Ongoing neurogenesis in the adult dentate gyrus mediates behavioral responses to ambiguous threat cues.

Fear learning is highly adaptive if utilized in appropriate situations but can lead to generalized anxiety if applied too widely. A role of predictive cues in inhibiting fear generalization has been suggested by stress and fear learning studies, but the effects of partially predictive cues (ambiguous cues) and the neuronal populations responsible for linking the predictive ability of cues and generalization of fear responses are unknown. Here, we show that inhibition of adult neurogenesis in the mouse dentate gyrus decreases hippocampal network activation and reduces defensive behavior to ambiguous threat cues but has neither of these effects if the same negative experience is reliably predicted. Additionally, we find that this ambiguity related to negative events determines their effect on fear generalization, that is, how the events affect future behavior under novel conditions. Both new neurons and glucocorticoid hormones are required for the enhancement of fear generalization following an unpredictably cued threat. Thus, adult neurogenesis plays a central role in the adaptive changes resulting from experience involving unpredictable or ambiguous threat cues, optimizing behavior in novel and uncertain situations.

Swelling of Cellulose-Based Fibrillar and Polymeric Networks Driven by Ion-Induced Osmotic Pressure.

Cellulose-based model materials in the form of fibrillar networks and macromolecular hydrogels were used to investigate the ion-induced swelling in relation to the elasticity and structure of the network. Both networks were charged by the introduction of carboxyl groups onto the cellulose surface, and the dimensions of the networks in aqueous solution were measured as a function of pH. The use of cellulose-model materials that contained either noncrystalline cellulose or cellulose I fibrils made it possible to model the effect of the ion-induced osmotic pressure of a delignified wood fiber wall. The noncrystalline hydrogels represented the noncrystalline domains of the fiber wall and the fibrillar network represented the supramolecular network of cellulose I fibrils of the fiber wall. The experimental results were compared to swelling potentials computed using the Donnan theory, and it was found that the ion-induced water uptake within the cellulose networks followed the theoretical predictions to a large extent. However, fibrillar networks were found to plastically deform upon swelling and deviated from the ideal Donnan theory for polyelectrolyte gel networks. Upon addition of salt to the aqueous phase surrounding the cellulose materials, both hydrogels and fibrillar networks deviated from the Donnan theory predictions, suggesting that structural differences between the networks impact their swelling.

Thermodynamics of the Water-Retaining Properties of Cellulose-Based Networks.

Noncrystalline cellulose-based gel beads were used as a model material to investigate the effect of osmotic stress on a cellulosic network. The gel beads were exposed to osmotic stress by immersion in solutions with different concentrations of high molecular mass dextran and the equilibrium dimensional change of the gel beads was studied using optical microscopy. The volume fraction of cellulose was calculated from the volume of the gel beads in dextran solutions and their dry content and the relation between the cellulose volume fraction and the total osmotic pressure was thus obtained. The results show that the contribution to the osmotic pressure from counterions increases the water-retaining capacity of the beads at high osmotic pressures but also that the main factor controlling the gel bead collapse at high osmotic strains is the resistance to the deformation of the polymer chain network within the beads. Furthermore, the osmotic pressure associated with the deformation of the polymer network, which counteracts the deswelling of the beads, could be fitted to the Wall model indicating that the response of the cellulose polymer networks was independent of the charge of the cellulose. The best fit to the Wall model was obtained when the Flory-Huggins interaction parameter (χ) of the cellulose-water system was set to 0.55-0.60, in agreement with the well-established insolubility of high molecular mass ß-(1,4)-d-glucan polymers in water.

Adult neurogenesis affects motivation to obtain weak, but not strong, reward in operant tasks.

