Climate change amplifies the risk of potentially toxigenic cyanobacteria.

Cyanobacterial blooms pose a significant threat to water security, with anthropogenic forcing being implicated as a key driver behind the recent upsurge and global expansion of cyanobacteria in modern times. The potential effects of land-use alterations and climate change can lead to complicated, less-predictable scenarios in cyanobacterial management, especially when forecasting cyanobacterial toxin risks. There is a growing need for further investigations into the specific stressors that stimulate cyanobacterial toxins, as well as resolving the uncertainty surrounding the historical or contemporary nature of cyanobacterial-associated risks. To address this gap, we employed a paleolimnological approach to reconstruct cyanobacterial abundance and microcystin-producing potential in temperate lakes situated along a human impact gradient. We identified breakpoints (i.e., points of abrupt change) in these time series and examined the impact of landscape and climatic properties on their occurrence. Our findings indicate that lakes subject to greater human influence exhibited an earlier onset of cyanobacterial biomass by 40 years compared to less-impacted lakes, with land-use change emerging as the dominant predictor. Moreover, microcystin-producing potential increased in both high- and low-impact lakes around the 1980s, with climate warming being the primary driver. Our findings chronicle the importance of climate change in increasing the risk of toxigenic cyanobacteria in freshwater resources.

Reconstructing historical time-series of cyanobacteria in lake sediments: Integrating technological innovation to enhance cyanobacterial management.

The global rise of cyanobacterial blooms emphasizes the need to develop tools to manage water bodies prone to cyanobacterial dominance. Reconstructing cyanobacterial baselines and identifying environmental drivers that favour cyanobacterial dominance are important to guide management decisions. Conventional techniques for estimating cyanobacteria in lake sediments require considerable resources, creating a barrier to routine reconstructions of cyanobacterial time-series. Here, we compare a relatively simple technique based on spectral inferences of cyanobacteria using visible near-infrared reflectance spectroscopy (VNIRS) with a molecular technique based on real-time PCR quantification (qPCR) of the 16S rRNA gene conserved in cyanobacteria in 30 lakes across a broad geographic gradient. We examined the sedimentary record from two perspectives: 1) relationships throughout the entire core (without radiometric dating); 2) relationships post-1900s with the aid of radiometric dating (i.e., 210Pb). Our findings suggest that the VNIRS-based cyanobacteria technique is best suited for reconstructing cyanobacterial abundance in recent decades (i.e., circa 1990 onwards). The VNIRS-based cyanobacteria technique showed agreement with those generated using qPCR, with 23 (76%) lakes showing a strong or very strong positive relationship between the results of the two techniques. However, five (17%) lakes showed negligible relationships, suggesting cyanobacteria VNIRS requires further refinement to understand where VNIRS is unsuitable. This knowledge will help scientists and lake managers select alternative cyanobacterial diagnostics where appropriate. These findings demonstrate the utility of VNIRS, in most instances, as a valuable tool for reconstructing past cyanobacterial prevalence.

Practical Guide to Measuring Wetland Carbon Pools and Fluxes.

Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions. Supplementary Information: The online version contains supplementary material available at 10.1007/s13157-023-01722-2.

Partial suturectomy for phenotypical craniosynostosis caused by incomplete fusion of cranial sutures: a novel surgical solution.

