bluuebunny/crossref_metadata_2025 huggingface dataset:
Intracellular calcium release resulting from mGluR1 receptor activation modulates GABAA currents in wide‐field retinal amacrine cells: a study with caffeine
Authors: Vigh Jozsef , Lasater Eric M.
Published: June 2003

The modulatory action of calcium (Ca2+) released from intracellular stores on GABAA receptor‐mediated current was investigated in wide‐field amacrine cells isolated from the teleost, Morone chrysops, retina. Caffeine, ryanodine or inositol 1,4,5‐triphosphate (IP3) markedly inhibited the GABAA current by elevating [Ca2+]i. The inhibition resulted from the activation of a Ca2+→ Ca2+/calmodulin → calcineurin cascade. Long (>12 s) exposure to glutamate mimicked the caffeine effect, i.e. it inhibited the GABAA current by elevating [Ca2+]i through mGluR1 receptor activation and consequent IP3 generation. This pathway provides a ‘timed’ disinhibitory mechanism to potentiate excitatory postsynaptic potentials in wide‐field amacrine cells. It occurs as a result of the suppression of GABA‐mediated conductances as a function of the duration of presynaptic excitatory input activity. This is much like some forms of long‐term potentiation in the central nervous system. In a local retinal circuit this will selectively accentuate particular excitatory inputs to the wide‐field amacrine cell. Similar to other neural systems, we suggest that activity‐dependent postsynaptic disinhibition is an important feature of the signal processing in the inner retina.
Arm movement and gap as factors influencing the reaction time of the second saccade in a double‐step task
Authors: Lünenburger Lars , Hoffmann Klaus‐Peter
Published: June 2003

To guide our hand for reaching, we explore our visual environment by sequences of saccades. In the present paper, we studied the eye and hand movements of human subjects looking or looking and pointing at a target that is instantaneously displaced two times (double‐step task). It was previously shown that the second saccade has a much longer reaction time than the first one [Feinstein & Williams (1972) Vision Res., 12, 33–44]. The second reaction time is even longer if the subject also has to point to the target with the hand [Lünenburger et al. (2000) Eur. J. Neurosci., 12, 4107–4116]. The conditions and objective for these effects are further examined in the present paper. It is shown that vision of the hand reduces the first and second saccadic reaction times in parallel. The second reaction time is prolonged for shorter delays between both target steps as well as for larger amplitudes of the second saccade. However, the long second reaction time does not reflect an absolute saccadic refractory period, because a gap before the second target step reduces the second reaction time to a value similar to the first. Hand response time and average hand velocity were increased when the second target step was larger. The response time for the eyes was about 30% of the response time of the hand. We argue that the observed effects reflect the coordination of eye and hand movement to allow a precise and efficient reaching behaviour.
Piriform cortex functional heterogeneity revealed by cellular responses to odours
Authors: Litaudon P. , Amat C. , Bertrand B. , Vigouroux M. , Buonviso N.
Published: June 2003

The role of the piriform cortex (PC) in olfactory information processing remains mainly unknown. Indeed, until recently, only a few studies have investigated the response of PC neurons to odours and these studies did not take into account the functional heterogeneity of the PC previously described using an electrical stimulation paradigm. In this experiment, extracellular activity in response to odour was recorded in urethane anaesthetized rats in the different parts of the cortex ranging from anterior to posterior. A large percentage of cortical cells were silent at rest, and this percentage increased from anterior to posterior. Analysis of odour evoked activity revealed a large percentage of nonresponsive cells that increased from anterior to posterior. Cell activity was largely synchronized with breathing and different temporal patterns were observed. The anterior PC was characterized by odour‐evoked responses phase‐locked with the inhalation‐exhalation transition period. By contrast, activity in the posterior PC was mainly phase‐locked with inhalation or exhalation. These data confirm the spatial functional heterogeneity previously reported in the PC. Functional anatomy of the PC suggests that activity in the anterior PC can be mainly driven by afferent activity coming from the OB whereas posterior cells were certainly entrained by more complex mechanisms.
Purinergic receptors on microglial cells: functional expression in acute brain slices and modulation of microglial activation in vitro
Authors: Boucsein Clemens , Zacharias Robert , Färber Katrin , Pavlovic Sanja , Hanisch Uwe‐Karsten , Kettenmann Helmut
Published: June 2003

Microglial cells are the pathologic sensors in the brain. ATP released from damaged cells is a candidate for signalling neural injury to microglia. Moreover, ATP is an extracellular messenger for propagating astrocyte activity in the form of Ca2+ waves. To test for the functional expression of purinoreceptors in microglial cells we employed the patch‐clamp technique in acute slices of adult mouse brain. ATP triggered a nonselective cationic and a K+ current. Pharmacological screening with purinergic ligands indicated the presence of P2Y1 and P2Y2/4 receptors linked to the activation of a K+ current and P2X receptors, including P2X7, linked to the activation of a nonselective cationic current. These findings suggest that microglial cells in situ express different purinergic receptors with distinct sensitivity and functional coupling. To test for the involvement of purinoreceptors in microglial activation, we stimulated cultured microglial cells with lipopolysaccharide and measured the release of tumour necrosis factor α, interleukin‐6, interleukin‐12 and macrophage inflammatory protein 1α, induction of K+ outward currents and nitric oxide release. All these parameters were reduced in the presence of purinergic ligands, indicating that purinergic receptor activation attenuated indicators of microglial activation.
Axonal morphogenesis controlled by antagonistic roles of two CRMP subtypes in microtubule organization
Authors: Yuasa‐Kawada Junichi , Suzuki Ryoko , Kano Fumi , Ohkawara Takeshi , Murata Masayuki , Noda Masaharu
Published: June 2003

