Deletion of nifB results in the formation of a variant nitrogenase MoFe protein (DeltanifB MoFe protein) that appears to contain two normal [8Fe-7S] P clusters. This protein can be reactivated to form the holo MoFe protein upon addition of isolated FeMo cofactor. In contrast, deletion of nifH results in a variant protein (DeltanifH MoFe protein) that appears to contain FeS clusters different from the normal P cluster, presumably representing precursors of the normal P cluster. The DeltanifH MoFe protein is not reconstituted to the holo MoFe protein with isolated FeMo cofactor. The EPR and EXAFS spectroscopic properties of FeS clusters in the DeltanifH MoFe protein clearly differ from those of the normal P cluster found in the DeltanifB MoFe protein and suggest the presence of [4Fe-4S]-like clusters. To further characterize the metal cluster structures in the DeltanifH MoFe protein, a variable-temperature, variable-field magnetic circular dichroism (VTVH-MCD) spectroscopic study has been undertaken on both the DeltanifB MoFe protein and the DeltanifH MoFe protein in both the dithionite-reduced and oxidized states. This study clearly shows that each half of the dithionite-reduced DeltanifH MoFe protein contains a [4Fe-4S]+ cluster paired with a diamagnetic [4Fe-4S]-like cluster. Upon oxidation, the VTVH-MCD spectrum of the DeltanifH MoFe protein reveals a paramagnetic, albeit EPR-silent system, suggesting an integer spin state. These results suggest that the DeltanifH MoFe protein contains a pair of neighboring, unusual [4Fe-4S]-like clusters, which are paramagnetic in their oxidized state.

Objective: The aim of this study was to identify procedure-specific risk factors independently associated with incisional hernia (IH) and demonstrate the feasibility of preoperative risk stratification through the use of an IH risk calculator app and decision–support interface. Summary Background Data: IH occurs after 10% to 15% of all abdominal surgeries (AS) and remains among the most challenging, seemingly unavoidable complications. However, there is a paucity of readily available, actionable tools capable of predicting IH occurrence at the point-of-care. Methods: Patients (n = 29,739) undergoing AS from 2005 to 2016 were retrospectively identified within inpatient and ambulatory databases at our institution. Surgically treated IH, complications, and costs were assessed. Predictive models were generated using regression analysis and corroborated using a validation group. Results: The incidence of operative IH was 3.8% (N = 1127) at an average follow-up of 57.9 months. All variables were weighted according to β-coefficients generating 8 surgery-specific predictive models for IH occurrence, all of which demonstrated excellent risk discrimination (C-statistic = 0.76–0.89). IH occurred most frequently after colorectal (7.7%) and vascular (5.2%) surgery. The most common occurring risk factors that increased the likelihood of developing IH were history of AS (87.5%) and smoking history (75%). An integrated, surgeon-facing, point-of-care risk prediction instrument was created in an app for preoperative estimation of hernia after AS. Conclusions: Operative IH occurred in 3.8% of patients after nearly 5 years of follow-up in a predictable manner. Using a bioinformatics approach, risk models were transformed into 8 unique surgery-specific models. A risk calculator app was developed which stakeholders can access to identify high-risk IH patients at the point-of-care.

Obese and underweight patients undergoing proctectomy for neoplasm are at a higher risk for postoperative complications and death.

Background: Various surgical techniques exist for lower extremity reconstruction, but limited high-quality data exist to inform treatment strategies. Using multi-institutional data and rigorous matching, the authors evaluated the effectiveness and cost of three common surgical reconstructive modalities. Methods: All adult subjects with lower extremity wounds who received bilayer wound matrix, local tissue rearrangement, or free flap reconstruction were retrospectively reviewed (from 2010 to 2017). Cohorts’ comorbidities and wound characteristics were balanced. Graft success at 180 days was the primary outcome; readmissions, reoperations, and costs were secondary outcomes. Results: Five hundred one subjects (166 matrix, 190 rearrangement, and 145 free flap patients) were evaluated. Matched subjects (n = 312; 104/group) were analyzed. Reconstruction success at 180 days for matrix, local tissue rearrangement, and free flaps was 69.2 percent, 91.3 percent, and 93.3 percent (p < 0.001), and total costs per subject were $34,877, $35,220, and $53,492 (p < 0.001), respectively. Median length of stay was at least 2 days longer for free flaps (p < 0.0001). Readmissions and reoperations were greater for free flaps. Local tissue rearrangement, if achievable, provided success at low cost. Free flaps were effective with large, traumatic wounds but at higher costs and longer length of stay. Matrices successfully treated older, obese patients without exposed bone. Conclusions: Lower extremity reconstruction can be performed effectively using multiple modalities with varying degrees of success and costs. Local tissue rearrangement and free flaps demonstrate success rates greater than 90 percent. Bilayer wound matrix-based reconstruction effectively treats a distinct patient population. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.