OBJECTIVE: Patients presenting with head shape changes phenotypical for craniosynostosis may have incomplete fusion of the involved sutures. The surgical literature is lacking in appropriate management strategies for these patients. In this paper, the authors evaluate their experience with a novel treatment strategy: suturectomy of only the fused portion followed by helmeting therapy in patients with skull deformity secondary to incomplete suture synostosis. METHODS: Patients with craniosynostosis with incomplete suture fusion requiring operative intervention between 2018 and 2020 were included for evaluation. Patients were selected for partial suturectomy if the patent portion of the suture had a normal appearance. All patients underwent craniectomy of the involved portion of the synostosed suture. Intraoperative ultrasound was used to reassess the degree of fusion at the time of surgery and incision planning. A 2- to 3-cm strip craniectomy was performed under direct visualization through a single minimal access incision. Postoperative helmeting was utilized for all patients. Demographic and perioperative data were collected, including laser scan data in the form of cranial index (CI) and cranial vault asymmetry (CVA), defined as the difference between two diagonal measurements, from the frontozygomaticus to the opposite eurion. RESULTS: Four males and 1 female with a mean age of 2.8 months (range 1.1-3.9 months) at presentation were included. All patients had incomplete sagittal synostosis (one patient also had an incomplete left lambdoid synostosis and another had an incomplete left coronal synostosis). The mean age at surgery was 3.5 months (range 2.0-4.7 months) without any major complications. All patients were compliant with postoperative helmeting. The average age at the last follow-up was 12.8 months (range 5.3-23.7 months) with a mean follow-up duration of 9.3 months (range 0.5-19.6 months). Final laser scan evaluations were available for 3 patients and showed an improvement of the CI from an average of 71.3 (range 70-73) to 84.3 (range 82-86). The CVA improved from an average of 9.67 mm (range 2-22 mm) to 1.67 mm (range 1-2 mm). CONCLUSIONS: Minimally invasive direct excision of the involved portion of fused cranial sutures followed by helmet therapy for phenotypical craniosynostosis is a safe and effective treatment strategy. This technique is suitable for very young patients and appears to offer similar outcomes to complete suturectomy. Further studies are required to see if this approach reduces the deformity severity for patients requiring vault remodeling later in life.

Targeted Injection of a Truncated Form of Tissue Inhibitor of Metalloproteinase 3 Alters Post-Myocardial Infarction Remodeling.

Infarct expansion can occur after myocardial infarction (MI), which leads to adverse left ventricular (LV) remodeling and failure. An imbalance between matrix metalloproteinase (MMP) induction and tissue inhibitors of MMPs (TIMPs) can accelerate this process. Past studies have shown different biologic effects of TIMP-3, which may depend upon specific domains within the TIMP-3 molecule. This study tested the hypothesis that differential effects of direct myocardial injections of either a full-length recombinant TIMP-3 (F-TIMP-3) or a truncated form encompassing the N-terminal region (N-TIMP-3) could be identified post-MI. MI was induced in pigs that were randomized for MI injections (30 mg) and received targeted injections within the MI region of F-TIMP-3 (n = 8), N-TIMP-3 (n = 9), or saline injection (MI-only, n = 11). At 14 days post-MI, LV ejection fraction fell post-MI but remained higher in both TIMP-3 groups. Tumor necrosis factor and interleukin-10 mRNA increased by over 10-fold in the MI-only and N-TIMP-3 groups but were reduced with F-TIMP-3 at this post-MI time point. Direct MI injection of either a full-length or truncated form of TIMP-3 is sufficient to favorably alter the course of post-MI remodeling. The functional and differential relevance of TIMP-3 domains has been established in vivo since the TIMP-3 constructs demonstrated different MMP/cytokine expression profiles. These translational studies identify a unique and more specific therapeutic strategy to alter the course of LV remodeling and dysfunction after MI. SIGNIFICANCE STATEMENT: Using different formulations of tissue inhibitor of matrix metalloproteinase-3 (TIMP-3), when injected into the myocardial infarction (MI) region, slowed the progression of indices of left ventricular (LV) failure, suggesting that the N terminus of TIMP-3 is sufficient to attenuate early adverse functional events post-MI. Injections of full-length recombinant TIMP-3, but not of the N-terminal region of TIMP-3, reduced relative indices of inflammation at the mRNA level, suggesting that the C-terminal region affects other biological pathways. These unique proof-of-concept studies demonstrate the feasibility of using recombinant small molecules to selectively interrupt adverse LV remodeling post-MI.

The Use of Ultrasound Guidance for the Treatment of Raynaud Disease of the Hand With Botulinum Toxin.

