bluuebunny/crossref_metadata_2025_split huggingface dataset:
Habitat‐dependent song divergence at subspecies level in the grey‐breasted wood‐wren
Authors: DINGLE C. , HALFWERK W. , SLABBEKOORN H. 
Published: April 2008

AbstractSong divergence among populations can theoretically lead to reproductive divergence and speciation. Despite many studies, this theory is still controversial. Habitat differences have been shown to shape songs, but few studies have looked for a link between ecologically driven acoustic and genetic divergence. We tested whether environmental selection has driven song divergence in two genetically distinct, but hybridizing, subspecies of the grey‐breasted wood‐wren (Henicorhina leucophrys) in Ecuador. Several acoustic features showed significant divergence between the subspecies. Spectral song divergence correlated with ambient noise profiles which differed significantly between the habitats of both subspecies. Temporal song divergence also corresponded as expected to vegetation density. However, in terms of quantified levels of reverberations, we found no significant differences in habitat‐dependent sound transmission properties. We conclude that ecological niche segregation may explain acoustic divergence among the two wren subspecies. The resulting habitat‐dependent song divergence may have contributed to reproductive divergence by guiding assortative mating in parapatric conditions or just currently contribute to maintenance of reproductive isolation upon secondary contact.
Geographically variable selection inAmbystoma tigrinumvirus (Iridoviridae) throughout the western USA
Authors: RIDENHOUR B. J. , STORFER A. T. 
Published: April 2008

AbstractWe investigated spatially variable selection inAmbystoma tigrinumvirus (ATV) which causes frequent and geographically widespread epizootics of the tiger salamander,Ambystoma tigrinum. To test for evidence of selection, we sequenced several coding and noncoding regions from virus strains isolated from epizootics throughout western North America. Three of the sequenced regions contained homologues for genes putatively involved in host immune evasion and virulence: eIF‐2α, caspase activation and recruitment domain (CARD) and β‐OH‐steroid oxidoreductase. Selection analysis showed evidence of very strong purifying selection on eIF‐2α, purifying selection within certain viral clades on CARD and positive selection on β‐OH‐steroid oxidoreductase within certain clades. Analysis usingmultidivtimeand Tajima’s relative rate tests indicate accelerated rates of evolution within clades associated with anthropogenic movement. These clades also demonstrate greater spatial variability in selection, suggesting a lack of local adaptation (i.e. locally adapted populations should exhibit little to no selection because of absent or reduced variation in fitness once a fitness optimum is reached). Increased transfer of non‐native viral strains to naïve salamander populations, in conjunction with local maladaptation as a result of local selection pressures, may explain the spread and emergence of ATV epizootics inA. tigrinumin western North America.
Long‐lasting alteration in mesocorticolimbic structures after repeated social defeat stress in rats: time course of µ‐opioid receptor mRNA and FosB/ΔFosB immunoreactivity
Authors: Nikulina Ella M. , Arrillaga‐Romany Isabel , Miczek Klaus A. , Hammer Ronald P. 
Published: April 2008

AbstractSocial defeat stress is a salient stressor that induces neuroadaptive changes in the mesocorticolimbic dopaminergic system. Substantial evidence indicates that µ‐opioid receptors (MORs) modulate dopamine transmission in the ventral tegmental area (VTA). FosB/ΔFosB protein accumulation in dopaminergic projections during repeated treatments is thought to be involved in long‐term neuroplasticity. In this study we characterize the magnitude and time‐course of MOR mRNA expression and FosB/ΔFosB immunoreactivity in mesocorticolimbic regions following repeated social defeat stress. Effects of brief repeated social defeat stress or control handling procedures were studied in rats either 2 h after the last exposure, or 3, 7, 14, 21 and 28 days later. We found that MOR mRNA expression in the VTA doubled after the last stress compared with handling, and remained 30–70% higher until day 21. The number of FosB/ΔFosB‐labeled neurons in regions of the frontal cortex, nucleus accumbens (NAc) shell and core, and in the medial, central and basolateral amygdala increased significantly immediately after the last stress episode, and remained enhanced for 21 days. Another group of rats received bilateral intra‐VTA infusion of the MOR agonist, DAMGO, 7 days after the last stress. Prior social defeat stress augmented DAMGO‐induced Fos expression in the NAc shell, suggesting that Fos expression in this region might be the direct result of MOR activity in the VTA. Social defeat stress leads to an increased capacity for MOR activation in the VTA, which may be relevant to enduring FosB/ΔFosB expression in mesocorticolimbic areas and to the behaviorally sensitized response to psychostimulant drugs.
Emergence of spatial impairment in rats following specific cholinergic depletion of the medial septum combined with chronic stress
Authors: Craig Laura A. , Hong Nancy S. , Kopp Joelle , McDonald Robert J. 
Published: April 2008

