bluuebunny/crossref_metadata_2025_split huggingface dataset:
The G‐protein γ‐subunit Gy8 is Expressed in the Developing Axons of Olfactory and Vomeronasal Neurons
Authors: Tirindelli Roberto , Ryba Nicholas J. P. 
Published: April 2006

AbstractThe tissue localization of the G‐protein y‐subunit, Gy8, that is specifically expressed in the olfactory and vomeronasal neurons, was studied in rats at different ages: embryonic day 16, postnatal days 1,7, 14 and 35, and adult. G8 appears to be a specific marker of the immature olfactory and vomeronasal neurons. Its distribution differs from that of Golfα, a G‐protein α‐subunit which is predominantly expressed in mature olfactory neurons. G8 immunoreactivity indicates that an undifferentiated organization of the olfactory epithelium persists up to 3 weeks of age, though neonates possess a functional sense of smell. Gy8 accumulates at the highest levels in the axons of the developing olfactory neurons 2 weeks after birth (postnatal day 14). Moreover, up to postnatal day 14, Gy8–positive neurons are present in the region of the olfactory and vomeronasal epithelium, where they are not observed in later life. In the olfactory epithelium and in the bulb, Gy8 expression becomes weaker and patchy with increasing age, suggesting that the process of continuous regeneration of olfactory neurons occurs in discrete areas. G8–enhanced expression following axotomy indicates that this system is potentially active throughout life. Conversely, in the vomeronasal epithelium Gy8 expression persists virtually unmodified in the adult. This indicates that the degree of differentiation may differ between olfactory and vomeronasal neurons.
Timing and Regulation of trkB and BDNF mRNA Expression in Placode‐derived Sensory Neurons and their Targets
Authors: Robinson Michelle , Adu Jimi , Davies Alun M. 
Published: April 2006

AbstractThe sensory neurons of the vestibular and nodose ganglia of the chicken embryo have nearby and distant targets, respectively. in vitro studies have shown that these neurons survive independently of neurotrophins when their axons are growing to their targets and become dependent on brain‐derived neurotrophic factor (BDNF) for survival when their axons reach the vicinity of their targets. Although the timing of BDNF dependence is principally controlled by an intrinsic timing mechanism in the neurons, the onset of dependence can be accelerated by BDNF exposure toward the end of the phase of neurotrophin independence. We have used quantitative reverse transcription/polymerase chain reaction to study the expression of transcripts coding for BDNF and the catalytic isoform of its receptor tyrosine kinase, TrkB, in these neurons and their targets at different stages of development. We show that the peripheral and central target tissues of these neurons express BDNF mRNA prior to the arrival of sensory axons. Vestibular neurons express trk6 mRNA before nodose neurons, which accords with the earlier response of vestibular neurons to BDNF. In culture, early nodose neurons start expressing trkB mRNA after 36 h incubation, which is 36 h before these neurons become dependent on BDNF for survival. Although BDNF does not affect the timing and level of trkB mRNA expression during the first 48 h in vitm, it increases the level of trk8 mRNA after this time. The timing of BDNF‐induced elevation of trkB mRNA correlates with the period during which BDNF exposure accelerates the onset of BDNF dependence in nodose neurons. These results suggest that the timing of BDNF dependence in developing sensory neurons is due in part to expression of catalytic TrkB and demonstrate that a BDNF autocrine loop is not required for the survival of sensory neurons during the earliest stages of their development.
Immortalized Hypothalamic Neurons Express Metabotropic Glutamate Receptors Positively Coupled to Cyclic AMP Formation
Authors: Sortino M. A. , Aleppo G. , Copani A. , Casabona G. , Nicoletti F. , Ventra C. , Kuhn R. , Knöpfel T. , Malitschek B. , Canonico P. L. 
Published: April 2006

