Real-world persistence with dolutegravir/lamivudine versus bictegravir/emtricitabina/tenofovir-alafenamide among people with HIV. / Persistencia de los tratamientos con dolutegravir/lamivudina y bictegravir/emtricitabina/tenofovir-alafenamida en personas con VIH en la práctica real.

OBJETIVES: The main objective was to compare the persistence between dolutegravir/lamivudine (DTG/3TC) and bictegravir/emtricitabine/tenofovir-alafenamide (BIC/FTC/TAF) and to analyze reasons for discontinuation. METHODS: We conducted a retrospective, non-interventional, descriptive and longitudinal study. All human immunodeficiency virus (HIV) patients over 18 years treated with DTG/3TC or BIC/FTC/TAF in our center were included. Persistence after first year was compared using the χ2 test. Kaplan-Meier survival analysis was performed. RESULTS: Three hundred fifty-eight patients were included. 99.5% versus 90.99% of patients were persistent after the first year for DTG/3TC and BIC/FTC/TAF respectively (p = 0.001). Persistence with DGT/3TC was 1,237 days (IC95% 1,216-1,258) and persistence with BIC/FTC/TAF was 986 days ([IC95% 950-1,021]; p < 0.001). The difference was remained after adjusting for covariates with the cox regression model (HR= 8.2 [IC95% 1.03-64.9], p = 0.047). The main reasons for discontinuation for BIC/FTC/TAF were toxicity/tolerability. CONCLUSION: In our study patients had a high persistence. Patients on DTG/3TC treatment were more persistent compared to BIC/FTC/TAF, although BIC/FTC/TAF have worse baseline characteristics. The main reason for discontinuation of BIC/FTC/TAF was tolerability/toxicity.

Tropical tree ectomycorrhiza are distributed independently of soil nutrients.

Mycorrhizae, a form of plant-fungal symbioses, mediate vegetation impacts on ecosystem functioning. Climatic effects on decomposition and soil quality are suggested to drive mycorrhizal distributions, with arbuscular mycorrhizal plants prevailing in low-latitude/high-soil-quality areas and ectomycorrhizal (EcM) plants in high-latitude/low-soil-quality areas. However, these generalizations, based on coarse-resolution data, obscure finer-scale variations and result in high uncertainties in the predicted distributions of mycorrhizal types and their drivers. Using data from 31 lowland tropical forests, both at a coarse scale (mean-plot-level data) and fine scale (20 × 20 metres from a subset of 16 sites), we demonstrate that the distribution and abundance of EcM-associated trees are independent of soil quality. Resource exchange differences among mycorrhizal partners, stemming from diverse evolutionary origins of mycorrhizal fungi, may decouple soil fertility from the advantage provided by mycorrhizal associations. Additionally, distinct historical biogeographies and diversification patterns have led to differences in forest composition and nutrient-acquisition strategies across three major tropical regions. Notably, Africa and Asia's lowland tropical forests have abundant EcM trees, whereas they are relatively scarce in lowland neotropical forests. A greater understanding of the functional biology of mycorrhizal symbiosis is required, especially in the lowland tropics, to overcome biases from assuming similarity to temperate and boreal regions.

Consistent patterns of common species across tropical tree communities.

Trees structure the Earth's most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1-6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth's 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world's most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.

The monarch butterfly in Mexico: a conservation model.

Each fall, millions of monarch butterflies (Danaus plexippus L.) travel from Canada and the United States to overwinter in Mexico and California. In 2022, the IUCN listed migratory monarchs as endangered because of their population decline. The main accepted drivers are widespread use of herbicides, effects of climate, and land use change that causes habitat loss. We analyzed the main actions taken to officially protect the overwintering sites and the migration phenomenon with the establishment of the Monarch Butterfly Biosphere Reserve in 2000. The conservation of the monarch overwintering sites in Mexico is an example of continuous work from their discovery to the present. We highlight the importance of monitoring the areas covered by overwintering monarchs in Mexico. These colonies represent the largest concentrations of monarch populations in the world. In the last 10 years, the average area covered by monarchs was 2.72 ( ± 0.47 SE) hectares.

Mycorrhizal feedbacks influence global forest structure and diversity.

