Association of Redlining and Natural Environment with Depressive Symptoms in Women in the Sister Study

BACKGROUND

Improving mental health is recognized as an important factor for achieving global development goals. Despite strong evidence that neighborhood greenery promotes better mental health, there are environmental justice concerns over the distribution of neighborhood greenery. Underlying these concerns are present-day consequences of historical discriminatory financial investment practices, such as redlining which was established by the U.S. Federal Home Owners' Loan Corporation (HOLC) in the 1930s. The impacts of redlining on environmental and health disparities have been researched extensively. However, the influences of redlining on the associations between neighborhood environment and health outcomes have not been fully assessed.

OBJECTIVES

The aim of this study was to examine whether associations between residential tree cover and depressive symptoms vary across areas subject to HOLC practices.

METHODS

Depressive symptoms were defined by the 10-item Center for Epidemiologic Studies Depression Scale collected during the period 2008-2012 for 3,555 women in the Sister Study cohort residing in cities subject to HOLC practices across the United States. HOLC rating maps were obtained from the Mapping Inequality Project, University of Richmond, with neighborhoods graded as A (best for financial investment, green), B (still desirable, blue), C (declining, yellow), and D (hazardous, red-known as redlined). Tree cover within 500 m and 2,000 m from residences was estimated using 2011 U.S. Forest Service Percent Tree Canopy Cover. Mixed model using climate zone as the random effect was applied to evaluate the associations with adjustments for potential covariates. Analyses were stratified by HOLC grade.

RESULTS

Tree cover was significantly higher in neighborhoods with better HOLC grades. A 10% increase in tree cover was associated with reduced odds of depressive symptoms for the full study population, with adjusted odds ratios (AORs) of 0.93 [95% confidence interval (CI): 0.88, 0.99], and 0.91 (0.85, 0.97) for 500 -m and 2,000 -m buffer, respectively. Across HOLC grades, the strongest associations were observed in redlined neighborhoods, with respective AORs of 0.72 (95% CI: 0.52, 0.99) and 0.63 (95% CI: 0.45, 0.90) for 500 -m and 2,000 -m buffer.

DISCUSSION

Findings support a remediation strategy focused on neighborhood greenery that would address multiple public health priorities, including mental health and environmental justice. https://doi.org/10.1289/EHP12212.

Designing amendments to improve plant performance for mine tailings revegetation

To provide recommendations for establishment of plants on low-pH Formosa Mine tailings, two greenhouse experiments were conducted to evaluate the use of remedial amendments to improve the survival and growth of Douglas fir (Pseudotsuga menziesii) seedlings. A preliminary experiment indicated that 1% lime (by weight) raised tailings pH, permitting seedling survival. However, high rates of biosolid application (BS; 2% by weight) added to supply nutrients were phytotoxic when added with lime. A gasified conifer biochar (BC) added to tailings at 1%, 2.5%, or 5% (by weight), along with lime and BS, caused an additional increase in pH, decreased electrical conductivity (EC), and tended to increase the survival of Douglas fir. The addition of a locally sourced microbial inoculum (LSM) did not affect survival. A subsequent experiment expanded our experimental design by testing multiple levels of amendments that included lime (0.5% and 1% by weight), three application rates (0.2%, 0.5%, and 2%) of two nutrient sources (BS or mineral fertilizer), BC (0% and 2.5%), and with or without LSM. There were many interactions among amendments. In general, Douglas fir survival was enhanced when lime and BC were added. These experiments suggest that amending with lime, a nutrient source, and BC would enhance revegetation on low-pH, metal-contaminated mine tailings.

Vinyl chloride enhances high-fat diet-induced proteome alterations in the mouse pancreas related to metabolic dysfunction

Alterations in physiological processes in pancreas have been associated with various metabolic dysfunctions and can result from environmental exposures, such as chemicals and diet. It was reported that environmental vinyl chloride (VC) exposure, a common industrial organochlorine and environmental pollutant, significantly exacerbated metabolic-related phenotypes in mice fed concurrently with high-fat diet (HFD) but not low-fat diet (LFD). However, little is known about the role of the pancreas in this interplay, especially at a proteomic level. The present study was undertaken to examine the protein responses to VC exposure in pancreas tissues of C57BL/6J mice fed LFD or HFD, with focus on the investigation of protein expression and/or phosphorylation levels of key protein biomarkers of carbohydrate, lipid, and energy metabolism, oxidative stress and detoxification, insulin secretion and regulation, cell growth, development, and communication, immunological responses and inflammation, and biomarkers of pancreatic diseases and cancers. We found that the protein alterations may indicate diet-mediated susceptibility in mouse pancreas induced by HFD to concurrent exposure of low levels of inhaled VC. These proteome biomarkers may lead to a better understanding of pancreas-mediated adaptive or adverse response and susceptibility to metabolic disease.

Transformation and release of micronized Cu used as a wood preservative in treated wood in wetland soil

Micronized Cu (μ-Cu) is used as a wood preservative, replacing toxic chromated copper arsenate (CCA). Micronized Cu is malachite [Cu₂CO₃(OH)₂] that has been milled to micron/submicron particles, with many particle diameters less than 100 nm, mixed with biocides and then used to treat wood. In addition to concerns about the fate of the Cu from μ-Cu, there is interest in the fate of the nano-Cu (n-Cu) constituents. We examined movement of Cu from μ-Cu-treated wood after placing treated-wood stakes into model wetland ecosystems. Release of Cu into surface and subsurface water was monitored. Surface water Cu reached maximum levels 3 days after stake installation and remained elevated if the systems remained inundated. Subsurface water Cu levels were 10% of surface water levels at day 3 and increased gradually thereafter. Sequential filtering indicated that a large portion of the Cu in solution was associating with soluble organics, but there was no evidence for n-Cu in solution. After 4 months, Cu in thin-sections of treated wood and adjacent soil were characterized with micro X-ray absorption fine structure spectroscopy (μ-XAFS). Localization and speciation of Cu in the wood and adjacent soil using μ-XAFS clearly indicated that Cu concentrations decreased over time in the treated wood and increased in the adjacent soil. However, n-Cu from the treated wood was not found in the adjacent soil or plant roots. The results of this study indicate that Cu in the μ-Cu-treated wood dissolves and migrates into adjacent soil and waters primarily in ionic form (i.e., Cu²⁺) and not as nano-sized Cu particles. A reduced form of Cu (Cu₂S) was identified in deep soil proximal to the treated wood, indicating strong reducing conditions. The formation of the insoluble Cu₂S effectively removes some portion of dissolved Cu from solution, reducing movement of Cu²⁺ to the water column and diminishing exposure.

