Engineering acetyl-CoA supply and ERG9 repression to enhance mevalonate production in Saccharomyces cerevisiae.

Mevalonate is a key precursor in isoprenoid biosynthesis and a promising commodity chemical. Although mevalonate is a native metabolite in Saccharomyces cerevisiae, its production is challenged by the relatively low flux toward acetyl-CoA in this yeast. In this study we explore different approaches to increase acetyl-CoA supply in S. cerevisiae to boost mevalonate production. Stable integration of a feedback-insensitive acetyl-CoA synthetase (Se-acsL641P) from Salmonella enterica and the mevalonate pathway from Enterococcus faecalis results in the production of 1,390 ± 10 mg/l of mevalonate from glucose. While bifid shunt enzymes failed to improve titers in high-producing strains, inhibition of squalene synthase (ERG9) results in a significant enhancement. Finally, increasing coenzyme A (CoA) biosynthesis by overexpression of pantothenate kinase (CAB1) and pantothenate supplementation further increased production to 3,830 ± 120 mg/l. Using strains that combine these strategies in lab-scale bioreactors results in the production of 13.3 ± 0.5 g/l, which is ∼360-fold higher than previously reported mevalonate titers in yeast. This study demonstrates the feasibility of engineering S. cerevisiae for high-level mevalonate production.

Endoscopic sinonasal meningoencephalocele repair: a 13-year experience with stratification by defect and reconstruction type.

OBJECTIVE: Sinonasal meningoencephalocele is a rare defect, with varying etiologies and treatment strategies. Here we present the largest published series from a single institution of patients with endoscopic repair. The primary goal is to examine rates of success with consideration to accompanying patient demographic data. The secondary goal is to report the results stratified by defect and reconstruction type. DESIGN: Retrospective consecutive case series. SETTING: Tertiary care academic center. SUBJECTS AND METHODS: Consecutive patients with CPT codes for skull base meningoencephalocele repair between May 2000 and March 2013 were reviewed. Patients who specifically had sinonasal defects were included. RESULTS: During the study period, 149 cases of sinonasal meningoencephaloceles were managed in 133 patients. Mean follow-up was 21.3 months (range, 0-116). There was a success rate of 88% for initial repair, with mean recurrence time of 8.3 months (range, 0-38), and a success rate of 93.8% for initial recurrence surgery, with 99.3% of ultimate successful repair. All cases were repaired endoscopically. Recurrence rate was not significantly related to location of defect (P = .682), size of defect (P = .434), particular reconstruction technique (P = .163), or etiology (trauma, P = .070). Overall complication rate was 11.3%. CONCLUSION: Endoscopic sinonasal meningoencephalocele repair has excellent long-term results and may be considered as a primary approach. Surgeon comfort with a particular technique should be the most important factor used to guide choice of reconstruction.

Minimizing morbidity in endoscopic pituitary surgery: outcomes of the novel nasoseptal rescue flap technique.

OBJECTIVE: The novel nasoseptal rescue flap has been proven to provide complete coverage of dural defects that may be encountered during endoscopic pituitary surgery through cadaveric studies. In this case series, the authors report outcomes from the first cohort of patients who had a nasoseptal rescue flap raised prior to surgery. STUDY DESIGN: Case series with chart review. SETTING: University of North Carolina-Chapel Hill. SUBJECTS AND METHODS: Patients requiring nasoseptal rescue flaps were identified from the senior author's database. RESULTS: Nasoseptal rescue flaps were harvested in 26 consecutive patients, with only 7 (27%) patients actually requiring use of the rescue flap for skull base reconstruction due to intraoperative cerebrospinal fluid (CSF) leak. Six patients had low-flow CSF leaks, whereas 1 patient had a high-flow CSF leak. Nineteen patients had pituitary adenomas, whereas 7 patients had Rathke cleft cyst. Mean follow-up time was 6 months (range, 1-16 months). Since surgery, no patients have presented with CSF leak or septal perforation. The success rate in those 7 patients with rescue flap utilization was 100%. CONCLUSION: The nasoseptal rescue flap is an effective surgical technique for patients undergoing pituitary surgery without a planned nasoseptal flap. It allows for vascularized skull base reconstruction if an intraoperative CSF leak is encountered and minimizes donor site morbidity if a leak is not encountered.

