bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential effect of endothelial nitric oxide synthase (NOS‐III) on the regulation of adult neurogenesis and behaviour
Authors: Reif Andreas , Schmitt Angelika , Fritzen Sabrina , Chourbaji Sabine , Bartsch Colin , Urani Alexandre , Wycislo Matthias , Mössner Rainald , Sommer Claudia , Gass Peter , Lesch Klaus‐Peter 
Published: August 2004

AbstractAlthough it has been postulated that adult neurogenesis, i.e. the generation of functional neurons from progenitor cells in the mammalian brain, is involved in both the pathogenesis of depressive disorders and the therapeutic effect of antidepressant drugs, its regulation is still poorly understood. Nitric oxide, a gaseous messenger molecule, represents a possible modulating agent as it is involved in learning and memory formation as well as synapto‐ and morphogenesis. Here we investigated whether adult neurogenesis is altered in mice lacking endothelial nitric oxide synthase (NOS‐III). Compared to wild‐type littermates, NOS‐III‐deficient mice showed a significant reduction in neuronal progenitor cell proliferation in the dentate gyrus, suggesting a role for NOS‐III in the stimulation of neuroneogenesis. NeuN, β‐III‐tubulin and GFAP double‐immunolabelling demonstrated that proliferating progenitor cells differentiate preferentially into neurons but not into astrocytes. However, when the survival rate of newly formed cells was examined no difference between wild‐type and NOS‐III knockout mice was found, suggesting that NOS‐III selectively exerts its effects on the proliferation of progenitor cells. This might be mediated by a decrease in vascular endothelial growth factor (VEGF) transcripts in the hippocampus of knockout animals. At the behavioural level, while NOS‐III knockout mice displayed better and faster learning in a learned helplessness paradigm, no depression‐like behaviours were observed. In conclusion, our results indicated that NOS‐III is involved in the proliferation of neuronal progenitor cells, although behavioural analysis does not provide evidence for a pro‐depressive effect of reduced neuroneogenesis.
Differential distribution of the KCl cotransporter KCC2 in thalamic relay and reticular nuclei
Authors: Barthó P. , Payne J. A. , Freund T. F. , Acsády L. 
Published: August 2004

AbstractIn the thalamus of the rat the reversal potential of GABA‐induced anion currents is more negative in relay cells than in neurones of the reticular nucleus (nRt) due to different chloride extrusion mechanisms operating in these cells. The distribution of KCl cotransporter type 2 (KCC2), the major neuronal chloride transporter that may underlie this effect, is unknown in the thalamus. In this study the precise regional and ultrastructural localization of KCC2 was examined in the thalamus using immunocytochemical methods. The neuropil of all relay nuclei was found to display intense KCC2 immunostaining to varying degrees. In sharp contrast, the majority of the nRt was negative for KCC2. In the anterior and dorsal part of the nRt, however, KCC2 immunostaining was similar to relay nuclei and parvalbumin and calretinin were found to colocalize with KCC2. At the ultrastructural level, KCC2 immunoreactivity was mainly located in the extrasynaptic membranes of thick and thin dendrites and the somata of relay cells but was also found in close association with asymmetrical synapses formed by cortical afferents. Quantitative evaluation of KCC2 distribution at the electron microscopic level demonstrated that the density of KCC2 did not correlate with dendritic diameter or synaptic coverage but is 1.7 times higher on perisynaptic membrane surfaces than on extrasynaptic membranes. Our data demonstrate that the regional distribution of KCC2 is compatible with the difference in GABA‐A reversal potential between relay and reticular nuclei. At the ultrastructural level, abundant extrasynaptic KCC2 expression will probably play a role in the regulation of extrasynaptic GABA‐A receptor‐mediated inhibition.
Disruption of the retinoid signalling pathway causes a deposition of amyloid β in the adult rat brain
Authors: Corcoran Jonathan P. T. , So Po Lin , Maden Malcolm 
Published: August 2004

