A Transient Printed Soil Decomposition Sensor Based on a Biopolymer Composite Conductor

Soil health is one of the key factors in determining the sustainability of global agricultural systems and the stability of natural ecosystems. Microbial decomposition activity plays an important role in soil health; and gaining spatiotemporal insights into this attribute is critical for understanding soil function as well as for managing soils to ensure agricultural supply, stem biodiversity loss, and mitigate climate change. Here, a novel in situ electronic soil decomposition sensor that relies on the degradation of a printed conductive composite trace utilizing the biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) as a binder is presented. This material responds selectively to microbially active environments with a continuously varying resistive signal that can be readily instrumented with low-cost electronics to enable wide spatial distribution. In soil, a correlation between sensor response and intensity of microbial decomposition activity is observed and quantified by comparison with respiration rates over 14 days, showing that devices respond predictably to both static conditions and perturbations in general decomposition activity.

Mobile phone use is associated with higher smallholder agricultural productivity in Tanzania, East Africa

Mobile phone use is increasing in Sub-Saharan Africa, spurring a growing focus on mobile phones as tools to increase agricultural yields and incomes on smallholder farms. However, the research to date on this topic is mixed, with studies finding both positive and neutral associations between phones and yields. In this paper we examine perceptions about the impacts of mobile phones on agricultural productivity, and the relationships between mobile phone use and agricultural yield. We do so by fitting multilevel statistical models to data from farmer-phone owners (n = 179) in 4 rural communities in Tanzania, controlling for site and demographic factors. Results show a positive association between mobile phone use for agricultural activities and reported maize yields. Further, many farmers report that mobile phone use increases agricultural profits (67% of respondents) and decreases the costs (50%) and time investments (47%) of farming. Our findings suggest that there are opportunities to target policy interventions at increasing phone use for agricultural activities in ways that facilitate access to timely, actionable information to support farmer decision making.

Leaf temperatures mediate alpine plant communities' response to a simulated extended summer

We use a quantitative model of photosynthesis to explore leaf-level limitations to plant growth in an alpine tundra ecosystem that is expected to have longer, warmer, and drier growing seasons. The model is parameterized with abiotic and leaf trait data that is characteristic of two dominant plant communities in the alpine tundra and specifically at the Niwot Ridge Long Term Ecological Research Site: the dry and wet meadows. Model results produce realistic estimates of photosynthesis, nitrogen-use efficiency, water-use efficiency, and other gas exchange processes in the alpine tundra. Model simulations suggest that dry and wet meadow plant species do not significantly respond to changes in the volumetric soil moisture content but are sensitive to variation in foliar nitrogen content. In addition, model simulations indicate that dry and wet meadow species have different maximum rates of assimilation (normalized for leaf nitrogen content) because of differences in leaf temperature. These differences arise from the interaction of plant height and the abiotic environment characteristic of each plant community. The leaf temperature of dry meadow species is higher than wet meadow species and close to the optimal temperature for photosynthesis under current conditions. As a result, 2°C higher air temperatures in the future will likely lead to declines in dry meadow species' carbon assimilation. On the other hand, a longer and warmer growing season could increase nitrogen availability and assimilation rates in both plant communities. Nonetheless, a temperature increase of 4°C may lower rates of assimilation in both dry and wet meadow plant communities because of higher, and suboptimal, leaf temperatures.

Managing Carbon on Federal Public Lands: Opportunities and Challenges in Southwestern Colorado

Federal lands in the United States have been identified as important areas where forests could be managed to enhance carbon storage and help mitigate climate change. However, there has been little work examining the context for decision making for carbon in a multiple-use public land environment, and how science can support decision making. This case study of the San Juan National Forest and the Bureau of Land Management Tres Rios Field Office in southwestern Colorado examines whether land managers in these offices have adequate tools, information, and management flexibility to practice effective carbon stewardship. To understand how carbon was distributed on the management landscape we added a newly developed carbon map for the SJNF-TRFO area based on Landsat TM texture information (Kelsey and Neff in Remote Sens 6:6407-6422. doi: 10.3390/rs6076407 , 2014). We estimate that only about 22 % of the aboveground carbon in the SJNF-TRFO is in areas designated for active management, whereas about 38 % is in areas with limited management opportunities, and 29 % is in areas where natural processes should dominate. To project the effects of forest management actions on carbon storage, staff of the SJNF are expected to use the Forest Vegetation Simulator (FVS) and extensions. While identifying FVS as the best tool generally available for this purpose, the users and developers we interviewed highlighted the limitations of applying an empirically based model over long time horizons. Future research to improve information on carbon storage should focus on locations and types of vegetation where carbon management is feasible and aligns with other management priorities.