BACKGROUND: This study sought to examine the feasibility and effectiveness of the use of ultrasound (US) as a clinical adjunct in the delivery of botulinum toxin for the treatment of Raynaud disease of the hand. METHODS: One cadaver hand was injected with a colored simulation material using the current traditional surface anatomy approach, whereas an additional cadaver hand was injected using US guidance. The hands were dissected and areas of distribution of the simulation material were evaluated. Five patients diagnosed with Raynaud disease were treated with botulinum toxin using US guidance and data using the Patient-Reported Outcomes Measurement Information System Upper Extremity were collected. RESULTS: The cadaver hand injected with a colored simulation material using US guidance demonstrated significantly reduced surface area of muscle infiltrated compared with the cadaver hand injected using the traditional surface anatomy approach (16 cm vs 37 cm, P < 0.001).All 5 patients treated with botulinum toxin using US guidance reported significant improvement in symptoms and function after injection (P < 0.05), where zero patients reported intrinsic hand weakness. CONCLUSIONS: The use of US significantly improves the accuracy of delivery of a surrogate dye in a cadaver model of Raynaud disease, whereas its use clinically results in at least as effective a treatment as the landmark approach, but with less botulinum toxin required to achieve the clinical effect.

Use of Sentinel Lymph Node Incision for Second Stage Implant-Based Breast Reconstruction After Radiation.

BACKGROUND: Staged expander to implant breast reconstruction is associated with a high complication rate when the patient has had postmastectomy radiation. With an increasing number of American women undergoing implant-based breast reconstruction after postmastectomy radiation, surgeons may find themselves operating in a radiated field with synthetic devices. We report the performance characteristics of a novel surgical modification to the second stage expander to implant exchange after adjuvant radiation using a transaxillary approach through a prior sentinel lymph node incision, a site remote from the breast implant pocket. METHODS: We performed a retrospective review of a prospectively maintained database to evaluate the surgical outcomes of serial patients undergoing second staged expander to implant exchange through the sentinel lymph node incision 6 months or more after completing whole breast radiation. A case matched cohort to age, body mass index, and comorbid status was used to compare outcomes between patients in the group of interest versus a traditional skin sparing incision on the anterior breast mound through the radiated skin envelope. All patients included demonstrated grade 1 or 2 skin changes on the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer Late Radiation Morbidity Scoring Schema for the skin organ system. RESULTS: Nineteen breasts were reconstructed for 18 women after immediate tissue expander placement and adjuvant whole breast radiation were included in our group of interest. Forty-one case-matched second controls were identified for the comparison group. There were no intraoperative complications. Two postoperative complications were reported for the sentinel lymph node approach group (10.5%) with an average of 9 months of follow-up: 1 operative exploration for hematoma and 1 minor wound requiring recloser in the office. The case matched cohort demonstrated significantly more minor postoperative complications (P = 0.037) with a total complications rate of 41.4%. There were 31.7% of the patients that experienced a minor complication alone, whereas 9.7% of the case-matched cohort experienced a major complication. CONCLUSIONS: These data support the use of the existing axillary sentinel lymph node access incision for second stage placement of a gel implant after immediate expander and adjuvant radiation therapy. The sentinel lymph node incision approach facilitates layered closure over the breast pocket at a site remote from irradiated tissue, reducing the incidence of postoperative minor complications. Forthcoming long-term data will determine if differences in reported capsular contracture rates can be achieved with a remote transaxillary approach to second stage implant reconstruction after radiation.

Determination of sediment sources in a mixed watershed within the Appalachian-St. Lawrence Lowland Regions of southern Quebec using sediment fingerprinting.

This paper identifies the main sediment sources to the Beaudet Reservoir in Quebec (Canada) using sediment fingerprinting. The reservoir, which is built on the Bulstrode River and provides drinking water to Victoriaville, has decreased in capacity by 35% in the past 35 years. This study provides new data on fingerprinting in large and complex watersheds, a first in the province of Quebec. Nine sampling sites on the Bulstrode River and its three main tributaries were selected and five sampling campaigns were conducted. Samples from river bank profiles and adjacent fields, along with suspended sediments, were collected. All samples were sieved to 2 mm and analyzed for 137Caesium, 15 geochemical elements and sieved to 63 µm for color analysis. Source classification, based on an ANOVA test to verify the independence hypothesis and iterative linear discriminant analysis to optimize the ratio of inter-group/within-group variability, resulted in four sample classes: agricultural soils, forested soils, stream bank bottom and stream bank top. A Kruskal-Wallis H test then identified 21 out of the 32 tracers with p value < 0.05. The linear discriminant analysis led to a set of 14 tracers, namely 137Cs and 13 color coefficients with a discriminating result of 94%. That combination of 137Cs and color coefficients proved to be a cost-effective fingerprint. Based on MixSIAR modeling results, this sediment fingerprinting study has demonstrated that the main sediment sources varied within the watershed but, generally, forested soil particles dominated (33 to 49%), then agricultural soils (43 to 50%) reflecting the land use changes, followed by stream bank bottoms (82%) at the Beaudet Reservoir.