One mechanism proposed to explain high species diversity in tropical systems is strong negative conspecific density dependence (CDD), which reduces recruitment of juveniles in proximity to conspecific adult plants. Although evidence shows that plant-specific soil pathogens can drive negative CDD, trees also form key mutualisms with mycorrhizal fungi, which may counteract these effects. Across 43 large-scale forest plots worldwide, we tested whether ectomycorrhizal tree species exhibit weaker negative CDD than arbuscular mycorrhizal tree species. We further tested for conmycorrhizal density dependence (CMDD) to test for benefit from shared mutualists. We found that the strength of CDD varies systematically with mycorrhizal type, with ectomycorrhizal tree species exhibiting higher sapling densities with increasing adult densities than arbuscular mycorrhizal tree species. Moreover, we found evidence of positive CMDD for tree species of both mycorrhizal types. Collectively, these findings indicate that mycorrhizal interactions likely play a foundational role in global forest diversity patterns and structure.

Assessing the ecological quality status of macrobenthic communities in a marine terminal of liquefied natural gas in Peru.

Macrobenthic organisms are useful bioindicators to assess ecological quality status. On the south-central coast of Peru (13°15.15'S, 76°18.5'W), a Liquefied Natural Gas (LNG) marine terminal has been operating since 2010. We investigated the macrobenthic communities and sediment parameters from 2011 to 2020 to evaluate the ecological quality status in the surrounding area of the marine terminal, using the AZTI Marine Biotic Index (AMBI) and its multivariate version (M-AMBI). We analyzed the diversity and community composition of macrobenthic invertebrates and the physico-chemical parameters of the sediment from 29 sampling sites, ranging from 0 to 15m depth. The sampling design considered: the direct influence zone ("DIZ", surroundings of the marine terminal), and northern (NCZ) and southern (SCZ) control zones. Our results indicated that abundance was high at SCZ and decreased with depth. Species richness and diversity were high at DIZ and NCZ, respectively, and increased up to 10m but dropped at 15m. High sand content was recorded in shallow depths, while in deeper areas and DIZ, mud and organic matter increased and redox potential was negative. AMBI indicated a "slightly disturbed" status in general, while M-AMBI indicated "good" or "moderate" status at depths ≤ 12m, and "poor" status at 15m. Overall, the season/year factor was not important, and variables were mostly significantly different across depths. Redox potential and organic matter were correlated with M-AMBI at 15m. In general, our results indicate an acceptable ecological quality surrounding the marine terminal, likely because the study area is not influenced by an important input of an anthropogenic stressor. This study highlights the importance of monitoring benthic communities in the surroundings of human-made structures and the use of ecological quality indices for understanding potential impacts.

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity.

A map of African humid tropical forest aboveground biomass derived from management inventories.

Forest biomass is key in Earth carbon cycle and climate system, and thus under intense scrutiny in the context of international climate change mitigation initiatives (e.g. REDD+). In tropical forests, the spatial distribution of aboveground biomass (AGB) remains, however, highly uncertain. There is increasing recognition that progress is strongly limited by the lack of field observations over large and remote areas. Here, we introduce the Congo basin Forests AGB (CoFor-AGB) dataset that contains AGB estimations and associated uncertainty for 59,857 1-km pixels aggregated from nearly 100,000 ha of in situ forest management inventories for the 2000 - early 2010s period in five central African countries. A comprehensive error propagation scheme suggests that the uncertainty on AGB estimations derived from c. 0.5-ha inventory plots (8.6-15.0%) is only moderately higher than the error obtained from scientific sampling plots (8.3%). CoFor-AGB provides the first large scale view of forest AGB spatial variation from field data in central Africa, the second largest continuous tropical forest domain of the world.

Soil nitrogen concentration mediates the relationship between leguminous trees and neighbor diversity in tropical forests.

Legumes provide an essential service to ecosystems by capturing nitrogen from the atmosphere and delivering it to the soil, where it may then be available to other plants. However, this facilitation by legumes has not been widely studied in global tropical forests. Demographic data from 11 large forest plots (16-60 ha) ranging from 5.25° S to 29.25° N latitude show that within forests, leguminous trees have a larger effect on neighbor diversity than non-legumes. Where soil nitrogen is high, most legume species have higher neighbor diversity than non-legumes. Where soil nitrogen is low, most legumes have lower neighbor diversity than non-legumes. No facilitation effect on neighbor basal area was observed in either high or low soil N conditions. The legume-soil nitrogen positive feedback that promotes tree diversity has both theoretical implications for understanding species coexistence in diverse forests, and practical implications for the utilization of legumes in forest restoration.

