Chronic nutrient inputs affect stream macroinvertebrate communities more than acute inputs: An experiment manipulating phosphorus, nitrogen and sediment.

Freshwaters worldwide are affected by multiple stressors. Timing of inputs and pathways of delivery can influence the impact stressors have on freshwater communities. In particular, effects of point versus diffuse nutrient inputs on stream macroinvertebrates are poorly understood. Point-source inputs tend to pose a chronic problem, whereas diffuse inputs tend to be acute with short concentration spikes. We manipulated three key agricultural stressors, phosphorus (ambient, chronic, acute), nitrogen (ambient, chronic, acute) and fine sediment (ambient, high), in 112 stream mesocosms (26 days colonisation, 18 days of manipulations) and determined the individual and combined effects of these stressors on stream macroinvertebrate communities (benthos and drift). Chronic nutrient treatments continuously received high concentrations of P and/or N. Acute channels received the same continuous enrichment, but concentrations were doubled during two 3-hour periods (day 6, day 13) to simulate acute nutrient inputs during rainstorms. Sediment was the most pervasive stressor in the benthos, reducing total macroinvertebrate abundance and richness, EPT (mayflies, stoneflies, caddisflies) abundance and richness. By contrast, N or P enrichment did not affect any of the six studied community-level metrics. In the drift assemblage, enrichment effects became more prevalent the longer the experiment went on. Sediment was the dominant driver of drift responses at the beginning of the experiment. After the first acute nutrient pulse, sediment remained the most influential stressor but its effects started to fade. After the second pulse, N became the dominant stressor. In general, impacts of either N or P on the drift were due to chronic exposure, with acute nutrient pulses having no additional effects. Overall, our findings imply that cost-effective management should focus on mitigating sediment inputs first and tackle chronic nutrient inputs second. Freshwater managers should also take into account the length of exposure to high nutrient concentrations, rather than merely the concentrations themselves.

Multiple-stressor effects of sediment, phosphorus and nitrogen on stream macroinvertebrate communities.

Multiple stressors affect stream ecosystems worldwide and their interactions are of particular concern, with gaps existing in understanding stressor impacts on stream communities. Addressing these knowledge gaps will aid in targeting and designing of appropriate mitigation measures. In this study, the agricultural stressors fine sediment (ambient, low, medium, high), phosphorus (ambient, enriched) and nitrogen (ambient, enriched) were manipulated simultaneously in 64 streamside mesocosms to determine their individual and combined effects on the macroinvertebrate community (benthos and drift). Stressor levels were chosen to reflect those typically observed in European agricultural streams. A 21-day colonisation period was followed by a 14-day manipulative period. Results indicate that added sediment had the most pervasive effects, significantly reducing total macroinvertebrate abundance, total EPT abundance and abundances of three common EPT taxa. The greatest effect was at high sediment cover (90%), with decreasing negative impacts at medium (50%) and low (30%) covers. Added sediment also led to higher drift propensities for nine of the twelve drift variables. The effects of nitrogen and phosphorus were relatively weak compared to sediment. Several complex and unpredictable 2-way or 3-way interactions among stressors were observed. While sediment addition generally reduced total abundance at high levels, this decrease was amplified by P enrichment at low sediment, whereas the opposite effect occurred at medium sediment and little effect at high sediment. These results have direct implications for water management as they highlight the importance of managing sediment inputs while also considering the complex interactions which can occur between sediment and nutrient stressors.

Polypoidal choroidal vasculopathy in white patients.

