Congenital absence of aortic valvar leaflets: a rare variant of the hypoplastic left heart syndrome.

Congenital absence of aortic valvar leaflets is a rare and fatal variant of the hypoplastic left heart syndrome. We describe a recent patient seen at our institution with this lesion, illustrating a combined echocardiographic and angiographic approach that delineates both anatomy and physiology. The early mortality experienced in previous reports, as well as unsuccessful surgical palliation in our case, should promote further discussion regarding the optimal treatment.

DNA bending near the replication origin of IncFII plasmid NR1.

The DNA replication origin of plasmid NR1 is located approximately 190 base pairs downstream from the 3' end of the repA1 gene, which encodes the essential initiation protein for replication of the plasmid. Restriction endonuclease fragments that contain the NR1 replication origin and its flanking sequences at circularly permuted positions were obtained by digesting oligomers of ori-containing DNA fragments with sets of enzymes that each cut only once in every ori fragment. Polyacrylamide gel electrophoresis of these permuted restriction fragments showed anomalous mobilities, indicating the presence of a DNA bending locus. Through analysis of the relative mobility plots of these permuted fragments, we found one or two possible DNA bending sites located in the intervening region between the repA1 gene and the replication origin of NR1. It seems possible that DNA bending in this region might help to orient the replication origin alongside the repA1 gene, which could contribute to the cis-acting character of the RepA1 initiation protein.