bluuebunny/crossref_metadata_2025_split huggingface dataset:
Both α2 and α3 GABAA receptor subtypes mediate the anxiolytic properties of benzodiazepine site ligands in the conditioned emotional response paradigm
Authors: Morris H. V. , Dawson G. R. , Reynolds D. S. , Atack J. R. , Stephens D. N. 
Published: May 2006

AbstractMice with point‐mutated α2 GABAA receptor subunits (rendering them diazepam insensitive) are resistant to the anxiolytic‐like effects of benzodiazepines (BZs) in unconditioned models of anxiety. We investigated the role of the α2 GABAA subtype in a model of conditioned anxiety. α2(H101R) and wildtype mice were trained in a conditioned emotional response (CER) task, in which lever‐pressing for food on a variable interval (VI) schedule was suppressed during the presentation of a conditioned stimulus (CS+) that predicted footshock. The ability of diazepam, ethanol and pentobarbital to reduce suppression during the CS+ was interpreted as an anxiolytic response. Diazepam (0, 0.5, 1, 2, 4 and 8 mg/kg) induced a dose‐dependent anxiolytic‐like effect in wildtype mice. At high doses, diazepam (2, 4 and 8 mg/kg) was sedative in α2(H101R) mice. Analysis of the anxiolytic properties of nonsedative diazepam doses (0.5 and 1 mg/kg), showed that α2(H101R) mice were resistant to the anxiolytic effects of diazepam. Equivalent anxiolytic properties of pentobarbital (20 mg/kg) and ethanol (1 and 2 g/kg) were seen in both genotypes. These findings confirm the critical importance of the α2 GABAA subtype in mediating BZ anxiolysis. However, as a compound, L‐838417, with agonist properties at α2, α3 and α5‐containing receptors, gave rise to anxiolytic‐like activity in α2(H101R) mice in the CER test, α3‐containing GABA receptors are also likely to contribute to anxiolysis. Observations that α2(H101R) mice were more active, and displayed a greater suppression of lever pressing in response to fear‐conditioned stimuli than wildtype mice, suggests that the α2(H101R) mutation may not be behaviourally silent.
Semaphorin3A regulates synaptic function of differentiated hippocampal neurons
Authors: Bouzioukh Farima , Daoudal Gaël , Falk Julien , Debanne Dominique , Rougon Geneviève , Castellani Valérie 
Published: May 2006

AbstractSemaphorins are major chemorepellents for developing neuronal projections. Their persistent expression at adult stages suggests that they may contribute to the functioning of neuronal circuits. We investigated the functional properties of semaphorin3A (Sema3A) in adult hippocampal neurons, and report that exogenous application of this cue decreases the efficacy of synaptic transmission evoked in the CA1 region of hippocampal slices. In situ hybridization, imaging and biochemical techniques showed that the Sema3A receptor component neuropilin‐1 is present at hippocampal synapses and localizes in the presynaptic membrane. In differentiated cultured hippocampal neurons, Sema3A elicited Erk1/2 phosphorylation in somata and neuritic compartments. Furthermore, Sema3A application resulted in a striking reduction of synaptophysin and postsynaptic density 95 puncta without affecting the axon diameter. These observations reveal novel functional potentialities for secreted semaphorins, which suggest that these cues could modulate the morphology and function of synapses in the adult brain.
Neuroprotective properties of memantine in different in vitro and in vivo models of excitotoxicity
Authors: Volbracht Christiane , Van Beek Johan , Zhu Changlian , Blomgren Klas , Leist Marcel 
Published: May 2006