The contribution of occult precipitation to nutrient deposition on the west coast of South Africa

The Strandveld mediterranean-ecosystem of the west coast of South Africa supports floristically diverse vegetation growing on mostly nutrient-poor aeolian sands and extending from the Atlantic Ocean tens of kilometers inland. The cold Benguela current upwelling interacts with warm onshore southerly winds in summer causing coastal fogs in this region. We hypothesized that fog and other forms of occult precipitation contribute moisture and nutrients to the vegetation. We measured occult precipitation over one year along a transect running inland in the direction of the prevailing wind and compared the nutrient concentrations with those in rainwater. Occult deposition rates of P, N, K, Mg, Ca, Na, Al and Fe all decreased with distance from the ocean. Furthermore, ratios of cations to Na were similar to those of seawater, suggesting a marine origin for these. In contrast, N and P ratios in occult precipitation were higher than in seawater. We speculate that this is due to marine foam contributing to occult precipitation. Nutrient loss in leaf litter from dominant shrub species was measured to indicate nutrient demand. We estimated that occult precipitation could meet the demand of the dominant shrubby species for annual N, P, K and Ca. Of these species, those with small leaves intercepted more moisture and nutrients than those with larger leaves and could take up foliar deposits of glycine, NO3(-), NH4(+) and Li (as tracer for K) through leaf surfaces. We conclude that occult deposition together with rainfall deposition are potentially important nutrient and moisture sources for the Strandveld vegetation that contribute to this vegetation being floristically distinct from neighbouring nutrient-poor Fynbos vegetation.

Short and long-term carbon balance of bioenergy electricity production fueled by forest treatments

BACKGROUND

Forests store large amounts of carbon in forest biomass, and this carbon can be released to the atmosphere following forest disturbance or management. In the western US, forest fuel reduction treatments designed to reduce the risk of high severity wildfire can change forest carbon balance by removing carbon in the form of biomass, and by altering future potential wildfire behavior in the treated stand. Forest treatment carbon balance is further affected by the fate of this biomass removed from the forest, and the occurrence and intensity of a future wildfire in this stand. In this study we investigate the carbon balance of a forest treatment with varying fates of harvested biomass, including use for bioenergy electricity production, and under varying scenarios of future disturbance and regeneration.

RESULTS

Bioenergy is a carbon intensive energy source; in our study we find that carbon emissions from bioenergy electricity production are nearly twice that of coal for the same amount of electricity. However, some emissions from bioenergy electricity production are offset by avoided fossil fuel electricity emissions. The carbon benefit achieved by using harvested biomass for bioenergy electricity production may be increased through avoided pyrogenic emissions if the forest treatment can effectively reduce severity.

CONCLUSION

Forest treatments with the use of harvested biomass for electricity generation can reduce carbon emissions to the atmosphere by offsetting fossil fuel electricity generation emissions, and potentially by avoided pyrogenic emissions due to reduced intensity and severity of a future wildfire in the treated stand. However, changes in future wildfire and regeneration regimes may affect forest carbon balance and these climate-induced changes may influence forest carbon balance as much, or more, than bioenergy production.

Twentieth century carbon stock changes related to Piñon-Juniper expansion into a black sagebrush community

BACKGROUND

Increases in the spatial extent and density of woody plants relative to herbaceous species have been observed across many ecosystems. These changes can have large effects on ecosystem carbon stocks and therefore are of interest for regional and national carbon inventories and for potential carbon sequestration or management activities. However, it is challenging to estimate the effect of woody plant encroachment on carbon because aboveground carbon stocks are very heterogeneous spatially and belowground carbon stocks exhibit complex and variable responses to changing plant cover. As a result, estimates of carbon stock changes with woody plant cover remain highly uncertain. In this study, we use a combination of plot- and remote sensing-based techniques to estimate the carbon impacts of piñon and juniper (PJ) encroachment in SE Utah across a variety of spatial scales with a specific focus on the role of spatial heterogeneity in carbon estimates.

RESULTS

At a plot scale (300 m2) areas piñon juniper (PJ) encroached areas had 0.26 kg C m-2 less understory vegetation carbon compared to un-encroached sites. This lower amount of carbon was offset by an average of 1.82 kg C m-2 higher carbon in PJ vegetation and 0.50 kg m-2 of C in PJ surface-litter carbon. Soil mineral carbon stocks were unaffected by woody plant cover and density. Aboveground carbon stocks were highly dependent on PJ vegetation density. At a 300 m2 plot-scale, plots with low and high density of PJ forest had 1.40 kg C m-2 and 3.69 kg m-2 more carbon than the un-encroached plot. To examine how these 300 m2 variations influence landscape scale C estimates, historical and contemporary aerial photos were analyzed to develop forest density maps in order to estimate above ground PJ associated C stock changes in a 25 ha area. This technique yielded an average estimate of 1.43 kg m-2 of C accumulation with PJ encroachment. Combining this estimate with analysis of tree growth increments from dendrochronologies, we estimate that these PJ stands are accumulating aboveground C at an annual rate of 0.02 kg C m-2 with no slowing of this rate in healthy PJ. This result is in contrast to what has been observed in large areas of drought related PJ mortality, where C accumulation has ceased.