AbstractA consistent finding in patients suffering from Alzheimer's disease is a loss of the cholinergic neurons of the basal forebrain that project to the hippocampus. However, the role this depletion plays in the development of Alzheimer's disease remains unclear. The loss of this ascending neurotransmitter system could potentially render hippocampal neurons more susceptible to further insult, such as chronic stress, ultimately resulting in neuronal death and memory loss. We explored this possibility by using the highly specific toxin 192 IgG‐Saporin to destroy the majority of cholinergic activity in the septo‐hippocampal pathway in rats. Following depletion, rats were subjected to 2 weeks of restraint stress. Rats were divided into two groups and were tested either on a hippocampal‐dependent (water maze) task or a hippocampal‐independent task (fear conditioning to tone and context). We showed that cholinergic depletion or stress alone had no effect on the successful performance of either of the tasks. However, rats with a combination of cholinergic depletion and stress were significantly impaired on the water‐maze task. No deficits were apparent in the combined group that was tested on fear conditioning to tone or context, suggesting that this impairment is specific to spatial working memory. These rats had no obvious hippocampal neuronal loss or damage; however, there were likely subtle changes in hippocampal processing that led to the observed deficit on the hippocampal‐dependent task. These findings support our theory that cholinergic depletion of the medial septum increases hippocampal vulnerability to further insults such as stress.
Changes in effective connectivity of human superior parietal lobule under multisensory and unisensory stimulation
Authors: Moran R. J. , Molholm S. , Reilly R. B. , Foxe J. J. 
Published: April 2008

AbstractPrevious event‐related potential (ERP) studies have identified the superior parietal lobule (SPL) as actively multisensory. This study compares effective, or contextually active, connections to this region under unisensory and multisensory conditions. Effective connectivity, the influence of one brain region over another, during unisensory visual, unisensory auditory and multisensory audiovisual stimulation was investigated. ERPs were recorded from subdural electrodes placed over the parietal lobe of three patients while they conducted a rapid reaction‐time task. A generative model of interacting neuronal ensembles for ERPs was inverted in a scheme allowing investigation of the connections from and to the SPL, a multisensory processing area. Important features of the ensemble model include inhibitory and excitatory feedback connections to pyramidal cells and extrinsic input to the stellate cell pool, with extrinsic forward and backward connections delineated by laminar connection differences between ensembles. The framework embeds the SPL in a plausible connection of distinct neuronal ensembles mirroring the integrated brain regions involved in the response task. Bayesian model comparison was used to test competing feed‐forward and feed‐backward models of how the electrophysiological data were generated. Comparisons were performed between multisensory and unisensory data. Findings from three patients show differences in summed unisensory and multisensory ERPs that can be accounted for by a mediation of both forward and backward connections to the SPL. In particular, a negative gain in all forward and backward connections to the SPL from other regions was observed during the period of multisensory integration, while a positive gain was observed for forward projections that arise from the SPL.
Functional similarities between the P1 component and alpha oscillations
Authors: Freunberger Roman , Höller Yvonne , Griesmayr Birgit , Gruber Walter , Sauseng Paul , Klimesch Wolfgang 
Published: April 2008

