Martin Luther University of Halle-Wittenberg

About: Martin Luther University of Halle-Wittenberg is a education organization based out in Halle, Germany. It is known for research contribution in the topics: Population & Liquid crystal. The organization has 20232 authors who have published 38773 publications receiving 965004 citations. The organization is also known as: MLU & University of Wittenberg.

Melatonin, endocrine pancreas and diabetes.

Abstract: Melatonin influences insulin secretion both in vivo and in vitro (i) The effects are MT(1)-and MT(2)-receptor-mediated (ii) They are specific, high-affinity, pertussis-toxin-sensitive, G(i)-protein-coupled, leading to inhibition of the cAMP-pathway and decrease of insulin release [Correction added after online publication 4 December 2007: in the preceding sentence, 'increase of insulin release' was changed to 'decrease of insulin release'] Furthermore, melatonin inhibits the cGMP-pathway, possibly mediated by MT(2) receptors In this way, melatonin likely inhibits insulin release A third system, the IP(3)-pathway, is mediated by G(q)-proteins, phospholipase C and IP(3), which mobilize Ca(2+) from intracellular stores, with a resultant increase in insulin (iii) Insulin secretion in vivo, as well as from isolated islets, exhibits a circadian rhythm This rhythm, which is apparently generated within the islets, is influenced by melatonin, which induces a phase shift in insulin secretion (iv) Observation of the circadian expression of clock genes in the pancreas could possibly be an indication of the generation of circadian rhythms in the pancreatic islets themselves (v) Melatonin influences diabetes and associated metabolic disturbances The diabetogens, alloxan and streptozotocin, lead to selective destruction of beta-cells through their accumulation in these cells, where they induce the generation of ROS Beta-cells are very susceptible to oxidative stress because they possess only low-antioxidative capacity Results suggest that melatonin in pharmacological doses provides protection against ROS (vi) Finally, melatonin levels in plasma, as well as the arylalkylamine-N-acetyltransferase (AANAT) activity, are lower in diabetic than in nondiabetic rats and humans In contrast, in the pineal gland, the AANAT mRNA is increased and the insulin receptor mRNA is decreased, which indicates a close interrelationship between insulin and melatonin

Positive effects of composted biochar on plant growth and soil fertility

Abstract: Mankind is actually facing serious issues due to the overexploitation of fossil fuels, biomass, soils, nitrogen, and phosphorus It is claimed that biochar addition to soil improves C sequestration to prevent CO2 from atmospheric cycling Biochar addition should also increase soil fertility in a similar way as anthropogenic dark earths of Central Amazonia Previous studies have shown that biochar stimulates plant growth and increase fertilizer efficiency, especially when biochar is combined with organic fertilizers such as compost However, little is known about optimum addition amounts and mixture ratios of biochar and compost Indeed most experiments to mimic Terra preta de Indio focused on biochar alone or biochar in combination with mineral fertilizers Therefore, we studied optimum biochar and compost amounts and mixture ratios with respect to plant response and soil fertility We tested the effect of total amount from 0 to 200 Mg/ha, and biochar proportion from 0 % to 50 % biochar, of 18 different compost mixtures on growth of oat (Avena sativa L) and soil properties in a fully randomized greenhouse study with sandy and loamy soil substrates We sampled soil substrates before and after plant growth and analyzed plant growth and yield, total organic carbon (TOC), total nitrogen (TN), mineralized nitrogen (Nmin), soil reaction (pH), and electrical conductivity (EC) applying standard procedures Results show that biomass production was increased with rising biochar and compost amounts Oat plant height and seed weight was improved only with rising biochar amounts, but not with compost amounts This could be explained by increase of total organic C and total N but not by plant-available ammonium and nitrate The positive influence of composted biochar on plant growth and soil properties suggests that composting is a good way to overcome biochar’s inherent nutrient deficiency, making it a suitable technique helping to refine farm-scale nutrient cycles

Sorptive stabilization of organic matter by microporous goethite: sorption into small pores vs. surface complexation

Abstract: Summary Stabilization of organic matter (OM) by sorption to minerals is thought to be due to (i) sorption into small pores (O < 50 nm) that prevents hydrolytic enzymes approaching and decomposing the organic substrate or (ii) reduced availability of organic molecules after formation of strong multiple bonds by complexation of organic ligands at mineral surfaces. We tested these two potential mechanisms by studying the binding of dissolved OM to microporous goethite (α-FeOOH). The size of organic molecules dissolved prior to and after equilibration with goethite was determined using atomic force microscopy (AFM). The goethite–OM complexes were analysed for bulk and surface elemental composition (by X-ray photoelectron spectroscopy, XPS), specific surface area (SSA) and mesopore and micropore volumes (by N2 adsorption/desorption), by scanning electron microscopy (SEM), and by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The absolute density of goethite–OM complexes was determined by gas pycnometry and the sorbed OM’s apparent density was calculated by assuming no major changes in the volumes of the goethite upon sorption of OM. The stability of the OM–mineral interactions was tested in desorption experiments and by treatment with NaOCl. Surface accumulation of OM by sorption decreased the N2-accessible SSA of the goethite, mostly because micropores (O < 2 nm) were rendered inaccessible to N2. The decrease in accessibility of micropores was most pronounced at small surface OM concentrations. The majority of dissolved organic molecules detected with AFM prior to interaction with goethite were globular with a diameter of 4–10 nm, the rest were mainly linear, 20–100 nm long and 4–8 nm thick. After contact with goethite, the latter type of molecules dominated, which suggests preferential sorption of globular molecules. Their size exceeded or equalled the size of micropores and small mesopores (O < 10 nm) and so sorption therein is unlikely. Also, the changes in volumes of pores with a size of 2–50 nm were smaller than the estimated volume of the OM sorbed. The apparent density of sorbed OM always exceeded that of the freeze-dried OM and was largest at small surface concentrations. DRIFT spectroscopy showed that most carboxyl groups at the goethite surface were in their complexed form. The proportion of complexed carboxyl groups dropped at larger surface concentrations, parallel to the decrease in micropore volume. Thus, micropores seem to favour the formation of multiple complex bonds per molecule. Scanning electron microscopy showed that at small surface concentrations, OM coated the goethite crystals and crystallites tightly, while at larger surface concentrations bulky accumulations of OM were more abundant. Even strongly desorbing reagents such as NaOH and Na pyrophosphate released only part of the sorbed OM. Treatment with NaOCl removed mainly bulky accumulations of OM; the OM tightly bound to goethite crystals was hardly affected by NaOCl. We conclude that molecules tightly bound via multiple complex bonds, probably at the mouths of small pores, are barely desorbable and resist the attack of chemical reagents and probably also of enzymes.