bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mu‐ and delta‐opioid receptor antagonists decrease proliferation and increase neurogenesis in cultures of rat adult hippocampal progenitors
Authors: Persson Anders I. , Thorlin Thorleif , Bull Cecilia , Zarnegar Parisa , Ekman Rolf , Terenius Lars , Eriksson Peter S. 
Published: December 2004

AbstractOpioids have previously been shown to affect proliferation and differentiation in various neural cell types. In the present study, cultured rat adult hippocampal progenitors (AHPs) were shown to release β‐endorphin. Membrane preparations of AHPs were found to bind [125I]β‐endorphin, and immunoreactivity for mu‐ and delta‐opioid receptors (MORs and DORs), but not for kappa‐opioid receptors (KORs), was found on cells in culture. Both DNA content and [3H]thymidine incorporation were reduced after a 48‐h incubation with 100 µm naloxone, 10 µm naltrindole or 10 µmβ‐funaltrexamine, but not nor‐binaltorphimine, suggesting proliferative actions of endogenous opioids against MORs and DORs on AHPs. Furthermore, analysis of gene and protein expression after incubation with MOR and DOR antagonists for 48 h using RT‐PCR and Western blotting suggested decreased signalling through the mitogen‐activated protein kinase (MAPK) pathway and lowered levels of genes and proteins that are important in cell cycling. Cultures were incubated with naloxone (10 or 100 µm) for 10 days to study the effects on differentiation. This resulted in an approximately threefold increase in neurogenesis, a threefold decrease in astrogliogenesis and a 50% decrease in oligodendrogenesis. In conclusion, this study suggests that reduced signalling through MORs and DORs decreases proliferation in rat AHPs, increases the number of in vitro‐generated neurons and reduces the number of astrocytes and oligodendrocytes in culture.
Analysis of differential gene expression supports a role for amyloid precursor protein and a protein kinase C substrate (MARCKS) in long‐term memory
Authors: Solomonia R. O. , Morgan K. , Kotorashvili A. , McCabe B. J. , Jackson A. P. , Horn G. 
Published: December 2004

AbstractPrevious work has identified the intermediate and medial part of the hyperstriatum ventrale (IMHV) as a region of the chick brain storing information acquired through the learning process of imprinting. We have examined in this brain region changes in expression of candidate genes involved in memory. Chicks were exposed to a rotating red box and the strength of their preference for it, a measure of learning, determined. Brain samples were removed ≈24 h after training. Candidate genes whose expressions were different in IMHV samples derived from strongly imprinted chicks relative to those from chicks showing little or no learning were identified using subtractive hybridization. The translation products of two candidate genes were investigated further in samples from the left and right IMHV and from two other brain regions not previously implicated in imprinting, the left and right posterior neostriatum. One of the proteins was the amyloid precursor protein (APP), the other was myristoylated alanine rich C kinase substrate (MARCKS). In the left IMHV the levels of the two proteins increased with the strength of learning. The effects in the right IMHV were not significantly different from those in the left. There were no effects of learning in the posterior neostriatum. This is the first study to relate changes in the amounts of MARCKS and APP proteins to the strength of learning in a brain region known to be a memory store and demonstrates that the systematic identification of protein molecules involved in memory formation is possible.
D2 Dopamine receptor blockade results in sprouting of DA axons in the intact animal but prevents sprouting following nigral lesions
Authors: Tripanichkul W. , Stanic D. , Drago J. , Finkelstein D. I. , Horne M. K. 
Published: December 2004