AbstractWe have disrupted the retinoid signalling pathway in adult rats by a dietary deficiency of vitamin A. After 1 year of this dietary deficiency, there was a deposition of amyloid β in the cerebral blood vessels. There is a downregulation of retinoic acid receptor α in the forebrain neurons of the retinoid‐deficient rats and a loss of choline acetyl transferase expression, which precedes amyloid β deposition. In neocortex of pathology samples of patients with Alzheimer's disease, the same retinoic acid receptor α deficit in the surviving neurons was observed. We have identified the retinoid‐synthesizing enzymes involved in this process, retinaldehyde dehydrogenase‐2 and class IV alcohol dehydrogenase, only the former is downregulated in patients with Alzheimer's disease. This suggests that retinoids are important for the maintenance of the adult nervous system and their loss may in part play a role in Alzheimer's disease.
INaP underlies intrinsic spiking and rhythm generation in networks of cultured rat spinal cord neurons
Authors: Darbon Pascal , Yvon Cédric , Legrand Jean‐Christophe , Streit Jürg 
Published: August 2004

AbstractWe have shown previously that rhythm generation in disinhibited spinal networks is based on intrinsic spiking, network recruitment and a network refractory period following the bursts. This refractory period is based mainly on electrogenic Na/K pump activity. In the present work, we have investigated the role of the persistent sodium current (INaP) in the generation of bursting using patch‐clamp and multielectrode array recordings. We detected INaP exclusively in the intrinsic spiking cells. The blockade of INaP by riluzole suppressed the bursting by silencing the intrinsic spiking cells and suppressing network recruitment. The blockade of the persistent sodium current produced a hyperpolarization of the membrane potential of the intrinsic spiking cells, but had no effect on non‐spiking cells. We also investigated the involvement of the hyperpolarization‐activated cationic current (Ih) in the rhythmic activity. The bath application of ZD7288, a specific Ih antagonist, slowed down the rate of the bursts by increasing the interburst intervals. Ih was present in ∼ 70% of the cells, both in the intrinsic spiking cells as well as in the non‐spiking cells. We also found both kinds of cells in which Ih was not detected. In summary, in disinhibited spinal cord cultures, a persistent sodium current underlies intrinsic spiking, which, via recurrent excitation, generates the bursting activity. The hyperpolarization‐activated cationic current contributes to intrinsic spiking and modulates the burst frequency.
Down‐regulation of nitrergic transmission in the rat striatum after chronic nigrostriatal deafferentation
Authors: Sancesario Giuseppe , Giorgi Mauro , D'Angelo Vincenza , Modica Anna , Martorana Alessandro , Morello Maria , Bengtson C. Peter , Bernardi Giorgio 
Published: August 2004

AbstractDopamine and NO are physiological stimulators of synthesis of cAMP and cGMP, respectively, and NO synthase‐containing interneurons in the striatum are physiologically activated by dopamine‐containing neurons in the substantia nigra. This study investigated whether lesioning dopamine neurons has multiple consequences in the striatum consistent with the reported sensitization of cAMP synthesis, including alteration of the NO–cGMP pathway and phosphodiesterase‐dependent metabolism of cyclic nucleotides. The substantia nigra of adult Sprague‐Dawley rats was unilaterally lesioned with 6‐hydroxydopamine. Two months later, we determined expression of NO synthase and evaluated cGMP and cAMP levels of intact and deafferented striatum. Moreover, we evaluated cAMP– and cGMP–phosphodiesterase activities in basal conditions and after Ca2+–calmodulin stimulation and determined the expression of the phosphodiesterase‐1B isoform and the levels of phosphodiesterase‐1B mRNA. Using immunocytochemistry we characterized the distribution of NO synthase and phosphodiesterase‐1B within striatal neurons. In the dopamine‐deafferented striatum, NO synthase levels were decreased by 42% while NO synthase‐immunopositive intrastriatal fibres but not NO synthase neuronal bodies were reduced in number. In the deafferented striatum basal cGMP levels were reduced, and cAMP levels were increased, but cGMP–phosphodiesterase and cAMP–phosphodiesterase activities were both increased in basal and Ca2+–calmodulin‐stimulated conditions. Accordingly, phosphodiesterase‐1B expression and phosphodiesterase‐1B mRNA were upregulated while a large population of medium‐sized striatal neurons showed increased phosphodiesterase‐1B immunoreactivity. Dopamine deafferentation led to a complex down‐regulation of the NO–cGMP pathway in the striatum and to an up‐regulation of phosphodiesterase‐1B‐dependent cyclic nucleotide metabolism, showing new aspects of neuronal plasticity in experimental hemiparkinsonism.
Bystin as a novel marker for reactive astrocytes in the adult rat brain following injury
Authors: Sheng Jiansong , Yang Shuo , Xu Lei , Wu Chunhua , Wu Xuefei , Li Aiqun , Yu Yi , Ni Hengjian , Fukuda Michiko , Zhou Jiawei 
Published: August 2004