AbstractThe pathogenesis of stroke, trauma and chronic degenerative diseases, such as Alzheimer's disease (AD), has been linked to excitotoxic processes due to inappropriate stimulation of the N‐methyl‐d‐asparate receptor (NMDA‐R). Attempts to use potent competitive NMDA‐R antagonists as neuroprotectants have shown serious side‐effects in patients. As an alternative approach, we were interested in the anti‐excitotoxic properties of memantine, a well‐tolerated low affinity uncompetitive NMDA‐R antagonist presently used as an anti‐dementia agent. We explored in a series of models of increasing complexity, whether this voltage‐dependent channel blocker had neuroprotective properties at clinically relevant concentrations. As expected, memantine protected neurons in organotypic hippocampal slices or dissociated cultures from direct NMDA‐induced excitotoxicity. However, low concentrations of memantine were also effective in neuronal (cortical neurons and cerebellar granule cells) stress models dependent on endogenous glutamate stimulation and mitochondrial stress, i.e. exposure to hypoxia, the mitochondrial toxin 1‐methyl‐4‐phenylpyridinium (MPP+) or a nitric oxide (NO) donor. Furthermore, memantine reduced lethality and brain damage in vivo in a model of neonatal hypoxia‐ischemia (HI). Finally, we investigated functional rescue (neuronal capacity to migrate along radial glia) by memantine in cerebellar microexplant cultures exposed to the indirect excitotoxin 3‐nitropropionic acid (3‐NP). Potent NMDA‐R antagonists, such as (+)MK‐801, are known to block neuronal migration in microexplant cultures. Interestingly, memantine significantly restored the number of neurons able to migrate out of the stressed microexplants. These findings suggest that inhibition of the NMDA‐R by memantine is sufficient to block excitotoxicity, while still allowing some degree of signalling.
MDMA and fenfluramine reduce L‐DOPA‐induced dyskinesia via indirect 5‐HT1A receptor stimulation
Authors: Bishop Christopher , Taylor Jennifer L. , Kuhn Donald M. , Eskow Karen L. , Park John Y. , Walker Paul D. 
Published: May 2006

AbstractChronicl‐3,4‐dihydroxyphenylalanine (L‐DOPA) pharmacotherapy in Parkinson's disease is often accompanied by the development of abnormal and excessive movements known as dyskinesia. Clinical and experimental studies indicate that indirect serotonin agonists can suppress dyskinesia without affecting the efficacy of L‐DOPA. While the mechanism by which these effects occur is not clear, recent research suggests that serotonin 5‐HT1A receptors may play a pivotal role. To test this, male Sprague–Dawley rats with unilateral 6‐hydroxydopamine medial forebrain bundle lesions received 1 week of daily treatment with L‐DOPA (12 mg/kg, i.p.) plus benserazide (15 mg/kg, i.p.). Beginning on the 8th day of treatment and every 3rd or 4th day thereafter, rats were pretreated with vehicle (0.9% NaCl), the serotonin and dopamine releaser 3,4‐methylenedioxymethamphetamine (MDMA; 0.25 or 2.5 mg/kg, i.p.) or the serotonin releaser fenfluramine (FEN; 0.25 or 2.5 mg/kg, i.p.) 5 min prior to L‐DOPA, after which abnormal involuntary movements (AIMs) and rotations were quantified every 20th minute for 2 h. Pretreatment with 2.5 mg/kg of either MDMA or FEN reduced AIMs. To determine the contribution of the 5‐HT1A receptor to these effects, another group of L‐DOPA‐primed 6‐hydroxydopamine‐lesioned rats were pretreated with the 5‐HT1A antagonist WAY100635 (0.5 mg/kg, i.p.), MDMA + WAY100635 (2.5 + 0.5 mg/kg, i.p.) or FEN + WAY100635 (2.5 + 0.5 mg/kg, i.p.) 5 min prior to L‐DOPA and subsequent AIMs and rotation tests. The antidyskinetic effects of MDMA and FEN were reversed by cotreatment with WAY100635. These results suggest that 5‐HT‐augmenting compounds such as MDMA and FEN probably convey antidyskinetic properties in part via stimulation of 5‐HT1A receptors.
Membrane traffic in outer hair cells of the adult mammalian cochlea
Authors: Kaneko Toshihiko , Harasztosi Csaba , Mack Andreas F. , Gummer Anthony W. 
Published: May 2006

