Search

The biomisation method is used to reconstruct Latin American vegetation at 6000±500 and 18 000±1000 radiocarbon years before present (14C yr BP) from pollen data. Tests using modern pollen data from 381 samples derived from 287 locations broadly reproduce potential natural vegetation. The strong temperature gradient associated with the Andes is recorded by a transition from high altitude cool grass/shrubland and cool mixed forest to mid-altitude cool temperate rain forest, to tropical dry, seasonal and rain forest at low altitudes. Reconstructed biomes from a number of sites do not match the potential vegetation due to local factors such as human impact, methodological artefacts and mechanisms of pollen representivity of the parent vegetation. At 6000±500 14C yr BP 255 samples are analysed from 127 sites. Differences between the modern and the 6000±500 14C yr BP reconstruction are comparatively small; change relative to the modern reconstruction are mainly to biomes characteristic of drier climate in the north of the region with a slight more mesic shift in the south. Cool temperate rain forest remains dominant in western South America. In northwestern South America a number of sites record transitions from tropical seasonal forest to tropical dry forest and tropical rain forest to tropical seasonal forest. Sites in Central America show a change in biome assignment, but to more mesic vegetation, indicative of greater plant available moisture, e.g. on the Yucatàn peninsula sites record warm evergreen forest, replacing tropical dry forest and warm mixed forest presently recorded. At 18 000±1000 14C yr BP 61 samples from 34 sites record vegetation reflecting a generally cool and dry environment. Cool grass/shrubland is prevalent in southeast Brazil whereas Amazonian sites record tropical dry forest, warm temperate rain forest and tropical seasonal forest. Southernmost South America is dominated by cool grass/shrubland, a single site retains cool temperate rain forest indicating that forest was present at some locations at the LGM. Some sites in Central Mexico and lowland Colombia remain unchanged in the biome assignments of warm mixed forest and tropical dry forest respectively, although the affinities that these sites have to different biomes do change between 18 000±1000 14C yr BP and present. The "unresponsive" nature of these sites results from their location and the impact of local edaphic influence. [ABSTRACT FROM AUTHOR]

The article investigates the effect of single vegetation elements on the pattern of average wind speed and sediment transport in the Sahelian zone in Burkina Faso. According to the authors, soil loss is a widespread phenomenon in the area due to wind erosion and that Sahelian farmers believe that scattered vegetation can help in controlling the phenomenon. They conducted a study in Burkina Faso during the rainy seasons of 2002 to 2003 that involved measuring wind speeds using three sonic anemometers and determining sediment transport. Furthermore, the study concluded that shrubs and trees were essential in reducing soil loss.

A surface energy balance model with a multilayer canopy representation has been developed to simulate the vertical temperature distribution of the foliage elements and the soil underneath. This model allows one to simulate the radiative temperature of the complex vegetation-covered surface as a function of the angle of observation. The model was implemented for a two-layer canopy and has been tested by comparing simulated radiative surface temperatures (observed under a look angle of 45°), latent heat, sensible heat, momentum, and ground heat fluxes, and soil temperatures at different depths, with observed data, gathered in a maize field. The fluxes above the canopy were measured by eddy correlation methods. This paper describes the model structure and simulation results as compared with the field measurements. Except for the ground heat fluxes, all the simulated and measured parameters match reasonably well. Further, the model was used to study the sensitivity of the radiative temperature of the complex surface to variations in the roughness length z0, the leaf area index LAI, and the drag coefficient C d. The radiative surface temperature turned out to be very insensitive to variations in C d and LAI, and it was found that resulting variations in the radiative surface temperature fall well within the detection error of the remotely sensed surface temperature. [ABSTRACT FROM AUTHOR]

