Social Communication in Mice – Are There Optimal Cage Conditions?

Social communication is heavily affected in patients with neuropsychiatric disorders. Accordingly, mouse models designed to study the mechanisms leading to these disorders are tested for this phenotypic trait. Test conditions vary between different models, and the effect of these test conditions on the quantity and quality of social interactions and ultrasonic communication is unknown. The present study examines to which extent the habituation time to the test cage as well as the shape / size of the cage influence social communication in freely interacting mice. We tested 8 pairs of male mice in free dyadic social interactions, with two habituation times (20 min and 30 min) and three cage formats (rectangle, round, square). We tested the effect of these conditions on the different types of social contacts, approach-escape sequences, follow behavior, and the time each animal spent in the vision field of the other one, as well as on the emission of ultrasonic vocalizations and their contexts of emission. We provide for the first time an integrated analysis of the social interaction behavior and ultrasonic vocalizations. Surprisingly, we did not highlight any significant effect of habituation time and cage shape / size on the behavioral events examined. There was only a slight increase of social interactions with the longer habituation time in the round cage. Remarkably, we also showed that vocalizations were emitted during specific behavioral sequences especially during close contact or approach behaviors. The present study provides a protocol reliably eliciting social contacts and ultrasonic vocalizations in adult male mice. This protocol is therefore well adapted for standardized investigation of social interactions in mouse models of neuropsychiatric disorders.     

Localization and Quantification of Plasma Membrane Aquaporin Expression in Maize Primary Root: A Clue to Understanding their Role as Cellular Plumbers

Water movement across root tissues occurs by parallel apoplastic, symplastic, and transcellular pathways that the plant can control to a certain extent. Because water channels or aquaporins (AQPs) play an important role in regulating water flow, studies on AQP mRNA and protein expression in different root tissues are essential. Here, we quantified and localized the expression of Zea mays plasma membrane AQPs (ZmPIPs) in primary root tip using in situ and quantitative RT-PCR and immunodetection approaches. All ZmPIP genes except ZmPIP2;7 were expressed in primary roots. Expression was found to be dependent on the developmental stage of the root, with, in general, an increase in expression towards the elongation and mature zones. Two genes, ZmPIP1;5 and ZmPIP2;5, showed the greatest increase in expression (up to 11- and 17-fold, respectively) in the mature zone, where they accounted for 50% of the total expressed ZmPIPs. The immunocytochemical localization of ZmPIP2;1 and ZmPIP2;5 in the exodermis and endodermis indicated that they are involved in root radial water movement. In addition, we detected a polar localization of ZmPIP2;5 to the external periclinal side of epidermal cells in root apices, suggesting an important role in water uptake from the root surface. Finally, protoplast swelling assays showed that root cells display a variable, but globally low, osmotic water permeability coefficient (P _f < 10 μm/s). However, the presence of a population of cells with a higher P _f (up to 26 μm/s) in mature zone of the root might be correlated with the increased expression of several ZmPIP genes.     

Maize plasma membrane aquaporins belonging to the PIP1 and PIP2 subgroups are in vivo phosphorylated

Aquaporins are channel proteins that facilitate transmembrane water movement. In this study, we showed that plasma membrane intrinsic proteins (PIPs) from maize shoots are in vitro and in vivo phosphorylated on serine residues by a calcium-dependent kinase associated with the membrane fraction. Mass spectrometry identified phosphorylated peptides corresponding to the C-terminal region of (i) ZmPIP2;1, ZmPIP2;2 and/or ZmPIP2;7; (ii) ZmPIP2;3 and/or ZmPIP2;4; (iii) ZmPIP2;6; together with (iv) a phosphorylated peptide located in the N-terminal region of ZmPIP1;1, ZmPIP1;2, ZmPIP1;3 and/or ZmPIP1;4. The role of phosphorylation in the water channel activity of wild-type and mutant ZmPIP2;1 was studied in Xenopus laevis oocytes. Activation of endogenous protein kinase A increased the osmotic water permeability coefficient of ZmPIP2;1-expressing oocytes, suggesting that phosphorylation activates its channel activity. Mutation of S126 or S203, putative phosphorylated serine residues conserved in all plant PIPs, to alanine decreased ZmPIP2;1 activity by 30-50%, without affecting its targeting to the plasma membrane. Mutation of S285, which is phosphorylated in planta, to alanine or glutamate did not affect the water channel activity. These results indicate that, in oocytes, S126 and S203 play an important role in ZmPIP2;1 activity and that phosphorylation of S285 is not required for its activity.     

