005

Long-term outcome of kidney function after twin-twin transfusion syndrome treated by intrauterine laser coagulation.

Twin-twin transfusion syndrome (TTTS) is caused by unbalanced shunting of blood between monochorionic twins. It is well known that chronic hypotension and hypovolemia may cause renal insufficiency in the donor twin. The long-term outcome of kidney function after TTTS has not previously been delineated in the literature, however. The aim of this study was to evaluate the long-term outcome of kidney function in children after intrauterine laser treatment for severe TTTS. Eighteen surviving twin pairs after intrauterine laser treatment for TTTS were involved in the study. Their gestational age at birth was 29-39 weeks, their median birth weight was 2050 g, and their median age at evaluation was 3 years 1 month, range 1 year 9 months to 4 years 5 months. Serum creatinine, cystatin C, and beta 2-microglobulin, sodium, potassium, and phosphate excretion, and urine albumin and alpha-1-microglobulin were measured. Creatinine clearance was calculated by use of the Schwartz formula. The laboratory findings for all 36 children were within normal limits. There were no significant differences between donors and recipients. Despite severe alteration of renal function before the laser treatment (anuria-polyuria) no long-term impairment of renal function could be detected in any of the 18 twin pairs.

Child Development↗
PubMed2003

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.

Alleles↗
PubMed2002

Complete virilization in congenital adrenal hyperplasia: clinical course, medical management and disease-related complications.

OBJECTIVE: In girls with congenital adrenal hyperplasia (CAH), genital ambiguity usually leads to a rapid neonatal diagnosis. Rarely, CAH causes complete virilization and male sex assignment with a delayed diagnosis. After being confronted with very specific problems in two of such patients, we collected data of patients with CAH and complete virilization in a nationwide study to delineate specific problems of these rare patients in order to improve their management. DESIGN AND PATIENTS: Through the German Working Group of Paediatric Endocrinology (Arbeitsgemeinschaft Pädiatrische Endokrinologie, APE), questionnaires were sent to all members caring for patients with CAH and complete virilization in their endocrine clinics. Data from 16 patients from 10 paediatric endocrine centres were assessed by questionnaire. RESULTS: The following problems have been encountered. (1) Sex assignment/gender identity: initially all patients had a male sex assignment. Six patients were diagnosed during the first month of life. Five were reassigned to female sex immediately, one at the age of 19 months. Except in one girl demonstrating some tomboyish behaviour, gender role behaviour in these patients did not differ from unaffected girls. Ten patients were diagnosed late at 3.4--7 years of age. In seven patients with a late diagnosis, male sex assignment was maintained; one of them expressed some concerns about living as a male. In three patients late sex reversal was performed, gender identity is very poor in one and new sex assignment is currently under consideration. (2) SURGERY: irrespective of the sex assigned, all patients had between one and three surgical procedures, including clitoris reduction and (repeated) vaginoplasties in patients with female sex assignment. Hysterectomy and ovarectomy were performed in patients with male sex assignment. (3) Short stature: patients with a late diagnosis of CAH had extremely advanced bone ages of +6.3 to +9.5 years, leading to severely reduced final height of 137 to 150 cm in adult patients. Patients tended to follow height percentiles of genetic females. One pubertal patient was suicidal due to short stature. (4) Central precocious puberty (CPP): prolonged exposition to adrenal androgens led to CPP in one patient. He was treated with GnRH analogues until gonadectomy. CONCLUSIONS: Patients with CAH and complete virilization have a high risk of being diagnosed late. There are major problems and uncertainties of the patients' families and the treating physicians concerning gender assignment. Gender identity is disturbed in some patients. In addition, multiple surgical procedures are necessary and short stature as well as central precocious puberty might be important to avoid late sequelae. While some surgical interventions are probably unavoidable, most of these issues could be resolved with an early diagnosis. Thus, especially for these patients, a neonatal screening programme for CAH would be of paramount importance.

Adolescent↗
PubMed2002

The beta2-microglobulin/cystatin C ratio--a potential marker of post-transplant lymphoproliferative disease.

