Stefan Kahlert

Stefan Kahlert
Otto-von-Guericke-Universität Magdeburg | OvGU · Institut für Anatomie

Doctor of Philosophy, Dipl.-Ing. (FH)

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71
Publications
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1,546
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Publications

Publications (71)
Article
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Prostate cancer metastasis has an enormous impact on the mortality of cancer patients. Factors involved in cancer progression and metastasis are known to be key players in microgravity (µ g )-driven three-dimensional (3D) cancer spheroid formation. We investigated PC-3 prostate cancer cells for 30 min, 2, 4 and 24 h on the random positioning machin...
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The sensitivity of pigs to deoxynivalenol (DON) might be increased by systemic inflammation (SI), which also has consequences for hepatic integrity. Liver lesions and a dys-regulated gene network might hamper hepatic handling and elimination of DON whereby the way of initiation of hepatic inflammation might play an additional role. First and second...
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In this study, we evaluated changes in focal adhesions (FAs) in two types of breast cancer cell (BCC) lines (differentiated MCF-7 and the triple-negative MDA-MB-231 cell line) exposed to simulated microgravity (s-μg) created by a random positioning machine (RPM) for 24 h. After exposure, the BCC changed their growth behavior and exhibited two pheno...
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The sensitivity of pigs to deoxynivalenol (DON) might be influenced by systemic inflammation (SI) which impacts liver. Besides following acute-phase proteins, our aim was to investigate both the hepatic fractional albumin (ALB) synthesis rate (FSR) and the ALB concentration as indicators of ALB metabolism in presence and absence of SI induced by LP...
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Low concentration of LPS can be detected in healthy mammals without triggering systemic inflammation. Here we analysed the influence of the mycotoxin deoxynivalenol (DON) on very low LPS concentrations and the role of DON in the physiology of pigs challenged with high artificial LPS dosage mimicking septic shock. Pigs were fed for 29 d with DON-con...
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Deoxynivalenol (DON) is a toxin found in cereals as well as in processed products such as pasta, and causes substantial economic losses for stock breeding as it induces vomiting, reduced feeding, and reduced growth rates in piglets. Oxidative phosphorylation, TCA-cycle, transcription, and translation have been hypothesized to be leading pathways th...
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This is a report on the prevalence of Rhagium inquisitor, R. bifasciatum und R. mordax in the area of Bad Dürkheim, Rhineland-Palatinate, Germany between 2004 and 2016. Frequency of occurrence was R. inquisitor > R. bifasciatum > R. mordax. Whereas R. inquisitor was nearly continuously found, R. bifasciatum was not observed after 2011. In contrast,...
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The aim of this study was to investigate the potential modulatory effect of E. coli lipopolysaccharides (LPS) on residues of deoxynivalenol (DON), de-epoxy-deoxynivalenol (DOM-1), zearalenone (ZEN) and its metabolites α-zearalenol (α-ZEL), β-zearalenol (β-ZEL), zearalanone (ZAN), α-zearalanol (α-ZAL) and β-zearalanol (β-ZAL) after pre- or post-hepa...
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The aim of the present study was to examine the role of chronic deoxynivalenol (DON) exposition on the liver morphology and function in combination with pre- and post-hepatic lipopolysaccharide (LPS) stress in young pigs fed for 4 weeks with a DON-contaminated diet (4.59 mg/kg feed). At the end of the experiment, LPS (7.5 μg/kg BW) was administered...
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This study aimed to investigate a potential modulatory effect of E. coli lipopolysaccharide (LPS) on the kinetics of deoxynivalenol (DON) and zearalenone (ZEN) after pre- or post-hepatic LPS administration to unravel the putative role of the liver. Fifteen barrows were fed a diet containing mycotoxin-contaminated maize (4.59 mg DON/kg feed, 0.22 mg...
Article
We studied the constancy of the relationship between rectal and intraabdominal temperature as well as their linkage to inflammatory markers (leucocyte counts, kynurenine-to-tryptophan ratio (Kyn–Trp ratio), tumour necrosis factor alpha (TNF-α) in healthy and in pigs exposed to lipopolysaccharide (LPS) and/or deoxynivalenol (DON). Barrows (n = 44) w...
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Histomorphometry and cell proliferation are markers of intestinal development, which we depinvestigated in pigs from weaning to slaughter at 5 different alonsmall intestinal sites. Furthermore, the impact of age enteral deoxynivalenol (DON) exposure on intestinal (P morphology and proliferation was studied. Postweaning albepigs of 4 categories (1,...
