bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuroprotection in Parkinson models varies with toxin administration protocol
Authors: Anderson David W. , Bradbury Kristin A. , Schneider Jay S.
Published: December 2006

Numerous factors contribute to substantia nigra pars compacta (SNc) dopamine (DA) neuron death in Parkinson's disease (PD), thus complicating the search for effective neuroprotective agents for this disease. Although the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐treated mouse has been widely used for assessing neuroprotective agents for PD, the pathological processes resulting from MPTP exposure can vary greatly depending upon the MPTP administration protocol. This study assessed the degree to which the neuroprotective efficacy of particular agents may depend upon the MPTP administration protocol (i.e. acute vs. subacute toxin administration). Endpoints analysed were changes in tyrosine hydroxylase (TH) and NeuN cell numbers in the SNc, striatal DA and metabolite levels, and striatal TH+fiber density. The efficacy of putative neuroprotective agents [i.e. LIGA 20, nicotinamide and pramipexole (PPX)] varied depending upon the MPTP administration protocol. LIGA 20 spared striatal DA levels in both MPTP models, while nicotinamide was only effective in the acute toxin administration model and PPX was only effective in the subacute model. In both MPTP models, LIGA 20 and nicotinamide significantly spared DAergic neurons; PPX only spared DAergic neurons in the subacute model. Only acute MPTP‐treated mice that received nicotinamide had a significant sparing of striatal DAergic fibers. These results underscore the need to assess putative neuroprotective agents for PD in multiple animal models using multiple endpoints. This strategy may better identify compounds with broad neuroprotective/neurorestorative profiles that may be more likely to be clinically effective.
Secreted factors from ventral telencephalon induce the differentiation of GABAergic neurons in cortical cultures
Authors: Trinh H.‐h. , Reid J. , Shin E. , Liapi A. , Parnavelas J. G. , Nadarajah B.
Published: December 2006

It is widely believed that the pyramidal cells and interneurons of the cerebral cortex are distinct in their origin, lineage and genetic make up. In view of these findings, the current thesis is that the phenotype determination of cortical neurons is primarily directed by genetic mechanisms. Using in vitro assays, the present study demonstrates that secreted factors from ganglionic eminence (GE) of the ventral telencephalon have the potency to induce the differentiation of a subset of cortical neurons towards γ‐aminobutyric acid (GABA)ergic lineage. Characterization of cortical cultures that were exposed to medium derived from GE illustrated a significant increase in the number of GABA‐, calretinin‐ and calbindin‐positive neurons. Calcium imaging together with pharmacological studies showed that the application of exogenous medium significantly elevated the intracellular calcium transients in cortical neurons through the activation of ionotropic glutamate receptors. The increase in GABA+ neurons appeared to be associated with the elevated calcium activity; treatment with blockers specific for glutamate receptors abolished both the synchronized transients and reduced the differentiation of GABAergic neurons. Such studies demonstrate that although intrinsic mechanisms determine the fate of cortical interneurons, extrinsic factors have the potency to influence their neurochemical differentiation and contribute towards their molecular diversity.
Dopamine activity in the nucleus accumbens modulates blocking in fear conditioning
Authors: Iordanova Mihaela D. , Westbrook R. Frederick , Killcross A. Simon
Published: December 2006

Associative learning depends on the discrepancy between actual and predicted outcomes. The neurochemical mechanisms involved in regulating this discrepancy in Pavlovian fear conditioning in rats are unknown. We employed the blocking paradigm to show that this learning discrepancy is decreased by heightened activation of dopamine following an accumbal infusion of d‐amphetamine, and increased by dopaminegic blockade following an accumbal infusion of cis‐(z)‐flupenthixol or by combined infusions of the D1 (SCH23390) and D2 (sulpiride) antagonists but not by infusion of either alone.
Tissue sparing and functional recovery following experimental traumatic brain injury is provided by treatment with an anti‐myelin‐associated glycoprotein antibody
Authors: Thompson Hilaire J. , Marklund Niklas , LeBold David G. , Morales Diego M. , Keck Carrie A. , Vinson Mary , Royo Nicolas C. , Grundy Robert , McIntosh Tracy K.
Published: December 2006