Decreased motivation to seek rewards is a key feature of mood disorders that correlates with severity and treatment outcome. This anhedonia, or apathy, likely reflects impairment in reward circuitry, but the specific neuronal populations controlling motivation are unclear. Granule neurons generated in the adult hippocampus have been implicated in mood disorders, but are not generally considered as part of reward circuits. We investigated a possible role of these new neurons in motivation to work for food and sucrose rewards in operant conditioning tasks using GFAP-TK pharmacogenetic ablation of adult neurogenesis in both rats and mice. Rats and mice lacking adult neurogenesis showed normal lever press responding during fixed ratio training, reward devaluation, and Pavlovian Instrumental Transfer, suggesting no impairment in learning. However, on an exponentially progressive ratio schedule, or when regular chow was freely available in the testing chamber, TK rats and mice showed less effort to gain sucrose tablets. When working for balanced food tablets, which rats and mice of both genotypes strongly preferred over sucrose, the genotype effects on behavior were lost. This decrease in effort under conditions of low reward suggests that loss of adult neurogenesis decreases motivation to seek reward in a manner that may model behavioral apathy.

Assessing reward preference using operant behavior in male and female mice.

Many different solid food pellets are available as reinforcers for rodents in operant behavior tests. Different reward formulations have not been compared, so it is unclear whether mice show strong preferences for different rewards and whether such preferences are consistent within or across sex and background strain. Here we show that mice have strong preferences for two balanced diet food rewards over sucrose pellets, and preference for one balanced diet pellet formulation over another, in a simultaneous choice test using a low effort fixed ratio operant test. All mice, of both sexes and both CD1 and C57 background strains, showed the same strong preferences among these three types of reinforcers. In contrast, flavorings added to the reward pellets had relatively small and more variable effects on preference. The preference for balanced diet pellets over sucrose pellets was seen also in the total numbers of rewards consumed in low effort tests with food pellets or only sucrose pellets available. However, progressive ratio testing showed that mice worked harder for sucrose pellets than for the preferred balanced diet pellets. These findings indicate that reinforcers with similar and very different preference profiles are readily available and that testing with different rewards can produce different, and sometimes unexpected, results.

Strain differences in stress responsivity are associated with divergent amygdala gene expression and glutamate-mediated neuronal excitability.

Stress is a major risk factor for numerous neuropsychiatric diseases. However, susceptibility to stress and the qualitative nature of stress effects on behavior differ markedly among individuals. This is partly because of the moderating influence of genetic factors. Inbred mouse strains provide a relatively stable and restricted range of genetic and environmental variability that is valuable for disentangling gene-stress interactions. Here, we screened a panel of inbred strains for anxiety- and depression-related phenotypes at baseline (trait) and after exposure to repeated restraint. Two strains, DBA/2J and C57BL/6J, differed in trait and restraint-induced anxiety-related behavior (dark/light exploration, elevated plus maze). Gene expression analysis of amygdala, medial prefrontal cortex, and hippocampus revealed divergent expression in DBA/2J and C57BL/6J both at baseline and after repeated restraint. Restraint produced strain-dependent expression alterations in various genes including glutamate receptors (e.g., Grin1, Grik1). To elucidate neuronal correlates of these strain differences, we performed ex vivo analysis of glutamate excitatory neurotransmission in amygdala principal neurons. Repeated restraint augmented amygdala excitatory postsynaptic signaling and altered metaplasticity (temporal summation of NMDA receptor currents) in DBA/2J but not C57BL/6J. Furthermore, we found that the C57BL/6J-like changes in anxiety-related behavior after restraint were absent in null mutants lacking the modulatory NMDA receptor subunit Grin2a, but not the AMPA receptor subunit Gria1. Grin2a null mutants exhibited significant ( approximately 30%) loss of dendritic spines on amygdala principal neurons under nonrestraint conditions. Collectively, our data support a model in which genetic variation in glutamatergic neuroplasticity in corticolimbic circuitry underlies phenotypic variation in responsivity to stress.

A novel role for PSD-95 in mediating ethanol intoxication, drinking and place preference.