Bone Graft Substitutes: Current Concepts and Future Expectations.

Owing to its osteoinductive and osteoconductive properties and the presence of osteogenic cells, freshly harvested autologous bone graft is the gold standard for skeletal reconstruction where there is inadequate native bone. Whereas these characteristics are difficult to replicate, engineered, commercially available bone graft substitutes aim to achieve a comparable osseoregenerative profile. This work furnishes the reader with an understanding of the predominant classes of bone graft substitutes available for reconstruction of upper extremity bone defects following trauma or oncological surgery. We review bone graft substitutes with respect to their mechanisms of action, their advantages and disadvantages, and their indications and contraindications. We provide examples of bone graft substitutes in clinical use and outline comparative costs. We also describe the future directions for this specific aspect of reconstructive surgery with a focus on the role of bioactive glass.

The Use of Patient-Specific Three-Dimensional Printed Surgical Models Enhances Plastic Surgery Resident Education in Craniofacial Surgery.

PURPOSE: A significant challenge in surgical education is to provide a meaningful hands-on experience with the pathology the trainee will see in independent practice. Craniofacial anatomy is challenging and unfamiliar to the learner. METHODS: Using preoperative computed tomography data, the authors produced an accurately sized, three-dimensional (3D) printed model of the congenital craniofacial anatomy of patients treated by the same attending surgeon-PGY4 resident surgeon pair over the course of a 6-month rotation. A preoperative stepwise surgical plan was written by the attending and resident, and the plan was marked on the 3D model by the attending and resident separately. The written and marked plans were measured for accuracy and time to completion. The resident surgeon's applicable milestone levels were assessed. RESULTS: Seven congenital craniofacial anomalies met criteria for inclusion: 4 craniosynostosis cases, 2 mandibular distractions, and 1 LeFort I distraction. The number of inaccuracies of the written plan improved from 5 to 0 for sagittal synostosis and 4 to 0 for mandibular distraction. The time to complete the written plan decreased by 22% for sagittal synostosis and 45% for mandibular distraction. The number of inaccuracies of the marked plan decreased from 5 to 0 for sagittal synostosis and 2 to 0 for mandibular distraction. Time to completion of the marked plan decreased by 76% for sagittal synostosis and 50% for mandibular distraction. Milestone scores increased an average of 1.875 levels. CONCLUSION: Three-dimensional printed craniofacial models are a positive addition to resident training and have been objectively quantified to improve the accuracy and time to completion of the surgical plan as well as progression in the plastic surgery milestones.

Laparoscopic Free Omental Flap for Craniofacial Reconstruction: A Video Article Demonstrating Operative Technique and Surgical Applications.

The omental flap is a well described pedicled flap for surgical reconstruction of multiple body locations. As a laparoscopically harvested free flap, the omentum offers a minimally invasive solution to many reconstructive problems including extremity and head and neck wounds. This video article highlights the operative technique involved in flap harvest and inset for a cranial defect. An illustrative case involving a 23-year-old female's traumatic scalp degloving injury that was resurfaced by free omental flap and split-thickness skin graft is presented. This patient had stable long-term wound coverage for a very severe injury. Through video media we demonstrate that the laparoscopically harvested free omental flap is a minimally invasive, 2-team operation that provides soft tissue coverage of severe, remote wounds. This video demonstrates a safe operative technique and nuances specific to laparoscopic harvest of this flap.

Injectable and bioresponsive hydrogels for on-demand matrix metalloproteinase inhibition.