Axonal injury is a hallmark of traumatic brain injury (TBI) and is associated with a poor clinical outcome. Following central nervous system injury, axons regenerate poorly, in part due to the presence of molecules associated with myelin that inhibit axonal outgrowth, including myelin‐associated glycoprotein (MAG). The involvement of MAG in neurobehavioral deficits and tissue loss following experimental TBI remains unexplored and was evaluated in the current study using an MAG‐specific monoclonal antibody (mAb). Anesthetized rats (n = 102) were subjected to either lateral fluid percussion brain injury (n = 59) or sham injury (n = 43). In surviving animals, beginning at 1 h post‐injury, 8.64 µg anti‐MAG mAb (n = 33 injured, n = 21 sham) or control IgG (n = 26 injured, n = 22 sham) was infused intracerebroventricularly for 72 h. One group of these rats (n = 14 sham, n = 11 injured) was killed at 72 h post‐injury for verification of drug diffusion and MAG immunohistochemistry. All other animals were evaluated up to 8 weeks post‐injury using tests for neurologic motor, sensory and cognitive function. Hemispheric tissue loss was also evaluated at 8 weeks post‐injury. At 72 h post‐injury, increased immunoreactivity for MAG was seen in the ipsilateral cortex, thalamus and hippocampus of brain‐injured animals, and anti‐MAG mAb was detectable in the hippocampus, fimbria and ventricles. Brain‐injured animals receiving anti‐MAG mAb showed significantly improved recovery of sensorimotor function at 6 and 8 weeks (P < 0.01) post‐injury when compared with brain‐injured IgG‐treated animals. Additionally, at 8 weeks post‐injury, the anti‐MAG mAb‐treated brain‐injured animals demonstrated significantly improved cognitive function and reduced hemispheric tissue loss (P < 0.05) when compared with their brain‐injured controls. These results indicate that MAG may contribute to the pathophysiology of experimental TBI and treatment strategies that target MAG may be suitable for further evaluation.
Differential susceptibility to striatal neurodegeneration induced by quinolinic acid and kainate in inbred, outbred and hybrid mouse strains
Authors: McLin Jessica Pilar , Thompson Leslie Michels , Steward Oswald
Published: December 2006

In mice, the genetic background determines susceptibility to hippocampal neurodegeneration induced by the excitotoxin kainic acid (KA). If genetic background plays as significant a role in the striatum, the area most affected in Huntington's disease (HD), it is important to characterize intrinsic differences in neuronal susceptibility in mouse strains used in HD models. This study was performed to investigate whether strain differences of different HD mouse models are determinants of striatal resistance to excitotoxicity. We conducted a survey of the susceptibility of striatal neurons to neurodegeneration induced by quinolinic acid and KA in six inbred, two outbred and two F1 hybrid (resistant*vulnerable) strains. These are the same strains in which we have assessed vulnerability to KA‐induced hippocampal neurodegeneration. We found significant strain differences in response to both excitotoxins and, for the most part, the strain‐dependent patterns of susceptibility to quinolinic acid and KA were similar and comparable to those previously found with KA‐induced hippocampal neurodegeneration. There were some incongruities, suggesting that the genetic determinants may be different for the two forms of excitotoxicity or that there are important interacting factors. For example, the F1 hybrid strains exhibited neurodegeneration similar to their vulnerable parent, indicating that the vulnerable phenotype is dominant. This is in contrast to KA‐induced hippocampal neurodegeneration, where F1 hybrids exhibit the resistant phenotype. These results are also of significance with regard to the issue of region‐specific vulnerability in the context of different diseases in which genetic modifiers affect age of onset and/or disease progression.
Muscarinic control of graded persistent activity in lateral amygdala neurons
Authors: Egorov Alexei V. , Unsicker Klaus , Von Bohlen und Halbach Oliver
Published: December 2006

The cholinergic system is crucially involved in several cognitive processes including attention, learning and memory. Muscarinic actions have profound effects on the intrinsic firing pattern of neurons. In principal neurons of the entorhinal cortex (EC), muscarinic receptors activate an intrinsic cation current that causes multiple self‐sustained spiking activity, which represents a potential mechanism for transiently sustaining information about novel items. The amygdala appears to be important for experience‐dependent learning by emotional arousal, and cholinergic muscarinic influences are essential for the amygdala‐mediated modulation of memory. Here we show that principal neurons from the lateral nucleus of the amygdala (LA) can generate intrinsic graded persistent activity that is similar to EC layer V cells. This firing behavior is linked to muscarinic activation of a calcium‐sensitive non‐specific cation current and can be mimicked by stimulation of cholinergic afferents that originate from the nucleus basalis of Meynert (n. M). Moreover, we demonstrate that the projections from the n. M. are essential and sufficient for the control and modulation of graded firing activity in LA neurons. We found that activation of these cholinergic afferents (i) is required to maintain and to increase firing rates in a graded manner, and (ii) is sufficient for the graded increases of stable discharge rates even without an associated up‐regulation of Ca2+. The induction of persistent activity was blocked by flufenamic acid or 2‐APB and remained intact after Ca2+‐store depletion with thapsigargin. The internal ability of LA neurons to generate graded persistent activity could be essential for amygdala‐mediated memory operations.
Corrective movements in response to displacements in visual feedback are more effective during periods of 13–35 Hz oscillatory synchrony in the human corticospinal system
Authors: Androulidakis Alexandros G. , Doyle Louise M. F. , Gilbertson Thomas P. , Brown Peter
Published: December 2006

Oscillatory synchronization in the beta (∼20 Hz) band is a common feature of human motor control, manifest at cortical and muscular levels during tonic contraction. Here we test the hypothesis that the influence of visual feedback on performance in a positional hold task is increased during bursts of beta‐band synchrony in the corticospinal motor system. Healthy subjects were instructed to extend their forefinger while receiving high‐gain visual feedback of finger position on a PC screen. Small step displacements of the feedback signal were triggered either by bursts of beta oscillations in scalp electroencephalogram or randomly with respect to cortical beta activity, and the resulting positional corrections expressed as a percentage of the step displacement. Corrective responses to beta and randomly triggered step changes in visual feedback were 41.7 ± 4.9 and 31.5 ± 6.8%, respectively (P < 0.05). A marked increase in the coherence in the beta band was also found between muscle activity and cortical activity during the beta‐triggered condition. The results suggest that phasic elevations of beta activity in the corticospinal motor system are associated with an increase in the gain of the motor response to visual feedback during a tonic hold task. Beta activity may index a motor state in which processing relevant to the control of positional hold tasks is promoted, with behavioural consequences.
Induction of synchronous oscillatory activity in the rat lateral amygdala in vitro is dependent on gap junction activity
Authors: Sinfield James L. , Collins Dawn R.
Published: December 2006

