Modeling Water Quality in Watersheds: From Here to the Next Generation.

In this synthesis, we assess present research and anticipate future development needs in modeling water quality in watersheds. We first discuss areas of potential improvement in the representation of freshwater systems pertaining to water quality, including representation of environmental interfaces, in-stream water quality and process interactions, soil health and land management, and (peri-)urban areas. In addition, we provide insights into the contemporary challenges in the practices of watershed water quality modeling, including quality control of monitoring data, model parameterization and calibration, uncertainty management, scale mismatches, and provisioning of modeling tools. Finally, we make three recommendations to provide a path forward for improving watershed water quality modeling science, infrastructure, and practices. These include building stronger collaborations between experimentalists and modelers, bridging gaps between modelers and stakeholders, and cultivating and applying procedural knowledge to better govern and support water quality modeling processes within organizations.

Human spermicidal activity of inorganic and organic oxidants.

OBJECTIVE: To identify prospective oxidants that rapidly immobilize human sperm upon contact with human semen. DESIGN: Inorganic, organic, and enzymatically-generated oxidants were mixed with human semen and spermicidal activity was tracked by a modified Sander-Cramer assay. SETTING: Commercial and university-based laboratories. PATIENT(S): Semen samples obtained through a university-based andrology laboratory. INTERVENTION(S): Not applicable. MAIN OUTCOME MEASURE(S): Quantitation of spermicidal activity of test oxidants. RESULT(S): Sperm lost motility within 20 seconds of exposure to enzymatically generated free iodine (I(2)). Toluidine blue, phenazine methosulfate, or methylene blue exhibited some, albeit much less, spermicidal activity. Oxidants formed by mixing ascorbic acid with Fe(III)-EDTA, xanthine with xanthine oxidase, or by exposing sperm to the nitric oxide generator, SIN-1 (3-morpholinosydnonimine hydrochloride), were far less potent spermicidal agents. CONCLUSION(S): Free I(2) formed in situ and presented to semen is an extremely potent spermicide. Additional studies on methods of generating de novo I(2) may be beneficial in developing a novel new class of nondetergent-based spermicides.

Comparison of the response of three human monocytic cell lines to challenge with polyethylene particles of known size and dose.

The response of three human monocytic cell lines (Monomac-1, U937 and THP-1) to challenge with polyethylene particles of known size and dose was evaluated. Particles with a mean size of 0.21, 0.49, 4.3, 7.2, and 88 microm were co-cultured with the cells for 24 hours prior to the assessment of cell viability and production of the pro-inflammatory cytokines, IL-1beta, IL-6 and TNFalpha. Additionally, GM-CSF and prostaglandin E2 were measured in culture supernatants from particle stimulated U937 cells. All particle fractions were evaluated at particle volume (microm3) to cell number ratios of 100 : 1, 10 : 1, 1 : 1 and 0.1 : 1. None of the test fractions had any effect on cell viability. Only the response of the U937 cell line was demonstrated to be comparable to that of primary macrophages as determined in a previous study. Furthermore only particle volume to cell number ratios of 10 : 1 or greater consistently stimulated significantly enhanced levels of cytokine secretion with particles within the phagocytosable size range (0.1 to 10 microm) being the most biologically active. No response was observed when U937 macrophages were stimulated with the largest (88 microm) particles at any of the volume ratios tested in this study. These results suggest that the size and volume of polyethylene particles are critical factors in macrophage activation. In addition, the U937 cell line has been shown to be a suitable model for the in vitro study of macrophage-particle interactions.

Effect of size and dose on bone resorption activity of macrophages by in vitro clinically relevant ultra high molecular weight polyethylene particles.