Types and spatial contexts of neighborhood greenery matter in associations with weight status in women across 28 U.S. communities

Excess body weight is a risk factor for many chronic diseases. Studies have identified neighborhood greenery as supportive of healthy weight. However, few have considered plausible effect pathways for ecosystem services (e.g., heat mitigation, landscape aesthetics, and venues for physical activities) or potential variations by climate. This study examined associations between weight status and neighborhood greenery that capture ecosystem services most relevant to weight status across 28 U.S. communities. Weight status was defined by body mass index (BMI) reported for 6591 women from the U.S. Sister Study cohort. Measures of greenery within street and circular areas at 500 m and 2000 m buffer distances from homes were derived for each participant using 1 m land cover data. Street area was defined as a 25 m-wide zone on both sides of street centerlines multiplied by the buffer distances, and circular area was the area of the circle centered on a home within each of the buffer distances. Measures of street greenery characterized the pedestrian environment to capture physically and visually accessible greenery for shade and aesthetics. Circular greenery was generated for comparison. Greenery types of tree and herbaceous cover were quantified separately, and a combined measure of tree and herbaceous cover (i.e., aggregate greenery) was also included. Mixed models accounting for the clustering at the community level were applied to evaluate the associations between neighborhood greenery and the odds of being overweight or obese (BMI > 25) with adjustment for covariates selected using gradient boosted regression trees. Analyses were stratified by climate zone (arid, continental, and temperate). Tree cover was consistently associated with decreased odds of being overweight or obese. For example, the adjusted odds ratio [AOR] was 0.92, 95% Confidence Interval [CI]: 0.88-0.96, given a 10% increase in street tree cover at the 2000 m buffer across the 28 U.S. communities. These associations held across climate zones, with the lowest AOR in the arid climate (AOR: 0.74, 95% CI: 0.54-1.01). In contrast, associations with herbaceous cover varied by climate zone. For the arid climate, a 10% increase in street herbaceous cover at the 2000 m buffer was associated with lower odds of being overweight or obese (AOR: 0.75, 95% CI: 0.55-1.03), whereas the association was reversed for the temperate climate, the odds increased (AOR: 1.19, 95% CI: 1.05-1.35). Associations between greenery and overweight/obesity varied by type and spatial context of greenery, and climate. Our findings add to a growing body of evidence that greenery design in urban planning can support public health. These findings also justify further defining the mechanism that underlies the observed associations.

How do natural features in the residential environment influence women's self-reported general health? Results from cross-sectional analyses of a U.S. national cohort

BACKGROUND

The relationship between health and human interaction with nature is complex. Here we conduct analyses to provide insights into potential health benefits related to residential proximity to nature.

OBJECTIVES

We aimed to examine associations between measures of residential nature and self-reported general health (SRGH), and to explore mediation roles of behavioral, social, and air quality factors, and variations in these relationships by urbanicity and regional climate.

METHODS

Using residential addresses for 41,127 women from the Sister Study, a U.S.-based national cohort, we derived two nature exposure metrics, canopy and non-gray cover, using Percent Tree Canopy and Percent Developed Imperviousness from the National Land Cover Database. Residential circular buffers of 250 m and 1250 m were considered. Gradient boosted regression trees were used to model the effects of nature exposure on the odds of reporting better SRGH (Excellent/Very Good versus the referent, Good/Fair/Poor). Analyses stratified by urbanicity and regional climate (arid, continental, temperate) and mediation by physical activity, social support, and air quality were conducted.

RESULTS

A 10% increase in canopy and non-gray cover within 1250 m buffer was associated with 1.02 (95% CI: 1.00-1.03) and 1.03 (95% CI: 1.01-1.04) times the odds of reporting better SRGH, respectively. Stronger associations were observed for the urban group and for continental climate relative to other strata. Social support and physical activity played a more significant mediation role than air quality for the full study population.

DISCUSSION

Findings from this study identified a small but important beneficial association between residential nature and general health. These findings could inform community planning and investments in neighborhood nature for targeted health improvements and potential societal and environmental co-benefits.

Changes in Landscape Greenness and Climatic Factors over 25 Years (1989-2013) in the USA

Monitoring and quantifying changes in vegetation cover over large areas using remote sensing can be achieved using the Normalized Difference Vegetation Index (NDVI), an indicator of greenness. However, distinguishing gradual shifts in NDVI (e.g., climate related-changes) versus direct and rapid changes (e.g., fire, land development) is challenging as changes can be confounded by time-dependent patterns, and variation associated with climatic factors. In the present study, we leveraged a method that we previously developed for a pilot study to address these confounding factors by evaluating NDVI change using autoregression techniques that compare results from univariate (NDVI vs. time) and multivariate analyses (NDVI vs. time and climatic factors) for 7,660,636 1 km × 1 km pixels comprising the 48 contiguous states of the USA, over a 25-year period (1989-2013). NDVI changed significantly for 48% of the nation over the 25-year period in the univariate analyses where most significant trends (85%) indicated an increase in greenness over time. By including climatic factors in the multivariate analyses of NDVI over time, the detection of significant NDVI trends increased to 53% (an increase of 5%). Comparisons of univariate and multivariate analyses for each pixel showed that less than 4% of the pixels had a significant NDVI trend attributable to gradual climatic changes while the remainder of pixels with a significant NDVI trend indicated that changes were due to direct factors. While most NDVI changes were attributable to direct factors like wildfires, drought or flooding of agriculture, and tree mortality associated with insect infestation, these conditions may be indirectly influenced by changes in climatic factors.

Effects of circuit resistance training and timely protein supplementation on exercise-induced fat oxidation in tetraplegic adults

BACKGROUND

Substrate utilization during exercise in persons with spinal cord injury (SCI) remains poorly defined.

PURPOSE

To investigate effects of circuit resistance training (CRT) and timing of protein supplementation (PS) on fuel utilization in persons with tetraplegia.

METHODS

Eleven individuals with chronic tetraplegia underwent 6 months of CRT 3 times weekly. Five randomly assigned participants received immediate PS (iPS) administered in split doses prior to and following all exercise sessions. Other participants consumed a matched dose of PS that was delayed until 24 hours post-exercise (dPS). Participants underwent a maximal graded exercise test (GXT) to volitional exhaustion at 4 conditioning time points: 3 months before (-3mo), at the beginning of (0mo), 3 months into (3mo), and 6 months following (6mo) the CRT conditioning program. Respiratory measures were continuously obtained throughout the GXT via open-circuit spirometry. Fuel utilization and energy expenditure were computed from the respiratory data.

RESULTS

The differences in changes in substrate utilization between the PS groups were not significant as determined by the interaction of PS group and conditioning time point, F (3, 27) = 2.32, P = .098, η(2) P = .205. Maximal absolute fat oxidation did not change significantly from 0 to 6mo (mean difference, 0.014 ± 0.031 g/min; P = .170), and fat oxidation remained low never exceeding an average of 0.10 ± 0.09 g/min for any given exercise intensity.

CONCLUSION

Maximum fat utilization during exercise and fat utilization at matched exercise intensities were not increased in persons with tetraplegia, independent of PS, and levels of fat oxidation remained low after training.

Sediment and total phosphorous contributors in Rock River watershed

Total phosphorous (TP) and total suspended sediment (TSS) pollution is a problem in the US Midwest and is of particular concern in the Great Lakes region where many water bodies are already eutrophic. Increases in monoculture corn planting to feed ethanol based biofuel production could exacerbate these already stressed water bodies. In this study we expand on the previous studies relating landscape variables such as land cover, soil type and slope with changes in pollutant concentrations and loading in the Great Lakes region. The Rock River watershed in Wisconsin, USA was chosen due to its diverse land use, numerous lakes and reservoirs susceptible to TSS and TP pollution, and the availability of long-term streamflow, TSS and TP data. Eight independent subwatersheds in the Rock River watershed were identified using United States Geological Survey (USGS) monitoring sites that monitor flow, TSS and TP. For each subwatershed, we calculated land use, soil type, and terrain slope metrics or variables. TSS and TP from the different subwatersheds were compared using Analysis of Variance (ANOVA), and associations and relationships between landscape metrics and water quality (TSS and TP) were evaluated using the partial least square (PLS) regression. Results show that urban land use and agricultural land growing corn rotated with non-leguminous crops are associated with TSS and TP in streams. This indicates that increasing the amount of corn rotated with non-leguminous crops within a subwatershed could increase degradation of water quality. Results showed that increase in corn-soybean rotation acreage within the watershed is associated with reduction in stream's TSS and TP. Results also show that forest and water bodies were associated with reduction in TSS and TP. Based on our results we recommend adoption of the Low Impact Development (LID) approach in urban dominated subwatersheds. This approach attempts to replicate the pre-development hydrological regime by reducing the ratio of impervious area to natural cover wherever possible, as well as recycling or treating stormwater runoff using filter strips, ponds and wetlands. In agriculturally dominated subwatersheds, we recommend increasing corn-soybean rotation, keeping corn on areas with gentle slope and soils with lower erodibility.