Synchronized and rhythmic activity within the amygdala is thought to play a pivotal role in the generation of fear‐ and anxiety‐related behaviour. The aim here was to determine the validity of the in vitro amygdala slice preparation to investigate the generation of rhythmic activity similar to that observed in vivo. Extracellular population activity recorded from the lateral nucleus of the amygdala in vitro showed significant enhancement of activity within the theta‐band frequency (3–9 Hz) in the presence of kainic acid (100 nm; n = 18). Alterations in the patterns of oscillatory activity within the gamma frequency band (20–40 Hz) were observed in the presence of (RS)‐3,5‐dihydroxyphenylglycine (10 µm; n = 7) or carbachol (50 µm; n = 5). Theta frequency oscillatory activity was blocked in the presence of the gap junction blocker carbenoxolone (100 mm), whereas gamma frequency oscillatory activity showed increased variability in the dominant frequency of rhythmic activity. The results suggest that the neuronal circuitry of the amygdala in vitro is capable of generating and sustaining rhythmic activity and that intercellular communication via gap junctions may play a role in the synchronization of population activity underlying this oscillatory activity.
Nicotine exposure refines visual map topography through an NMDA receptor‐mediated pathway
Authors: Yan Xiaohua , Zhao Bing , Butt Christopher M. , Debski Elizabeth A.
Published: December 2006

The precise mapping of one surface onto another is fundamental to visual system organization and depends upon adequate stimulation of postsynaptic targets to stabilize correctly placed synapses. As exogenous nicotine alters neuronal activity, we investigated whether it would affect the visual map created by retinal ganglion cell terminals in the frog optic tectum. Chronic exposure of the tectum to nicotine decreased the retinal area from which cells project to a given tectal site. This map refinement was also produced by exposure to either the α‐bungarotoxin sensitive nicotinic receptor agonist, anatoxin‐a or the α‐bungarotoxin‐insensitive nicotinic receptor agonist epiboxidine. Immunocytochemical studies using mAb306 and mAb22 demonstrated that α‐bungarotoxin‐sensitive and ‐insensitive nicotinic receptors, respectively, occupied different tectal sites. Choline acetyltransferase immunoreactivity overlapped with mAb306, but not mAb22, staining. The developing optic tectum was more sensitive to nicotine than the adult tectum and nicotine induced both map refinements and map disruptions in a concentration‐dependent manner. Blockade of theN‐methyl‐d‐aspartate (NMDA) receptor with D(–)‐2‐amino‐5‐phosphonopentanoic acid (D‐APV) prevented nicotine from refining the map in the adult tectum. Exposure to the use‐dependent NMDA antagonist MK801 alone had no effect on retinotectal topography but in combination with either NMDA or nicotine it disrupted the map. Exposure to NMDA alone produced refinement. We conclude that the map refinement induced by chronic nicotine treatment has as its basis an increase in the level of NMDA receptor activity. The data are consistent with a model whereby map topography can be bidirectionally affected by either increasing or decreasing NMDA receptor activity.
Regional cerebral blood flow changes associated with clitorally induced orgasm in healthy women
Authors: Georgiadis Janniko R. , Kortekaas Rudie , Kuipers Rutger , Nieuwenburg Arie , Pruim Jan , Reinders A. A. T. Simone , Holstege Gert
Published: December 2006

There is a severe lack of knowledge regarding the brain regions involved in human sexual performance in general, and female orgasm in particular. We used [15O]‐H2O positron emission tomography to measure regional cerebral blood flow (rCBF) in 12 healthy women during a nonsexual resting state, clitorally induced orgasm, sexual clitoral stimulation (sexual arousal control) and imitation of orgasm (motor output control). Extracerebral markers of sexual performance and orgasm were rectal pressure variability (RPstd) and perceived level of sexual arousal (PSA). Sexual stimulation of the clitoris (compared to rest) significantly increased rCBF in the left secondary and right dorsal primary somatosensory cortex, providing the first account of neocortical processing of sexual clitoral information. In contrast, orgasm was mainly associated with profound rCBF decreases in the neocortex when compared with the control conditions (clitoral stimulation and imitation of orgasm), particularly in the left lateral orbitofrontal cortex, inferior temporal gyrus and anterior temporal pole. Significant positive correlations were found between RPstd and rCBF in the left deep cerebellar nuclei, and between PSA and rCBF in the ventral midbrain and right caudate nucleus. We propose that decreased blood flow in the left lateral orbitofrontal cortex signifies behavioural disinhibition during orgasm in women, and that deactivation of the temporal lobe is directly related to high sexual arousal. In addition, the deep cerebellar nuclei may be involved in orgasm‐specific muscle contractions while the involvement of the ventral midbrain and right caudate nucleus suggests a role for dopamine in female sexual arousal and orgasm.
Mouse galectin‐1 inhibits the toxicity of glutamate by modifying NR1 NMDA receptor expression
Authors: Lekishvili Tamuna , Hesketh Shirley , Brazier Marcus W. , Brown David R.
Published: December 2006

