Increased fluoroscopy time for central venous catheter placement by radiology residents versus staff radiologists.

PURPOSE: To evaluate differences in interventional radiology procedural fluoroscopy time (FT) for radiology residents versus staff radiologists, using central venous catheter (CVC) placement as an index service. METHODS: To minimize interservice and complexity variables, stand-alone temporary internal jugular CVC procedures were targeted for analysis. Reports and images from 1,067 temporary CVC services from 2 hospitals over 2 years were reviewed as part of a quality improvement initiative. Insertion site, catheter type (eg, smaller triple lumen versus larger hemodialysis), resident identifier, staff identifier, and documented FT were compiled and analyzed. RESULTS: Applying clinical (eg, concomitant venous angioplasty) and anatomic (eg, femoral access) exclusions, 537 cases with complete CVC procedure records were available for analysis. Radiology residents and staff radiologists were primary operators in 128 and 409 procedures, respectively. Distribution of resident procedures (82% right, 66% large lumen) was similar to that of staff (79% right, 63% large lumen). Mean FT of resident services was twice as long as that of staff services (1.24 minutes versus 0.63 minutes, P < .0001). Resident FT was independent of supervising staff radiologist. Increasing years of training for residents did not significantly reduce FT. CONCLUSIONS: When CVCs are placed by radiology residents, FT is double that for identical procedures performed by staff radiologists. Similar discrepancies likely exist for other interventional radiologic procedures. Residency training programs should initiate measures to monitor and manage fluoroscopy during interventional procedures to minimize radiation dose to patients, trainees, and other staff.

KREPA4, an RNA binding protein essential for editosome integrity and survival of Trypanosoma brucei.

The 20S editosome, a multiprotein complex, catalyzes the editing of most mitochondrial mRNAs in trypanosomatids by uridylate insertion and deletion. RNAi mediated inactivation of expression of KREPA4 (previously TbMP24), a component of the 20S editosome, in procyclic form Trypanosoma brucei resulted in inhibition of cell growth, loss of RNA editing, and disappearance of 20S editosomes. Levels of MRP1 and REAP-1 proteins, which may have roles in editing but are not editosome components, were unaffected. Tagged KREPA4 protein is incorporated into 20S editosomes in vivo with no preference for either insertion or deletion subcomplexes. Consistent with its S1-like motif, recombinant KREPA4 protein binds synthetic gRNA with a preference for the 3' oligo (U) tail. These data suggest that KREPA4 is an RNA binding protein that may be specific for the gRNA Utail and also is important for 20S editosome stability.

TbMP81 is required for RNA editing in Trypanosoma brucei.

Most mitochondrial mRNAs are edited in Trypano soma brucei by a series of steps that are catalyzed by a multienzyme complex that is in its initial stages of characterization. RNA interference (RNAi)-mediated repression of the expression of TbMP81, a zinc finger protein component of the complex, inhibited growth of bloodstream and insect forms, and blocked in vivo RNA editing. This repression preferentially inhibited insertion editing compared with deletion editing in vitro. It resulted in reduced specific endoribonucleolytic cleavage and a greater reduction of U addition and associated RNA ligation activities than U removal and associated RNA ligation activities. The repressed cells retained 20S editing complexes with several demonstrable proteins and adenylatable TbMP52 RNA ligase, but adenlyatable TbMP48 was not detected. Elimination of TbMP48 by RNAi repression did not inhibit cell growth or in vivo editing in either bloodstream or procyclic forms. These results indicate that TbMP81 is required for RNA editing and suggest that the editing complex is functionally partitioned.

Separate insertion and deletion subcomplexes of the Trypanosoma brucei RNA editing complex.

The Trypanosoma brucei editosome catalyzes the maturation of mitochondrial mRNAs through the insertion and deletion of uridylates and contains at least 16 stably associated proteins. We examined physical and functional associations among these proteins using three different approaches: purification of complexes via tagged editing ligases TbREL1 and TbREL2, comprehensive yeast two-hybrid analysis, and coimmunoprecipitation of recombinant proteins. A purified TbREL1 subcomplex catalyzed precleaved deletion editing in vitro, while a purified TbREL2 subcomplex catalyzed precleaved insertion editing in vitro. The TbREL1 subcomplex contained three to four proteins, including a putative exonuclease, and appeared to be coordinated by the zinc finger protein TbMP63. The TbREL2 subcomplex had a different composition, contained the TbMP57 terminal uridylyl transferase, and appeared to be coordinated by the TbMP81 zinc finger protein. This study provides insight into the molecular architecture of the editosome and supports the existence of separate subcomplexes for deletion and insertion editing.