Identifying riparian buffer effects on stream nitrogen in southeastern coastal plain watersheds

Within the Southeastern (SE) Coastal Plain of the U.S., numerous freshwaters and estuaries experience eutrophication with significant nutrient contributions by agricultural non-point sources (NPS). Riparian buffers are often used to reduce agricultural NPS yet the effect of buffers in the watershed is difficult to quantify. Using corrected Akaike information criterion (AICc) and model averaging, we compared flow-path riparian buffer models with land use/land cover (LULC) models in 24 watersheds from the SE Coastal Plain to determine the ability of riparian buffers to reduce or mitigate stream total nitrogen concentrations (TNC). Additional models considered the relative importance of headwaters and artificial agricultural drainage in the Coastal Plain. A buffer model which included cropland and non-buffered cropland best explained stream TNC (R (2) = 0.75) and was five times more likely to be the correct model than the LULC model. The model average predicted that current buffers removed 52 % of nitrogen from the edge-of-field and 45 % of potential nitrogen from the average SE Coastal Plain watershed. On average, 26 % of stream nitrogen leaked through buffered cropland. Our study suggests that stream TNC could potentially be reduced by 34 % if buffers were adequately restored on all cropland. Such estimates provide realistic expectations of nitrogen removal via buffers to watershed managers as they attempt to meet water quality goals. In addition, model comparisons of AICc values indicated that non-headwater buffers may contribute little to stream TNC. Model comparisons also indicated that artificial drainage should be considered when accessing buffers and stream nitrogen.

Temporal and spatial variation of atmospherically deposited organic contaminants at high elevation in Yosemite National Park, California, USA

Contaminants used at low elevation, such as pesticides on crops, can be transported tens of kilometers and deposited in adjacent mountains in many parts of the world. Atmospherically deposited organic contaminants in the Sierra Nevada Mountains of California, USA, have exceeded some thresholds of concern, but the spatial and temporal distributions of contaminants in the mountains are not well known. The authors sampled shallow-water sediment and tadpoles (Pseudacris sierra) for pesticides, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls in four high-elevation sites in Yosemite National Park in the central Sierra Nevada twice during the summers of 2006, 2007, and 2008. Both historic- and current-use pesticides showed a striking pattern of lower concentrations in both sediment and tadpoles in Yosemite than was observed previously in Sequoia-Kings Canyon National Parks in the southern Sierra Nevada. By contrast, PAH concentrations in sediment were generally greater in Yosemite than in Sequoia-Kings Canyon. The authors suggest that pesticide concentrations tend to be greater in Sequoia-Kings Canyon because of a longer air flow path over agricultural lands for this park along with greater pesticide use near this park. Concentrations for DDT-related compounds in some sediment samples exceeded guidelines or critical thresholds in both parks. A general pattern of difference between Yosemite and Sequoia-Kings Canyon was not evident for total tadpole cholinesterase activity, an indicator of harmful exposure to organophosphorus and carbamate pesticides. Variability of chemical concentrations among sites, between sampling periods within each year, and among years, contributed significantly to total variation, although the relative contributions differed between sediment and tadpoles.

Mercury in tadpoles collected from remote alpine sites in the southern Sierra Nevada mountains, California, USA

Amphibians in alpine wetlands of the Sierra Nevada mountains comprise key components of an aquatic-terrestrial food chain, and mercury contamination is a concern because concentrations in fish from this region exceed thresholds of risk to piscivorous wildlife. Total mercury concentrations were measured in whole tadpoles of the Sierra chorus frog, Pseudacris sierra, two times at 27 sites from high elevations (2786-3375 m) in the southern Sierra Nevada. Median mercury concentrations were 14 ng/g wet weight (154 ng/g dry weight), which were generally low in comparison to tadpoles of 15 other species/location combinations from studies that represented both highly contaminated and minimally contaminated sites. Mercury concentrations in P. sierra were below concentrations known to be harmful in premetamorphic tadpoles of another species and below threshold concentrations for risk to predaceous wildlife. Concentrations in tadpoles were also lower than those observed in predaceous fish in the study region presumably because tadpoles in the present study were much younger (1-2 months) than fish in the other study (3-10 years), and tadpoles represent a lower trophic level than these fish. Mercury concentrations were not related to distance from the adjacent San Joaquin Valley, a source of agricultural and industrial pollutants.

Pesticide distributions and population declines of California, USA, alpine frogs, Rana muscosa and Rana sierrae

Atmospherically deposited pesticides from the intensively cultivated Central Valley of California, USA, have been implicated as a cause for population declines of several amphibian species, with the strongest evidence for the frogs Rana muscosa and Rana sierrae at high elevation in the Sierra Nevada mountains. Previous studies on these species have relied on correlations between frog population status and either a metric for amount of upwind pesticide use or limited measurements of pesticide concentrations in the field. The present study tested the hypothesis that pesticide concentrations are negatively correlated with frog population status (i.e., fraction of suitable water bodies occupied within 2 km of a site) by measuring pesticide concentrations in multiple media twice at 28 sites at high elevation in the southern Sierra Nevada. Media represented were air, sediment, and Pseudacris sierra tadpoles. Total cholinesterase (ChE), which has been used as an indicator for organophosphorus and carbamate pesticide exposure, was also measured in P. sierra tadpoles. Results do not support the pesticide-site occupancy hypothesis. Among 46 pesticide compounds analyzed, nine were detected with ≥ 30% frequency, representing both historically and currently used pesticides. In stepwise regressions with a chemical metric and linear distance from the Central Valley as predictor variables, no negative association was found between frog population status and the concentration of any pesticide or tadpole ChE activity level. By contrast, frog population status showed a strong positive relationship with linear distance from the Valley, a pattern that is consistent with a general west-to-east spread across central California of the amphibian disease chytridiomycosis observed by other researchers.

Temporal patterns and sources of atmospherically deposited pesticides in Alpine Lakes of the Sierra Nevada, California, U.S.A

Agricultural pesticides are being transported by air large distances to remote mountain areas and have been implicated as a cause for recent population declines of several amphibian species in such locations. Largely unmeasured, however, are the magnitude and temporal variation of pesticide concentrations in these areas, and the relationship between pesticide use and pesticide appearance in the montane environment. We addressed these topics in the southern Sierra Nevada mountains, California, by sampling water weekly or monthly from four alpine lakes from mid-June to mid-October 2003. The lakes were 46-83 km from the nearest pesticide sources in the intensively cultivated San Joaquin Valley. Four of 41 target pesticide analytes were evaluated for temporal patterns: endosulfan, propargite, dacthal, and simazine. Concentrations were very low, approximately 1 ng/L or less, at all times. The temporal patterns in concentrations differed among the four pesticides, whereas the temporal pattern for each pesticide was similar among the four lakes. For the two pesticides applied abundantly in the San Joaquin Valley during the sampling period, endosulfan and propargite, temporal variation in concentrations corresponded strikingly with application rates in the Valley with lag times of 1-2 weeks. A finer-scale analysis suggests that a large fraction of these two pesticides reaching the lakes originated in localized upwind areas within the Valley.

