Unbiased Measurement of Phosphate and Phosphorus Speciation in Surface Waters.

Trace-level phosphate analysis and phosphorus speciation in surface water remained challenging due to adsorption and phosphate uptake by microorganisms. In this study a two-dimensional ion chromatography separation coupled to electrospray ionization high-resolution mass spectrometry (2D-IC-ESI-MS) allowed isotope dilution quantitation of phosphate with simultaneous analysis of 11 phosphate-containing metabolites and two inorganic condensed phosphates. Samples were collected from Lake St. Clair, Lake Ontario, and Georgian Bay (ON, Canada). Comparative experiments showed lower phosphate results for samples not immediately spiked and for external calibration quantitation. Field spiking with 18O-labeled phosphate combined with isotope dilution quantitation allows measurement of the phosphate levels existent at the collection time instead of the phosphate concentrations remaining in the samples at the analysis time. This is a significant advantage against the traditional colorimetric and ion chromatographic (IC) analysis methods, which are unable to compensate for the adsorption loss occurring in standards and samples, especially when phosphate is present at levels below 20 µg L-1 as P (61 µg L-1 as PO43-). Two phosphate-containing metabolites, adenosine 5'-monophosphate (AMP) and d-glucose 6-phosphate (Glucose-P), were detected in a subset of samples collected from Lake St. Clair, with no statistically significant correlation between them and the simultaneously measured phosphate. Directly bioavailable P (phosphate), indirectly bioavailable P (phosphatase-hydrolyzed P) and nonbioavailable P (nonhydrolizable P) fractions were quantified by measuring phosphate, phosphate after phosphatase addition and total phosphorus. The proposed 2D-IC-ESI-MS method developed for a QExactive MS instrument with field spiking of the internal standard provides accurate phosphate results and eliminates quantitation errors caused by phosphate adsorption. This setup allows simultaneous collection of targeted and nontargeted analysis data and thus the detection of trace polar organic phosphorus metabolites as well.

Phosphorus-based metabolic pathway tracers in surface waters.

Trophic status in surface waters has been mostly monitored by measuring soluble reactive phosphorus (SRP) and total phosphorus (TP). Additional to these common parameters, a two-dimensional ion chromatography mass spectrometry (2D-IC-MS) method was used to simultaneously measure soluble phosphate (Pi), pyrophosphate (PPi), and eleven phosphate-containing metabolites (P-metabolites) in Lake Ontario and its tributaries. From the additional P species, PPi, adenosine 5'-monophosphate (AMP), glucose 6-phosphate (G-P), D-fructose 6-phosphate (F-P), D-fructose 1,6-biphosphate (F-2P), D-ribulose 5-phosphate (R-P), D-ribulose 1,5-bisphosphate (R-2P), and D-(-)-3-phosphoglyceric acid (PGA) were detected and quantified in the lake and river samples. The additional multivariate statistical analysis identified similarities between samples collected at different locations. The presence of R-P, R-2P, and F-2P in Lake Ontario tributaries seems to be mainly related to the Calvin cycle, while the lack of all these three P-metabolites and higher PGA levels than G-P in Toronto Harbour samples seems to be the result of depleted Calvin cycle, pentose phosphate, and glycolysis metabolic pathways.

Gallstone disease in heart transplant recipients.

OBJECTIVE: To review the outcome of cholecystectomy after heart transplant. SUMMARY BACKGROUND DATA: The optimal timing for gallbladder surgery in heart transplant patients is controversial. METHODS: Between April 1985 and October 2000, 518 cardiac transplants were performed at Ochsner Foundation Hospital. Data gathered included ultrasound reports, cholecystectomy operative reports, gallbladder pathologic reports, complications, and deaths. RESULTS: Charts were available for 509 patients (98%), 68 (13%) of whom underwent cholecystectomy before transplantation. Of the 509, 53 (10%) had serial ultrasound examinations and 29 of the 53 (55%) developed gallstones. After transplant, 47 (9%) underwent cholecystectomy. Five cholecystectomies were performed during the immediate postoperative course. Two patients who underwent cholecystectomy had acalculous cholecystitis; one was incidental. Four patients died (one with rejection and three with sepsis). After discharge, 42 cholecystectomies were performed: 16 for biliary colic (no deaths, three patients with complications), 19 for acute cholecystitis (one death, nine patients with complications), 5 for biliary pancreatitis (1 death, 1 patient with complications), and 2 others. CONCLUSIONS: The risk of morbidity and mortality from gallstone disease is high in cardiac transplant patients, particularly immediately posttransplant. Posttransplant patients require annual ultrasound examinations to detect the onset of gallstone disease, and this risk is higher than in the general population. Gallstones alone are an indication for cholecystectomy in the cardiac transplant patient. Pretransplant cholecystectomy should be considered in clinically stable patients with gallstones.