During development, cells undergo dynamic morphological changes by rearrangements of the cytoskeleton including microtubules. However, molecular mechanisms underlying the microtubule remodeling between orientated and disoriented formations are almost unknown. Here we found that novel subtypes of collapsin response mediator proteins (CRMP‐As) and the originals (CRMP‐Bs), which occur from the alternative usage of different first coding exons, are involved in this conversion of microtubule patterns. Overexpression of CRMP2A and CRMP2B in chick embryonic fibroblasts induced orientated and disoriented patterns of microtubules, respectively. Moreover, sequential overexpression of another subtype overcame the effect of the former expression of the countersubtype. Overexpression experiments in cultured chick retinae showed that CRMP2B promoted axon branching and suppressed axon elongation of ganglion cells, while CRMP2A blocked these effects when co‐overexpressed. Our findings suggest that the opposing activities of CRMP2A and CRMP2B contribute to the cellular morphogenesis including neuronal axonogenesis through remodeling of microtubule organization.
Expression patterns and subcellular localization of the Down syndrome candidate protein MNB/DYRK1A suggest a role in late neuronal differentiation
Authors: Hämmerle B. , Carnicero A. , Elizalde C. , Ceron J. , Martínez S. , Tejedor F. J.
Published: June 2003

The Minibrain (Mnb) gene belongs to a new protein kinase family, which is evolutionarily conserved, and probably plays several roles during brain development and in adulthood. In Drosophila, mnb is involved in postembryonic neurogenesis and in learning/memory. In humans, MNB has been mapped within the Down syndrome critical region of chromosome 21 and is overexpressed in the Down syndrome embryonic brain. It has been widely proposed that MNB is involved in the neurobiological alterations associated with Down syndrome. Nevertheless, little is known about the functional role that MNB plays in vertebrate brain development. We have recently shown [Hämmerle et al. (2002) Dev. Biol., 246, 259–273] that in early vertebrate embryos, Mnb is transiently expressed in neural progenitor cells during the transition from proliferating to neurogenic divisions. Here we have studied in detail a second wave of Mnb expression, which takes place in the brain of intermediate and late vertebrate embryos. In these stages, MNB seems to be restricted to certain populations of neurons, as no consistent expression was detected in astroglial or oligodendroglial cells. Interestingly, MNB expression takes place at the time of dendritic tree differentiation and is initiated by a transient translocation from the cytoplasm to the nucleus. Afterwards, MNB protein is transported to the growing dendritic tree, where it colocalizes with Dynamin 1, a putative substrate of MNB kinases. We propose that MNB kinase is involved in the signalling mechanisms that regulate dendrite differentiation. This functional role helps to build a new hypothesis for the implication of MNB/DYRK1A in the developmental aetiology of Down syndrome neuropathologies.
Decreased ethanol preference and wheel running in Nurr1‐deficient mice
Authors: Werme Martin , Hermanson Elisabet , Carmine Andrea , Buervenich Silvia , Zetterström Rolf H. , Thorén Peter , Ögren Sven Ove , Olson Lars , Perlmann Thomas , Brené Stefan
Published: June 2003

Nurr1 (Nr4a2) is a transcription factor expressed in dopamine cells from early development and throughout life. Null mutants for Nurr1 lack the ventral midbrain dopamine neurons and die soon after birth. Animals with a heterozygous deletion are viable and display no apparent abnormality. We have investigated the impact of heterozygous deletion of Nurr1 on ethanol consumption in adult mice as a model for drug‐induced reward and on wheel running as a model for natural reward. Interestingly, Nurr1 heterozygous mice never developed high ethanol consumption nor did they develop as much running behaviour as did the wild‐type animals. Thus, Nurr1 appears to have a key role for the reinforcing properties of ethanol and running that underlies the development of excessive reward‐seeking behaviours characteristic for addiction. Quantitative trait loci mapping using C57Bl/6 and DBA/2 mice describe a locus for ethanol preference on chromosome 2, wherein Nurr1 is located. We found two dinucleotide repeats in the Nurr1 promoter that were longer in mice with low preference for ethanol (DBA/2 and 129/Sv) than in mice with high preference for ethanol (C57Bl/6J and C57Bl/6NIH). These sequential data are compatible with Nurr1 as a candidate gene responsible for the quantitative trait loci for ethanol preference on mouse chromosome 2. Together, our data thus imply involvement of Nurr1 in the transition to a state of high ethanol consumption as well as in the development of a high amount of wheel running in mice.
Early life adversity programs changes in central 5‐HT neuronal function in adulthood
Authors: Gartside Sarah E. , Johnson Daniel A. , Leitch Melville M. , Troakes Claire , Ingram Colin D.
Published: June 2003