Polyethylene wear debris generated at the bearing surfaces of total artificial hip joints is thought to play an important role in the periprosthetic osteolysis and ultimately the aseptic loosening of these prostheses. The macrophage is believed to be central to this process by releasing various cytokines and other mediators of osteolysis upon phagocytosis of the polyethylene wear debris. This study evaluated the in vitro bone resorption response of C3H murine peritoneal macrophages to clinically relevant GUR 1120 polyethylene particles. Macrophages were co-cultured in vitro with GUR 1120 particles with a mean size of 0.24, 0.45, 1.71, and 7.62, and GUR 1120 polyethylene resin with a mean size of 88 microm at various particle volume (microm)(3): macrophage ratios (0.1:1; 1:1; 10:1; and 100:1). The conditioned supernatants were incubated with (45)calcium radio-labeled mouse calvariae, and bone resorption was measured as (45)calcium release. The results showed that the 0.24 microm particles stimulated the macrophages to generate bone resorbing activity at a ratio of 10(microm)(3) per macrophage. The 0.45 and 1.71 microm particles were active at a ratio of 100( microm)(3) per macrophage, and the 7.62 and 88 microm particles were inactive at all the doses tested. The co-culture supernatants were also assayed for TNF-alpha, IL-1beta, IL-6, and PGE(2). The results followed the same trend for particle size and volume dose to that observed for the bone resorbing activity. This study has demonstrated, for the first time, the importance of size and dose of clinically relevant polyethylene particles on the osteolytic response of macrophages in vitro.

Comparison of the response of primary human peripheral blood mononuclear phagocytes from different donors to challenge with model polyethylene particles of known size and dose.

The response of primary human peripheral blood mononuclear phagocytes to challenge with polyethylene particles of known size and dose was evaluated. Particles with mean sizes of 0.21, 0.49, 4.3, 7.2, and 88 microm were co-cultured with cells for 24 h prior to the assessment of cell viability and production of the osteolytic mediators IL-1beta, IL-6, TNFalpha, GM-CSF and PGE2. All particle fractions were evaluated at particle volume (microm3) to cell number ratios of 10:1 and 100:1 which were previously identified as being the most biologically active and clinically relevant. The heterogeneity of human individuals was clearly evident both in the profile and the magnitude of the response of the donors evaluated in this study (the response of donor 5 being 2- to 15-fold lower than that of the other donors). Only the sub-micrometre particles stimulated significantly enhanced cytokine secretion at the ratios tested: mean particle sizes of 0.49 and 0.21 microm being the most biologically active. Macrophages stimulated with particles outside this size range produced considerably lower levels of mediator. These results compared favourably with the results of earlier studies, which demonstrated that particles within the phagocytosable size range (0.1-10 microm) were the most biologically active. These results, therefore, confirm earlier findings and suggest that the size and volume of polyethylene particles are critical factors in macrophage activation. Furthermore, they suggest that the heterogeneity of human individuals may be another important factor in determining implant life and could provide the basis for a valuable diagnostic tool to identify those patients most at risk of implant loosening.

Evaluation of the response of primary human peripheral blood mononuclear phagocytes to challenge with in vitro generated clinically relevant UHMWPE particles of known size and dose.

The response of primary human peripheral blood mononuclear phagocytes to challenge with clinically relevant ultra-high molecular weight polyethylene (UHMWPE) wear debris of known particle size and dose was evaluated. Particles with a mean size of 0.24, 0. 45, 1.7, 7.6, and 88 microm were cocultured with cells for 24 h before assessment of cell viability and production of the osteolytic cytokines interleukin (IL)-1 beta, IL-6, tumor necrosis factor-alpha, and granulocyte macrophage colony-stimulating factor, and prostaglandin E(2). All particle fractions were evaluated at particle volume (microm(3)) to cell number ratios of 10:1 and 100:1, which had been previously identified as being the most stimulatory and clinically relevant. None of the test fractions had an effect on cell viability. Whereas the heterogeneity of human individuals was clearly evident in the responses of the donors evaluated in this study (the response of donor 3 was between 5 and 20 times greater than the other donors), the most biologically active particles were found to be submicrometer in size. Stimulation with phagocytosable particles (0.24, 0.45, and 1.7 microm) resulted in enhanced levels of cytokine secretion. Macrophages stimulated with particles outside this size range produced considerably less cytokines at the volumes tested. These results confirm earlier findings and suggest that the size and volume of UHMWPE particles are critical factors in macrophage activation. Furthermore, they suggest that the heterogeneity of human individuals may be another important factor in determining implant life.

