Classes and Narrowing Selectivity of Olfactory Receptor Neurons of Xenopus laevis Tadpoles

In olfactory receptor neurons (ORNs) of aquatic animals amino acids have been shown to be potent stimuli. Here we report on calcium imaging experiments in slices of the olfactory mucosa of Xenopus laevis tadpoles. We were able to determine the response profiles of 283 ORNs to 19 amino acids, where one profile comprises the responses of one ORN to 19 amino acids. 204 out of the 283 response profiles differed from each other. 36 response spectra occurred more than once, i.e., there were 36 classes of ORNs identically responding to the 19 amino acids. The number of ORNs that formed a class ranged from 2 to 13. Shape and duration of amino acid-elicited [Ca2+]i transients showed a high degree of similarity upon repeated stimulation with the same amino acid. Different amino acids, however, in some cases led to clearly distinguishable calcium responses in individual ORNs. Furthermore, ORNs clearly appeared to gain selectivity over time, i.e., ORNs of later developmental stages responded to less amino acids than ORNs of earlier stages. We discuss the narrowing of ORN selectivity over stages in the context of expression of olfactory receptors

How well suited are current thermodynamic models to predict or interpret the composition of (Ba,Sr)SO₄ solid-solutions in geothermal scalings?

In this study, we report results of the analysis of a particularly interesting scaling sample from the geothermal plant in Neustadt-Glewe in northern Germany, which contained 19% Galena (PbS) and 81% of a heterogeneous assemblage of (Ba,Sr)SO₄ crystals with varying compositions, 0.15 < X$_{Ba}$ < 0.53. A main fraction of the sample (~56%) has a barite content of X$_{Ba}$ ≈ 0.32. We try to relate the solid composition of the (Ba,Sr)SO₄ solid-solution to the conditions at the geothermal plant concerning temperature, pressure, and solution composition, and discuss it with respect to the challenges in modelling the composition of (Ba,Sr)SO₄ solid-solutions on the basis of thermodynamic mixing models. We note that considerable uncertainties are related to the description of (Ba,Sr)SO₄ formation by means of thermodynamic models. The scaling composition observed in this study would be in line with endmember solubilities as predicted by the PhreeqC-Pitzer database for 70 °C and an interaction parameter, a0 = 1.6. According to such a model, the scaling heterogeneity would reflect bimodal precipitation behaviour due to various degrees of depletion of the brine with respect to X(Ba)($_{aq}$). Minor fluctuations in X(Ba)($_{aq}$): 0.0017 < X(Ba)($_{aq}$) < 0.0042 explain the full range of observed solid compositions. The choice especially of the interaction parameter seems to some extent arbitrary. This knowledge gap strongly limits the interpretation of (Ba,Sr) SO₄ compositions. Thus, it is not possible to distinguish between kinetic and thermodynamic effects on partitioning or to use the solid-solution composition to draw conclusions about the precipitation conditions (e.g. Temperature)

Purinergic receptor-mediated Ca2+ signaling in the olfactory bulb and the neurogenic area of the lateral ventricles

Like in other vertebrates, the anterior part of the telencephalon of amphibians mainly consists of the olfactory bulb (OB), but different from higher vertebrates, the lateral telencephalic ventricles of larval Xenopus laevis expand deep into the anterior telencephalon. The neurogenic periventricular zone (PVZ) of the lateral ventricles generates new OB neurons throughout the animal’s lifetime. We investigated the ultrastructural organization of the PVZ and found that within a time period of 24 h, 42.54 ± 6.65% of all PVZ cells were actively proliferating. Functional purinergic receptors are widespread in the central nervous system and their activation has been associated with many critical physiological processes, including the regulation of cell proliferation. In the present study we identified and characterized the purinergic system of the OB and the PVZ. ATP and 2MeSATP induced strong [Ca2+]i increases in cells of both regions, which could be attenuated by purinergic antagonists. However, a more thorough pharmacological investigation revealed clear differences between the two brain regions. Cells of the OB almost exclusively express ionotropic P2X purinergic receptor subtypes, whereas PVZ cells express both ionotropic P2X and metabotropic P1 and P2Y receptor subtypes. The P2X receptors expressed in the OB are evidently not involved in the immediate processing of olfactory information

Nicotinic acid adenine dinucleotide phosphate-mediated calcium signalling in effector T cells regulates autoimmunity of the central nervous system

Nicotinic acid adenine dinucleotide phosphate represents a newly identified second messenger in T cells involved in antigen receptor-mediated calcium signalling. Its function in vivo is, however, unknown due to the lack of biocompatible inhibitors. Using a recently developed inhibitor, we explored the role of nicotinic acid adenine dinucleotide phosphate in autoreactive effector T cells during experimental autoimmune encephalomyelitis, the animal model for multiple sclerosis. We provide in vitro and in vivo evidence that calcium signalling controlled by nicotinic acid adenine dinucleotide phosphate is relevant for the pathogenic potential of autoimmune effector T cells. Live two photon imaging and molecular analyses revealed that nicotinic acid adenine dinucleotide phosphate signalling regulates T cell motility and re-activation upon arrival in the nervous tissues. Treatment with the nicotinic acid adenine dinucleotide phosphate inhibitor significantly reduced both the number of stable arrests of effector T cells and their invasive capacity. The levels of pro-inflammatory cytokines interferon-gamma and interleukin-17 were strongly diminished. Consecutively, the clinical symptoms of experimental autoimmune encephalomyelitis were ameliorated. In vitro, antigen-triggered T cell proliferation and cytokine production were evenly suppressed. These inhibitory effects were reversible: after wash-out of the nicotinic acid adenine dinucleotide phosphate antagonist, the effector T cells fully regained their functions. The nicotinic acid derivative BZ194 induced this transient state of non-responsiveness specifically in post-activated effector T cells. Naïve and long-lived memory T cells, which express lower levels of the putative nicotinic acid adenine dinucleotide phosphate receptor, type 1 ryanodine receptor, were not targeted. T cell priming and recall responses in vivo were not reduced. These data indicate that the nicotinic acid adenine dinucleotide phosphate/calcium signalling pathway is essential for the recruitment and the activation of autoaggressive effector T cells within their target organ. Interference with this signalling pathway suppresses the formation of autoimmune inflammatory lesions and thus might qualify as a novel strategy for the treatment of T cell mediated autoimmune diseases

