Phosphorus storage and utilization strategies of two bloom-forming freshwater cyanobacteria.

The inter-relationships between cellular phosphorus (P) storage, dissolved inorganic P (DIP) uptake affinity, alkaline phosphatase activity (APA) and dissolved inorganic nitrogen (DIN) concentrations were studied in two ubiquitous diazotrophic freshwater cyanobacteria, Raphidiopsis raciborskii (six strains) and Chrysosporum ovalisporum (two strains). DIP uptake kinetics were measured using rates of incorporation of the radio-isotope, 33P and APA as a proxy for DOP-ester utilization. The study showed that DIP uptake of individual strains followed Michaelis-Menten kinetics (modified in our study to incorporate cellular P quotas), but differed with DIN and P availability, and between growth stages. High-affinity DIP uptake and APA were activated below a P quota threshold of approximately 0.01 µg P µg-1 C across the species and strains. C. ovalisporum had significantly higher APA and P quotas (per unit C and cell) but lower uptake affinity than R. raciborskii. Demand for DIP by C. ovalisporum increased when N fixation occurred, but typically not for R. raciborskii. Our results indicate that cyanobacterial species and strains differ in their strategies to P limiting conditions, and highlight the interplay between N and P. Physiological adaptations like APA and diazotrophy of cyanobacteria adapting to low DIP and/or DIN conditions may occur simultaneously and drive species dominance in oligotrophic environments.

Schindler's legacy: from eutrophic lakes to the phosphorus utilization strategies of cyanobacteria.

David Schindler and his colleagues pioneered studies in the 1970s on the role of phosphorus in stimulating cyanobacterial blooms in North American lakes. Our understanding of the nuances of phosphorus utilization by cyanobacteria has evolved since that time. We review the phosphorus utilization strategies used by cyanobacteria, such as use of organic forms, alternation between passive and active uptake, and luxury storage. While many aspects of physiological responses to phosphorus of cyanobacteria have been measured, our understanding of the critical processes that drive species diversity, adaptation and competition remains limited. We identify persistent critical knowledge gaps, particularly on the adaptation of cyanobacteria to low nutrient concentrations. We propose that traditional discipline-specific studies be adapted and expanded to encompass innovative new methodologies and take advantage of interdisciplinary opportunities among physiologists, molecular biologists, and modellers, to advance our understanding and prediction of toxic cyanobacteria, and ultimately to mitigate the occurrence of blooms.

The bicipital groove as a landmark for humeral version reference during shoulder arthroplasty: a computed tomography study of normal humeral rotation.

BACKGROUND: Accurate reproduction of humeral version is important in shoulder arthroplasty. Traditional referencing relative to the transepicondylar axis (TEA) is prone to error as it is absent on preoperative imaging and inaccurately reproduced intraoperatively. The bicipital groove is present on preoperative imaging and in the operative field and thus may be a useful landmark for accurate reproduction of humeral version. MATERIALS AND METHODS: Two trained observers analyzed 101 full-humerus computed tomography scans of patients undergoing a myeloma screening protocol. Measurements of humeral retroversion relative to the TEA (angle A), humeral articular axis retroversion relative to the bicipital groove (angle B), and the bicipital groove axis relative to the TEA (angle C) were made with comparison of the measurement properties of each. RESULTS: Humeral retroversion relative to the TEA was 23.7° ± 8° (range, 0.2°-48.7°; 95% confidence interval, 22°-26°). The humeral articular axis was retroverted to the bicipital groove axis (angle B) by 33.5° ± 9.4° (range, 15.5°-61.7°; 95% confidence interval, 32°-35°). Overall inter-rater reliability was 0.88. DISCUSSION: Measurement of humeral head retroversion relative to the bicipital groove is not inferior to the gold-standard measurement. The bicipital groove is present both on preoperative imaging and in the operative field, making it a potential reference landmark for accurate reproduction of humeral version in shoulder arthroplasty.

Migration of Patients for Liver Transplantation and Waitlist Outcomes.