AbstractRecently it was demonstrated that sprouting of dopaminergic neurons and a microglial and astrocyte response follows both partial lesions of the substantia nigra pars compacta and blockade of the D2 dopamine receptor. We therefore studied the effects of the combination of these two treatments (lesioning and D2 dopamine receptor blockade). Haloperidol administration caused a 57% increase in dopaminergic terminal tree size (measured as terminal density per substantia nigra pars compacta neuron) and an increase of glia in the striatum. Following small to medium nigral lesions (less than 60%), terminal tree size increased by 51% on average and returned density of dopaminergic terminals to normal. In contrast, administration of haloperidol for 16 weeks following lesioning resulted in reduced dopaminergic terminal density and terminal tree size (13%), consistent with absent or impaired sprouting. Glial cell numbers increased but were less than with lesions alone. When haloperidol was administered after the striatum had been reinnervated through sprouting (16–32 weeks after lesioning), terminal tree size increased up to 150%, similar to the effect of haloperidol in normal animals. By examining the effect of administering haloperidol at varying times following a lesion, we concluded that a switch in the effect of D2 dopamine receptor blockade occurred after dopaminergic synapses began to form in the striatum. We postulate that when synapses are present, D2 dopamine receptor blockade results in increased terminal density, whereas prior to synapse formation D2 dopamine receptor blockade causes attenuation of a sprouting response. We speculate that D2 dopamine receptors located on growth cones ‘push’ neurites toward their targets, and blockade of these receptors could lead to attenuation of sprouting.
NMDA receptor‐mediated extracellular adenosine accumulation in rat forebrain neurons in culture is associated with inhibition of adenosine kinase
Authors: Lu Yin , Chung Hye Joo , Li Ya , Rosenberg Paul A. 
Published: December 2004

AbstractThe effect of N‐methyl‐d‐aspartate (NMDA) on regulation of extracellular adenosine was investigated in rat forebrain neurons in culture. NMDA evoked accumulation of extracellular adenosine with an EC50 value of 4.8 ± 1.2 µm. The effect of NMDA was blocked by (+)‐5‐methyl‐10,11‐dihydro‐5H‐dibenzo [a, d] cyclohepten‐5,10‐imine hydrogen maleate indicating that NMDA receptor activation was involved. The NMDA effect was also blocked by chelation of extracellular Ca2+ indicating that influx of calcium was required. The nitric oxide–cyclic GMP signalling pathway was not involved, as nitric oxide synthase inhibitors were unable to block, and cGMP analogs were unable to mimic, the effect of NMDA. The source for extracellular adenosine was likely to be intracellular adenosine as the ecto‐5′‐nucleotidase inhibitor αβ‐methylene‐ADP was unable to block the effect of NMDA. One possible cause of intracellular adenosine accumulation might be NMDA receptor‐mediated inhibition of mitochondrial function and ATP hydrolysis. We found that NMDA caused a concentration dependent depletion of intracellular ATP with an EC50 value of 21 ± 8 µm. NMDA also caused a significant decrease in adenosine kinase activity, assayed by two different methods. Consistent with the hypothesis that inhibition of adenosine kinase is sufficient to cause an increase in extracellular adenosine, inhibition of adenosine kinase by 5′‐iodotubercidin resulted in elevation of extracellular adenosine. However, in the presence of a concentration of 5′‐iodotubercidin that inhibited over 90% of adenosine kinase activity, exposure to NMDA still caused adenosine accumulation. These studies suggest that several possible mechanisms are likely to be involved in NMDA‐evoked extracellular adenosine accumulation.
The ability of atypical antipsychotic drugs vs. haloperidol to protect PC12 cells against MPP+‐induced apoptosis
Authors: Qing Hong , Xu Haiyun , Wei Zelan , Gibson Kurt , Li Xin‐Min 
Published: December 2004