Early life adversity is associated with an increased incidence of psychiatric illness in adulthood. Although the mechanisms underlying this association are unclear, one possible substrate is brain 5‐hydroxytryptamine neurotransmission, which is reportedly abnormal in several psychiatric disorders. This study examined the effect of a rat model of early life adversity, early maternal separation, on 5‐hydroxytryptamine neurotransmission in adulthood. In vitro electrophysiological experiments revealed that, in early maternal separation rats compared with controls, the sensitivity of α1‐adrenoceptors on 5‐hydroxytryptamine neurons in the dorsal raphe nucleus was significantly reduced, whilst the sensitivity of 5‐hydroxytryptamine1A receptors showed a nonsignificant trend to reduction. In in vivo microdialysis experiments, the 5‐hydroxytryptamine1A receptor agonist‐induced suppression of 5‐hydroxytryptamine release in the frontal cortex was reduced in early maternal separation animals, suggesting desensitization of 5‐hydroxytryptamine1A autoreceptors. There was no increase in basal 5‐hydroxytryptamine in the frontal cortex as measured by microdialysis and a nonsignificant trend towards increased basal firing activity of classical (non‐bursting) 5‐hydroxytryptamine neurons in the dorsal raphe nucleus measured by in vivo electrophysiology. Finally, early maternal separation failed to alter expression of messenger ribonucleic acids coding for 5‐hydroxytryptamine1A or α1B receptors in the dorsal raphe nucleus as measured by in situ hybridization histochemistry, suggesting that functional changes in receptor sensitivity observed are not due to changes in receptor gene transcription. The findings demonstrate that early life adversity programs changes in sensitivity of the two principal regulators of 5‐hydroxytryptamine neuronal activity. Similar effects in humans may contribute to the increased incidence of psychiatric illness in individuals exposed to early life adversity.
What you believe versus what you think they believe: a neuroimaging study of conceptual perspective‐taking
Authors: Ruby Perrine , Decety Jean
Published: June 2003

Social communication requires shared representations as well as a cognitive flexibility for successful interactions between self and other. What neural mechanisms underlie the ability to distinguish between our own perspective vs. the perspective of others at a conceptual level? In this PET study subjects who were medical students were asked according to the experimental conditions to respond to a list of health‐related questions, taking either their own perspective or the perspective of a ‘lay person’. Third‐person perspective as compared to first‐person perspective was associated with activation in the medial part of the superior frontal gyrus, in the left superior temporal sulcus, in the left temporal pole and in the right inferior parietal lobe. The reverse comparison revealed a specific activation in the postcentral gyrus for the first‐person conceptual perspective. This study provides congruent results at the conceptual level with previous studies investigating the neural correlates of self/other distinction at the motor level, and opens a new area of research in which conceptual cognition can be viewed in the continuity of motor cognition.
Rapid reversal of stress induced loss of synapses in CA3 of rat hippocampus following water maze training
Authors: Sandi Carmen , Davies Heather A. , Cordero M. Isabel , Rodriguez Jose J. , Popov Victor I. , Stewart Michael G.
Published: June 2003

The impact was examined of exposing rats to two life experiences of a very different nature (stress and learning) on synaptic structures in hippocampal area CA3. Rats were subjected to either (i) chronic restraint stress for 21 days, and/or (ii) spatial training in a Morris water maze. At the behavioural level, restraint stress induced an impairment of acquisition of the spatial response. Moreover, restraint stress and water maze training had contrasting impacts on CA3 synaptic morphometry. Chronic stress induced a loss of simple asymmetric synapses [those with an unperforated postsynaptic density (PSD)], whilst water maze learning reversed this effect, promoting a rapid recovery of stress‐induced synaptic loss within 2–3 days following stress. In addition, in unstressed animals a correlation was found between learning efficiency and the density of synapses with an unperforated PSD: the better the performance in the water maze, the lower the synaptic density. Water maze training increased the number of perforated synapses (those with a segmented PSD) in CA3, both in stressed and, more notably, in unstressed rats. The distinct effects of stress and learning on CA3 synapses reported here provide a neuroanatomical basis for the reported divergent effects of these experiences on hippocampal synaptic activity, i.e. stress as a suppressor and learning as a promoter of synaptic plasticity.
Normal sensitivity to acute pain, but increased inflammatory hyperalgesia in mice lacking the nociceptin precursor polypeptide or the nociceptin receptor
Authors: Depner Ulrike B. , Reinscheid Rainer K. , Takeshima Hiroshi , Brune Kay , Zeilhofer Hanns Ulrich
Published: June 2003

Nociceptin/orphanin FQ (N/OFQ) is the endogenous agonist of the N/OFQ peptide receptor (NOP receptor). It is released from a larger precursor polypeptide, called prepro‐nociceptin (ppN/OFQ) from which, in addition to N/OFQ, other biologically active neuropeptides may be derived. Increasing evidence indicates that exogenous application of N/OFQ to the central nervous system of mice and rats induces pro‐ and antinociceptive effects depending on the dose and site of administration. Much less is known about a potential contribution of endogenous N/OFQ to pain control. Here, we have used a genetic approach to address this topic. Mice deficient in either the NOP receptor (NOP‐R−/− mice) or the N/OFQ precursor polypeptide (ppN/OFQ−/− mice) or both (double knockout mice) were compared with wild‐type littermates in animal models of acute and tonic pain. Nociceptive responses to acute noxious heat of all three types of mutant mice were indistinguishable from those of wild‐type mice. Accordingly, nociceptive behaviour was very similar in the early phase of the formalin test. However, NOP‐R−/−, ppN/OFQ−/− and double knockout mice showed markedly stronger nociceptive responses during prolonged nociceptive stimulation in the second phase of the formalin test and significantly lower thermal pain thresholds in inflamed tissue after zymosan A injection. These results indicate that N/OFQ contributes significantly to endogenous pain control during prolonged nociceptive stimulation but does not affect acute pain sensitivity. Among the three types of mutant mice nociceptive behaviour was nearly identical, indicating that the lack of other potential ppN/OFQ products in the ppN/OFQ−/− mice was apparently without effect on the nociceptive phenotype.
Morphine withdrawal precipitated by specific mu, delta or kappa opioid receptor antagonists: a c‐Fos protein study in the rat central nervous system
Authors: Le Guen Stéphanie , Gestreau Christian , Besson Jean‐Marie
Published: June 2003