BACKGROUND & AIMS: Patients in need of liver transplantation may travel to improve their chance of receiving an organ. We evaluated factors to determine which transplant candidates travel to other regions to increase their chances of receiving a liver and effects of travel on waitlist outcomes. METHODS: We performed a retrospective cohort study of all adult patients registered for primary deceased donor liver transplantation in the United States from January 2004 to December 2016. Zip code data were used to calculate the travel distance from a patient's residence to centers at which they were on the waitlist or received a liver transplant. Distant listing and migration were defined as placement on a waitlist and receipt of liver transplantation, respectively, outside the home transplantation region and greater than 500 miles from the home zip code. We assessed the effect of distant listing on outcomes (death and liver transplantation) and predictors of distant listing or migration using multivariable analyses. RESULTS: There were 104,914 waitlist registrations during the study period; of these, 2930 (2.8%) pursued listing at a distant center. Of waitlist registrants, 60,985 received liver transplants, of whom 1985 (3.3%) had migrated. In a multivariable competing risk analysis in which liver transplantation was considered as a competing event, distant listing was associated with a 22% reduction in the risk of death within 1 year (subhazard ratio, 0.78; 95% CI, 0.70-0.88). Distant listing and migration were associated with non-black race, non-Medicaid payer, residence in a higher income area, and education beyond high school. CONCLUSIONS: Placement on a liver transplant waitlist outside the home transplantation region is associated with reduced waitlist mortality and an increased probability of receiving a liver transplant. Geographic disparities in access to liver transplantation have disproportionate effects on patients who are minorities, have lower levels of education, or have public insurance.

C-peptide levels do not correlate with pancreas allograft failure: Multicenter retrospective analysis and discussion of the new OPT definition of pancreas allograft failure.

The OPTN Pancreas Transplantation Committee performed a multicenter retrospective study to determine if undetectable serum C-peptide levels correspond to center-reported pancreas graft failures. C-peptide data from seven participating centers (n = 415 graft failures for transplants performed from 2002 to 2012) were analyzed pretransplant, at graft failure, and at return to insulin. One hundred forty-nine C-peptide values were submitted at pretransplant, 94 at return to insulin, and 233 at graft failure. There were 77 transplants with two available values (at pretransplant and at graft failure). For recipients in the study with pretransplant C-peptide <0.75 ng/mL who had a posttransplant C-peptide value available (n = 61), graft failure was declared at varying levels of C-peptide. High C-peptide values at graft failure were not explained by nonfasting testing or by individual center bias. Transplant centers declare pancreas graft failure at varying levels of C-peptide and do not consistently report C-peptide data. Until February 28, 2018, OPTN did not require reporting of posttransplant C-peptide levels and it appears that C-peptide levels are not consistently used for evaluating graft function. C-peptide levels should not be used as the sole criterion for the definition of pancreas graft failure.

Evaluation of respiratory symptoms and respiratory protection behavior among poultry workers in small farming operations.

Agricultural workers who work in enclosed poultry operations are at increased risk of respiratory exposure to atmospheric contaminants, including dusts, endotoxins, particulate from feathers, ammonia, and hydrogen sulfide from animal excrement. Given the relatively large number of small, family-run poultry farms in North Carolina, there has been relatively little research in the area documenting human lung function and perception of using respiratory protection among poultry workers. This study assesses respiratory health, knowledge, and perception of wearing respiratory protection among a sample of poultry workers attending a regional farm show in North Carolina. Lung function (spirometry), airway inflammation (exhaled nitric oxide), self-reported respiratory symptoms, and behavior of wearing respiratory protection were evaluated. Overall, mean lung function values were slightly lower than normal predicted values. The majority of participants ranked using respiratory protection as very important (51.9%); however, actual self-reported behavior was low (16.7%). In bivariate analysis, associations between the importance of wearing respiratory protection and the number of poultry houses (P=.04), as well as using a respirator and the number of poultry houses (P=.01) were statistically significant. Improved educational opportunities, including fit-testing and proper respiratory selection, should be emphasized for workers at small, poultry farm operations.