Inhibitors of matrix metalloproteinases (MMPs) have been extensively explored to treat pathologies where excessive MMP activity contributes to adverse tissue remodelling. Although MMP inhibition remains a relevant therapeutic target, MMP inhibitors have not translated to clinical application owing to the dose-limiting side effects following systemic administration of the drugs. Here, we describe the synthesis of a polysaccharide-based hydrogel that can be locally injected into tissues and releases a recombinant tissue inhibitor of MMPs (rTIMP-3) in response to MMP activity. Specifically, rTIMP-3 is sequestered in the hydrogels through electrostatic interactions and is released as crosslinks are degraded by active MMPs. Targeted delivery of the hydrogel/rTIMP-3 construct to regions of MMP overexpression following a myocardial infarction significantly reduced MMP activity and attenuated adverse left ventricular remodelling in a porcine model of myocardial infarction. Our findings demonstrate that local, on-demand MMP inhibition is achievable through the use of an injectable and bioresponsive hydrogel.

Selecting Color-based Tracers and Classifying Sediment Sources in the Assessment of Sediment Dynamics Using Sediment Source Fingerprinting.

The use of sediment color as a fingerprint property to determine sediment sources is an emerging technique that can provide a rapid and inexpensive means of investigating sediment sources. The present study aims to test the feasibility of color fingerprint properties to apportion sediment sources within the South Tobacco Creek Watershed (74 km) in Manitoba, Canada. Suspended sediment from 2009 to 2011 at six monitoring stations and potential source samples along the main stem of the creek were collected. Reflectance spectra of sediments and source materials were quantified using a diffuse reflectance spectrometry, and 16 color coefficients were derived from several color space models. Canonical discriminant analysis was used to reclassify and downsize sediment source groups. After the linear additive test and stepwise discriminant function analysis, four color coefficients were chosen to fit the Stable Isotope Analysis in R model. Consistent with the conventional fingerprinting approach, the color fingerprint results demonstrated a switch in the dominant sediment source between the headwaters and the outlet of the watershed, with the main sources being topsoil in the upper reaches, whereas outcrop shale and stream bank materials dominated in the lower reaches. The color fingerprinting approach can be integrated with conventional fingerprints (e.g., geochemical and fallout radionuclide properties) to improve source discrimination, which is a key component for source ascription modeling. We concluded that the use of color fingerprints is a promising, cost-effective technique for sediment source fingerprinting.

Nutrient and sediment losses in snowmelt runoff from perennial forage and annual cropland in the canadian prairies.

An 8-yr field-scale study, 2005 to 2012, investigated effects of agricultural land use on nutrient and sediment losses during snowmelt runoff from four treatment fields in southern Manitoba. In 2005, two fields with a long-term history of annual crop (AC) production were planted to perennial forage (PF), while two other fields were left in AC production. In 2009, the AC fields were converted to PF, while the PF fields were returned to AC. Runoff flow rates were monitored at the lower edge of the fields, and nutrient concentrations of runoff water were determined. The effects of AC and PF on selected variables were similar for the spatial (between-fields) and temporal (within-field) comparisons. The flow-weighted mean concentrations (FWMCs) and loads of particulate N, P, and sediment were not affected by treatment. Soil test N and the FWMC and load of NO (NO + NO) were significantly greater in the AC treatment, but the FWMC and load of NH were greater in the PF treatment. Loads of total dissolved N (TDN) and total N (TN) were not affected by treatment, although the concentrations of TDN and TN were greater in the AC treatment. The PF treatment significantly increased FWMCs and loads of total dissolved P (TDP) and total P (TP). On an annual snowmelt runoff basis, the PF treatment increased the FWMC of TDP by 53% and TP by 52% and increased the load of TDP by 221% and TP by 160% compared with the AC treatment. The greater P and NH losses in the PF treatment were attributed mainly to nutrient release from forage residue due to freezing.

Conversion of Conservation Tillage to Rotational Tillage to Reduce Phosphorus Losses during Snowmelt Runoff in the Canadian Prairies.