AbstractWe have characterized the expression pattern and pharmacological profile of activation of metabotropic glutamate receptors (mGluRs) in immortalized, gonadotropin releasing hormone (GnRH)‐secreting GT1‐7 cells, which represent a homogeneous cellular population of hypothalamic origin. These cells are known to respond to the mGluR agonist (1S, 3R)‐cyclopentanedicarboxylic acid (1S, 3R‐ACPD) with increased GnRH release. To establish which specific mGluR subtypes are expressed by GT1‐7 cells, we used polyclonal antibodies raised against non‐conserved regions of the carboxy‐terminal domains of individual subtypes. The selectivity of these antibodies was tested in HEK 293 cells transiently transfected with each mGluR subtype. GTl‐7 cells stained positively for the subtypes mGluRla, ‐1b and ‐5 (belonging to group I mGluRs), mGluR2/3 (group 11) and mGluR7 (group 111). Agonists of group I mGluRs, including 1S, 3R‐ACPD, activated phosphoinositide hydrolysis in GT1‐7 cells. This effect, however, was manifested only when cell density was low, and it disappeared when cells reached confluence. Stimulation of phosphoinositide hydrolysis could not therefore have been related to hormone secretion because 1S, 3RACPD effectively released GnRH in confluent cultures. We then focused on group II and Ill mGluRs, which in transfected cells are negatively linked to adenylate cyclase activity. Unexpectedly, however, agonists which preferentially activate group II and Ill mGluRs increased both basal and forskolin‐stimulated cAMP accumulation in GT1‐7 cells. Stimulation of GAMP accumulation by mGluR agonists was not prevented by enzymatic depletion of endogenous adenosine, but was obliterated when cells were incubated with agonists of receptors positively coupled to adenylate cyclase, such as P‐adrenergic and prostaglandin E2 receptors. These results suggest that GT1‐7 cells express a novel mGluR subtype positively coupled to adenylate cyclase, which shares the same transduction pathway of other classical receptors coupled with a G,‐type of GTP‐binding protein.
The Course and Termination of Corticothalamic Fibres Arising in the Visual Cortex of the Rat
Authors: Lozsádi D. A. , Gonzalez‐Soriano J. , Guillery R. W. 
Published: April 2006

AbstractCorticothalamic axons have been studied in adult Lister hooded rats with single or dual injections of tracers into the visual cortex. Labelled axons leave medial and lateral injection sites in separate or partially overlapping bundles along parallel trajectories in the subcortical white matter. In the internal capsule they converge and both bundles enter roughly the same sector of the thalamic reticular nucleus (TRN). Their reticular terminal fields, however, differ. Axons from a medial injection site innervate more lateral parts of the TRN than do the axons from lateral injection sites. The most medial third of the TRN is not innervated from area 17 but receives a topographically arranged input from peristriate cortex (Crabtree and Killackey, 1989, Eur J. Neurosci., 1, 94‐109; Coleman and Mitrofanis, 1996, EWK J. Neurosci., 8, 388‐404). The two groups of axons then separate in the dorsal thalamus, axons from medial parts of visual cortex turning caudally into lateral regions of the lateral geniculate nucleus, whereas fibres from more lateral cortex continue into medial parts of the nucleus. Connolly and van Essen (1984, J. Comp. Neurol., 226, 544‐564) and Nelson and LeVay (1985, J. Comp. Neurol., 240, 322‐330) have shown that in the geniculocortical pathway the two groups of fibres cross over in the subcortical white matter, probably in the region of the subplate. We show that the corticothalamic pathway also has a crossing, but it occurs in, or close to, the diencephalon itself, in the region of the perireticular nucleus. This result suggests that each of these pathways, the geniculocortical and the corticogeniculate, may undergo reorganization within distinct cerebral zones, one diencephalic for the corticothalamic axons and the other telencephalic for the thalamocortical axons.
An Analysis of an Axonal Gradient of Phosphorylated MAP 1B in Cultured Rat Sensory Neurons
Authors: Bush Maxwell S. , Goold Robert G. , Moya Fernando , Gordon‐Weeks Phillip R. 
Published: April 2006

