Porcine acellular dermal matrix (PADM) vascularises after exposure in open necrotic wounds seen after complex hernia repair.

Biological alternatives to synthetic meshes are increasingly utilised in complex abdominal wall reconstruction. There is a lack of evidence demonstrating that non-cross-linked porcine acellular dermal matrix vascularizes and integrates with human tissue in suboptimal wound conditions. We aimed to evaluate these properties in Strattice™ (Life Cell Inc., Branchburg, NJ) following ventral hernia repair. A retrospective review of patients with high-risk ventral hernia repair utilising Strattice™ as an onlay after open component separation was conducted. Patients with postoperative wound exploration and exposure of the onlay were included in this review. One patient underwent punch biopsy for histological analysis. Eleven patients with wound complications necessitating postoperative debridement and exposure of Strattice™ onlay were identified. The onlay was partially debrided in two cases, and one case required complete excision. Vascularisation was clinically evident in 10 of 11 cases (91%) as demonstrated by the presence of granulation tissue and/or the ability to support a skin graft. Histological analysis of one onlay 3 months postoperatively showed neovascularisation and collagen remodelling with minimal inflammatory response. Strattice™ demonstrated resistance to rejection, ability to undergo vascularisation and incorporation into host tissues in sub-optimal wound conditions following ventral hernia repair.

A modified approach to component separation using biologic graft as a load-sharing onlay reinforcement for the repair of complex ventral hernia.

BACKGROUND: Components separation has been proposed as a means to close large ventral hernia without undue tension. We report a modification on open components separation that allows for the incorporation of onlaid noncrosslinked porcine acellular dermal matrix (Strattice, LifeCell Corp, Branchburg, NJ) as a load-sharing structure. METHODS: This was a retrospective case series including all cases using Strattice from July 2008 through December 2009. Data evaluated included patient demographics, comorbidities associated with risk of recurrence, hernia grade, and postoperative complications. The primary outcomes were hernia recurrence and surgical site occurrences. RESULTS: There were 58 patients; 60.8% presented with a recurrent incisional hernia. Average length of follow-up was 384 days. There were 4 hernia recurrences (7.9%). Complications included surgical site infection (20.7%), seroma (15.5%), and hematoma (5%) requiring intervention. Four deaths occurred in the series due to causes unrelated to the hernia repair, only 1 within 30 days of operation. CONCLUSIONS: This series demonstrates that components separation reinforced with noncrosslinked porcine acellular dermal matrix onlay is an efficacious, single-stage repair with a low rate of recurrence and surgical site occurrences.

Pectoralis major turnover versus advancement technique for sternal wound reconstruction.

BACKGROUND: We compared the efficacy of pectoralis turnover versus advancement technique for sternal wound reconstruction. METHODS: A retrospective chart review was performed, December 1989 to December 2010, to compare postoperative complication rates between pectoralis major turnover versus pectoralis major advancement reconstruction techniques. Complications included hematomas, wound infections, tissue necrosis, dehiscence, and need for reoperation. Pearson χ and logistic regression were used and significance was P < 0.05. RESULTS: Sixty-seven patients received 91 tissue flaps. Eleven patients (16%) required reoperation due to complications, including recurrent wound infection, tissue necrosis, wound dehiscence, mediastinitis, and hematoma formation. Four patients (6%) were treated conservatively for minor complications. Overall, complication rates were significantly higher after pectoralis major advancement reconstruction (32.5% vs. 3.7%, P = 0.004). CONCLUSIONS: When feasible, pectoralis major turnover flap offers a superior reconstructive technique for complex sternal wounds, with diminished complications compared with the pectoralis advancement flap.

The sentinel fat pads: the relationship of the ROOF and SOOF to the temporal nerve in facial rejuvenation.

BACKGROUND: A great number of studies have reported on the temporal branch anatomy and its relationship to the fascial layers and various fat pads of the temporal region, but no article has included information on the relationship of the temporal nerve to the retro-orbicularis oculi fat (ROOF) and/or the suborbicularis oculi fat (SOOF). OBJECTIVES: The authors report the results of a series of human cadaver temporal nerve dissections, with particular attention paid to its relation to the ROOF and the SOOF. The results of a literature review and a subsequent open browlift are also reported to confirm the results of the cadaver study. METHODS: Dissection was performed on 15 fresh human cadavers, for a total of 29 hemifaces. The course and relationships of the temporal nerve branch to the fascia, fat pads, and landmarks in the temporal region were noted and detailed. A thorough review was also performed for 23 articles, to compare the author's anatomical findings with data in the previous literature. RESULTS: During cadaver dissection, the temporal branch was found to lie on the undersurface of the superficial temporal fascia. In the supraorbital area, the ROOF existed in the loose areolar plane or deep layer of the superficial temporal fascia, with the temporal nerve branch directly superficial to it. The temporal branch passed lateral to the SOOF in its superiomedial course at the level of the zygoma. These findings were later confirmed during an in vivo open browlift as well. CONCLUSIONS: The ROOF was formerly unrecognized as an important sentinel marker for possible injury to the temporal nerve branch during browlift. However, this cadaver study and its accompanying literature comparisons show that browlift dissection, whether endoscopic or open, should aim to keep the ROOF fat in the superficial plane, ensuring that the nerve branch is safe from iatrogenic injury.

