Insights into the chemical composition of Equisetum hyemale by high resolution Raman imaging

Equisetaceae has been of research interest for decades, as it is one of the oldest living plant families, and also due to its high accumulation of silica up to 25% dry wt. Aspects of silica deposition, its association with other biomolecules, as well as the chemical composition of the outer strengthening tissue still remain unclear. These questions were addressed by using high resolution (<1 μm) Confocal Raman microscopy. Two-dimensional spectral maps were acquired on cross sections of Equisetum hyemale and Raman images calculated by integrating over the intensity of characteristic spectral regions. This enabled direct visualization of differences in chemical composition and extraction of average spectra from defined regions for detailed analyses, including principal component analysis (PCA) and basis analysis (partial least square fit based on model spectra). Accumulation of silica was imaged in the knobs and in a thin layer below the cuticula. In the spectrum extracted from the knob region as main contributions, a broad band below 500 cm−1 attributed to amorphous silica, and a band at 976 cm−1 assigned to silanol groups, were found. From this, we concluded that these protrusions were almost pure amorphous, hydrated silica. No silanol group vibration was detected in the silicified epidermal layer below and association with pectin and hemicelluloses indicated. Pectin and hemicelluloses (glucomannan) were found in high levels in the epidermal layer and in a clearly distinguished outer part of the hypodermal sterome fibers. The inner part of the two-layered cells revealed as almost pure cellulose, oriented parallel along the fiber

Dinosterol deltaD values in stratified tropical lakes (Cameroon) are affected by eutrophication

In freshwater settings, dinosterol (4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol) is produced primarily by dinoflagellates, which encompass various species including autotrophs, mixotrophs and heterotrophs. Due to its source specificity and occurrence in lake and marine sediments, its presence and hydrogen isotopic composition (dD) should be valuable proxies for paleohydrological reconstruction. However, because the purity required for hydrogen isotope measurements is difficult to achieve using standard wet chemical purification methods, their potential as a paleohydrological proxy is rarely exploited. In this study, we tested dD values of dinosterol in both particulate organic matter (POM) and sediments of stratified tropical freshwater lakes (from Cameroon) as a paleohydrological proxy, the lakes being characterized by variable degrees of eutrophication. In POM and sediment samples, the dD values of dinosterol correlated with lake water dD values, confirming a first order influence of source water dD values. However, we observed that sedimentary dinosterol was D enriched from ca. 19 to 54‰ compared with POM dinosterol. The enrichment correlated with lake water column conditions, mainly the redox potential at the oxic–anoxic interface (Eh OAI). The observations suggest that paleohydrologic reconstruction from dD values of dinosterol in the sediments of stratified tropical lakes ought to be sensitive to the depositional environment, in addition to lake water dD values, with more positive dinosterol dD values potentially reflecting increasing lake eutrophication. Furthermore, in lake sediments, the concentration of partially reduced vs. non-reduced C34 botryococcenes, stanols vs. stenols, and bacterial (diploptene, diplopterol and bb-bishomohopanol) vs. planktonic/terrestrial lipids (cholesterol, campesterol and dinosterol) correlated with Eh OAI. We suggest using such molecular proxies for lake redox conditions in combination with dinosterol dD values to evaluate the effect of lake trophic status on sedimentary dinosterol dD values, as a basis for accurately reconstructing tropical lake water dD values

Hydrogen isotope ratios of lacustrine sedimentary n-alkanes as proxies of tropical African hydrology: insights from a calibration transect across Cameroon

Hydrogen isotope values (δD) of sedimentary aquatic and terrestrial lipid biomarkers, originating from algae, bacteria, and leaf wax, have been used to record isotopic properties of ancient source water (i.e., precipitation and/or lake water) in several mid- and high-latitude lacustrine environments. In the tropics, however, where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes, calibration studies for this proxy are not yet available. To close this gap of knowledge, we sampled surface sediments from 11 lakes in Cameroon to identify those hydro-climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers. Here we present a robust framework for the application of compound-specific hydrogen isotopes in tropical Africa. Our results show that the δD values of the aquatic lipid biomarker n-C17 alkane were not correlated with the δD values of lake water. Carbon isotope measurements indicate that the n-C17 alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis. We demonstrate that the δD values of the n-C29 alkane were correlated with the δD values of surface water (i.e., river water and groundwater), which, on large spatial scales, reflect the isotopic composition of mean annual precipitation. Such a relationship has been observed at higher latitudes, supporting the robustness of the leaf-wax lipid δD proxy on a hemispheric spatial scale. In contrast, the δD values of n-C31 alkane did not show such a relationship but instead were correlated with the evaporative lake water δD values. This result suggests distinct water sources for both leaf-wax lipids, most likely originating from two different groups of plants. These new findings have important implications for the interpretation of long-chain n-alkane δD records from ancient lake sediments. In particular, a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources. Our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and/or growth form of organisms and therefore, the source of hydrogen used during lipid biosynthesis

Unexplained Splenomegalies : Interim Data of the French Prospective Multi-Center Splenomegaly Study (SMS)

International audienc

La grotte des Planches-près-Arbois (Jura)

Barbier Aline, Boudin R.-C., Chaix Louis, Délibrias Georgette, Erroux J., Lundström-Baudais Karen, Passard Françoise, Pétrequin Anne-Marie, Petrequin Pierre, Picard P., Piningre J F, Rutkowski H., Urlacher J. P., Séné G., Vuaillat Dominique. La grotte des Planches-près-Arbois (Jura). In: Gallia préhistoire, tome 24, fascicule 1, 1981. pp. 145-200

Methods for the examination of cattle, sheep and goat dung in prehistoric wetland settlements with examples of the sites Alleshausen-Täschenwiesen and Alleshausen-Grundwiesen (around cal 2900 BC) at Lake Federsee, south-west Germany

There has been evidence of dung in lakeside and moorland settlements since the beginning of wetland archaeology in the 19th century. While evidence has been found for the easily discernible faecal pellets of sheep and goats, recognition of cattle dung has proven to be considerably more difficult. In this study, we give an overview of evidence for dung remains in prehistoric wetland settlements in Germany, Switzerland and eastern France. Various methods for the analysis of uncharred dung remains are reviewed ‐ analyses of plant macro- and microremains, micromorphology and palaeoparasitology ‐ and are applied to two late Neolithic sites in Germany, Alleshausen-Täschenwiesen and Alleshausen-Grundwiesen. It will be shown that at Alleshausen-Täschenwiesen small ruminants were penned during the whole winter and fed on leaf hay unlike Alleshausen-Grundwiesen, where cattle browsed/grazed in the open during the day and were herded into the settlement during the night ‐ both in summer and in winter. Dung - Wiederkäuer-Dung - Seeufer - Viehhaltung - Viehfutter - Mikromorphologie - Parasi