Two frequent missense mutations in Pendred syndrome

Pendred syndrome is an autosomal recessive disorder characterized by early childhood deafness and goiter. A century after its recognition as a syndrome by Vaughan Pendred, the disease gene ( PDS ) was mapped to chromosome 7q22-q31.1 and, recently, found to encode a putative sulfate transporter. We performed mutation analysis of the PDS gene in patients from 14 Pendred families originating from seven countries and identified all mutations. The mutations include three single base deletions, one splice site mutation and 10 missense mutations. One missense mutation (L236P) was found in a homozygous state in two consanguineous families and in a heterozygous state in five additional non-consanguineous families. Another missense mutation (T416P) was found in a homozygous state in one family and in a heterozygous state in four families. Pendred patients in three non-consanguineous families were shown to be compound heterozygotes for L236P and T416P. In total, one or both of these mutations were found in nine of the 14 families analyzed. The identification of two frequent PDS mutations will facilitate the molecular diagnosis of Pendred syndrome.      

Cyclosiloxanes produce fatal liver and lung damage in mice.

To examine the toxicity of cyclosiloxanes (CSs), the predominant low molecular weight cyclic silicones found in breast implants, we injected female CD-1 mice intraperitoneally with different doses of distillate (3.5-35 g/kg body weight) containing cyclosiloxane D3 (hexamethylcyclotrisiloxane; CS-D3), cyclosiloxane D4 (octamethylcyclotetrasiloxane; CS-D4), cyclosiloxane D5 (decamethylcyclopentasiloxane; CS-D5), and cyclosiloxane D6 (dodecamethylcyclohexasiloxane; CS-D6). The distillate was found to be lethal and all the mice injected with 35 g/kg died within 5-8 days. The median lethal dose (LD50) for distillate was estimated to be approximately 28 g/kg. These mice developed inflammatory lesions of the lung and liver as well as liver cell necrosis with elevated serum levels of alanine aminotransferase, aspartate aminotransferase, and lactic acid dehydrogenase. Administration of CS-D4 alone also produced lethality in these mice with an LD50 of 6-7 g/kg. CS-D4-treated mice also exhibited pulmonary and hepatic lesions and elevated serum enzymes. Analysis of LD50 data indicates that CS-D4 is about as toxic as carbon tetrachloride or trichloroethylene. We measured hydroxyl radical formation in CS-D4-treated mice and found increases of approximately 20-fold in liver and approximately 7-fold in lung on day 4 following injection. Our findings are significant because in vitro experiments have demonstrated that CSs can migrate out of breast implants, and in mouse experiments CSs have been shown to be widely distributed in many organs after a single subcutaneous injection and to persist for at least a year.     

Cholesterol screening and family history of vascular disease

Hypercholesterolaemia is a major risk factor for the development of coronary heart disease (CHD). Early detection and management of hypercholesterolaemia could retard the atherosclerotic process. Given that CHD and hypercholesterolaemia cluster within families, a screening strategy based on a family history of vascular disease has been advocated. Serum total cholesterol concentrations were measured in a random stratified sample of 1012 children aged from 12-15 years old participating in a coronary risk factor surveillance study in Northern Ireland. Information about vascular disease in close family members was obtained by means of a questionnaire. The study population was divided into two groups according to total cholesterol values: (i) normal, < 5.2 mmol/l (n = 822) and (ii) raised, > or = 5.2 mmol/l (n = 190). A family history identified 63 out of 190 individuals with hypercholesterolaemia yielding a sensitivity of 33.2% and specificity of 71.5%. Our data indicated that a strategy whereby only children from high risk families are screened for hypercholesterolaemia is ineffective. While primary prevention emphasising a healthy diet for all is essential, the role of universal screening deserves further appraisal.     

Pediatric experience with intradialytic parenteral nutrition and supplemental tube feeding

Good nutrition is necessary to maximize the potential for growth and development in the pediatric age-group, but children, like adults with chronic renal failure and end-stage renal disease, may be anorectic and eat poorly. Infants and adolescents are at special risk because of the intense demands of growth during the first 2 years of life and again during puberty. Neurodevelopment is also adversely affected by poor nutrition, especially in infants. Approximately two-thirds of pediatric dialysis patients are treated with chronic peritoneal dialysis, which results in significant protein losses in the dialysis effluent that can contribute to protein-calorie malnutrition. Meeting the nutritional needs of pediatric patients usually requires supplemental sources, such as intradialytic parenteral nutrition (IDPN) or tube feeding. Little is known about the effectiveness or desirability of IDPN in pediatric patients. More studies, especially of amino acid-based dialysis fluids for chronic peritoneal dialysis, need to be done before making IDPN a standard for pediatrics. Supplemental nasogastric or gastrostomy tube feedings have been very successful in maintaining and improving growth in infants, but no studies are available to evaluate their success in older children and adolescents. Recombinant growth hormone therapy, in addition to good nutrition and control of other growth factors such as acidosis, renal osteodystrophy, and chronic volume depletion, may be necessary for most growth-retarded children with chronic renal failure to achieve normal adult height.