One of the major causes of neuronal death in neurodegenerative disease is excitotoxicity from the neurotransmitter glutamate. This form of cell death could arise from either excess levels of glutamate due to decreased astrocyte clearance or due to increased susceptibility. We have identified galectin‐1, a galactose‐binding lectin, as a potential neuroprotective factor secreted by astrocytes. Our results show that both native and recombinant galectin‐1 protects mouse and rat cerebellar neurons from the toxic effects of glutamate. Galectin‐1 applied to neurons increased their expression of the NMDA receptor NR1 and increased the proportion of the NR1a subunit subtype while antisense knockdown of the NR1a receptor blocked the neuroprotective effect of galectin‐1. This effect of the protein was dependent upon it carbohydrate recognition domain, suggesting that the protein acts in a reduced dimerized form. In addition, galectin‐1 caused a decreased expression of PKC associated with increased resistance to glutamate toxicity. These results suggest that the astrocytic lectin galectin‐1 could protect neurons against the effects of excitotoxicity as seen in stroke and ischemic injury.
Gender‐related differences in the human subthalamic area: a local field potential study
Authors: Marceglia S. , Mrakic‐Sposta S. , Foffani G. , Cogiamanian F. , Caputo E. , Egidi M. , Barbieri S. , Priori A.
Published: December 2006

The objective of this study was to investigate the possible existence of gender‐related neurophysiological differences in the oscillatory activity of the human subthalamic area. To this end, we recorded local field potentials (LFPs) after neurosurgical procedures for deep brain stimulation (DBS) in 24 patients (12 males and 12 females) with Parkinson's disease. LFP recordings at rest before levodopa medication (19 nuclei from 11 female patients and 16 nuclei from ten male patients) showed significantly higher power in the alpha/low‐beta band (8–12 Hz, P < 0.01; 13–20 Hz, P = 0.03) in females than in males. After levodopa medication (ten nuclei from six female patients and 11 nuclei from seven male patients), the power in the high‐gamma band (60–90 Hz) and of the 300 Hz rhythm was significantly higher in females than in males (high‐gamma, P = 0.007; 300 Hz, P = 0.002). These findings show that functional gender‐related differences in the central nervous system involve the human subthalamic area (STN) and its response to levodopa in Parkinson's disease. Gender‐related neurophysiological differences may be important for understanding gender‐specific features of neurodegenerative disorders and should be considered when interpreting LFP data from the human basal ganglia.
Innexins in the lobster stomatogastric nervous system: cloning, phylogenetic analysis, developmental changes and expression within adult identified dye and electrically coupled neurons
Authors: Ducret E. , Alexopoulos H. , Le Feuvre Y. , Davies J. A. , Meyrand P. , Bacon J. P. , Fénelon V. S.
Published: December 2006

Gap junctions play a key role in the operation of neuronal networks by enabling direct electrical and metabolic communication between neurons. Suitable models to investigate their role in network operation and plasticity are invertebrate motor networks, which are built of comparatively few identified neurons, and can be examined throughout development; an excellent example is the lobster stomatogastric nervous system. In invertebrates, gap junctions are formed by proteins that belong to the innexin family. Here, we report the first molecular characterization of two crustacean innexins: the lobster Homarus gammarus innexin 1 (Hg‐inx1) and 2 (Hg‐inx2). Phylogenetic analysis reveals that innexin gene duplication occurred within the arthropod clade before the separation of insect and crustacean lineages. Using in situ hybridization, we find that each innexin is expressed within the adult and developing lobster stomatogastric nervous system and undergoes a marked down‐regulation throughout development within the stomatogastric ganglion (STG).The number of innexin expressing neurons is significantly higher in the embryo than in the adult. By combining in situ hybridization, dye and electrical coupling experiments on identified neurons, we demonstrate that adult neurons that express at least one innexin are dye and electrically coupled with at least one other STG neuron. Finally, two STG neurons display no detectable amount of either innexin mRNAs but may express weak electrical coupling with other STG neurons, suggesting the existence of other forms of innexins. Altogether, we provide evidence that innexins are expressed within small neuronal networks built of dye and electrically coupled neurons and may be developmentally regulated.
Impairment of microtubule‐dependent trafficking by overexpression of α‐synuclein
Authors: Lee He‐Jin , Khoshaghideh Farnaz , Lee Stephen , Lee Seung‐Jae
Published: December 2006

