Showing papers by "University of Fribourg published in 2005"
TL;DR: This study shows that SA, JA, and ET play a primary role in the orchestration of the plant's defense response, but other regulatory mechanisms, such as pathway cross-talk or additional attacker-induced signals, eventually shape the highly complex attacker-specific defense response.
Abstract: Plant defenses against pathogens and insects are regulated differentially by cross-communicating signaling pathways in which salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) play key roles. To understand how plants integrate pathogen- and insect-induced signals into specific defense responses, we monitored the dynamics of SA, JA, and ET signaling in Arabidopsis after attack by a set of microbial pathogens and herbivorous insects with different modes of attack. Arabidopsis plants were exposed to a pathogenic leaf bacterium (Pseudomonas syringae pv. tomato), a pathogenic leaf fungus (Alternaria brassicicola), tissuechewing caterpillars (Pieris rapae), cell-content-feeding thrips (Frankliniella occidentalis), or phloem-feeding aphids (Myzus persicae). Monitoring the signal signature in each plant-attacker combination showed that the kinetics of SA, JA, and ET production varies greatly in both quantity and timing. Analysis of global gene expression profiles demonstrated that the signal signature characteristic of each Arabidopsis-attacker combination is orchestrated into a surprisingly complex set of transcriptional alterations in which, in all cases, stress-related genes are overrepresented. Comparison of the transcript profiles revealed that consistent changes induced by pathogens and insects with very different modes of attack can show considerable overlap. Of all consistent changes induced by A. brassicicola, Pieris rapae, and F. occidentalis, more than 50% also were induced consistently by P. syringae. Notably, although these four attackers all stimulated JA biosynthesis, the majority of the changes in JA-responsive gene expression were attacker specific. All together, our study shows that SA, JA, and ET play a primary role in the orchestration of the plant’s defense response, but other regulatory mechanisms, such as pathway cross-talk or additional attacker-induced signals, eventually shape the highly complex attacker-specific defense response.
944 citations
TL;DR: Recent research shows that abscisic acid can also be implicated in increasing the resistance of plants towards pathogens via its positive effect on callose deposition.
743 citations
01 Jan 2005
726 citations
TL;DR: In this review, the current understanding of food science is discussed, by considering established SCM methods as well as emerging techniques and theoretical approaches.
Abstract: Foods make up some of the most complex examples of soft condensed matter (SCM) with which we interact daily. Their complexity arises from several factors: the intricacy of components, the different aggregation states in which foods are encountered, and the multitude of relevant characteristic time and length scales. Because foodstuffs are governed by the rules of SCM physics but with all the complications related to real systems, the experimental and theoretical approaches of SCM physics have deepened our comprehension of their nature and behaviour, but many questions remain. In this review we discuss the current understanding of food science, by considering established SCM methods as well as emerging techniques and theoretical approaches. With their complexity, heterogeneity and multitude of states, foods provide SCM physics with a challenge of remarkable importance.
635 citations
TL;DR: In this article, the glutamate levels increase in the extracellular space of Per2Brdm1 mutant mice, which have a deletion in the PAS domain of the Per2 protein, leading to reduced uptake of glutamate by astrocytes.
Abstract: Period (Per) genes are involved in regulation of the circadian clock and are thought to modulate several brain functions. We demonstrate that Per2Brdm1 mutant mice, which have a deletion in the PAS domain of the Per2 protein, show alterations in the glutamatergic system. Lowered expression of the glutamate transporter Eaat1 is observed in these animals, leading to reduced uptake of glutamate by astrocytes. As a consequence, glutamate levels increase in the extracellular space of Per2Brdm1 mutant mouse brains. This is accompanied by increased alcohol intake in these animals. In humans, variations of the PER2 gene are associated with regulation of alcohol consumption. Acamprosate, a drug used to prevent craving and relapse in alcoholic patients is thought to act by dampening a hyper-glutamatergic state. This drug reduced augmented glutamate levels and normalized increased alcohol consumption in Per2Brdm1 mutant mice. Collectively, these data establish glutamate as a link between dysfunction of the circadian clock gene Per2 and enhanced alcohol intake.