Production of TNF-alpha and bone resorbing activity by macrophages in response to different types of bone cement particles.

We have compared the capacity of clinically relevant wear debris from seven different cement types to activate macrophages to produce TNF-alpha, IL-1beta, IL-6 and bone resorbing activity in vitro. The bone cements were: CMW 1 original (PMMA only); CMW 1RO (1 microm BaSO4; 9.2%); CMW copolymer bone cement 1 (10 microm BaSO4; 10%); CMW copolymer bone cement 2 (1 microm BaSO4; 10%); Palacos R (10 microm ZrO2; 15.6%); CMW Calcium phosphate cement 20% (10 microm tri-calcium phosphate; 20%) and CMW calcium phosphate cement 30% (10 microm tri-calcium phosphate; 30%). Cement debris was produced aseptically using a simple configuration wear test. The majority of particles were in the size range 0.1-0.5 microm for each cement type. The cement particles were co-cultured with the U937 macrophage cell line at ratios of 10 and 100 microm3 particle volumes to macrophage cell numbers for 24 h. At the 10:1 ratio the particles had no effect on the cells. At the 100:1 ratio, the major cytokine produced was TNF-alpha and there were no statistical differences between the different types of cement debris. The bone resorption activity of the co-culture supernatants was significantly greater than the control (U937 cells without particles) for particles of CMW 1RO, CMW copolymer bone cement 1, CMW copolymer bone cement 2 and Palacos R (P < 0.05, ANOVA). However there were no statistical differences between the levels of bone resoprtion evoked by these four cement types. The CMW1 original and CMW calcium phosphate containing cements failed to induce the macrophages to elaborate bone resorption activity at the 100:1 ratio. These data suggest that the addition of radio-opaque additives to bone cement may increase the capacity of the debris to induce osteolysis.

Comparison of the response of primary murine peritoneal macrophages and the U937 human histiocytic cell line to challenge with in vitro generated clinically relevant UHMWPE particles.

The response of primary murine macrophages and the U937 human histiocytic cell line to challenge with clinically relevant UHMWPE wear debris of known particle size and dose was evaluated. Particles with mean sizes of 0.24, 0.45, 1.71, 7.62 and 88 microm were co-cultured with cells for 24 hours prior to assessment of cell viability and production of the osteolytic mediators IL-1beta, IL-6, TNFalpha and, in supernatants from murine phagocytes, PGE2 and GM-CSF. All particle fractions were evaluated at particle volume (microm3) to cell number ratios of 10 : 1 and 100 : 1 (and, additionally, 0.1 : 1 and 1 : 1 for U937 cells). These ratios had previously been identified as the most stimulatory and clinically relevant. Although the results for the cell line were highly variable, stimulation with phagocytosable particles (range 0.1 to 15 microm) resulted in enhanced levels of cytokine secretion by both murine macrophages and U937 histiocytes. The most biologically active particles were sub-micrometre in size. However, U937 cells responded to wear debris at much lower particle volume to cell number ratios (>0.1 microm3 per cell) than the murine cells (> 10 microm3 per cell). No GM-CSF was produced by particle or LPS stimulated murine macrophages. Similarly, U937 histiocytes failed to secrete any IL-1beta. Neither macrophage population responded to stimulation with the largest (88 microm) particles. These results confirm earlier findings and suggest that the size of UHMWPE wear particles is a critical factor in macrophage activation. Moreover, primary murine macrophages have been demonstrated to be a suitable model for studying cell-particle interactions in vitro.

Serum digoxin in the presence of digibind: determination of digoxin by the Abbott AxSYM and Baxter Stratus II immunoassays by direct analysis without pretreatment of serum samples.

We have reevaluated the feasibility of using direct immunochemical methods to track free digoxin in patients receiving Digibind. We report here that results obtained by the Stratus II and AxSYM immunoassays on patients receiving digoxin (without Digibind), digoxin-fortified serum samples supplemented with Digibind, and a digitoxic patient treated with Digibind, show no clinically significant biases. We conclude that useful free digoxin concentrations may be obtained for Digibind-treated patients using either the AxSYM or Stratus immunoassays without subjecting samples to ultrafiltration before analysis.