CONCLUSIONS

These results illustrate that the encroachment of PJ forests in SE Utah over the last century has resulted in a large (and ongoing) accumulation of carbon in PJ trees and surface litter. However, the magnitude of the increase depends to on the density of vegetation across the landscape and the health of forest stands. Both management activities that remove forest carbon and forest mortality due to drought or wildfire have the potential to quickly reverse the multi-decadal accumulation of carbon in these stands.

What controls plant nutrient use in high elevation ecosystems?

The importance of rock-derived mineral nutrients (P, K, Mn, Mg, and Ca) in plant physiological function is well established. However, one important and relatively unexplored question is whether or not the same rules of plant nutrient use efficiency apply to these essential elements even if they are not limiting to primary production. We examined conifer growth and nutrient use dynamics across sites with contrasting geologies (sedimentary and volcanic) that vary in both rock-derived mineral nutrient and N availability. Differences in bedrock geochemistry generally corresponded to differences in available soil nutrients, such that the volcanic site tended to have greater available nutrients. Foliar nutrient concentrations reflected both differences in bedrock chemistry and indices of available soil nutrients for P, K, and Mn. Aboveground biomass production did not follow expected patterns and was greater for trees growing on low nutrient sites, but only with respect to the annual woody increment. Fine litter production did not differ between sites. Finally, we found evidence for trade-offs between two commonly examined components of nutrient use efficiency (NUE): nutrient productivity (A n) and mean residence time of nutrients. However, we did not find evidence for higher plant NUE in soils with lower nutrient availability for N or rock-derived nutrients.

Water and heat transport in boreal soils: implications for soil response to climate change

Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4°C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30 years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate.

Soil carbon storage responses to expanding pinyon-juniper populations in southern Utah

Over the past several decades, the expansion and thickening of woodlands in the western United States has caused a range of ecological changes. Woody expansion often leads to increases in soil organic matter (SOM) pools with implications for both biogeochemical cycling and ecological responses to management strategies aimed at restoration of rangeland ecosystems. Here we directly measure C and N stocks and use simple non-steady-state models to quantify the dynamics of soil C accumulation under and around trees of varied ages in southern Utah woodlands. In the two pinyon-juniper forests of Grand Staircase Escalante National Monument studied here, we found approximately 3 kg C/m2 and approximately 0.12 kg N/m2 larger C and N stocks in soils under pinyon canopies compared to interspace sites. These apparent increases in soil C and N stocks under woody plant species were dominated by elevated SOM in the surface 10 cm of soil, particularly within non-mineral-associated organic fractions. The most significant accumulation of C was in the >850 microm fraction, which had an estimated C residence time of <20 yr. Rates of carbon accumulation following pinyon-juniper expansion appear to be dominated by changes in this fast-cycling surface soil fraction. In contrast, we found that after separating >850 microm organic matter from the remaining light fraction (LF), C had residence times of approximately 400 yr and mineral-associated (MA) soil C had residence times of approximately 600 yr. As a result, we calculate that input rates to the LF and MA pools to be 10 +/- 1 and 0.68 +/- 0.15 g m(-2) yr(-1) (mean +/- SE), respectively. These findings suggest that one consequence of management activities aimed at the reduction of pinyon-juniper biomass may be a relatively rapid loss of soil C and N pools associated with the >850 microm fraction. The temporal dynamics of the <850 microm pools suggest that carbon and nitrogen continue to accumulate in these fractions, albeit at very slow rates, and suggest that multidecadal storage of C following tree recruitment is limited to relatively small, subsurface fractions of the total soil C pool.