554 citations
TL;DR: In this paper, structural differences in LiBH 4 before and after the melting reaction at approximately 550 K were investigated to clarify the experimental method for the confirmation of reversible dehydriding and rehydriding reactions.
421 citations
TL;DR: It is demonstrated that BABA-induced water stress tolerance is based on enhanced ABA accumulation resulting in accelerated stress gene expression and stomatal closure and a possibility to increase plant tolerance for these abiotic stresses through effective priming of the preexisting defense pathways without resorting to genetic alterations.
Abstract: Drought and salt stress tolerance of Arabidopsis (Arabidopsis thaliana) plants increased following treatment with the nonprotein amino acid β-aminobutyric acid (BABA), known as an inducer of resistance against infection of plants by numerous pathogens BABA-pretreated plants showed earlier and higher expression of the salicylic acid-dependent PR-1 and PR-5 and the abscisic acid (ABA)-dependent RAB-18 and RD-29A genes following salt and drought stress However, non-expressor of pathogenesis-related genes 1 and constitutive expressor of pathogenesis-related genes 1 mutants as well as transgenic NahG plants, all affected in the salicylic acid signal transduction pathway, still showed increased salt and drought tolerance after BABA treatment On the contrary, the ABA deficient 1 and ABA insensitive 4 mutants, both impaired in the ABA-signaling pathway, could not be protected by BABA application Our data demonstrate that BABA-induced water stress tolerance is based on enhanced ABA accumulation resulting in accelerated stress gene expression and stomatal closure Here, we show a possibility to increase plant tolerance for these abiotic stresses through effective priming of the preexisting defense pathways without resorting to genetic alterations
412 citations
TL;DR: It is shown that enhanced passive Ca2+ transport in the proximal tubule rather than active Ca2 + transport in distal convolution explains thiazide-induced hypocalciuria, and that Trpm6 downregulation may represent a general mechanism involved in the pathogenesis of hypomagnesemia accompanying NCC inhibition or inactivation.
Abstract: Thiazide diuretics enhance renal Na+ excretion by blocking the Na+-Cl- cotransporter (NCC), and mutations in NCC result in Gitelman syndrome. The mechanisms underlying the accompanying hypocalciuria and hypomagnesemia remain debated. Here, we show that enhanced passive Ca2+ transport in the proximal tubule rather than active Ca2+ transport in distal convolution explains thiazide-induced hypocalciuria. First, micropuncture experiments in mice demonstrated increased reabsorption of Na+ and Ca2+ in the proximal tubule during chronic hydrochlorothiazide (HCTZ) treatment, whereas Ca2+ reabsorption in distal convolution appeared unaffected. Second, HCTZ administration still induced hypocalciuria in transient receptor potential channel subfamily V, member 5-knockout (Trpv5-knockout) mice, in which active distal Ca2+ reabsorption is abolished due to inactivation of the epithelial Ca2+ channel Trpv5. Third, HCTZ upregulated the Na+/H+ exchanger, responsible for the majority of Na+ and, consequently, Ca2+ reabsorption in the proximal tubule, while the expression of proteins involved in active Ca2+ transport was unaltered. Fourth, experiments addressing the time-dependent effect of a single dose of HCTZ showed that the development of hypocalciuria parallels a compensatory increase in Na+ reabsorption secondary to an initial natriuresis. Hypomagnesemia developed during chronic HCTZ administration and in NCC-knockout mice, an animal model of Gitelman syndrome, accompanied by downregulation of the epithelial Mg2+ channel transient receptor potential channel subfamily M, member 6 (Trpm6). Thus, Trpm6 downregulation may represent a general mechanism involved in the pathogenesis of hypomagnesemia accompanying NCC inhibition or inactivation.