Spatial patterns of atmospherically deposited organic contaminants at high elevation in the southern Sierra Nevada mountains, California, USA

Atmospherically deposited contaminants in the Sierra Nevada mountains of California, USA have been implicated as adversely affecting amphibians and fish, yet little is known about the distributions of contaminants within the mountains, particularly at high elevation. The hypothesis that contaminant concentrations in a high-elevation portion of the Sierra Nevada decrease with distance from the adjacent San Joaquin Valley was tested. Air, sediment, and tadpoles were sampled twice at 28 water bodies in 14 dispersed areas in Sequoia and Kings Canyon National Parks (2,785-3,375 m elevation; 43-82 km from Valley edge). Up to 15 chemicals were detected frequently in sediment and tadpoles, including current- and historic-use pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons. Only beta-endosulfan was found frequently in air. Concentrations of all chemicals detected were very low, averaging in the parts-per-billion range or less in sediment and tadpoles, and on the order of 10 pg/m3 for beta-endosulfan in air. Principal components analysis indicated that chemical compositions were generally similar among sites, suggesting that chemical transport patterns were likewise similar among sites. In contrast, transport processes did not appear to strongly influence concentration differences among sites, because variation in concentrations among nearby sites was high relative to sites far from each other. Moreover, a general relationship for concentrations as a function of distance from the valley was not evident across chemical, medium, and time. Nevertheless, concentrations for some chemical/medium/time combinations showed significant negative relationships with metrics for distance from the Valley. However, the magnitude of these distance effects among high-elevation sites was small relative to differences found in other studies between the valley edge and the nearest high-elevation sites.

Multi-scale landscape factors influencing stream water quality in the state of Oregon

Enterococci bacteria are used to indicate the presence of human and/or animal fecal materials in surface water. In addition to human influences on the quality of surface water, a cattle grazing is a widespread and persistent ecological stressor in the Western United States. Cattle may affect surface water quality directly by depositing nutrients and bacteria, and indirectly by damaging stream banks or removing vegetation cover, which may lead to increased sediment loads. This study used the State of Oregon surface water data to determine the likelihood of animal pathogen presence using enterococci and analyzed the spatial distribution and relationship of biotic (enterococci) and abiotic (nitrogen and phosphorous) surface water constituents to landscape metrics and others (e.g. human use, percent riparian cover, natural covers, grazing, etc.). We used a grazing potential index (GPI) based on proximity to water, land ownership and forage availability. Mean and variability of GPI, forage availability, stream density and length, and landscape metrics were related to enterococci and many forms of nitrogen and phosphorous in standard and logistic regression models. The GPI did not have a significant role in the models, but forage related variables had significant contribution. Urban land use within stream reach was the main driving factor when exceeding the threshold (> or =35 cfu/100 ml), agriculture was the driving force in elevating enterococci in sites where enterococci concentration was <35 cfu/100 ml. Landscape metrics related to amount of agriculture, wetlands and urban all contributed to increasing nutrients in surface water but at different scales. The probability of having sites with concentrations of enterococci above the threshold was much lower in areas of natural land cover and much higher in areas with higher urban land use within 60 m of stream. A 1% increase in natural land cover was associated with a 12% decrease in the predicted odds of having a site exceeding the threshold. Opposite to natural land cover, a one unit change in each of manmade barren and urban land use led to an increase of the likelihood of exceeding the threshold by 73%, and 11%, respectively. Change in urban land use had a higher influence on the likelihood of a site exceeding the threshold than that of natural land cover.

Watershed vulnerability predictions for the Ozarks using landscape models

Forty-six broad-scale landscape metrics derived from commonly used landscape metrics were used to develop potential indicators of total phosphorus (TP) concentration, total ammonia (TA) concentration, and Escherichia coli bacteria count among 244 sub-watersheds of the Upper White River (Ozark Mountains, USA). Indicator models were developed by correlating field-based water quality measurements and contemporaneous remote-sensing-based ecological metrics using partial least squares (PLS) analyses. The TP PLS model resulted in one significant factor explaining 91% of the variability in surface water TP concentrations. Among the 18 contributing landscape model variables for the TP PLS model, the proportions of a sub-watershed that are barren and in human use were key indicators of water chemistry in the associated sub-watersheds. The increased presence and reduced fragmentation of forested areas are negatively correlated with TP concentrations in associated sub-watersheds, particularly within close proximity to rivers and streams. The TA PLS model resulted in one significant factor explaining 93% of the variability in surface water TA concentrations. The eight contributing landscape model variables for the TA PLS model were among the same forest and urban metrics for the TP model, with a similar spatial gradient trend in relationship to distance from streams and rivers within a sub-watershed. The E. coli PLS model resulted in two significant factors explaining 99.7% of the variability in E. coli cell count. The 17 contributing landscape model variables for the E. coli PLS model were similar to the TP and TA models. The integration of model results demonstrates that forest, riparian, and urban attributes of sub-watersheds affect all three models. The results provide watershed managers in the Ozark Mountains with a broad-scale vulnerability prediction tool, focusing on TP, TA, and E. coli, and are being used to prioritize and evaluate monitoring and restoration efforts in the vicinity of the White River, a major tributary to the Mississippi River and Gulf of Mexico.

A randomized blinded comparison of two methods used for venous antistasis in tetraplegia

OBJECTIVE

The hemodynamic effects of slow sequential compression (SCD) were compared with rapid intermittent pulsatile compression (IPC) in subjects with complete tetraplegia.

METHODS

Twenty subjects underwent Doppler examination of the bilateral popliteal and femoral veins. Resting volume flow per minute (VFM), average venous velocity (AVV), and maximal venous velocity (MVV) were measured in both veins. SCD and IPC were then randomly applied to one limb each, followed by repeat Doppler measurements under compression conditions. Doppler spectral recordings were stored for future analysis, and then measured by an investigator blinded to testing conditions (rest versus compression) and device (SCD versus IPC).

RESULTS

Sequential compression and IPC compression both increased popliteal and femoral vein VFM, AVV, and MVV above resting levels (all p's < 0.001). In the femoral vein VFM (p < 0.05) and MVV (p < 0.05) were augmented during IPC compared to SCD compression.

CONCLUSION

As MVV best reflects performance effectiveness of compression devices, these data find IPC more effective than SCD for stimulating venous blood flow in subjects with tetraplegia.

