Variable thermal plasticity of leaf functional traits in Andean tropical montane forests.

Tropical montane forests (TMFs) are biodiversity hotspots and provide vital ecosystem services, but they are disproportionately vulnerable to climate warming. In the Andes, cold-affiliated species from high elevations are being displaced at the hot end of their thermal distributions by warm-affiliated species migrating upwards from lower elevations, leading to compositional shifts. Leaf functional traits are strong indicators of plant performance and at the community level have been shown to vary along elevation gradients, reflecting plant adaptations to different environmental niches. However, the plastic response of such traits to relatively rapid temperature change in Andean TMF species remains unknown. We used three common garden plantations within a thermosequence in the Colombian Andes to investigate the warming and cooling responses of key leaf functional traits in eight cold- and warm-affiliated species with variable thermal niches. Cold-affiliated species shifted their foliar nutrient concentrations when exposed to warming, while all other traits did not significantly change; contrastingly, warm-affiliated species were able to adjust structural, nutrient and water-use efficiency traits from acquisitive to conservative strategies in response to cooling. Our findings suggest that cold-affiliated species will struggle to acclimate functional traits to warming, conferring warm-affiliated species a competitive advantage under climate change.

Biological invasions and climate change amplify each other's effects on dryland degradation.

Climate models predict that, in the coming decades, many arid regions will experience increasingly hot conditions and will be affected more frequently by drought. These regions are also experiencing rapid vegetation change, notably invasion by exotic grasses. Invasive grasses spread rapidly into native desert ecosystems due, in particular, to interannual variability in precipitation and periodic fires. The resultant destruction of non-fire-adapted native shrub and grass communities and of the inherent soil resource heterogeneity can yield invader-dominated grasslands. Moreover, recurrent droughts are expected to cause widespread physiological stress and mortality of both invasive and native plants, as well as the loss of soil resources. However, the magnitude of these effects may differ between invasive and native grasses, especially under warmer conditions, rendering the trajectory of vegetated communities uncertain. Using the Biosphere 2 facility in the Sonoran Desert, we evaluated the viability of these hypothesized relationships by simulating combinations of drought and elevated temperature (+5°C) and assessing the ecophysiological and mortality responses of both a dominant invasive grass (Pennisetum ciliare or buffelgrass) and a dominant native grass (Heteropogan contortus or tanglehead). While both grasses survived protracted drought at ambient temperatures by inducing dormancy, drought under warmed conditions exceeded the tolerance limits of the native species, resulting in greater and more rapid mortality than exhibited by the invasive. Thus, two major drivers of global environmental change, biological invasion and climate change, can be expected to synergistically accelerate ecosystem degradation unless large-scale interventions are enacted.

Targeting Nanomaterials to Head and Neck Cancer Cells Using a Fragment of the Shiga Toxin as a Potent Natural Ligand.

Head and Neck Cancer (HNC) is the seventh most common cancer worldwide with a 5-year survival from diagnosis of 50%. Currently, HNC is diagnosed by a physical examination followed by an histological biopsy, with surgery being the primary treatment. Here, we propose the use of targeted nanotechnology in support of existing diagnostic and therapeutic tools to prevent recurrences of tumors with poorly defined or surgically inaccessible margins. We have designed an innocuous ligand-protein, based on the receptor-binding domain of the Shiga toxin (ShTxB), that specifically drives nanoparticles to HNC cells bearing the globotriaosylceramide receptor on their surfaces. Microscopy images show how, upon binding to the receptor, the ShTxB-coated nanoparticles cause the clustering of the globotriaosylceramide receptors, the protrusion of filopodia, and rippling of the membrane, ultimately allowing the penetration of the ShTxB nanoparticles directly into the cell cytoplasm, thus triggering a biomimetic cellular response indistinguishable from that triggered by the full-length Shiga toxin. This functionalization strategy is a clear example of how some toxin fragments can be used as natural biosensors for the detection of some localized cancers and to target nanomedicines to HNC lesions.

Multiwalled Carbon Nanotubes Inhibit Tumor Progression in a Mouse Model.

Understanding the molecular mechanisms underlying the biosynthetic interactions between particular nanomaterials with specific cells or proteins opens new alternatives in nanomedicine and nanotoxicology. Multiwalled carbon nanotubes (MWCNTs) have long been explored as drug delivery systems and nanomedicines against cancer. There are high expectations for their use in therapy and diagnosis. These filaments can translocate inside cultured cells and intermingle with the protein nanofilaments of the cytoskeleton, interfering with the biomechanics of cell division mimicking the effect of traditional microtubule-binding anti-cancer drugs such as paclitaxel. Here, it is shown how MWCNTs can trigger significant anti-tumoral effects in vivo, in solid malignant melanomas produced by allograft transplantation. Interestingly, the MWCNT anti-tumoral effects are maintained even in solid melanomas generated from paclitaxel-resistant cells. These findings provide great expectation in the development of groundbreaking adjuvant synthetic microtubule-stabilizing chemotherapies to overcome drug resistance in cancer.