407 citations
TL;DR: The data presented here introduce three novel regulatory genes involved in priming for different defense responses in plant resistance, which were tested for BABA-IR against the bacterium Pseudomonas syringae pv tomato, the oomycete Hyaloperonospora parasitica, andBABA-induced tolerance to salt.
Abstract: Plants treated with the nonprotein amino acid β-aminobutyric acid (BABA) develop an enhanced capacity to resist biotic and abiotic stresses. This BABA-induced resistance (BABA-IR) is associated with an augmented capacity to express basal defense responses, a phenomenon known as priming. Based on the observation that high amounts of BABA induce sterility in Arabidopsis thaliana, a mutagenesis screen was performed to select mutants impaired in BABA-induced sterility (ibs). Here, we report the isolation and subsequent characterization of three T-DNA–tagged ibs mutants. Mutant ibs1 is affected in a cyclin-dependent kinase–like protein, and ibs2 is defective in AtSAC1b encoding a polyphosphoinositide phosphatase. Mutant ibs3 is affected in the regulation of the ABA1 gene encoding the abscisic acid (ABA) biosynthetic enzyme zeaxanthin epoxidase. To elucidate the function of the three IBS genes in plant resistance, the mutants were tested for BABA-IR against the bacterium Pseudomonas syringae pv tomato, the oomycete Hyaloperonospora parasitica, and BABA-induced tolerance to salt. All three ibs mutants were compromised in BABA-IR against H. parasitica, although to a different extent. Whereas ibs1 was reduced in priming for salicylate (SA)-dependent trailing necrosis, mutants ibs2 and ibs3 were affected in the priming for callose deposition. Only ibs1 failed to express BABA-IR against P. syringae, which coincided with a defect in priming for SA-inducible PR-1 gene expression. By contrast, ibs2 and ibs3 showed reduced BABA-induced tolerance to salt, which correlated with an affected priming for ABA-inducible gene expression. For all three ibs alleles, the defects in BABA-induced sterility and BABA-induced protection against P. syringae, H. parasitica, and salt could be confirmed in independent mutants. The data presented here introduce three novel regulatory genes involved in priming for different defense responses.
395 citations
TL;DR: It is shown that flies induced to form long-term memory become more susceptible to extreme stress (such as desiccation), in contrast, induction of anesthesia-resistant memory had no detectable effect on Desiccation resistance.
Abstract: Two distinct forms of consolidated associative memory are known in Drosophila: long-term memory and so-called anesthesia-resistant memory. Long-term memory is more stable, but unlike anesthesia-resistant memory, its formation requires protein synthesis. We show that flies induced to form long-term memory become more susceptible to extreme stress (such as desiccation). In contrast, induction of anesthesia-resistant memory had no detectable effect on desiccation resistance. This finding may help to explain why evolution has maintained anesthesia-resistant memory as another form of consolidated memory, distinct from long-term memory.
252 citations
TL;DR: In this paper, the authors provide an overview of the intricacies of mountain climates, particularly as they pertain to the European Alps, and some of the physical mechanisms that may be responsible for those changes.
Abstract: This contribution provides an overview of the intricacies of mountain climates, particularly as they pertain to the European Alps. Examples will be given of issues that are related to climatic change as observed in the Alps during the course of the 20th century, and some of the physical mechanisms that may be responsible for those changes. The discussion will then focus on the problems related to assessing climatic change in regions of complex topography, the potential shifts in climate during the 21st century that the alpine region may be subjected to, and the associated climate-generated impacts on mountain environments.
TL;DR: It is proposed that bec-1 represents a link between autophagy and apoptosis, thus supporting the view that the two processes act in concerted manner in the cell death machinery.
TL;DR: The DEAR (DAPhiNE exotic atom research) experiment measured the energy of x rays emitted in the transitions to the ground state of Kaonic hydrogen and the pattern of the kaonic hydrogen K-series lines, K(alpha), K(beta), and K(gamma), was disentangled for the first time.