Abundance, density, and social structure of African forest elephants (Loxodonta cyclotis) in a human-modified landscape in southwestern Gabon.

Population monitoring is critical to effective conservation, but forest living taxa can be difficult to directly observe. This has been true of African forest elephants (Loxodonta cyclotis), for which we have limited information regarding population size and social behavior despite their threatened conservation status. In this study, we estimated demographic parameters using genetic capture-recapture of forest elephants in the southern Industrial Corridor of the Gamba Complex of Protected Areas in southwestern Gabon, which is considered a global stronghold for forest elephants. Additionally, we examined social networks, predicting that we would find matrilineal structure seen in both savanna and forest elephants. Given 95% confidence intervals, we estimate population size in the sampled area to be between 754 and 1,502 individuals and our best density estimate ranges from 0.47 to 0.80 elephants per km2. When extrapolated across the entire Industrial Corridor, this estimate suggests an elephant population size of 3,033 to 6,043 based on abundance or 1,684 to 2,832 based on density, approximately 40-80% smaller than previously suggested. Our social network analysis revealed approximately half of network components included females with different mitochondrial haplotypes suggesting a wider range of variation in forest elephant sociality than previously thought. This study emphasizes the threatened status of forest elephants and demonstrates the need to further refine baseline estimates of population size and knowledge on social behavior in this taxon, both of which will aid in determining how population dynamics in this keystone species may be changing through time in relation to increasing conservation threats.

Frailty as a predictor of short- and long-term mortality in critically ill older medical patients.

PURPOSE: Frailty is a common condition among critically ill patients. Usually evaluated in a mixed population of medical, cardiac and surgical patients, we aimed to assess the impact of frailty on short- and long-term mortality exclusively in critically ill older medical patients. MATERIALS AND METHODS: We included 285 patients aged≥70 years admitted to ICU (2009-2017). Comorbidities, severity scores, treatment intensity and complications were recorded. Pre-hospital frailty, measured by Clinical Frailty Scale (CFS), was defined as a score ≥ 5 according to this scale. RESULTS: Prevalence of frailty (CFS ≥ 5) of 18.6%. Frail patients were more likely to be female (64.2% vs. 35.6%, p < .001) or suffer from heart failure (17% vs. 6%,p = .021). Apache II score was higher in frail than in non-frail patients (27.4 ±â€¯7.1 vs. 24.8 ±â€¯8.6,p = .041). Age, comorbidities, treatment intensity, complications, and ICU and hospital length of stay were similar between frail and non-frail patients. Life-sustaining treatment limitation was more frequent in frail patients (47.2% vs. 20.7%,p < .001). Except for ICU mortality, frailty was an independent predictor of short- and long-term mortality after adjustment for sociodemographic, comorbidities, severity scores, treatment intensity and complications. CONCLUSIONS: Frailty (CFS ≥ 5) was independently associated with short- and long-term mortality in older patients admitted to ICU exclusively due to a medical reason.

The Forest Observation System, building a global reference dataset for remote sensing of forest biomass.

Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world's forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities.

Direct and indirect effects of climate on richness drive the latitudinal diversity gradient in forest trees.

Climate is widely recognised as an important determinant of the latitudinal diversity gradient. However, most existing studies make no distinction between direct and indirect effects of climate, which substantially hinders our understanding of how climate constrains biodiversity globally. Using data from 35 large forest plots, we test hypothesised relationships amongst climate, topography, forest structural attributes (stem abundance, tree size variation and stand basal area) and tree species richness to better understand drivers of latitudinal tree diversity patterns. Climate influences tree richness both directly, with more species in warm, moist, aseasonal climates and indirectly, with more species at higher stem abundance. These results imply direct limitation of species diversity by climatic stress and more rapid (co-)evolution and narrower niche partitioning in warm climates. They also support the idea that increased numbers of individuals associated with high primary productivity are partitioned to support a greater number of species.

Empirical selection between least-cost and current-flow designs for establishing wildlife corridors in Gabon.