Biological integrity in mid-atlantic coastal plains headwater streams

The objective of this study was to assess the applicability of using landscape variables in conjunction with water quality and benthic data to efficiently estimate stream condition of select headwater streams in the Mid-Atlantic Coastal Plains. Eighty-two streams with riffle sites were selected from eight-two independent watersheds across the region for sampling and analyses. Clustering of the watersheds by landscape resulted in three distinct groups (forest, crop, and urban) which coincided with watersheds dominant land cover or use. We used non-parametric analyses to test differences in benthos and water chemistry between groups, and used regression analyses to evaluate responses of benthic communities to water chemistry within each of the landscape groups. We found that typical water chemistry measures associated with urban runoff such as specific conductance and dissolved chloride were significantly higher in the urban group. In the crop group, we found variables commonly associated with farming such as nutrients and pesticides significantly greater than in the other two groups. Regression analyses demonstrated that the numbers of tolerant and facultative macroinvertebrates increased significantly in forested watersheds with small shifts in pollutants, while in human use dominated watersheds the intolerant macroinvertebrates were more sensitive to shifts in chemicals present at lower concentrations. The results from this study suggest that landscape based clustering can be used to link upstream landscape characteristics, water chemistry and biotic integrity in order to assess stream condition and likely cause of degradation without the use of reference sites. Notice: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Linking land cover and water quality in New York City's water supply watersheds

The Catskill/Delaware reservoirs supply 90% of New York City's drinking water. The City has implemented a series of watershed protection measures, including land acquisition, aimed at preserving water quality in the Catskill/Delaware watersheds. The objective of this study was to examine how relationships between landscape and surface water measurements change between years. Thirty-two drainage areas delineated from surface water sample points (total nitrogen, total phosphorus, and fecal coliform bacteria concentrations) were used in step-wise regression analyses to test landscape and surface-water quality relationships. Two measurements of land use, percent agriculture and percent urban development, were positively related to water quality and consistently present in all regression models. Together these two land uses explained 25 to 75% of the regression model variation. However, the contribution of agriculture to water quality condition showed a decreasing trend with time as overall agricultural land cover decreased. Results from this study demonstrate that relationships between land cover and surface water concentrations of total nitrogen, total phosphorus, and fecal coliform bacteria counts over a large area can be evaluated using a relatively simple geographic information system method. Land managers may find this method useful for targeting resources in relation to a particular water quality concern, focusing best management efforts, and maximizing benefits to water quality with minimal costs.

Circuit resistance training improves the atherogenic lipid profiles of persons with chronic paraplegia

BACKGROUND

People with chronic paraplegia frequently experience dyslipidemias characterized by depressed levels of high-density lipoprotein cholesterol (HDL-C) and elevated levels of low-density lipoprotein cholesterol (LDL-C). These abnormal lipid profiles and poor fitness levels increase their risk for cardiovascular disease.

METHODS

To test the hypothesis that circuit resistance exercise training improves both upper-extremity fitness and the atherogenic lipid profile in persons with chronic paraplegia, a homogeneous cohort of 5 men with neurologically complete spinal cord injuries at T6 to L1 underwent 3 months of exercise training using uninterrupted resistance and endurance exercises of the upper extremities. Training was performed 3 times a week on alternating days.

RESULTS

Results of graded arm exercise testing showed a 30.3% improvement in peak oxygen consumption (P < .01), a 33.5% increase in time to fatigue (P < .01) and a 30.4% increase in peak power output (P < .05). Pretraining total cholesterol levels (TC) were in the low-risk category and were nonsignificantly lowered following training. Similar nonsignificant reductions of plasma triglycerides averaging 12 mg/dL were attained. Conversely, a 25.9% lowering of LDL-C (P < .05) and 9.8% elevation of HDL-C (P < .05) were observed after training. These changes reduced the average LDL-C-to-HDL-C ratio by 1 unit (P < .05) and the TC-to-HDL-C ratio from 5.0 +/- 1.1 (mean +/- SD) to 3.9 +/- 0.7 (P < .05).

CONCLUSIONS

This change reflects a cardiovascular risk reduction of almost 25%; the TC/HDL-C declined from the high-risk score of 5.0 to near the desired score of 3.5. These findings support the beneficial effects of circuit exercise resistance training on fitness and atherogenic lipid profiles in persons with chronic paraplegia.

Modes, benefits, and risks of voluntary an delectrically induced exercise in persons with spinal cord injury

BACKGROUND

Sedentary lifestyles and physical deconditioning are commonly reported among persons with spinal cord injury (SCI), although many forms of exercise have been shown to be beneficial. For individuals unable to perform voluntary exercise, involuntary exercise by electrically stimulated contractions has been used to train individual body segments, invoke cycling movements with or without arm propulsion, and stimulate ambulation.

OBJECTIVE

To evaluate the benefits and risks associated with various modes of exercise in persons with SCI.

METHODS

Literature review.

FINDINGS

Electrical stimulation of local muscle sites increases muscle mass and circulation and favorably alters muscle fiber composition. Electrically stimulated cycling has been observed to improve fitness, lower-extremity circulation, and circulatory response to ischemia and to reverse cardiac muscle atrophy in persons with tetraplegia. Electrically stimulated ambulation improves upper-extremity endurance, lower-extremity circulation, and perception of body image. Studies of arm and wheelchair ergometry show increased arm endurance and decreased cardiovascular risks associated with hyperlipidemia, while resistance training of the upper extremities improves strength and endurance. Because autonomic hyperreflexia, orthostatic intolerance, thermal dysregulation, and fracture are associated with exercise in SCI, risk reduction strategies and prompt intervention are required.

CONCLUSIONS

Well-designed programs of exercise are beneficial for persons with tetraplegia and paraplegia. Risks and benefits vary with level of injury. Programs need to address prevention of and intervention for potential adverse effects associated with exercise in individuals with spinal cord dysfunction.

Enhanced inducible mGlu1alpha receptor expression in Chinese hamster ovary cells

Inducible expression of the group-I metabotropic glutamate receptor (mGlu1alpha) in Chinese hamster ovary cells allows for the study of receptor density dependent effects. However, expression levels attainable with this system are lower than those reported for various brain regions and achieved by conventional (constitutive) transfection. Thus, direct comparison of mGlu1alpha receptor-mediated responses in this inducible expression system with those for receptors expressed heterologously or in vivo is compounded. We show here that inducible expression can be selectively augmented by butyrate pretreatment to levels approaching those reported for cerebral tissue. Enhanced mGlu1alpha receptor protein levels, agonist-induced inositol phosphate accumulation, as well as single-cell inositol 1,4,5-trisphosphate production and intracellular Ca(2+) mobilization occurred following co-induction with butyrate. In contrast, endogenous purinoceptor function was unaffected. Importantly, the ability to titrate receptor expression by varying isopropyl beta-thiogalactoside concentration was retained. Sodium butyrate thus offers a simple and convenient method to enhance inducible gene expression to levels found in vivo.

Reassessment of the Ca2+ sensing property of a type I metabotropic glutamate receptor by simultaneous measurement of inositol 1,4,5-trisphosphate and Ca2+ in single cells

Transient transfection of Chinese hamster ovary or baby hamster kidney cells expressing the Group I metabotropic glutamate receptor mGlu1alpha with green fluorescent protein-tagged pleckstrin homology domain of phospholipase Cdelta1 allows real-time detection of inositol 1,4,5-trisphosphate. Loading with Fura-2 enables simultaneous measurement of intracellular Ca(2+) within the same cell. Using this technique we have studied the extracellular calcium sensing property of the mGlu1alpha receptor. Quisqualate, in extracellular medium containing 1.3 mm Ca(2+), increased inositol 1,4,5-trisphosphate in all cells. This followed a typical peak and plateau pattern and was paralleled by concurrent increases in intracellular Ca(2+) concentration. Under nominally Ca(2+)-free conditions similar initial peaks in inositol 1,4,5-trisphosphate and Ca(2+) concentration occurred with little change in either agonist potency or efficacy. However, sustained inositol 1,4,5-trisphosphate production was substantially reduced and the plateau in Ca(2+) concentration absent. Depletion of intracellular Ca(2+) stores using thapsigargin abolished quisqualate-induced increases in intracellular Ca(2+) and markedly reduced inositol 1,4,5-trisphosphate production. These data suggest that the mGlu1alpha receptor is not a calcium-sensing receptor because the initial response to agonist is not sensitive to extracellular Ca(2+) concentration. However, prolonged activation of phospholipase C requires extracellular Ca(2+), while the initial burst of activity is highly dependent on Ca(2+) mobilization from intracellular stores.

