2017 ( 10 )

2016 ( 24 )

2015 ( 861 )

2014 ( 991 )


匹配条件: “ Andreas Zimmer” ,找到相关结果约10950条。
Loss of CB1 receptors leads to differential age-related changes in reward-driven learning and memory
Onder Albayram,Andreas Zimmer
Frontiers in Aging Neuroscience , 2012, DOI: 10.3389/fnagi.2012.00034
Abstract: Previous studies have shown that cannabinoid 1 (CB1) receptor signaling dissociates between reward-associated and aversive memories. The influence of CB1 receptors on the aversion-driven spatial learning in the Morris water maze test is strongly age-dependent: mice with genetic deletion of CB1 receptors (Cnr1?/?) show superior learning when young but inferior learning when old compared to age-matched wild-type mice. Whether the reward-driven spatial learning is influenced in the same way by CB1 receptor signaling as the aversion-driven learning remains unclear. Thus, we examined the performance of Cn1?/? and their wild-type littermates at ages of 2-, 5-, and 12-months-old in the eight-arm radial maze test—a reward-motivated model of spatial learning. Interestingly, 2-months-old Cnr1?/? mice had a superior learning ability to wild-type mice. At the age of 5-months, Cnr1?/? mice showed the same performance as the wild-type littermates. However, 12-months-old Cnr1?/? mice showed significantly impaired performances in each parameter of the test. Accordingly, this study provides compelling support for our previous result that genetic deletion of CB1 receptor leads to early onset of age-related memory decline, similarly affecting both reward and aversion-driven learning.
THC Prevents MDMA Neurotoxicity in Mice
Clara Touri?o,Andreas Zimmer,Olga Valverde
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009143
Abstract: The majority of MDMA (ecstasy) recreational users also consume cannabis. Despite the rewarding effects that both drugs have, they induce several opposite pharmacological responses. MDMA causes hyperthermia, oxidative stress and neuronal damage, especially at warm ambient temperature. However, THC, the main psychoactive compound of cannabis, produces hypothermic, anti-inflammatory and antioxidant effects. Therefore, THC may have a neuroprotective effect against MDMA-induced neurotoxicity. Mice receiving a neurotoxic regimen of MDMA (20 mg/kg ×4) were pretreated with THC (3 mg/kg ×4) at room (21°C) and at warm (26°C) temperature, and body temperature, striatal glial activation and DA terminal loss were assessed. To find out the mechanisms by which THC may prevent MDMA hyperthermia and neurotoxicity, the same procedure was carried out in animals pretreated with the CB1 receptor antagonist AM251 and the CB2 receptor antagonist AM630, as well as in CB1, CB2 and CB1/CB2 deficient mice. THC prevented MDMA-induced-hyperthermia and glial activation in animals housed at both room and warm temperature. Surprisingly, MDMA-induced DA terminal loss was only observed in animals housed at warm but not at room temperature, and this neurotoxic effect was reversed by THC administration. However, THC did not prevent MDMA-induced hyperthermia, glial activation, and DA terminal loss in animals treated with the CB1 receptor antagonist AM251, neither in CB1 and CB1/CB2 knockout mice. On the other hand, THC prevented MDMA-induced hyperthermia and DA terminal loss, but only partially suppressed glial activation in animals treated with the CB2 cannabinoid antagonist and in CB2 knockout animals. Our results indicate that THC protects against MDMA neurotoxicity, and suggest that these neuroprotective actions are primarily mediated by the reduction of hyperthermia through the activation of CB1 receptor, although CB2 receptors may also contribute to attenuate neuroinflammation in this process.
Wind-Driven Dynamics of Beach-Cast Wrack in a Tide-Free System  [PDF]
Sven Hammann, Martin Zimmer
Open Journal of Marine Science (OJMS) , 2014, DOI: 10.4236/ojms.2014.42009

