Mapping the Friedreich ataxia locus (FRDA) by linkage disequilibrium analysis with highly polymorphic microsatellites.

The Friedreich's ataxia locus (FRDA) is tightly linked to markers D9S5 and D9S15 located in 9q13-q21. Cumulated maximum lod scores between FRDA and D9S5 and between FRDA and D9S15 are above 36 and 61, respectively, at a recombination fraction of 0, indicating that recombination events needed to orient the search of the gene are very difficult to identify and ascertain. We have established a 1 Megabase PFGE map around D9S5 and D9S15 and isolated a corresponding 530 kb YAC contig. We found that the two markers are 260 kb apart. This result was surprising, since D9S5 and D9S15 were independently isolated, but in agreement with the strong linkage between the two loci (lod score > 35 at a recombination fraction of 0). Seven clusters of rare cutter enzyme sites (CpG islands), which are potential indicators of genes, were identified in the 1 Megabase region by PFGE analysis and YAC mapping. The search for genes around the CpG islands is in progress. To map the Friedreich ataxia locus in the absence of clearly identified recombination events, we chose an alternative approach based on haplotype analysis of patients from small populations with precise geographic and historical origins, such as the Louisiana-Acadians, deported from Nova-Scotia about 150 years ago and who remained isolated for historical and cultural reasons. In this population, a single mutation, associated with a specific haplotype may account for the majority of Friedreich ataxia cases. Haplotypes different from the major haplotype at one or the other extremity can indicate ancient recombinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous cholangiography and sonography in acute cholecystitis: prospective evaluation.

Twenty-seven patients with clinically suspected acute cholecystitis were prospectively evaluated for supporting evidence with intravenous cholangiography and gray scale sonography. Twenty of these fulfilled criteria for inclusion in the study. Sonography was found to be helpful in all 20 patients (100%). Intravenous cholangiography could be performed in 16 patients (four patients had elevated bilirubin greater than 4 mg/dl). Of these 16, cholangiography was diagnostic in nine (56.3% accuracy). Because of the superiority of sonography and the morbidity and mortality associated with intravenous cholangiography, the study was terminated. Consequently, it is believed sonography is superior to intravenous cholangiography in the evaluation of suspected acute cholecystitis.