Single-cell imaging of graded Ins(1,4,5)P3 production following G-protein-coupled-receptor activation

The pleckstrin homology domain of phospholipase Cdelta1 (PH(PLCdelta)) binds Ins(1,4,5)P(3) and PtdIns(4,5)P(2) specifically, and can be used to detect changes in Ins(1,4,5)P(3) in single cells. A fusion construct of PH(PLCdelta) and enhanced green fluorescent protein (EGFP-PH(PLCdelta)) associates with the plasma membrane due to its association with PtdIns(4,5)P(2). However, PH(PLCdelta) has greater affinity for Ins(1,4,5)P(3) than PtdIns(4,5)P(2), and translocates to the cytosol as Ins(1,4,5)P(3) levels rise. Prolonged activation of group I metabotropic glutamate receptor 1alpha expressed in Chinese-hamster ovary cells or endogenous M(3) muscarinic receptors in SH-SY5Y neuroblastoma cells gave an initial transient peak in translocation, followed by a sustained plateau phase. This closely followed changes in cell population Ins(1,4,5)P(3) mass, but not PtdIns(4,5)P(2) levels, which decreased monophasically, as determined by radioreceptor assay. Translocation thus provides a real-time method to follow increases in Ins(1,4,5)P(3). Graded changes in Ins(1,4,5)P(3) in Chinese-hamster ovary-lac-mGlu1alpha cells could be detected with increasing glutamate concentrations, and dual loading with fura 2 and EGFP-PH(PLCdelta) showed that changes in intracellular Ca(2+) concentration closely paralleled Ins(1,4,5)P(3) production. Moreover, Ins(1,4,5)P(3) accumulation and intracellular Ca(2+) mobilization within single cells is graded in nature and dependent on both agonist concentration and receptor density.

Circuit training provides cardiorespiratory and strength benefits in persons with paraplegia

PURPOSE

This study tested the safety and the effects of circuit resistance training (CRT) on peak upper extremity cardiorespiratory endurance and muscle strength in chronic survivors of paraplegia due to spinal cord injury.

METHODS

Ten men with chronic neurologically complete paraplegia at the T5-L1 levels participated in the study. Subjects completed 12 wk of CRT, using a series of alternating isoinertial resistance exercises on a multi-station gym and high-speed, low-resistance arm ergometry. Peak arm ergometry tests, upper extremity isoinertial strength testing, and testing of upper extremity isokinetic strength were all performed before and after training.

RESULTS

None of the subjects suffered injury from exercise training. Significant increases were observed in peak oxygen consumption (29.7%, P < 0.01), time to fatigue (P < 0.01), and peak power output during arm testing (P < 0.05). Significant increases in isoinertial strength for the training maneuvers ranged from 11.9% to 30% (Ps < 0.01). Significant increases in isokinetic strength were experienced for shoulder joint internal rotation, extension, abduction, adduction, and horizontal adduction (Ps < 0.05).

CONCLUSION

Chronic survivors of paraplegia safely improve their upper extremity cardiorespiratory endurance and muscle strength when undergoing a short-term circuit resistance training program. Gains in fitness and strength exceeded those usually reported after either arm endurance exercise conditioning or strength training in this subject population.

Immune dysfunction and illness susceptibility after spinal cord injury: an overview of probable causes, likely consequences, and potential treatments

Information contained in the following monographs was presented as a symposium at the Annual Conference of the American Paraplegia Society in September 1999.

Known and plausible modulators of depressed immune functions following spinal cord injuries

Recent evidence suggests that depression of immune function occurs early after spinal cord injury (SCI) and is maintained thereafter. Deviations from immune function observed in healthy persons with intact neuraxes include natural killer cell number and cytotoxicity, T cell function and activation, macrophage phagocytosis, levels of interleukins (IL)-2 and -6, the soluble IL-2R receptor, and intracellular adhesion molecules. While a single etiology explaining these abnormalities has not been identified, decentralization of the autonomic nervous system is the most likely cause. Otherwise, many persons with SCI, who sustain episodic autonomic overstimulation, are among the most physically deconditioned of all humans, and often select a diet rich in fat and low in protein. All of these are associated with suppressed immune function in persons without SCI. Those with SCI may also be (over)exposed to drugs and medications that suppress immune function, including methylprednisolone administered immediately after traumatic injury. No evidence suggests that the immune profiles of persons with SCI favor disease and illness resistance. As opportunistic infections of the urinary tract, lungs, and skin represent major causes of morbidity for those aging with SCI, attention to, or intervention on, immune suppressive states, traits, behaviors, diets, and medications may represent a means through which host defenses of persons with SCI can be fortified and their illness proclivities reduced.

5-Hydroxytryptamine1A agonists: potential use in glaucoma. Evidence from animal studies

Various classes of compounds exist to lower intraocular pressure (IOP) in the treatment of glaucoma. None of them is ideal since some patients respond better than others and the side effects vary between individuals. New classes of compounds need to be introduced to allow the clinician greater scope for effective treatment of all patients. It is now generally agreed that the cause of ganglion cell dysfunction in glaucoma is likely to be multifactorial and that concentrating solely on reducing IOP is inadequate. Irrespective of the reason for the dysfunction, the future goal must be to attenuate cell death. This may be achieved with drugs that interact with components of the retina, and is termed 'neuroprotection'. Thus, drugs that can both reduce IOP and act as neuroprotectants would be ideal for the treatment of glaucoma. In this article we summarise studies on animals which show serotonergic 5-HT1A agonists to both reduce IOP when topically applied to the rabbit eye and blunt the damaging effect to the rat retina and ganglion cells induced by glutamate toxicity or ischaemia. Reduction of IOP occurs via stimulation of 5-HT1A receptors associated with the ciliary processes. Neuroprotection of retinal neurones appears to involve the interaction of 5-HT1A agonists with membrane sodium channels and/or 5-HT1A or even possibly 5-HT7 receptors. Various 5-HT1A agonists are used in patients to treat depression, so classes of these drugs have a proven safety profile for use in patients. The animal studies summarised in this article suggest that 5-HT1A agonists need to be considered as a new class of drugs for the treatment of glaucoma.

Flupirtine ameliorates ischaemic-like death of rat retinal ganglion cells by preventing calcium influx

The effect of flupirtine on the loss of retinal ganglion cells following transient elevation of intraocular pressure (experimental ischaemia) or NMDA-induced excitotoxicity was studied. Ischaemia (60 min) or intravitreal injection of NMDA (20 nmol) caused a decrease in Thy-1 mRNA and Thy-1 immunoreactivity which are associated with ganglion cells. Administration of flupirtine counteracted these changes. Moreover, flupirtine dose-dependently inhibited NMDA-induced 45Ca(2+) influx into cultured cortical neurones and retinal pieces in vitro with maximal inhibition being observed at 200 microM. A similar concentration of flupirtine failed to inhibit kainate-stimulated calcium influx into cultured cortical neurones. In addition, flupirtine had no significant effect on [3H]nitrendipine or [3H]diltiazem binding to cortical membranes. The present studies are consistent with previous findings which suggested flupirtine to act as a NMDA antagonist by a mechanism that still remains to be clarified.