Structural insights into a new homodimeric self-activated GTPase family

The human XAB1/MBDin GTPase and its close homologues form one of the ten phylogenetically distinct families of the SIMIBI (after signal recognition particle, MinD and BioD) class of phosphate-binding loop NTPases. The genomic context and the partners identified for the archaeal and eukaryotic homologues indicate that they are involved in genome maintenance--DNA repair or replication. The crystal structure of PAB0955 from Pyrococcus abyssi shows that, unlike other SIMIBI class G proteins, these highly conserved GTPases are homodimeric, regardless of the presence of nucleotides. The nucleotide-binding site of PAB0955 is rather rigid and its conformation is closest to that of the activated SRP G domain. One insertion to the G domain bears a strictly conserved GPN motif, which is part of the catalytic site of the other monomer and stabilizes the phosphate ion formed. Owing to this unique functional feature, we propose to call this family as GPN-loop GTPase.     

NMDA Receptor Hypofunction Leads to Generalized and Persistent Aberrant γ Oscillations Independent of Hyperlocomotion and the State of Consciousness

Background

The psychotomimetics ketamine and MK-801, non-competitive NMDA receptor (NMDAr) antagonists, induce cognitive impairment and aggravate schizophrenia symptoms. In conscious rats, they produce an abnormal behavior associated with a peculiar brain state characterized by increased synchronization in ongoing γ (30–80 Hz) oscillations in the frontoparietal (sensorimotor) electrocorticogram (ECoG). This study investigated whether NMDAr antagonists-induced aberrant γ oscillations are correlated with locomotion and dependent on hyperlocomotion-related sensorimotor processing. This also implied to explore the contribution of intracortical and subcortical networks in the generation of these pathophysiological ECoG γ oscillations.

Methodology/Principal Findings

Quantitative locomotion data collected with a computer-assisted video tracking system in combination with ECoG revealed that ketamine and MK-801 induce highly correlated hyperlocomotion and aberrant γ oscillations. This abnormal γ hyperactivity was recorded over the frontal, parietal and occipital cortices. ECoG conducted under diverse consciousness states (with diverse anesthetics) revealed that NMDAr antagonists dramatically increase the power of basal γ oscillations. Paired ECoG and intracortical local field potential recordings showed that the ECoG mainly reflects γ oscillations recorded in underlying intracortical networks. In addition, multisite recordings revealed that NMDAr antagonists dramatically enhance the amount of ongoing γ oscillations in multiple cortical and subcortical structures, including the prefrontal cortex, accumbens, amygdala, basalis, hippocampus, striatum and thalamus.

Conclusions/Significance

NMDAr antagonists acutely produces, in the rodent CNS, generalized aberrant γ oscillations, which are not dependent on hyperlocomotion-related brain state or conscious sensorimotor processing. These findings suggest that NMDAr hypofunction-related generalized γ hypersynchronies represent an aberrant diffuse network noise, a potential electrophysiological correlate of a psychotic-like state. Such generalized noise might cause dysfunction of brain operations, including the impairments in cognition and sensorimotor integration seen in schizophrenia.     

Expression of a cauliflower tonoplast aquaporin tagged with GFP in tobacco suspension cells correlates with an increase in cell size

In plants, vacuoles are essential organelles that undergo dynamic volume changes during cell growth due to rapid and high flow of water through tonoplast water-carrying channels composed of integral proteins (tonoplast aquaporins). The tonoplast BobTIP26-1 from cauliflower has previously been shown to be an efficient active aquaporin in Xenopus leavis oocytes. In this study we used tobacco (Nicotiana tabacum cv. Wisconsin 38) suspension cells to examine the effect of BobTIP26-1 expression. In order to follow the intracellular localisation of the protein in real time, the gfp sequence was fused downstream to the BobTIP26-1 coding region. The fusion protein BobTIP26-1::GFP is less active than BobTIP26-1 by itself when expressed in Xenopus oocytes. Nevertheless, this fusion protein is well targeted to the tonoplast of the plant suspension cell when expressed via Agrobacterium co-cultivation. A complex tonoplast labelling is shown when young vacuolated cells are observed. The expression of the fusion protein does not affect the growth rate of the cells but increases their volume. We postulate that the increase in cell volume is triggered by the fusion protein allowing vacuolar volume increase.     