AbstractThe present study investigated the cellular distribution of a developmentally regulated phosphorylated form of MAP 1B recognized by monoclonal antibody (mAb) 150 in cultures of dorsal root ganglia. The cell soma and the whole axon, when it first appears, are labelled, but longer axons label with a proximodistal gradient, such that the cell soma and proximal axon become unlabelled, whilst the distal axon and growth cone label strongly. Double‐labelling experiments with mAb 150 and a polyclonal antibody (N1–15) that recognizes all forms of MAP 1B demonstrated that MAP 1B is distributed along the entire length of axons with gradients, so the gradient of phosphorylated MAP 1B is not due to a loss or absence of MAP 1B from the proximal axon. The proportion of axons from 20 h cultures that were labelled with a mAb 150 gradient was at least 80% and this proportion was independent of the nerve growth factor concentration of the culture medium. Analysis of axons ranging in length from 100 to 700 μm and labelled with a gradient showed that the unlabelled proximal portions of axons increased in length more slowly than the labelled distal axon. Axons labelled along their entire length accounted for no more than 19% of the axonal population and analysis of these showed them to be frequently <400 μm long. After simultaneously fixing and detergent‐extracting cultures this proportion rose significantly to 93%, suggesting that in the proximal axon the mAb 150 epitope is masked by some factor(s) that is removed by detergent extraction. The possibility that mAb 150 could not access the epitope in the proximal axon was discounted because another IgM, mAb 125, which recognizes a different phosphorylation epitope on MAP 1B, labelled the proximal axon of conventionally fixed cultures. In growth cones of fixed and extracted neurons examined by immunofluorescence, the mAb 150 labelling strongly colocalized to bundled microtubules in the distal axon shaft and the C‐domain. In the P‐domain, mAb 150 staining was weaker and more widely distributed than the microtubules. Immunogold electron microscopy confirmed that antibody N1–15 and mAb 150 strongly labelled the bundled microtubules in the C‐domain and also showed that individual microtubules in the P‐domain, some of which lie alongside actin filament bundles of filopodia, were labelled lightly and discontinuously with both antibodies. This suggests that the phosphorylated isoform of MAP 1B recognized by mAb 150 may be involved in bundling microtubules in the proximal region of the growth cone and in the interaction between microtubules and actin filaments in the P‐domain.
Kinematic Analysis of the Cat Shoulder Girdle during Treadmill Locomotion: an X‐ray Study
Authors: Boczek‐Funcke A. , Kuhtz‐Buschbeck J. P. , Illert M. 
Published: April 2006

AbstractA quantitative kinematic analysis of the movements of the shoulder girdle in the three dimensions of space during treadmill locomotion (velocity range 0.33–1.2 m/s) was performed in two cats. Since the movement patterns of the scapula and the humeroscapular joint can only vaguely be estimated through the overlying skin we used implanted metal spheres placed on the scapula in combination with three‐dimensional pulsed X‐ray cinematography (time resolution 20 ms) to reconstruct the excursions of the scapula, the humerus and the elbow and to calculate the respective angular amplitudes and velocities. The movements of the scapula relative to the Th4 spinous process consist of four major components: (i) a monophasic flexion (caudocranial movement of the glenoid fossa during swing)/extension (craniocaudal movement of the glenoid fossa during stance) sequence, the fulcrum for which sequence is situated near the vertebral border of the scapula at the medial elongation of the scapular spine; (ii) a vertical monophasic up/down sequence of the fulcrum relative to the trunk, the highest vertical position being reached during mid‐stance and the lowest vertical position during mid‐swing; (iii) a biphasic abduction/adduction sequence during swing and during stance respectively; and (iv) small rotations along the scapular spine. The trajectory recordings of the scapula indicate that the scapula yields relative to the trunk under the body weight after ground contact. The angular excursions of the humeroscapular joint consist of: (i) a flexion/extension sequence during swing, a yield after ground contact and a final extension at the end of stance; (ii) an adduction and outward rotation during the early swing phase flexion; (iii) an abduction and inward rotation during the late swing phase extension; and (iv) an adduction during the yield with only minor rotations during the whole stance phase. The movement patterns are discussed in view of the muscular synergies necessary to guide the scapula and the humerus during stance and swing, and in relation to the implications for the organization of these patterns in spinal neuronal systems.
A p65/p95 Neural Surface Receptor is Expressed at the S‐G2 Phase of the Cell Cycle and Defines Distinct Populations
Authors: Rebai Najet , Almazan Guillermina , Wei Ling , Greene Mark I. , Uri Saragovi H. 
Published: April 2006