BACKGROUND: As a consequence of more intensified immunosuppression, post-transplant lymphoproliferative disease (PTLD) is increasingly observed in patients after solid-organ transplantation. Beta2-microglobulin, a low-molecular weight protein (MW 11.8 kDa), is produced by all nucleated cells as part of the HLA complex. Its serum concentration is directly correlated with prognosis in patients with lymphatic neoplasms. Like other low-molecular weight proteins, beta2-microglobulin is eliminated by glomerular filtration. This complicates its use as a tumor marker in renal insufficiency. Cystatin C, a low-molecular weight protein of 13.3 kDa, is a new marker of kidney function largely unaffected by extrarenal disease. We, therefore, sought to assess the potential of the beta2-microglobulin/cystatin C ratio (beta2M/Cys) as a marker of lymphoproliferation. PATIENTS AND METHODS: Beta2M/Cys was determined by particle-enhanced immunonephelometry in sera from 132 children with different degrees of renal insufficiency, 5 of whom had lymphoproliferative disease. Renal function was assessed using the Schwartz formula. RESULTS: Beta2M/Cys was constant between 1.2 and 2.4 mg/mg for Schwartz GFR > or = 40 ml/min x 1.73 m2. With lower GFR, beta2M/Cys rose progressively, maximum values being found in the hemodialysis patients (4.85-11.73). Healthy renal transplant recipients had beta2M/Cys comparable to controls. With acute lymphoproliferative disease, all but one patient had significantly elevated beta2M/Cys between 2.68 and 3.68 mg/mg, which returned to normal in remission (1.67-2.35 mg/mg). The sensitivity of a beta2M/Cys ratio > 2.4 mg/mg for the detection of PTLD was 80%, the specificity 100%, positive predictive value 100%, negative predictive value 90%. CONCLUSION: The beta2-microglobulin/cystatin C ratio is a promising parameter of lymphoproliferation in patients with normal or mildly impaired renal function.

Biomarkers↗
PubMed2001

Perioperative management of central diabetes insipidus in kidney transplantation.

Central diabetes insipidus is clinically masked in dialysis patients. We report a 12-year-old girl receiving a living-related donor graft for renal failure from Alport syndrome, in whom a craniopharyngioma had been resected 6 months before transplantation. Pretransplant evaluation had documented central hypothyroidism, growth hormone deficiency, and presumptive hypogonadotropic hypogonadism. The corticotropin-releasing factor test had been normal. Four hours after transplantation, urine output exceeded 1,000 ml/h without diuretic therapy. Serum sodium concentration was 155 mmol/l, serum osmolality 333 mmol/kg, and plasma antidiuretic hormone 4.9 ng/l, while urine osmolality was 233 mmol/kg. Desmopressin acetate was started by continuous intravenous infusion at 1 microgram/day. Serum electrolytes rapidly normalized, urine output stabilized at 2 l/day. The patient was discharged 4 weeks after transplantation with good allograft function, receiving intranasal desmopressin acetate 10 micrograms twice daily. Pre-existing central diabetes insipidus is unmasked after successful kidney transplantation, leading to rapid dehydration and hypernatremia, which can be prevented by prompt institution of desmopressin therapy.

Child↗
PubMed2001

Fetal serum concentrations of cystatin C and beta2-microglobulin as predictors of postnatal kidney function.

OBJECTIVES: Cystatin C and beta(2)-microglobulin are established serum markers of renal function in children and adults. In contrast to creatinine, diaplacental exchange is minimal. The aim of the study was to establish reference values in fetal serum and to test their efficiency in predicting postnatal kidney function. STUDY DESIGN: This was a prospective noninterventional study measuring cystatin C and beta(2)-microglobulin by particle-enhanced immunoturbidimetry in excess serum from 129 cordocenteses performed in 84 fetuses. Reference intervals (mean +/- 1.96 SD) were calculated in a subgroup of 54 fetuses without evidence of kidney disease, and these reference values were evaluated in 75 sera from 55 fetuses. RESULTS: Mean cystatin C was 1.66 +/- 0.202 mg/L (upper limit 2.06), and mean beta(2)-microglobulin was 4.25 +/- 0.734 mg/L. Unlike cystatin C, beta(2)-microglobulin decreased significantly with gestational age so that the upper reference limit was 7.19-0.052 x gestational age in weeks. beta(2)-Microglobulin had higher sensitivity (90.0% vs 63.6%) and cystatin C a higher specificity (91.8% vs. 85.5%) for the prediction of impaired renal function; diagnostic efficiency was equal (87.6% vs. 86.1%). Fetuses with impaired renal function at birth or who were aborted for renal malformations had higher cystatin C concentrations than those in a control group. beta(2)-Microglobulin was increased only in fetuses who were aborted. CONCLUSION: Fetal serum cystatin C and beta(2)-microglobulin concentrations may be useful predictors of postnatal kidney function.

Cordocentesis↗
PubMed1999

Role of albumin and glomerular capillary wall charge distribution on glomerular permselectivity: studies on the perfused-fixed rat kidney model.