Ratiometric high-resolution imaging of JC-1 fluorescence reveals the subcellular heterogeneity of astrocytic mitochondria

Using the mitochondrial potential (ΔΨm) marker JC-1 (5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide) and high-resolution imaging, we functionally analyzed mitochondria in cultured rat hippocampal astrocytes. Ratiometric detection of JC-1 fluorescence identified mitochondria with high and low ΔΨm. Mitochondrial density was highest in the perinuclear region, whereas ΔΨm tended to be higher in peripheral mitochondria. Spontaneous ΔΨm fluctuations, representing episodes of increased energization, appeared in individual mitochondria or synchronized in mitochondrial clusters. They continued upon withdrawal of extracellular Ca2+, but were antagonized by dantrolene or 2-aminoethoxydiphenylborate (2-APB). Fluo-3 imaging revealed local cytosolic Ca2+ transients with similar kinetics that also were depressed by dantrolene and 2-APB. Massive cellular Ca2+ load or metabolic impairment abolished ΔΨm fluctuations, occasionally evoking heterogeneous mitochondrial depolarizations. The detected diversity and ΔΨm heterogeneity of mitochondria confirms that even in less structurally polarized cells, such as astrocytes, specialized mitochondrial subpopulations coexist. We conclude that ΔΨm fluctuations are an indication of mitochondrial viability and are triggered by local Ca2+ release from the endoplasmic reticulum. This spatially confined organelle crosstalk contributes to the functional heterogeneity of mitochondria and may serve to adapt the metabolism of glial cells to the activity and metabolic demand of complex neuronal networks. The established ratiometric JC-1 imaging—especially combined with two-photon microscopy—enables quantitative functional analyses of individual mitochondria as well as the comparison of mitochondrial heterogeneity in different preparations and/or treatment conditions

Differential Detection of Potentially Hazardous Fusarium Species in Wheat Grains by an Electronic Nose

Fungal infestation on wheat is an increasingly grave nutritional problem in many countries worldwide. Fusarium species are especially harmful pathogens due to their toxic metabolites. In this work we studied volatile compounds released by F. cerealis, F. graminearum, F. culmorum and F. redolens using SPME-GC/MS. By using an electronic nose we were able to differentiate between infected and non-infected wheat grains in the post-harvest chain. Our electronic nose was capable of distinguishing between four wheat Fusaria species with an accuracy higher than 80%

Contactins in the central nervous system: role in health and disease

Contactins are a group of cell adhesion molecules that are mainly expressed in the brain and play pivotal roles in the organization of axonal domains, axonal guidance, neuritogenesis, neuronal development, synapse formation and plasticity, axo-glia interactions and neural regeneration. Contactins comprise a family of six members. Their absence leads to malformed axons and impaired nerve conduction. Contactin mediated protein complex formation is critical for the organization of the axon in early central nervous system development. Mutations and differential expression of contactins have been identified in neuro-developmental or neurological disorders. Taken together, contactins are extensively studied in the context of nervous system development. This review summarizes the physiological roles of all six members of the Contactin family in neurodevelopment as well as their involvement in neurological/neurodevelopmental disorders

Double exponential decay analysis in time- and Legendre-domain.

<p>(<b>a,b</b>) The interaction of Ru(II) complexes with DNA (same as in in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090500#pone-0090500-g001" target="_blank">Fig. 1</a>) shows double exponential decay(<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090500#pone.0090500-Bazzicalupi1" target="_blank">[12]</a>, data courtesy of F. Secco, Univ Pisa,I). Same data fitted in t- (<b>a</b>) and L-domain (<b>b</b>). (<b>c</b>) Probability for the fitting error in the L-domain, , to be smaller than that in the t-domain, , represented as a function of and . Color code of the probability is shown beneath the plot. For each pair () 1000 trials were computed. (<b>d</b>) Relative difference of fitting errors, , as a function of and . Color code beneath the plot. 1000 trials per pixel. Left of the solid and dashed white lines in <b>a</b> and <b>b</b>, the success rate of the fit in the L-domain is larger that and , respectively. Left of the solid and dashed black lines in <b>c</b> and <b>d</b>, the success rate of the fit in the t-domain is larger that 50% and 95%, respectively. Relative error differences were calculated only for successful trials. (<b>e</b>) Success rate of fitting in the L-domain (solid) and t-domain (dashed) along the vertical line in <b>c</b>, i.e., as a function of with kept at .</p