Glacier Forelands – Unique Field Laboratories for the Study of Primary Succession of Plants

While receding glaciers in several respects are related to negative consequences for resident people down river (e.g., water security, glacial lake outburst floods, etc.), from an ecological point of view, they are unique field laboratories to study vegetation development and dynamics from the very beginning. As the bare ground exposed by the receding glaciers generally does not provide a seed bank, the colonization of formerly ice-covered ground represents a true primary succession. There are two different approaches to study vegetation dynamics in glacier forelands: permanent plots and chronosequences (“space for time substitution”). As both procedures have their respective pros and cons, they should not be regarded to be mutually exclusive; rather, they should complement each other for a comprehensive understanding of the vegetation dynamics in glacier forelands. This chapter gives a general overview on patterns and processes of vegetation development in glacier forelands based on vegetation sampling in two glacier forelands of the Eastern Alps employing both abovementioned approaches. Sampling records groundcover of all vascular plants, structural features such as life form composition and dispersal biology types of the species as well as site characteristics. The two different approaches give evidence for both the early vegetation dynamics after deglaciation by the permanent plot studies and for potential future developments by the chronosequences

Liver Fibrosis-4 index indicates atrial fibrillation in acute ischemic stroke

BACKGROUND: Non-alcoholic fatty liver disease and particularly liver fibrosis is related to cardiovascular disease and may indicate an increased risk for atrial fibrillation (AF), but this association has not yet been systematically investigated in a cohort of ischemic stroke patients. METHODS: We analyzed data from a prospective single-center study enrolling all consecutive ischemic stroke patients admitted to our stroke unit over a one-year-period. All patients received a thorough etiological work-up. For evaluation of liver fibrosis, we determined the FIB-4 index, a well-established noninvasive liver fibrosis test. Laboratory results were analyzed from a uniform blood sample taken at stroke unit admission. RESULTS: Of 414 included patients (mean age 70.2 years, 57.7% male), FIB-4 indicated advanced liver fibrosis in 92 (22.2%). AF as the underlying stroke mechanism was present in 28.0% (large vessel disease: 25.6%, small vessel disease: 11.4%, cryptogenic: 29.2%). Patients with FIB-4 ≥2.67 had higher rates of AF (53.3% vs. 20.8%, p<0.001), this association remained significant after correction for established AF risk factors (Odds Ratio 2.53, 95% confidence interval 1.44-4.46, p=0.001). FIB-4 was further associated with worse functional outcome three months (p<0.001) and higher mortality four years post-stroke (p<0.02), but these relationships were no longer present after correction for age and initial stroke severity. Moreover, FIB-4 did not associate with long-term recurrent vascular events. CONCLUSIONS: Liver fibrosis assessed by the FIB-4 index is independently associated with AF in acute ischemic stroke patients. Further studies should evaluate whether adding the FIB-4 index to AF risk scores increases their precision

Lysosomal Acid Lipase Hydrolyzes Retinyl Ester and Affects Retinoid Turnover

Lysosomal acid lipase (LAL) is essential for the clearance of endocytosed cholesteryl ester and triglyceride-rich chylomicron remnants. Humans and mice with defective or absent LAL activity accumulate large amounts of cholesteryl esters and triglycerides in multiple tissues. Although chylomicrons also contain retinyl esters (REs), a role of LAL in the clearance of endocytosed REs has not been reported. In this study, we found that murine LAL exhibits RE hydrolase activity. Pharmacological inhibition of LAL in the human hepatocyte cell line HepG2, incubated with chylomicrons, led to increased accumulation of REs in endosomal/lysosomal fractions. Furthermore, pharmacological inhibition or genetic ablation of LAL in murine liver largely reduced in vitro acid RE hydrolase activity. Interestingly, LAL-deficient mice exhibited increased RE content in the duodenum and jejunum but decreased RE content in the liver. Furthermore, LAL-deficient mice challenged with RE gavage exhibited largely reduced post-prandial circulating RE content, indicating that LAL is required for efficient nutritional vitamin A availability. In summary, our results indicate that LAL is the major acid RE hydrolase and required for functional retinoid homeostasis

