bluuebunny/crossref_metadata_2025 huggingface dataset:
The environmental status of a Kashmir Himalayan wetland game reserve: Aquatic plant communities and eco‐restoration measures
Authors: Khan M. A. , Shah M. A. , Mir S. S. , Bashir Suzana
Published: August 2004

The data (November 2000 – October 2001) are presented on environmental status, hydrology, sedimentation rate, water quality and macrophytic community architecture of an important game reserve (Hokersar Wetland) in the Kashmir Himalayan valley. Of the total water input, 91% was contributed from surface inlets and just 9% through precipitation. Of the total surface water output, 67% occurred through outlets while evapotranspiration and other losses accounted for 33%. The net annual sediment accumulation was principally a function of suspended load carried by Doodganga inlet. The ecosystem supports diverse aquatic plant communities (emergents, rooted–floating leaf type, free‐floating leaf type, submersed type) marked by striking variability in composition, frequency and extent of colonization. Several ecological factors, such as habitat loss related to siltation, pollution, expanding agricultural activities and drastic hydrological fluctuations, have induced considerable changes in the dynamics and distribution pattern of sustained biota. The shift in macrophytic community structure is evidenced by the decline of Nelumbio nucifera and the near‐disappearance of some economically important plants (Euryale ferox, Acorus calamus). The shrinkage of the wetland area, once spread over 1800 ha, by ≈28% is a cause for environmental concern. The paper highlights the rapidly deteriorating environmental status of the Kashmir Himalayan Hokersar Wetland game reserve and stresses the need for its urgent ecological restoration.
Equations for designing tidally affected harbours and lagoons, and for calculating water exchange in coast‐connected lakes
Authors: Essa Sawsan S.
Published: August 2004

A three‐dimensional flow and transport model was used to simulate the flow of water and assumed conservative substance in a large number of hypothetical, sea‐connected lagoons and harbours experiencing tidal effects. The dimensions of the lagoons and harbours were selected to cover a wide range of widths, lengths, depths and entrance channel widths. The tidal flow in and out of each lagoon and harbour was simulated for durnal and semidurnal conditions for different tidal ranges. The water exchange for each lagoon and harbour was assessed on the basis of the exchange coefficient. The results of model runs and non‐linear multiple regression techniques were used to develop equations for calculating the average exchange, in terms of lagoon dimensions, depth and tidal range for durnal and semidurnal conditions. These equations can be used for a quick assessment of water exchange conditions in lagoons and harbours, upon which their water quality depends. In designing an artificial, sea‐connected lagoon and harbour, the developed equations can be used in the preliminary stages for testing options regarding the number and widths of entrances and the physical layout of the lagoon and harbour. This approach also allows for identification of unsuitable options, with the acceptable options being subjected to detailed mathematical modelling to assess their expected water exchange and water quality. The same approach can be applied to existing lagoons (natural or artificial) and harbours in designing layout modifications for improving water exchange and water quality conditions, as well as lakes directly connected to coastal waters and subject to tidal effects. The use of the equations presented in this report also can provide knowledge regarding the preferred water flushing conditions and/or improvements needed to enhance the water exchange in order to preserve the ecosystems in such water systems.
Identifying sources and effects of carer fatigue and burnout for mental health nurses: a qualitative approach
Authors: Taylor Bev , Barling Jan
Published: August 2004

ABSTRACT: This project aimed to: identify work‐related problems to assist mental health nurses to locate the sources and effects of carer fatigue and burnout, set up a dialogue between the participants and the identified sources of stress in the workplace to address the identified problems, and make recommendations to a local Area Health Service to prevent and manage stressors in the practice of mental health nursing. In total, 20 experienced registered nurses working as mental health nurses were enlisted through a snowballing method of recruitment, and convenience sampling was used to intentionally target those research participants who were interested in identifying sources of carer fatigue and burnout in their work. Data collection was via semistructured interviews which used questions reflecting the first stage of

White and Epston's (1990

) method of narrative therapy, in which relative influence questioning is used to externalize the problem. The research questions related to the effect of burnout in mental health nursing across various interfaces, through the dominant story of emotional stress and fatigue. The sources of work‐related problems for mental health nurses that contribute towards their experiences of carer fatigue and burnout were: employment insecurity and casualization of the work‐force; issues with management and the system; difficulties with the nature of the work, inadequate resources and services, problems with doctors, aggressive and criminal consumers

