bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic changes of the anti‐ and pro‐apoptotic proteins Bcl‐w, Bcl‐2, and Bax with Smac/Diablo mitochondrial release after photothrombotic ring stroke in rats
Authors: Hu Xiao‐Lei , Olsson Tommy , Johansson Inga‐Maj , Brännström Thomas , Wester Per
Published: September 2004

The anti‐apoptotic proteins Bcl‐w and Bcl‐2 and the pro‐apoptotic protein Bax may mediate cell death or survival via regulation of the mitochondria including second mitochondria‐derived activator of caspase (Smac)/direct inhibitor of apoptosis protein (IAP)‐binding protein with low pI (DIABLO) release. This study aimed to explore alterations in Bcl‐w, Bcl‐2, and Bax and the relationship between these proteins and Smac/DIABLO by means of in situ hybridization, immunohistochemical (IHC) staining, and Western blots after low‐ and high‐intensity photothrombotic ring stroke. At 4 h after low‐intensity irradiation, we found widespread bcl‐w overexpression on both the mRNA and protein levels in the bilateral cortex except the ring lesion region and in subcortical regions. A prolonged elevation of Bcl‐2 with relatively unchanged Bax in the mitochondrial fraction was demonstrated from 4 to 72 h. These upregulated anti‐apoptotic proteins combined with little Smac/DIABLO release might be associated with increased cell survival and thereby remarkable morphological recovery after low‐intensity irradiation. After high‐intensity irradiation, we observed decreased bcl‐w and bcl‐2 mRNA with increased Bcl‐2 protein in the cytosolic fraction, whereas the Bax protein remained in scattered ischaemic cells in the ring lesion and the region at risk that corresponded with release of Smac/DIABLO from mitochondria to the cytosol at 1–24 h. These changes might be related to the massive cell death observed after high‐intensity irradiation. Taken together, the balance and the location of anti‐apoptotic proteins vs. pro‐apoptotic proteins could be associated with the translocation of Smac/DIABLO from the mitochondria to the cytosol and therefore closely related to cell death or survival after focal cerebral ischaemia.
Long‐term changes in the molecular composition of the glial scar and progressive increase of serotoninergic fibre sprouting after hemisection of the mouse spinal cord
Authors: Camand Emeline , Morel Marie‐Pierre , Faissner Andréas , Sotelo Constantino , Dusart Isabelle
Published: September 2004

The scarring process occurring after adult central nervous system injury and the subsequent increase in the expression of certain extracellular matrix molecules are known to contribute to the failure of axon regeneration. This study provides an immunohistochemical analysis of temporal changes (8 days to 1 year) in the cellular and molecular response of the Swiss mouse spinal cord to a dorsal hemisection and its correlation with the axonal growth properties of a descending pathway, the serotoninergic axons. In this lesion model, no cavity forms at the centre of the lesion. Instead, a dense fibronectin‐positive tissue matrix occupies the centre of the lesion, surrounded by a glial scar mainly constituted by reactive astrocytes. NG2 proteoglycan and tenascin‐C, potential axon growth inhibitors, are constantly associated with the central region. In the glial scar, tenascin‐C is never observed and the expression of chondroitin sulphate proteoglycans (revealed with CS‐56 and anti‐NG2 antibodies) highly increases in the week following injury to progressively return to their control level. In parallel, there is an increasing expression of the polysialilated neural cell adhesion molecule by reactive astrocytes. These molecular changes are correlated with a sprouting process of serotoninergic axons in the glial scar, except in a small area in contact with the central region. All these observations suggest that while a part of the glial scar progressively becomes permissive to axon regeneration after mouse spinal cord injury, the border of the glial scar, in contact with the fibronectin‐positive tissue matrix, is the real barrier to prevent axon regeneration.
Brain‐derived neurotrophic factor controls functional differentiation and microcircuit formation of selectively isolated fast‐spiking GABAergic interneurons
Authors: Berghuis Paul , Dobszay Marton B. , Sousa Kyle M. , Schulte Gunnar , Mager Peter P. , Härtig Wolfgang , Görcs Tamás J. , Zilberter Yuri , Ernfors Patrik , Harkany Tibor
Published: September 2004

GABAergic interneurons with high‐frequency firing, fast‐spiking (FS) cells, form synapses on perisomatic regions of principal cells in the neocortex and hippocampus to control the excitability of cortical networks. Brain‐derived neurotrophic factor (BDNF) is essential for the differentiation of multiple interneuron subtypes and the formation of their synaptic contacts. Here, we examined whether BDNF, alone or in conjunction with sustained KCl‐induced depolarization, drives functional FS cell differentiation and the formation of inhibitory microcircuits. Homogeneous FS cell cultures were established by target‐specific isolation using the voltage‐gated potassium channel 3.1b subunit as the selection marker. Isolated FS cells expressed parvalbumin, were surrounded by perineuronal nets, formed immature inhibitory connections and generated slow action potentials at 12 days in vitro. Brain‐derived neurotrophic factor (BDNF) promoted FS cell differentiation by increasing the somatic diameter, dendritic branching and the frequency of action potential firing. In addition, BDNF treatment led to a significant up‐regulation of synaptophysin and vesicular GABA transporter expression, components of the synaptic machinery critical for GABA release, which was paralleled by an increase in synaptic strength. Long‐term membrane depolarization alone was detrimental to dendritic branching. However, we observed that BDNF and KCl exerted additive effects, as reflected by the significantly accelerated maturation of synaptic contacts and high discharge frequencies, and was required for the formation of reciprocal connections between FS cells. Our results show that BDNF, along with membrane depolarization, is critical for FS cells to establish inhibitory circuitries during corticogenesis.
Deletion of the adenosine A1 receptor gene does not alter neuronal damage following ischaemia in vivo or in vitro
Authors: Olsson Tomas , Cronberg Tobias , Rytter Anna , Asztély Fredrik , Fredholm Bertil B. , Smith Maj‐Lis , Wieloch Tadeusz
Published: September 2004