AbstractThe present study attempts to demonstrate functional similarities between the P1 component of event‐related potentials and alpha oscillations that are predicted by the ‘alpha inhibition‐timing’ hypothesis. On the basis of findings showing that the frequency characteristic of the P1 component lies in the alpha range and that alpha oscillation is functionally associated with inhibition, we predict that the P1 component also reflects inhibitory processes. This hypothesis is tested in two experiments, a spatial‐cuing task and a visual‐semantic categorization task. The results of the cuing task demonstrate that in a similar way as alpha power, the P1 component is larger over task‐irrelevant ipsilateral sites. For the categorization task, we found that the P1 component, in a similar way to alpha oscillations, is larger for task‐irrelevant, distorted pictures. We conclude that the P1 component may be generated at least in part by evoked alpha oscillations and reflects inhibition in the sense of suppressing task‐irrelevant processes.
13‐cis‐retinoic acid alters the cellular morphology of slice‐cultured serotonergic neurons in the rat
Authors: Ishikawa Junko , Sutoh Chihiro , Ishikawa Akinori , Kagechika Hiroyuki , Hirano Hitoshi , Nakamura Shoji 
Published: April 2008

AbstractRetinoids influence cellular processes such as differentiation, proliferation and apoptosis via retinoic acid receptor (RAR) and retinoid X receptor (RXR), and have therapeutic applications in several cancers and dermatologic diseases. Recent reports indicate that depression occasionally occurs in patients using the acne drug Accutane, the active component of which is 13‐cis‐retinoic acid (13‐cis‐RA). Although impairment of serotonin (5‐HT)‐expressing neurons, including morphologic changes, is thought to be associated with depressive symptoms, the effects of 13‐cis‐RA on 5‐HT neurons have not been examined. The present study demonstrated that 13‐cis‐RA alters the morphology of 5‐HT neurons in cultured rat midbrain slices. The 13‐cis‐RA‐induced changes were partially blocked by RXR and RAR antagonists. Furthermore, cotreatment with RAR and RXR agonists altered the morphology of 5‐HT neurons to a greater extent than the individual application of each agonist. The morphologic changes were completely blocked by RXR antagonist, whereas RAR antagonist partially blocked the effects. These results suggest that 13‐cis‐RA exerts its action on slice‐cultured 5‐HT neurons, at least in part, through specific retinoid receptors. Moreover, RXR has a greater influence on the morphology of 5‐HT neurons than RAR. The receptor‐mediated actions of 13‐cis‐RA presented here may provide a clue for further research on depression associated with the use of 13‐cis‐RA.
Disentangling neural structures for processing of high‐ and low‐speed visual motion
Authors: Lorteije Jeannette A. M. , Van Wezel Richard J. A. , Van Der Smagt Maarten J. 
Published: April 2008

AbstractHuman psychophysical and electrophysiological evidence suggests at least two separate visual motion pathways, one tuned to a lower and one tuned to a broader and partly overlapping range of higher speeds. It remains unclear whether these two different channels are represented by different cortical areas or by sub‐populations within a single area. We recorded evoked potentials at 59 scalp locations to the onset of a slow (3.5°/s) and fast (32°/s) moving test pattern, preceded by either a slow or fast adapting pattern that moved in either the same direction or opposite to the test motion. Baseline potentials were recorded for slow and fast moving test patterns after adaptation to a static pattern. Comparison of adapted responses with baseline responses revealed that the N2 peak around 180 ms after test stimulus onset was modulated by the preceding adaptation. This modulation depended on both direction and speed. Source localization of baseline potentials as well as direction‐independent motion adaptation revealed cortical areas activated by fast motion to be more dorsal, medial and posterior compared with neural structures underlying slow motion processing. For both speeds, the direction‐dependent component of this adaptation modulation occurred in the same area, located significantly more dorsally compared with neural structures that were adapted in a direction‐independent manner. These results demonstrate for the first time the cortical separation of more ventral areas selectively activated by visual motion at low speeds (and not high speeds) and dorsal motion‐sensitive cortical areas that are activated by both high and low speeds.
Functional analysis of human CNGA3 mutations associated with colour blindness suggests impaired surface expression of channel mutants A3R427C and A3R563C
Authors: Koeppen Katja , Reuter Peggy , Kohl Susanne , Baumann Britta , Ladewig Thomas , Wissinger Bernd 
Published: April 2008