Polyethylene particles of a 'critical size' are necessary for the induction of cytokines by macrophages in vitro.

Particulate wear debris from total hip prosthetic components can stimulate macrophages to produce mediators of osteolysis which may cause aseptic implant loosening. This study evaluated the in vitro response of murine peritoneal macrophages to polyethylene particles of definitive size distributions at varying volume doses. Ceridust 3615 polyethylene particles with a mean size of 0.21, 0.49, 4.3 and 7.2 microm and GUR 120 polyethylene resin with a mean size of 88 microm were co-cultured with C3H murine peritoneal macrophages at volume (microm)3 to cell number ratios of 100:1, 10:1, 1:1 and 0.1: 1. The secretion of IL-6, IL-1beta and TNF-alpha was determined by ELISA. Significantly elevated levels of TNF-alpha and IL-1beta were determined at 100:1 ratios when the macrophages were challenged with particles with a mean size of 0.49, 4.3 and 7.2 microm, and at 10:1 ratios for particles with a mean size of 0.49 and 4.3 microm. IL-6 production was significantly elevated at 100:1 ratios for mean particle sizes of 0.49 and 4.3 microm. Particles outside this range produced considerably less cytokine suggesting that both the size and volume (or number) of polyethylene particles are critical factors in macrophage activation. Therefore particles in the phagocytosable size range of 0.3-10 microm appear to be the most biologically active.

Beta-carotene in HIV infection: an extended evaluation.

OBJECTIVE: Several small short-term intervention studies have suggested that beta-carotene supplementation in HIV-infected patients can increase the number of various immune cells including CD4 cells. This prospective double-blinded study was designed to investigate whether beta-carotene supplementation would result in this immuno-enhancement in a larger number of patients over a longer time period. METHODS: HIV-positive patients were randomly assigned to receive either 60 mg beta-carotene orally three times daily or a matched placebo. In addition, all patients received a multivitamin supplement. Patients were evaluated at baseline, 1 month, and 3 months for T-cell quantitative subsets, natural killer cells, HIV p24 antigen, beta-carotene levels, complete blood counts and chemistry batteries. Body weights and Karnofsky scores were evaluated at each visit. RESULTS: Seventy-two patients signed informed consent forms and entered the study. Except for serum beta-carotene concentration, there were no statistically significant differences (P < 0.05) between the treatment (60 mg beta-carotene three times daily and multivitamins) and placebo (placebo and multivitamins) groups at baseline or after either 1 or 3 months of treatment. DISCUSSION: Earlier studies suggesting that beta-carotene supplementation increased levels of immune cells in HIV-infected patients were not replicated in this study. The addition of a multivitamin supplement to both arms of this study may have masked any difference between the two groups. However, on the basis of the results of this study, we would not recommend supplementation with high doses of beta-carotene for HIV-infected patients.

Specificity and properties of propofol as an antioxidant free radical scavenger.

The active component of the anesthetic propofol (2,6-diisopropylphenol), which structurally resembles butylated hydroxy-toluene (BHT), a known free radical scavenger, was examined and compared to BHT with regard to its dose-dependent radical scavenging activity. Studies on the ameliorating effect of propofol in inhibiting radical production revealed that it preferentially scavenges organoradical species. In aqueous suspension it is more efficient than BHT as a free radical scavenger of riboflavin radicals and in blocking formation of malondialdehyde degradation products generated from lipid hydroperoxides of arachidonic acid. Neither propofol nor BHT showed any radical scavenging activities at concentration ranges less than 10 micrograms/ml. Propofol quenched radicals generated by photoillumination of riboflavin by 50% at 30 micrograms/ml. Under the same conditions BHT still showed no radical scavenging activity. At 50 micrograms/ml propofol the formation of malondialdehyde degradation products of arachidonic acid formed by illuminating arachidonic acid in test mixtures containing riboflavin was decreased by 38% compared to a decrease of only 24% with BHT substituted in place of propofol. The concentration of propofol required to ameliorate free radicals is approximately an order of magnitude higher than therapeutic doses of propofol used in anesthesia, suggesting that its scavenging activity during anesthesia is likely very limited.

