Efficacy of surgical preparation solutions in lumbar spine surgery.

BACKGROUND: Postoperative spinal wound infections are relatively common and are often associated with increased morbidity and poor long-term patient outcomes. The purposes of this study were to identify the common bacterial flora on the skin overlying the lumbar spine and evaluate the efficacy of readily available skin-preparation solutions in the elimination of bacterial pathogens from the surgical site following skin preparation. METHODS: A prospective randomized study was undertaken to evaluate 100 consecutive patients undergoing elective lumbar spine surgery. At the time of surgery, the patients were randomized to be treated with one of two widely used, and Food and Drug Administration (FDA)-approved, surgical skin-preparation solutions: ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol) or DuraPrep (0.7% available iodine and 74% isopropyl alcohol). Specimens for aerobic and anaerobic cultures were obtained prior to skin preparation (pre-preparation), after skin preparation (post-preparation), and after wound closure (post-closure). A validated neutralization solution was used for each culture to ensure that the antimicrobial activity was stopped immediately after the sample was taken. Positive cultures and specific bacterial pathogens were recorded. RESULTS: Coagulase-negative Staphylococcus, Propionibacterium acnes, and Corynebacterium were the most commonly isolated organisms prior to skin preparation. The overall rate of positive cultures prior to skin preparation was 82%. The overall rate of positive cultures after skin preparation was 0% (zero of fifty) in the ChloraPrep group and 6% (three of fifty) in the DuraPrep group (p = 0.24, 95% confidence interval [CI] = 0.006 to 0.085). There was an increase in positive cultures after wound closure, but there was no difference between the ChloraPrep group (34%, seventeen of fifty) and the DuraPrep group (32%, sixteen of fifty) (p = 0.22, 95% CI = 0.284 to 0.483). Body mass index (BMI), duration of surgery, and estimated blood loss did not a show significant association with post-closure positive culture results. CONCLUSIONS: ChloraPrep and DuraPrep are equally effective skin-preparation solutions for eradication of common bacterial pathogens on the skin overlying the lumbar spine.

m-AAA protease-driven membrane dislocation allows intramembrane cleavage by rhomboid in mitochondria.

Maturation of cytochrome c peroxidase (Ccp1) in mitochondria occurs by the subsequent action of two conserved proteases in the inner membrane: the m-AAA protease, an ATP-dependent protease degrading misfolded proteins and mediating protein processing, and the rhomboid protease Pcp1, an intramembrane cleaving peptidase. Neither the determinants preventing complete proteolysis of certain substrates by the m-AAA protease, nor the obligatory requirement of the m-AAA protease for rhomboid cleavage is currently understood. Here, we describe an intimate and unexpected functional interplay of both proteases. The m-AAA protease mediates the ATP-dependent membrane dislocation of Ccp1 independent of its proteolytic activity. It thereby ensures the correct positioning of Ccp1 within the membrane bilayer allowing intramembrane cleavage by rhomboid. Decreasing the hydrophobicity of the Ccp1 transmembrane segment facilitates its dislocation from the membrane and renders rhomboid cleavage m-AAA protease-independent. These findings reveal for the first time a non-proteolytic function of the m-AAA protease during mitochondrial biogenesis and rationalise the requirement of a preceding step for intramembrane cleavage by rhomboid.

The m-AAA protease defective in hereditary spastic paraplegia controls ribosome assembly in mitochondria.

AAA proteases comprise a conserved family of membrane bound ATP-dependent proteases that ensures the quality control of mitochondrial inner-membrane proteins. Inactivation of AAA proteases causes pleiotropic phenotypes in various organisms, including respiratory deficiencies, mitochondrial morphology defects, and axonal degeneration in hereditary spastic paraplegia (HSP). The molecular basis of these defects, however, remained unclear. Here, we describe a regulatory role of an AAA protease for mitochondrial protein synthesis in yeast. The mitochondrial ribosomal protein MrpL32 is processed by the m-AAA protease, allowing its association with preassembled ribosomal particles and completion of ribosome assembly in close proximity to the inner membrane. Maturation of MrpL32 and mitochondrial protein synthesis are also impaired in a HSP mouse model lacking the m-AAA protease subunit paraplegin, demonstrating functional conservation. Our findings therefore rationalize mitochondrial defects associated with m-AAA protease mutants in yeast and shed new light on the mechanism of axonal degeneration in HSP.

Characterization of peptides released from mitochondria: evidence for constant proteolysis and peptide efflux.

