Biomedical subjects

Ari M Simckes

Publications and source records attributed to Ari M Simckes.

3 recordsLinked to original sources

PubMed2002

Structural and functional characterization of factor H mutations associated with atypical hemolytic uremic syndrome.

Genetic studies have demonstrated the involvement of the complement regulator factor H in nondiarrheal, nonverocytotoxin (i.e., atypical) cases of hemolytic uremic syndrome. Different factor H mutations have been identified in 10%-30% of patients with atypical hemolytic uremic syndrome (aHUS), and most of these mutations alter single amino acids in the C-terminal region of factor H. Although these mutations are considered to be responsible for the disease, the precise role that factor H plays in the pathogenesis of aHUS is unknown. We report here the structural and functional characterization of three different factor H proteins purified from the plasma of patients with aHUS who carry the factor H mutations W1183L, V1197A, or R1210C. Structural anomalies in factor H were found only in R1210C carriers; these individuals show, in their plasma, a characteristic high-molecular-weight factor H protein that results from the covalent interaction between factor H and human serum albumin. Most important, all three aHUS-associated factor H proteins have a normal cofactor activity in the proteolysis of fluid-phase C3b by factor I but show very low binding to surface-bound C3b. This functional impairment was also demonstrated in recombinant mutant factor H proteins expressed in COS7 cells. These data support the hypothesis that patients with aHUS carry a specific dysfunction in the protection of cellular surfaces from complement activation, offering new possibilities to improve diagnosis and develop appropriate therapies.

Animals↗

PubMed2002

Childhood hyperuricemia and acute renal failure resulting from a missense mutation in the HPRT gene.

A 6-year-old boy was determined to have partial hypoxanthine phosphoribosyl transferase (HPRT) enzyme deficiency without the phenotypic features of Lesch-Nyhan syndrome. He presented with recurrent acute renal failure (ARF) from hyperuricemia. Treatment with allopurinol prevented further attacks of renal failure. T lymphocyte cultures were used to sequence the HPRT cDNA and a novel single nucleotide substitution at codon 65 in exon 3 was found (193C>T, 65leu>phe). This mutation was confirmed by genomic DNA sequencing and was also detected in his heterozygous, asymptomatic mother and sister. Unlike the cells from patients with classic Lesch-Nyhan syndrome, the in vitro cultures of our patient's T-lymphocytes did not proliferate in the presence of purine analogue 6-thioguanine (TG). This report highlights the unusual occurrence of recurrent ARF in a child with partial HPRT enzyme deficiency. The absence of TG resistance in vitro with this mutation shows that even small alterations in enzyme activity in vivo can result in disease symptoms, in this instance, hyperuricemia sufficient to cause ARF. Atypical HPRT mutations should also be considered in cases of unusual renal failure, because correct diagnosis can allow appropriate treatment, as well as informed genetic counseling.

Acute Kidney Injury↗

PubMed2002

Ambulatory blood pressure monitoring in children and adolescents.

With recent technological advances, 24-hour ambulatory blood pressure (BP) monitoring (ABPM) has become a useful tool for the evaluation, diagnosis, and management of hypertensive children. It provides a more accurate representation of an individual's BP rather than intermittent casual or office BP measurements. Hence, ABPM is being used more often to assess the BP of children. In this comprehensive review, we provide the reader with the available literature on ABPM, discuss the advantages and limitations of ABPM, and the interpretation of ABPM data. The role of ABPM in various clinical conditions and hypertension research in children is presented.

Adolescent↗