Vegetation density on foredunes exerts an important control on aeolian sediment transport and deposition, and therefore on profile development. In a long-term monitoring field experiment, three plots were planted with regular grids of reed bundles in three different densities: 4, 2 and 1 bundles per m2. This study reports on the differences in profile development under the range of vegetation densities. Topographic profiles were measured between May 1996 and April 1997. Results indicate important differences in profile development forthe three reed bundle densities: in the highest density plot a distinct, steep dune developed, while in the lowest density a more gradualand smooth sand ramp was deposited. When the stems had been completely buried, differences in profile evolution vanished. After a second planting of reed stems in January 1997 the process was repeated. In May 1997, all plots had gained a sand volume ranging from 1175 to 1273m3 m-1, indicating that the sediment budget isrelatively constant, regardless of the particular profile evolution.The field evidence is compared with simulations of profile development, generated by the foredune development model SAFE. The model successfully reproduces the overall profile development, but in general, the equations used for vegetation-transport interaction overestimate the effect of vegetation. This causes some deviations between field and model results. Several reasons for this are discussed. Based on theexperiments reported here, recommendations are given for further research. [ABSTRACT FROM AUTHOR]

This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and empirical relationships, describing the influence of meteorological conditions, topography, sediment characteristics and vegetation. A so-called adaptation length is incorporated to calculate the development of transport equilibrium along the profile. Changes in topography are derived from the predicted transport, using the continuity equation. Vegetation height is incorporated in the model as a dynamic variable. Vegetation can be buried during transport events, which results in important changes in the sediment transport rates. The sediment transport model is dynamically linked to a second-order closure air flow model, which predicts friction velocities overthe profile, influenced by topography and surface roughness. Modelling results are shown for (a) the growth and migration of bare, initially sine-shaped dunes, and (b) dune building on a partly vegetated and initially flat surface. Results show that the bare symmetrical dunes change into asymmetric shapes with a slipface on the lee side. Thisresult could only be achieved in combination with the secondorder closure model for the calculation of air flow. The simulations with thepartly vegetated surfaces reveal that the resulting dune morphology strongly depends on the value of the adaptation length parameter and on the vegetation height. The latter result implies that the dynamical interaction between aeolian activity and vegetation (reaction to burial, growth rates) is highly relevant in dune geomorphology and deserves much attention in future studies. [ABSTRACT FROM AUTHOR]

In an inner dune area in the Dutch coastal dunes several artificially stabilized blowouts were reactivated. The purpose was to investigate whether these reactivated blowouts could remain active despite the increased atmospheric deposition of nutrients, how much area would beaffected by sand from the blowouts, whether the vegetation would respond to the deposition of sand, and whether the reactivation of blow outs could be a measure against the effects of acidification and eutrophication. This paper presents the results of the first years of monitoring the changes in the blowout morphology and the response of thevegetation. In the monitoring period (1991--1994) the blowouts remained active and grew slowly in size and depth. The area which receivesmore than 1 cm of calcareous sand from the blowout in three years was up to six times the area of the blowouts. Moss vegetation respondedto the accumulation of sand: Campylopus introflexus was sparse within the deposition area whereas Tortula ruralis was found near the contour of 1 cm deposition in 3 yr. No indications were found that shrubsor marram grass were adversely affected by the deposition of sand. The experiment forms part of a programme to test measures aimed at mitigating the effects of air pollution on natural landscapes. From the viewpoint of the programme the experiment is a success. [ABSTRACT FROM AUTHOR]