The charge-related determinants of albumin permeability are the subject of controversial discussion. To study this question we have developed an isolated perfused rat kidney model in which metabolic processes are eliminated by perfusion fixation with glutaraldehyde. The fixed kidneys were perfused with albumin solutions using the following approaches: 1. Modification of the charge of both the glomerular capillary wall (GCW) and albumin using different buffer systems in a pH range spanning the isoelectric points of albumin and the glomerular basement membrane (GBM), the extracellular matrix of the GCW. 2. Modification of the charge of the GCW by perfusing the isolated kidney with cations either before or after fixation. 3. Modification of the charge of albumin by cationization. In the model, the inulin "urine" to perfusate ratio was one. This shows that the tubules have no metabolic activity, that the glomerular filtration rate (GFR) is equal to "urine" flow rate and that the "urine" collected is identical to the ultrafiltrate. Therefore, sieving coefficients in this model can simply be calculated as the ratio between "urine" and perfusate protein concentrations. We could show that: 1. pH has a significant effect on the albumin sieving coefficient: it was maximally increased at pH 4.0 [(70.3 +/- 15.9) x 10(-3), n = 10 versus (8.7 +/- 3.7) x 10(-3), n = 11, at pH 7.4]. Only a pH as low as 4.0 should lead to a pronounced neutralization of the anionic charges of albumin and the GBM; the charge density of the GCW calculated with these data is 43 mEq/l at pH 7.4. 2. Modifying the ionic composition of the GCW with protamine before fixation with glutaraldehyde causes a bigger increase in the glomerular permeability for albumin [(51.2 +/- 22.5) x 10(-3), n = 10, glomerular charge density 21 mEq/l] than modifying the albumin charge by cationization. 3. Modifying the albumin charge by cationization increases the glomerular permeability for albumin [(20.0 +/- 6.7) x 10(-3), n = 8]. These findings support the hypothesis that at the onset of proteinuria changes in the charge and configuration of the GCW could be more important pathogenetic factors than changes in the charge of serum-derived proteins.

Animals↗
PubMed1999

Plasma calcium oxalate supersaturation in children with primary hyperoxaluria and end-stage renal failure.

BACKGROUND: Children with primary hyperoxaluria type 1 (PH 1) are at great risk to develop systemic oxalosis in end-stage renal disease (ESRD), as endogenous oxalate production exceeds oxalate removal by dialytic therapy. As oxalate accumulates, calcium oxalate (CaOx) tissue deposition occurs. Children with other causes of ESRD, however, are not prone to CaOx deposition despite elevated plasma oxalate (POx) levels. METHODS: Our study objective was to examine the potential mechanisms for these observations. We measured POx, sulfate, citrate, and calculated CaOx saturation (betaCaOx) in 7 children with ESRD caused by PH 1 and in 33 children with non-PH-related ESRD. Maintenance hemodialysis (HD) was performed in 6 PH 1 and 22 non-PH patients: Pre- and post-HD levels were analyzed at this point and were repeated twice within 12 months in 5 PH 1 and 14 non-PH patients. Samples were obtained only once in 12 patients (one PH 1) on peritoneal dialysis (PD). After liver-kidney or kidney transplantation, plasma levels were measured repetitively. RESULTS: The mean POx was higher in PH 1 (125.7 +/- 17.9 micromol/liter) than in non-PH patients (44.2 +/- 3.3 micromol/liter, P < 10(-4)). All other determined anions did not differ between the two groups. betaCaOx was higher in PH 1 (4.71 +/- 0.69 relative units) compared with non-PH children (1.56 +/- 0.12 units, P < 10(-4)). POx and betaCaOx were correlated in both the PH 1 (r = 0.98, P < 2 x 10(-4)) and the non-PH group (r = 0.98, P < 10(-4)). POx and betaCaOx remained stable over time in the non-PH children, whereas an insignificant decline was observed in PH 1 patients after six months of more aggressive dialysis. betaCaOx was supersaturated (more than 1) in all PH 1 and in 25 out of 33 non-PH patients. Post-HD betaCaOx remained more than 1 in all PH 1, but in only 2 out of 22 non-PH patients. In non-PH children, POx and betaCaOx decreased to normal within three weeks after successful kidney transplantation, whereas the levels still remained elevated seven months after combined liver-kidney transplantation in two PH 1 patients. CONCLUSION: Systemic oxalosis in PH 1 children with ESRD is due to higher POx and betaCaOx levels. As betaCaOx remained supersaturated in PH 1 even after aggressive HD, oxalate accumulation increases, and CaOx tissue deposition occurs. Therefore, sufficient reduction of POx and betaCaOx is crucial in PH 1 and might only be achieved by early, preemptive, combined liver-kidney transplantation or liver transplantation alone.

Bone and Bones↗
PubMed1999

Cystatin C and creatinine after successful kidney transplantation in children.