Abstract: The DEAR (DA$\ensuremath{\Phi}$NE exotic atom research) experiment measured the energy of x rays emitted in the transitions to the ground state of kaonic hydrogen. The measured values for the shift $ϵ$ and the width $\ensuremath{\Gamma}$ of the 1$s$ state due to the ${K}^{\ensuremath{-}}p$ strong interaction are ${ϵ}_{1s}=\ensuremath{-}193\ifmmode\pm\else\textpm\fi{}37$ (stat) $\ifmmode\pm\else\textpm\fi{}6$ (syst) eV and ${\ensuremath{\Gamma}}_{1s}=249\ifmmode\pm\else\textpm\fi{}111$ (stat) $\ifmmode\pm\else\textpm\fi{}30$ (syst) eV, the most precise values yet obtained. The pattern of the kaonic hydrogen $K$-series lines, ${K}_{\ensuremath{\alpha}}$, ${K}_{\ensuremath{\beta}}$, and ${K}_{\ensuremath{\gamma}}$, was disentangled for the first time.
TL;DR: In this paper, the authors used dendrogeomorphology to investigate spatial and temporal variations of rockfall activity in a protection forest and reconstructed 741 growth disturbances (GD) during the last four centuries.
TL;DR: This paper introduces scientists to chronobiology by explaining the basic terminology used within the field and aims to assist in designing, carrying out, and evaluating wheel-running experiments with rodents, particularly mice.
Abstract: Most behavioral experiments within circadian research are based on the analysis of locomotor activity. This paper introduces scientists to chronobiology by explaining the basic terminology used within the field. Furthermore, it aims to assist in designing, carrying out, and evaluating wheel-running experiments with rodents, particularly mice. Since light is an easily applicable stimulus that provokes strong effects on clock phase, the paper focuses on the application of different lighting conditions.
TL;DR: It is shown that expression of the slow CBP parvalbumin (PV) in cerebellar interneurons is cell specific and developmentally regulated, leading to characteristic changes in presynaptic Ca2+ dynamics (Cai).
Abstract: Certain interneurons contain large concentrations of specific Ca2+-binding proteins (CBPs), but consequences on presynaptic Ca2+ signaling are poorly understood. Here we show that expression of the slow CBP parvalbumin (PV) in cerebellar interneurons is cell specific and developmentally regulated, leading to characteristic changes in presynaptic Ca2+ dynamics (Ca(i)). Using whole-cell recording and fluorescence imaging, we studied action potential-evoked Ca(i) transients in axons of GABA-releasing interneurons from mouse cerebellum. At early developmental stages [postnatal days 10-12 (P10-P12)], decay kinetics were significantly faster for basket cells than for stellate cells, whereas at P19-P21 both interneurons displayed fast decay kinetics. Biochemical and immunocytochemical analysis showed parallel changes in the expression levels and cellular distribution of PV. By comparing wild-type and PV(-/-) mice, PV was shown to accelerate the initial decay of action potential-evoked Ca(i) signals in single varicosities and to introduce an additional slow phase that summates during bursts of action potentials. The fast initial Ca(i) decay accounts for a previous report that PV elimination favors synaptic facilitation. The slow decay component is responsible for a pronounced, PV-dependent, delayed transmitter release that we describe here at interneuron-interneuron synapses after presynaptic bursts of action potentials. Numerical simulations account for the effect of PV on Ca(i) kinetics, allow estimates for the axonal PV concentration (approximately 150 microm), and predict the time course of volume-averaged Ca(i) in the absence of exogenous buffer. Overall, PV arises as a major contributor to presynaptic Ca(i) signals and synaptic integration in the cerebellar cortex.
TL;DR: It is suggested that time spent with friends affords a survival advantage among older adults, above and beyond the effects of other leisure activities.
