Evolutionary implications of C2 photosynthesis: how complex biochemical trade-offs may limit C4 evolution.

The C2 carbon-concentrating mechanism increases net CO2 assimilation by shuttling photorespiratory CO2 in the form of glycine from mesophyll to bundle sheath cells, where CO2 concentrates and can be re-assimilated. This glycine shuttle also releases NH3 and serine into the bundle sheath, and modelling studies suggest that this influx of NH3 may cause a nitrogen imbalance between the two cell types that selects for the C4 carbon-concentrating mechanism. Here we provide an alternative hypothesis outlining mechanisms by which bundle sheath NH3 and serine play vital roles to not only influence the status of C2 plants along the C3 to C4 evolutionary trajectory, but to also convey stress tolerance to these unique plants. Our hypothesis explains how an optimized bundle sheath nitrogen hub interacts with sulfur and carbon metabolism to mitigate the effects of high photorespiratory conditions. While C2 photosynthesis is typically cited for its intermediary role in C4 photosynthesis evolution, our alternative hypothesis provides a mechanism to explain why some C2 lineages have not made this transition. We propose that stress resilience, coupled with open flux tricarboxylic acid and photorespiration pathways, conveys an advantage to C2 plants in fluctuating environments.

Limb Fasciotomy for COVID-19 Patients: Is the Chance to Cut a Chance to Cure?

Based on the findings of two consecutive cases of upper extremity compartment syndrome encountered at our institution, we hypothesize that the presence of compartment syndrome in the unstable COVID-19 patient may be associated with high mortality and low limb salvage rates. A literature search was conducted with key search terms, including "compartment syndrome, fasciotomy, COVID, and coronavirus." Articles describing patients with a confirmed COVID-19 diagnosis who developed extremity compartment syndrome were included in our study. The primary outcome investigated was patient survival. Secondary outcomes included limb survival and limb salvage. Limb salvage was calculated in patients who survived to time of discharge, whereas limb survival was counted for all patients. We then added our two cases to the findings reported in our literature to determine current overall limb salvage and patient survival rates. Our review of the literature yielded six case reports of ten extremities that developed compartment syndrome in the COVID-19 positive patient. Overall survival was four of six patients (67%). The overall limb survival rate at the time of hospital discharge was three of 10 (30%). With the addition of our two cases, overall survival was four of eight (50%) and overall limb survival rate was three of 12 (25%). Furthermore, with inclusion of our two cases, the patient survival rate of hemodynamically unstable patients was only three of seven (43%). The development of compartment syndrome in the unstable COVID-19 patient may be a harbinger of death, and the decision to proceed with operative intervention is challenging, complex, and in some cases must prioritize life over limb.

Transfusion Ethics in a Pediatric Jehovah's Witness Trauma Patient: Simulation Case.

INTRODUCTION: Current ethical practice allows for adult patients with decision-making capacity to refuse blood transfusion, even at the cost of high morbidity or mortality. However, for an adult patient who is of the Jehovah's Witness faith, an unwanted blood transfusion confers a psychospiritual cost to the patient and a financial cost to health care entities. The ethical boundaries are increasingly ambiguous with minors who are members of the Jehovah's Witness faith. This simulation experience intends to identify and address knowledge gaps in the care of minors in an emergent setting using a biomedical ethics framework. METHODS: This scenario provides an immersive simulation experience involving a 12-year-old Jehovah's Witness patient requiring emergent laparotomy for splenic hemorrhage. Patient interview (via simulation manikin with instructor voice) and care handoff take place in an operating room setting. The learner ascertains the patient's and family's refusal of blood products. Induction of general anesthesia results in profound patient hypotension secondary to acute blood-loss anemia. Pulseless electrical activity results if packed red blood cells are not administered. Ethical principles require the learner to impose an unwanted lifesaving therapy on a minor patient over the objections of family members. Secondly, the anesthesia provider must advocate for transfusion on these ethical grounds against a well-meaning but ultimately misguided surgeon who opposes transfusion. An included learner evaluation form based on ACGME core competencies facilitates postsimulation debriefing. RESULTS: Participants were primarily anesthesia residents and fellows. Anecdotally, the residents said that it "felt good to be an attending" and that the simulation helped them appreciate how important conflict resolution skills are in the OR setting. Additionally, faculty appreciated the ability to assess the development of crucial assertiveness skills, with the option of remediating incorrect behavior during the debriefing. DISCUSSION: This simulation experience provides experience in the emergent medical management of a pediatric trauma patient while also incorporating specific ethical consent issues unique to pediatric and trauma patient populations. Furthermore, this experience develops professionalism skills and practice in assertive patient advocacy.

Do peer guidelines or editorial policies affect the reporting and discussion of race and ethnicity in pediatric research?

OBJECTIVES: Two policy statements published in pediatric journals encouraged researchers not to use race and ethnicity [R/E] to explain cohort differences without collecting and analyzing data that examine the potential underlying social mechanisms. We sought to determine if these statements had any impact on the reporting and discussion of R/E and sociodemographic markers [SM]. METHODS: Articles in three general pediatric journals between July 2002 and June 2003 were reviewed, and were compared with previously collected data from July 1999-June 2000. We recorded whether the articles documented R/E or SM, or both, in the results, and whether they discussed their significance. Researchers were surveyed to determine whether and why they collected R/E data. RESULTS: Race was reported in 156 of 228 articles (68%), but discussed in only one-third (75). Although there is wide interjournal variability, there was little change between the two periods. Seventy-two percent of respondents thought that R/E was or might be relevant to their research, and this influenced their decision to report and discuss R/E. CONCLUSIONS: Most researchers report R/E and believe it is relevant to their research. Despite policies that reject R/E as explanatory variables, most researchers do not report or discuss the underlying social mechanisms that may explain R/E differences.