AbstractThe present study examined the effects of the atypical antipsychotic drugs clozapine, olanzapine, quetiapine and risperidone, on N‐methyl‐4‐phenylpyridinium ion‐induced apoptosis and DNA damage in PC12 cells, and explored the molecular mechanisms underlying these effects. Haloperidol, a typical antipsychotic drug, was used for comparison. Exposure of PC12 cells to 50 µm N‐methyl‐4‐phenylpyridinium ion for 24 h resulted in a 35–45% loss of cells in culture. Pretreatment with the aforementioned atypical antipsychotic drugs significantly reduced the N‐methyl‐4‐phenylpyridinium ion‐induced cell loss, whereas haloperidol (10–100 µm) did not have this protective effect. Hoechst 33258 staining revealed the apoptotic nuclear features of the N‐methyl‐4‐phenylpyridinium ion‐induced cell death, and showed that the atypical antipsychotic drugs, but not haloperidol, effectively prevented PC12 cells from this N‐methyl‐4‐phenylpyridinium ion‐induced apoptosis. DNA fragmentation assays further confirmed the N‐methyl‐4‐phenylpyridinium ion‐induced nuclear fragmentation. Pretreatment with the atypical antipsychotic drugs completely prevented this nuclear fragmentation, whereas haloperidol only partially prevented it. In vitro oligonucleotide assays indicated an activation of a specific glycosylase that recognizes and cleaves bases (at the 8‐hydroxyl‐2‐deoxyguanine site) that were damaged by N‐methyl‐4‐phenylpyridinium ion. Pretreatment with the atypical antipsychotic drugs more effectively attenuated this N‐methyl‐4‐phenylpyridinium ion‐induced activation than did haloperidol. Northern blot analyses showed that the atypical antipsychotic drugs, but not haloperidol, blocked the N‐methyl‐4‐phenylpyridinium ion‐induced substantial increase of copper/zinc superoxide dismutase mRNA in PC12 cells. Atypical antipsychotic drugs slightly up‐regulated the expression of copper/zinc superoxide dismutase mRNA, whereas haloperidol strongly increased the expression of copper/zinc superoxide dismutase mRNA. These data may account for the different therapeutic effects and side‐effect profiles of typical and atypical antipsychotic drugs in schizophrenia.
Induction of CB2 receptor expression in the rat spinal cord of neuropathic but not inflammatory chronic pain models
Authors: Zhang Ji , Hoffert Cyrla , Vu Huy Khang , Groblewski Thierry , Ahmad Sultan , O'Donnell Dajan 
Published: December 2004

AbstractCannabinoids have been considered for some time as potent therapeutic agents in chronic pain management. Central and systemic administration of natural, synthetic and endogenous cannabinoids produce antinociceptive and antihyperalgesic effects in both acute and chronic animal pain models. Although much of the existing data suggest that the analgesic effects of cannabinoids are mediated via neuronal CB1 receptors, there is increasing evidence to support a role for peripheral CB2 receptors, which are expressed preferentially on immune cells. As yet, little is known about the central contribution of CB2 in neuropathic pain states. We report here that chronic pain models associated with peripheral nerve injury, but not peripheral inflammation, induce CB2 receptor expression in a highly restricted and specific manner within the lumbar spinal cord. Moreover, the appearance of CB2 expression coincides with the appearance of activated microglia.
Limited functional redundancy in high diversity systems: resilience and ecosystem function on coral reefs
Authors: Bellwood David R. , Hoey Andrew S. , Choat J. Howard 
Published: December 2004

Abstract Biodiversity is frequently associated with functional redundancy. Indo‐Pacific coral reefs incorporate some of the most diverse ecosystems on the globe with over 3000 species of fishes recorded from the region. Despite this diversity, we document changes in ecosystem function on coral reefs at regional biogeographical scales as a result of overfishing of just one species, the giant humphead parrotfish (Bolbometopon muricatum). Each parrotfish ingests over 5 tonnes of structural reef carbonates per year, almost half being living corals. On relatively unexploited oceanic reefs, total ingestion rates per m2 balance estimated rates of reef growth. However, human activity and ecosystem disruption are strongly correlated, regardless of local fish biodiversity. The results emphasize the need to consider the functional role of species when formulating management strategies and the potential weakness of the link between biodiversity and ecosystem resilience.
Natural enemy specialization and the period of population cycles
Authors: Rohani P. , Wearing H.J. , Cameron T. , Sait S.M. 
Published: December 2004

AbstractThe dynamical consequences of multiple‐species interactions remain an elusive and fiercely debated topic. Recently, Murdoch and colleagues proposed a general rule for the dynamics of generalist natural enemies: when periodic, they exhibit single generation cycles (SGCs), similar to single species systems. This contrasts markedly with specialists, which tend to show classic (longer period) consumer–resource cycles. Using a well‐studied laboratory system, we show that this general rule is contradicted when we consider resource age‐structure.
Tree size frequency distributions, plant density, age and community disturbance
Authors: Niklas Karl J. , Midgley Jeremy J. , Rand Richard H. 
Published: December 2004