Pharmacological Applications of Bile Acids and Their Derivatives in the Treatment of Metabolic Syndrome

Apart from well-known functions of bile acids in digestion and solubilization of lipophilic nutrients and drugs in the small intestine, the emerging evidence from the past two decades identified the role of bile acids as signaling, endocrine molecules that regulate the glucose, lipid, and energy metabolism through complex and intertwined pathways that are largely mediated by activation of nuclear receptor farnesoid X receptor (FXR) and cell surface G protein-coupled receptor 1, TGR5 (also known as GPBAR1). Interactions of bile acids with the gut microbiota that result in the altered composition of circulating and intestinal bile acids pool, gut microbiota composition and modified signaling pathways, are further extending the complexity of biological functions of these steroid derivatives. Thus, bile acids signaling pathways have become attractive targets for the treatment of various metabolic diseases and metabolic syndrome opening the new potential avenue in their treatment. In addition, there is a significant effort to unveil some specific properties of bile acids relevant to their intrinsic potency and selectivity for particular receptors and to design novel modulators of these receptors with improved pharmacokinetic and pharmacodynamic profiles. This resulted in synthesis of few semi-synthetic bile acids derivatives such as 6a-ethyl-chenodeoxycholic acid (obeticholic acid, OCA), norursodeoxycholic acid (norUDCA), and 12-monoketocholic acid (12-MKC) that are proven to have positive effect in metabolic and hepato-biliary disorders. This review presents an overview of the current knowledge related to bile acids implications in glucose, lipid and energy metabolism, as well as a potential application of bile acids in metabolic syndrome treatment with future perspectives

Hepatic progenitor cells of biliary origin with liver repopulation capacity

Hepatocytes and cholangiocytes self-renew following liver injury. Following severe injury hepatocytes are increasingly senescent, but whether hepatic progenitor cells (HPCs) then contribute to liver regeneration is unclear. Here, we describe a mouse model where the E3 ubiquitin ligase Mdm2 is inducibly deleted in more than 98% of hepatocytes, causing apoptosis, necrosis and senescence with nearly all hepatocytes expressing p21. This results in florid HPC activation, which is necessary for survival, followed by complete, functional liver reconstitution. HPCs isolated from genetically normal mice, using cell surface markers, were highly expandable and phenotypically stable in vitro. These HPCs were transplanted into adult mouse livers where hepatocyte Mdm2 was repeatedly deleted, creating a non-competitive repopulation assay. Transplanted HPCs contributed significantly to restoration of liver parenchyma, regenerating hepatocytes and biliary epithelia, highlighting their in vivo lineage potency. HPCs are therefore a potential future alternative to hepatocyte or liver transplantation for liver disease

<scp>ReSurveyEurope</scp>: A database of resurveyed vegetation plots in Europe

AbstractAimsWe introduce ReSurveyEurope — a new data source of resurveyed vegetation plots in Europe, compiled by a collaborative network of vegetation scientists. We describe the scope of this initiative, provide an overview of currently available data, governance, data contribution rules, and accessibility. In addition, we outline further steps, including potential research questions.ResultsReSurveyEurope includes resurveyed vegetation plots from all habitats. Version 1.0 of ReSurveyEurope contains 283,135 observations (i.e., individual surveys of each plot) from 79,190 plots sampled in 449 independent resurvey projects. Of these, 62,139 (78%) are permanent plots, that is, marked in situ, or located with GPS, which allow for high spatial accuracy in resurvey. The remaining 17,051 (22%) plots are from studies in which plots from the initial survey could not be exactly relocated. Four data sets, which together account for 28,470 (36%) plots, provide only presence/absence information on plant species, while the remaining 50,720 (64%) plots contain abundance information (e.g., percentage cover or cover–abundance classes such as variants of the Braun‐Blanquet scale). The oldest plots were sampled in 1911 in the Swiss Alps, while most plots were sampled between 1950 and 2020.ConclusionsReSurveyEurope is a new resource to address a wide range of research questions on fine‐scale changes in European vegetation. The initiative is devoted to an inclusive and transparent governance and data usage approach, based on slightly adapted rules of the well‐established European Vegetation Archive (EVA). ReSurveyEurope data are ready for use, and proposals for analyses of the data set can be submitted at any time to the coordinators. Still, further data contributions are highly welcome.</jats:sec