Corridors are intended to increase species survival by abating landscape fragmentation resulting from the conversion of natural habitats into human-dominated matrices. Conservation scientists often rely on 1 type of corridor model, typically the least-cost model or current-flow model, to construct a linkage design, and their choice is not usually based on theory or empirical evidence. We developed a method to empirically confirm whether corridors produced by these 2 models are used by target species under current landscape conditions. We applied this method in the Gamba landscape between 2 national parks in southwestern Gabon. We collected signs of presence of African forest elephant (Loxodonta cyclotis), forest buffalo (Syncerus caffer nanus), and 2 apes, western lowland gorilla (Gorilla gorilla gorilla) and central chimpanzee (Pan troglodytes troglodytes), on transects. We used patch-occupancy models to identify least-cost and current-flow corridors for these 4 species. On average, 28.7% of current-flow corridors overlapped with least-cost corridors, confirming that the choice of corridor model can affect the location of the resulting linkage design. We validated these corridors by monitoring signs and examining camera detections on new transects within and outside modeled corridors. Current-flow corridors performed better than least-cost corridors for elephants, whereas the opposite was found for buffalo and apes. Locations of the highest priority corridors for the 3 taxa did not overlap, and only 18.3% of their combined surface was common among 2 species. We used centrality metrics to calculate the average contribution of corridor pixels to landscape connectivity and derived an index that can be used to prioritize corridors. As a result, we recommend protecting at least 17.4% of the land surface area around Gamba town to preserve the preferred travel routes of the target species.

Selección Empírica entre Diseños de Menor Costo y de Flujo de Corriente para Establecer Corredores de Fauna en Gabón Resumen La intención de los corredores es incrementar la supervivencia de las especies abatiendo la fragmentación del paisaje que resulta de la conversión de los hábitats naturales en matrices dominadas por humanos. Los científicos de la conservación con frecuencia dependen de un tipo de modelo de corredor, comúnmente el modelo de menor costo o el de flujo de corriente para construir un diseño de conexiones y su elección no suele estar basada en evidencia teórica o empírica. Desarrollamos un método para confirmar empíricamente si los corredores producidos por estos dos modelos son usados por las especies diana bajo las condiciones actuales del paisaje. Aplicamos este método en el paisaje de Gamba entre dos parques nacionales al suroeste de Gabón. Recolectamos señales de la presencia del elefante de bosque africano (Loxodonta cyclotis), el búfalo de bosque (Syncerus caffer nanus), y dos primates: el gorila occidental de tierras bajas (Gorilla gorilla gorilla) y el chimpancé central (Pan troglodytes troglodytes) a lo largo de transectos en esta zona. Usamos modelos de ocupación de fragmentos para identificar los corredores de menor costo y los de flujo de corriente para estas cuatro especies. En promedio, el 28.7% de los corredores de flujo de corriente se traslaparon con los corredores de menor costo, lo que confirmó que la elección de modelo de corredor puede afectar la ubicación del diseño de conexiones resultante. Validamos estos corredores por medio del monitoreo de señales y la examinación de detecciones con cámaras en transectos nuevos dentro y fuera de los corredores modelados. Los corredores de flujo de corriente tuvieron un mejor desempeño que los corredores de menor costo para los elefantes, mientras que fue el caso contrario para los búfalos y los primates. La ubicación de los corredores con mayor prioridad para los tres taxones no se traslapó y sólo el 18.3% de las superficies combinadas fue común para dos especies. Usamos medidas de centralidad para calcular la contribución promedio de los pixeles del corredor hacia la conectividad del paisaje y derivamos un índice que puede usarse para priorizar los corredores. Como resultado de nuestro estudio recomendamos proteger al menos el 17.4% del área de superficie terrestre alrededor del poblado de Gamba para preservar las rutas de viaje de las especies diana.

Substrate, moisture, temperature and seed germination of the threatened endemic tree Eriotheca vargasii (Malvaceae) / Sustrato, humedad, temperatura y germinación de semillas del árbol endémico amenazado Eriotheca vargasii (Malvaceae)