Whereas wrack dynamics on tidally influenced beaches have been studied to some detail, essentially nothing is known about how drift lines in tide-free coastal systems vary in space and time. We provide evidence for high spatial and temporal dynamics of beach-cast wrack on a sand beach in the Western Baltic Sea. Over the course of one year, the amount of weekly deposited macrophyte wrack fluctuated from zero to 3000 g·m-1 shoreline. Wrack mostly accumulated just above the waterline. Part of the beach-cast wrack is frequently re-suspended into coastal water upon extreme high water level events, or wrack patches are translocated landwards by wind-driven changes in water level or along the shoreline by winds. Consequently, the deposited wrack does accumulate, but a steady-state of ca 400 g·m-1 builds up within 2 - 3 weeks. Eelgrass wrack buried in sand decomposed almost twice as fast as on top of the sand or re-suspended in water. Fragmentation of leaves promoted decomposition only when wrack remained on the sand surface. The spatial and temporal distribution of this valuable source of organic matter is unpredictable and depends on wind and wind-driven waves.

Large impact of the apoplast on somatic embryogenesis in Cyclamen persicum offers possibilities for improved developmental control in vitro
Claudia Hoenemann, Sandra Richardt, Katja Krüger, Andreas D Zimmer, Annette Hohe, Stefan A Rensing
BMC Plant Biology , 2010, DOI: 10.1186/1471-2229-10-77
Abstract: The analysis was based on a cDNA microarray representing 1,216 transcripts and was exemplarily validated by realtime PCR. For this purpose relative transcript abundances of homologues of a putative receptor kinase, two different glutathione S-transferases (GST), a xyloglucan endotransglycosylase (XET) and a peroxidase (POX) were quantitatively measured by realtime PCR for three different comparisons. In total, 417 genes were found to be differentially expressed. Gene Ontology annotation revealed that transcripts coding for enzymes that are active in the extracellular compartment (apoplast) were significantly overrepresented in several comparisons. The expression profiling results are underpinned by thorough histological analyses of somatic and zygotic embryos.The putative underlying physiological processes are discussed and hypotheses on improvement of the protocol for in vitro somatic embryogenesis in Cyclamen persicum are deduced. A set of physiological markers is proposed for efficient molecular control of the process of somatic embryogenesis in C. persicum. The general suitability of expression profiling for the development and improvement of micropropagation methods is discussed.Plant micropropagation on a commercial scale has developed since the 1960s and gained high impact during the last centuries for clonal mass propagation especially of ornamental crops [1,2]. The method with the potentially highest multiplication rate is regeneration via somatic embryogenesis (s.e.), which was initially described in 1958 for Daucus carota [3,4]. Since then, somatic embryogenesis systems have been developed for a multitude of plant species, but despite the large number of published protocols, only very few systems are actually used in commercial plant propagation. This can be put down to the fact that many protocols are inadequately reproducible, a differing fraction of the embryos shows developmental aberrations and non-embryogenic callus frequently arises during the use
Val103Ile polymorphism of the melanocortin-4 receptor gene (MC4R) in cancer cachexia
Susanne Knoll, Sabiene Zimmer, Anke Hinney, André Scherag, Andreas Neubauer, Johannes Hebebrand
BMC Cancer , 2008, DOI: 10.1186/1471-2407-8-85
Abstract: BMI (body mass index in kg/m2) of 509 patients (295 males) with malignant neoplasms was determined; additionally patients were asked about premorbid/pretherapeutical changes of appetite and weight loss. Cachexia was defined as a weight loss of at least 5% prior to initiation of therapy; to fulfil this criterion this weight loss had to occur independently of other plausible reasons; in single cases weight loss was the initial reason for seeing a physician. The average age in years (± SD) was 59.0 ± 14.5 (males: 58.8 ± 14.0, females 59.2 ± 14.0). Blood samples were taken for genotyping of the Val103Ile by PCR- RFLP.Most of the patients suffered from lymphoma, leukaemia and gastrointestinal tumours. 