AbstractA surface receptor complex of Mr˜65 000 (p65) and ˜95 000 (p95) is expressed in cells of the central nervous system of mice. This receptor is recognized by monoclonal antibody 87.92.6 or by reovirus type 3 haemagglutinin as unnatural ligands. The p65/p95 receptor is expressed mostly in neural embryonic precursors undergoing proliferation, especially those in the S‐G2 phase of the cell cycle. Receptor expression decreases progressively throughout embryogenesis to low but detectable levels in the adult brain. Biochemical characterization revealed that the neural p65/p95 receptor complex is indistinguishable from the p65/p95 receptor expressed in T cells, where receptor ligation leads to a mitogenic block. In neural and lymphoid tissues the p65/p95 receptor (or an associated protein) possesses a tyrosine kinase enzymatic activity. Receptor ligation in neural cells resulted in the rapid tyrosine phosphorylation of cellular proteins which are different from substrates phosphorylated in T cells. Differential substrate coupling to the receptor may account for differences in signal transduction and biology between neural cells and T cells. Further study of this receptor complex may help define important features of neural proliferation, differentiation and survival.
Less Segregated Processing of Visual Information in V2 than in V1 of the Monkey Visual Cortex
Authors: Tamura Hiroshi , Sato Hiromichi , Katsuyama Narumi , Hata Yoshio , Tsumoto Tadaharu 
Published: April 2006

AbstractTo test the possibility of cross‐talk between parallel pathways dealing with different aspects of visual information, such as orientation, direction of motion and colour in cortical area V2, we quantitatively analysed visual responses of 121 V2 cells recorded from anaesthetized and paralysed macaques and compared them with those of 147 V1 cells. A selectivity index of visual responses was calculated for each neuron, which was then classified as selective or not to a particular attribute of visual stimuli. Twenty‐one percent of the V2 neurons had dual selectivity to both colour and direction of stimulus motion (C&D cells). In V1, only 5% of the cells were C&D cells. Thus, the proportion of C&D cells significantly increased from V1 to V2. We also carried out cross‐correlation analysis of spike trains recorded simultaneously from pairs of V2 neurons or pairs of V1 neurons. In V2, correlated firings could be observed between cells with completely different optimal orientation, such as orthogonal, while it was never observed in V1. The cross‐correlation analysis further indicated that functional interactions in V2 were more widespread than those in V1. These results suggest that neurons which have different functional properties become less segregated, and that functional interactions become more widespread in V2 than in V1.
Tissue‐specific and Developmental Expression of Pituitary Adenylate Cyclase‐activating Polypeptide (PACAP) Receptors in Rat Brain
Authors: D'Agata Velia , Cavallaro Sebastiano , Stivala Franca , Travali Salvatore , Canonico Pier Luigi 
Published: April 2006

AbstractThe two forms of pituitary adenylate cyclase‐activating polypeptide, PACAP27 and PACAP38, are novel members of the vasoactive intestinal peptide (VIP)/secretin/glucagon family of peptides. PACAP receptors that are positively coupled to adenylate cyclase and phospholipase C have been recently identified. We examined the expression of PACAP receptors in the rat cortex, hippocampus, cerebellum and hypothalamus during postnatal development. Functional studies revealed PACAP stimulation of cAMP formation in all the brain areas examined and [3H]inositol monophosphate ([3H]insP) accumulation only in the cerebellum and hypothalamus. Throughout development, the efficacy of PACAP in stimulating cAMP formation slightly increased in the cortex and hypothalamus and decreased in the hippocampus and cerebellum; PACAP stimulation of [3H]lnsP formation decreased in the cerebellum and remained steady in the hypothalamus. The effects of PACAP27 and PACAP38 on cAMP levels and inositol phospholipid hydrolysis were dose‐dependent between 1 and 100 nM. In the same brain areas, treatment with VIP increased cAMP formation at doses greater than 100 nM and failed to affect [3H]lnsP content, thus suggesting the existence of type‐l PACAP receptors. The reverse transcription polymerase chain reaction (RT‐PCR) was used to analyse the mRNA expression of type‐l PACAP receptor splice variants. PACAP receptor gene expression in the central nervous system was regulated in a developmental‐ and tissue‐specific manner. The PACAP‐R transcript was detected in all the brain areas examined whereas PACAP‐R‐hop mRNA occurred only in the cerebellum and hypothalamus. The different expression profiles and functional properties of PACAP receptors in the developing rat brain suggest an involvement of PACAP in histogenesis, maturation and neurotransmission.
The Intrinsic Optical Signal Evoked by Chiasm Stimulation in the Rat Suprachiasmatic Nuclei Exhibits GABAergic Day‐Night Variation
Authors: Trachsel Lorenz , Dodt Hans‐Ulrich , Zieglgänsberger Walter 
Published: April 2006