Photoreceptors are preferentially affected in the rat retina following permanent occlusion of the carotid arteries

Carotid artery occlusion (two vessel occlusion; 2-VO) for 3 or 9 months causes a suppression of the electroretinogram. However, after 3 months the retinal morphology appears unaffected judging from the localisation of GABA, ChAT, alpha PKC, Thy-1 and GFAP immunoreactivities. Moreover, no difference in NMDA-R1, opsin or Thy-1 mRNA levels were detected. In contrast, after 9 months 2-VO photoreceptor degeneration occurred as indicated by thinning of the outer nuclear layer and reduced Ret-P1 immunoreactivity. All other immunoreactivities appeared normal. These findings were supported by analysis of retinal mRNA levels. We conclude that the major effect of prolonged 2-VO is photoreceptor degeneration.

The 5-HT(1A)Receptor agonist 8-OH-DPAT lowers intraocular pressure in normotensive NZW rabbits

The aims of this study were first to investigate the effect of topical instillation of the 5-HT(1A)receptor agonist 8-OH-DPAT on intraocular pressure (IOP) in normotensive rabbits and second to establish whether the drug reaches the aqueous humour of treated and contralateral eyes at concentrations sufficient to activate ciliary epithelial 5-HT(1A)receptors. Following topical unilateral instillation of (+/-), (+) or (-)8-OH-DPAT, the IOP of rabbits was measured using an applanation tonometer. For the penetration study, [(3)H]8-OH-DPAT was instilled into one eye of each rabbit. Animals were killed after 30 min and the radioactive content of treated and contralateral ocular tissues was assessed. Administration of (+/-)8-OH-DPAT caused dose-dependent decreases in IOP in treated eyes of rabbits during the light and dark. The full 5-HT(1A)agonist (+)8-OH-DPAT was shown to be a more effective hypotensive agent than the partial agonist (-)8-OH-DPAT. The effect of (+/-)8-OH-DPAT on IOP was blocked by pretreatment with pindolol, a mixed 5-HT(1A)antagonist/beta-blocker, but not by the specific beta-blocker betaxolol. After instillation of [(3)H]8-OH-DPAT, peak levels of radioactivity were found in the cornea, followed by similar amounts in the iris-ciliary body and aqueous. There was negligible radioactivity present in tissues of the contralateral eye. This study demonstrates that topical administration of the 5-HT(1A)agonist 8-OH-DPAT dose-dependently decreases IOP in normotensive rabbits during the light and dark. The action of 8-OH-DPAT is presumably local to the anterior uvea as IOP was reduced only in treated eyes and [(3)H]8-OH-DPAT failed to reach the contralateral eye after unilateral instillation. Moreover, since 5-HT(1A)receptors are located in the rabbit ciliary epithelium and the effect of 8-OH-DPAT is blocked by a recognized 5-HT(1A)antagonist, the mechanisms of action of 8-OH-DPAT may well involve a decreased secretion of aqueous humour.

Topically applied betaxolol attenuates NMDA-induced toxicity to ganglion cells and the effects of ischaemia to the retina

The present results show that topically applied Betoptic(R)(0.5% betaxolol) to the rabbit or rat eye reaches the retina and can counteract the detrimental effects caused by ischaemia/reperfusion or N -methyl- d -aspartate (NMDA)-induced insults to the retina. Betaxolol is a beta(1)-adrenergic blocker but its neuroprotective action is generally thought to be due to its calcium channel blocking properties. Support for this view comes from studies on cultures of cortical neurones where it was found that betaxolol attenuated the NMDA-induced influx of(45)Ca(2+)while beta-adrenoreceptor agonists were ineffective. Topically applied Betoptic(R)to the rabbit eye was observed to reach the retina in maximal amounts within 60 min. Some of the substance was also found in the contralateral retina of the untreated eye suggesting that the agent reaches the retina by local systemic and retinal circulation. Concurrent treatment with Latanoprost(R)did not result in a greater amount of betaxolol reaching the retina. An ophthalmodynamometric procedure, which raises the intraocular pressure, was used to apply an ischaemic insult to the rabbit retina. After three days of reperfusion the b-wave of the electroretinogram was reduced by an average of 59% and the choline acetyltransferase immunoreactivity in the retina was almost obliterated. However, when experiments were carried out on animals which had been treated with one drop of Betoptic(R) twice daily for 4 weeks before ischaemia and also during the reperfusion phase, the reductions in both the b-wave of the electroretinogram and retinal choline acetyltransferase immunoreactivity due to ischaemia/reperfusion were greatly attenuated. Intravitreal injection of NMDA into the rat eye caused a decrease in the immunostaining for Thy-1 antigen which is associated with ganglion cells. The Thy-1 mRNA level was also reduced as was the mRNA for the common subunit of the NMDA receptor, the NR1 subunit. However, in animals subjected to a topical Betoptic(R)regime, before and after intravitreal injection of NMDA, the decreases in the mRNA levels of Thy-1 and NR1 were significantly attenuated.

Neuroprotection in relation to retinal ischemia and relevance to glaucoma

Management of glaucoma is directed at the control of intraocular pressure (IOP), yet it is recognized now that increased IOP isjust an important risk factor in glaucoma. Therapy that prevents the death of ganglion cells is the main goal of treatment, but an understanding of the causes of ganglion cell death and precisely how it occurs remains speculative. Present information supports the working hypothesis that ganglion cell death may result from a particular form of ischemia. Support for this view comes from the fact that not all types of retinal ischemia lead to the pathologic findings seen in glaucomatous retinas or to cupping in the optic disk area. Moreover, in animal experiments in which ischemia is caused by elevated IOP, a retinal abnormality similar to that seen in true glaucoma is produced, whereas after occlusion of the carotid arteries a different pattern of damage is found. In ischemia, glutamate is released, and this initiates the death of neurons that contain ionotropic glutamate (NMDA) receptors. Elevated glutamate levels exist in the vitreous humor of patients with glaucoma, and NMDA receptors exist on ganglion cells and a subset of amacrine cells. Experimental studies have shown that a variety of agents can be used to prevent the death of retinal neurons (particularly ganglion cells) induced by ischemia. These agents are generally those that block NMDA receptors to prevent the action of the released glutamate or substances that interfere with the subsequent cycle of events that lead to cell death. The major causes of cell death after activation of NMDA receptors are the influx of calcium into cells and the generation of free radicals. Substances that prevent this cascade of events are, therefore, often found to act as neuroprotective agents. For a substance to have a role as a neuroprotective agent in glaucoma, it would ideally be delivered topically to the eye and used repeatedly. It is, therefore, of interest that betaxolol, a beta-blocker presently used to reduce IOP in humans, also has calcium channel-blocking functions. Moreover, experimental studies show that betaxolol is an efficient neuro protective agent against retinal ischemia in animals, when injected directly into the eye or intraperitoneally.

Assessment of Thy-1 mRNA levels as an index of retinal ganglion cell damage

PURPOSE

Thy-1 is primarily, if not entirely, expressed by the ganglion cells within the retina. This knowledge was used to index ganglion cell death after ischemia and excitotoxicity by studying changes in Thy-1 mRNA levels.

METHODS

Insults to the rat retina were delivered either by elevation of intraocular pressure for 60 minutes or by intravitreal injection of N-methyl-D-aspartate (NMDA). After a defined period, changes in Thy-1 immunoreactivity and mRNA levels of Thy-1 and NR1 (NMDA receptor subunit) were used to index ganglion cell sensitivity to damage. Opsin mRNA levels were used as an internal control because photoreceptors lack NMDA receptors.