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses.

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates of deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. Our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.

Nano-ZnO leads to tubulin macrotube assembly and actin bundling, triggering cytoskeletal catastrophe and cell necrosis.

Zinc is a crucial element in biology that plays chief catalytic, structural and protein regulatory roles. Excess cytoplasmic zinc is toxic to cells so there are cell-entry and intracellular buffering mechanisms that control intracellular zinc availability. Tubulin and actin are two zinc-scavenging proteins that are essential components of the cellular cytoskeleton implicated in cell division, migration and cellular architecture maintenance. Here we demonstrate how exposure to different ZnO nanostructures, namely ZnO commercial nanoparticles and custom-made ZnO nanowires, produce acute cytotoxic effects in human keratinocytes (HaCat) and epithelial cells (HeLa) triggering a dose-dependent cell retraction and collapse. We show how engulfed ZnO nanoparticles dissolve intracellularly, triggering actin filament bundling and structural changes in microtubules, transforming these highly dynamic 25 nm diameter polymers into rigid macrotubes of tubulin, severely affecting cell proliferation and survival. Our results demonstrate that nano-ZnO causes acute cytoskeletal collapse that triggers necrosis, followed by a late reactive oxygen species (ROS)-dependent apoptotic process.

Inhibition of Cancer Cell Migration by Multiwalled Carbon Nanotubes.

Inhibiting cancer cell migration and infiltration to other tissues makes the difference between life and death. Multiwalled carbon nanotubes (MWCNTs) display intrinsic biomimetic properties with microtubules, severely interfering with the function of these protein filaments during cell proliferation, triggering cell death. Here it is shown MWCNTs disrupt the centrosomal microtubule cytoskeletal organization triggering potent antimigratory effects in different cancer cells.

Anti-cancer cytotoxic effects of multiwalled carbon nanotubes.

Recent research has opened new alternatives to traditional chemotherapy treatments using nanomaterials as cytotoxic agents. Anti-cancer nanomedicines do not require specific target sites on key proteins or genes to kill cancer cells and have radically different mechanisms to interact with the living matter. Among 1D nanomaterials, multiwalled carbon nanotubes (MWCNTs) have the intrinsic ability to bind tubulin and interfere with microtubule dynamics, mimicking the effect of traditional cytotoxic microtubule-binding agents such as paclitaxel (taxol®). Here, we review the cytotoxic properties of MWCNTs and show a direct pro-apoptotic effect of these nanomaterials in vitro in different cancer cell lines and tumor cells obtained from surgical specimens. Understanding the bio-synthetic relationship between MWCNTs and microtubules could serve to improve these nanomaterials to be used as broad spectrum antineoplastic agents in combination to traditional microtubule-binding treatments, thus avoiding drug resistance mechanisms in cancer cells.

Three-step versus single-step use of system B: evaluation of gutta-percha root canal fillings and their adaptation to the canal walls.

This study aimed to evaluate the quality of gutta-percha (GP) root canal fillings and their adaptation to the root canal walls, when the System B was used in three steps and a single step to fill three different split-tooth models. Each model was filled 10 times in two different ways. Group A: the System B plugger was used to fill the apical 3 mm of the canal in three steps, and then the Obtura II was used to backfill the rest of the canal. Group B: the System B plugger was inserted just once to a distance 3 mm short of the working length and then backfilled as in Group A. Replication of artificial depressions, presence of voids within the GP mass, and presence of spaces between the GP mass and the root canal walls were evaluated and scored. The individual scores of each parameter evaluated were compared between the two groups and statistically analyzed by use of the Mann-Whitney U test. Group A showed statistically significant (p < 0.05) better scores than Group B concerning the replication of artificial depressions and spaces between the GP mass and the canal walls. It was concluded that better adaptation of the GP mass to the canal walls in the apical third was obtained when the System B plugger was used in three steps.

Radiographic evaluation of root canal multiplicity in mandibular first premolars.