Extracellular adenosine is dramatically increased during cerebral ischaemia and is considered to be neuroprotective due to its inhibitory effect on synaptic transmission mediated by the adenosine A1 receptor (A1R). We investigated the importance of the A1R in a mouse model of global ischaemia and in a murine hippocampal slice culture model of in vitro ischaemia, using mice with the A1R gene deleted. In brains from mice lacking the A1R, damage induced by global ischaemia was similar to that in wild‐type animals. In contrast, treatment with a selective A1R antagonist [8‐cyclo‐pentyl theophylline (8‐CPT)], administered before the ischaemic insult in naive wild‐type mice, exacerbated the neuronal damage following global ischaemia. Although the inhibitory action of adenosine on excitatory neurotransmission in hippocampal slices was lost in A1R knockout mice, there was no difference in damage between slices from wild‐type and knockout mice after in vitro ischaemia. The results suggest that some effects of the A1R are compensated for in knockout animals.
Independent coding of connected environments by place cells
Authors: Paz‐Villagrán V. , Save E. , Poucet B.
Published: September 2004

Place cells are hippocampal neurons that have a strong location‐specific firing activity in the rat's current environment. Collectively, place cells also provide a signature of the rat's environment as their ensemble activity is markedly different when recorded in distinct apparatuses. This phenomenon, referred to as ‘remapping’, suggests that each environment activates a different hippocampal map. In this study, we sought to determine the independence of such maps. In Experiment 1, we used a cylinder apparatus that was divided into two equal halves by a central barrier with an aperture allowing the rat to freely commute between the two sides. A local change in one side failed to induce field remapping in the changed side, thus precluding any significant conclusion to be drawn. We therefore designed Experiment 2 in which place cells were first recorded while rats explored three distinct high‐walled boxes. Most cells had distinctive firing fields in each box. A runway was then added to connect two initially unrelated boxes. This manipulation altered the firing of some cells but the fields in each box were still clearly distinguishable. The final manipulation consisted of changing one box and allowing the rat to commute freely between the changed and unchanged boxes. While the firing fields remapped in the changed box, they were most usually unaltered in the unchanged box. These results suggest that the hippocampus holds a set of independent maps for each box, and that each specific map is activated mainly according to the rat's current sensory environment.
Optical detection of neural function in the chick visual pathway in the early stages of embryogenesis
Authors: Miyakawa Naohisa , Sato Katsushige , Momose‐Sato Yoko
Published: September 2004

We investigated the developmental pattern of functional synaptogenesis in the chick visual pathway using a multiple‐site optical recording method. Responses to optic nerve stimulation were recorded from the diencephalon and mesencephalon of the chick embryo. The first excitatory postsynaptic responses to optic nerve stimulation appeared in the contralateral diencephalon at Hamburger–Hamilton stage 27, which corresponds to an incubation day 5.5 (E5.5). At more developed stages, the optical signals evoked by optic nerve stimulation spread to several different regions, including the tectum and extra‐tectal visual nuclei. We constructed maps of neural activity in the diencephalon and mesencephalon at different stages to investigate the spatio‐temporal patterns of functional development in the chick visual system. The maps revealed that distinct postsynaptic response areas in the extra‐tectal regions showed different onsets of activity, suggesting that the corresponding visual nuclei exhibit different time courses of functional synaptogenesis. We also identified the onset and location of the first functional synaptic connection in the optic tectum, which had been a point of controversy in earlier studies. In the tectal region, the action potential and the excitatory postsynaptic potential first appeared at E8, although these signals were recognized in the tecto/tegmental region at E7. The response area expanded with retinotectal fibre elongation, and reached the area centralis at E9. These results show that the onset of synaptic function in the tectum occurs 2–3 days earlier than was previously reported.
Effects of muscarinic acetylcholine receptor activation on membrane currents and intracellular messengers in medium spiny neurones of the rat striatum
Authors: Lin John Y. , Chung Kenny K. H. , De Castro Denis , Funk Gregory D. , Lipski Janusz
Published: September 2004