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Weaning triggers an adaptation of the gut function including luminal lactate generation by lactobacilli, depending on gastrointestinal site. We hypothesized that both lactobacilli and lactate influence porcine intestinal epithelial cells. In vivo experiments showed that concentration of lactate was significantly higher in gastric, duodenal and jeju...
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This is a report on the prevalence of Cicindela campestris and C. hybrida in the area of Bad Dürkheim, Rhineland-Palatinate, Germany, between 2002 and 2015. The observations were fitted to a grid (1x1 km UTM squares) and overlaid with the frequencies of visits of the individual squares. C. campestris was frequently found in the Palatinate Forest wh...
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We studied the interaction between deoxynivalenol (DON)-feeding and a subsequent pre- and post-hepatic immune stimulus with the hypothesis that the liver differently mediates the acute phase reaction (APR) in pigs. Barrows (n = 44) were divided into a DON-(4.59 mg DON/kg feed) and a control-diet group, surgically equipped with permanent catheters p...
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Previous studies have shown that chronic oral deoxynivalenol (DON) exposure modulated Escherichia coli lipopolysaccharide (LPS)-induced systemic inflammation, whereby the liver was suspected to play an important role. Thus, a total of 41 barrows was fed one of two maize-based diets, either a DON-diet (4.59 mg DON/kg feed, n = 19) or a control diet...
Article
The porcine intestinal epithelium is a primary target for mycotoxin deoxynivalenol (DON) and lipopolysaccharides (LPS). Although epithelial cells are exposed to these toxins mainly from the luminal-chyme compartment an exposure from the blood side resulting from systemic absorption cannot be excluded. Thus, we investigated the effect of DON and LPS...
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The pig shows genetical and physiological resemblance to human, which predestines it as an experimental animal model especially for mucosal physiology. Therefore, the intestinal epithelial cell lines 1 and J2 (IPEC-1, IPEC-J2)-spontaneously immortalised cell lines from the porcine intestine-are important tools for studying intestinal function. A mi...
Article
The mycotoxin deoxynivalenol (DON) and lipopolysaccharides (LPS) are reported to act synergistically in the animal organism. Thus, we tested the hypothesis that systemic co-exposure of DON and LPS aggravates the impact of the individual toxin on leukocyte counts in vivo and peripheral blood mononuclear cells (PBMC) ex vivo. Growing barrows were fed...
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Pigs might be exposed to lipopolysaccharides (LPS) and deoxynivalenol (DON) at the same time, and both toxins are thought to interactively affect the intestinal barrier, the innate immune system, and the xenobiotics metabolism. Hence, we aimed at examining the single and combined effects of both toxins on nutrient digestibility and DON metabolism....
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The numerous pores in the basement membrane (BM) of the intestinal villi are essential for the communication of enterocytes with cells in the lamina propria, an important mechanism for the induction of intestinal immune responses. The intestinal epithelial barrier is affected by the mycotoxin deoxynivalenol (DON) from both the apical (luminal) and...
Article
The systemic effects of the Fusarium toxin deoxynivalenol (DON) and of bacterial lipopolysaccharides (LPS) were studied in male castrated pigs (40.4±3.7kg) infused intravenously with either DON or LPS alone (100μg DON/kg/h, 7.5μg/LPS/kg/h), or together (100μg DON plus 7.5μg/LPS/kg/h). The Control group received a saline infusion (n=6/treatment, 24h...
Article
Lipopolysaccharides (LPS), a cell wall component of gram-negative bacteria, and deoxynivalenol (DON), a prevalent Fusarium-derived contaminant of cereal grains, are each reported to have detrimental effects on the liver. A potentiating toxic effect of the combined exposure was reported previously in a mouse model and hepatocytes in vitro, but not i...
Article
We investigated a proposed synergistic effect of deoxynivalenol (DON) and lipopolysaccharides (LPS) on small intestinal architecture and epithelial barrier integrity in pigs. Crypt depth and intestinal cell proliferation were analyzed, as well as expression of zonula occludens protein-1 (ZO-1) and β-catenin of the apical junction complex along the...
Article
The plasma elimination kinetics of the Fusarium toxin deoxynivalenol (DON) was investigated in male castrated pigs (40.4±3.7kg) when infused intravenously either alone (100μg/kg/h, n=6) or together with lipopolysaccharides (LPS, 7.5μg/kg/h, n=6). The maximum DON concentration after one hour of infusion was significantly higher by 61% in the DON+LPS...