AbstractWe show that explicit mathematical and biological relationships exist among the scaling exponents and the allometric constants (α and β, respectively) of log–log linear tree‐community size frequency distributions, plant density NT, and minimum, maximum and average stem diameters (Dmin, Dmax, and , respectively). As individuals grow in size and Dmax increases, NT is predicted to decrease as reflected by a decrease in the numerical value of α and an increase in the value of β. Our derivations further show that NT decreases as increases even if Dmin or Dmax remain unchanged. Because Dmax and the age of the largest individuals in a community are correlated, albeit weakly, we argue that the interdependent relationships among the numerical values of α, β, NT, and shed light on the extent to which communities have experienced recent global disturbance. These predicted relationships receive strong statistical support using two large datasets spanning a broad spectrum of tree‐dominated communities.
A developmental bottleneck in dispersing larvae: implications for spatial population dynamics
Authors: Schneider Daniel W. , Stoeckel James A. , Rehmann Chris R. , Douglas Blodgett K. , Sparks Richard E. , Padilla Dianna K. 
Published: December 2004

AbstractWe found evidence for a critical population bottleneck at a developmental‐stage transition in larvae of the zebra mussel Dreissena polymorpha Pallas from field estimates of mortality. Identification of this critical period in the field was made possible by closely tracking cohorts of larvae over 5 days of development as they dispersed 128 km in a river system. The presence of a survival bottleneck during development was confirmed in laboratory studies of zebra mussel larvae. Development‐specific mortality has important implications for spatial population dynamics of the zebra mussel in particular, and all species with indirect development in general. Marine reserves that do not take development‐specific mortality into account may dramatically underestimate reserve size needed to protect rare and/or exploited marine populations. Conversely, for the zebra mussel, the lower contribution of dispersing individuals to population growth downstream of reserves can lead to more feasible control through the blocking of dispersal.
Variable reporting and quantitative reviews: a comparison of three meta‐analytical techniques
Authors: Lajeunesse Marc J. , Forbes Mark R. 
Published: December 2004

AbstractVariable reporting of results can influence quantitative reviews by limiting the number of studies for analysis, and thereby influencing both the type of analysis and the scope of the review. We performed a Monte Carlo simulation to determine statistical errors for three meta‐analytical approaches and related how such errors were affected by numbers of constituent studies. Hedges’dand effect sizes based on item response theory (IRT) had similarly improved error rates with increasing numbers of studies when there was no true effect, but IRT was conservative when there was a true effect. Log response ratio had low precision for detecting null effects as a result of overestimation of effect sizes, but high ability to detect true effects, largely irrespective of number of studies. Traditional meta‐analysis based on Hedges’dare preferred; however, quantitative reviews should use various methods in concert to improve representation and inferences from summaries of published data.
Environmental variation and the maintenance of polymorphism: the effect of ambient light spectrum on mating behaviour and sexual selection in guppies
Authors: Gamble Shenagh , Lindholm Anna K. , Endler John A. , Brooks Robert 
Published: December 2004

AbstractThe intensity of sexual selection is influenced by environmental conditions because these conditions influence signal propagation and the risks of the signal being exploited by predators and parasites. We explore the possibility that spatial or temporal heterogeneity in environmental signalling conditions (in this case light spectrum) may induce fluctuating sexual selection on male behaviour and ornamentation in guppies. We used shade cloth and filters to experimentally manipulate light spectrum, mimicking conditions found naturally: early morning/late afternoon light (SC treatment), midday forest shade (F89 filter treatment) and midday woodland shade (F55 filter treatment). Females were more responsive to male courtship and males were less likely to attempt sneak copulations under F55 light than the other two treatments. By contrast, male display rate was not influenced by treatment. Females tended to prefer the same males under SC and F55 light, but attractiveness in these treatments was unrelated to attractiveness under F89 light. There were similarities among treatments in the traits that females preferred: females preferred males with larger areas of orange in all three treatments. There were, however, also some differences, including preference for larger males under F89 light and for smaller males under the other treatments. Overall, the influence of ambient light spectrum on the relative importance of mate choice and male sneak copulation may have important implications for the mode and strength of sexual selection in different environments. The findings on attractiveness and preference functions, however, suggest that light spectrum only weakly affects the direction of sexual selection by female choice.
Regulation of moth–yucca mutualisms: mortality of eggs in oviposition‐induced ‘damage zones’
Authors: Shapiro Judith M. , Addicott John F. 
Published: December 2004