In a preceding study, converting conventional tillage (ConvT) to conservation tillage (ConsT) was reported to decrease nitrogen (N) but to increase phosphorus (P) losses during snowmelt runoff. A field-scale study was conducted from 2004 to 2012 to determine if conversion of ConsT to rotational tillage (RotaT), where conservation tillage was interrupted by a fall tillage pass every other year, could effectively reduce P losses compared with ConsT. The RotaT study was conducted on long-term paired watersheds established in 1993. The ConvT field in the pair has remained under ConvT practice since 1993, whereas tillage was minimized on the ConsT field from 1997 until 2007. In fall 2007, RotaT was introduced to the ConsT field, and heavy-duty cultivator passes were conducted in the late fall of years 2007, 2009, and 2011. Runoff volume and nutrient content were monitored at the edge of the two fields, and soil and crop residue samples were taken in each field. Greater soil Olsen P and more P released from crop residue are likely the reasons for the increased P losses in the ConsT treatment (2004-2007) relative to the ConvT treatment (2004-2007). Analysis of covariance indicated that, compared with ConsT (2004-2007), RotaT (2008-2012) increased the concentrations of dissolved organic carbon (DOC) by 62%, total dissolved N (TDN) by 190%, and total N (TN) by 272% and increased the loads of DOC by 34%, TDN by 34%, and TN by 60%. However, RotaT (2008-2012) decreased soil test P in surface soil, P released from crop residue, and duration of runoff compared with ConsT (2004-2007) and thus decreased the concentrations of total dissolved P (TDP) by 46% and total P (TP) by 38% and decreased the loads of TDP by 56% and TP by 42%. In the Canadian Prairies, where P is a major environmental concern compared with N, RotaT was demonstrated to be an effective practice to reduce P losses compared with ConsT.

Critical factors affecting field-scale losses of nitrogen and phosphorus in spring snowmelt runoff in the canadian prairies.

A long-term, field-scale study in southern Manitoba, Canada, was used to identify the critical factors controlling yearly transport of nitrogen (N) and phosphorus (P) by snowmelt runoff. Flow monitoring and water sampling for total and dissolved N and P were performed at the edge of field. The flow-weighted mean concentrations and loads of N and P for the early (the first half of yearly total volume of snowmelt runoff), late (the second half of yearly total volume of snowmelt runoff), and yearly snowmelt runoff were calculated as response variables. A data set of management practices, weather variables, and hydrologic variables was generated and used as predictor variables. Partial least squares regression analysis indicated that critical factors affecting the water chemistry of snowmelt runoff depended on the water quality variable and stage of runoff. Management practices within each year, such as nitrogen application rate, number of tillage passes, and residue burial ratio, were critical factors for flow-weighted mean concentration of N, but not for P concentration or nutrient loads. However, the most important factors controlling nutrient concentrations and loads were those related to the volume of runoff, including snow water equivalent, flow rate, and runoff duration. The critical factors identified for field-scale yearly snowmelt losses provide the basis for modeling of nutrient losses in southern Manitoba and potentially throughout areas with similar climate in the northern Great Plains region, and will aid in the design of effective practices to reduce agricultural nonpoint nutrient pollution in downstream waters.

Influence of climate, topography, and soil type on soil extractable phosphorus in croplands of northern glacial-derived landscapes.

Delineating the relative solubility of soil phosphorus (P) in agricultural landscapes is essential to predicting potential P mobilization in the landscape and can improve nutrient management strategies. This study describes spatial patterns of soil extractable P (easily, moderately, and poorly soluble P) in agricultural landscapes of the Red River basin and the southern Great Lakes region. Surface soils (0-30 cm) and select deeper cores (0-90 cm) were collected from 10 cropped fields ranging in terrain (near-level to hummocky), soil texture (clay to loam), composition (calcareous to noncalcareous), and climate across these differing glacial landscapes. Poorly soluble P dominated (up to 91%) total extractable P in the surface soils at eight sites. No differences in the relative solubilities of soil extractable P with microtopography were apparent in landscapes without defined surface depressions. In contrast, in landscapes with pronounced surface depressions, increased easily soluble P (Sol-P), and decreased soil P sorption capacity were found in soil in wetter, low-slope zones relative to drier upslope locations. The Sol-P pool was most important to soil P retention (up to 28%) within the surface depressions of the Red River basin and at sites with low-carbonate soils in the southern Lake Erie watershed (up to 28%), representing areas at elevated risk of soil P remobilization. This study demonstrates interrelationships among soil extractable P pools, soil development, and soil moisture regimes in agricultural glacial landscapes and provides insight into identifying potential areas for soil P remobilization and associated P availability to crops and runoff.

Regional heterogeneity in determinants of atrial matrix remodeling and association with atrial fibrillation vulnerability postmyocardial infarction.