AbstractBystin has been identified as a protein which mediates cellular interactions between trophoblastic and endometrial epithelial cells by forming complexes with two partners, trophinin and tastin, during embryo implantation. However, the presence of bystin in the central nervous system has not been demonstrated. Here, we report the cloning of the full‐length cDNA of the rat bystin gene from adult brain. Immunohistochemical and RT‐PCR analysis showed that the levels of bystin expression were markedly up‐regulated in the both 6‐hydrodopamine‐lesioned rat nigrostriatum and stab‐lesioned cerebral cortex in adult rats. Double immunofluorescence staining revealed that most bystin‐expressing glial cells were astrocytes (immature or mature). To determine the mechanisms for the up‐regulation of bystin expression in glial cells, primary cultures of postnatal cortical astrocytes were employed. Western blot analysis showed that the expression of bystin was elevated by treatment with pro‐inflammatory mediators lipopolysaccharide and interleukin‐1β. Nerve growth factor known to be released after brain injury also induced bystin expression in the cultures. Exposure of astrocyte cultures to the differentiating agent forskolin resulted in up‐regulation of bystin followed by a pronounced astrocytic stellation. The results suggest that the injury in the adult brain induces spatiotemporal up‐regulation of bystin and it could be influenced, at least in part, by elevation of intracellular cAMP level. Bystin expressed by reactive astrocytes may be involved in their differentiation during the inflammatory processes following brain injury. The reappearance of bystin may also indicate that some reactive astrocytes have the capacity to recapitulate early developmental stages.
Differential involvement of rat medial prefrontal cortex dopamine receptors in modulation of hypothalamic‐ pituitary‐adrenal axis responses to different stressors
Authors: Spencer S. J. , Ebner K. , Day T. A. 
Published: August 2004

AbstractRecent investigations have implicated the medial prefrontal cortex (mPFC) in modulation of subcortical pathways that contribute to the generation of behavioural, autonomic and endocrine responses to stress. However, little is known of the mechanisms involved. One of the key neurotransmitters involved in mPFC function is dopamine, and we therefore aimed, in this investigation, to examine the role of mPFC dopamine in response to stress in Wistar rats. In this regard, we infused dopamine antagonists SCH23390 or sulpiride into the mPFC via retrodialysis. We then examined changes in numbers of cells expressing the c‐fos immediate‐early gene protein product, Fos, in subcortical neuronal populations associated with regulation of hypothalamic‐pituitary‐adrenal (HPA) axis stress responses in response to either of two stressors; systemic injection of interleukin‐1β, or air puff. The D1 antagonist, SCH23390, and the D2 antagonist, sulpiride, both attenuated expression of Fos in the medial parvocellular hypothalamic paraventricular nucleus (mpPVN) corticotropin‐releasing factor cells at the apex of the HPA axis, as well as in most extra‐hypothalamic brain regions examined in response to interleukin‐1β. By contrast, SCH23390 failed to affect Fos expression in response to air puff in any brain region examined, while sulpiride resulted in an attenuation of the air puff‐induced response in only the mpPVN and the bed nucleus of the stria terminalis. These results indicate that the mPFC differentially processes the response to different stressors and that the two types of dopamine receptor may have different roles.
Differential activation of glomeruli in the ferret's main olfactory bulb by anal scent gland odours from males and females: an early step in mate identification
Authors: Woodley Sarah K. , Baum Michael J. 
Published: August 2004