BACKGROUND: Serum creatinine is commonly used for the monitoring of allograft function following renal transplantation (RTX). Due to lower muscle mass, creatinine production rate is reduced in children, thus decreasing its sensitivity for the detection of allograft dysfunction. In children, the serum concentration of cystatin C, a low molecular weight protein of 13.3 kDa, reflects glomerular filtration rate independent of age, height and body composition. We, therefore, sought to assess the potential of cystatin C as a marker of allograft function in children. METHODS: Cystatin C and creatinine were measured in parallel at least daily in 24 children (14 boys, 10 girls; mean age 10.5+/-5.1 years) during hospitalization after successful RTX. Cystatin was determined immunoturbidimetrically, creatinine enzymatically. RESULTS: Within one hour after RTX, cystatin C (mean+/-SE) almost halved from 6.69+/-0.45 mg/l to 3.69+/-0.38 mg/l while creatinine declined from 862 +/-65.4 to 633+/-62.9 micromol/l. Following a nadir of 1.82+/-0.18 mg/l on day 2, there was a secondary increase in cystatin C concentrations to 2.69+/-0.35 mg/l on day 10. Creatinine concentrations continued to decline until day 9 reaching 80.5+/-13.1 micromol/l. Day-to-day variation at steady-state was comparable. In the course of 9 acute rejection episodes, both parameters rose in parallel, the increase in creatinine concentration being much greater. CONCLUSION: Cystatin C was an early indicator of allograft function following successful RTX in children. It did not prove superior to creatinine for the recognition of acute allograft dysfunction, however.

Biomarkers↗
PubMed1998

Reference values for cystatin C serum concentrations in children.

Cystatin C, a low molecular weight protein, is a new endogenous marker of renal function whose serum concentration correlates better with glomerular filtration rate than creatinine. The aim of the present study was to define a reference interval for cystatin C concentrations in children. Cystatin C was measured by an immunoturbidimetric assay in sera obtained from 258 children (93 girls, 165 boys, median age 6.29 years, range 1 day to 18 years) without evidence of kidney disease. The reference interval was calculated non-parametrically using the 2.5th and 97.5th percentiles. For comparison, creatinine was measured in the same samples. The cystatin C concentration was highest on the first days of life (range 1.64-2.59 mg/l) with a rapid decrease during the first 4 months. Beyond the 1st year, the cystatin C concentration was constant, with a reference interval of 0.7-1.38 mg/l. In contrast, serum creatinine concentrations steadily increased with age until adulthood. Compared with creatinine, cystatin C facilitates the recognition of abnormal renal function in children as its reference range is constant beyond the 1st year of life. The higher levels of cystatin C in the 1st year of life probably reflect the low glomerular filtration rate of neonates and infants.

Adolescent↗
PubMed1998

Plasma calcium-oxalate saturation in children with renal insufficiency and in children with primary hyperoxaluria.

BACKGROUND: Calcium-oxalate (CaOx) deposition and systemic oxalosis are uncommon in children with chronic renal failure (CRI), but frequent in children with primary hyperoxaluria type I (PH-1). We hypothesized a difference in plasma CaOx saturation (betaCaOx) and its determining factors would explain this discrepancy. METHODS: Therefore, in addition to common biochemical measurements, plasma-oxalate (POx), citrate (PCit) and sulfate (PSulf) (plasma anions) were measured and betaCaOx was calculated in 17 PH-1 patients with normal renal function receiving pyridoxine and citrate therapy, in 54 children with CRI (SCr 0.9 to 5.9 mg/dl), and in 50 healthy children (NL). Plasma anions were analyzed by ion-chromatography and betaCaOx was calculated using a PC-based program for solution equilibria. RESULTS: Compared to NL, all plasma anion levels and betaCaOx were higher in PH-1 and CRI; POx, PCit and betaCaOx were higher in PH-1 than in CRI (P < 0.05), but PSulf was higher in CRI (P < 0.01). BetaCaOx and POx were correlated in all groups (r = 0.63 to 0.95, P < 10(-4)). POx and betaCaOx were both inversely correlated to a decrease in GFR in CRI patients. PCit and PSulf did not influence betaCaOx. Although supersaturation (betaCaOx > 1) was found in 7 CRI and in 4 PH-1 patients, eye examinations were suspicious for CaOx depositions only in the PH-1 patients, while systemic oxalosis was confirmed in one PH patient because of oxalate osteopathy. CONCLUSIONS: In PH-1, POx and betaCaOx are elevated even with normal renal function, which increases the likelihood of CaOx crystal deposition. Therefore, more effective therapy to decrease betaCaOx is crucial to reduce the risk of systemic oxalosis. In children with CRI unknown, but presumably protective substances, help prevent the risk of systemic oxalosis, despite increased POx and betaCaOx levels, often to supersaturation levels.

Calcium Oxalate↗