Biomedical subjects
Publications and source records attributed to F J Stewart.
Williams syndrome was first described in 1961 (Williams et al. 1961) and is a well-recognised clinical syndrome characterised by growth deficiency, learning difficulties and a typical facies. We describe a 9-year-old girl with classical features of Williams syndrome who presented with acute vocal cord paralysis for which no other cause was found.
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Wolcott-Rallison syndrome is a rare autosomal recessive condition characterized by diabetes mellitus arising in early infancy and multiple epiphyseal dysplasia. To date, nine cases have been described in the world literature. We report an affected girl who died at the age of 4 years and on whom a full autopsy was performed. In addition to neonatal diabetes mellitus and epiphyseal dysplasia, this child had mental retardation and recurrent episodes of self-limiting hepatic failure. Autopsy revealed severe pancreatic hypoplasia and markedly abnormal pancreatic histology, while histology of the bone was consistent with epiphyseal dysplasia. There was laryngeal stenosis and pulmonary hypoplasia. The heart was enlarged with mitral value dysplasia and stenosis, left atrial dilatation, left ventricular hypertrophy, and endocardial fibroelastosis. Examination of the central nervous system showed arrhinencephaly and cerebellar cortical dysplasia. The liver showed minor histological abnormalities but no features were present to account for the recurrent hepatic failure. In addition to Wolcott-Rallison syndrome this child had a deletion at 15q11-12 in 65% of her cells.
DNA cleavage by the modification-dependent restriction enzyme McrBC requires the presence of two suitably modified recognition elements appropriately spaced in the substrate. To characterize the spacing requirement in more detail, we have constructed a plasmid with a single McrBC cleavage site, in which the distance between recognition elements could be systematically varied while preserving the local sequence surrounding the recognition elements. Optimal separation between elements was 55-103 basepairs, with detectable cleavage observed at spacing of 32 bp to 2 kb; no cleavage was seen with spacing of 22 bp or less or with 3 kb between elements. Changing the spacing by 4 basepairs within the optimal range had little effect on the efficiency of cleavage, suggesting that the recognition elements need not lie on the same face of the DNA helix.