Better Resilient than Resistant—Regeneration Dynamics of Storm-Disturbed Mangrove Forests on the Bay Island of Guanaja (Honduras) during the First Two Decades after Hurricane Mitch (October 1998)

Located at the interface of land and sea, Caribbean mangroves frequently experience severe disturbances by hurricanes, but in most cases storm-impacted mangrove forests are able to regenerate. How exactly regeneration proceeds, however, is still a matter of debate: does—due to the specific site conditions—regeneration follows a true auto-succession with exactly the same set of species driving regeneration that was present prior to the disturbance, or do different trajectories of regeneration exist? Considering the fundamental ecosystem services mangroves provide, a better understanding of their recovery is crucial. The Honduran island of Guanaja offers ideal settings for the study of regeneration dynamics of storm-impacted mangrove forests. The island was hit in October 1998 by Hurricane Mitch, one of the most intense Atlantic storms of the past century. Immediately after the storm, 97% of the mangroves were classified as dead. In 2005, long-term monitoring on the regeneration dynamics of the mangroves of the island was initiated, employing permanent line-transects at six different mangrove localities all around the island, which have been revisited in 2009 and 1016. Due to the pronounced topography of the island, different successional pathways emerge depending on the severity of the previous disturbance

Common Patterns and Diverging Trajectories in Primary Succession of Plants in Eastern Alpine Glacier Forelands

This paper deals with the vegetation development in four glacier forelands, aligned along a distance of 250 km from West to East in the siliceous Eastern Central Alps. The study employs a chronosequence approach, which assumes a temporal sequence in vegetation development by spatially different sites regarding time since deglaciation. The chronosequences cover the area between Little Ice Age (LIA) maximum glacier extent around 1850, and the current glacier terminus. Despite some shortcomings, chronosequences allow the identification of general patterns of primary succession of plants as a function of site age and local environmental conditions, e.g., changes in species richness, ground cover, plant functional traits, and community structure. While there is no shortage of chronosequence studies in glacier forelands of the Alps, a straightforward comparison aimed at the deduction of general successional trajectories is tricky, due to different procedures of vegetation sampling and data analyses. The comparative examination by a standardized sampling and analyzing protocol of four glacier forelands in the Eastern Central Alps presented here proves the existence of several common patterns in primary succession, but also diverging successional trajectories from West to East. While the pioneer stage in all glacier forelands is similar both floristically and structurally, from the early successional stage onwards, differences increase, leading to different phases in the late successional stage, which is shrub dominated throughout in the westernmost study site, herb&ndash;grass&ndash;dwarfshrub dominated throughout in the easternmost study site, and divided into an earlier herb&ndash;grass&ndash;dwarfshrub phase and a later shrub phase in the two study sites in between

Renaturierung und Aufforstung von Mangroven-Wäldern und ihre Bedeutung als CO2-Senken

Renaturation and reforestation of mangrove forests and their importance as CO2 sinks: Mangroves, the tidal forests along tropical and subtropical coastlines, allocate a disproportionately high amount of carbon per area unit compared to other forest biomes of the world. Thus, mangroves are considered an important nature-based tool for climate change mitigation by their high carbon sequestering capacity. On the other hand, mangroves are one of the most seriously threatened ecosystem of the world due to deforestation and anthropogenic conversion, with loss rates higher than those of tropical rain forests – potential carbon sinks become carbon sources, amplifying climate change. As mangroves achieve many other ecosystem services beside sequestering CO2, initiatives and projects for the rehabilitation of disturbed or lost former mangrove forests increased in recent times. As these measures are labor-intensive and often not successful, they must be critically considered. In addition, as mangroves are spatially restricted by very distinct site conditions, their effect for carbon sequestration on a global scale is limited. On a local scale, however, in particular for countries with low CO2-emissions and extensive coastlines, mangroves can play a more substantial role for climate change mitigation, if deforestation of mangroves is stopped, their areal extent enlarged and additional programs for reducing CO2-emissions are implemented