The synaptic signaling mechanisms mediating the behavioral effects of ethanol (EtOH) remain poorly understood. Post-synaptic density 95 (PSD-95, SAP-90, Dlg4) is a key orchestrator of N-methyl-D-aspartate receptors (NMDAR) and glutamatergic synapses, which are known to be major sites of EtOH's behavioral actions. However, the potential contribution of PSD-95 to EtOH-related behaviors has not been established. Here, we evaluated knockout (KO) mice lacking PSD-95 for multiple measures of sensitivity to the acute intoxicating effects of EtOH (ataxia, hypothermia, sedation/hypnosis), EtOH drinking under conditions of free access and following deprivation, acquisition and long-term retention of EtOH conditioned place preference (CPP) (and lithium chloride-induced conditioned taste aversion), and intoxication-potentiating responses to NMDAR antagonism. PSD-95 KO exhibited increased sensitivity to the sedative/hypnotic, but not ataxic or hypothermic, effects of acute EtOH relative to wild-type controls (WT). PSD-95 KO consumed less EtOH than WT, particularly at higher EtOH concentrations, although increases in KO drinking could be induced by concentration-fading and deprivation. PSD-95 KO showed normal EtOH CPP 1 day after conditioning, but showed significant aversion 2 weeks later. Lithium chloride-induced taste aversion was impaired in PSD-95 KO at both time points. Finally, the EtOH-potentiating effects of the NMDAR antagonist MK-801 were intact in PSD-95 KO at the dose tested. These data reveal a major, novel role for PSD-95 in mediating EtOH behaviors, and add to growing evidence that PSD-95 is a key mediator of the effects of multiple abused drugs.

The use of model cellulose gel beads to clarify flame-retardant characteristics of layer-by-layer nanocoatings.

Layer-by-Layer (LbL) assembled nanocoatings are exploited to impart flame-retardant properties to cellulosic substrates. A model cellulose material can make it possible to investigate an optimal bilayer (BL) range for the deposition of coating while elucidating the main flame-retardant action thus allowing for an efficient design of optimized LbL formulations. Model cellulose gel beads were prepared by dissolving cellulose-rich fibers followed by precipitation. The beads were LbL-treated with chitosan (CH) and sodium hexametaphosphate (SHMP). The char forming properties were studied using thermal gravimetric analysis. The coating increased the char yield in nitrogen to up to 29 % and showed a distinct pattern of micro intumescent behavior upon heating. An optimal range of 10-20 BL is observed. The well-defined model cellulose gel beads hence introduce a new scientific route both to clarify the fundamental effects of different film components and to optimize the composition of the films.

Prenatal maternal infection promotes tissue-specific immunity and inflammation in offspring.

The immune system has evolved in the face of microbial exposure. How maternal infection experienced at distinct developmental stages shapes the offspring immune system remains poorly understood. Here, we show that during pregnancy, maternally restricted infection can have permanent and tissue-specific impacts on offspring immunity. Mechanistically, maternal interleukin-6 produced in response to infection can directly impose epigenetic changes on fetal intestinal epithelial stem cells, leading to long-lasting impacts on intestinal immune homeostasis. As a result, offspring of previously infected dams develop enhanced protective immunity to gut infection and increased inflammation in the context of colitis. Thus, maternal infection can be coopted by the fetus to promote long-term, tissue-specific fitness, a phenomenon that may come at the cost of predisposition to inflammatory disorders.

Does gene deletion of AMPA GluA1 phenocopy features of schizoaffective disorder?

Glutamatergic dysfunction is strongly implicated in schizophrenia and mood disorders. GluA1 knockout (KO) mice display schizophrenia- and depression-related abnormalities. Here, we asked whether GluA1 KO show mania-related abnormalities. KO were tested for behavior in approach/avoid conflict tests, responses to repeated forced swim exposure, and locomotor responses under stress and after psychostimulant treatment. The effects of rapid dopamine depletion and treatment with lithium or a GSK-3ß inhibitor (SB216763) on KO locomotor hyperactivity were tested. Results showed that KO exhibited novelty- and stress-induced locomotor hyperactivity, reduced forced swim immobility and alterations in approach/avoid conflict tests. Psychostimulant treatment and dopamine depletion exacerbated KO locomotor hyperactivity. Lithium, but not SB216763, treatment normalized KO anxiety-related behavior and partially reversed hyperlocomotor behavior, and also reversed elevated prefrontal cortex levels of phospho-MARCKS and phospho-neuromodulin. Collectively, these findings demonstrate mania-related abnormalities in GluA1 KO and, combined with previous findings, suggest this mutant may provide a novel model of features of schizoaffective disorder.