RESULTS

Retinal Thy-1 immunoreactivity, associated with the ganglion cell and inner plexiform layers, is reduced by ischemia or intravitreal injections of NMDA in a dose-dependent manner. Using a semi-quantitative polymerase chain reaction (reverse transcription-polymerase chain reaction) methodology, the levels of total retinal Thy-1 and NR1 mRNAs were shown to be dramatically reduced after both transient ischemia and intravitreal injection of NMDA. The effect of NMDA was found to be both time- and dose-dependent. In contrast, no change occurred in the levels of opsin mRNA unless high levels of NMDA (200 nmoles) were administered.

CONCLUSIONS

Ischemia and NMDA-induced excitotoxicity caused retinal ganglion cell destruction, but the photoreceptors were unaffected. Measurement of total retinal Thy-1 mRNA levels provides a useful way of following ganglion cell death especially when combined with immunohistochemical localization of Thy-1. Additionally, the effect on other retinal cell types such as the photoreceptors can be followed in concert using this technique.

NMDA induces BDNF expression in the albino rat retina in vivo

The effect of an intravitreal injection of NMDA on the expression of brain-derived neurotrophic factor (BDNF) in retinal ganglion cells was investigated in rats. Forty-eight hours after intravitreal injection of NMDA retinal ganglion cell BDNF immunoreactivity was practically obliterated, as was the choline acetyltransferase (ChAT) immunoreactivity associated with a subset of amacrine cells. However, 2h following treatment with NMDA the BDNF immunoreactivity and BDNF mRNA associated with the ganglion cells was enhanced while the amacrine cell ChAT immunoreactivity was clearly reduced and the levels of mRNA coding for rhodopsin and Thy-1 did not change. However, 4h after NMDA injection the increase in BDNF mRNA was now no longer apparent. The results show that synthesis of BDNF is increased in the ganglion cells immediately following an insult by NMDA. It is suggested that this is a natural protective mechanism of rat retinal ganglion cells.

The potential of neuroprotection in glaucoma treatment

Visual field loss in glaucoma is due to death of retinal ganglion cells. Reducing or slowing down the loss of ganglion cells in glaucoma, a concept known as neuroprotection, would appear to be the only way forward. This does not imply that treatment of risk factors, such as elevated intraocular pressure, must not be continuously implemented. In this paper we point out that very little is known about the mechanisms of ganglion cell death in glaucoma and that data derived from studies on the "ideal animal model for glaucoma" must not be overemphasized. We also propose that the death processes of neurones in various diseases are fundamentally the same but vary in cause. Experimental data show that the death rate of neuronal populations is dependent on the impact of the insult and that neuroprotectants are more likely to benefit a patient in diseases in which the neurones die slowly, as in glaucoma, than in a disease in which the death of a set of neurones is rapid. We conclude that if a putative neuroprotectant can be administered in such a way that it reaches the retina in appropriate amounts and has insignificant side effects, it is likely to attenuate ganglion cell death and thus benefit the glaucoma patient.

Nonselective debridement and antimicrobial cleansing of a venting ductal breast carcinoma

A woman with a moderately differentiated carcinoma that erupted through the skin and amputated her breast was treated with whirlpool, topical antimicrobials, radiation, and chemotherapy. The draining, necrotic, and septic wound was treated for 5 months with a whirlpool containing dilute povidone-iodine solution and intravenous chemotherapy. Wet bandages, necrotic tissue, and softened eschar were removed by whirlpool agitation or mechanically debrided. To start treatment the wound was dressed with Debrisan crystals and sterile gauze for 1 week. Afterwards, wet-to-dry dressings wetted with Dakin's solution were applied. Tissue ingrowth at the wound margin started after 2 weeks, with whirlpool treatments effecting a tissue-reddening hyperemia. Wound drainage ceased after 2 months, with granulation and revascularization resulting. Eleven months later the wound was closed, aseptic, and undergoing dry flaking. The patient was cancer free with a completely healed wound 2 years after treatment. In this case, nonspecific debridement using whirlpool and topical antimicrobials promoted healing of an open fungating wound from a breast carcinoma.

Melatonin counteracts ischemia-induced apoptosis in human retinal pigment epithelial cells

PURPOSE

To investigate whether the neurohormone melatonin can prevent apoptosis caused by deprivation of oxygen, glucose, and serum (experimental ischemia) in cultured human retinal pigment (RPE) cells.

METHODS

Cultures of human RPE cells established from a variety of donors were grown to passage four and then subjected to experimental ischemia, with or without various substances, for up to 72 hours. Cells were examined for morphologic changes and breakdown of DNA, assessed by TdT-dTUP terminal nick-end labeling (TUNEL) and agarose gel electrophoresis. Changes in transcription and translation of various proto-oncogenes (bcl-2, TIAR, ICH-1S/1) were assessed by analysis of mRNA and protein levels, respectively. The effect of various substances on the iron-ascorbate-induced formation of reactive oxygen species (ROS) in chick retinal dissociates was also investigated.

RESULTS

Cultured human RPE cells on coverslips that were incubated in serum-free medium, glucose, and oxygen remained viable for up to 40 hours. Thereafter, there was a steady decrease in cell numbers and an increase in the number of cells labeled by the TUNEL method. By 72 hours 65% of cells remained attached to the coverslips, of which approximately 65% were TUNEL positive. Furthermore, most of the experimental ischemia-treated cells exhibited a shrunken appearance typical of apoptosis. Fragmentation of the DNA from cells in which ischemia was induced for 72 hours was also confirmed by agarose gel electrophoresis. Inclusion of 100 microM melatonin significantly decreased the amount of apoptotic cell nuclei after ischemia, but the effect was mild compared with that of fetal calf serum, which almost completely counteracted cell death. The action of melatonin was not prevented by 0.01 mM to 1 mM luzindole, a melatonin receptor antagonist. In addition, 100 microM ascorbate did not counteract ischemia-induced apoptosis. Treatment of RPE cells with 100 microM flupirtine gluconate for 72 hours caused an upregulation of the proto-oncogene protein Bcl-2 and a decrease in TIAR and ICH-1L proteins compared with that in control cells. Melatonin at 100 microM had no such effect. The levels of the mRNA transcripts for ICH-1L relative to those for ICH-1S were significantly decreased in cultures treated with 100 microM flupirtine or 100 microM melatonin when compared with levels in control cells. However, the effect of flupirtine was greater than that of melatonin. Ten micromolar ascorbate and 5 microM iron stimulated the formation of ROS in chick retinal cell dissociates. Ascorbate, melatonin, and flupirtine (all at 100 microM) blunted this response in the order flupirtine > melatonin >> ascorbate. Luzindole had no effect, alone or in the presence of melatonin.

CONCLUSIONS

The presented data show that melatonin counteracted ischemia-induced apoptosis in human RPE cells by a process that seemed to be independent of melatonin receptors. Moreover, melatonin and flupirtine counteracted iron-ascorbate-induced ROS formation and decreased the ratio of mRNA for ICH-1L and ICH-1S. However, melatonin was less potent than flupirtine in its action in each case, which suggests that either the two compounds act on different signaling pathways or that they act on the same pathway with differing potency. The failure to detect an effect of melatonin on the levels of Bcl-2, ICH-1L, and TIAR proteins when compared with the effect of flupirtine was probably caused by the sensitivity of the procedures. It is suggested that substances that can prevent ROS formation can potentially nullify apoptotic cell death, but this is difficult to detect experimentally when the substance has only a mild effect, such as in the case of ascorbate.