Abstract: This study tested the hypothesis that time spent on social activities (i.e., in direct interaction with others) and time spent in social contexts (i.e., while others are present) is associated with survival in persons aged 70 and older. An observational study with mortality follow-ups was carried out in the former West Berlin, Germany (Berlin Aging Study). The sample was stratified by age and sex, and consisted of 473 persons aged 70 to 103 years. Social activity and social context measures were assessed in 1990–1993 by structured interviews in the participants’ homes. Cox regression was used to model survival from time of interview. The main outcome measure was survival on 1 August 2003. Time spent on social activities was revealed as a predictor of survival only in analyses that did not control for confounding factors. In contrast, time spent in context “with friends” was significantly related to increased survival (relative risk=0.76, 95% confidence interval 0.59 to 0.99) even after several confounding factors were controlled for. This study suggests that time spent with friends affords a survival advantage among older adults, above and beyond the effects of other leisure activities. Future research on social participation and survival may benefit from an examination of the interaction between activity content and social context.
TL;DR: It is shown that Gelation results when interconnected colloid-rich regions solidify when these regions undergo a glass transition, leading to dynamic arrest of the spinodal decomposition.
Abstract: Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich and colloid-poor regions. Gelation results when interconnected colloid-rich regions solidify. We show that this occurs when these regions undergo a glass transition, leading to dynamic arrest of the spinodal decomposition. The characteristic length scale of the gel decreases with increasing quench depth, and the nonergodicity parameter exhibits a pronounced dependence on scattering vector. Mode coupling theory gives a good description of the dynamics, provided we use the full static structure as input.
TL;DR: Cluster analysis of ESTs revealed major differences between the expressed gene content of mycelial and spore-related stages, and affinities between some growth conditions.
Abstract: To overview the gene content of the important pathogen Phytophthora infestans, large-scale cDNA and genomic sequencing was performed. A set of 75,757 high-quality expressed sequence tags (ESTs) from P. infestans was obtained from 20 cDNA libraries representing a broad range of growth conditions, stress responses, and developmental stages. These included libraries from P. infestans-potato and -tomato interactions, from which 963 pathogen ESTs were identified. To complement the ESTs, onefold coveragethe P. infestans genome was obtained and regions of coding potential identified. A unigene set of 18,256 sequences was derived from the EST and genomic data and characterized for potential functions, stage-specific patterns of expression, and codon bias. Cluster analysis of ESTs revealed major differences between the expressed gene content of mycelial and spore-related stages, and affinities between some growth conditions. Comparisons with databases of fungal pathogenicity genes revealed conserved elements of pa...
TL;DR: The Drosophila larva is proposed as an "elementary" olfactory model system because its basic design is similar to the adult one and its ORNs and projection neurons lack cellular redundancy and do not exhibit any convergent or divergent connectivity.
Journal Article•
TL;DR: In this article, the connectivity of the larval olfactory circuit was analyzed by genetically labeling single neurons with FLP-out and MARCM techniques, and it was shown that each of the 21 odorant-receptor neurons (ORNs) is unique and projects to one of 21 morphologically identifiable antennal-lobe glomeruli.
TL;DR: Lipase double-mutant cells in which the third lipase is expressed from the inducible GAL1 promoter have greatly reduced steady-state levels of steryl esters, indicating that overexpression of any of the three lipases is sufficient for steryl Ester mobilization in vivo.
Abstract: Sterol homeostasis in eukaryotic cells relies on the reciprocal interconversion of free sterols and steryl esters. The formation of steryl esters is well characterized, but the mechanisms that control steryl ester mobilization upon cellular demand are less well understood. We have identified a family of three lipases of Saccharomyces cerevisiae that are required for efficient steryl ester mobilization. These lipases, encoded by YLL012/ YEH1, YLR020/YEH2, and TGL1, are paralogues of the mammalian acid lipase family, which is composed of the lysosomal acid lipase, the gastric lipase, and four novel as yet uncharacterized human open reading frames. Lipase triple-mutant yeast cells are completely blocked in steryl ester hydrolysis but do not affect the mobilization of triacylglycerols, indicating that the three lipases are required for steryl ester mobilization in vivo. Lipase single mutants mobilize steryl esters to various degrees, indicating partial functional redundancy of the three gene products. Lipase double-mutant cells in which the third lipase is expressed from the inducible GAL1 promoter have greatly reduced steady-state levels of steryl esters, indicating that overexpression of any of the three lipases is sufficient for steryl ester mobilization in vivo. The three yeast enzymes constitute a novel class of membrane-anchored lipases that differ in topology and subcellular localization.