AbstractOuter hair cells (OHCs), the sensory‐motor cells responsible for the extraordinary frequency selectivity and dynamic range of the cochlea, rapidly endocytose membrane and protein at their apical surface. Endocytosis and transcytosis in isolated OHCs from the mature guinea‐pig cochlea were investigated using the amphiphatic membrane probe FM1‐43. We observed membrane transport from the apical surface to both the basolateral wall and the subnuclear pole. By double‐labelling with DiOC6, a stain for endoplasmic reticulum, and aspiration of the plasma membrane, we showed that the basolateral target was the subsurface cisternae. The fluorescent signal was about three times weaker at the basal than at the apical pole. The speed of vesicle transport to the subnuclear pole was approximately 0.4 µm/s. Changing extracellular Ca2+ concentration from 25 µm to 2 mm accelerated rapid endocytosis. Extracellular application of BAPTA‐AM (25 µm), an intracellular Ca2+ chelator, and TFP (20 µm), a specific inhibitor of calmodulin, reduced endocytic activity, as did depolarization of the whole cell. The presence of extracellular Cd2+ (200 µm), a Ca2+‐channel blocker, had no effect on the voltage dependence of endocytosis at the apical pole, and inhibited the voltage dependence at the subnuclear pole. These results suggest that rapid endocytosis is a Ca2+/calmodulin‐dependent process, with extracellular Ca2+ entering through voltage‐gated Ca2+ channels at the basal pole. The two distinct destinations of endocytosed membrane are consistent with the functional polarization of the OHC, with the basolateral wall being dedicated to electromechanical transduction and the subnuclear pole being dedicated to electrochemical transduction processes.
Nucleus incertus contribution to hippocampal theta rhythm generation
Authors: Nuñez A. , Cervera‐Ferri A. , Olucha‐Bordonau F. , Ruiz‐Torner A. , Teruel V. 
Published: May 2006

AbstractThe hippocampal theta rhythm is generated by the pacemaker activity of the medial septum‐diagonal band of Broca (MS/DBB) neurons. These nuclei are influenced by brainstem structures that modulate the theta rhythm. The aim of the present work is to determine whether the nucleus incertus (NI), which has important anatomical connections with the MS/DBB, contributes to the hippocampal theta rhythm generation in rats. Hippocampal field activity was recorded in urethane‐anaesthetized rats. Electrical stimulation of the NI not only evoked theta rhythm in the hippocampus, but also decreased the amplitude of delta waves. Unit recordings in the NI revealed either a non‐rhythm discharge pattern in most neurons (76%), or a rhythm activity at 13–25 Hz in the remaining neurons. The firing rate of these neurons increased during the presence of theta rhythm evoked by either sensory or reticularis pontis oralis nucleus (RPO) stimulation. Electrolytic lesions of NI, or the microinjection of the γ‐aminobutyric acid (GABA)A agonist muscimol, abolished the theta rhythm evoked by RPO stimulation. Consequently, the NI may be a relay station between brainstem structures and the MS/DBB in the control of the hippocampal theta rhythm generation.
Identification of disabled‐1 as a candidate gene for critical period neuroplasticity in cat and mouse visual cortex
Authors: Yang Cui Bo , Zheng Yu Ting , Kiser Paul J. , Mower George D. 
Published: May 2006

AbstractRearing in darkness slows the time course of the critical period in visual cortex, such that at 5 weeks of age normal cats are more plastic than dark‐reared cats, whereas at 20 weeks dark‐reared cats are more plastic [G. D. Mower (1991)Dev. Brain Res., 58, 151–158]. Thus, a stringent criterion is that genes that are important for plasticity in visual cortex will show differences in expression between normal and dark‐reared visual cortex that are of opposite direction in young vs. older animals. The present study reports the identification by differential display PCR of Dab‐1, the mammalian homolog of the drosophila disabled‐1 gene, as a candidate gene for critical period neuronal plasticity, expression of which is regulated according to this criterion in cat visual cortex. Evidence for this bidirectional direction regulation is extended to Dab‐1 protein in cat and mouse visual cortex and shown to be specific to visual cortex, not occurring in frontal cortex. The Reelin/Dab‐1 pathway has well‐documented functions in cell migration during prenatal life and increasing evidence indicates that in postnatal brain the pathway plays a role in synaptic plasticity. The present results extend this evidence by directly implicating Dab‐1 in postnatal critical period plasticity of visual cortex.
Taxa–area relationships for microbes: the unsampled and the unseen
Authors: Woodcock Stephen , Curtis Thomas P. , Head Ian M. , Lunn Mary , Sloan William T. 
Published: May 2006