The purpose of this study was to examine the accuracy of radiographic evaluation of root canal multiplicity in mandibular first premolars in vitro. One hundred thirty-nine extracted human mandibular premolars were used. Buccolingual radiographs were taken, and the number of canals in each tooth was determined on radiographs by four dentists using a view box. A sudden narrowing of the main canal was interpreted as a sign of multiple canals. After the radiographic evaluation, the tooth crown was removed. India ink was injected into the root canal system, and the root was cleared to observe the canal morphology. There was no statistically significant difference among the four dentists with respect to the coincidence rate (93%-96%) of the canal number evaluated on radiographs with that identified by cleared teeth observation (p > 0.05, one-way analysis of variance). A sudden narrowing of the main canal on the radiograph was a good criterion to judge root canal multiplicity.

Liquid correlation across the walls in a slit pore: effect on the wetting and drying transition.

The liquid structure next to the walls of a slit pore, immersed in a model simple liquid, is studied through a liquid theory and grand canonical Monte Carlo simulations. A liquid correlation across slit walls, of finite width, is found. This correlation modifies the structure and capillary partial wetting and drying transitions of the nonhomogeneous fluid, when close to its liquid-vapor coexistence curve.

Frequency of transverse anastomoses with and without apical communication in Japanese population teeth.

The aim of this study was to describe and measure the frequency of transverse anastomoses with and without an apical communication in Japanese population teeth. One hundred and twenty-three extracted teeth from Japanese people were used in this study. The sample consisted of: 63 mandibular first molars, 30 maxillary first molars and 30 maxillary first premolars. Access openings were made through the crowns to the pulp chamber and India ink was injected into the coronal pulp space and vacuumed from the apical end. The teeth were cleaned and digital micrographs taken from several angles to identify transverse anastomoses. Fourteen teeth had only one canal and 81 teeth out of 109 (74%) had transverse anastomoses including 6 teeth (5.5%) that had an apical communication. Most of the anastomoses (50) were located in the middle portion of the canal and 22 (20%) teeth showed multiple anastomoses. Special attention must be taken after resection of roots with apparent multiple canals. The potentially exposed exits and/or isthmuses should be taken into consideration during surgical endodontic treatment.

Nanotube interactions with microtubules: implications for cancer medicine.

Carbon nanotubes (CNTs) and microtubules are both hollow nanofibers and have similar dimensions; they both self-assemble and form bundles. These common features prompt their association into biosynthetic polymers in vitro and in vivo. Unlike CNTs, microtubules are highly dynamic protein polymers essential for cell proliferation and migration. Interaction between these filaments inside live cells leads to microtubule dysfunction, mitotic arrest and cell death. Thus, CNTs behave as spindle poisons, same as taxanes, vinca alkaloids or epotilones. Recent findings support the idea that CNTs represent a ground-breaking type of synthetic microtubule-stabilizing agents that could play a pivotal role in future cancer treatments in combination to traditional antineoplastic drugs. Here we review the potential use of CNTs in cancer medicine.

Multiwalled carbon nanotubes hinder microglia function interfering with cell migration and phagocytosis.

The intranasal drug delivery route provides exciting expectations regarding the application of engineered nanomaterials as nano-medicines or drug-delivery vectors into the brain. Among nanomaterials, multiwalled CNTs (MWCNTs) are some of the best candidates for brain cancer therapy since they are well known to go across cellular barriers and display an intrinsic ability to block cancer cell proliferation triggering apoptosis. This study reveals that microglial cells, the brain macrophages and putative vehicles for MWCNTs into the brain, undergo a dose-dependent cell division arrest and apoptosis when treated with MWCNTs. Moreover, it is shown that MWCNTs severely interfere with both cell migration and phagocytosis in live microglia. These results lead to a re-evaluation of the safety of inhaled airborne CNTs and provide strategic clues of how to biocompatibilize MWCNTs to reduce brain macrophage damage and to develop new nanodrugs.

Multiwalled carbon nanotubes display microtubule biomimetic properties in vivo, enhancing microtubule assembly and stabilization.

Microtubules are hollow protein cylinders of 25 nm diameter which are implicated in cytokinetics and proliferation in all eukaryotic cells. Here we demonstrate in vivo how multiwalled carbon nanotubes (MWCNTs) interact with microtubules in human cancer cells (HeLa) blocking mitosis and leading to cell death by apoptosis. Our data suggest that, inside the cells, MWCNTs display microtubule biomimetic properties, assisting and enhancing noncentrosomal microtubule polymerization and stabilization. These features might be useful for developing a revolutionary generation of chemotherapeutic agents based on nanomaterials.

Andrés Posada Arango: el conocimiento de la naturalez, el progreso, la civilización y las razas superiores / Andrés Posada Arango

Es una aproximación a la vida y obra del Doctor Andrés Posada Arango.