Acetylcholine, acting through muscarinic receptors, modulates the excitability of striatal medium spiny neurones. However, the underlying membrane conductances and intracellular signalling pathways have not been fully determined. Our aim was to characterize excitatory effects mediated by M1 muscarinic acetylcholine receptors in these neurones using whole‐cell patch‐clamp recordings in brain slices of postnatal rats. Under voltage‐clamp, muscarine evoked an inward current associated with an increase in cell membrane resistance. The current, which reversed at −85 mV, was sensitive to the M1 receptor antagonist pirenzepine. Blocking the potassium conductance attenuated the response and the residual current was further reduced by ruthenium red (50 µm) and reversed at +15 mV. Simultaneous recordings from cholinergic interneurones and medium spiny neurones in conjunction with spike‐triggered averaging revealed small unitary excitatory postsynaptic currents in four of 39 cell pairs tested. The muscarine‐induced inward current was attenuated by a phospholipase C (PLC) inhibitor, U73122, but not by a protein kinase C inhibitor, chelerythrine, or by the intracellular calcium chelator 1,2‐bis(2‐aminophenoxy) ethane‐N,N,N′,N′‐tetra‐acetic acid, suggesting that the current was associated with PLC in a protein kinase C‐ and Ca2+‐independent manner. The phosphatidylinositol 4‐kinase inhibitor wortmannin (10 µm) reduced the recovery of the inward current, indicating that the recovery process was dependent on the removal of diacylglycerol and/or inositol 1,4,5 triphosphate or resynthesis of phospholipid phosphatidylinositol 4,5‐bisphophate. Ratiometric measurement of intracellular calcium after cell loading with fura‐2 demonstrated a muscarine‐induced increase in calcium signal that originated mainly from intracellular stores. Thus, the cholinergic excitatory effect in striatal medium spiny neurones, which is important in motor disorders associated with altered cholinergic transmission in the striatum such as Parkinson's disease, is mediated through M1 receptors and the PLC‐dependent pathway.
Integration and differentiation of neural stem cells after transplantation into the dysmyelinated central nervous system of adult mice
Authors: Ader Marius , Schachner Melitta , Bartsch Udo
Published: September 2004

Mutant mice deficient in the myelin‐associated glycoprotein (MAG) and the nonreceptor‐type tyrosine kinase Fyn are characterized by a severely hypomyelinated central nervous system (CNS) and morphologically abnormal myelin sheaths. Despite this pronounced phenotype, MAG/Fyn‐deficient mice have a normal longevity. In the present study, we took advantage of the normal life expectancy of this myelin mutant and grafted neural stem cells (NSCs) into the CNS of MAG/Fyn‐deficient mice to study in short‐ and long‐term experiments the fate of NSCs in adult dysmyelinated brains. Neural stem cells were isolated from spinal cords of transgenic mouse embryos ubiquitously expressing enhanced green fluorescent protein. Cells were expanded in vitro in the presence of mitogens for up to 5 weeks before they were grafted into the lateral ventricles or injected into white matter tracts. Analysis of mutant brains 3–15 weeks after intracerebroventricular transplantation of NSCs revealed only limited integration of donor cells into the host brains. However, injection of NSCs directly into white matter tracts resulted in widespread distribution of donor cells within the host tissue. Donor cells survived for at least 15 weeks in adult host brains. The majority of grafted cells populated white matter tracts and differentiated into oligodendrocytes that myelinated host axons. Results suggest that intraparenchymal transplantation of NSCs might be a strategy to reconstruct myelin in dysmyelinated adult brains.
BDNF increases rat brain mitochondrial respiratory coupling at complex I, but not complex II
Authors: Markham A. , Cameron I. , Franklin P. , Spedding M.
Published: September 2004

Brain‐derived neurotrophic factor (BDNF) governs both the selective survival of neurons during development and the experience‐based regulation of synaptic strength throughout life. BDNF produced a concentration‐dependent increase in the respiratory control index (RCI, a measure of the efficiency of respiratory coupling, ATP synthesis and organelle integrity) of rat brain mitochondria. This effect was mediated via a MAP kinase pathway and highly specific for oxidation of glutamate plus malate (complex I) by brain mitochondria. The oxidation by brain mitochondria of the complex II substrate succinate was unaffected by BDNF. The failure of BDNF to modify respiratory activity associated with mitochondrial preparations isolated from rat liver indicates that the actions of the neurotrophin are tissue specific. BDNF also increased the RCI values associated with Ca2+‐induced respiration to a similar extent. This is the first demonstration that BDNF, in addition to modifying neuronal plasticity, can modify brain metabolism and the efficiency of oxygen utilization. The finding that neurotrophins can alter mitochondrial oxidative efficiency has important implications for neurodegenerative and psychiatric diseases.
Directed interactions between visual areas and their role in processing image structure and expectancy
Authors: Salazar Rodrigo F. , König Peter , Kayser Christoph
Published: September 2004

During sensory processing, cortical areas continuously exchange information in different directions along the hierarchy. The functional role of such interactions, however, has been the subject of various proposals. Here, we investigate the role of bottom‐up and top‐down interactions in processing stimulus structure and their relation to expected events. Applying multivariate autoregressive methods to local field potentials recorded in alert cats, we quantify directed interactions between primary (A17/18) and higher (A21) visual areas. A trial‐by‐trial analysis yields the following findings. To assess the role of interareal interactions in processing stimulus structure, we recorded in naïve animals during stimulation with natural movies and pink noise stimuli. The overall interactions decrease compared with baseline for both stimuli. To investigate whether forthcoming events modulate interactions, we recorded in trained animals viewing two stimuli, one of which had been associated with a reward. Several results support such modulations. First, the interactions increase compared with baseline and this increase is not observed in a context where food was not delivered. Second, these stimuli have a differential effect on top‐down and bottom‐up components. This difference is emphasized during the stimulus presentation and is maximal shortly before the possible reward. Furthermore, a spectral decomposition of the interactions shows that this asymmetry is most dominant in the gamma frequency range. Concluding, these results support the notion that interareal interactions are more related to an expectancy state rather than to processing of stimulus structure.
The frontal predominance in human EEG delta activity after sleep loss decreases with age
Authors: Münch Mirjam , Knoblauch Vera , Blatter Katharina , Schröder Carmen , Schnitzler Corina , Kräuchi Kurt , Wirz‐Justice Anna , Cajochen Christian
Published: September 2004