Multiscale analysis of tree cover and aboveground carbon stocks in pinyon-juniper woodlands

Regional, high-resolution mapping of vegetation cover and biomass is central to understanding changes to the terrestrial carbon (C) cycle, especially in the context of C management. The third most extensive vegetation type in the United States is pinyon-juniper (P-J) woodland, yet the spatial patterns of tree cover and aboveground biomass (AGB) of P-J systems are poorly quantified. We developed a synoptic remote-sensing approach to scale up pinyon and juniper projected cover (hereafter "cover") and AGB field observations from plot to regional levels using fractional photosynthetic vegetation (PV) cover derived from airborne imaging spectroscopy and Landsat satellite data. Our results demonstrated strong correlations (P < 0.001) between field cover and airborne PV estimates (r2 = 0.92), and between airborne and satellite PV estimates (r2 = 0.61). Field data also indicated that P-J AGB can be estimated from canopy cover using a unified allometric equation (r2 = 0.69; P < 0.001). Using these multiscale cover-AGB relationships, we developed high-resolution, regional maps of P-J cover and AGB for the western Colorado Plateau. The P-J cover was 27.4% +/- 9.9% (mean +/- SD), and the mean aboveground woody C converted from AGB was 5.2 +/- 2.0 Mg C/ha. Combining our data with the southwest Regional Gap Analysis Program vegetation map, we estimated that total contemporary woody C storage for P-J systems throughout the Colorado Plateau (113 600 km2) is 59.0 +/- 22.7 Tg C. Our results show how multiple remote-sensing observations can be used to map cover and C stocks at high resolution in drylands, and they highlight the role of P-J ecosystems in the North American C budget.

The earliest stages of ecosystem succession in high-elevation (5000 metres above sea level), recently deglaciated soils

Global climate change has accelerated the pace of glacial retreat in high-latitude and high-elevation environments, exposing lands that remain devoid of vegetation for many years. The exposure of 'new' soil is particularly apparent at high elevations (5000 metres above sea level) in the Peruvian Andes, where extreme environmental conditions hinder plant colonization. Nonetheless, these seemingly barren soils contain a diverse microbial community; yet the biogeochemical role of micro-organisms at these extreme elevations remains unknown. Using biogeochemical and molecular techniques, we investigated the biological community structure and ecosystem functioning of the pre-plant stages of primary succession in soils along a high-Andean chronosequence. We found that recently glaciated soils were colonized by a diverse community of cyanobacteria during the first 4-5 years following glacial retreat. This significant increase in cyanobacterial diversity corresponded with equally dramatic increases in soil stability, heterotrophic microbial biomass, soil enzyme activity and the presence and abundance of photosynthetic and photoprotective pigments. Furthermore, we found that soil nitrogen-fixation rates increased almost two orders of magnitude during the first 4-5 years of succession, many years before the establishment of mosses, lichens or vascular plants. Carbon analyses (pyrolysis-gas chromatography/mass spectroscopy) of soil organic matter suggested that soil carbon along the chronosequence was of microbial origin. This indicates that inputs of nutrients and organic matter during early ecosystem development at these sites are dominated by microbial carbon and nitrogen fixation. Overall, our results indicate that photosynthetic and nitrogen-fixing bacteria play important roles in acquiring nutrients and facilitating ecological succession in soils near some of the highest elevation receding glaciers on the Earth.

Molecular C dynamics downstream: the biochemical decomposition sequence and its impact on soil organic matter structure and function

Advances in spectroscopic and other chemical methods have greatly enhanced our ability to characterize soil organic matter chemistry. As a result, the molecular characteristics of soil C are now known for a range of ecosystems, soil types, and management intensities. Placing this knowledge into a broader ecological and management context is difficult, however, and remains one of the fundamental challenges of soil organic matter research. Here we present a conceptual model of molecular soil C dynamics to stimulate inter-disciplinary research into the ecological implications of molecular C turnover and its management- and process-level controls. Our model describes three properties of soil C dynamics: 1) soil size fractions have unique molecular patterns that reflect varying degrees of biological and physical control over decomposition; 2) there is a common decomposition sequence independent of plant inputs or other ecosystem properties; and 3) molecular decomposition sequences, although consistent, are not uniform and can be altered by processes that accelerate or slow the microbial transformation of specific molecules. The consequences of this model include several key points. First, lignin presents a constraint to decomposition of plant litter and particulate C (>53 microm) but exerts little influence on more stable mineral-associated soil fractions <53 microm. Second, carbon stabilized onto mineral fractions has a distinct composition related more to microbially processed organic matter than to plant-related compounds. Third, disturbances, such as N fertilization and tillage, which alter decomposition rates, can have "downstream effects"; that is, a disturbance that directly alters the molecular dynamics of particulate C may have a series of indirect effects on C stabilization in silt and clay fractions.

Estimates of CO2 from fires in the United States: implications for carbon management

BACKGROUND

Fires emit significant amounts of CO2 to the atmosphere. These emissions, however, are highly variable in both space and time. Additionally, CO2 emissions estimates from fires are very uncertain. The combination of high spatial and temporal variability and substantial uncertainty associated with fire CO2 emissions can be problematic to efforts to develop remote sensing, monitoring, and inverse modeling techniques to quantify carbon fluxes at the continental scale. Policy and carbon management decisions based on atmospheric sampling/modeling techniques must account for the impact of fire CO2 emissions; a task that may prove very difficult for the foreseeable future. This paper addresses the variability of CO2 emissions from fires across the US, how these emissions compare to anthropogenic emissions of CO2 and Net Primary Productivity, and the potential implications for monitoring programs and policy development.

