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Background Within surgical education, there has been a recent emphasis on preparing medical students for the rigors of residency in an effort to improve confidence and technical preparedness throughout postgraduate training. The aim of this study is to test the impact of a boot camp course using the American College of Surgeons–based curriculum and objective, observer-based rating tools on both subjective confidence and objective skills of fourth-year medical students. Materials and Methods Informed consent was obtained on the first day of the boot camp. Before any teaching, students performed 5 tasks (patient handoff, suturing, knot tying, central line placement, and chest tube placement), which were scored using objective rating tools provided by the American College of Surgeons. Students also completed 2 confidence measures. After 2 weeks of dedicated teaching and review, students were scored on the 5 same tasks and repeated the confidence measures. Results Fourth-year medical students (N = 12) who had matched into surgical subspecialties were invited to participate in a 2-week surgical boot camp. All students beginning the study completed the study. The average age was 26.7 years; 25% of students were female. Subspecialties represented included general surgery (n = 5), orthopedics (n = 3), integrated plastics (n = 2), urology (n = 1), and neurosurgery (n = 1). Scores on objective skills improved significantly in all 5 tasks measured. Confidence improved significantly on individual task items, while overall self-efficacy remained unchanged. Conclusions Implementation of a 2-week, multimodal surgical boot camp improved student performance on objectively rated surgical skills and increased student confidence.

Climate and topography have been widely recognized but studied separately as important factors controlling soil organic carbon (SOC) dynamics. Subsequently, the significance of their interplay in determining SOC storages and their pools is not well understood. Here we examined SOC storages and SOC-mineral interactions along two hillslope transects in differing climate zones (MAP = 549 mm in semi-arid eucalyptus savannah vs. 816 mm in temperate eucalyptus forest) in southeastern Australia. On eroding slopes, SOC inventories were twice as large at the wetter site (4.5 ± 0.6 vs. 2.3 ± 0.9 kg m−2), whereas depositional soils had similar SOC inventories at both locations (7.5 ± 2.0 vs.7.0 ± 2.2 kg m−2). On eroding slopes, carbon concentrations of the mineral-associated SOC fraction ( 2.0 g cm−3) increased by ~50% with increasing rainfall, which was also positively correlated to abundances of clay minerals and pedogenic iron oxides. Within individual hillslopes, carbon concentrations of the mineral-associated SOC fraction doubled from eroding to depositional soils at the drier site, but no topographic trend was observed at the wetter site. The effects of topography on SOC inventories and mineral-associated SOC were more strongly expressed under the drier climate, where vegetation was sparser and soil erosion involved mineral grain size sorting. Our results demonstrate that SOC pools and their interactions with minerals are dependent on topographic locations, emphasizing the need to include geomorphic data when assessing climatic controls of SOC.

Interactions between organic carbon (OC) and minerals represent a critical mechanism for stabilizing organic matter in soils. Because both mineral weathering and plant productivity are negatively affected by soil erosion, mineral-associated organic carbon (MOC) chemistry is also expected to vary with erosion intensity. Here we show that MOC chemistry, determined by carbon X-ray absorption near-edge fine structure spectroscopy (XANES), exhibits little difference across a large (10-fold) gradient in erosion-derived soil turnover times. Mineral-associated OC chemistry further fails to explain the variation in radiocarbon-based MOC turnover times. Our results suggest that soil OC longevity is largely independent of organic matter chemistry in steep mountainous landscapes where soil development is constrained by erosion.

Phylogenetically diverse microbes that produce long chain, olefinic hydrocarbons have received much attention as possible sources of renewable energy biocatalysts. One enzyme that is critical for this process is OleA, a thiolase superfamily enzyme that condenses two fatty acyl-CoA substrates to produce a β-ketoacid product and initiates the biosynthesis of long chain olefins in bacteria. Thiolases typically utilize a ping-pong mechanism centered on an active site cysteine residue. Reaction with the first substrate produces a covalent cysteine-thioester tethered acyl group that is transferred to the second substrate through formation of a carbon-carbon bond. Although the basics of thiolase chemistry are precedented, the mechanism by which OleA accommodates two substrates with extended carbon chains and a coenzyme moiety—unusual for a thiolase—are unknown. Gaining insights into this process could enable manipulation of the system for large scale olefin production with hydrocarbon chains lengths equivalent to those of fossil fuels. In this study, mutagenesis of the active site cysteine in Xanthomonas campestris OleA (Cys143) enabled trapping of two catalytically relevant species in crystals. In the resulting structures, long chain alkyl groups (C12 and C14) and phosphopantetheinate define three substrate channels in a T-shaped configuration, explaining how OleA coordinates its two substrates and product. The C143A OleA co-crystal structure possesses a single bound acyl-CoA representing the Michaelis complex with the first substrate, whereas the C143S co-crystal structure contains both acyl-CoA and fatty acid, defining how a second substrate binds to the acyl-enzyme intermediate. An active site glutamate (Gluβ117) is positioned to deprotonate bound acyl-CoA and initiate carbon-carbon bond formation.