We have recently shown concurrent changes in behavioural responses and c‐Fos protein expression in the central nervous system in both naive and morphine‐dependent rats after systemic administration of the opioid antagonist naloxone. However, because naloxone acts on the three major types of opioid receptors, the present study aimed at determining, in the same animals, both changes in behaviour and c‐Fos‐like immunoreactivity after intravenous injection of selective opioid antagonists, such as mu (β‐funaltrexamine, 10 mg/kg), delta (naltrindole, 4 mg/kg) or kappa (nor‐binaltorphimine, 5 mg/kg) opioid receptor antagonists, in naive or morphine‐dependent rats. In a first experimental series, only β‐funaltrexamine increased c‐Fos expression in the eight central nervous system structures examined, whereas no effect was seen after naltrindole or nor‐binaltorphimine administration in naive rats. These results suggest a tonic activity in the endogenous opioid peptides acting on mu opioid receptors in normal rats. A second experimental series in morphine‐dependent rats showed that β‐funaltrexamine had the highest potency in the induction of classical signs of morphine withdrawal syndrome, as well as the increase in c‐Fos expression in the 22 central nervous system structures studied, suggesting a major role of mu opioid receptors in opioid dependence. However, our results also demonstrated that naltrindole and, to a lesser extent, nor‐binaltorphimine were able to induce moderate signs of morphine withdrawal and relatively weak c‐Fos protein expression in restricted central nervous system structures. Therefore, delta and kappa opioid receptors may also contribute slightly to opioid dependence.
Illusory contours and specific regions of human extrastriate cortex: evidence from rTMS
Authors: Brighina F. , Ricci R. , Piazza A. , Scalia S. , Giglia G. , Fierro B.
Published: June 2003

Functional magnetic resonance imaging studies showed that perception of illusory contours is associated with extrastriate cortex activation prevailing on the right side. 1 Hz repetitive transcranial magnetic stimulation (rTMS) is able to induce lasting inhibition of cortical activity. The objective of the study was to investigate the role of extrastriate cortex in illusory contour perception inducing 1 Hz rTMS interference in healthy subjects. Eight healthy subjects underwent 1 Hz rTMS (600 pulses) through a figure‐of‐eight coil over right and left occipital cortex (O1 and O2 of 10/20 EEG system); sham magnetic stimulation on the same sites and right motor cortex rTMS (in three subjects) were given as control. Subjects performed a computerized task requiring perception of illusory and real contours of Kanizsa squares in baseline and after rTMS. After stimulus presentation the subject made a forced‐choice decision about the regularity or irregularity of stimulus contour, by hitting as fast as possible one of two keys on the computer keyboard. Reaction times (RT) were measured. Right occipital stimulation significantly increased RT for illusory contour perception (vs. baseline, P < 0.05). No significant RT changes were observed in the other experimental conditions with respect to the baseline condition. It is concluded that 1Hz rTMS of right extrastriate cortex can disrupt perception of illusory contours and the effect appears to be side‐specific, being evident only after right occipital stimulation. This study supports the critical role of right extrastriate cortex in illusory contour perception.
Cloning and characterization of an ionotropic glutamate receptor subunit expressed in the squid nervous system
Authors: Battaglia A. A. , Nardi G. , Steinhardt A. , Novakovic A. , Gentile S. , Iaccarino Idelson P. , Gilly W. F. , Santis A. De
Published: June 2003

In this paper we describe the cloning of a putative ionotropic glutamate receptor subunit, SqGluR, and its distribution in the nervous system of the squid. A full‐length cDNA was assembled from a cDNA library of the stellate ganglion/giant fibre lobe complex of Loligo opalescens. The deduced amino acid sequence of the mature SqGluR displayed 44–46% amino acid identity with mammalian GluR1–GluR4 and 53% with Lym‐eGluR1 from Lymnaea stagnalis. In situ hybridizations in adult squid confirmed that the SqGluR mRNA is abundant in giant fibre lobe neurons, in large, presumptive motor neurons of the stellate ganglion proper and in the supraoesophageal and optic lobes of the central nervous system. In newborn squid, SqGluR mRNA expression was detected throughout the nervous system but not elsewhere. A synthetic peptide corresponding to the last 15 amino acids of the SqGluR C‐terminus was used to generate polyclonal antibodies, which were used for immunoblot analysis to demonstrate widespread expression in the squid central and peripheral nervous systems. Injection of the synthetic peptide into the postsynaptic side of the giant synapse inhibited synaptic transmission.
Expression of oncostatin M receptor β in a specific subset of nociceptive sensory neurons
Authors: Tamura Shinobu , Morikawa Yoshihiro , Miyajima Atsushi , Senba Emiko
Published: June 2003

