Alternative stable states in a wet calcareous dune slack in The Netherlands

Evidence is presented for the occurrence of alternative stable states in a wet calcareous dune slack on the Frisian island of Texel, The Netherlands. An early pioneer stage (0.5 kg m–2 total standing crop) and a more productive later successional stage (2.9 kg m–2) occur side by side, with sharp boundaries between them. The pioneer vegetation has been recorded at the site for more than 62 yr. These features indicate the occurrence of a positive-feedback mechanism that has led to alternative stable states. Analyses of ground and surface water composition, and decalcification depths, indicated that hydrologically the study site can be characterized as a flow-through slack, with exfiltration of calcareous groundwater on one side and infiltration of surface water on the other side of the slack. These differences in hydrological conditions have led to distinct differences in environmental conditions within the dune slack. The occurrence of the two successional stages can, however, not be explained by differences in hydrological conditions since both stages occur side by side in the centre of the dune slack. It is, therefore, more likely that biotic interactions are the cause of the vegetation pattern. Three possible mechanisms for feedback processes are discussed: (1) enhanced nitrogen loss; (2) sulfide toxicity and (3) nutrient accumulation in internal cycle.

An experimental workflow for studying barrier integrity, permeability, and tight junction composition and localization in a single endothelial cell monolayer: Proof of concept

Endothelial and epithelial barrier function is crucial for the maintenance of physiological processes. The barrier paracellular permeability depends on the composition and spatial distribution of the cell-to-cell tight junctions (TJ). Here, we provide an experimental workflow that yields several layers of physiological data in the setting of a single endothelial cell monolayer. Human umbilical vein endothelial cells were grown on Transwell filters. Transendothelial electrical resistance (TER) and 10 kDa FITC dextran flux were measured using Alanyl-Glutamine (AlaGln) as a paracellular barrier modulator. Single monolayers were immunolabelled for Zonula Occludens-1 (ZO-1) and Claudin-5 (CLDN5) and used for automated immunofluorescence imaging. Finally, the same monolayers were used for single molecule localization microscopy (SMLM) of ZO-1 and CLDN5 at the nanoscale for spatial clustering analysis. The TER increased and the paracellular dextran flux decreased after the application of AlaGln and these functional changes of the monolayer were mediated by an increase in the ZO-1 and CLDN5 abundance in the cell–cell interface. At the nanoscale level, the functional and protein abundance data were accompanied by non-random increased clustering of CLDN5. Our experimental workflow provides multiple data from a single monolayer and has wide applicability in the setting of paracellular studies in endothelia and epithelia. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Rescue of respiratory failure in pulmonary alveolar proteinosis due to pathogenic MARS1 variants.

Background Pulmonary alveolar proteinosis (PAP) is a heterogeneous condition with more than 100 different underlying disorders that need to be differentiated to target therapeutic options, which are generally limited. Methods The clinical course of two brothers with pathogenic variants in the methionyl-tRNA synthetase (MARS)1gene was compared to previously published patients. Functional studies in patient-derived fibroblasts were performed and therapeutic options evaluated. Results The younger brother was diagnosed with PAP at the age of 1 year. Exome sequencing revealed the homozygousMARS1variant p.(Arg598Cys), leading to interstitial lung and liver disease (ILLD). At 2 years of age, following surgery hypoglycemia was detected, the pulmonary condition deteriorated, and the patient developed multiorgan failure. Six therapeutic whole lung lavages (WLL) were necessary to improve respiratory insufficiency. Methionine supplementation was started and a high protein diet ensured, leading to complete respiratory recovery. The older brother, homozygous for the sameMARS1variant, had a long-known distinct eating preference of methionine-rich food and showed a less severe clinical phenotype. Decreased aminoacylation activity confirmed the pathogenicity of p.(Arg598Cys) in vitro. In agreement with our review of currently published ILLD patients, the presence of hepatopathy, developmental delay, muscular hypotonia, and anemia support the multisystemic character of the disease. Conclusions Catabolic events can provoke a severe deterioration of the pulmonary situation in ILLD with a need for repetitive WLL. Although the precise role of oral methionine supplementation and high protein intake are unknown, we observed an apparent treatment benefit, which needs to be evaluated systematically in controlled trials