Abnormal accumulation of α‐synuclein (α‐syn) has been linked to several neurological disorders, including Parkinson's disease (PD). However, the underlying mechanism by which α‐syn accumulation affects neuronal function and survival remains unknown. Here, we provide data suggesting a possible effect of aggregated α‐syn on the microtubule (MT) network. Consistent with the MT dysfunction, we also observed other degenerative changes, such as neuritic degeneration, trafficking defects, and Golgi fragmentation, which are common pathological features shared by many human neurodegenerative diseases. Neuritic degeneration and Golgi fragmentation were confirmed in primary cultures of dorsal root ganglia (DRG) neurons overexpressing α‐syn. This effect of α‐syn seems to have some selectivity to the MT system, as actin microfilaments and MT‐independent trafficking remain unaffected. Within the degenerating neurites, we found numerous spherical co‐aggregates of α‐syn and tubulins, from which actin was excluded. These studies suggest that the MT system is a potential target of α‐syn, and impairment of this system might have impacts on neuronal structure and function.
Chronic nicotine‐induced switch in Src‐family kinase signaling for long‐term potentiation induction in hippocampal CA1 pyramidal cells
Authors: Yamazaki Yoshihiko , Jia Yousheng , Wong Jamie K. , Sumikawa Katumi
Published: December 2006

Here, we show that chronic nicotine exposure induces changes in Src signaling for the modulation of N‐methyl‐d‐aspartate receptor (NMDAR) function and LTP induction in CA1 pyramidal cells. Activation of muscarinic receptors normally potentiates NMDAR responses in pyramidal cells via a Gq/protein kinase C (PKC)/proline‐rich tyrosine kinase 2/Src signaling cascade. However, muscarinic, PKC and Src stimulation had no effect on NMDAR responses after chronic nicotine treatment. The lack of effect was apparently due to enhanced tyrosine phosphorylation, and therefore further stimulation of the signaling cascade caused no effect on NMDAR responses. Interestingly, another Src‐family kinase potentiated NMDAR responses after, but not before, chronic nicotine treatment. In control pyramidal cells, Src inhibitor peptides prevented tetanus‐induced long‐term potentiation (LTP). Conversely, in chronic nicotine‐exposed cells, the inhibitor was ineffective in blocking tetanus‐induced LTP. Furthermore, in control pyramidal cells, applying exogenous Src and administration of an endogenous Src‐family kinase activator increased α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate receptor (AMPAR)‐mediated responses. This increase was blocked by Src inhibitor peptides and occluded tetanus‐induced LTP, as reported previously. In contrast, in chronic nicotine‐treated pyramidal cells, applying exogenous Src had no effect on AMPAR‐mediated responses and a tetanus‐induced LTP. Interestingly, however, administration of an endogenous Src‐family kinase activator enhanced AMPAR‐mediated responses, which occluded tetanus‐induced LTP. This enhancement was not prevented by co‐application of Src inhibitor peptides. Thus, it appears that chronic nicotine exposure recruits another member of the Src‐family for the regulation of NMDAR function and LTP induction. The nicotine‐induced distinct signaling cascades may be involved in long‐lasting memories of nicotine misuse.
Sex differences in the basolateral amygdala: the extracellular levels of serotonin and dopamine, and their responses to restraint stress in rats
Authors: Mitsushima Dai , Yamada Kaori , Takase Kenkichi , Funabashi Toshiya , Kimura Fukuko
Published: December 2006

The sex difference in the emotional response to stress suggests a sex‐specific stress response in the amygdala. To examine the sex difference in extracellular levels of serotonin (5HT) and dopamine (DA) in the basolateral amygdala (BLA) and their responses to restraint stress,in vivomicrodialysis studies were performed in male and female rats. In experiment I, dialysates were collected from the BLA at 15‐min intervals under the freely moving condition. Mean extracellular levels of 5HT or DA in the BLA were higher in male rats than in female rats. In experiment II, rats were subjected to restraint stress for 60 min to examine the stress response of 5HT or DA levels. Although restraint stress significantly increased extracellular 5HT levels in both sexes of rats, female rats showed a greater response than male rats. Moreover, restraint stress significantly increased extracellular DA levels in female rats, but not in male rats. In experiment III, rats were subjected to restraint stress for 30 min to examine behavioral responses to restraint stress. Although no sex difference was observed in the number of audible vocalizations, male rats defecated a larger number of fecal pellets than female rats. In experiment IV, rats were tested for freezing behavior to examine contextual fear responses. Conditioned male rats showed a longer freezing time than conditioned female rats. We found sex differences in the extracellular levels of 5HT and DA in the BLA and their responses to restraint stress, which may be involved in the sex‐specific emotional response to stress in rats.
Invasion in a heterogeneous world: resistance, coexistence or hostile takeover?
Authors: Melbourne Brett A. , Cornell Howard V. , Davies Kendi F. , Dugaw Christopher J. , Elmendorf Sarah , Freestone Amy L. , Hall Richard J , Harrison Susan , Hastings Alan , Holland Matt , Holyoak Marcel , Lambrinos John , Moore Kara , Yokomizo Hiroyuki
Published: December 2006

We review and synthesize recent developments in the study of the invasion of communities in heterogeneous environments, considering both the invasibility of the community and impacts to the community. We consider both empirical and theoretical studies. For each of three major kinds of environmental heterogeneity (temporal, spatial and invader‐driven), we find evidence that heterogeneity is critical to the invasibility of the community, the rate of spread, and the impacts on the community following invasion. We propose an environmental heterogeneity hypothesis of invasions, whereby heterogeneity both increases invasion success and reduces the impact to native species in the community, because it promotes invasion and coexistence mechanisms that are not possible in homogeneous environments. This hypothesis could help to explain recent findings that diversity is often increased as a result of biological invasions. It could also explain the scale dependence of the diversity–invasibility relationship. Despite the undoubted importance of heterogeneity to the invasion of communities, it has been studied remarkably little and new research is needed that simultaneously considers invasion, environmental heterogeneity and community characteristics. As a young field, there is an unrivalled opportunity for theoreticians and experimenters to work together to build a tractable theory informed by data.
Persistence and Extinction for General Nonautonomous n‐Species Lotka–Volterra Cooperative Systems with Delays
Authors: Abdurahman Xamxinur , Teng Zhidong
Published: December 2006