AbstractPeripheral anosmia was previously found to disrupt sex discrimination and partner preference in male and female ferrets. Here we show directly that volatile anal scent gland odourants from male and female ferrets activated overlapping but distinguishable clusters of glomeruli located in the ventral–caudal portion of the main olfactory bulb (MOB) of breeding ferrets of both sexes. No glomerular activation was seen in the accessory olfactory bulb (AOB). The profile of MOB glomerular activation induced in oestrous females by male anal scents was very similar to that induced by direct contact with a male during mating, and oestrogen treatment failed to alter the profile of glomerular activation induced in ovo‐hysterectomized females by male anal scents. In rodents, ‘atypical’ MOB glomeruli, which have dense acetylcholinesterase (AChE) activity in the neuropil, may be activated by body odours from conspecifics. No such AChE‐staining ‘atypical’ glomeruli were found in the ferret's MOB, suggesting that in this carnivore they do not constitute a subset of MOB glomeruli that respond to body odourants. In ferrets of both sexes, volatile body odourants that are detected by the main as opposed to the vomeronasal–AOB accessory olfactory system may play a critical role in mate identification.
Long‐term but not short‐term blockade of dopamine release in Drosophila impairs orientation during flight in a visual attention paradigm
Authors: Ye Yizhou , Xi Wang , Peng Yueqing , Wang Yizheng , Guo Aike 
Published: August 2004

AbstractDopamine is a major neuromodulator in both vertebrates and invertebrates and has profound effects on many physiological processes, including the regulation of attention. Most studies of the functions of dopamine use models with long‐term blockade of dopamine release and few effects of transient blockade have yet been reported. The goal of the present study was to determine the role of dopamine in attention‐like behavior in Drosophila by taking advantage of the fly's orientation behavior during flight. The examination of several different transgenic flies in a single‐target visual attention paradigm showed that flies lost their orientation ability if dopamine release was blocked from the beginning of the development of dopaminergic neurons. This is similar to the attention loss in mammals. However, if the blockade of dopamine release was induced during the experimental procedure, flies performed normally. Statistical analysis of the behavioral assessment showed a significant difference between long‐term and transient blockade. Using the RNA interference approach, we generated flies with down‐regulated J‐domain protein, which is a potential cochaperone in synaptic vesicle release, to make an alternative form of long‐term dopamine‐blockade mutant. Behavioral assays revealed that flies with permanent J‐domain protein down‐regulation specifically in dopaminergic neurons have an attention defect similar to that induced by long‐term blockade of dopamine release. Furthermore, dopamine depletion beginning at eclosion also caused an attention deficit. Our results indicate that prolonged but not transient blockade of dopamine release impairs visual attention‐like behavior in Drosophila.
Targeting modular polyketide synthases with iteratively acting acyltransferases from metagenomes of uncultured bacterial consortia
Authors: Piel Jörn , Hui Dequan , Fusetani Nobuhiro , Matsunaga Shigeki 
Published: August 2004

SummaryBacterial type I polyketide synthases (PKSs) produce a wide range of biomedically important secondary metabolites. These enzymes possess a modular structure that can be genetically re‐engineered to yield novel drug candidates not found in nature. Recently, we have reported the putative pederin PKS from an uncultured bacterial symbiont of Paederus fuscipes beetles. It belongs to an architecturally unusual PKS group, the members of which contain iteratively acting acyltransferases that are not integrated into the PKS modules but are encoded by isolated genes. As these systems are rare, often contain additional unusual features and are of smaller size than regular PKSs, the development of a method for the targeted isolation of new group members would be of great interest. Here, we present a phylogenetic approach to identify these systems rapidly in highly complex metagenomic DNA samples. To demonstrate its practical value, we located two pederin‐type PKS systems putatively involved in the biosynthesis of antitumour polyketides in the metagenomic DNA of beetles, sponges and their uncultivated bacterial symbionts.
Suppressive subtractive hybridization as a tool for identifying genetic diversity in an environmental metagenome: the rumen as a model
Authors: Galbraith Elizabeth A. , Antonopoulos Dionysios A. , White Bryan A. 
Published: August 2004