Early CK-MB elevations predict ischemic events in stable chest pain patients.

OBJECTIVE: To demonstrate that creatine kinase-MB fraction (CK-MB) elevations within three hours of presentation in the emergency department (ED) are associated with subsequent ischemic events in clinically stable chest pain patients. METHODS: Prospective cohort study at two university- affiliated teaching hospitals. Participants were consenting ED chest pain patients 25 years old or older without evidence of rhythm or hemodynamic instability (n = 449). Exclusions included ST-segment elevation > or = 0.1 mV in > or = 2 electrocardiogram leads, chest wall trauma, abnormal x-ray studies, and incomplete data collection. Measurements included presenting and three-hour CK-MB levels, presenting ECG, initial clinical impression of coronary care unit need, and clinical follow up. Monitored adverse events included myocardial ischemia necessitating coronary angioplasty or cardiac bypass surgery, recurrent in-hospital myocardial infarction, bradycardia requiring pacing, emergent cardioversion, cardiogenic shock, ventricular fibrillation, and death. RESULTS: Overall, nine (2%) of 449 patients experienced an ischemic event within the first 48 hours. All nine patients required either coronary angioplasty or bypass surgery. Four (44%) of the nine patients with 48-hour ischemic events had elevated CK-MB levels. Of 23 patients who had complications within one week of ED presentation, seven (30%) had elevated ED CK-MB levels. An elevated CK-MB level was associated with an ischemic event both within 48 hours (risk ratio 9.5; 95% CI 2.7-33.7) and within one week (risk ration 5.2; 95% CI 2.3-11.7). CONCLUSIONS: An elevated CK-MB level within three hours of ED presentation is associated with a subsequent ischemic event in the clinically stable chest pain patient without ST-segment elevation. However, the ED CK-MB identifies only a minority or otherwise low-risk patients who develop ischemic events; other markers for diagnosing myocardial ischemia in the ED are needed.

The role of single ECG, creatinine kinase, and CKMB in diagnosing patients with acute chest pain.

The objective of this study was to determine the combined accuracy of emergency department (ED) cardiac enzymes and electrocardiograms (ECGs) in patients who were admitted to "rule-out" myocardial infarction (ROMI). A retrospective analysis of ED creatinine kinase (CK), CKMB, and ECG was performed and the results were compared with final hospital diagnosis of MI, in the ED of a medical school- and university hospital-affiliated teaching Veterans Affairs Medical Center. Approximately 222 consecutive ED patients admitted to ROMI, including 43 (19%) MI patients, 29 (67%) of whom presented to the ED within 24 hours of symptom onset were eligible to participate. Interventions included an analysis of CK and CKMB results and ECG findings. There were no statistical differences in the sensitivities, specificities, and predictive values when the two cardiac enzymes were compared. Almost all of the elevated cardiac enzyme results occurred in MI patients who presented within 24 hours of symptom onset, more than half of whom had ED cardiac enzyme elevations. For all MI patients, regardless of duration of symptoms, more than half of the ED ECGs had new ST-T changes consistent with an acute MI or acute myocardial ischemia. In the MI patients who presented within 24 hours of symptom onset, 79% had positive enzymes or ECG or both in the ED. No statistically significant difference in the sensitivity rates for MI between the CK and CKMB comparing enzymes with ECGs was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Theophylline in oral mucosal transudate. A practical method for monitoring outpatient therapy.