TL;DR: This work describes how to optimize TRC measurements and how to detect and avoid possible artifacts, and proposes and demonstrates a method to correct for the noise contribution, based on a N--> infinity extrapolation scheme.
Abstract: Time resolved correlation (TRC) is a recently introduced light scattering technique that allows one to detect and quantify dynamic heterogeneities. The technique is based on the analysis of the temporal evolution of the speckle pattern generated by the light scattered by a sample, which is quantified by ${c}_{I}(t,\ensuremath{\tau})$, the degree of correlation between speckle images recorded at time $t$ and $t+\ensuremath{\tau}$. Heterogeneous dynamics results in significant fluctuations of ${c}_{I}(t,\ensuremath{\tau})$ with time $t$. We describe how to optimize TRC measurements and how to detect and avoid possible artifacts. The statistical properties of the fluctuations of ${c}_{I}$ are analyzed by studying their variance, probability distribution function, and time autocorrelation function. We show that these quantities are affected by a noise contribution due to the finite number $N$ of detected speckles. We propose and demonstrate a method to correct for the noise contribution, based on a $N\ensuremath{\rightarrow}\ensuremath{\infty}$ extrapolation scheme. Examples from both homogeneous and heterogeneous dynamics are provided. Connections with recent numerical and analytical works on heterogeneous glassy dynamics are briefly discussed.
TL;DR: Mature adipocytes release hydrosoluble protein growth factor(s) with a molecular mass >100 kDa for SMCs, which stimulates SMC proliferation, which is enhanced in aged WKY and in high-fat, diet-induced obesity but not in leptin receptor-deficient obese Zucker rats.
Abstract: Adipocytes and perivascular adipose tissue are emerging as regulators of vascular function. The effects of adipocytes and perivascular adipose tissue on human smooth muscle cell (SMC) proliferation were investigated. Conditioned medium was prepared from cultured premature and differentiated 3T3-L1 adipocytes and from periaortic adipose tissue from young (3 mo) and old (24 mo) Wistar-Kyoto (WKY) rats, lean and obese Zucker rats (3 mo), and WKY rats fed normal chow or a high-fat diet for 3 mo. Conditioned medium from differentiated (but not premature) adipocytes stimulated SMC proliferation, which was abolished by charcoal and proteinase K treatment but was resistant to heat, trypsin, or phospholipase B (to hydrolyze lysophosphatidic acid). Further experiments demonstrated that the growth factor(s) are hydrosoluble and present in the fraction of molecular mass >100 kDa. Moreover, conditioned medium from periaortic adipose tissue stimulated SMC proliferation, which was significantly enhanced in aged rats and in rats fed a high-fat diet but not in obese Zucker rats deficient in functional leptin receptors. In conclusion, mature adipocytes release hydrosoluble protein growth factor(s) with a molecular mass >100 kDa for SMCs. Perivascular adipose tissue stimulates SMC proliferation, which is enhanced in aged WKY and in high-fat, diet-induced obesity but not in leptin receptor-deficient obese Zucker rats. These adipocyte-derived growth factor(s) and the effect of perivascular adipose tissue may be involved in vascular disease associated with aging and obesity.
TL;DR: The activity of single striatal neurons in macaques that were presented with different combinations of two rewards found in nearly half of the investigated neurons that the processing for one reward shifted, relative to the other rewards that were available in a given trial block.
Abstract: Rewards are often not only valued according to their physical characteristics but also relative to other available rewards. The striatum (caudate nucleus, putamen, ventral striatum including nucleus accumbens) is involved in the organization of movement and the processing of reward information. We studied the activity of single striatal neurons in macaques that were presented with different combinations of two rewards. We found in nearly half of the investigated neurons that the processing for one reward shifted, relative to the other rewards that were available in a given trial block. The relative reward processing concerned all forms of striatal activity related to reward-predicting visual stimuli, arm movements and reception of rewards. The observed changes may provide a neural basis for the known shifts in valuation of rewarding outcomes relative to known references.