RESULTS

Average annual CO2 emissions from fires in the lower 48 (LOWER48) states from 2002-2006 are estimated to be 213 (+/- 50 std. dev.) Tg CO2 yr-1 and 80 (+/- 89 std. dev.) Tg CO2 yr-1 in Alaska. These estimates have significant interannual and spatial variability. Needleleaf forests in the Southeastern US and the Western US are the dominant source regions for US fire CO2 emissions. Very high emission years typically coincide with droughts, and climatic variability is a major driver of the high interannual and spatial variation in fire emissions. The amount of CO2 emitted from fires in the US is equivalent to 4-6% of anthropogenic emissions at the continental scale and, at the state-level, fire emissions of CO2 can, in some cases, exceed annual emissions of CO2 from fossil fuel usage.

CONCLUSION

The CO2 released from fires, overall, is a small fraction of the estimated average annual Net Primary Productivity and, unlike fossil fuel CO2 emissions, the pulsed emissions of CO2 during fires are partially counterbalanced by uptake of CO2 by regrowing vegetation in the decades following fire. Changes in fire severity and frequency can, however, lead to net changes in atmospheric CO2 and the short-term impacts of fire emissions on monitoring, modeling, and carbon management policy are substantial.

Africa and the global carbon cycle

The African continent has a large and growing role in the global carbon cycle, with potentially important climate change implications. However, the sparse observation network in and around the African continent means that Africa is one of the weakest links in our understanding of the global carbon cycle. Here, we combine data from regional and global inventories as well as forward and inverse model analyses to appraise what is known about Africa's continental-scale carbon dynamics. With low fossil emissions and productivity that largely compensates respiration, land conversion is Africa's primary net carbon release, much of it through burning of forests. Savanna fire emissions, though large, represent a short-term source that is offset by ensuing regrowth. While current data suggest a near zero decadal-scale carbon balance, interannual climate fluctuations (especially drought) induce sizeable variability in net ecosystem productivity and savanna fire emissions such that Africa is a major source of interannual variability in global atmospheric CO2. Considering the continent's sizeable carbon stocks, their seemingly high vulnerability to anticipated climate and land use change, as well as growing populations and industrialization, Africa's carbon emissions and their interannual variability are likely to undergo substantial increases through the 21st century.

The Impact of Boreal Forest Fire on Climate Warming

We report measurements and analysis of a boreal forest fire, integrating the effects of greenhouse gases, aerosols, black carbon deposition on snow and sea ice, and postfire changes in surface albedo. The net effect of all agents was to increase radiative forcing during the first year (34 +/- 31 Watts per square meter of burned area), but to decrease radiative forcing when averaged over an 80-year fire cycle (-2.3 +/- 2.2 Watts per square meter) because multidecadal increases in surface albedo had a larger impact than fire-emitted greenhouse gases. This result implies that future increases in boreal fire may not accelerate climate warming.

Variable effects of nitrogen additions on the stability and turnover of soil carbon

Soils contain the largest near-surface reservoir of terrestrial carbon and so knowledge of the factors controlling soil carbon storage and turnover is essential for understanding the changing global carbon cycle. The influence of climate on decomposition of soil carbon has been well documented, but there remains considerable uncertainty in the potential response of soil carbon dynamics to the rapid global increase in reactive nitrogen (coming largely from agricultural fertilizers and fossil fuel combustion). Here, using 14C, 13C and compound-specific analyses of soil carbon from long-term nitrogen fertilization plots, we show that nitrogen additions significantly accelerate decomposition of light soil carbon fractions (with decadal turnover times) while further stabilizing soil carbon compounds in heavier, mineral-associated fractions (with multidecadal to century lifetimes). Despite these changes in the dynamics of different soil pools, we observed no significant changes in bulk soil carbon, highlighting a limitation inherent to the still widely used single-pool approach to investigating soil carbon responses to changing environmental conditions. It remains to be seen if the effects observed here-caused by relatively high, short-term fertilizer additions-are similar to those arising from lower, long-term additions of nitrogen to natural ecosystems from atmospheric deposition, but our results suggest nonetheless that current models of terrestrial carbon cycling do not contain the mechanisms needed to capture the complex relationship between nitrogen availability and soil carbon storage.