Sleep loss has marked and selective effects on brain wave activity during subsequent recovery sleep. The electroencephalogram (EEG) responds to sleep deprivation with a relative increase in power density in the delta and theta range during non‐rapid eye movement sleep. We investigated age‐related changes of the EEG response to sleep deprivation along the antero‐posterior axis (Fz, Cz, Pz, Oz) under constant routine conditions. Both healthy young (20–31 years) and older (57–74 years) participants manifested a significant relative increase in EEG power density in the delta and theta range after 40 h of sleep deprivation, indicating a sustained capacity of the sleep homeostat to respond to sleep loss in ageing. However, the increase in relative EEG delta activity (1.25–3.75 Hz) following sleep deprivation was significantly more pronounced in frontal than parietal brain regions in the young, whereas such a frontal predominance was diminished in the older volunteers. This age‐related decrease of frontal delta predominance was most distinct at the beginning of the recovery sleep episode. Furthermore, the dissipation of homeostatic sleep pressure during the recovery night, as indexed by EEG delta activity, exhibited a significantly shallower decline in the older group. Activation of sleep regulatory processes in frontal brain areas by an extension of wakefulness from 16 to 40 h appears to be age‐dependent. These findings provide quantitative evidence for the hypothesis that frontal brain regions are particularly vulnerable to the effects of elevated sleep pressure (‘prefrontal tiredness’) and ageing (‘frontal ageing’).
GABAergic phenotypic differentiation of a subpopulation of subventricular derived migrating progenitors
Authors: De Marchis S. , Temoney S. , Erdelyi F. , Bovetti S. , Bovolin P. , Szabo G. , Puche A. C.
Published: September 2004

Olfactory bulb interneurons are continuously generated throughout development and in adulthood. These neurons are born in the subventricular zone (SVZ) and migrate along the rostral migratory stream into the olfactory bulb where they differentiate into local interneurons. To investigate the differentiation of GABAergic interneurons of the olfactory bulb we used a transgenic mouse which expresses green fluorescent protein (GFP) under the control of the glutamic acid decarboxylase 65 kDa (GAD65) promoter. During development and in adulthood GFP was expressed by cells in the SVZ and along the entire length of its rostral extension including the distal portion within the olfactory bulb. The occurrence of GAD65 mRNA in these zones was confirmed by PCR analysis on microdissected regions along the pathway. Polysialic acid neural cell adhesion molecule, a marker of migrating neuroblasts in adults, was coexpressed by the majority of the GFP‐positive SVZ‐derived progenitor cells. Cell tracer injections into the SVZ indicated that ≈ 26% of migrating progenitor cells expressed GFP. These data show the early differentiation of migrating SVZ‐derived progenitors into a GAD65–GFP‐positive phenotype. These cells could represent a restricted lineage giving rise to GAD65‐positive GABAergic olfactory bulb interneurons.
GABAergic neurons participate in the brain's response to birdsong auditory stimulation
Authors: Pinaud Raphael , Velho Tarciso A. F. , Jeong Jin K. , Tremere Liisa A. , Leão Ricardo M. , Von Gersdorff Henrique , Mello Claudio V.
Published: September 2004

Birdsong is a learned vocal behaviour that requires intact hearing for its development in juveniles and for its maintenance during adulthood. However, the functional organization of the brain circuits involved in the perceptual processing of song has remained obscure. Here we provide evidence that GABAergic mechanisms are an important component of these circuits and participate in the auditory processing of birdsong. We first cloned a zebra finch homologue of the gene encoding the 65‐kDa isoform of glutamic acid decarboxylase (zGAD‐65), a specific GABAergic marker, and conducted an expression analysis by in situ hybridization to identify GABAergic cells and to map their distribution throughout auditory telencephalic areas. The results showed that field L2, the caudomedial nidopallium (NCM) and the caudomedial mesopallium (CMM) contain a high number of GABAergic cells. Using patch‐clamp brain slice recordings, we found abundant GABAergic mIPSCs in NCM. Pharmacological antagonism of mIPSCs induced large EPSC bursts, suggesting that tonic inhibition helps to stabilize NCM against runaway excitation via activation of GABA‐A receptors. Next, using double fluorescence in situ hybridization and double immunocytochemical labelling, we demonstrated that large numbers of GABAergic cells in NCM and CMM show inducible expression of the transcriptional regulator ZENK in response to song auditory stimulation. These data provide direct evidence that GABAergic neurons in auditory brain regions are activated by song stimulation. Altogether, our results suggest that GABAergic mechanisms participate in auditory processing and perception, and might contribute to the memorization of birdsong.
Environmental enrichment in mice decreases anxiety, attenuates stress responses and enhances natural killer cell activity
Authors: Benaroya‐Milshtein N. , Hollander N. , Apter A. , Kukulansky T. , Raz N. , Wilf A. , Yaniv I. , Pick C.G.
Published: September 2004