*

, undervaluing consumers and nurses, physical and emotional constraints of the work setting, and nurse−nurse relationships and horizontal violence. The effects of stress were shown in dealing with and reacting to work place stressors.
Lower rhombic lip‐derived cells undergo transmedian tangential migration followed by radial migration in the chick embryo brainstem
Authors: Ono Katsuhiko , Yasui Yukihiko , Ikenaka Kazuhiro
Published: August 2004

Migration behaviour and fate of cells originated from the lower rhombic lip (LRL) was examined in the chick embryo hindbrain. LRL‐derived cells tangentially migrate along the pial surface of the brainstem and form a transient subpial migratory stream. In the initial stages of migration, LRL‐derived cells appose each other or axon‐like processes, which is indicative of mode of homophilic chain migration and/or axophilic migration. Some LRL‐derived cells relocate rostroventrally towards the pontine region, although the majority of them migrate circumferentially to the ventral medulla oblongata. Depending on the stage of generation, LRL‐derived cells undergo transmedian migration; late‐generated LRL‐derived cells preferentially colonize the contralateral brainstem compared with early generated cells. Thus, latecomer neuron precursors may migrate past their predecessors in the migratory stream. When LRL‐derived cells leave the subpial migratory stream, they change their migratory direction to a radial one and relocate inwardly, with a profile that resembles a tangential‐to‐radial change seen in cerebellar granule cell precursors. After they enter the parenchymal region of the brainstem, they exhibited morphological differentiation, and some differentiate into excitatory neurons. The present results suggest that LRL‐derived cells migrate across boundaries such as midline or rhombomere, which may facilitate to build up cellular and functional architectures of the hindbrain.
Cognitive tuning of corticospinal excitability during human gait: adaptation to the phase
Authors: Camus Mickael , Pailhous Jean , Bonnard Mireille
Published: August 2004

The aim of this study was to investigate how the cognitive tuning of corticospinal (CS) excitability adapts to the type of evoked‐movement (Flexion vs. Extension) during human gait. Transcranial magnetic stimulation (TMS) was used both as a central perturbation evoking a movement and as a tool for quantifying the CS excitability of the muscles under study (RF/BF). In the first condition (Dst), the TMS occurred at mid‐stance, inducing hip extension, whereas in the second condition (Dsw), the TMS occurred at the beginning of the swing phase, inducing hip flexion. In both conditions, the subjects were asked to cognitively prepare to either not intervene (NINT) or to compensate (COMP) for the evoked‐movements. The results showed that, regardless of the type of evoked‐movement, preparing to compensate resulted in a selective increase in the CS excitability to those muscles that would be involved in counteracting the possible central perturbation, i.e. the hip extensor muscle (BF) to compensate for an evoked flexion during the swing phase or the hip flexor muscle (RF) to compensate for an evoked extension during the stance phase. This latter result offers the first evidence of a modulation in CS excitability to the proximal muscles during the stance phase. In conclusion, the cognitive tuning of CS excitability was found to adapt to the gait phases. Moreover, the same selective preparation strategy was observed whether the central perturbation occurred during the stance or the swing phase of the step cycle.
Nerve terminals of squid photoreceptor neurons contain a heterogeneous population of mRNAs and translate a transfected reporter mRNA
Authors: Gioio Anthony E. , Lavina Zeno Scotto , Jurkovicova Dana , Zhang Hengshan , Eyman Maria , Giuditta Antonio , Kaplan Barry B.
Published: August 2004

It is now well established that the distal structural/functional domains of the neuron contain 2a diverse population of mRNAs that program the local synthesis of protein. However, there is still a paucity of information on the composition and function of these mRNA populations in the adult nervous system. To generate empirically, hypotheses regarding the function of the local protein synthetic system, we have compared the mRNAs present in the squid giant axon and its parental cell bodies using differential mRNA display as an unbiased screen. The results of this screen facilitated the identification of 31 mRNAs that encoded cytoskeletal proteins, translation factors, ribosomal proteins, molecular motors, metabolic enzymes, nuclear‐encoded mitochondrial mRNAs, and a molecular chaperone. Results of cell fractionation and RT‐PCR analyses established that several of these mRNAs were present in polysomes present in the presynaptic nerve terminal of photoreceptor neurons, indicating that these mRNAs were being actively translated. Findings derived from in vitro transfection studies established that these isolated nerve terminals had the ability to translate a heterologous reporter mRNA. Based upon these data, it is hypothesized that the local protein synthetic system plays an important role in the maintenance/remodelling of the cytoarchitecture of the axon and nerve terminal, maintenance of the axon transport and mRNA translation systems, as well as contributing to the viability and function of the local mitochondria.
Dissociation in the effects of neonatal maternal separations on maternal care and the offspring's HPA and fear responses in rats
Authors: Macrí Simone , Mason Georgia J. , Würbel Hanno
Published: August 2004