An antigenically related polypeptide family is a major structural constituent of a stable acrosomal matrix assembly in bovine spermatozoa

The apical and principal segments of the bovine acrosome contain a stable matrix complex that is bound to the outer acrosomal membrane and exhibits hydrolase-binding activity. The present study was undertaken to determine whether the outer acrosomal membrane-associated matrix complex (OMC) is composed of a unique set of acrosomal proteins and to define its fate during both capacitation and the acrosome reaction. A purified OMC fraction was isolated from ejaculated spermatozoa, and one polypeptide of 32 kDa (OMC32) was purified to homogeneity and used for N-terminal sequence analysis and preparation of monospecific antisera. Immunofluorescence staining of sperm with anti-OMC32 demonstrated that the polypeptide localized specifically to the apical and principal segments of the acrosome. Immunoelectron microscopy further revealed that OMC32 was restricted to the stable matrix assembly and was not associated with the inner acrosomal membrane or the equatorial segment. Immunoblot analyses of sperm lysates and of the purified OMC fraction revealed that anti-OMC32 recognized an antigenically related family of polypeptides between 38 and 19 kDa. These polypeptides exhibited no size processing during capacitation or the acrosome reaction, and they were not released during the acrosome reaction but remained in the particulate cell subfraction, associated with the hybrid membrane complex. N-terminal sequence analysis of OMC32 indicated a structural relationship to the SP-10 polypeptide family of human and baboon spermatozoa. The potential function of the OMC complex and differences in the intraacrosomal distribution of bovine OMC32-related polypeptides from that reported for acrosomal SP-10 polypeptides in other species are discussed.

Evaluation of a rapid peptide-based anti-human immunodeficiency virus-1 antibody immunoassay

A qualitative, visually interpreted, rapid, and synthetic peptide-based anti-human immunodeficiency virus-1 (HIV) antibody immunoassay has been developed that may be of value in situations in which rapid determination of HIV-1 status is important. Because questions have been raised about the accuracy of rapid anti-HIV-1 assays, the sensitivity, specificity, interobserver and intraobserver variability of the Genie HIV-1 assay (Genetics Systems, Seattle, WA) were determined. Sera from 56 patients with HIV-1 infections documented by enzyme immunoassay and western blot tested positive by this assay. Enzyme immunoassay- and western blot-negative sera from 30 visceral organ transplant donors were negative using the Genie assay. Specificity was examined further by testing sera from 29 patients hospitalized with a variety of medical disorders, including acute bacterial pneumonia, acute myocardial infarction, monoclonal gammopathy, and high titer antinuclear or antimitochondrial antibodies. Two of these patients were reactive with the enzyme immunoassay, both of which tested negative by western blot. All 29 tested negative using the Genie assay. In addition, sera from five patients with repeatedly reactive enzyme immunoassays and negative western blots tested negative by the Genie system. There was 100% agreement in interobserver and intraobserver studies. With the western blot as the reference method, the Genie assay exhibited 100% sensitivity and specificity and there was no observer variability.

Diagnostic significance of hypocomplementemia

Hypocomplementemia is an important marker for the presence of IC-mediated disease and can be used to assess disease activity. However, in interpreting the clinical significance of hypocomplementemia, the following must be kept in mind: 1) There are numerous non-immunologic conditions that also can cause hypocomplementemia. Furthermore, some of these conditions can cause a multisystem disease that, along with the hypocomplementemia, can closely resemble an IC-mediated systemic vasculitis. Furthermore, these nonimmunologic conditions that lower serum complement levels can complicate the course of patients with inactive IC-mediated disease, spuriously indicating that the disease is active. The most relevant of these differential diagnostic problems are listed in Table 2. 2) There are a few conditions (for example, pregnancy) that can raise serum complement levels, thereby possibly obscuring the presence of a disorder (such as, active SLE) that is lowering complement levels. 3) There are some conditions that might be expected to lower serum complement levels, because of their effect on protein metabolism, but do not. Nephrotic syndrome, and moderately poor nutrition are examples. All of these factors should be considered when interpreting results of serum complement levels in a given patient.

Immunosuppressive effects of pentostatin

The immune function of patients with hairy cell leukemia (HCL) and solid tumors was evaluated before and after treatment with the investigational drug 2'-deoxycoformycin (pentostatin; dCF). Thirteen HCL patients received doses of dCF of 2 to 4 mg/m2 intravenously at 2- to 6-week intervals for up to 15 courses. After completion of treatment, 12 of 13 patients had resolution of severe monocytopenia and five of nine had normal monocyte antibody dependent cellular cytotoxicity. There was statistically significant depression of total lymphocytes, T cells, and B cells. Evaluation of T subsets showed a decrease in CD4+ cells. Immunoglobulin G (IgG) in sera were decreased from baseline, while IgM and IgA were unaffected. There was no significant effect on skin-test reactivity or large granular lymphocyte numbers. Lymphoblastic transformation was variably affected. Natural-killer (NK) cell function was improved or unchanged after dCF treatment. Reevaluation of seven patients at 21 to 119 weeks after receiving dCF demonstrated that recovery to normal T- and B-cell numbers and subsets does occur. Five solid tumor patients were given dCF at 4 mg/m2 intravenously at 1- to 2-week intervals for up to five courses. There was significant reduction in T cells, B cells, CD4+, and CD8+ cells with no statistically significant effect on the other immune parameters. We conclude that low doses of dCF can cause persistent immunosuppression though recovery may occur after the drug is stopped. In patients followed after completion of dCF, there was no associated increase in second malignancies or unusual infections.