Activity-dependent isomerization of Kv4.2 by Pin1 regulates cognitive flexibility.

Voltage-gated K+ channels function in macromolecular complexes with accessory subunits to regulate brain function. Here, we describe a peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1)-dependent mechanism that regulates the association of the A-type K+ channel subunit Kv4.2 with its auxiliary subunit dipeptidyl peptidase 6 (DPP6), and thereby modulates neuronal excitability and cognitive flexibility. We show that activity-induced Kv4.2 phosphorylation triggers Pin1 binding to, and isomerization of, Kv4.2 at the pThr607-Pro motif, leading to the dissociation of the Kv4.2-DPP6 complex. We generated a novel mouse line harboring a knock-in Thr607 to Ala (Kv4.2TA) mutation that abolished dynamic Pin1 binding to Kv4.2. CA1 pyramidal neurons of the hippocampus from these mice exhibited altered Kv4.2-DPP6 interaction, increased A-type K+ current, and reduced neuronal excitability. Behaviorally, Kv4.2TA mice displayed normal initial learning but improved reversal learning in both Morris water maze and lever press paradigms. These findings reveal a Pin1-mediated mechanism regulating reversal learning and provide potential targets for the treatment of neuropsychiatric disorders characterized by cognitive inflexibility.

Impaired fear extinction learning and cortico-amygdala circuit abnormalities in a common genetic mouse strain.

Fear extinction is a form of new learning that results in the inhibition of conditioned fear. Trait deficits in fear extinction are a risk factor for anxiety disorders. There are few examples of naturally occurring animal models of impaired extinction. The present study compared fear extinction in a panel of inbred mouse strains. This strain survey revealed an impairment in fear extinction in 129/SvImJ (129S1). The phenotypic specificity of this deficit was evaluated by comparing 129S1 and C57BL/6J for one-trial and multitrial fear conditioning, nociception, and extinction of conditioned taste aversion and an appetitive instrumental response. 129S1 were tested for sensitivity to the extinction-facilitating effects of extended training, as well as d-cycloserine and yohimbine treatment. To elucidate the neural basis of impaired 129S1 fear extinction, c-Fos and Zif268 expression was mapped after extinction recall. Results showed that impaired fear extinction in 129S1 was unrelated to altered fear conditioning or nociception, and was dissociable from intact appetitive extinction. Yohimbine treatment facilitated extinction in 129S1, but neither extended extinction training nor d-cycloserine treatment improved 129S1 extinction. After extinction recall, 129S1 showed reduced c-Fos and Zif268 expression in the infralimbic cortex and basolateral amygdala, and elevated c-Fos or Zif268 expression in central nucleus of the amygdala and medial paracapsular intercalated cell mass, relative to C57BL/6J. Collectively, these data demonstrate a deficit in fear extinction in 129S1 associated with a failure to properly engage corticolimbic extinction circuitry. This common inbred strain provides a novel model for studying impaired fear extinction in anxiety disorders.

Desipramine potentiation of the acute depressant effects of ethanol: modulation by alpha2-adrenoreceptors and stress.

Ethanol exerts effects on the brain noradrenergic system, and these are thought to contribute to the sedative/hypnotic (depressant) effects of ethanol. Recent studies suggest that the norepinephrine transporter (NET) plays an important role in modulating ethanol's depressant effects. The aim of the present study was to further characterize this role. Transporter blockers with varying affinity for NET versus the serotonin transporter (desipramine>fluoxetine>citalopram) were tested for their ability to alter ethanol's depressant effects, and for comparison, hypothermic effects. Effects of desipramine on another depressant, pentobarbital, were examined. Desipramine potentiation of ethanol's depressant effects was assessed following depletion of brain norepinephrine via N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP-4) treatment, or depletion of brain 5-HT via para-chlorophenylalanine methyl ester hydrochloride (PCPA) treatment. The effects of co-administration of either the selective alpha2-adrenoreceptor agonist (dexmedetomidine) or the selective alpha2-adrenoreceptor antagonist (atipamezole) on desipramine's effect on ethanol's depressant effects were examined. Given the close link between stress, ethanol and norepinephrine, desipramine potentiation of ethanol's depressant effects was tested following repeated forced swim stress. Results showed that desipramine, but not SERT-selective doses of citalopram or fluoxetine, strongly potentiated the depressant (not hypothermic) effects of ethanol. These effects were mimicked by dexmedetomidine and blocked by atipamezole, but not by depletion of either norepinephrine or 5-HT. Desipramine potentiation of ethanol's depressant effects was abolished following repeated stress. Present findings further support a major role for NET and the alpha2-adrenoreceptor in modulating the depressant effects of ethanol, with possible implications for understanding the role of noradrenergic dysfunction in stress-related alcoholism.