We tested the utility of a novel collection system that allows measurement of theophylline in oral mucosal transudate (OMT) to calculate serum theophylline concentrations. In 25 adult patients, theophylline levels in OMT correlated better than expectorated saliva with serum theophylline (r = 0.927 for OMT versus r = 0.831 for expectorated saliva, each p < 0.0001). In a subsequent study of 128 patients (118 adults and 10 children aged 4 to 12 yr), OMT and serum theophylline were measured and polynomial regression analysis performed to allow calculation of serum level for any given OMT level. Theophylline levels calculated from OMT values closely followed measured serum theophylline in two normal subjects after administration of either intravenous or oral theophylline. OMT samples collected by 24 patients at home were mailed to the laboratory for testing. Theophylline values from the home collection samples correlated closely (r = 0.930, p < 0.0001) with serum theophylline levels obtained at the same dose of theophylline. These findings suggest that once the relationship of serum to OMT theophylline is established in a given laboratory, the latter can be used to monitor outpatient theophylline therapy in adults (and possibly children) at times of the day otherwise inaccessible to serum sampling.

Stoichiometry of O2 metabolism and NADPH oxidation of the cell-free latent oxidase reconstituted from cytosol and solubilized membrane from resting human neutrophils.

The stoichiometry of NADPH-dependent O2 consumption expressed by reconstituted latent oxidase obtained by combining cytosol and membrane fractions from resting human neutrophils with GTP gamma S and SDS in a cell-free assay was evaluated with regard to NADPH consumed and superoxide and H2O2 production. Oxidase activity monitored simultaneously by O2 uptake analysis using a Clark cell and O2 electrode for O2 consumption, and spectrally at 340 nm for NADPH oxidation, in the presence of excess superoxide dismutase and catalase, yielded an O2 uptake: NADPH consumption ratio of 0.51 +/- 0.04 (+/- 1 S.D., n = 6). In the presence of varying concentrations of ferricytochrome c in excess of 100 microM, and with exclusion of superoxide dismutase, the net rate of O2 consumption plateaued at approximately 6% of the rate seen with exclusion of ferricytochrome c from final assay mixtures. Cytosol and solubilized membrane fractions employed in these assays were devoid of endogenous superoxide trapping, or dismutase-like, activities. These results indicate that of the total O2 consumed, 94% is associated with direct univalent generation of superoxide. The remaining albeit low level of O2 consumption appears to be recovered in the form of H2O2 indicating that the cell-free oxidase reconstituted with SDS is capable of channeling electron equivalents through its redox sites in a highly controlled manner in ensuring that superoxide is its principal O2 reduction product concomitant with oxidation of NADPH.

Serial ECGs are less accurate than serial CK-MB results for emergency department diagnosis of myocardial infarction.

HYPOTHESIS: Serial creatine kinase-MB (CK-MB) levels provide more accurate predictive information regarding myocardial infarction than serial ECGs in emergency department patients with chest discomfort and no ST-segment elevation on the initial ECG. DESIGN: Prospective, observational study. SETTING: University hospital and university-affiliated Veterans Affairs Medical Center EDs. PARTICIPANTS: Two hundred sixty-one patients 30 years or older with chest discomfort warranting an ECG and consenting to observation. Exclusions included hemodynamic or rhythm instability and ST-segment elevation of 0.1 mV or more in two or more electrically contiguous leads at presentation. MEASUREMENTS: ECGs were obtained at presentation and three to four hours after presentation. Significant serial ECG changes sought on comparison of initial and three- to four-hour ECGs were 0.05 mV or more ST elevation or depression, Q-wave development, or T-wave inversion changes in two or more electrically contiguous leads. CK-MB levels were obtained at presentation and hourly for three hours (positive level, 8 or more ng/mL). Myocardial infarction was determined by record review and was based on independent CK-MB measurements. RESULTS: Twenty-eight (11%) patients were diagnosed with a myocardial infarction. Thirty-eight (15%) patients had a serial ECG change. Eleven of the myocardial infarction patients (39%) had a serial ECG change compared with 27 (12%) of the non-myocardial infarction patients (P < .001). Sensitivities and specificities of a serial ECG change versus serial CK-MBs for myocardial infarction were 39% versus 68% (sensitivity) and 88% versus 95% (specificity), respectively. Serial CK-MBs were more accurate than a serial ECG change for predicting myocardial infarction (P < .03). CONCLUSION: Serial changes in ECGs during a three- to four-hour interval were associated with the diagnosis of myocardial infarction but were infrequent and less accurate than serial CK-MB levels obtained for the same interval.