TL;DR: In this paper, the authors presented twenty paleogeographic maps for Middle Eocene to Late Pliocene times according to the stratigraphical data given in the companion paper by Berger et al. this volume.
Abstract: Twenty paleogeographic maps are presented for Middle Eocene (Lutetian) to Late Pliocene times according to the stratigraphical data given in the companion paper by Berger et al. this volume. Following a first lacustrine-continental sedimentation during the Middle Eocene, two and locally three Rupelian transgressive events were identified with the first corresponding with the Early Rupelian Middle Pechelbronn beds and the second and third with the Late Rupelian ≪ Serie Grise ≫ (Fischschiefer and equivalents). During the Early Rupelian (Middle Pechelbronn beds), a connection between North Sea and URG is clearly demonstrated, but a general connection between North Sea, URG and Paratethys, via the Alpine sea, is proposed, but not proved, during the late Rupelian. Whereas in the southern URG, a major hiatus spans Early Aquitanian to Pliocene times, Early and Middle Miocene marine, brackish and freshwater facies occur in the northern URG and in the Molasse Basin (OMM, OSM); however, no marine connections between these basins could be demonstrated during this time. After the deposition of the molasse series, a very complex drainage pattern developed during the Late Miocene and Pliocene, with a clear connection to the Bresse Graben during the Piacenzian (Sundgau gravels). During the Late Miocene, Pliocene and Quaternary sedimentation persisted in the northern URG with hardly any interruptions. The present drainage pattern of the Rhine river (from Alpine area to the lower Rhine Embayment) was not established before the Early Pleistocene.
TL;DR: In this paper, the past debris-flow activity in the Ritigraben torrent (Mattertal, Valais) with dendrogeomorphological methods was reconstructed, going back to the year 1605.
Abstract: Three major rainfall events have caused considerable damage in the Valais region (Swiss Alps) since 1987. Substantial debris flows originating from periglacial environments were recorded during the August 1987 and September 1993 rainfall events, whereas no debris flows occurred in October 2000. This paper aims at putting these large-area events and the apparent increase in debris-flow frequency into a wider context by reconstructing the past debris-flow activity in the Ritigraben torrent (Mattertal, Valais) with dendrogeomorphological methods. Tree-ring analysis allowed the reconstruction of 53 events, going back to the year 1605. Previously, only 10 debris flows had been known for the torrent, and these were limited to the period between 1922 and 2002. Results further show that the apparently above-average concentration of events since 1987 was mainly caused by insufficient and short archival data. In fact, debris flows occurred even more frequently in the nineteenth century than they do today. ...
TL;DR: The results show that generalist herbivores could potentially play a role in the evolution and maintenance of the diversity of PAs and indications for synergistic deterrent effects of P as in PA mixtures are found.
Abstract: The evolution of the diversity in plant secondary compounds is often thought to be driven by insect herbivores, although there is little empirical evidence for this assumption. To investigate whether generalist insect herbivores could play a role in the evolution of the diversity of related compounds, we examined if (1) related compounds differ in their effects on generalists, (2) there is a synergistic effect among compounds, and (3) effects of related compounds differed among insect species. The effects of pyrrolizidine alkaloids (PAs) were tested on five generalist insect herbivore species of several genera using artificial diets or neutral substrates to which PAs were added. We found evidence that structurally related PAs differed in their effects to the thrips Frankliniella occidentalis, the aphid Myzus persicae, and the locust Locusta migratoria. The individual PAs had no effect on Spodoptera exigua and Mamestra brassicae caterpillars. For S. exigua, we found indications for synergistic deterrent effects of PAs in PA mixtures. The relative effects of PAs differed between insect species. The PA senkirkine had the strongest effect on the thrips, but had no effect at all on the aphids. Our results show that generalist herbivores could potentially play a role in the evolution and maintenance of the diversity of PAs.