The importance of environment in the regulation of brain, behaviour and physiology has long been recognized in biological, social and medical sciences. Animals maintained under enriched conditions have clearly been shown to have better learning abilities than those maintained under standard conditions. However, the effects of environmental enrichment (EE) on immunity and emotionality have been less documented and remain questionable. Therefore, we investigated the effect of EE on natural killer (NK) cell activity, psychological stress responses and behavioural parameters. Male C3H mice were housed either in enriched or standard conditions for 6 weeks. Behaviour was then examined by the grip‐strength test, staircase and elevated plus maze, and corticosterone levels and NK cell activity were measured. Furthermore, animals exposed to the stress paradigm, achieved by electric shock with reminders, were tested for freezing time in each reminder. Corticosterone levels were also measured. The EE mice showed decreased anxiety‐like behaviour and higher activity compared to standard mice, as revealed by a greater percentage of time spent in the open arms of the elevated plus maze, and a higher rate of climbing the staircase. A shorter freezing time in the stress paradigm and no corticosterone level reactivity were measured in EE mice. In addition, NK cell activity in spleens of EE mice was higher than that demonstrated in those of standard mice. Thus, EE has a beneficial effect on anxiety‐like behaviour, stress response and NK cell activity. The effect on NK cell activity is promising, due to the role of NK cells in host resistance.
Fractalkine (CX3CL1) and fractalkine receptor (CX3CR1) distribution in spinal cord and dorsal root ganglia under basal and neuropathic pain conditions
Authors: Verge Gail M. , Milligan Erin D. , Maier Steve F. , Watkins Linda R. , Naeve Gregory S. , Foster Alan C.
Published: September 2004

Fractalkine is a unique chemokine reported to be constitutively expressed by neurons. Its only receptor, CX3CR1, is expressed by microglia. Little is known about the expression of fractalkine and CX3CR1 in spinal cord. Given that peripheral nerve inflammation and/or injury gives rise to neuropathic pain, and neuropathic pain may be partially mediated by spinal cord glial activation and consequent glial proinflammatory cytokine release, there must be a signal released by affected neurons that triggers the activation of glia. We sought to determine whether there is anatomical evidence implicating spinal fractalkine as such a neuron‐to‐glia signal. We mapped the regional and cellular localization of fractalkine and CX3CR1 in the rat spinal cord and dorsal root ganglion, under basal conditions and following induction of neuropathic pain, employing both an inflammatory (sciatic inflammatory neuropathy; SIN) as well as a traumatic (chronic constriction injury; CCI) model. Fractalkine immunoreactivity and mRNA were observed in neurons, but not glia, in the rat spinal cord and dorsal root ganglia, and levels did not change following either CCI or SIN. By contrast, CX3CR1 was expressed by microglia in the basal state, and the microglial cellular concentration was up‐regulated in a regionally specific manner in response to neuropathy. CX3CR1‐expressing cells were identified as microglia by their cellular morphology and positive OX‐42 and CD4 immunostaining. The cellular distribution of fractalkine and CX3CR1 in the spinal circuit associated with nociceptive transmission supports a potential role in the mechanisms that contribute to the exaggerated pain state in these models of neuropathy.
Functional repair after dorsal root rhizotomy using nerve conduits and neurotrophic molecules
Authors: Tang Xiao‐Qing , Cai Jie , Nelson Kevin D. , Peng Xue‐Jun , Smith George M.
Published: September 2004

Functional recovery after large excision of dorsal roots is absent because of both the limited regeneration capacity of the transected root, and the inability of regenerating sensory fibers to traverse the dorsal root entry zone. In this study, bioresorbable guidance conduits were used to repair 6‐mm dorsal root lesion gaps in rats, while neurotrophin‐encoding adenoviruses were used to elicit regeneration into the spinal cord. Polyester conduits with or without microfilament bundles were implanted between the transected ends of lumbar dorsal roots. Four weeks later, adenoviruses encoding NGF or GFP were injected into the spinal cord along the entry zone of the damaged dorsal roots. Eight weeks after injury, nerve regeneration was observed through both types of implants, but those containing microfilaments supported more robust regeneration of calcitonin gene‐related peptide (CGRP)‐positive nociceptive axons. NGF overexpression induced extensive regeneration of CGRP(+) fibers into the spinal cord from implants showing nerve repair. Animals that received conduits containing microfilaments combined with spinal NGF virus injections showed the greatest recovery in nociceptive function, approaching a normal level by 7–8 weeks. This recovery was reversed by recutting the dorsal root through the centre of the conduit, demonstrating that regeneration through the implant, and not sprouting of intact spinal fibers, restored sensory function. This study demonstrates that a combination of PNS guidance conduits and CNS neurotrophin therapy can promote regeneration and restoration of sensory function after severe dorsal root injury.
CREATING A CONSTITUTIONAL ORDER OF FREEDOM IN EMERGING MARKET ECONOMIES1
Authors: Dorn James A.
Published: September 2004

Economic liberalisation offers the greatest hope for bringing the developing world out of poverty, but to be successful economic liberalisation also requires political and constitutional reform to safeguard private property rights and secure the rule of law. This article examines the process of constitutional reform in a number of developing nations that have recently undergone economic liberalisation, with particular reference to the experience of reform in China.
The genetic control of lignin deposition during plant growth and development
Authors: Rogers Louisa A. , Campbell Malcolm M.
Published: September 2004