AbstractMutations in the CNGA3 gene have been associated with complete and incomplete forms of total colour blindness (achromatopsia), a disorder characterized by reduced visual acuity, lack of colour discrimination, photophobia and nystagmus. CNGA3 encodes the A‐subunit of the cone photoreceptor cyclic nucleotide‐gated (CNG) channel, an essential component of the phototransduction cascade. Here we report the identification of three new CNGA3 mutations in patients with achromatopsia. To assess the pathogenicity of these newly identified and four previously reported mutations, mutant CNGA3 channels were heterologously expressed in a human embryonic kidney cell line (HEK293 cells) and functionally analysed using calcium imaging. Channels with the mutations R427C and R563C showed a response in imaging experiments and were subsequently characterized in‐depth with the patch‐clamp technique. The mutant channels were analysed as homooligomers and also as heterooligomers with the wild‐type B‐subunit present in native channels. Overall, cyclic guanosine monophosphate (cGMP) maximum currents of mutant channels were profoundly reduced in homo‐ and heteromers. Treatment with the chemical chaperone glycerol effectively increased macroscopic currents, presumably by enhancing surface expression of mutant channels as confirmed by immunocytochemistry. These results suggest decreased channel density in the cell membrane due to impaired folding or trafficking of the channel protein as the main pathogenic effect of the mutations R427C and R563C. Moreover, A3R427C homomers showed distinctly increased cGMP and cyclic adenosine monophosphate (cAMP) sensitivities as well as cAMP fractional currents that were raised to over 90% of cGMP maximum currents. Co‐expression of A3R427C with the B3 subunit compensated for most of these aberrant properties, apart from the reduced cGMP maximum currents.
Mechanical lesion activates newly identified NFATc1 in primary astrocytes: implication of ATP and purinergic receptors
Authors: Pérez‐Ortiz José M. , Serrano‐Pérez María C. , Pastor María D. , Martín Eduardo D. , Calvo Soledad , Rincón Mercedes , Tranque Pedro 
Published: April 2008

AbstractCa2+‐dependent calcineurin is upregulated in reactive astrocytes in neuroinflammatory models. Therefore, the fact that the nuclear factor of activated T cells (NFAT) is activated in response to calcineurin qualifies this family of transcription factors with immune functions as candidates to mediate astrogliosis. Brain trauma induces a neuroinflammatory state in which ATP is released from astrocytes, stimulating calcium signalling. Our goal here is to characterize NFATc1 and NFATc2 in mouse primary astrocyte cultures, also exploring the implication of NFAT in astrocyte activation by mechanical lesion. Quantitative reverse transcriptase‐polymerase chain reaction, Western blot analysis and immunofluorescence microscopy identified NFATc1 in astrocytes, but not NFATc2. Moreover, NFATc1 was expressed in the cytosol of resting astrocytes, whereas activation of the Ca2+‐calcineurin pathway by ionomycin translocated NFATc1 to the nucleus, which is a requirement for activation. The implication of astrocytic NFAT in brain trauma was analysed using an in vitro scratch lesion model. Mechanical lesion caused a rapid NFATc1 translocation that progressed throughout the culture as a gradient and was maintained for at least 4 h. We also demonstrate that ATP, released by lesion, is a potent inducer of NFATc1 translocation and activation. Moreover, the use of P2Y receptor modulators showed that such ATP action is mediated by stimulation of several Gq‐protein‐coupled P2Y purinergic receptors, among which P2Y1 and P2Y6 are included. In conclusion, this work provides evidence that newly identified NFATc1 is translocated in astrocytes in response to lesion following a pathway that involves ATP release and activation of metabotropic purinergic receptors.
Motor learning affects visual movement perception
Authors: Engel Annerose , Burke Michael , Fiehler Katja , Bien Siegfried , Rösler Frank 
Published: April 2008