Article
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The intestinal epithelial cell layer represents the border between the luminal and systemic side of the gut. The decision between absorption and exclusion of substances is the quintessential function of the gut and varies along the gut axis. Consequently, potentially toxic substances may reach the basolateral domain of the epithelial cell layer via...
Article
The aim of this study was to examine the effects of a control diet (CON) or a Fusarium toxin contaminated diet (FUS) with and without HS (CON-HS and FUS-HS, respectively) on pigs during a 10-week growth trial starting at 35.1±3.2 kg live weight (n=12/group). Moreover, 2 additional choice feeding groups were included to test the ability of the pigs...
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The specific function of the epithelium as critical barrier between the intestinal lumen and the organism's internal microenvironment is reflected by permanent maintenance of intercellular junctions and cellular polarity. The intestinal epithelial cells are responsible for absorption of nutritional components, facing mechanical stress and a changin...
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Deoxynivalenol (DON) is a Fusarium derived mycotoxin, often occurring on cereals used for human and animal nutrition. The intestine, as prominent barrier for nutritional toxins, has to handle the mycotoxin from the mucosa protected luminal side (apical exposure), as well as already absorbed toxin, reaching the cells from basolateral side via the bl...
Article
The Fusarium derived mycotoxin deoxynivalenol (DON) is frequently found in cereals used for human and animal nutrition. We studied effects of DON in non-transformed, non-carcinoma, polarized epithelial cells of porcine small intestinal origin (IPEC-1 and IPEC-J2) in a low (200 ng/mL) and a high (2000 ng/mL) concentration. Application of high DON co...
Article
The in vitro effects of deoxynivalenol (DON), de-epoxy-DON, DON-sulfonate (DONS) and sodium metabisulfite (Na(2)S(2)O(5), SBS) on porcine peripheral blood mononuclear cells (PBMC), and on the Intestinal Porcine Epithelial Cell lines IPEC-1 and IPEC-J2 were examined by using the MTT assay. In addition, an uncontaminated and a DON contaminated tritic...
Article
Decreased activity of the mitochondrial thiamin-dependent 2-oxoglutarate dehydrogenase complex (OGDHC) is associated with a number of inborn and acquired neuropathologies. We hypothesized that perturbation in flux through the complex influences brain development and function, in particular, because the OGDHC reaction is linked to the synthesis/degr...
Article
Pristanic acid and phytanic acid are branched-chain fatty acids, which play an important role in diseases with peroxisomal impairment, like Refsum disease (MIM 266500), Zellwegers syndrome and alpha-methylacyl-CoA racemase deficiency (MIM 604489). Several studies revealed that the toxic activity of phytanic acid is mediated by multiple mitochondria...
Article
The α-ketoglutarate dehydrogenase complex (KGDHC) which catalyzes the conversion of α-ketoglutarate to succinyl-CoA and NADH in mitochondria, is known to generate O2·− in vitro. To find out if KGDHC contributes to neuronal reactive oxygen species (ROS) increase in situ, we investigated whether the specific inhibitors of cellular KGDHC, succinyl pho...
Article
The mitochondrial potential is an essential regulator in cellular physiology and detection of this parameter in living cells is still under discussion. Here we present a protocol which allows the use of rhodamine 123 as a probe for quantifying the mitochondrial potential. To avoid dequenching artefacts the detection area is limited to the area abov...
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Saturated very long chain fatty acids (VLCFAs; > or =C22:0) accumulate in X-linked adrenoleukodystrophy (X-ALD, OMIM 300100), a severe hereditary neurodegenerative disease, due to peroxisomal impairment. Previous studies analysed the development of X-ALD in humans and gene knockout animal models. However, the toxic effect of VLCFA leading to severe...
Article
With mixed cultures of hippocampal astrocytes and neurons, we investigated the influence of nucleotides on cytosolic Ca(2+) level, generation of reactive oxygen species (ROS), and mitochondrial potential. We employed ATP and four purine/pyrimidine derivates, which are P2Y receptor subtype-preferring agonists. Stimulation with ATP, a P2Y(1/2/4) rece...
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The beneficial or detrimental role of gap junction communication in the pathophysiology of brain injury is still controversial. We used co-cultures of hippocampal astrocytes and neurons, where we identified homocellular astrocyte-astrocyte and heterocellular astrocyte-neuron coupling by fluorescence recovery after photobleaching, which was decrease...