Oncostatin M belongs to the interleukin‐6 family of cytokines and acts as a multifunctional cytokine during murine embryogenesis and in inflammatory reactions. Although it has been demonstrated that oncostatin M has biological activities on many types of cells, including hepatocytes, dermal fibroblasts and endothelial cells, the roles of oncostatin M in the murine peripheral nervous system remain unclear. Here, we investigated the expression of specific β‐subunit of oncostatin M receptor in the dorsal root ganglia of adult mice. In the adult dorsal root ganglia, β‐subunit of oncostatin M receptor was exclusively expressed in small‐sized neurons. Approximately 13% of total dorsal root ganglia neurons in mice contained β‐subunit of oncostatin M receptor. The double‐immunofluorescence method revealed that approximately 28% of β‐subunit of oncostatin M receptor‐positive neurons contained TrkA immunoreactivity, 63% expressed Ret immunoreactivity and 58% bound isolectin B4. No neuropeptides, including substance P and calcitonin gene‐related peptide, were contained in the neurons. In addition, all β‐subunit of oncostatin M receptor‐positive neurons expressed both vanilloid receptor 1 and P2X3 purinergic receptor. These neurons projected to the inner portion of lamina II in the dorsal horn of spinal cord and the dermis of skin. Seven days after sciatic nerve axotomy, the expression of β‐subunit of oncostatin M receptor was down‐regulated in the lumbar dorsal root ganglia of the injured side. Our study demonstrated that β‐subunit of oncostatin M receptor was expressed in both cell bodies and processes of nonpeptidergic nociceptive neurons in adult mice, suggesting that oncostatin M may affect the nociceptive function of the neurons through the modulation of vanilloid receptor 1 and P2X3 expression.
Metabolic changes after repetitive transcranial magnetic stimulation (rTMS) of the left prefrontal cortex: a sham‐controlled proton magnetic resonance spectroscopy (1H MRS) study of healthy brain
Authors: Michael Nikolaus , Gösling Michael , Reutemann Michael , Kersting Annette , Heindel Walter , Arolt Volker , Pfleiderer Bettina
Published: June 2003

Rapid transcranial magnetic stimulation is being increasingly used in the treatment of psychiatric disorders, especially major depression. However, its mechanisms of action are still unclear. The aim of this study was to assess metabolic changes by proton magnetic resonance spectroscopy following high‐frequency rapid transcranial magnetic stimulation (20 Hz), both immediately after a single session and 24 h after a series of five consecutive sessions. Twelve healthy volunteers were enrolled in a prospective single‐blind, randomized study [sham (n = 5) vs. real (n = 7)]. Three brain regions were investigated (right, left dorsolateral prefrontal cortex, left anterior cingulate cortex). A single as well as a series of consecutive rapid transcranial magnetic stimulations affected cortical glutamate/glutamine levels. These effects were present not only close to the stimulation site (left dorsolateral prefrontal cortex), but also in remote (right dorsolateral prefrontal cortex, left cingulate cortex) brain regions. Remarkably, the observed changes in glutamate/glutamine levels were dependent on the pre‐transcranial magnetic stimulation glutamate/glutamine concentration, i.e. the lower the pre‐stimulation glutamate/glutamine level, the higher the glutamate/glutamine increase observed after short‐ or long‐term stimulation (5 days). In general, the treatment was well tolerated and no serious side‐effects were reported. Neither transient mood changes nor significant differences in the outcome of a series of neuropsychological test batteries after real or sham transcranial magnetic stimulation occurred in our experiment. In summary, these data indicate that rapid transcranial magnetic stimulation may act via stimulation of glutamatergic prefrontal neurons.
Tremor‐related activity of neurons in the ‘motor’ thalamus: changes in firing rate and pattern in the MPTP vervet model of parkinsonism
Authors: Guehl D. , Pessiglione M. , François C. , Yelnik J. , Hirsch E. C. , Féger J. , Tremblay L.
Published: June 2003

The pathophysiology of parkinsonian tremor remains a matter of debate with two opposing hypotheses proposing a peripheral and a central origin, respectively. A central origin of tremor could arise either from a rhythmic activity of the internal segment of the globus pallidus (GPi) or from a structure such as the thalamus, outside the basal ganglia. In this study, single‐unit recordings were performed in three 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐treated monkeys within the GPi and within three territories of the motor thalamus (delimited by their afferent inputs from the GPi, the substantia nigra and the cerebellum, respectively). For each recorded neuron, we compared the variations in firing rate and pattern in tremor and no tremor periods. Tremor either occurred spontaneously or was induced by external stimulation. When the animals entered into a tremor period we observed: (i) an increase in the mean firing rate in about half of the recorded neurons of the motor thalamus; and (ii), a change from an irregular to a rhythmic discharge within the range of tremor frequency (5–7 Hz) in about 10% of the recorded neurons of the motor thalamus (pallidal and cerebellar territories) and the GPi. Most of the thalamic neurons that exhibited a rhythmic discharge during tremor were found to be sensitive to external stimulation. Because the changes in firing rate occurred predominantly in the motor thalamus and not in the GPi, and because a fast rhythmic discharge of 10–15 Hz was frequently observed in the GPi and not in the motor thalamus, we conclude that thalamic activity is not a simple reproduction of basal ganglia output. Moreover, we suggest that thalamic processing of basal ganglia outputs could participate in the genesis of tremor, and that this thalamic processing could be influenced by sensory inputs and/or changes in attentional level elicited by external stimulation.
Perturbation of CD44 function affects chiasmatic routing of retinal axons in brain slice preparations of the mouse retinofugal pathway
Authors: Lin Ling , Chan Sun‐On
Published: June 2003