AbstractIn the present study we investigated whether imitation of artificial movement trajectories of meaningless objects has an effect on how these trajectories are later perceptually processed within the human brain. During observation of a sequence of artificial object movements 10 participants (experimental group) actively imitated the trajectories during motor training and 10 participants (control group) solved a working memory task without motor training. The haemodynamic responses were recorded before and after the intervention while participants observed the movements and either had to detect colour changes of one of the objects (colour task, motor‐irrelevant) or had to judge whether the movement pattern could be imitated with the hands (simulation judgement task, motor‐relevant). The between‐group comparison of the post‐intervention haemodynamic responses revealed stronger activity for the motor training than for the control group during the simulation judgement task. This activity appeared in motor‐related areas (supplementary motor area and inferior parietal lobe) and in the occipito‐temporal area. During the colour task, the motor training group showed stronger activity in the occipital lobe. The control group did not reveal any stronger activity than the motor training group for either task. The results suggest that motor training has task‐specific effects on neural processes that are involved in perception of movements. Furthermore, they indicate that motor‐related areas are triggered by observed artificial object movements, but only if a motor‐relevant task is pursued.
Augmented brain 5‐HT crosses the blood–brain barrier through the 5‐HT transporter in rat
Authors: Nakatani Yasushi , Sato‐Suzuki Ikuko , Tsujino Naohisa , Nakasato Akane , Seki Yoshinari , Fumoto Masaki , Arita Hideho 
Published: April 2008

AbstractThe present study re‐evaluated an existing notion that serotonin (5‐hydroxytryptamine; 5‐HT) could not cross the brain to the circulating blood via the blood–brain barrier (BBB). To elevate brain 5‐HT alone, 5‐hydroxytryptophan (5‐HTP; 30–75 mg/kg) was administrated intravenously to anaesthetized rats that had undergone gastrointestinal and kidney resections along with liver inactivation (organs contributing to increasing blood 5‐HT after 5‐HTP administration). A microdialysis method and HPLC system were used to determine the brain 5‐HT levels in samples collected from the frontal cortex. Blood 5‐HT levels were determined from whole blood, not platelet‐poor plasma, collected from the central vein. We found that blood 5‐HT levels showed a significant augmentation whenever brain 5‐HT levels were significantly elevated after the administration of 5‐HTP in those rats with the abdominal surgical procedures. This elevation was abolished after pretreatment with a selective serotonin reuptake inhibitor (fluoxetine; 10 mg/kg i.v.), although brain 5‐HT levels remained augmented. These results indicate that augmented brain 5‐HT can cross the BBB through the 5‐HT transporter from the brain to the circulating blood.
Membrane properties of excitatory and inhibitory neurons in the rat prepositus hypoglossi nucleus
Authors: Shino Masato , Ozawa Seiji , Furuya Nobuhiko , Saito Yasuhiko 
Published: April 2008

AbstractThe prepositus hypoglossi nucleus (PHN) is thought to be a neural structure involved in transforming eye or head velocity signals into eye position signals for horizontal eye movements. In this study, we investigated the relationship between electrophysiological membrane properties and expression patterns of cellular markers for excitatory and inhibitory neurons by whole‐cell patch clamp recordings followed by reverse transcription polymerase chain reaction (RT‐PCR) analysis in rat brainstem slices. Three types of voltage response properties, namely afterhyperpolarization (AHP), firing pattern, and response to hyperpolarizing current pulses, were characterized in each neuron. Following RT‐PCR analysis, we identified PHN neurons as either glutamatergic (n = 22) or GABAergic (n = 43), although a small number of cholinergic (n = 2) and glycinergic neurons (n = 1) were also identified. Both glutamatergic and GABAergic neurons showed a wide variety of membrane properties; however, we found several characteristic relationships between neuronal type and membrane properties. Most neurons exhibiting (i) AHP without a slow component, (ii) a firing pattern with a delay in the generation of the first spike, (iii) a firing pattern with a transient burst and (iv) a firing pattern with a prolonged initial interspike interval were GABAergic. On the other hand, glutamatergic neurons were primarily characterized by a low firing rate. These results indicate that there is a close relationship between specific electrophysiological membrane properties and expression of chemical markers in some types of glutamatergic and GABAergic PHN neurons.