Adequate levels of thyroid hormones (THs) in the fetal brain are vital for early neurodevelopment. Most of the TH in fetal brain is derived from circulating thyroxine (T4), which gets locally converted into the biologically active triiodothyronine (T3) by deiodinase enzymes. One of the major routes of TH into the brain is through the blood-cerebrospinal fluid barrier (BCSFB). The BCSFB is maintained by the choroid plexus (CP), which separates the blood from the cerebrospinal fluid (CSF). TH transport across the BCSFB is facilitated by TH transmembrane transporters (THTMTs) present in the CP. However, TH transport across the BCSFB is still poorly understood as there is a lack of human representative BCSFB models. Previously, a human choroid plexus papilloma cell line (HIBCPP) has been established, which exhibits certain key characteristics of the human CP. In this study, the suitability of the HIBCPP cell line as a human in vitro BCSFB model for TH transport was evaluated. For this, HIBCPP cells were grown on transwell inserts and the gene and protein expression of several THTMTs was assessed using qPCR and immunohistochemistry. Additionally, the transport of T4 across a HIBCPP monolayer was assessed using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), with a special focus on the role of transthyretin (TTR), a TH binding protein produced by the CP involved in TH transport across the BCSFB. Finally, inhibition studies were performed with various THTMT inhibitors, to conclude which THTMT drive TH transport across the BCSFB. Gene and protein expression data showed that several THTMTs were expressed in the HIBCPP model, however HIBCPP cells lacked key THTMTs, notably monocarboxylate transporter 8 (MCT8) and organic anion transporter polypeptide 1C1 (OATP1C1), known to be highly expressed in the human BCSFB. Moreover, TH transport across the HIBCPP model was low and addition of TTR did not increase this transport. Two TTR-binding chemicals, TBBPA and F21388, significantly decreased the transport of T4 across the HIBCPPs cells, suggesting a possible role of intracellular TTR in the transport of T4 across the BCSFB. The transport of TTR-T4 complex might be mediated through SR-B1, indicated by the decreased T4 transport after BLT-1 exposure. However, the poor expression of several important THTMTs, together with the low amount of TH transport, indicate that the HIBCPP cells lack key features that drive TH transport in the BCSFB. The HIBCPP cells could serve as a model to further study the mechanisms of TTR driven TH transport, but for the identification of THTMTs more in vivo accurate BCSFB models are necessary., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

While many plastic additives show endocrine disrupting properties, this has not been studied for micro- and nanoplastics (MNPs) particles despite their ubiquitous presence in humans. The objective of this study was to determine the effects of various sizes and concentrations of polystyrene (PS)-MNPs (50-10,000 nm, 0.01-100 μg/mL) on estrogen- and androgen receptor (ER and AR) activity and steroidogenesis in vitro. Fluorescent (F)PS-MNPs of ≤1000 nm were internalized in VM7 and H295R cells and FPS-MNPs ≤200 nm in AR-ecoscreen cells. H295R cells displayed the highest uptake and particles were closer to the nucleus than other cell types. None of the sizes and concentrations PS-MNPs tested affected ER or AR activity. In H295R cells, PS-MNPs caused some statistically significant changes in hormone levels, though these showed no apparent concentration or size-dependent patterns. Additionally, PS-MNPs caused a decrease in estriol (E3) with a maximum of 37.5 % (100 μg/mL, 50 nm) and an increase in gene expression of oxidative stress markers GPX1 (1.26-fold) and SOD1 (1.23-fold). Taken together, our data show limited endocrine-disrupting properties of PS-MNPs in vitro. Nevertheless the importance of E3 in the placenta warrants further studies in the potential effects of MNPs during pregnancy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Micro- and nanoplastics (MNPs) are emerging pollutants of concern with ubiquitous presence in global ecosystems. MNPs pose potential implications for human health; however, the health impacts of MNP exposures are not yet understood. Recent evidence suggests that MNPs can cross the placental barrier, underlying the urgent need to understand their impact on reproductive health and development., Objective: The Actionable eUropean ROadmap for early-life health Risk Assessment of micro- and nanoplastics (AURORA) project will investigate MNP exposures and their biological and health effects during pregnancy and early life, which are critical periods due to heightened vulnerability to environmental stressors. The AURORA project will enhance exposure assessment capabilities for measuring MNPs, MNP-associated chemicals, and plastic additives in human tissues, including placenta and blood., Methods: In this interdisciplinary project, we will advance methods for in-depth characterization and scalable chemical analytical strategies, enabling high-resolution and large-scale toxicological, exposure assessment, and epidemiological studies. The AURORA project performs observational studies to investigate determinants and health impacts of MNPs by including 800 mother-child pairs from 2 existing birth cohorts and 110 women of reproductive age from a newly established cohort. This will be complemented by toxicological studies using a tiered-testing approach and epidemiological investigations to evaluate associations between maternal and prenatal MNP exposures and health perturbations, such as placental function, immune-inflammatory responses, oxidative stress, accelerated aging, endocrine disruption, and child growth and development. The ultimate goal of the AURORA project is to create an MNP risk assessment framework and identify the remaining knowledge gaps and priorities needed to comprehensively assess the impact of MNPs on early-life health., Results: In the first 3 years of this 5-year project (2021-2026), progress was made toward all objectives. This includes completion of recruitment and data collection for new and existing cohorts, development of analytical methodological protocols, and initiation of the toxicological tiered assessments. As of September 2024, data analysis is ongoing and results are expected to be published starting in 2025., Conclusions: As plastic pollution increases globally, it is imperative to understand the impact of MNPs on human health, particularly during vulnerable developmental stages such as early life. The contributions of the AURORA project will inform future risk assessment., International Registered Report Identifier (irrid): DERR1-10.2196/63176., (©Amanda M Durkin, Runyu Zou, Justin M Boucher, Matthew SP Boyles, Jeske van Boxel, Mariona Bustamante, Emily A Christopher, Payam Dadvand, Hanna M Dusza, Majorie van Duursen, Markus M Forsberg, Karen S Galea, Juliette Legler, Laurens DB Mandemaker, Florian Meirer, Jane Muncke, Tim S Nawrot, Petra Přibylová, Anna R Robuck, Nelly D Saenen, Barbara M Scholz-Böttcher, Kuanliang Shao, Martine Vrijheid, Douglas I Walker, Lisa Zimmermann, Laura M Zoutendijk, Virissa Lenters, Roel Vermeulen. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 08.10.2024.)