Lignins are complex, three‐dimensional polymers embedded in the cell walls of specialised plant cells, where they play important roles in plant growth and development. Plants must possess mechanisms to coordinate lignin deposition so that its synthesis occurs at the appropriate time and place, in response to endogenous and exogenous cues. Here we consider the genetic basis of the control of lignin deposition. We focus on the transcriptional regulation of lignification, considering how the genes encoding the lignin biosynthetic pathway might be co‐ordinately controlled, and the transcription factors that are likely to be involved. We also discuss the mechanisms regulating lignification that have been revealed by mutants with altered lignin deposition. We conclude that, while transcriptional regulation is a common feature in the control of lignification, there are many different regulators that may bring about this common mode of regulation.

Contents

Summary
17

I.
Introduction
17

II.
Transcriptional regulation of genes encoding lignin biosynthetic enzymes
19

III.
Co‐ordinate regulation of genes encoding lignin biosynthetic enzymes
21

IV.
Mutants with altered spatial and temporal control of lignification
23

V.
Conclusion
28

Acknowledgements
28

References
28
Cryopreservation in Populus functional genomics
Authors: Tsai Chung‐Jui , Hubscher Sandra L.
Published: September 2004

The release of the first tree genome sequence for Populus tricocarpa, along with continuing rapid development of Populus EST, microarray and metabolomic technologies, promises to advance forest tree genomics. High throughput transformation by knockout or other gene manipulation strategies to generate large numbers of transgenic Populus for functional elucidation of the estimated 36 000 genes will soon follow. The efficacy of large‐scale transformation approaches for advancing Populus genomics will ultimately depend on the availability of properly maintained transgenic germ lines for distribution. The Arabidopsis community has already demonstrated the value of shared genetic resources, especially mutant and transgenic seed stocks, in functional genomics research. Seed bank will not work for the Populus research community. Instead, a stock distribution center for transgenic Populus research will have to be based on long‐term preservation of clonal germplasm. This review presents recent progress in applying cryogenic techniques for clonal preservation of long‐lived trees and discusses the challenges facing Populus molecular geneticists in germplasm preservation.
Ustilago maydis: how its biology relates to pathogenic development
Authors: Kahmann Regine , Kämper Jörg
Published: September 2004

The smut fungus Ustilago maydis is a ubiquitous pathogen of corn. Although of minor economical importance, U. maydis has become the most attractive model among the plant pathogenic basidiomycetes under study. This fungus undergoes a number of morphological transitions throughout its life‐cycle, the most prominent being the dimorphic switch from budding to filamentous growth that is prerequisite for entry into the biotrophic phase. The morphological transition is controlled by the tetrapolar mating system. Understanding the mating system has allowed connections to signalling cascades operating during pathogenic development. Here, we will review the status and recent insights into understanding pathogenic development of U. maydis and emphasize areas and directions of future research.

Contents

Summary
31

I.
Introduction
31

II.
Important tools for exprimentation with Ustilago myadis
32

III.
Cell fusion requres a complex signalling network
33

IV.
Development of the dikaryon: the bE/bW complex at work
34

V.
A connection between cell cycle, morphogenesis and virulence
36

VI.
The early infection stages
38

VII.
Proliferation and differentiaton in the plant host
38

VIII.
The Ustilago maydis genome
39

IX.
Conclusions
40

Acknowledgements
40

References
40
Revisiting tree maturation and floral initiation in the poplar functional genomics era
Authors: Brunner Amy M. , Nilsson Ove
Published: September 2004

The recent release of the Populus trichocarpa genome sequence will dramatically enhance the efficiency of functional and comparative genomics research in trees. This provides researchers studying various developmental processes related to the perennial and tree life strategies with a completely new set of tools. Intimately associated with the life strategy of trees are their abilities to maintain juvenile or nonflowering phases for years to decades, and once reproductively competent, to alternate between the production of vegetative and reproductive shoots. Most of what we know about the regulation of the floral transition comes from research on Arabidopsis thaliana, a small, herbaceous, rapid‐cycling, annual plant. In this review, we discuss the similarities and differences between Arabidopsis and tree flowering, and how recent findings in Arabidopsis, coupled to comparative and functional genomics in poplars, will help answer the question of how tree maturation and floral initiation is regulated.
Tension wood as a model for functional genomics of wood formation
Authors: Pilate Gilles , Déjardin Annabelle , Laurans Françoise , Leplé Jean‐Charles
Published: September 2004

Wood is a complex and highly variable tissue, the formation of which is developmentally and environmentally regulated. In reaction to gravitropic stimuli, angiosperm trees differentiate tension wood, a wood with specific anatomical, chemical and mechanical features. In poplar the most significant of these features is an additional layer that forms in the secondary wall of tension wood fibres. This layer is mainly constituted of cellulose microfibrils oriented nearly parallel to the fibre axis. Tension wood formation can be induced easily and strongly by bending the stem of a tree. Located at the upper side of the bent stem, tension wood can be compared with the wood located on its lower side. Therefore tension wood represents an excellent model for studying the formation of xylem cell walls. This review summarizes results recently obtained in the field of genomics on tension wood. In addition, we present an example of how the application of functional genomics to tension wood can help decipher the molecular mechanisms responsible for cell wall characteristics such as the orientation of cellulose microfibrils.
Effects of psychotomimetic and antipsychotic agents on neocortical and striatal concentrations of various amino acids in the rat
Authors: Sakurai Shin‐ichiro , Ishii Sumikazu , Umino Asami , Shimazu Dai , Yamamoto Naoki , Nishikawa Toru
Published: September 2004