Triazine-human serum albumin association: thermodynamic approach and sodium effect

Human serum albumin (HSA) serves as a carrier protein to transport triazine herbicides to molecular targets. In this paper, a theoretical treatment was developed to describe the HSA-triazine herbicides association. A determination of the association constant, K, as well as the degree of complexation n(c) (the percent of complex guest) was carried out. Enthalpy-entropy compensation was also analyzed in relation to this mathematical model to confirm the herbicide complexation behavior with HSA. The role of the sodium cation (Na(+)) on this association was investigated. It was expected that the sodium ion would act on the herbicide-HSA association process by modifying the surface tension of the bulk solvent and increase the K and n(c) values. The results showed that for patients who suffer from Na(+) desequilibrium, the triazine-HSA binding would change and as well the toxicological effect of these herbicides.     

Amatoxins in wood-rotting Galerina marginata

Amatoxins, bicyclic octapeptide derivatives responsible for severe hepatic failure, are present in several Basidiomycota species belonging to four genera, i.e. Amanita, Conocybe, Galerina and Lepiota. DNA studies for G. autumnalis, G. marginata, G. oregonensis, G. unicolor and G. venenata (section Naucoriopsis) determined that these species are the same, supporting the concept of Galerina marginata complex. These mostly lignicolous species are designated as white-rot fungi having a broad host range and capable of degrading both hardwoods and softwoods. Twenty-seven G. marginata basidiomes taken from different sites and hosts (three sets) as well as 17 A. phalloides specimens (three sets) were collected in French locations. The 44 basidiomes were examined for amatoxins and phallotoxins using high-performance liquid chromatography. Toxinological data for the wood-rotting G. marginata and the ectomycorrhizal A. phalloides species were compared and statistically analyzed. The acidic and neutral phallotoxins were not detected in any G. marginata specimen, whereas the acidic (β-Ama) and neutral (α-Ama and γ-Ama) amanitins were found in all basidiomes from either Angiosperms or Gymnosperms hosts. The G. marginata amatoxin content varied from 78.17 to 243.61 μg.mg(-1) of fresh weight and was elevated significantly in one set out of three. The amanitin amounts from certain Galerina specimens were higher than those from some A. phalloides basidiomes. Relationship between the amanitin distribution and the chemical composition of substrate was underlined and statistically validated for the white-rot G. marginata. Changes in nutritional components from decayed host due to enzymatic systems and genetic factors as well as environmental conditions seem to play a determinant role in the amanitin profile. Variability noticed in the amanitin distribution for the white-rot G. marginata basidiomes was not observed for the ectomycorrhizal A. phalloides specimens.     

Regulation of plant aquaporin activity

Accumulating evidence indicates that aquaporins play a key role in plant water relations. Plant aquaporins are part of a large and highly divergent protein family that can be divided into four subfamilies according to amino acid sequence similarity. As in other organisms, plant aquaporins facilitate the transcellular movement of water, but, in some cases, also the flux of small neutral solutes across a cellular membrane. Plant cell membranes are characterized by a large range of osmotic water permeabilities, and recent data indicate that plant aquaporin activity might be regulated by gating mechanisms. The factors affecting the gating behaviour possibly involve phosphorylation, heteromerization, pH, Ca2+, pressure, solute gradients and temperature. Regulation of aquaporin trafficking may also represent a way to modulate membrane water permeability. The aim of this review is to integrate recent molecular and biophysical data on the mechanisms regulating aquaporin activity in plant membranes and to relate them to putative changes in protein structure.