Triuret (carbonyldiurea) is an impurity found in industrial urea fertilizer (

In this study, a 3-step design and optimization method is presented for a bioremediation system utilizing silica gel encapsulated whole-cell biocatalyst. Characterization experiments were conducted to determine the parameters of a steady state reaction/diffusion model for encapsulated AtzA biocatalyst that was subsequently verified experimentally. Dimensionless numbers governing the reaction rate, the Thiele modulus (Φ) and effectiveness factor (η), were evaluated based on the design parameters of the material, ρ (cell loading density) and Lc (characteristic length). Mechanical properties of the gel were determined as a function of ρ. Optimal values for ρ and Lc were determined for a case study, based on biocatalytic performance, mechanical properties and cost. It was found that free biocatalyst reaction kinetics are first order with k free ′ = 7.38 × 10−2 s−1/(g cells/mL) and diffusivity of atrazine in the gel increases with ρ, from 3.51 × 10−4 mm2/s up to 6.93 × 10−4 mm2/s. Modeling results showed that ∼20% of activity was lost during encapsulation. Diffusion limitations became significant (Φ > 1) when Lc exceeded 0.1–0.3 mm. The optimal catalyst radius and cell loading density were determined to be Lc = 0.2 mm and ρ = 0.11 g cells/mL gel, for an atrazine bioremediation setup with a desired effluent

Background Few studies have evaluated the impact of the upright position on the success of oral-tracheal intubation. Yet, for patients with airway difficulties (i.e, active intraoral bleeding or morbidly obese), the upright position may both benefit the patient and facilitate intubation. Objectives We compared the success rates of subjects performing standard intubation to a modified version of the sitting face-to-face oral-tracheal intubation technique on a simulation model. We also reviewed the possible advantages and limitations of the sitting face-to-face intubation technique. Methods Volunteer medical and paramedical students were given instruction, then tested, performing in random order both standard oral-tracheal and two-person sitting face-to-face oral-tracheal intubation on full-bodied mannequins. Observers reviewed video recordings, noting the number of successful intubations and the time to completion of each procedure at 15, 20, and 30 s. Results All of the sitting face-to-face intubations were successful, 53/53 (100%, 95% confidence interval [CI] 93–100%); whereas of the 53 subjects who performed standard intubation, 48 were successful (91%, 95% CI 80–96%). The difference between successful intubations using the standard vs. sitting face-to-face technique was 9% (95% CI 1.3–9.4%, p =0.025). At times 15 and 20 s, medical student subjects who successfully performed both techniques were less successful at completing the procedure when performing the standard technique as compared to the sitting face-to-face technique ( p =0.016). A post-procedural survey found that the majority of subjects preferred the sitting technique. Conclusion Subjects were significantly more successful at performing and preferred the sitting face-to-face intubation when compared to standard intubation.

OleA catalyzes the condensation of fatty acyl groups in the first step of bacterial long-chain olefin biosynthesis, but the mechanism of the condensation reaction is controversial. In this study, OleA from Xanthomonas campestris was expressed in Escherichia coli and purified to homogeneity. The purified protein was shown to be active with fatty acyl-CoA substrates that ranged from C8 to C16 in length. With limiting myristoyl-CoA (C14), 1 mol of the free coenzyme A was released/mol of myristoyl-CoA consumed. Using [14C]myristoyl-CoA, the other products were identified as myristic acid, 2-myristoylmyristic acid, and 14-heptacosanone. 2-Myristoylmyristic acid was indicated to be the physiologically relevant product of OleA in several ways. First, 2-myristoylmyristic acid was the major condensed product in short incubations, but over time, it decreased with the concomitant increase of 14-heptacosanone. Second, synthetic 2-myristoylmyristic acid showed similar decarboxylation kinetics in the absence of OleA. Third, 2-myristoylmyristic acid was shown to be reactive with purified OleC and OleD to generate the olefin 14-heptacosene, a product seen in previous in vivo studies. The decarboxylation product, 14-heptacosanone, did not react with OleC and OleD to produce any demonstrable product. Substantial hydrolysis of fatty acyl-CoA substrates to the corresponding fatty acids was observed, but it is currently unclear if this occurs in vivo. In total, these data are consistent with OleA catalyzing a non-decarboxylative Claisen condensation reaction in the first step of the olefin biosynthetic pathway previously found to be present in at least 70 different bacterial strains.