Comparison of dopamine D1 and D5 receptor knockout mice for cocaine locomotor sensitization.

RATIONALE: There is compelling support for the contribution of dopamine and the D1R-like (D1R, D5R) receptor subfamily to the behavioral and neural effects of psychostimulant drugs of abuse. The relative roles of D1R and D5R subtypes in mediating these effects are not clear. OBJECTIVES: The objectives of this study are to directly compare (C57BL/6J congenic) D1R knockout (KO) and D5R KO mice for baseline locomotor exploration, acute locomotor responses to cocaine, and locomotor sensitization to repeated cocaine administration, and to examine cocaine conditioned place preference (CPP) in D5R KO. MATERIALS AND METHODS: D1R KO, D5R KO, and wild-type (WT) were assessed for baseline open field exploration, locomotor-stimulating effects of 15 mg/kg acute cocaine and sensitized locomotor responses to cocaine after repeated home cage treatment with 20 or 30 mg/kg cocaine. D5R KO and WT were tested for CPP to 15 mg/kg cocaine. RESULTS: D1R KO showed modest basal hyperactivity and increased center exploration relative to WT. Acute locomotor responses to cocaine were consistently absent in D1R KO, but intact in D5R KO. D5R KO showed normal locomotor sensitization to cocaine and normal cocaine CPP. D1R KO failed to show a sensitized locomotor response to 30 mg/kg cocaine. Failure to sensitize in D1R KO was not because of excessive stereotypies. Surprisingly, D1R KO showed a strong trend for sensitization to 20 mg/kg cocaine. CONCLUSIONS: D5R KO does not alter acute or sensitized locomotor responses to cocaine or cocaine CPP. D1R KO abolishes acute locomotor response to cocaine, but does not fully prevent locomotor sensitization to cocaine at all doses.

The neuropeptide Y Y1 receptor subtype is necessary for the anxiolytic-like effects of neuropeptide Y, but not the antidepressant-like effects of fluoxetine, in mice.

RATIONALE: Neuropeptide Y (NPY) is implicated in the pathophysiology of affective illness. Multiple receptor subtypes (Y1R, Y2R, and Y5R) have been suggested to contribute to NPY's effects on rodent anxiety and depression-related behaviors. OBJECTIVES: To further elucidate the role of Y1R in (1) NPY's anxiolytic-like effects and (2) fluoxetine's antidepressant-like and neurogenesis-inducing effects. METHODS: Mice lacking Y1R were assessed for spontaneous anxiety-like behavior (open field, elevated plus-maze, and light/dark exploration test) and Pavlovian fear conditioning, and for the anxiolytic-like effects of intracerebroventricularly (icv)-administrated NPY (elevated plus-maze). Next, Y1R -/- were assessed for the antidepressant-like effects of acute fluoxetine in the forced swim test and chronic fluoxetine in the novelty-induced hypophagia test, as well as for chronic fluoxetine-induced hippocampal neurogenesis. RESULTS: Y1R -/- exhibited largely normal baseline behavior as compared to +/+ littermate controls. Intraventricular administration of NPY in Y1R -/- mice failed to produce the normal anxiolytic-like effect in the elevated plus-maze test seen in +/+ mice. Y1R mutant mice showed higher immobility in the forced swim test and longer latencies in the novelty-induced hypophagia test. In addition, Y1R -/- mice responded normally to the acute and chronic effects of fluoxetine treatment in the forced swim test and the novelty-induced hypophagia test, respectively, as well as increased neuronal precursor cell proliferation in the hippocampus. CONCLUSIONS: These data demonstrate that Y1R is necessary for the anxiolytic-like effects of icv NPY, but not for the antidepressant-like or neurogenesis-inducing effects of fluoxetine. The present study supports targeting Y1R as a novel therapeutic target for anxiety disorders.