Neurons generated early in development of the ventral diencephalon have been shown to play a key role in defining the midline and the caudal boundary of the optic chiasm in the mouse retinofugal pathway. These functions have been attributed to a surface bound adhesion molecule, CD44 that is expressed in these chiasmatic neurons. In this study, we investigated the effects of perturbing normal CD44 functions on axon routing in brain slice preparations of the mouse retinofugal pathway. Two CD44 antibodies (Hermes‐1 and IM7) were used that bind to distinct epitopes on the extracellular domain of the molecule. We found that both antibodies produced dramatic defects in routing of the retinal axons that arrive early in the chiasm. In preparations of embryonic day 13 (E13) and E14 pathways, the crossed component in the chiasm was significantly reduced after antibody treatment. However, such reduction in axon crossing was not observed in E15 chiasm, indicating that the lately generated crossed axons lost their responses to CD44. Furthermore, the anti‐CD44 treatment produced a reduction in the uncrossed component in the E15 but not in younger pathways, suggesting a selective response of the lately generated axons, mostly from ventral temporal retina, but not those generated earlier, to the CD44 at the chiasmatic midline in order to make their turn for the uncrossed pathway. These findings provide evidence that a normal function of CD44 molecules in the chiasmatic neurons is essential for axon crossing and axon divergence at the mouse optic chiasm.
GAP‐43 mRNA and protein expression in the hippocampal and parahippocampal region during the course of epileptogenesis in rats
Authors: Tolner Else A. , Van Vliet Erwin A. , Holtmaat Anthony J. G. D. , Aronica Eleonora , Witter Menno P. , Da Silva Fernando H. Lopes , Gorter Jan A.
Published: June 2003

In order to reveal axonal rewiring in the hippocampal and parahippocampal regions after status epilepticus, we investigated the temporal evolution of growth‐associated protein‐43 (GAP‐43) mRNA and protein expression in two rat models of mesial temporal lobe epilepsy (MTLE). Status epilepticus (SE) was induced by electrical stimulation of the angular bundle or by intraperitoneal kainic acid (KA) injections. Despite increased GAP‐43 mRNA expression in dentate granule cells at 24 h after SE, GAP‐43 protein expression in the inner molecular layer (IML) of the dentate gyrus decreased progressively after 24 h after SE in both models. Nevertheless robust mossy fiber sprouting (MFS) was evident in the IML of chronic epileptic rats. Remaining GAP‐43 protein expression in the IML in chronic epileptic rats did not correlate with the extent of MFS, but with the number of surviving hilar neurons. In the parahippocampal region, GAP‐43 mRNA expression was decreased in layer III of the medial entorhinal area (MEAIII) in parallel with extensive neuronal loss in this layer. There was a tendency of GAP‐43 mRNA up‐regulation in the presubiculum, a region that projects to MEAIII. With regard to this parahippocampal region, however, changes in GAP‐43 mRNA expression were not followed by protein changes. The presence of the presynaptic protein GAP‐43 in a neurodegenerated MEAIII indicates that fibers still project to this layer. Whether reorganization of fibers has occurred in this region after SE needs to be investigated with tools other than GAP‐43.
Role of heme oxygenase‐1 protein in the neuroprotective effects of cyclopentenone prostaglandin derivatives under oxidative stress
Authors: Satoh Takumi , Baba Megumi , Nakatsuka Daisaku , Ishikawa Yasuyuki , Aburatani Hiroyuki , Furuta Kyoji , Ishikawa Toshihisa , Hatanaka Hiroshi , Suzuki Masaaki , Watanabe Yasuyoshi
Published: June 2003

Previously we found that some cyclopenteone prostaglandin derivatives (PGs), referred to as neurite outgrowth‐promoting PGs (NEPPs), have dual biological activities of promoting neurite outgrowth and preventing neuronal death [Satoh et al. (2000) J. Neurochem., 75, 1092‐1102; Satoh et al. (2001) J. Neurochem., 77, 50‐62; Satoh et al. (2002) In Kikuchi, II. (ed.), Strategenic Medical Science Against Brain Attack. Springer‐Verlag, Tokyo, pp. 78‐93]. To investigate possible cellular mechanisms of the neuroprotective effects, we performed oligo hybridization‐based DNA array analysis with mRNA isolated from HT22, a cell line that originated from a mouse hippocampal neuron. Several transcripts up‐regulated by NEPP11 were identified. Because heme oxygenase 1 (HO‐1) mRNA was the most prominently induced and was earlier reported to protect neuronal and non‐neuronal cells against oxidative stress, we focused on it as a possible candidate responsible for the neuroprotective effects. We found NEPP11 to induce HO‐1 protein (32 kDa) in HT22 cells in both the presence and the absence of glutamate, whereas non‐neuroprotective prostaglandins (PGs) Δ12‐PGJ2 or PGA2 did not. Overexpression of HO‐1‐green fluorescence protein (GFP) fusion protein significantly protected HT22 cells against oxidative glutamate toxicity, whereas that of GFP alone did not. Furthermore, biliverdin and bilirubin, products of HO‐1 enzymatic activity on heme, protected HT22 cells from oxidative glutamate toxicity. These results, together with our previous results, suggest that NEPP11 activates the expression of HO‐1 and that HO‐1 produces biliverdin and bilirubin, which result in the inhibition of neuronal death induced by oxidative stress. NEPP11 is the first molecular probe reported to have a neuroprotective action through induction of HO‐1 in neuronal cells.
A novel Antarctic microbial endolithic community within gypsum crusts
Authors: Hughes Kevin A. , Lawley Blair
Published: June 2003