Sensitivity and interobserver variability of the Recombigen-HIV-1 LA test

The Recombigen-HIV-1 LA Test (Cambridge BioScience Corporation, Worcester, MA) uses recombinant peptides derived from the env gene product in a latex agglutination assay for the detection of antibodies to human immunodeficiency virus type 1 (HIV-1) and was recently approved by the Food and Drug Administration for marketing in the United States. It is intended for use as a screening test in physicians' offices, emergency rooms, and other settings where enzyme immunoassays are not practical or available. Concern has been raised over the sensitivity, specificity, and difficulty in interpretation of the agglutination pattern. The authors report on the sensitivity and interobserver variability of the assay as performed in a blinded fashion in a hospital laboratory by technologists experienced with other latex agglutination assays. In the first study, sera from 50 patients positive by enzyme immunoassay (EIA) (Abbott HIV EIA) and western blot (WB), performed with EPITOPE HIV western blot strips were assayed by one technologist using the latex agglutination technique. Forty-six samples were positive and four were negative, yielding a sensitivity of 92%. In the second study, 30 samples consisting of 10 negative by EIA and WB, 10 borderline by EIA and/or indeterminate by WB, and 10 positive by EIA and WB were evaluated by three technologists with the latex agglutination technique. There was agreement among all three technologists in 24 of 30 samples (80%). There was disagreement over one sample from the negative group (one technologist obtained a single false positive result), three from the borderline/indeterminate group, and two from the positive group (three technologists obtained false negative results on two samples). In summary, the authors report interobserver variation in interpreting 20% of tests, reflecting difficulty in assessing weak agglutination. Sensitivity of 92% is below that achievable with the EIA or WB techniques and limits the usefulness of the latex agglutination assay as a screening test.

Relative value of prostate-specific antigen and prostatic acid phosphatase in diagnosis and management of adenocarcinoma of prostate. Ohio State University experience

Serum concentrations of prostate-specific antigen (PSA), prostate-specific acid phosphatase (PAP), and transrectal prostatic ultrasound were utilized in the evaluation of 193 men with various urologic disorders. Of the 193 patients, 48 had prostate cancer, and the other 145 included 5 with genitourinary neoplasms, 69 with benign prostatic hypertrophy, and 71 with other non-neoplastic genitourinary disease. PSA levels were elevated in 35 patients with prostate cancer and in 25 of the 145 without prostate cancer. PAP levels were elevated in 15 with prostate cancer and in 2 of the 145 without prostate cancer. The data indicate that PSA is a more sensitive but less specific tumor marker than PAP in the detection of prostate cancer. PSA appears to be more sensitive than PAP in monitoring the response to treatment. The use of PSA and PAP jointly to detect and to monitor prostate cancer did not appear to enhance the clinical utility over that of PSA alone.

Infectious hazards in the clinical laboratory: a program to protect laboratory personnel

The increasing risk of exposure to blood-borne pathogens in the health care setting makes the development of effective infection control programs in the laboratory workplace critical. Central to such programs is the concept of universal precautions. The program described here relates the level of protection or precaution to the potential danger for infection, given the laboratory workstation and task which is to be performed. Four Levels of Protection are described. Implementation of this program requires that each workstation and procedure in each laboratory section be reviewed by the laboratory director and supervisory personnel for risk of exposure. Implementation additionally requires that provisions be made for both the initial and continuing education of laboratory employees. Laboratory directors and supervisors should also monitor the program to ensure compliance. There will certainly be situations unique to individual institutions or laboratory settings that may require precautions or policies over and above those described by universal precautions. Laboratory policies will not gain acceptance if they are developed and implemented without the advice and cooperation of the hospital medical staff. Employee acceptance of infection control policies will be greater if actual development and implementation actively involves the laboratory personnel who will practice them. The program described here is but one approach to the problem. Employers and laboratory directors must understand that it is their responsibility to develop a program that provides appropriate safeguards for workers who may be exposed to infectious agents in the laboratory workplace and to ensure that employees are properly trained and educated in the proper use and application of those safeguards.