A subcutaneous injection of small and moderate doses (1.6, 3.2, 4.0 and 4.8 mg/kg) of the schizophrenomimetic methamphetamine caused a dose‐related increase in the tissue content (the net content) of l‐Arg and l‐Asn in the neocortex and striatum at 60 min, but not at 360 min, after injection. The methamphetamine‐induced (4.8 mg/kg) increases in levels of these amino acids were significantly attenuated by pretreatment with an antipsychotic drug, haloperidol (1 mg/kg) or clozapine (10 mg/kg). In the neocortex, a clozapine‐reversible increase in the level of l‐Thr was also observed 60 min after methamphetamine administration. Striatal concentrations of l‐Glu, l‐Ser, l‐Thr, Gly and l‐Ala were augmented by the same regimen in a haloperidol‐ and clozapine‐sensitive fashion. A moderate dose of another schizophrenomimetic phencyclidine (7.5 mg/kg) given subcutaneously induced robust abnormal behavior, a diminution in the neocortical and striatal levels of l‐Asp and an increase in the striatal l‐Ala content without significant effects on the other amino acids studied. These results suggest that neocortical and striatal l‐Arg, l‐Asn, l‐Thr, Gly, l‐Ala or l‐Ser may be implicated in the psychotomimetic effects of methamphetamine and might display mutual interaction with cerebral dopaminergic transmission. The differential effects of methamphetamine and phencyclidine on the net neocortical and striatal concentrations of various amino acids might, at least in part, underlie the distinct features of psychoses induced by these two drugs.
Intermediate‐conductance calcium‐activated potassium channels in enteric neurones of the mouse: pharmacological, molecular and immunochemical evidence for their role in mediating the slow afterhyperpolarization
Authors: Neylon Craig B. , Nurgali Kulmira , Hunne Billie , Robbins Heather L. , Moore Stephen , Chen Mao Xiang , Furness John B.
Published: September 2004

Calcium‐activated potassium channels are critically important in modulating neuronal cell excitability. One member of the family, the intermediate‐conductance potassium (IK) channel, is not thought to play a role in neurones because of its predominant expression in non‐excitable cells such as erythrocytes and lymphocytes, in smooth muscle tissues, and its lack of apparent expression in brain. In the present study, we demonstrate that IK channels are localized on specific neurones in the mouse enteric nervous system where they mediate the slow afterhyperpolarization following an action potential. IK channels were localized by immunohistochemistry on intrinsic primary afferent neurones, identified by their characteristic Dogiel type II morphology. The slow afterhyperpolarization recorded from these cells was abolished by the IK channel blocker clotrimazole. RT–PCR and western analysis of extracts from the colon revealed an IK channel transcript and protein identical to the IK channel expressed in other cell types. These results indicate that IK channels are expressed in neurones where they play an important role in modulating firing properties.
Differential gene expression induced by chronic levodopa treatment in the striatum of rats with lesions of the nigrostriatal system
Authors: Ferrario Juan E. , Taravini Irene R. E. , Mourlevat Sophie , Stefano Andrea , Delfino Marina A. , Raisman‐Vozari Rita , Murer M. Gustavo , Ruberg Merle , Gershanik Oscar
Published: September 2004

Levodopa, the major treatment for patients with Parkinson's disease, has been shown to induce a variety of compensatory effects, including facilitation of sprouting by dopaminergic neurons, in experimental animals with lesions leading to denervation of the striatum. To better understand the cellular and molecular environment where most of these compensatory changes take place, in particular elements that might contribute to the recovery of dopaminergic innervation, we have constructed a differential expression library enriched in transcripts from the striata of rats with lesions of the medial forebrain bundle treated with levodopa for 6 months. We have used this library to screen an expression array of rat genes representing the major cell functions, and have identified several that are involved in neurotrophic mechanisms and plasticity. We have confirmed the differential expression of selected transcripts by non‐radioactive in situ hybridization, and report that the growth factor pleiotrophin, myelin basic protein and calmodulin are overexpressed in the denervated striatum of levodopa‐treated rats.
Conserved residues within the putative active site of γ‐secretase differentially influence enzyme activity and inhibitor binding
Authors: Wrigley Jonathan D. J. , Nunn Emma J. , Nyabi Omar , Clarke Earl E. , Hunt Peter , Nadin Alan , De Strooper Bart , Shearman Mark S. , Beher Dirk
Published: September 2004