Abstract We studied the germination of Eriotheca vargasii (Malvaceae), a poorly known endemic Peruvian Andean tree species characteristic of the dry forests of the Torobamba river valley, Peru. We determined seed characteristics, embryo morphology, viability, and assessed the influence of substrate (natural soil and commercially prepared media), temperature (controlled at 25 ºC and at ambient temperature between 18-22 ºC), and moisture (25 % and 50 % field capacity) on seed germination. Most seeds were ovoid in shape and although they contained well-developed embryos, only 46 % of them were viable. Substrate moisture levels had no influence on germination capacity or rate. In contrast, temperature and substrate type showed strong effects on germination. We observed the highest proportion of germinated seeds in prepared media at both temperatures tested (> 61 %). Furthermore, substrate types also influenced germination rates, with lower values in natural soil. The strongest effect on germination rates was by temperature, enhancing the difference in responses in substrate types (up to 90 % in commercially prepared media at 25 ºC). The low proportion of germinated seeds in soil (< 39 %), together with external local stress factors (e.g. grazing impact by herbivores), may be the critical factors contributing to the nearly total absence of seedlings and saplings of E. vargasiiin the study area despite abundant seed production. In order to ensure a supply of E. vargasii seedlings for reforestation efforts, we recommend producing E. vargasii plants in nurseries and conducting reforestation trials. We suggest that germination of seedlings is done following guidelines from this study. Rev. Biol. Trop. 66(3): 1162-1170. Epub 2018 September 01.

Resumen Estudiamos la germinación de Eriotheca vargasii (Malvaceae), un árbol endémico poco conocido de los andes peruanos y carácterístico de los bosques secos del valle del río Torobamba. Determinamos las características de la semilla, la morfología del embrión y la viabilidad; además evaluamos la influencia del sustrato (suelo y sustrato preparado comercialmente), temperatura (controlada a 25 ºC y sin control entre 18-22 ºC) y humedad (25 % y 50 % de capacidad de campo) sobre la germinación de las semillas. La mayoría de las semillas tuvo forma ovoide y aunque la mayoría contenía embriones bien desarrollados, sólo el 46 % de estas fue viable. Los niveles de humedad del sustrato no tuvieron influencia sobre la capacidad o tasa de germinación, mientras que la temperatura y el tipo de sustrato si tuvieron efectos visibles. Observamos las proporciones más altas de semillas germinadas en los sustratos preparados y en ambas temperaturas (> 61 %). Adicionalmente, el tipo de sustrato también influenció las tasas de germinación, con valores más bajos en el suelo natural. El efecto más fuerte sobre las tasas de germinación se dió por la temperatura, aumentando las diferencias de las respuestas de acuerdo al tipo de sustrato (hasta un 90 % de germinación en sustratos preparados comercialmente y a 25 ºC). La baja proporción de semillas germinadas en el suelo (< 39 %), junto con factores locales de estrés externos (como por ejemplo el impacto por herbivoría), pueden ser elementos clave que están contribuyendo a la casi ausencia total de plántulas de E. vargasii en el área de estudio, a pesar de una producción de semilla abundante. Para asegurar proveer plantones de E. Vargasii para esfuerzos de reforestación, recomendamos producir plantas de esta especie en viveros y realizar experimentos de reforestación. Sugerimos que la germinación de las plántulas se haga siguiendo las recomendaciones de este estudio.

Response to Comment on "Plant diversity increases with the strength of negative density dependence at the global scale".

Hülsmann and Hartig suggest that ecological mechanisms other than specialized natural enemies or intraspecific competition contribute to our estimates of conspecific negative density dependence (CNDD). To address their concern, we show that our results are not the result of a methodological artifact and present a null-model analysis that demonstrates that our original findings-(i) stronger CNDD at tropical relative to temperate latitudes and (ii) a latitudinal shift in the relationship between CNDD and species abundance-persist even after controlling for other processes that might influence spatial relationships between adults and recruits.

Response to Comment on "Plant diversity increases with the strength of negative density dependence at the global scale".

Chisholm and Fung claim that our method of estimating conspecific negative density dependence (CNDD) in recruitment is systematically biased, and present an alternative method that shows no latitudinal pattern in CNDD. We demonstrate that their approach produces strongly biased estimates of CNDD, explaining why they do not detect a latitudinal pattern. We also address their methodological concerns using an alternative distance-weighted approach, which supports our original findings of a latitudinal gradient in CNDD and a latitudinal shift in the relationship between CNDD and species abundance.

Why do microbes exhibit weak biogeographic patterns?