The development of the hypothalamic–pituitary–adrenal (HPA) response to stress is influenced by the early mother–infant relationship. In rats, early handling (brief daily mother–offspring separations) attenuates the adult offspring's HPA and fear responses compared to both nonhandling (no separations) and maternal separation (prolonged daily separations). It has been proposed that variation in the amount of maternal care mediates these effects of neonatal manipulations on the adult offspring's stress and fear responses. Here we tested this hypothesis by assessing maternal care and the adult offspring's HPA and fear responses in Lister hooded rats which were subjected to either early handling (EH) or maternal separation (MS) from postnatal day 1–13, or were left completely undisturbed (nonhandled, NH) throughout this period. Both EH and MS induced a more active nursing style and elevated levels of maternal care compared to NH. Total levels of maternal care were indistinguishable between EH and MS, but diurnal distribution differed. MS dams showed elevated levels of maternal care following the 4‐h separation period, thereby fully compensating for the amount of maternal care provided by EH dams during the time MS dams were separated from their pups. However, while EH resulted in reduced HPA and fear responses in the adult offspring compared to NH, MS and NH offspring did not differ. Our findings therefore demonstrate dissociation in the effects of EH and MS on maternal care and on the stress and fear responses in the offspring. This indicates that maternal care cannot be the sole mediator of these effects.
Experience‐dependent changes in the hippocampus of domestic chicks: a model for spatial memory
Authors: Freire Rafael , Cheng Heng‐Wei
Published: August 2004

In the domestic chicken, providing visual barriers for a brief period early in life has been found to improve spatial memory [R. Freire et al. (2004)Animal Behaviour, 67, 141–150]. In the present study we compared the structure of neurons in the hippocampus and neostriatum in chicks reared with or without visual barriers. From 8 to 16 days of age, chicks were reared in pens either with two wooden screens (Treatment E) or with no screens (Treatment C). At 16 days of age, chicks were anaesthetized, perfused intracardially and brain samples collected and stained using a Golgi–Cox technique. Morphometric analysis revealed that the multipolar projection neurons of Treatment E chicks had longer dendrites (anova, F1,14 = 7.4, P < 0.05) and had more spines per 20 µm of dendrite (SLD; anova, F1,14 = 10.6, P < 0.01) than those of Treatment C chicks. By contrast, no evidence was found that rearing treatment differentially influences dendrite length or SLD in the neostriatum, suggesting that the above environment‐induced changes may be specific to the hippocampus. Multipolar projection neuron dendrites of the right hemisphere were longer (anova, F1,14 = 36.4, P < 0.0001) and had more spines (anova, F1,14 = 8.8, P < 0.05) than dendrites of the left hemisphere, supporting previous findings that the right hemisphere of chickens is predominantly involved in spatial processing. We conclude that the chicken provides a useful model for the study of developmental plasticity in brain and behaviour, partly because the possibility of rearing chicks in isolation and imprinting them on an artificial object provides a means of accurately manipulating early experience.
Regulation of striatal tyrosine hydroxylase phosphorylation by acute and chronic haloperidol
Authors: Håkansson Kerstin , Pozzi Laura , Usiello Alessandro , Haycock John , Borrelli Emiliana , Fisone Gilberto
Published: August 2004