A novel endolithic microbial habitat is described from a climatically extreme site at Two Step Cliffs, Alexander Island, Antarctic Peninsula (71°54′S, 68°13′W). Small endolithic colonies (<3 mm in diameter) are found within the translucent gypsum crust that forms on the surface of sandstone boulders. Gypsum crusts are found on ice‐free rocks throughout the Antarctic and therefore offer potential colonization sites at more inhospitable locations, including sites at higher latitudes. Cyanobacterial, bacterial and fungal components were cultured from the crust material and have been identified as Chloroglea sp., Sphingomonas sp. and Verticillium sp. respectively. A non‐cultured, black‐pigmented fungus was also found. Cyanobacterial primary productivity is low: at depths of 1.2 and 2.5 mm within the crust, estimates of possible cell divisions per year were < 38 and four respectively. This microniche is proposed to provide protection from desiccation, rapid temperature variation and UV radiation flux while allowing penetration of photosynthetically active radiation (PAR) for utilization by phototrophs. The endolithic communities are less extensive than those of the Dry Valleys, continental Antarctica, probably owing to only recent deglaciation (<7000 year ago).
Metabolism of organic compounds in anaerobic, hydrothermal sulphate‐reducing marine sediments
Authors: Tor Jason M. , Amend Jan P. , Lovley Derek R.
Published: June 2003

Previous studies of hot (>80°C) microbial ecosystems have primarily relied on the study of pure cultures or analysis of 16S rDNA sequences. In order to gain more information on anaerobic metabolism by natural communities in hot environments, sediments were collected from a shallow marine hydrothermal vent system in Baia di Levante, Vulcano, Italy and incubated under strict anaerobic conditions at 90°C. Sulphate reduction was the predominant terminal electron‐accepting process in the sediments. The addition of molybdate inhibited sulphate reduction in the sediments and resulted in a linear accumulation of acetate and hydrogen over time. [U‐14C]‐ acetate was completely oxidized to 14CO2, and the addition of molybdate inhibited 14CO2 production by 60%. [U‐14C]‐glucose was oxidized to 14CO2, and this was inhibited when molybdate was added. When the pool sizes of short‐chain fatty acids were artificially increased, radiolabel from [U‐14C]‐glucose accumulated in the acetate pool. L‐[U‐14C]‐glutamate, [ring‐14C]‐benzoate and [U‐14C]‐palmitate were also anaerobically oxidized to 14CO2 in the sediments, but molybdate had little effect on the oxidation of these compounds. These results demonstrate that natural microbial communities living in a hot, microbial ecosystem can oxidize acetate and a range of other organic electron donors under sulphate‐reducing conditions and suggest that acetate is an important extracellular intermediate in the anaerobic degradation of organic matter in hot microbial ecosystems.
An immunomagnetic separation–reverse transcription polymerase chain reaction (IMS‐RT‐PCR) test for sensitive and rapid detection of viable waterborne Cryptosporidium parvum
Authors: Hallier‐Soulier Sylvie , Guillot Emmanuelle
Published: June 2003

The public health problem posed by the waterborne parasite Cryptosporidium parvum incited the water supply industry to develop very accurate analytical tools able to assess the presence of viable oocysts in drinking water. In this study, we report the development of a viability assay for C. parvum oocysts based on immunomagnetic separation and reverse transcription polymerase chain reaction (IMS‐RT‐PCR). The detection limit of the IMS‐RT‐PCR assay, which targets the hsp70 heat shock‐induced mRNA, was in the range of ten viable oocysts per 100‐l tap water samples. Purified Cryptosporidium parvum oocysts were exposed to heating, freezing and three chemical disinfection treatments namely, chlorination, chlorine dioxide treatment and ozonation under conventional doses used in water treatment plants, then detected by IMS‐PCR and IMS‐RT‐PCR. The results obtained by IMS‐PCR showed that none of the treatments had an effect on oocyst detection. The inactivation of oocysts by boiling resulted in no RT‐PCR signal. Chlorine as well as chlorine dioxide did not influence oocyst viability as determined by IMS‐RT‐PCR. Ozone more effectively inactivated oocysts. The IMS‐RT‐PCR assay in conjunction with IMS‐PCR marks the development of a combined detection and viability test which can be used for drinking water quality control as well as for reliable evaluation of treatment efficiency.
Method of DNA extraction and application of multiplex polymerase chain reaction to detect toxigenic Vibrio cholerae O1 and O139 from aquatic ecosystems
Authors: Rivera Irma N. G. , Lipp Erin K. , Gil Ana , Choopun Nipa , Huq Anwar , Colwell Rita R.
Published: June 2003

Vibrio cholerae is a free‐living bacterium found in water and in association with plankton. V. cholerae non‐O1/non‐O139 strains are frequently isolated from aquatic ecosystems worldwide. Less frequently isolated are V. cholerae O1 and V. cholerae O139, the aetiological agents of cholera. These strains have two main virulence‐associated factors, cholera toxin (CT) and toxin co‐regulated pilus (TCP). By extracting total DNA from aquatic samples, the presence of pathogenic strains can be determined quickly and used to improve a microbiological risk assessment for cholera in coastal areas. Some methods suggested for DNA extraction from water samples are not applicable to all water types. We describe here a method for DNA extraction from coastal water and a multiplex polymerase chain reaction (PCR) for O1 and O139 serogroups. DNA extraction was successfully accomplished from 117 sea water samples collected from coastal areas of Perú, Brazil and the USA. DNA concentration in all samples varied from 20 ng to 480 µg µl−1. The sensitivity of the DNA extraction method was 100 V. cholerae cells in 250 ml of water. The specificity of multiplex O1/O139 PCR was investigated by analysing 120 strains of V. cholerae, Vibrio and other Bacteria species. All V. cholerae O1 and O139 tested were positive. For cholera surveillance of aquatic environments and ballast water, total DNA extraction, followed by V. cholerae PCR, and O1/O139 serogroup and tcpA/ctxA genes by multiplex PCR offers an efficient system, permitting risk analysis for cholera in coastal areas.
Nitrite reductase activity of sulphate‐reducing bacteria prevents their inhibition by nitrate‐reducing, sulphide‐oxidizing bacteria
Authors: Greene E. A. , Hubert C. , Nemati M. , Jenneman G. E. , Voordouw G.
Published: June 2003