AbstractThe recent observation of a power–law relationship, S ∝ Az, between number of taxa, S, and area, A, for microbial eukaryotes and bacteria suggests that this is one of the few generic relationships in ecology, applicable to plants, animals and microbes. However, the rate of increase in the number of species with area varies from approximately the fourth (z = 0.26) to as little as the 50th root (z = 0.0019) in microbes. This is an enormous range for which no quantitative explanation has been proffered. We show by sampling from synthetic populations that the disparity between sample and community sizes in microbial community surveys means z can be considerably underestimated and accrual of rare taxa with increasing area will not be detectable. Significant microbial taxa–area relationships will only be observed when changes in community structure within samples correlate with area. Thus, the very low z values observed recently cannot be used as the sole evidence in support of any particular community theory of community assembly. More generally, this suggests that our search for patterns and laws in the microbial world will be profoundly influenced and, potentially distorted by the sample sizes that are typical of microbial community surveys.
Phylogeny, physiology and distribution of ‘Candidatus Microthrix calida’, a new Microthrix species isolated from industrial activated sludge wastewater treatment plants
Authors: Levantesi Caterina , Rossetti Simona , Thelen Karin , Kragelund Caroline , Krooneman Janneke , Eikelboom Dick , Nielsen Per Halkjær , Tandoi Valter 
Published: May 2006

SummaryTwelve strains of filamentous bacteria morphologically identified as ‘Microthrix parvicella’ were isolated from industrial activated sludge wastewater treatment plants. 16S rRNA gene sequences analysis showed that these strains were all closely related to ‘Candidatus Microthrix parvicella’. Six of them, however, had a 16S rRNA gene similarity of only 95.7% and 96.7% to ‘Candidatus Microthrix parvicella’ suggesting the presence of a new species. The name ‘Candidatus Microthrix calida’ is proposed for this new microorganism. The physiological properties of these six isolates supported the description of a new taxon. The ‘Candidatus Microthrix calida’ strains produced thin filaments (0.3–0.7 µm diameter), they did not grow on the media supporting the growth of ‘Candidatus Microthrix parvicella’ and could be cultivated at higher temperature (up to 36.5°C). Preliminary data on substrate uptake were obtained by microautoradiography on pure culture. Two new fluorescence in situ hybridization (FISH) probes, Mpa‐T1‐1260 specific for ‘Candidatus Microthrix calida’ and Mpa‐all‐1410 targeting both Microthrix species, were designed. The presence of Microthrix spp. was investigated in 114 activated sludge plants. ‘Microthrix parvicella’ morphotype was detected in 23% of the analysed samples and FISH analysis revealed that ‘Candidatus Microthrix calida’ was present in 5% of them. The remaining ‘M. parvicella’ filaments were positive with probe Mpa‐all‐1410 but could not all be identified as ‘Candidatus Microthrix parvicella’ suggesting the presence of more hitherto undescribed biodiversity within this morphotype.
The Effects of Income Imputation on Microanalyses: Evidence from the European Community Household Panel
Authors: Nicoletti Cheti , Peracchi Franco 
Published: May 2006

SummarySocial surveys are usually affected by item and unit non-response. Since it is unlikely that a sample of respondents is a random sample, social scientists should take the missing data problem into account in their empirical analyses. Typically, survey methodologists try to simplify the work of data users by ‘completing’ the data, filling the missing variables through imputation. The aim of the paper is to give data users some guidelines on how to assess the effects of imputation on their microlevel analyses. We focus attention on the potential bias that is caused by imputation in the analysis of income variables, using the European Community Household Panel as an illustration.
Sibling Death Clustering in India: State DependenceVersusUnobserved Heterogeneity
Authors: Arulampalam Wiji , Bhalotra Sonia 
Published: May 2006

SummaryData from a range of environments indicate that the incidence of death is not randomly distributed across families but, rather, that there is a clustering of death among siblings. A natural explanation of this would be that there are (observed or unobserved) differences across families, e.g. in genetic frailty, education or living standards. Another hypothesis that is of considerable interest for both theory and policy is that there is a causal process whereby the death of a child influences the risk of death of the succeeding child in the family. Drawing language from the literature on the economics of unemployment, the causal effect is referred to here as state dependence (or scarring). The paper investigates the extent of state dependence in India, distinguishing this from family level risk factors that are common to siblings. It offers some methodological innovations on previous research. Estimates are obtained for each of three Indian states, which exhibit dramatic differences in socio-economic and demographic variables. The results suggest a significant degree of state dependence in each of the three regions. Eliminating scarring, it is estimated, would reduce the incidence of infant mortality (among children who are born after the first child) by 9.8% in the state of Uttar Pradesh, 6.0% in West Bengal and 5.9% in Kerala.
Multilevel Modelling of Complex Survey Data
Authors: Rabe-Hesketh Sophia , Skrondal Anders 
Published: May 2006