Atrazine chlorohydrolase, TrzN (triazine hydrolase or atrazine chlorohydrolase 2), initiates bacterial metabolism of the herbicide atrazine by hydrolytic displacement of a chlorine substituent from the s-triazine ring. The present study describes crystal structures and reactivity of wild-type and active site mutant TrzN enzymes. The homodimer native enzyme structure, solved to 1.40 Å resolution, is a (βα)(8) barrel, characteristic of members of the amidohydrolase superfamily. TrzN uniquely positions threonine 325 in place of a conserved aspartate that ligates the metal in most mononuclear amidohydrolases superfamily members. The threonine side chain oxygen atom is 3.3 Å from the zinc atom and 2.6 Å from the oxygen atom of zinc-coordinated water. Mutation of the threonine to a serine resulted in a 12-fold decrease in k(cat)/K(m), largely due to k(cat), whereas the T325D and T325E mutants had immeasurable activity. The structure and kinetics of TrzN are reminiscent of carbonic anhydrase, which uses a threonine to assist in positioning water for reaction with carbon dioxide. An isosteric substitution in the active site glutamate, E241Q, showed a large diminution in activity with ametryn, no detectable activity with atratone, and a 10-fold decrease with atrazine, when compared with wild-type TrzN. Activity with the E241Q mutant was nearly constant from pH 6.0 to 10.0, consistent with the loss of a proton-donating group. Structures for TrzN-E241Q were solved with bound ametryn and atratone to 1.93 and 1.64 Å resolution, respectively. Both structure and kinetic determinations suggest that the Glu(241) side chain provides a proton to N-1 of the s-triazine substrate to facilitate nucleophilic displacement at the adjacent C-2.

A century of biodegradation and natural product chemistry research has provided the backdrop for more deeply understanding the evolution of new degradative enzymes. Natural products serve as substrates and select for enzymes that may later act on industrial chemicals via analogous mechanisms. Enzymes that work on a range of substrates are said to be catalytically promiscuous. Studies are advancing with the development of tools to quantitatively assess catalytic promiscuity. Moreover, the role of catalytic promiscuity in evolution can now be studied by looking at genome-wide changes and their effects on cell survival. The expansion of public databases dealing with chemical compounds and metabolic reactions facilitates this research and now allows for the computational prediction of biodegradative metabolism.

Broad-based adoption of biocatalytic methods will require widely available database tools, analogous to previous efforts compiling information for the facilitation of chemical synthesis. The analog to chemical reagents are enzymes. The analog to chemical synthetic routes are metabolic pathways. The free on-line database BRENDA exemplifies efforts to compile relevant information on enzymes for biocatalytic purposes. Likewise, the University of Minnesota Biocatalysis/Biodegradation Database focuses on novel enzymes and metabolic pathways useful in environmental and industrial biotechnology. The development of biocatalytic protocols will be facilitated by the increasing availability of well-curated database information on enzymatic enantioselectivity and capabilities for transforming disparate chemical functional groups.

Teen pregnancy has declined throughout North America in the 1990s. In Yukon Territory, Canada, teen pregnancy in the late 1990s was almost 40% lower than in the early 1990s. This rate of decline is significantly greater than most recently reported national rates of teen pregnancy decline in Canada and United States. Identifying possible causes of the Yukon decline may help policy makers and program managers plan and implement teen pregnancy prevention strategies. Data on Yukon teen pregnancy prevention initiatives were collected through numerous discussions and interviews with Yukon service providers, teens, and the general public between 1994 and 2001. Analysis of data demonstrates that multiple new initiatives spanning many sectors were implemented in the mid and late 1990s that could have contributed to the decline in Yukon teen pregnancy. A multi-dimensional approach to teen pregnancy prevention that included researching and evaluating family planning programs and policies before, during, and after implementation, increasing access to longer-acting hormonal contraceptives, providing continuing family planning medical education to health care providers and other youth service providers, subsidization of contraceptives, delivery of innovative family planning mass media campaigns, and delivery of ongoing sexual health education programs may have significantly contributed to the decline in Yukon teen pregnancy. Collaboration among service providers across many service sectors (clinical, public health, education, First Nations, government communication and policy, grassroots) facilitated coordination of the multi-dimensional approach.

Oxygenases are a broad class of enzymes which are important for the catabolism or recycling of organic matter in the environment. Bacterial catabolism of hydrocarbons and substituted aromatic compounds often uses dioxygenases containing a Rieske iron–sulfur cluster and a non-heme iron center. The dioxygenases have been useful in producing oxygenated materials directly, or indirectly by generating chiral synthetic intermediates. The recent availability of protein structures and gene sequences provides new opportunities for expanding the usefulness of this enzyme class.

Iatrogenic Horner syndrome is a rare complication of chest tube insertion, with little information available on this topic in the pediatric literature. We present a case of a 13-month-old boy with a left-sided pneumonia and an associated pleural effusion for which a chest tube was inserted. His respiratory and septic parameters improved, but he was noted to have ptosis, miosis, and anhydrosis of the left side. These resolved in the days after chest tube removal. Although tube thoracostomy is a common procedure in surgical practice, little is written about the potential for injury to the ipsilateral sympathetic chain. This report reviews the available literature, with an emphasis on complication avoidance.