Sulphate‐reducing bacteria (SRB) can be inhibited by nitrate‐reducing, sulphide‐oxidizing bacteria (NR‐SOB), despite the fact that these two groups are interdependent in many anaerobic environments. Practical applications of this inhibition include the reduction of sulphide concentrations in oil fields by nitrate injection. The NR‐SOB Thiomicrospira sp. strain CVO was found to oxidize up to 15 mM sulphide, considerably more than three other NR‐SOB strains that were tested. Sulphide oxidation increased the environmental redox potential (Eh) from −400 to +100 mV and gave 0.6 nitrite per nitrate reduced. Within the genus Desulfovibrio, strains Lac3 and Lac6 were inhibited by strain CVO and nitrate for the duration of the experiment, whereas inhibition of strains Lac15 and D. vulgaris Hildenborough was transient. The latter had very high nitrite reductase (Nrf) activity. Southern blotting with D. vulgaris nrf genes as a probe indicated the absence of homologous nrf genes from strains Lac3 and Lac6 and their presence in strain Lac15. With respect to SRB from other genera, inhibition of the known nitrite reducer Desulfobulbus propionicus by strain CVO and nitrate was transient, whereas inhibition of Desulfobacterium autotrophicum and Desulfobacter postgatei was long‐lasting. The results indicate that inhibition of SRB by NR‐SOB is caused by nitrite production. Nrf‐containing SRB can overcome this inhibition by further reducing nitrite to ammonia, preventing a stalling of the favourable metabolic interactions between these two bacterial groups. Nrf, which is widely distributed in SRB, can thus be regarded as a resistance factor that prevents the inhibition of dissimilatory sulphate reduction by nitrite.
Development and validation of a diagnostic microbial microarray for methanotrophs
Authors: Bodrossy Levente , Stralis‐Pavese Nancy , Murrell J. Colin , Radajewski Stefan , Weilharter Alexandra , Sessitsch Angela
Published: June 2003

The potential of DNA microarray technology in high‐throughput detection of bacteria and quantitative assessment of their community structures is widely acknowledged but has not been fully realised yet. A generally applicable set of techniques, based on readily available technologies and materials, was developed for the design, production and application of diagnostic microbial microarrays. A microarray targeting the particulate methane monooxygenase (pmoA) gene was developed for the detection and quantification of methanotrophs and functionally related bacteria. A microarray consisting of a set of 59 probes that covers the whole known diversity of these bacteria was validated with a representative set of extant strains and environmental clones. The potential of the pmoA microarray was tested with environmental samples. The results were in good agreement with those of clone library sequence analyses. The approach can currently detect less dominant bacteria down to 5% of the total community targeted. Initial tests assessing the quantification potential of this system with artificial PCR mixtures showed very good correlation with the expected results with standard deviations in the range of 0.4–17.2%. Quantification of environmental samples with this method requires the design of a reference mixture consisting of very close relatives of the strains within the sample and is currently limited by biases inherent in environmental DNA extraction and universal PCR amplification.
Nitrogenase gene diversity and microbial community structure: a cross‐system comparison
Authors: Zehr Jonathan P. , Jenkins Bethany D. , Short Steven M. , Steward Grieg F.
Published: June 2003

Biological nitrogen fixation is an important source of fixed nitrogen for the biosphere. Microorganisms catalyse biological nitrogen fixation with the enzyme nitrogenase, which has been highly conserved through evolution. Cloning and sequencing of one of the nitrogenase structural genes, nifH, has provided a large, rapidly expanding database of sequences from diverse terrestrial and aquatic environments. Comparison of nifH phylogenies to ribosomal RNA phylogenies from cultivated microorganisms shows little conclusive evidence of lateral gene transfer. Sequence diversity far outstrips representation by cultivated representatives. The phylogeny of nitrogenase includes branches that represent phylotypic groupings based on ribosomal RNA phylogeny, but also includes paralogous clades including the alternative, non‐molybdenum, non‐vanadium containing nitrogenases. Only a few alternative or archaeal nitrogenase sequences have as yet been obtained from the environment. Extensive analysis of the distribution of nifH phylotypes among habitats indicates that there are characteristic patterns of nitrogen fixing microorganisms in termite guts, sediment and soil environments, estuaries and salt marshes, and oligotrophic oceans. The distribution of nitrogen‐fixing microorganisms, although not entirely dictated by the nitrogen availability in the environment, is non‐random and can be predicted on the basis of habitat characteristics. The ability to assay for gene expression and investigate genome arrangements provides the promise of new tools for interrogating natural populations of diazotrophs. The broad analysis of nitrogenase genes provides a basis for developing molecular assays and bioinformatics approaches for the study of nitrogen fixation in the environment.