The general nonautonomous n‐species Lotka–Volterra cooperative systems with varying‐time delays are studied. Sufficient conditions for the uniform strong persistence, uniform weak average persistence, uniform strong average persistence, and extinction of populations are obtained by applying the method of Liapunov functionals. Particularly, when the intrinsic growth rate of a species is nonpositive, the species can be persistent or extinct under the same given assumptions.
Separable Systems of Coordinates for Triangular Newton Equations
Authors: Marciniak Krzysztof , Rauch‐Wojciechowski Stefan
Published: December 2006

Triangular form of Newton equations is a strong property. Together with the existence of a single quadratic with respect to velocities integral of motion, it usally implies existence of further n− 1 integrals that are also quadratic. These integrals make the triangular system separable in new type of coordinates. The separation coordinates are built of quadric surfaces that are nonorthogonal and noconfocal and can intersect along lower dimensional singular manifolds. We present here separability theory for n‐dimensional triangular systems and analyze the structure of separation coordinates in two and three dimensions.
The New Keynesian Model and the Euro Area Business Cycle*
Authors: Casares Miguel
Published: December 2006

This paper describes a New Keynesian model incorporating transactions‐facilitating money and a time‐to‐build constraint into endogenous capital accumulation. The calibrated New Keynesian model performs almost as well as the estimated vector autoregressive model in replicating Euro area cyclical correlations between key variables such as output and inflation, although it fares less well in predicting the procyclical dynamics of nominal interest rates. The presence of a time‐to‐build requirement in the model helps to improve its fit to Euro area data, whereas the role of transactions‐facilitating money is much less important. Impulse–response functions and a decomposition of variance complete the analysis.
The Delphi process – an expert‐based approach to ecological modelling in data‐poor environments
Authors: MacMillan D. C. , Marshall K.
Published: December 2006

Resource managers are involved in difficult decisions that affect rare species and habitats but often lack relevant ecological knowledge and experience. Ecological models are increasingly being looked to as a means of assisting the decision‐making process, but very often the data are missing or are unsuited to empirical modelling. This paper describes the development and application of the Delphi approach to develop a decision support tool for wildlife conservation and management. The Delphi process is an expert‐based approach to decision support that can be used as a means for predicting outcomes in situations where ‘absolute’ or ‘objective’ models are unavailable or compromised by lack of appropriate data. The method aims to develop consensus between experts over several rounds of deliberation on the assumption that combining the expertise of several individuals will provide more reliable results than consulting one or two individuals. In this paper the approach is used to engineer soft knowledge on the conservation requirements of capercaillie Tetrao urogallus, an endangered woodland grouse, into a model that can be used by forests managers to improve the quality of forest habitat for capercaillie over extensive commercial forest areas. This paper concludes with a discussion of the potential advantages and disadvantages of Delphi and other soft knowledge approaches to ecological modelling and conservation management.
Demography of an Afrotropical passerine in a highly fragmented landscape
Authors: Githiru M. , Lens L.
Published: December 2006

Demographic attributes of discrete subpopulations of animals and plants that constitute a larger (meta)population network may affect the strength and direction of local population responses to habitat loss or degradation. To address this question in an Afrotropical context, we studied survival rates, population densities, sex ratios and age distributions in seven white‐starred robinPogonocichla stellatapopulations inhabiting differently sized forest remnants in a highly fragmented Kenyan landscape. Sex ratios were strongly male biased, especially during the non‐breeding season, but the level of bias did not differ between age groups nor fragment sizes. Juvenile to adult ratios were smallest in the medium‐sized fragment, but did not differ between the largest and smallest fragments. Low population density combined with a skewed sex ratio in the medium‐sized fragment pointed towards a local scarcity of females, which was supported by the presence of unmated territorial males. Based on capture–recapture analysis, all populations were considered stable on average. When combining demographic patterns with those emerging from a recent population genetic study and removal experiment, our results support the notion that small populations inhabiting tiny habitat remnants may play an important role in augmenting the long‐term survival of spatially structured populations.
Nest‐site selection of endangered cinereous vulture (Aegypius monachus) populations affected by anthropogenic disturbance: present and future conservation implications
Authors: Morán‐López R. , Sánchez Guzmán J. M. , Borrego E. Costillo , Sánchez A. Villegas
Published: December 2006

