An 80-year-old male patient had complained of left abdominal pain since 1990, and an abdominal aortic aneurysm (AAA) 5.3cm in diameter was diagnosed by computed tomography (CT). The patient was NYHA class III with complaints of chest pain during exercise. Coronary arteriography showed that he had three-vessel disease. At that time, aneurysmectomy was not anticipated due to his age and because the AAA showed no tendency to enlarge. However, in October 1993, CT showed that the AAA rapidly enlarged to 6.8cm in diameter. Due to the greater risk of rupture of the AAA, aneurysmectomy was considered necessary. The operative mortality associated with aneurysmectomy in patients with coronary artery disease (CAD) is higher than that in patients without CAD. Therefore, coronary artery bypass grafting (CABG) was indicated prior to aneurysmectomy. The patient underwent CABG (two vessels) in December 1993, and aneurysmectomy was successfully performed in February 1994. He was discharged uneventfully 17 days after the operation.

The in vivo assembly of ribosomal subunits is a highly complex process, with a tight coordination between protein assembly and rRNA maturation events, such as folding and processing of rRNA precursors, as well as modifications of selected bases. In the cell, a large number of factors are required to ensure the efficiency and fidelity of subunit production. Here we characterize the immature 30S subunits accumulated in a factor-null Escherichia coli strain (∆rsgA∆rbfA). The immature 30S subunits isolated with varying salt concentrations in the buffer system show interesting differences on both protein composition and structure. Specifically, intermediates derived under the two contrasting salt conditions (high and low) likely reflect two distinctive assembly stages, the relatively early and late stages of the 3' domain assembly, respectively. Detailed structural analysis demonstrates a mechanistic coupling between the maturation of the 5' end of the 17S rRNA and the assembly of the 30S head domain, and attributes a unique role of S5 in coordinating these two events. Furthermore, our structural results likely reveal the location of the unprocessed terminal sequences of the 17S rRNA, and suggest that the maturation events of the 17S rRNA could be employed as quality control mechanisms on subunit production and protein translation.
Cryoelectron Microscopy ; Escherichia coli ; metabolism ; Escherichia coli Proteins ; genetics ; metabolism ; GTP Phosphohydrolases ; genetics ; metabolism ; Mass Spectrometry ; Protein Structure, Secondary ; Protein Structure, Tertiary ; RNA, Ribosomal ; analysis ; metabolism ; Ribosomal Proteins ; chemistry ; genetics ; metabolism ; Ribosome Subunits, Small, Bacterial ; chemistry ; metabolism ; ultrastructure ; Salts ; chemistry