Article
Phytanic acid, a saturated fatty acid of 20-carbon-atoms with isoprenoic structure, is formed from the phytol-side chain of chlorophyll in ruminants. Degradation of phytanic acid is blocked in Refsum disease by several enzymatic defects of peroxisomal degradation of branched-chain fatty acids. Refsum disease is an inherited neurological disorder pr...
Article
Phytanic acid is a saturated branched-chain fatty acid, which is formed by bacterial degradation of chlorophyll in the intestinal tract of ruminants. The methyl group in beta-position prevents degradation of phytanic acid by the beta-oxidation pathway. Therefore, degradation of phytanic acid is initiated by alpha-oxidation in peroxisomes. The inher...
Article
Objectives: The disturbance of energy supply during ischemia is fatal for brain tissue. A characteristic feature is the massive increase in extracellular glutamate concentration which triggers subsequent cell death. Mitochondria play a central role in the induction of cell death due to generation of reactive oxygen species (ROS), release of apoptot...
Article
The saturated branched chain fatty acid, phytanic acid, a degradation product of chlorophyll, accumulates in Refsum disease, an inherited peroxisomal disorder with neurological clinical features. To elucidate the pathogenic mechanism, we investigated the influence of phytanic acid on cellular physiology of rat hippocampal astrocytes. Phytanic acid...
Article
Generation of reactive oxygen species (ROS) in brain tissue leads to neurodegeneration. The major source of ROS is the mitochondrial respiratory chain. We studied regulation of Ca2+ level, mitochondrial potential, and ROS generation in defined mixed hippocampal cell cultures exposed to glutamate (100 microM). Recordings were made from individually...
Article
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Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) accumulates at high levels throughout the body in the adult form of Refsum disease, a peroxisomal genetic disorder. However, it is still unclear why increased levels of phytanic acid have cytotoxic effects. In the present study, we examined the influence of non-esterified phytanic acid on energ...
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Cooperation between astrocytes and neurons is a unique interaction between two highly specialized cell types of the brain. Therefore, lack of nutrient supply during ischemia requires tight coordination of metabolism between astrocytes and neurons to keep the brain functions intact. To understand the impact of energy limitation on astrocytes, the fu...
Article
Intracellular ATP supply and ion homeostasis determine neuronal survival and degeneration after ischemic stroke. The present study provides a systematic investigation in organotypic hippocampal slice cultures of the influence of experimental ischemia, induced by oxygen-glucose-deprivation (OGD). The pathways controlling intracellular Na(+) and Ca(2...
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In animal models, brain ischemia causes changes in respiratory capacity, mitochondrial morphology, and cytochrome c release from mitochondria as well as a rise in cytosolic Ca2+ concentration. However, the causal relationship of the cellular processes leading to mitochondrial deterioration in brain has not yet been clarified. Here, by applying vari...
Article
The influence of cytosolic Ca(2+) load and of mitochondrial membrane potential change on mitochondrial morphology was investigated in cultured rat hippocampal astrocytes. The uncoupler FCCP, applied together with oligomycin, depolarized mitochondria rapidly but did not change their morphology. Depolarization was associated with a moderate cytosolic...
Article
The influence of physiological Ca2+-inducing stimuli and agents mimicking ischemic conditions on mitochondrial potential was studied in postnatal (P1) hippocampal astrocytes. Cytosolic Ca2+ loads with characteristic kinetics of rise and duration, detected by Fura-2, were provoked by extracellular Ca2+ influx, release from InsP3-sensitive intracellu...
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A decrease in glomerular heparan sulfate (HS) proteoglycan (PG), without apparent decrease in HSPG core protein expression, has been reported to occur in diabetic nephropathy (DN). In most studies however, agrin, the major HSPG core protein in the glomerular basement membrane, has not been studied. This prompted us to study the glomerular expressio...
Article
A major consequence of brain hypoxia and hypoglycemia, which induces the detrimental effects of stroke, is impaired ATP supply. However, it is not yet clear to which degree reduced cellular ATP production affects Ca(2+) homeostasis and Ca(2+) signaling of glia cells. Here we studied in cultured hippocampal astrocytes the influence of inhibition of...
Article
A major consequence of brain hypoxia and hypoglycemia, which induces the detrimental effects of stroke, is impaired ATP supply. However, it is not yet clear to which degree reduced cellular ATP production affects Ca2+ homeostasis and Ca2+ signaling of glia cells. Here we studied in cultured hippocampal astrocytes the influence of inhibition of cell...

Projects

Projects (9)
Project
Darstellung von Biotopen im Raum Bad Dürkheim
Project
Incidence and biology in Palatina
Project
Incidence and biology in Palatina