Conserved ATP-dependent proteases ensure the quality control of mitochondrial proteins and control essential steps in mitochondrial biogenesis. Recent studies demonstrated that non-assembled mitochondrially encoded proteins are degraded to peptides and amino acids that are released from mitochondria. Here, we have characterized peptides extruded from mitochondria by mass spectrometry and identified 270 peptides that are exported in an ATP- and temperature-dependent manner. The peptides originate from 51 mitochondrially and nuclearly encoded proteins localized mainly in the matrix and inner membrane, indicating that peptides generated by the activity of all known mitochondrial ATP-dependent proteases can be released from the organelle. Pulse-labeling experiments in logarithmically growing yeast cells revealed that approximately 6-12% of preexisting and newly imported proteins is degraded and contribute to this peptide pool. Under respiring conditions, we observed an increased proteolysis of newly imported proteins that suggests a higher turnover rate of respiratory chain components and thereby rationalizes the predominant appearance of representatives of this functional class in the detected peptide pool. These results demonstrated a constant efflux of peptides from mitochondria and provided new insight into the stability of the mitochondrial proteome and the efficiency of mitochondrial biogenesis.

Use of a genetically introduced cross-linker to identify interaction sites of acidic activators within native transcription factor IID and SAGA.

An important goal is to identify the direct activation domain (AD)-interacting components of the transcriptional machinery within the context of native complexes. Toward this end, we first demonstrate that the multisubunit TFIID, SAGA, mediator, and Swi/Snf coactivator complexes from transcriptionally competent whole-cell yeast extracts were all capable of specifically interacting with the prototypic acidic ADs of Gal4 and VP16. We then used hexahistidine tags as genetically introduced activation domain-localized cross-linking receptors. In combination with immunological reagents against all subunits of TFIID and SAGA, we systematically identified the direct AD-interacting subunits within the AD-TFIID and AD-SAGA coactivator complexes enriched from whole-cell extracts and confirmed these results using purified TFIID and partially purified SAGA. Both ADs directly cross-linked to TBP and to a subset of TFIID and SAGA subunits that carry histone-fold motifs.

A kyphectomy technique with reduced perioperative morbidity for myelomeningocele kyphosis.

STUDY DESIGN: The lumbar sacropelvis in 11 patients with myelomeningocele and kyphosis was treated with a subtraction kyphectomy technique and posterior instrumentation. The results of this procedure in the 11 patients were evaluated and compared with previous results. OBJECTIVE: To examine critically their experience using the subtraction (decancellation) vertebrectomy technique combined with posterior instrumentation for myelomeningocele kyphosis, the authors reviewed the charts of 18 myelomeningocele patients who underwent surgery for lumbar kyphosis between 1994 and 1998. SUMMARY OF BACKGROUND: The benefits of restoring sagittal spinal alignment in myelomeningocele patients with severe lumbar kyphosis deformity to achieve postural stability and improved sitting balance generally are accepted. The optimal method of deformity correction, the extent of instrumentation, and the role of limited arthrodesis remain undefined. METHODS: Of the 18 patients considered, 11 met the inclusion criteria of having undergone reconstruction using a subtraction (decancellation) vertebrectomy technique, preservation of the thecal sac, limited arthrodesis with posterior transpedicular lumbosacral instrumentation, and a minimum follow-up evaluation of 2 years. The study considered the age of the patient, number of levels fused, estimated blood loss, preoperative deformity, immediate postoperative correction, magnitude of correction, and maintenance of correction at latest follow-up assessment. RESULTS: The average age at the time of the index procedure was 6 years (range, 3-12 years). The average preoperative kyphosis was 88 degrees (range, 50-149 degrees ). Immediately after surgery, the average curve measurement was 3 degrees lordosis (range, 50 degrees to 50 degrees ). The average magnitude of postoperative sagittal plane deformity correction was 91 degrees (range, 43-126 degrees ). Finally, the magnitude of correction maintained at the final follow-up assessment averaged 66 degrees (range, 22-114 degrees ). This represented an average loss of correction at 2 years of 24 degrees (range, 0-84 degrees ). There were no deaths, episodes of acute-onset hydrocephalus, vascular complications, or chronic deep wound infections. CONCLUSIONS: The subtraction (decancellation) vertebrectomy technique with preservation of the dural sac is a safe and efficacious technique for correction and stabilization of myelomeningocele kyphosis in young patients. Morbidity is reduced, as compared with that of excision techniques. Restoration of sagittal alignment at the time of initial correction and stabilization to achieve a balanced spine led to acceptable results.