Analysis of patterns in the distribution of taxa can provide important insights into ecological and evolutionary processes. Microbial biogeographic patterns almost always appear to be weaker than those reported for plant and animal taxa. It is as yet unclear why this is the case. Some argue that microbial diversity scales differently over space because microbial taxa are fundamentally different in their abundance, longevity and dispersal abilities. Others have argued that differences in scaling are an artifact of how we assess microbial biogeography, driven, for example, by differences in taxonomic resolution, spatial scale, sampling effort or community activity/dormancy. We tested these alternative explanations by comparing bacterial biogeographic patterns in soil to those of trees found in a forest in Gabon. Altering taxonomic resolution, excluding inactive individuals, or adjusting for differences in spatial scale were insufficient to change the rate of microbial taxonomic turnover. In contrast, we account for the differences in spatial turnover between these groups by equalizing sampling extent. Our results suggest that spatial scaling differences between microbial and plant diversity are likely not due to fundamental differences in biology, and that sampling extent should be taken into account when comparing the biogeographic patterns of microorganisms and larger organisms.

Necrolisis epidérmica tóxica: un paradigma de enfermedad crítica / Toxic epidermal necrolysis: a paradigm of critical illness

RESUMEN La necrolisis epidérmica tóxica es una reacción cutánea adversa de tipo inmunológico secundaria en la mayor parte de los casos a la administración de un fármaco. La necrolisis epidérmica tóxica, el síndrome de Steven Johnson y el eritema exudativo multiforme forman parte del mismo espectro de enfermedad. La mortalidad de la necrolisis epidérmica tóxica es alrededor del 30%. La fisiopatología de la necrolisis epidérmica tóxica es semejante en muchos aspectos a la de las quemaduras dérmicas superficiales. La afectación mucosa del epitelio ocular y genital se asocia con secuelas graves si no se trata de forma temprana. Se acepta en general que los pacientes con necrolisis epidérmica tóxica son tratados mejor en unidades de grandes quemados, donde existe experiencia en el manejo de enfermos con pérdida cutánea extensa. El tratamiento es de soporte, eliminación y cobertura con derivados biosintéticos de la piel de las zonas afectadas, tratamiento de la afectación mucosa, y tratamiento inmunosupresor específico. De los tratamientos ensayados sólo se usa actualmente en la mayor parte de los centros la inmunoglobulina G y la ciclosporina A, aun cuando no existe evidencia sólida para recomendar ningún tratamiento específico. Entre los aspectos particulares del tratamiento de esta enfermedad se encuentra la prevención de secuelas relacionadas con la formación de sinequias, los cuidados oculares para prevenir secuelas graves que pueden conducir a la ceguera, y el tratamiento específico inmunosupresor. Un mejor conocimiento de los principios del manejo de la necrolisis epidérmica tóxica llevará a un mejor manejo de la enfermedad, a una mayor supervivencia y una menor prevalencia de las secuelas.

ABSTRACT Toxic epidermal necrolysis is an adverse immunological skin reaction secondary in most cases to the administration of a drug. Toxic epidermal necrolysis, Stevens-Johnson syndrome, and multiform exudative erythema are part of the same disease spectrum. The mortality rate from toxic epidermal necrolysis is approximately 30%. The pathophysiology of toxic epidermal necrolysis is similar in many respects to that of superficial skin burns. Mucosal involvement of the ocular and genital epithelium is associated with serious sequelae if the condition is not treated early. It is generally accepted that patients with toxic epidermal necrolysis are better treated in burn units, which are experienced in the management of patients with extensive skin loss. Treatment includes support, elimination, and coverage with biosynthetic derivatives of the skin in affected areas, treatment of mucosal involvement, and specific immunosuppressive treatment. Of the treatments tested, only immunoglobulin G and cyclosporin A are currently used in most centers, even though there is no solid evidence to recommend any specific treatment. The particular aspects of the treatment of this disease include the prevention of sequelae related to the formation of synechiae, eye care to prevent serious sequelae that can lead to blindness, and specific immunosuppressive treatment. Better knowledge of the management principles of toxic epidermal necrolysis will lead to better disease management, higher survival rates, and lower prevalence of sequelae.

Plant diversity increases with the strength of negative density dependence at the global scale.

Theory predicts that higher biodiversity in the tropics is maintained by specialized interactions among plants and their natural enemies that result in conspecific negative density dependence (CNDD). By using more than 3000 species and nearly 2.4 million trees across 24 forest plots worldwide, we show that global patterns in tree species diversity reflect not only stronger CNDD at tropical versus temperate latitudes but also a latitudinal shift in the relationship between CNDD and species abundance. CNDD was stronger for rare species at tropical versus temperate latitudes, potentially causing the persistence of greater numbers of rare species in the tropics. Our study reveals fundamental differences in the nature of local-scale biotic interactions that contribute to the maintenance of species diversity across temperate and tropical communities.