The typical neuroleptic haloperidol increases the state of phosphorylation and activity of tyrosine hydroxylase (TH), the rate‐limiting enzyme in the synthesis of catecholamines. Here we show that the increases in TH phosphorylation produced by haloperidol at Ser31 and Ser40, two sites critically involved in the regulation of enzymatic activity, are abolished in dopamine D2receptor‐null mice and mimicked by the selective dopamine D2receptor antagonist, eticlopride. Moreover, the ability of haloperidol and eticlopride to stimulate phosphorylation at both seryl residues is prevented by treatment with SL327, a compound that blocks activation of extracellular signal‐regulated protein kinases 1 and 2 (ERK1/2). We also show that chronic administration of haloperidol reduces the basal levels of phosphoSer31‐TH and decreases the ability of the drug to stimulate Ser40 phosphorylation. These results provide a model accounting for the stimulation exerted by haloperidol on dopamine synthesis. According to this model, haloperidol increases TH activity via blockade of dopamine D2receptors, disinhibition of dopaminergic projection neurons and ERK1/2‐dependent phosphorylation of TH at Ser31 and Ser40. These studies also show that lower levels of phosphorylated TH are associated with chronic neuroleptic treatment and may be related to depressed dopaminergic transmission in nigrostriatal neurons.
Central blockade of muscarinic cholinergic receptors disrupts affective and attentional set‐shifting
Authors: Chen Katy C. , Baxter Mark G. , Rodefer Joshua S.
Published: August 2004

Impairments in multiple aspects of attentional and executive function follow damage to cholinergic neurons in the central nervous system. Affective and attentional set‐shifting represent two aspects of executive function controlled by different sectors of the prefrontal cortex. The involvement of cholinergic neural mechanisms in these aspects of executive function has not been specified. To determine whether central muscarinic cholinergic receptors were involved in affective and/or attentional set‐shifting, we tested rats on a series of discrimination learning problems, which included affective (reversal learning) and attentional set (extradimensional shift)‐shifting components, under the systemic influence of scopolamine, a muscarinic antagonist. Scopolamine impaired both reversal learning and extradimensional shifting, but was without effect on learning new discrimination problems that did not require an affective or attentional shift. Systemic administration of methylscopolamine, which does not cross the blood–brain barrier, did not impair affective or attentional set‐shifting, indicating that the scopolamine effects were centrally mediated. These data implicate muscarinic receptors in the central nervous system in the control of executive function. Taken together with other recent data, they may also suggest an important role for cholinergic receptors outside of the neocortex in regulating these aspects of attention and executive function.
Repeated sensory contact with aggressive mice rapidly leads to an anticipatory increase in core body temperature and physical activity that precedes the onset of aversive responding
Authors: Pardon Marie‐Christine , Kendall David A. , Pérez‐Diaz Fernando , Duxon Mark S. , Marsden Charles A.
Published: August 2004

The present study investigated whether the ‘psychological threat’ induced by sensory contact with an aggressive conspecific would be a sufficient factor in inducing behavioural and physiological disturbances. Repeated sensory contact with an aggressive mouse (social threat) in a partitioned cage was compared with repeated exposure to a novel partitioned cage in male NMRI mice. We first examined parameters of stress responsiveness (body weight, plasma corticosterone levels, frequency of self‐grooming and defecation). The temperature and physical activity responses to stress were also recorded during and after the 4 weeks of stress using radiotelemetry. Finally, cognitivo‐emotional performance was assessed after acute stress and 2 and 4 weeks of stress by measuring decision making, sequential alternation performance and behaviour in the elevated T‐maze. Social threat had a greater impact than novel cage exposure on most parameters of stress responsiveness, although mice did not habituate to either stressor. Social threat rapidly led to an anticipatory rise in core body temperature and physical activity before the scheduled stress sessions. Such anticipation developed within the first week and persisted for 9 days after ending the stress procedure. Some memory impairment in the sequential alternation test was found in stressed mice, independent of the stressor. After 4 weeks of stress, inhibitory avoidance in the elevated T‐maze was enhanced in socially stressed mice and reduced in novel cage mice. The sustained anticipation of stress in the social threat group preceded aversive responding. It remains to be established whether anticipation contributes to the development of aversive responses.
Hypoxia induces caspase‐9 and caspase‐3 activation without neuronal death in gerbil brains
Authors: Garnier Philippe , Prigent‐Tessier Anne , Van Hoecke Michaël , Bertrand Nathalie , Demougeot Céline , Sordet Olivier , Swanson Raymond A. , Marie Christine , Beley Alain
Published: August 2004