Micro- and nanoplastics (MNPs) are ubiquitous in the environment and have recently been found in human lungs, blood and placenta. However, data on the possible effects of MNPs on human health is extremely scarce. The potential toxicity of MNPs during pregnancy, a period of increased susceptibility to environmental insults, is of particular concern. The placenta provides a unique interface between maternal and fetal circulation which is essential for in utero survival and healthy pregnancy. Placental toxicokinetics and toxicity of MNPs are still largely unexplored and the limited studies performed up to now focus mainly on polystyrene particles. Practical and ethical considerations limit research options in humans, and extrapolation from animal studies is challenging due to marked differences between species. Nevertheless, diverse in vitro and ex vivo human placental models exist e.g., plasma membrane vesicles, mono-culture and co-culture of placental cells, placenta-on-a-chip, villous tissue explants, and placental perfusion that can be used to advance this research area. The objective of this concise review is to recapitulate different human placental models, summarize the current understanding of placental uptake, transport and toxicity of MNPs and define knowledge gaps. Moreover, we provide perspectives for future research urgently needed to assess the potential hazards and risks of MNP exposure to maternal and fetal health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Lymphocytes infiltrating synovial membranes were characterized in eight patients with proliferative rheumatoid synovitis. Surface immunoglobulins were studied with use of immunofluorescence, and the C3 receptor was detected by adherence of red cells coated with antibody and complement - both are B-cell markers. Spontaneous rosette formation with sheep erythrocytes was used as a T-cell marker. To obtain viable lymphocytes in suspension, the villous synovium of five of these patients was digested with collagenase and deoxyribonuclease. Populations enriched in lymphocytes could be obtained by velocity sedimentation. Whereas only 9 to 35 per cent of lymphocytes bore surface immunoglobulins, the majority (70 to 85 per cent) formed sheep-erythrocyte rosettes. Cells bearing the C3 receptor constituted a distinct minority of synovial lymphocytes in frozen-tissue sections, and were found in follicle-like accumulations. These data indicate that the predominant infiltrating lymphocyte in proliferative rheumatoid synovitis is a T cell.