The cinereous vulture Aegypius monachus is the largest bird of the western Palaearctic, and is threatened over its entire range of distribution. Considering explicitly the influence of human interference, we studied breeding habitat selection in seven breeding colonies using a geographic information system and multivariate statistical models. Steep areas far from human disturbance constituted the preferential breeding sites in all the colonies. The nesting substrate and climatic conditions varied between colonies, but always corresponded to non‐extreme climates, and included tree species of adequate size. Since human activities influenced the breeding habitat choice, there is a potential for management policies that can clearly be of benefit for the conservation of this vulture. These would fundamentally be as follows: (1) forestry activity should be oriented to protecting oak (Quercus spp.) and pine (Pinus ssp.) stands, especially individual trees of great height, and to replacing eucalyptus (Eucalyptus spp.) with autochthonous species; (2) activities (recreational, economic, etc.) around the breeding areas should be scheduled and spatially organized to avoid disturbance, particularly those deriving from the proximity of roads and tracks; (3) the expected effects of global warming should be compensated, identifying future sites where the habitat can be managed, supplementary food can be provided and reserves can be designed.
Wildlife conservation and animal temperament: causes and consequences of evolutionary change for captive, reintroduced, and wild populations
Authors: McDougall P. T. , Réale D. , Sol D. , Reader S. M.
Published: December 2006

We argue that animal temperament is an important concept for wildlife conservation science and review causes and consequences of evolutionary changes in temperament traits that may occur in captive‐breeding programmes. An evolutionary perspective is valid because temperament traits are heritable, linked to fitness and potentially subject to intense selection in captivity. Natural, sexual and artificial selection can cause permanent shifts in temperament, reducing the diversity of temperament traits, diversity that may be critical to reintroduction success. Breeding programmes that ignore temperament risk leading the captive population towards domestication. Furthermore, shifts in temperament may involve alterations in linked morphological and physiological traits, and selection may even change functional relationships between traits. Captive‐breeding programmes can reduce changes in temperaments by closely monitoring temperament traits, equalizing reproductive success between temperament morphs and using environmental enrichment to reduce captive stress. Under certain circumstances, knowledge about temperament may also provide a useful tool to optimize captive reproduction and to increase reintroduction success. Outside reintroduction programmes, temperament can mediate responses to human contact, hunting, exploitation, habitat fragmentation and disease transmission. Consideration of temperaments could strengthen both captive and wild conservation efforts.
Assessment of the historical population size of an endangered bird, the black‐faced spoonbill (Platalea minor) by analysis of mitochondrial DNA diversity
Authors: Yeung C. K.‐L. , Yao C.‐T. , Hsu Y.‐C. , Wang J.‐P. , Li S.‐H.
Published: December 2006

We present a practical case of inferring historical demography in an endangered avian species, the black‐faced spoonbill Platalea minor, which may be of reference for strategizing conservation planning for species lacking historical records. We applied a genetic approach, complemented by limited knowledge of demographic parameters and life history, to infer the historical population size in the black‐faced spoonbill, based on 2369 bp of three protein‐coding mitochondrial DNA fragments from 87 individuals. The best estimate of θ (a product of two times the female effective population and the mutation rate) was 0.00028, which led a historical population size of 10 320 (95% CI: 1976–37 254) individuals – roughly nine times larger than the current estimated global population size of 1206 individuals. For an avian species lacking historical demographic records, this study extrapolates the occurrence of a severe and probably recent historical population reduction in the endangered black‐faced spoonbill. We suggest that the population decline of this bird might not be fully explained by factors such as the Korean War or loss of habitat; rather, a bottleneck resulting from pollution by pesticides seems more congruent with the demographic history in terms of the scale of the population reduction and the timing and pattern of recovery. Environmental monitoring is therefore suggested as a proactive step to prevent future pollution or disease outbreak.
Managing the matrix for large carnivores: a novel approach and perspective from cheetah (Acinonyx jubatus) habitat suitability modelling
Authors: Muntifering J. R. , Dickman A. J. , Perlow L. M. , Hruska T. , Ryan P. G. , Marker L. L. , Jeo R. M.
Published: December 2006

Effective management within the human‐dominated matrix, outside of formally protected areas, is of paramount importance to wide‐ranging carnviores. For instance, the largest extant population of cheetahs Acinonyx jubatus currently persists on privately owned Namibian ranchlands, and provides an excellent case study to examine and design matrix conservation approaches. Although human‐caused mortality is likely the principal threat to this population, ancedotal evidence suggests that ‘bush encroachment’, the widespread conversion of mixed woodland and savannah habitats to dense, Acacia‐dominated thickets, is another probable threat. A better understanding of cheetah habitat use, outside of protected areas, could be used to directly influence habitat management strategies and design local restoration and conflict mitigation efforts. To identify specific habitat characteristics associated with cheetah use, we used radio‐telemetry locations to identify areas used intensively by cheetahs on commercial Namibian farms. We then compared the habitat characteristics of these ‘high‐use’ areas with adjacent ‘low‐use’ areas. A binary logistic regression model correctly categorized 92% of plot locations as high or low use, and suggested that cheetahs may be utilizing ‘rewarding patches’ with better sighting visibility and greater grass cover. We discuss the possible reasons for kudu Tragelaphus strepsiceros, Namibian cheetahs' preferred prey, exhibiting significantly lower abundance in high‐use areas. Using habitat characteristics to identify areas intensively utilized by cheetahs has important implications for guiding future habitat restoration and developing effective predator conflict mitigation efforts.
Trends, dynamics and resilience of an Ethiopian wolf population
Authors: Marino J. , Sillero‐Zubiri C. , Macdonald D.W.
Published: December 2006