107 of the patients (21%) fulfilled our criteria for cancer cachexia. We did not detect association between the Val103Ile polymorphism and cancer cachexia. However, if we exploratively excluded the patients with early leucaemic stages, we detected a trend towards the opposite effect (p < 0.05); heterozygotes for the 103Ile-allele developed cancer cachexia less frequently in comparison to the rest of the study group. Changes of appetite were not associated with the 103Ile-allele carrier status (p > 0.39).Heterozygotes for the 103Ile-allele are not more prone to develop cancer cachexia than patients without this allele; possibly, Ile103 carriers might be more resistant to cancer cachexia in patients with solid tumors. Further studies of the melanocortinergic system in cachexia of patients with solid tumors are warranted.The cachexia syndrome represents a complex metabolic state accompanied by muscle wasting and a loss of body fat, hence quality of life is deteriorated and the prognosis of the patients who suffer from it is reduced [1,2]. Reports mostly vary in the amount of weight loss (5–10%) and the time span (6–12 months) in which the weight loss occurs [3-7]. Up to one-half of untreated cancer patients is expected to lose weight while about one third is expected to lose m
SNAI1-Mediated Epithelial-Mesenchymal Transition Confers Chemoresistance and Cellular Plasticity by Regulating Genes Involved in Cell Death and Stem Cell Maintenance
Soyoung Lim, Astrid Becker, Andreas Zimmer, Jianrong Lu, Reinhard Buettner, Jutta Kirfel
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0066558
Abstract: Tumor cells at the tumor margin lose epithelial properties and acquire features of mesenchymal cells, a process called epithelial-to-mesenchymal transition (EMT). Recently, features of EMT were shown to be linked to cells with tumor-founding capability, so-called cancer stem cells (CSCs). Inducers of the EMT include several transcription factors, such as Snail (SNAI1) and Slug (SNAI2), as well as the secreted transforming growth factor (TGF?). In the present study, we found that EMT induction in MCF10A cells by stably expressing SNAI1 contributed to drug resistance and acquisition of stem/progenitor-like character as shown by increased cell population for surface marker CD44+/CD24? and mammosphere forming capacity. Using a microarray approach, we demonstrate that SNAI1 overexpression results in a dramatic change in signaling pathways involved in the regulation of cell death and stem cell maintenance. We showed that NF-κB/MAPK signaling pathways are highly activated in MCF10A-SNAI1 cells by IL1? stimulation, leading to the robust induction in IL6 and IL8. Furthermore, MCF10A-SNAI1 cells showed enhanced TCF/?-catenin activity responding to the exogenous Wnt3a treatment. However, EMT-induced stem/progenitor cell activation process is tightly regulated in non-transformed MCF10A cells, as WNT5A and TGFB2 are strongly upregulated in MCF10A-SNAI1 cells antagonizing canonical Wnt pathway. In summary, our data provide new molecular findings how EMT contributes to the enhanced chemoresistance and the acquisition of stem/progenitor-like character by regulating signaling pathways.
Identification and characterization of NAGNAG alternative splicing in the moss Physcomitrella patens
Rileen Sinha, Andreas D Zimmer, Kathrin Bolte, Daniel Lang, Ralf Reski, Matthias Platzer, Stefan A Rensing, Rolf Backofen
BMC Plant Biology , 2010, DOI: 10.1186/1471-2229-10-76
Abstract: Using Sanger data, we found 295 alternatively used NAGNAG acceptors in P. patens. Using 31 features and training and test datasets of constitutive and alternative NAGNAGs, we trained a classifier to predict the splicing outcome at NAGNAG tandem splice sites (alternative splicing, constitutive at the first acceptor, or constitutive at the second acceptor). Our classifier achieved a balanced specificity and sensitivity of ≥ 89%. Subsequently, a classifier trained exclusively on data well supported by transcript evidence was used to make genome-wide predictions of NAGNAG splicing outcomes. By generation of more transcript evidence from a next-generation sequencing platform (Roche 454), we found additional evidence for NAGNAG AS, with altogether 664 alternative NAGNAGs being detected in P. patens using all currently available transcript evidence. The 454 data also enabled us to validate the predictions of the classifier, with 64% (80/125) of the well-supported cases of AS being predicted correctly.NAGNAG AS is just as common in the moss P. patens as it is in the seed plants A. thaliana and O. sativa (but not conserved on the level of orthologous introns), and can be predicted with high accuracy. The most informative features are the nucleotides in the NAGNAG and in its immediate vicinity, along with the splice sites scores, as found earlier for NAGNAG AS in animals. Our results suggest that the mechanism behind NAGNAG AS in plants is similar to that in animals and is largely dependent on the splice site and its immediate neighborhood.Eukaryotic primary mRNAs consist of protein-coding regions (exons) and intervening non-coding regions (introns). The mature mRNA transcript, which acts as substrate for translation into protein, is produced by removing introns in a process called splicing. Splicing can be either constitutive, always producing the same mRNA, or alternative, via variable inclusion of parts of the primary transcript. Alternative splicing (AS) is thus a mechani