Bullous lichen planus: diagnosis by indirect immunofluorescence and treatment with dapsone

Bullous lichen planus may be confused with other subepidermal bullous dermatoses, especially if bullae arise on normal-appearing skin. We present two patients who were originally thought, on the basis of clinical and histopathologic criteria, to have bullous pemphigoid. However, results of standard indirect and direct immunofluorescence assays did not support the diagnosis of bullous pemphigoid. Further investigation using the indirect autologous immunofluorescence assay revealed deposits of immunoglobulins in the stratum granulosum. Moreover, the indirect allogeneic immunofluorescence assay (using papular lichen planus lesional substrates from different patients) was positive for the same pattern, confirming the diagnosis of bullous lichen planus. Bullous lichen planus with bullous pemphigoid-like histologic features can be differentiated from bullous pemphigoid on the basis of the indirect autologous and allogeneic immunofluorescence assays for circulating antigranulosum antibodies. Both patients were treated with systemic corticosteroids. One patient went into remission with this therapy alone; the other patient had a favorable response when dapsone was given with systemic corticosteroids. The suggestion that there is a subset of bullous lichen planus with bullous pemphigoid-like histologic features that responds to dapsone needs to be explored.

Gastrointestinal malformations associated with prune belly syndrome: three cases and a review of the literature

Prune belly syndrome (PBS), a triad consisting of abdominal musculature hypoplasia, urinary tract malformations, and cryptorchidism, is frequently associated with other congenital malformations. Although it is acknowledged that gastrointestinal (GI) malrotation and mesenteric anomalies are frequent in PBS, other GI anomalies are generally considered to be exceedingly rare. Here we describe 3 autopsy cases with severe malformations of both midgut and hindgut derivatives and review the world literature to evaluate the spectrum of GI malformations associated with this syndrome. The relatively high frequency of distal stenoses and atresias suggests that the anomalous mesenteric attachments may predispose to prenatal volvulus and subsequent anatomic bowel obstruction. Postnatal volvulus is also occasionally observed. Infants with PBS also appear to be at a higher risk for persistence of the common fetal cloaca.

Use of indirect immunofluorescence in the lupus erythematosus/lichen planus overlap syndrome: an additional diagnostic clue

The lupus erythematosus (LE)/lichen planus (LP) overlap syndrome comprises a heterogeneous group of patients who demonstrate clinical, histologic, and immunopathologic characteristics of two diseases. We report six patients with the syndrome who were evaluated by a double-layer indirect immunofluorescence (IF) technic using patient serum and autologous lesional skin as substrate followed by conjugate. This test demonstrated intense staining of the stratum granulosum in two patients, a finding previously shown to be consistent with LP. A third patient developed criteria for the diagnosis of systemic LE with corroborating direct IF findings and a negative indirect IF assay. This preliminary study provides evidence for a possible way of distinguishing LE from LP in some patients with the overlap syndrome.

Hematological Characteristics of the BB Wistar Rat

Complete blood counts, differential white blood cell and platelet counts were performed on male and female BB Wistar diabetic rats (BBWd), their nondiabetic siblings (BBWnd) and outbred Wistar rats of the line from which the BB Wistar rats were derived. Most of the observed changes were strain-related (those present in both BBWd and BBWnd but not in control rats) rather than diabetes-related (those in BBWd but neither BBWnd nor control rats) and therefore probably due to the inbreeding process. The BBW strain had significantly lower numbers of white cells and platelets, as well as markedly changed differential white cell counts. Differential counts showed a pattern of lymphopenia, neutrophilia, monocytosis and eosinophilia. It is possible that these white blood cell changes contribute to the increased susceptibility to infection reported for the BBW strain. No significant difference in serum immunoglobulin concentrations was found in any of these three groups of rats. There- fore, hypogammaglobutinemia cannot account for the increased susceptibility to infections, but it is not possible to rule out an abnormality in the distribution of immunoglobulin fractions as an etiological factor.

Increased helper-suppressor T-cell ratio in psoriasis

Numerous investigations have suggested an immunologic pathogenesis of psoriasis and diminished suppressor T-cell activity of psoriatic blood. Consequently, a study was undertaken to explain whether diminished suppressor cell activity was a result of quantitative alterations of the T-lymphocyte subpopulation. Twenty patients with psoriasis and 20 normal control subjects were randomly selected. Our findings demonstrated a significant decrease in the percentage of suppressor cells (T gamma), a significant elevation of helper cells (T mu), and a highly significant increase in the helper-suppressor T-cell ratio (T mu/T gamma) of psoriatic blood compared with that of normal control subjects. Our study gives further support to the possible role of immunologic factors in the pathogenesis of psoriasis.