SummaryMolecular techniques previously used for genome comparisons of closely related bacterial species could prove extremely valuable for comparisons of complex microbial communities, or metagenomes. Our study aimed to determine the breadth and value of suppressive subtractive hybridization (SSH) in a pilot‐scale analysis of metagenomic DNA from communities of microorganisms in the rumen. Suppressive subtractive hybridization was performed using total genomic DNA isolated from rumen fluid samples of two hay‐fed steers, arbitrarily designated as tester or driver. Ninety‐six subtraction DNA fragments from the tester metagenome were amplified, cloned and the DNA sequences were determined. Verification of the isolation of DNA fragments unique to the tester metagenome was accomplished through dot blot and Southern blot hybridizations. Tester‐specific SSH fragments were found in 95 of 96 randomly selected clones. DNA sequences of subtraction fragments were analysed by computer assisted DNA and amino acid comparisons. Putative translations of 26 (32.1%) subtractive hybridization fragments exhibited significant similarity to Bacterial proteins, whereas 15 (18.5%) distinctive subtracted fragments had significant similarity to proteins from Archaea. The remainder of the subtractive hybridization fragments displayed no similarity to GenBank sequences. This metagenomic approach has exposed an unexpectedly large difference in Archaeal community structure between the rumen microbial populations of two steers fed identical diets and housed together. 16S rRNA dot blot hybridizations revealed similar proportions of Bacteria and Archaea in both rumen samples and suggest that the differences uncovered by SSH are the result of varying community structural composition. Our study demonstrates a novel approach to comparative analyses of environmental microbial communities through the use of SSH.
Application of tetranucleotide frequencies for the assignment of genomic fragments
Authors: Teeling Hanno , Meyerdierks Anke , Bauer Margarete , Amann Rudolf , Glöckner Frank Oliver 
Published: August 2004

SummaryA basic problem of the metagenomic approach in microbial ecology is the assignment of genomic fragments to a certain species or taxonomic group, when suitable marker genes are absent. Currently, the (G +  C)‐content together with phylogenetic information and codon adaptation for functional genes is mostly used to assess the relationship of different fragments. These methods, however, can produce ambiguous results. In order to evaluate sequence‐based methods for fragment identification, we extensively compared (G + C)‐contents and tetranucleotide usage patterns of 9054 fosmid‐sized genomic fragments generated in silico from 118 completely sequenced bacterial genomes (40 982 931 fragment pairs were compared in total). The results of this systematic study show that the discriminatory power of correlations of tetranucleotide‐derived z‐scores is by far superior to that of differences in (G + C)‐content and provides reasonable assignment probabilities when applied to metagenome libraries of small diversity. Using six fully sequenced fosmid inserts from a metagenomic analysis of microbial consortia mediating the anaerobic oxidation of methane (AOM), we demonstrate that discrimination based on tetranucleotide‐derived z‐score correlations was consistent with corresponding data from 16S ribosomal RNA sequence analysis and allowed us to discriminate between fosmid inserts that were indistinguishable with respect to their (G + C)‐contents.
Construction, characterization, and use of small‐insert gene banks of DNA isolated from soil and enrichment cultures for the recovery of novel amidases
Authors: Gabor Esther M. , De Vries Erik J. , Janssen Dick B. 
Published: August 2004

SummaryTo obtain new amidases of biocatalytic relevance, we used microorganisms indigenous to different types of soil and sediment as a source of DNA for the construction of environmental gene banks, following two different strategies. In one case, DNA was isolated from soil without preceding cultivation to preserve a high degree of (phylo)genetic diversity. Alternatively, DNA samples were obtained from enrichment cultures, which is thought to reduce the number of clones required to find a target enzyme. To selectively sustain the growth of organisms exhibiting amidase activity, cultures were supplied with a single amide or a mixture of different aromatic and non‐aromatic acetamide and glycine amide derivatives as the only nitrogen source. Metagenomic DNA was cloned into a high‐copy plasmid vector and transferred to E. coli, and the resulting gene banks were searched for positives by growth selection. In this way, we isolated a number of recombinant E. coli strains with a stable phenotype, each expressing an amidase with a distinct substrate profile. One of these clones was found to produce a new and highly active penicillin amidase, a promising biocatalyst that may allow higher yields in the enzymatic synthesis of β‐lactam antibiotics.