A substantial fraction of human cord blood and peripheral blood lymphocytes have recently been shown to bear IgD. Although IgD has not been identified in mice, it has been suggested that it is also a major surface immunoglobulin of murine lymphocytes. Thus, lactoperoxidase-catalyzed iodination of surface immunoglobulin of mouse spleen and lymph node cells reveals the existence of an IgH chain differing from mu, gamma, and alpha-chain both antigenically and by mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This new H chain class has been previously proposed to be the mouse homologue of delta-chain. In this paper, we analyzed human, mouse, guinea pig, and rabbit lymphoid cell membrane Ig by lactoperoxidase-catalyzed iodination, extraction with non-ionic detergent precipitation with a variety of specific anti-Ig sera, and electrophoresis of dissolved reduced precipitates on sodium dodecyl sulfate-polyacrylamide gels. Our studies confirm the previous reports of a new mouse cell membrane H chain with a mobility more rapid than that of mu-chain. However, we fail to detect a molecule with this electrophoretic mobility on the surface of guinea pig or rabbit lymph node and spleen cells. Moreover, neither anti-kappa nor anti-delta antibody precipitates a molecule with an H chain of this mobility from labeled extracts of human cord blood or peripheral blood lymphocytes. Cell surface delta was identified on both human cord blood and peripheral blood lymphocytes, but it proved to have mobility similar to human and mouse mu-chain. This result indicates either that mouse delta-chain has an electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gels which differs appreciably from that of human membrane delta-chain or that the newly described mouse H chain is not the homologue of human delta-chain.

Experimental autoimmune thyroiditis was induced in out-bred guinea pigs by isoimmunization with thyroid extract in complete Freund's adjuvant. A digestion procedure using collagenase and deoxyribonuclease was used to make viable single-cell suspensions of pooled thyroid glands from groups of animals with advanced degrees of thyroiditis. Thymus-derived or T lymphocytes, identified by their capacity to form E rosettes with rabbit erythrocytes, were found to be the predominant (75%) infiltrating lymphocyte; bone marrow-derived or B cells consitituted most of the remainder. The infiltrates of inbred animals with thyroiditis were demonstrated to contain cells capable of mediating antibody-dependent lymphoid cell-mediated cytotoxicity.

Heat-aggregated guinea pig gamma-globulin was shown to bind to the surface membrane of a subclass of guinea pig T lymphocytes. Cells of this subpopulation were identified as T lymphocytes because these cells did not stain for surface Ig (a B-cell marker) but did form spontaneous E-rosettes with rabbit erythrocytes (a T-cell marker). A strikingly high proportion of such aggregate-binding (Agg(+)), E-rosette-forming (E-rosette(+)), but surface Ig-negative (Ig(-)) cells were found in an inflammatory exudate. Thus purified peritoneal exudate lymphocytes (PELs) are known to consist of over 90% T cells, and 59% of these cells bound aggregates. 10% of these Agg+ Ig- E-rosette+ cells were found in draining lymph node cell populations and none in thymus cell populations. The high frequency amongst PELs suggested that these Aggregate+ Ig- E-rosette+ cells might be activated T cells as these are known to occur in high proportion in PEL populations. Confirmatory evidence for this postulate was provided by the striking increase (from 10% to 46%) of Ig- E-rosette+ cells that bound aggregates when lymph node cells were activated by antigen stimulation in vitro.

The capacity of lymphoid cells from nonsensitized mice to lyse antibody-coated target erythrocytes in vitro does not require the presence of thymus-derived or thymus-dependent lymphocytes. Thus, spleen cells from thymus-deprived mice and spleen cell populations from which thymus-dependent lymphocytes had been removed were fully competent to mediate destruction of antibody-coated target cells. However, prior treatment of spleen cell populations with antibody to kappa chains diminished this function, suggesting a role for bone marrow-derived lymphocytes.