AbstractPollination–seed predation mutualisms such as moth–yucca interactions are important model systems for studying mechanisms that limit exploitation when mutualistic partners have strong conflicts of interest. In many moth–yucca interactions, oviposition leads to the failure of some ovules to develop normally. Here, we demonstrate that moth eggs almost always perish if they are inside these oviposition‐induced ‘damage zones’ of developing fruit. Moreover, because more ovipositions result both in larger damage zones and in higher proportions of eggs within damage zones, this source of mortality is strongly density‐dependent. Therefore, mortality of eggs in oviposition‐induced damage zones may be an important process for limiting seed consumption and regulating moth densities in many moth–yucca mutualisms.
Analysis and comparison of the microbial community structures of two enrichment cultures capable of reductively dechlorinating TCE and cis‐DCE
Authors: Gu April Z. , Hedlund Brian P. , Staley James T. , Strand Stuart E. , Stensel H. David 
Published: December 2004

SummaryIn order to study the effect of different chloroethenes (electron acceptors) on the bacterial composition of dechlorinating communities, two reductive dechlorinating enrichment cultures were developed that were able to reduce trichloroethene (TCE) and cis‐1,2‐dichloroethene (cis‐DCE) to ethene using hydrogen as electron donor, respectively. The inoculum for the cultures was material from a methanogenic fluidized bed reactor (FBR), which was originally seeded with digester sludge and showed a stable capacity for tetrachloroethene (PCE) reduction to ethene for over six years. Molecular methods were used to determine and compare the microbial communities of these two enrichment cultures. A clone library of bacterial 16S rRNA genes was generated for each enrichment. The clones were screened into different groups by restriction fragment length polymorphism (RFLP) analysis using two different four base pair recognition restriction enzymes. A total of 12 sequence types were identified by phylogenetic analysis of nearly complete 16S rDNA sequences (∼1450 bp). The sequences were affiliated with six recognized phyla of the domain Bacteria: Firmicutes (low G+C Gram‐positives), Chloroflexi (green non‐sulphur bacteria), Actinobacteria (high G+C Gram‐positives), Bacteroidetes (Cytophaga‐Flexibacter‐Bacteroides), Nitrospira and Spirochaetes. The results led to the identification of an organism closely related to Dehalococcoides ethenogenes to be the presumptive dechlorinator in both enrichments. Different electron acceptors affected the bacterial diversity and the community profiles of the two enrichments. Most of the sequences identified in our dechlorinating enrichments shared high similarities with sequences previously obtained from other enriched dechlorinating cultures and chlorinated‐compound‐contaminated sediments or aquifers, suggesting these bacteria may have direct or indirect roles in reductive dechlorination.
Mortality in a Population‐based Cohort of Epilepsy Surgery Patients
Authors: Nilsson Lena , Ahlbom Anders , Farahmand Bahman Y. , Tomson Torbjōrn 
Published: December 2004

Summary:  Purpose: To investigate mortality and especially the incidence of sudden unexpected death in epilepsy (SUDEP) in a population‐based cohort of epilepsy surgery patients.Methods: All patients who underwent epilepsy surgery treatment between January 1990 and December 1998 (surgery patients) or whose presurgical evaluation started, although not leading to an operation, during the same period (nonsurgery patients) were identified through the Swedish National Epilepsy register. All subjects were followed up through the Cause of Death Register until December 1998. Standardized mortality ratios (SMRs) for all causes of death and incidence of SUDEP were calculated.Results: During the study period, 651 surgical operations were carried out on 596 patients (316 male). Of those, 14 patients died (six in SUDEP), rendering a total SMR of 4.9 [95% confidence interval (CI), 2.7–8.3]. SUDEP incidence was 2.4 per 1,000 person years. No major differences were found in SMRs or SUDEP rates between subgroups when stratifying for type of operation and for seizure outcome 2 years after surgery. SMR and SUDEP rates were higher in right‐sided temporal lobe resections for gliosis than in left‐sided, but the number of deaths was small. Among 212 nonsurgery patients, five died (four in SUDEP). The SMR for all causes was 7.9 (2.6–18.4), and SUDEP incidence, 6.3 per 1,000 person years.Conclusions: In this large and strictly population‐based cohort, SMR for all causes and SUDEP incidence among surgery patients were similar to those of other studies. No differences in overall mortality emerged by seizure outcome, but none of the SUDEP cases was seizure free at the time of death. Four of five deaths in the nonsurgery group occurred during the surgery evaluation period. Mortality appeared to be lower for surgery than for nonsurgery patients, and the interpretation of this finding is discussed.