To investigate the in vivo apoptotic machinery in oxygen deprived brain, we examined the expression of caspase‐9 and caspase‐3 in the hippocampus of Mongolian gerbils subjected to either transient hypoxia (4% O2 for 6 min) or forebrain ischemia (10 min bilateral carotid artery occlusion) followed by 8 h to 7 days of reoxygenation or blood recirculation. Apoptotic death was characterized by isolating hippocampal genomic DNA and analysing DNA fragmentation as well as histological studies including TUNEL assay and toluidine blue staining of brain sections. The results showed that both hypoxic and ischemic gerbil brains exhibited an increase in caspase‐9 and caspase‐3 gene expression. However, no cell damage was detectable following hypoxia, while marked DNA fragmentation and extensive cell death was observed following ischemia. Moreover, although hypoxia did not lead to cell death, both hypoxia and ischemia were associated with cleavage of procaspase‐9 and procaspase‐3 and increases in their activities as well as cleavage of poly(ADP‐ribose) polymerase‐1 (PARP‐1), a major caspase‐3 substrate. These results indicate that, in vivo, even late apoptotic events such as caspase activation and PARP‐1 cleavage in hypoxic brains do not necessarily induce an irreversible commitment to apoptotic neuronal death.
Altered agonist sensitivity and desensitization of neuronal mGluR1 responses in knock‐in mice by a single amino acid substitution at the PKC phosphorylation site
Authors: Sato Masaaki , Tabata Toshihide , Hashimoto Kouichi , Nakamura Kenji , Nakao Kazuki , Katsuki Motoya , Kitano Jun , Moriyoshi Koki , Kano Masanobu , Nakanishi Shigetada
Published: August 2004

mGluR1 and mGluR5 of the metabotropic glutamate receptor family are coupled to inositol trisphosphate–Ca2+ signal cascades and evoke distinct Ca2+ responses in neural cells and heterologously expressing cells. In heterologous cells, stimulation of recombinant mGluR1 evokes a single‐peaked Ca2+ response whereas mGluR5 elicits an oscillatory Ca2+ response. The distinct Ca2+ responses are interchangeable by single amino substitution of aspartate for threonine at the corresponding position of the carboxy‐terminal cytoplasmic regions of mGluR1 and mGluR5, respectively. In this investigation, we generated knock‐in mice, termed mGluR1 D854T mice, in which aspartate of mGluR1 was replaced with threonine. We examined the effect of this D854T substitution on Ca2+ and current responses mediated by mGluR1 in cultured cerebellar Purkinje cells. Stimulation of mGluR1 D854T by a group 1 mGluR agonist, 3,5‐dihydroxyphenylglycine (DHPG) evoked, as in wild‐type mGluR1, only single‐peaked Ca2+ responses as measured by Ca2+ fluorometric analysis. We then examined mGluR1‐induced inward currents carried by nonselective cation channels during whole‐cell recordings from cultured Purkinje cells. The mGluR1 D854T mutation abolished the responsiveness of mGluR1 to low concentrations of DHPG (0.5–500 nm) and reduced its desensitization during prolonged agonist application. mGluR1 D854T homozygous mutants showed no apparent behavioural abnormality as analysed by motor movement tests. These results indicate that, although additional modulatory mechanisms seem to be required to produce oscillatory Ca2+ responses of mGluR1, the single amino acid substitution at position 854 of mGluR1 is capable of influencing the kinetics of neuronal mGluR1 responses, most probably through PKC‐mediated phosphorylation.
Inwardly rectifying potassium channels in rat retinal ganglion cells
Authors: Chen Ling , Yu Yong‐Chun , Zhao Jing‐Wei , Yang Xiong‐Li
Published: August 2004

Inwardly rectifying potassium channels (Kir channels) are important for neuronal signalling and membrane excitability. In the present work we characterized, for the first time, Kir channels in rat retinal ganglion cells (RGCs), the output neurons in the retina, using immunocytochemical and patch‐clamp techniques. Various subunits of Kir channels (Kir1.1, 2.1, 2.3, 3.1, 3.2 and 3.3) were expressed in RGCs, but with distinct subcellular localization. Kir1.1 was mainly expressed in axons of RGCs. Kir2.1 and Kir2.3 were both present in somata of RGCs. Whereas staining for Kir3.1 was profoundly present in an endoplasmic reticulum‐like structure and Kir3.2 was strongly expressed in the cytoplasm and the cytomembrane of somata, dendrites and axons of RGCs, faint, sparse labelling for Kir3.3 was seen in the cytomembrane. Immunoreactivity for Kir4.1 and Kir4.2 was not detectable in RGCs. Whole‐cell currents mediated by Kir channels were recorded in isolated RGCs and they differed from hyperpolarization‐activated currents (Ih) by showing full activation in < 10 ms, no inactivation, and being significantly suppressed by 300 µm Ba2+. Unlike in retinal horizontal cells and bipolar cells, these currents were mainly mediated by G‐protein‐coupled Kir3 (GIRK) channels, as demonstrated by the fact that GDPβS and GTPγS included in the pipette solution markedly decreased and increased the currents, respectively. Furthermore, the GIRK channels were probably coupled to GABAB receptors, because baclofen considerably increased the Kir currents and the increased currents were suppressed by Ba2+. These characteristics of the Kir currents provide more versatility for signalling of RGCs.
Rhythmic regulation of membrane potential and potassium current persists in SCN neurons in the absence of environmental input
Authors: Kuhlman Sandra J. , McMahon Douglas G.
Published: August 2004