Characterization of quinolinate synthases from Escherichia coli, Mycobacterium tuberculosis, and Pyrococcus horikoshii indicates that [4Fe-4S] clusters are common cofactors throughout this class of enzymes.

Quinolinate synthase (NadA) catalyzes a unique condensation reaction between iminoaspartate and dihydroxyacetone phosphate, affording quinolinic acid, a central intermediate in the biosynthesis of nicotinamide adenine dinucleotide (NAD). Iminoaspartate is generated via the action of l-aspartate oxidase (NadB), which catalyzes the first step in the biosynthesis of NAD in most prokaryotes. NadA from Escherichia coli was hypothesized to contain an iron-sulfur cluster as early as 1991, because of its observed labile activity, especially in the presence of hyperbaric oxygen, and because its primary structure contained a CXXCXXC motif, which is commonly found in the [4Fe-4S] ferredoxin class of iron-sulfur (Fe/S) proteins. Indeed, using analytical methods in concert with Mossbauer and electron paramagnetic resonance spectroscopies, the protein was later shown to harbor a [4Fe-4S] cluster. Recently, the X-ray structure of NadA from Pyrococcus horikoshii was solved to 2.0 A resolution [Sakuraba, H., Tsuge, H.,Yoneda, K., Katunuma, N., and Ohshima, T. (2005) J. Biol. Chem. 280, 26645-26648]. This protein does not contain a CXXCXXC motif, and no Fe/S cluster was observed in the structure or even mentioned in the report. Moreover, rates of quinolinic acid production were reported to be 2.2 micromol min (-1) mg (-1), significantly greater than that of E. coli NadA containing an Fe/S cluster (0.10 micromol min (-1) mg (-1)), suggesting that the [4Fe-4S] cluster of E. coli NadA may not be necessary for catalysis. In the study described herein, nadA genes from both Mycobacterium tuberculosis and Pyrococcus horikoshii were cloned, and their protein products shown to contain [4Fe-4S] clusters that are absolutely required for activity despite the absence of a CXXCXXC motif in their primary structures. Moreover, E. coli NadA, which contains nine cysteine residues, is shown to require only three for turnover (C113, C200, and C297), of which only C297 resides in the CXXCXXC motif. These results are consistent with a bioinformatics analysis of NadA sequences, which indicates that three cysteines are strictly conserved across all species. This study concludes that all currently annotated quinolinate synthases harbor a [4Fe-4S] cluster, that the crystal structure reported by Sakuraba et al. does not accurately represent the active site of the protein, and that the "activity" reported does not correspond to quinolinate formation.

The activity of Escherichia coli cyclopropane fatty acid synthase depends on the presence of bicarbonate.

Cyclopropane fatty acid (CFA) synthases catalyze the formation of cyclopropane rings on isolated and unactivated olefinic bonds within various fatty acids; the methylene carbon is derived from the activated methyl group of (S)-adenosylmethionine. The E. coli enzyme is the prototype for this class of enzymes, which include the cyclopropane mycolic acid (CMA) synthases, which are potential targets for the design of antituberculosis agents. Crystal structures of several CMA synthases have recently been solved, and electron density attributed to a bicarbonate ion was found in or near the active site. Because a functional assay for CMA synthases has not been developed, the relevance of the bicarbonate ion has not been established. CFA synthase is 30-35% identical to the CMA synthases that have been analyzed structurally, suggesting that the mechanisms of these enzymes are conserved. In this work, we show that indeed the activity of CFA synthase requires bicarbonate, and that it is inhibited by borate, a planar trigonal molecule that mimics the structure of bicarbonate. We also show that substitutions of the conserved amino acids that act as ligands to the bicarbonate ion based on the structure of CMA synthases result in drastic losses in the activity of the protein.

Escherichia coli quinolinate synthetase does indeed harbor a [4Fe-4S] cluster.

Quinolinic acid is an intermediate in the biosynthesis of nicotinamide-containing redox cofactors. The ultimate step in the formation of quinolinic acid in prokaryotes is the condensation of iminosuccinate and dihydroxyacetone phosphate, which is catalyzed by the product of the nadA gene in Escherichia coli. A combination of UV-vis, Mössbauer, and EPR spectroscopies, along with analytical methods for the determination of iron and sulfide, demonstrates for the first time that anaerobically purified quinolinate synthetase (NadA) from E. coli contains one [4Fe-4S] cluster per polypeptide. The protein is active, catalyzing the formation of quinolinic acid with a Vmax [ET]-1 of 0.01 s-1.