Fifteen years of monitoring in the Bale Mountains provide a valuable time series to better understand the dynamics of populations of the endangered Ethiopian wolf Canis simensis in the face of epizootics and increasing human pressure. Line‐transect counts in four study areas were used to identify trends in the local abundances of wolves, people, livestock and domestic dogs (a putative rabies reservoir). Estimates of wolf abundance were validated against total counts in prime wolf habitats, where two local populations decimated by rabies in the early 1990s had recovered fully by 2000. Growth appeared to be regulated by negative density dependence, but the rate of growth was unexpectedly low at reduced densities. Limitations to rapid growth, including an initial gap for which data were sparse, are discussed. In a poorer habitat, wolf abundance estimates were less reliable but indicated slight fluctuations without an overall trend. A local extinction was recorded in an area of marginal habitat. With this exception, trends in wolf abundances were unrelated to trends in the abundance of people, livestock or dogs. Rabies emerged as the main cause of decline for high‐density populations. The rapidly increasing livestock grazing pressure in Bale gives cause for concern, calling for further research on its impacts upon long‐term wolf survival.
Effect of human activities on the behaviour of breeding Spanish imperial eagles (Aquila adalberti): management implications for the conservation of a threatened species
Authors: González L. M. , Arroyo B. E. , Margalida A. , Sánchez R. , Oria J.
Published: December 2006

We studied (14 500 h of field observations during 20 breeding attempts by 10 pairs) the effects of human activities on the behaviour of breeding Spanish imperial eagles. The probability that human activities around nest sites provoked a flight reaction varied significantly among territories and among types of activity, and increased when the distance between the activity and the nest site decreased, and increased when the number of people involved in each intrusion was higher. Pedestrian activities (mainly by hunters, campers and ecotourists) caused more flight reactions than vehicles. Overall, the probability of a reaction increased sharply when activities occurred at less than 450 m from the nest, but was negligible if they occurred at 800 m. Reaction probability was lower in territories with higher intrusion frequencies (which suggests that some habituation occurs), where the nest was not visible from the tracks, and in less ‘plain’ or ‘accessible’ territories. Hatching rate was affected negatively by the frequency of human activities. Our results suggest that the critical inner buffer zone around Spanish imperial eagle nests should be established at a minimum radius of 500 m, and the vulnerable zones at a minimum of 800 m, bearing in mind the physiography of the terrain and the visibility of the nests. Finally, in future studies of nest‐site selection with this species, it would be advisable to use a variable that quantifies (through field observations) human disturbance frequency.
Congenital Disorder of Glycosylation Type Ia: Searching for the Origin of Common Mutations in PMM2
Authors: Quelhas D. , Quental R. , Vilarinho L. , Amorim A. , Azevedo L.
Published: December 2006

Congenital Disorders of Glycosylation (CDG) are a group of recessive genetic disorders characterized by hypoglycosylation of glycoproteins. CDG‐Ia, the most common type, is caused by mutations in the PMM2 gene, coding for a phosphomannomutase (PMM2; EC 5.4.2.8). The mutational spectrum of PMM2 comprises more than 80 different mutations but one of them, R141H, is particularly interesting due to its high frequency among CDG‐Ia patients worldwide. In contrast, other mutations are ethnically or geographically restricted, such as D65Y which is only found in patients of Iberian ancestry.

In the present study a population genetic approach was used in an attempt to clarify the origins of two important disease causing mutations: R141H and D65Y. Based on SNP and STR genotypic analysis, we ascertained an association between the R141H substitution and a particular haplotype, suggesting a common origin for all the mutated chromosomes. Similar results were found for D65Y, although the associated haplotype was different from that of R141H, suggesting independent origins for these two mutations. Our results enable us to infer an Iberian origin for the D65Y mutation.
Association of a Common Interferon Regulatory Factor 5 (IRF5) Variant with Increased Risk of Systemic Lupus Erythematosus (SLE)
Authors: Demirci F. Y. K. , Manzi S. , Ramsey‐Goldman R. , Minster R. L. , Kenney M. , Shaw P. S. , Dunlop‐Thomas C. M. , Kao A. H. , Rhew E. , Bontempo F. , Kammerer C. , Kamboh M. I.
Published: December 2006

Interferon regulatory factor 5 (IRF5) belongs to a family of transcription factors that control the transactivation of type I interferon system‐related genes, as well as the expression of several other genes involved in immune response, cell signalling, cell cycle control and apoptosis. Two recent studies reported a significant association between the IRF5/rs2004640 T allele and systemic lupus erythematosus (SLE). The purpose of this study was to determine whether the reported rs2004640 T allele association could be replicated in our independent SLE case‐control sample. We genotyped DNA samples from 370 white SLE‐affected female subjects and 462 white healthy female controls using the TaqMan Assay‐on‐Demand for rs2004640, and performed a case‐control genetic association analysis. Frequency of the rs2004640 T allele was significantly higher in cases than in controls (56.5% vs. 50%; P= 0.008). The odds ratio for T allele carriers was 1.68 (95% CI: 1.20 – 2.34; P= 0.003). Our results in an independent case‐control sample confirm the robust association of the IRF5/rs2004640 T allele with SLE risk, and further support the relevance of the type I interferon system in the pathogenesis of SLE and autoimmunity.