SummaryMultilevel modelling is sometimes used for data from complex surveys involving multistage sampling, unequal sampling probabilities and stratification. We consider generalized linear mixed models and particularly the case of dichotomous responses. A pseudolikelihood approach for accommodating inverse probability weights in multilevel models with an arbitrary number of levels is implemented by using adaptive quadrature. A sandwich estimator is used to obtain standard errors that account for stratification and clustering. When level 1 weights are used that vary between elementary units in clusters, the scaling of the weights becomes important. We point out that not only variance components but also regression coefficients can be severely biased when the response is dichotomous. The pseudolikelihood methodology is applied to complex survey data on reading proficiency from the American sample of the ‘Program for international student assessment’ 2000 study, using the Stata program gllamm which can estimate a wide range of multilevel and latent variable models. Performance of pseudo-maximum-likelihood with different methods for handling level 1 weights is investigated in a Monte Carlo experiment. Pseudo-maximum-likelihood estimators of (conditional) regression coefficients perform well for large cluster sizes but are biased for small cluster sizes. In contrast, estimators of marginal effects perform well in both situations. We conclude that caution must be exercised in pseudo-maximum-likelihood estimation for small cluster sizes when level 1 weights are used.
Proximity and inter‐organizational collaboration: A literature review
Authors: Knoben J. , Oerlemans L.A.G. 
Published: May 2006

The proximity concept is used in many different ways in the literature. These dimensions of proximity are, however, defined and measured in many different (sometimes even contradictory) ways, show large amounts of overlap, and often are under‐ or over‐specified. The goal of this paper is to specify the different dimensions of proximity relevant in inter‐organizational collaboration more precisely and to provide definitions of these dimensions. The research presented contributes to reducing the ambiguity of the proximity concept as used in the literature.Based on the above, the following research question is addressed in this paper: ‘Which dimensions of proximity are relevant in inter‐organizational collaboration and how are they defined?’ A systematic literature review is presented in order to disentangle the dimensions of the proximity concept. Based on this literature review, three dimensions of proximity relevant in inter‐organizational collaboration are distinguished: geographical proximity, organizational proximity and technological proximity. Examples (case studies) from the literature are used to illustrate the current conceptual ambiguity as well as to clarify how the proposed dimensions of proximity reduce this conceptual ambiguity.
The effect of congenital deafness on duration judgment
Authors: Kowalska Joanna , Szelag Elzbieta 
Published: May 2006

Objective:  Congenital deafness provides the opportunity to study how atypical sensory and language experiences affect different aspects of information processing, e.g., time perception.Methods:  Using two methods of temporal estimation, reproduction (Exp. 1) and production (Exp. 2), the effect of deafness on duration judgment was investigated within a time domain of a few seconds. We examined 16 congenitally deaf adolescents, aged between 16 and 19 years, and 16 normally hearing subjects, matched for gender and age. In Exp. 1 subjects were asked to reproduce durations from 1 to 5.5 s, whereas in Exp. 2 they produced durations from 1 to 6 s.Results:  The results showed that in both experiments, the region of accurate estimation was significantly limited in deaf individuals, compared to normal hearing ones. Deaf adolescents judged accurately only intervals around 3 s, whereas they overestimated standards shorter than 2 s and underestimated those above 3 s. In contrast, controls correctly estimated the majority of standards applied in both experiments, with the exception of underreproduction of intervals longer than 3 s (Exp. 1).Conclusions:  The effect of deafness on the accuracy of duration judgment can be linked to differences in the use of conventional time units, applied strategy as well as cognitive processes such as attention or working memory.
Ten polymorphic tetranucleotide microsatellite markers isolated from the Anolis roquet series of Caribbean lizards
Authors: GOW JENNIFER L. , JOHANSSON HELENA , SURGET‐GROBA YANN , THORPE ROGER S. 
Published: May 2006

AbstractThe Anolis roquet series of Caribbean lizards provides natural replicates with which to examine the role of historical contingency and ecological determinism in shaping evolutionary patterns. Here, we describe 10 polymorphic tetranucleotide microsatellites to facilitate studies on population differentiation and gene flow. All loci successfully amplified in several species from this series. Genotyping 96 individuals from two A. roquet populations demonstrated the markers’ suitability as population genetic markers: genetic diversity was high (9–22 alleles per locus); there were no instances of linkage disequilibrium; and, with one exception, all genotypic frequencies conformed to Hardy–Weinberg equilibrium expectations.