Neurons of the mammalian suprachiasmatic nucleus (SCN) generate self‐sustained rhythms of action potential frequency having a period of approximately 24 h. It is generally believed that cell autonomous circadian oscillation of a network of biological clock genes drives the circadian rhythm in neuronal firing rate through as yet unspecified effects on the neuronal membrane. While it is clear that cyclic gene expression continues in constant darkness, previous studies have not examined which specific membrane properties of SCN neurons continue to oscillate in constant conditions. Here, we demonstrate that SCN neurons exhibit robust rhythms in resting membrane potential and input resistance in constant darkness. Furthermore, application of the K+ channel blocker tetraethylammonium revealed a rhythm in K+ current amplitude that persists in constant darkness and underlies the rhythm in membrane potential.
Genetic deletion and pharmacological blockade of CB1 receptors modulates anxiety in the shock‐probe burying test
Authors: Degroot Aldemar , Nomikos George G.
Published: August 2004

Cannabinoids affect various behavioral processes, including emotion, learning and memory, which may bspecifically regulated through the CB1 receptors. The exact role CB1 receptors play in anxiety remains unclear. Both genetic and pharmacological blockade of CB1 receptors have produced inconsistent effects on anxiety. However, these studies examined passive avoidance as an index of anxiety. In the present study, both active and passive avoidance were examined using the shock‐probe burying test while CB1 receptors were blocked genetically or pharmacologically. In the shock‐probe burying test, anxiety is reflected by increased burying (increased active avoidance) and increased freezing (increased passive avoidance). In addition, probe‐contacts may reflect cognitive performance and/or passive avoidance. As there have been few studies examining mouse behavior in the shock‐probe burying test, experiment 1 was designed to pharmacologically validate this model in mice. Our results indicated that administration (i.p.) of chlordiazepoxide (4 mg/kg) or FG7412 (5 mg/kg) decreased and increased burying behavior, respectively, without affecting freezing or the number of probe contacts. Experiments 2 and 3 showed that both CB1 knockout mice and mice injected (i.p.) with 3 or 10 mg/kg, but not 1 mg/kg, of the CB1 receptor antagonist SR141716A had lower burying scores, fewer contacts with the probe and similar freezing times compared with wild‐type mice and mice injected with vehicle (experiments 2 and 3). Collectively, these results suggest that CB1 receptor blockade reduces some, but not all, aspects of anxiety. The decrease in probe contacts induced by CB1 receptor blockade may be due to enhanced cognition.
Effects of sensory deprivation on columnar organization of neuronal circuits in the rat barrel cortex
Authors: Schierloh Anja , Eder Matthias , Zieglgänsberger Walter , Dodt Hans‐Ulrich
Published: August 2004

We examined whether sensory deprivation during formation of the cortical circuitry influences the pattern of intracortical single‐cell connections in rat barrel cortex. Excitatory postsynaptic potentials (EPSPs) from layer 2/3 (L2/3) pyramidal neurons were recorded in vitro using patch‐clamp techniques. In order to evoke EPSPs, presynaptic neurons were stimulated by photolytically applied glutamate, thus generating action potentials. Synaptic connections between the stimulated and the recorded neuron were identified by the occurrence of PSPs following photostimulation. Sensory deprivation changed the pattern of projections from L4 and L2/3 neurons to L2/3 pyramidal cells. In slices of non‐deprived rats 86% of the total presynaptic neurons were located in the first and only 10% in the second barrel column. Deprivation changed these values to 67% and 26%, respectively. Therefore, the probability of presynaptic cells projecting to L2/3 neurons was shifted from adjacent to more remote barrel columns. These results indicate that deprivation of sensory input influences the pattern of intracortical connections.
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

Although 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

In 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

We 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

We 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

Dopamine 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

Bystin 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

Recent 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

Peripheral 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

Dopamine 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

Bacterial 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.