BACKGROUND: Left ventricular (LV) remodeling following a myocardial infarction (MI) is associated with new-onset atrial fibrillation (AF). LV remodeling post-MI is characterized by regional changes in matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), causing extracellular matrix (ECM) remodeling. OBJECTIVE: The purpose of this study was to test the hypothesis that a shift in regional atrial MMP activity, MMP/TIMP expression, and ECM remodeling occurs post-MI, which cause increased vulnerability to AF. METHODS: MI was induced in pigs (weight 25 kg; coronary ligation; n = 9). At approximately 14 days post-MI, an atrial electrical stimulation protocol was performed, after which an MMP radiotracer was infused, MMP/TIMP mRNA profiling performed, and ECM collagen assessed by histochemistry. An additional 7 non-MI pigs served as controls. RESULTS: AF could be induced in 89% (8/9) of the post-MI pigs but none of the controls. MMP activity (MMP radiotracer uptake) increased by approximately 2-fold in most atrial regions post-MI, whereas fibrillar collagen content was unchanged or actually reduced in right atrial regions and increased in left atrial regions. MMP/TIMP profiles revealed a heterogeneous pattern from the left atrial appendage to right atrial regions. CONCLUSION: AF vulnerability early post-MI was associated with a heterogeneous pattern of atrial ECM remodeling, detectable by noninvasive molecular imaging. Detection of early atrial MMP activation post-MI may help define the myocardial substrate underlying AF.

The effects of multiple beneficial management practices on hydrology and nutrient losses in a small watershed in the Canadian prairies.

Most beneficial management practices (BMPs) recommended for reducing nutrient losses from agricultural land have been established and tested in temperate and humid regions. Previous studies on the effects of these BMPs in cold-climate regions, especially at the small watershed scale, are rare. In this study, runoff and water quality were monitored from 1999 to 2008 at the outlets of two subwatersheds in the South Tobacco Creek watershed in Manitoba, Canada. Five BMPs-a holding pond below a beef cattle overwintering feedlot, riparian zone and grassed waterway management, grazing restriction, perennial forage conversion, and nutrient management-were implemented in one of these two subwatersheds beginning in 2005. We determined that >80% of the N and P in runoff at the outlets of the two subwatersheds were lost in dissolved forms, ≈ 50% during snowmelt events and ≈ 33% during rainfall events. When all snowmelt- and rainfall-induced runoff events were considered, the five BMPs collectively decreased total N (TN) and total P (TP) exports in runoff at the treatment subwatershed outlet by 41 and 38%, respectively. The corresponding reductions in flow-weighted mean concentrations (FWMCs) were 43% for TN and 32% for TP. In most cases, similar reductions in exports and FWMCs were measured for both dissolved and particulate forms of N and P, and during both rainfall and snowmelt-induced runoff events. Indirect assessment suggests that retention of nutrients in the holding pond could account for as much as 63 and 57%, respectively, of the BMP-induced reductions in TN and TP exports at the treatment subwatershed outlet. The nutrient management BMP was estimated to have reduced N and P inputs on land by 36 and 59%, respectively, in part due to the lower rates of nutrient application to fields converted from annual crop to perennial forage. Overall, even though the proportional contributions of individual BMPs were not directly measured in this study, the collective reduction of nutrient losses from the five BMPs was substantial.

Phosphorus runoff from Canadian agricultural land: A dataset for 30 experimental fields.

Phosphorus (P) runoff from agricultural land plays a critical role in downstream water quality. This article summarizes P and sediment runoff data for both snowmelt and rainfall runoff from 30 arable fields in the Canadian provinces of Saskatchewan, Manitoba and Ontario. The data were collected from 216 site-years of field experiments, with climates ranging from semi-arid to humid and a wide range of field management practices. In the article, mean annual and seasonal (in terms of snowmelt and rain) precipitation inputs, runoff depths, and P and sediment concentrations and loads are presented, along with ranges of yearly values. In addition, information of field management and soil characteristics (e.g. soil type and soil Olsen P) is also presented for each field. The data have potential to be reused for national and international cross-region comparisons of P and sediment losses, constructing and validating decision-support models and tools for assessing and managing P losses in both snowmelt and rainfall runoff, and informing beneficial management practices to improve agricultural water quality. Interpretation of the data is found in "Phosphorus runoff from Canadian agricultural land: A cross-region synthesis of edge-of-field results" [1].