PURPOSE: To report on a series of white patients in the United States with polypoidal choroidal vasculopathy (PCV). METHODS: This is a retrospective chart review of 27 patients at a single center with PCV. RESULTS: The mean age was 74.3 with 48% being male. The most common presenting diagnosis was exudative age-related macular degeneration in 59%, and it took 17.5 months to diagnose PCV. During this time, patients received one antivascular endothelial growth factor injection every 1.3 months. The most common reason for suspecting PCV was a large retinal pigment epithelial detachment or a poor response to antivascular endothelial growth factor therapy. Once PCV was diagnosed, most underwent photodynamic therapy. In those who received photodynamic therapy, the fluid and/or age-related macular degeneration decreased in 86%. The vision improved in 41% with 36% maintaining stable vision. Patients received only one additional injection every 3.95 months after photodynamic therapy. CONCLUSION: This is one of the larger series of PCV in an entirely white population. It emphasizes the importance of diagnosis in whites as PCV can masquerade as recalcitrant exudative age-related macular degeneration. Common findings were a temporal or peripapillary location and the presence of lipid. After photodynamic therapy, the patients still required antivascular endothelial growth factor therapy, but the injection burden was decreased by 67% and vision was found to be improved or maintained in 77% of patients.

The effect of nicotine on anti-vascular endothelial growth factor therapy in a mouse model of neovascular age-related macular degeneration.

PURPOSE: The purpose of this article is to evaluate the effect of nicotine on anti-vascular endothelial growth factor therapy in the treatment of neovascular age-related macular degeneration. METHODS: One group of mice received nicotine in drinking water and the other group received water only. Choroidal neovascularization (CNV) was induced with a laser. Nicotinic acetylcholine receptor-α7 (nAChRα7) expression was evaluated by immunohistochemistry. Bevacizumab or adiponectin peptide II (APNpII) was injected intravitreally on Day 7 postlaser, and the effects were evaluated on Days 14 and 21. α-Bungarotoxin was injected intraperitoneally on Days 2 to 5, and its effect was evaluated on Day 14. RESULTS: Expression of nAChRα7 was 2 to 7 times higher between Days 3 and 7 postlaser compared with naive mice. In water-fed mice, APNpII, bevacizumab, and α-bungarotoxin significantly reduced CNV size. In nicotine-fed mice, treatment with APNpII or bevacizumab did not significantly reduce CNV size, whereas α-bungarotoxin did have an effect. Comparing water- and nicotine-fed mice, CNV size was 61% to 86% smaller in water-fed mice except for the α-bungarotoxin group, where there was no difference. Platelet-derived growth factor and vascular endothelial growth factor expression was 1.5- to 2.5-fold higher at Day 14 in nicotine-treated mice. CONCLUSION: Nicotine significantly blocks the effect of anti-vascular endothelial growth factor therapy in the treatment of laser-induced neovascular age-related macular degeneration. nAChRα7 is significantly upregulated during the formation of CNV, and treatment with an nAChRα7 antagonist decreases CNV size irrespective of nicotine administration.

Quantitative analysis of procalcitonin after pediatric cardiothoracic surgery.

Procalcitonin appears to be an early and sensitive marker of bacterial infection in a variety of clinical settings. The use of levels of procalcitonin to predict infection in children undergoing cardiac surgery, however, may be complicated by the systemic inflammatory response that normally accompanies cardiopulmonary bypass. The aim of our study was to estimate peri-operative concentrations of procalcitonin in non-infected children undergoing cardiac surgery. Samples of serum for assay of procalcitonin were obtained in 53 patients at baseline, 24, 48, and 72 hours following cardiac surgery. Concentrations were assessed using an immunoluminetric technique. Median concentrations were lowest at baseline at less than 0.5 nanograms per millilitre, increased at 24 hours to 1.8 nanograms per millilitre, maximized at 48 hours at 2.1 nanograms per millilitre, and decreased at 72 hours to 1.3 nanograms per millilitre, but did not return to baseline levels. Ratios of concentrations between 24, 48 and 72 hours after surgery as compared to baseline were 6.15, with 95 percent confidence intervals between 4.60 and 8.23, 6.49, with 95 percent confidence intervals from 4.55 to 9.27, and 4.26, with 95 percent confidence intervals between 2.78 and 6.51, respectively, with a p value less than 0.001. In 8 patients, who had no evidence of infection, concentrations during the period from 24 to 72 hours were well above the median for the group. We conclude that concentrations of procalcitonin in the serum increase significantly in children following cardiac surgery, with a peak at 48 hours, and do not return to baseline within 72 hours of surgery. A proportion of patients, in the absence of infection, had exaggerated elevations post-operatively.