An ancient genome duplication contributed to the abundance of metabolic genes in the moss Physcomitrella patens
Stefan A Rensing, Julia Ick, Jeffrey A Fawcett, Daniel Lang, Andreas Zimmer, Yves Van de Peer, Ralf Reski
BMC Evolutionary Biology , 2007, DOI: 10.1186/1471-2148-7-130
Abstract: In this study, based on a large collection of EST sequences, we provide evidence that the haploid moss Physcomitrella patens is a paleopolyploid as well. Based on the construction of linearized phylogenetic trees we infer the genome duplication to have occurred between 30 and 60 million years ago. Gene Ontology and pathway association of the duplicated genes in P. patens reveal different biases of gene retention compared with seed plants.Metabolic genes seem to have been retained in excess following the genome duplication in P. patens. This might, at least partly, explain the versatility of metabolism, as described for P. patens and other mosses, in comparison to other land plants.In contrast to animals, the entire multicellular diploid generation of plants (along with the cuticle and thick-walled, non-motile spores) probably evolved after the transition to land [1,2]. All land plants display alternating multicellular generations – the sexual, haploid gametophyte and the asexual, diploid sporophyte. In early land plant fossils the gametophytic and sporophytic generation share about equal morphological complexity, making it likely that the gametophyte was reduced and the sporophyte became the dominant generation in vascular plants [1-3] while in “bryophytes” (mosses, hornworts and liverworts) the sporophyte generation was reduced and the gametophyte became dominant. Thus, “bryophytes” in comparison with vascular plants enable inference of early states of land plant evolution. Based upon spores found in the fossil record, the first plants had occupied the land in the Middle Ordovician, approximately 460 million years ago (MYA) [1]. The first splits among the Embryophyta separated the Bryopsida (mosses), Antocerotophyta (hornworts) and Marchantiophyta (liverworts) from the remainder of the land plants, the vascular plants. The oldest liverwort fossils are from the Late Devonian, ~360 MYA, the oldest mosses to be found in the fossil record are from the Permian, ~270 MYA
High-sensitivity tool for studying phonon related mechanical losses in low loss materials
Daniel Heinert,Anja Zimmer,Ronny Nawrodt,Torsten Koettig,Christian Schwarz,Matthias Hudl,Wolfgang Vodel,Andreas Tünnermann,Paul Seidel
Physics , 2007, DOI: 10.1088/1742-6596/92/1/012183
Abstract: Fundamental mechanical loss mechanisms exist even in very pure materials, for instance, due to the interactions of excited acoustic waves with thermal phonons. A reduction of these losses in a certain frequency range is desired in high precision instruments like gravitational wave detectors. Systematic analyses of the mechanical losses in those low loss materials are essential for this aim, performed in a highly sensitive experimental set-up. Our novel method of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy), is well suited to systematically determine losses at the resonant frequencies of the samples of less than 10^(-9) in the wide temperature range from 5 to 300 K. A high precision set-up in a specially built cryostat allows contactless excitation and readout of the oscillations of the sample. The experimental set-up and measuring procedure are described. Limitations to our experiment due to external loss mechanisms are analysed. The influence of the suspension system as well as the sample preparation is explained.
Mechanical losses in low loss materials studied by Cryogenic Resonant Acoustic spectroscopy of bulk materials (CRA spectroscopy)
Anja Zimmer,Ronny Nawrodt,Daniel Heinert,Christian Schwarz,Matthias Hudl,Torsten Koettig,Wolfgang Vodel,Andreas Tünnermann,Paul Seidel
Physics , 2007, DOI: 10.1088/1742-6596/92/1/012095
Abstract: Mechanical losses of crystalline silicon and calcium fluoride have been analyzed in the temperature range from 5 to 300 K by our novel mechanical spectroscopy method, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectrocopy). The focus lies on the interpretation of the measured data according to phonon-phonon interactions and defect induced losses in consideration of the excited mode shape.

Copyright © 2008-2017 jourlib.org. All rights reserved.