Pediatric acute sinusitis: predictors of increased resource utilization.

OBJECTIVE: To determine variations in resource utilization in the management of pediatric acute sinusitis. STUDY DESIGN: Retrospective analysis of a publicly available national dataset. METHODS: The Kids' Inpatient Database 2006 was analyzed using ICD-9 codes for acute sinusitis. RESULTS: A total of 8,381 patients (55% male, mean age 8.5 years [SE = 0.2]) were admitted with acute sinusitis. Mean total charges was $20,062 (SE = 1,159.1). Mean length of stay was 4.2 days (SE = 0.12), with 4.8 diagnoses (SE = 0.06) and 0.85 procedures (SE = 0.06). Thirty-six percent had concomitant respiratory diseases, 11% otitis media, and 8% orbital symptoms. A total of 703 patients underwent operations on the upper aerodigestive tract (534 were nasal sinusectomies); 582 patients underwent lumbar puncture and 162 underwent orbital surgery. The primary payer was private insurance in 50% and Medicaid in 41%. Predictors of increased total charges were male gender (P =.028), being a teaching hospital (P < .0001), metropolitan patient location (P < .0001), hospitals in the western region (P < .0001), admission source from another hospital (P < .0001), and discharge status to another inpatient hospital or home healthcare (P < .0001). There is a large geographic variation in resource utilization (range = $5,837 [Arkansas] to $48,327 [California]). Race, primary payer, admission type, and urgency were not significant predictors of increased resource utilization. CONCLUSIONS: Despite being a common diagnosis, there exists a large national variation in management of acute pediatric sinusitis. Predictors of increased resource utilization included male gender, teaching hospital status, metropolitan patient location, western hospital region, admission source, and discharge status. Knowledge of these variables may allow interventions and potentially facilitate benchmarking to reduce the economic burden of this entity while ensuring optimal outcomes.

Ranking chemical structures for drug discovery: a new machine learning approach.

With chemical libraries increasingly containing millions of compounds or more, there is a fast-growing need for computational methods that can rank or prioritize compounds for screening. Machine learning methods have shown considerable promise for this task; indeed, classification methods such as support vector machines (SVMs), together with their variants, have been used in virtual screening to distinguish active compounds from inactive ones, while regression methods such as partial least-squares (PLS) and support vector regression (SVR) have been used in quantitative structure-activity relationship (QSAR) analysis for predicting biological activities of compounds. Recently, a new class of machine learning methods - namely, ranking methods, which are designed to directly optimize ranking performance - have been developed for ranking tasks such as web search that arise in information retrieval (IR) and other applications. Here we report the application of these new ranking methods in machine learning to the task of ranking chemical structures. Our experiments show that the new ranking methods give better ranking performance than both classification based methods in virtual screening and regression methods in QSAR analysis. We also make some interesting connections between ranking performance measures used in cheminformatics and those used in IR studies.

Predicting alternate structure attainment and amyloidogenesis: a nonlinear signal analysis approach.

Chain hydrophobicity values have been used in prediction of alternate structure attainment by a polypeptide. Nonlinear signal analysis on the hydrophobicity values gives important clues about the propensities of particular stretches of a protein to form local or nonlocal contacts. These contacts determine the folding behavior of a polypeptide and helps in predicting the final structure that can be attained. A nonlinear signal analysis called the recurrent quantification analysis has been carried out using the hydrophobicity values on a wide range of proteins obtained from human, plant, and fungal sources. Here, we show that such an analysis gives us an easy handle in determining sequences within the proteins that may be important in beta-sheet formation leading to amyloidosis.