Effects of adolescent fluoxetine treatment on fear-, anxiety- or stress-related behaviors in C57BL/6J or BALB/cJ mice.

RATIONALE: 5-Hydroxytryptamine (5-HT, serotonin) plays a major role in brain ontogeny. Disruption of 5-HT during early postnatal development produces lasting changes in rodent 'emotion-related' behaviors. Adverse effects of treatment with serotonin reuptake inhibitor (SRI) antidepressants have been reported in human adolescents. However, the long-term effects of chronic SRI treatment during adolescence in rodents remain unclear. OBJECTIVES: The objectives of the study are to assess the effects of fluoxetine treatment throughout the adolescent period in measures of fear-, anxiety- and stress-related endpoints in drug-free adults and to examine these effects in two genetic strains of mice differing in baseline stress- and anxiety-related behaviors and sensitivity to SRIs. MATERIALS AND METHODS: C57BL/6J and BALB/cJ mice received one of two fluoxetine doses for 4 weeks during adolescence (3-7 weeks old). A separate group of C57BL/6J and BALB/cJ mice received fluoxetine for 4 weeks during adulthood (8-12 weeks old). After a 3-week washout period, mice were tested for anxiety-like behaviors (novel open field, elevated plus-maze), fear conditioning and extinction, and stress-related responses to forced swim, as well as serotonin brain levels. RESULTS: Adolescent fluoxetine treatment did not increase adult measures of anxiety-, fear- or stress-related behaviors, or brain serotonin levels. The same duration of treatment in adulthood also had no effects on these measures when tested after a 3-week washout period. CONCLUSIONS: In clear contrast with emotion-related abnormalities caused by preadolescent fluoxetine treatment or genetic inactivation of fluoxetine's pharmacological target, the 5-HT transporter, fluoxetine treatment throughout mouse adolescence did not produce detectable, lasting abnormalities in either "high" or "low anxiety" inbred mouse strains.

Role of major NMDA or AMPA receptor subunits in MK-801 potentiation of ethanol intoxication.

BACKGROUND: The glutamate system plays a major role in mediating EtOH's effects on brain and behavior, and is implicated in the pathophysiology of alcohol-related disorders. N-methyl-D-aspartate receptor (NMDAR) antagonists such as MK-801 (dizocilpine) interact with EtOH at the behavioral level, but the molecular basis of this interaction is unclear. METHODS: We first characterized the effects of MK-801 treatment on responses to the ataxic (accelerating rotarod), hypothermic and sedative/hypnotic effects of acute EtOH administration in C57BL/6J and 129/SvImJ inbred mice. Effects of another NMDAR antagonist, phencyclidine, on EtOH-induced sedation/hypnosis were also assessed. Gene knockout of the NMDAR subunit NR2A or l-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate GluR1 or pharmacological antagonism of the NMDAR subunit NR2B (via Ro 25-6981) was employed to examine whether inactivating any one of these glutamate signaling molecules modified MK-801's effect on EtOH-related behaviors. RESULTS: MK-801 markedly potentiated the ataxic effects of 1.75 g/kg EtOH and the sedative/hypnotic effects of 3.0 g/kg EtOH, but not the hypothermic effects of 3.0 g/kg EtOH, in C57BL/6J and 129/SvImJ mice. Phencyclidine potentiated EtOH-induced sedation/hypnosis in both inbred strains. Neither NR2A nor GluR1 KO significantly altered basal EtOH-induced ataxia, hypothermia, or sedation/hypnosis. Ro 25-6981 modestly increased EtOH-induced sedation/hypnosis. The ability of MK-801 to potentiate EtOH-induced ataxia and sedation/hypnosis was unaffected by GluR1 KO or NR2B antagonism. NR2A KO partially reduced MK-801 + EtOH-induced sedation/hypnosis, but not ataxia or hypothermia. CONCLUSIONS: Data confirm a robust and response-specific potentiating effect of MK-801 on sensitivity to EtOH's intoxicating effects. Inactivation of three major components of glutamate signaling had no or only partial impact on the ability of MK-801 to potentiate behavioral sensitivity to EtOH. Further work to elucidate the mechanisms underlying NMDAR x EtOH interactions could ultimately provide novel insight into the role of NMDARs in alcoholism and its treatment.

Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers.

Macroscopic beads of water-based gels consisting of uncharged and partially charged ß-(1,4)-d-glucan polymers were developed to be used as a novel model material for studying the water induced swelling of the delignified plant fiber walls. The gel beads were prepared by drop-wise precipitation of solutions of dissolving grade fibers carboxymethylated to different degrees. The internal structure was analyzed using Solid State Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance and Small Angle X-ray Scattering showing that the internal structure could be considered a homogeneous, non-crystalline and molecularly dispersed polymer network. When beads with different charge densities were equilibrated with aqueous solutions of different ionic strengths and/or pH, the change in water uptake followed the trends expected for weak polyelectrolyte gels and the trends found for cellulose-rich fibers. When dried and subsequently immersed in water the beads also showed an irreversible loss of swelling depending on the charge and type of counter-ion which is commonly also found for cellulose-rich fibers. Taken all these results together it is clear that the model cellulose-based beads constitute an excellent tool for studying the fundamentals of swelling of cellulose rich plant fibers, aiding in the elucidation of the different molecular and supramolecular contributions to the swelling.

DPP6 Loss Impacts Hippocampal Synaptic Development and Induces Behavioral Impairments in Recognition, Learning and Memory.

DPP6 is well known as an auxiliary subunit of Kv4-containing, A-type K+ channels which regulate dendritic excitability in hippocampal CA1 pyramidal neurons. We have recently reported, however, a novel role for DPP6 in regulating dendritic filopodia formation and stability, affecting synaptic development and function. These results are notable considering recent clinical findings associating DPP6 with neurodevelopmental and intellectual disorders. Here we assessed the behavioral consequences of DPP6 loss. We found that DPP6 knockout (DPP6-KO) mice are impaired in hippocampus-dependent learning and memory. Results from the Morris water maze and T-maze tasks showed that DPP6-KO mice exhibit slower learning and reduced memory performance. DPP6 mouse brain weight is reduced throughout development compared with WT, and in vitro imaging results indicated that DPP6 loss affects synaptic structure and motility. Taken together, these results show impaired synaptic development along with spatial learning and memory deficiencies in DPP6-KO mice.

Short-term and long-term effects of postnatal exposure to an adult male in C57BL/6J mice.

Rodent models provide a valuable approach to elucidating the pathophysiological mechanisms underlying the deleterious effects of childhood trauma and stress. Neonatal rats and mice emit ultrasonic vocalizations (USVs) when separated from the dam and litter. USVs are suppressed in rat pups by exposure to the putatively infanticidal threat of an adult male. In the present study, C57BL/6J mouse pups were exposed to an anaesthetized (non-sire) adult C57BL/6J male for 3-min/day from postnatal days 2-14, and subsequently tested for anxiety-related behaviors (using the novel open field, elevated plus-maze, light/dark exploration tests) and depression-related behavior (using the forced swim test) at 11 weeks of age. In a separate cohort, hypothalamic-pituitary-adrenal-axis activation was measured via plasma corticosterone levels following either a single male-exposure or separation episode. Results showed that pups exposed to an adult male emitted significantly fewer USVs than separation-only counterparts. Corticosterone levels were significantly lower following single exposure to the adult male than separation alone. Repeated neonatal male-exposure did not lead to significant alterations in anxiety- or depression-related behaviors in adulthood. Taken together, present data suggest that the form of adult male-exposure employed did not act as a significant stressor, at least in this mouse strain. Further studies will be needed to determine whether alternative mouse strains, exposure protocols or adult behavioral assays will produce a different pattern of short-term and long-term effects.