γ‐Secretase performs the final processing step in the generation of amyloid‐β (Aβ) peptides, which are believed to be causative for Alzheimer's disease. Presenilins (PS) are required for γ‐secretase activity and the presence of two essential intramembranous aspartates (D257 and D385) has implicated this region as the putative catalytic centre of an aspartyl protease. The presence of several key hydrogen‐bonding residues around the active site of classical aspartyl proteases led us to investigate the role of both the critical aspartates and two nearby conserved hydrogen bond donors in PS1. Generation of cell lines stably overexpressing the D257E, D385E, Y256F and Y389F engineered mutations has enabled us to determine their role in enzyme catalysis and binding of a transition state analogue γ‐secretase inhibitor. Here we report that replacement of either tyrosine residue alters γ‐secretase cleavage specificity, resulting in an increase in the production of the more pathogenic Aβ(42) peptide in both cells and membranous enzyme preparations, without affecting inhibitor binding. In contrast, replacement of either of the aspartate residues precludes inhibitor binding in addition to inactivation of the enzyme. Together, these data further incriminate the region around the intramembranous aspartates as the active site of the enzyme, targeted by transition state analogue inhibitors, and highlight the roles of individual residues.
Cerebral creatine kinase deficiency influences metabolite levels and morphology in the mouse brain: a quantitative in vivo1H and 31P magnetic resonance study
Authors: In‘t Zandt H. J. A. , Renema W. K. J. , Streijger F. , Jost C. , Klomp D. W. J. , Oerlemans F. , Van der Zee C. E. E. M. , Wieringa B. , Heerschap A.
Published: September 2004

Creatine kinase (CK)‐catalysed ATP–phosphocreatine (PCr) exchange is considered to play a key role in energy homeostasis of the brain. This study assessed the metabolic and anatomical consequences of partial or complete depletion of this system in transgenic mice without cytosolic B‐CK (B‐CK–/–), mitochondrial ubiquitous CK (UbCKmit–/–), or both isoenzymes (CK –/–), using non‐invasive quantitative magnetic resonance (MR) imaging and spectroscopy. MR imaging revealed an increase in ventricle size in a subset of B‐CK–/– mice, but not in animals with UbCKmit or compound CK mutations. Mice lacking single CK isoenzymes had normal levels of high‐energy metabolites and tissue pH. In the brains of CK double knockouts pH and ATP and Pi levels were also normal, even though PCr had become completely undetectable. Moreover, a 20–30% decrease was observed in the level of total creatine and a similar increase in the level of neuronal N‐acetyl‐aspartate compounds. Although CKs themselves are not evenly distributed throughout the CNS, these alterations were uniform and concordant across different brain regions. Changes in myo‐inositol and glutamate peaks did appear to be mutation type and brain area specific. Our results challenge current models for the biological significance of the PCr–CK energy system and suggest a multifaceted role for creatine in the brain.
Cloning and expression of the mouse histamine H3 receptor: evidence for multiple isoforms
Authors: Rouleau Agnès , Héron Anne , Cochois Véronique , Pillot Catherine , Schwartz Jean‐Charles , Arrang Jean‐Michel
Published: September 2004

The existence of mouse H3‐receptor isoforms was investigated by PCR analysis and cDNA cloning. Splicing mechanisms previously reported in various species are conserved in the mouse. The retention/deletion of a fragment in the third intracellular loop of the mouse receptor leads to the existence of three isoforms designated mH3(445), mH3(413) and mH3(397) according to the length of their deduced amino acid sequence. PCR analysis showed that mouse H3‐receptor isoforms display different expression patterns in the brain. Following expression in Cos‐1 cells, [125I]iodoproxyfan binding indicated similar pharmacological profiles of the mH3(445), mH3(413) and mH3(397) isoforms. The pharmacological profile of the mouse H3 receptor is more similar to the rat receptor than to the human receptor, although some differences were also observed between the mouse and rat receptors. For example, the potency of thioperamide and ciproxifan is slightly higher at the mouse receptor than at the rat receptor but 40–100‐fold higher than at the human receptor. In situ hybridization histochemistry showed that the distribution of H3‐receptor mRNAs in the mouse brain is rather similar to that previously reported in the rat brain. However, the autoradiographic and cellular expression patterns observed in several brain areas such as the thalamus or hippocampus reveal important differences between the two species.
Mechanism of promoter activity of the β‐amyloid precursor protein gene in different cell lines: identification of a specific 30 bp fragment in the proximal promoter region
Authors: Ge Yuan‐Wen , Ghosh Chandramallika , Song Weihong , Maloney Bryan , Lahiri Debomoy K.
Published: September 2004

The amyloid β‐protein (Aβ) deposited in brains of Alzheimer's disease (AD) patients is proteolytically derived from a large Aβ precursor protein (APP). APP gene expression patterns in the AD brain region indicate that abnormalities of gene regulation may be important in AD pathology. To understand the contribution of different cell types to APP gene expression, we studied it at four levels: promoter activity (by reporter gene assay of transfected cells), DNA–nuclear protein interaction (by electrophoretic mobility shift assay), RNA message and protein (by northern and western blotting, respectively). APP mRNA and protein expression levels were greater in neuroblastoma and PC12 cells than in glial or cervix epithelial cells. Relative activity among 12 different promoter regions and within single regions varied according to cell type/cell line. An upstream regulatory region containing a GATA‐1 site is necessary for activity in PC12 and glial cells but not in neuroblastoma cells. DNA–protein interactions were examined in three distal and one proximal promoter elements in nuclear extracts belonging to neuronal and non‐neuronal cells. The proximal promoter region is important for cell line‐specific APP gene expression. Characterization of the APP regulatory region's interaction with cell type‐specific nuclear factor(s) is important to understand tissue‐specific expression of APP seen in AD subjects.