TL;DR: In this paper, the authors reported observations made recently in the western Swiss Alps in several accumulations of coarse sediments (talus slopes, relict or inactive rock glaciers) located at higher elevations (2200-2800 m a.s.l.) within the belt of discontinuous permafrost or close to its lower limit.
Abstract: The winter ascending circulation of air throughout an accumulation of coarse slope sediments (the so-called chimney effect) facilitates the cooling of the ground and even the occurrence of permafrost in the lower part of a deposit. Simultaneously, any freezing is unlikely to occur in the upper part. To date, the chimney effect has been reported mainly for cold and sometimes perennially frozen scree slopes situated at low elevations, far below the regional limit of the discontinuous mountain permafrost. This article reports observations made recently in the western Swiss Alps in several accumulations of coarse sediments (talus slopes, relict or inactive rock glaciers) located at higher elevations (2200–2800 m a.s.l.) within the belt of discontinuous permafrost or close to its lower limit. These observations show that a chimney effect may also occur in debris accumulations situated at ‘usual’ mountain permafrost elevation. This gives rise to multiple questions, in particular about the impact of the chimney ...
TL;DR: The usefulness of FSP1/S100A4 as a tool for detection of (myo)fibroblasts in inflamed kidneys and of EMT in vivo is put into question because in the given rat model the consistent co-expression of αSMA and 5′NT suggests that myofibroblast originate from resident peritubular fibroblast.
Abstract: Fibrosis is considered as a central factor in the loss of renal function in chronic kidney diseases. The origin of fibroblasts and myofibroblasts that accumulate in the interstitium of the diseased kidney is still a matter of debate. It has been shown that accumulation of myofibroblasts in inflamed and fibrotic kidneys is associated with upregulation of fibroblast-specific protein 1 (FSP1, S100A4), not only in the renal interstitium but also in the injured renal epithelia. The tubular expression of FSP1 has been taken as evidence of myofibroblast formation by epithelial–mesenchymal transition (EMT). The identity of FSP1/S100A4 cells has not been defined in detail. We originally intended to use FSP1/S100A4 as a marker of putative EMT in a model of distal tubular injury. However, since the immunoreactivity of FSP1 did not seem to fit with the distribution and shape of fibroblasts or myofibroblasts, we undertook the characterization of FSP1/S100A4-expressing cells in the interstitium of rodent kidneys. We performed immunolabeling for FSP1/S100A4 on thin cryostat sections of perfusion-fixed rat and mouse kidneys with peritubular inflammation, induced by thiazides and glomerulonephritis, respectively, in combination with ecto-5′-nucleotidase (5′NT), recognizing local cortical peritubular fibroblasts, with CD45, MHC class II, CD3, CD4 and Thy 1, recognizing mononuclear cells, with alpha smooth muscle actin (αSMA), as marker for myofibroblasts, and vimentin for intracellular intermediate filaments in cells of mesenchymal origin. In the healthy interstitium of rodents the rare FSP1/S100A4+ cells consistently co-expressed CD45 or lymphocyte surface molecules. Around the injured distal tubules of rats treated for 3–4 days with thiazides, FSP1+/S100A4+, 5′NT+, αSMA+, CD45+ and MHC class II+ cells accumulated. FSP1+/S100A4+ cells consistently co-expressed CD45. In the inflamed regions, αSMA was co-expressed by 5′NT+ cells. In glomerulonephritic mice, FSP1+/S100A4+ cells co-expressed Thy 1, CD4 or CD3. Thus, in the inflamed interstitium around distal tubules of rats and of glomerulonephritic mice, the majority of FSP1+ cells express markers of mononuclear cells. Consequently, the usefulness of FSP1/S100A4 as a tool for detection of (myo)fibroblasts in inflamed kidneys and of EMT in vivo is put into question. In the given rat model the consistent co-expression of αSMA and 5′NT suggests that myofibroblasts originate from resident peritubular fibroblasts.