AbstractInfrared light transmittance imaging was used in rat hypothalamic slices to record an intrinsic optical signal (IOS) of the cell ensemble in the suprachiasmatic nuclei (SCN), the locus of the endogenous circadian clock. Upon optic chiasm stimulation, a transient IOS was observed in an area conforming to the known retinohypothalamic tract innervation in the ventral SCN. An increase in extracellular Mg2+ concentration to 10 mM reduced the IOS, suggesting that the elicited IOS is dependent on synaptic transmission. D‐2‐Amino‐5‐phosphonopentanoic acid and muscimol suppressed the elicited IOS, indicating that NMDA and GABAA receptor‐mediated mechanisms were involved in cell ensemble activity reflected in the IOS. The extracellularly recorded spiking of SCN neurons located outside the IOS area remained largely unaffected by the afferent stimulus. Neurons located within the IOS area responded with a depressed electrical discharge, manifesting an inverse relationship between single‐unit discharge and the optical measure. The influence of the endogenous circadian rhythm on the elicited IOS was assessed by carrying out daytime‐dependent concentration‐response experiments. NMDA and non‐NMDA receptor specific compounds did not exhibit significant day‐night differences, whereas GABA‐specific ligands showed a significant day‐night variation in activity. The competitive GABAA receptor antagonist bicuculline enhanced the IOS exclusively in the daytime SCN. 5α‐Pregnane‐3α, 21‐diol‐20‐one (allotetrahydrodeoxy‐corticosterone), a neuroactive steroid that potentiates GABAergic inhibition, suppressed the IOS in the night‐time SCN more than in the daytime SCN. This suggests that in the rat the level of extracellular GABA is higher in the night‐time SCN compared to the daytime SCN.
A Single‐cell Study of the Axonal Projections Arising from the Posterior Intralaminar Thalamic Nuclei in the Rat
Authors: Deschênes Martin , Bourassa Jacques , Doan Van Diep , Parent André 
Published: April 2006

AbstractThalamostriatal projections arising from the posterior intralaminar nuclei (Pl; the parafascicular nucleus and the adjacent caudalmost part of the posterior thalamic group) were studied in rats by tracing the axons of small pools of neurons labelled anterogradely with biocytin. Thirteen Pl cells were also stained by juxtacellular application of the tracer. Relay cells of Pl nuclei have a morphology that differs radically from the classical descriptions of the bushy cells which represent the main neuronal type of the sensory thalamic relay nuclei. Pl cells have ovoid or polygonal somata of ˜20–25 μm, from which emerge four or five thick, long and poorly branched dendrites bearing spines and filamentous appendages; their dendritic domains extend for up to 1.5 mm. Before leaving the nucleus 20% of axons give off collaterals that ramify locally. All axons course through the thalamic reticular nucleus, where they emit one or two poorly branched collaterals, traverse the globus pallidus, where they also distribute collaterals, and arborize massively in the striatum and sparsely in the cerebral cortex. At the striatal level four or five collaterals leave the main axon and terminate in patches scattered dorsoventrally within a rostrocaudally oriented slab. As revealed by calbindin D‐28k immunohistochemistry, only the matrix compartment receives terminations from Pl axons. The cortical branch forms small terminal puffs centred upon layer VI of the motor cortex. Before entering the striatum some axons of the parafascicular nucleus give rise to descending collaterals that arborize in the entopeduncular nucleus, in the subthalamic nucleus and in the vicinity of the red nucleus. Other axons arising from the caudal part of the posterior group send descending branches only to the entopeduncular nucleus. These findings show that Pl cells belong to a distinct category of thalamic relay neurons which, beside their massive projection to the striatum, also distribute collaterals to other components of the basal ganglia. Moreover, these results provide the first direct evidence that virtually all Pl cells project to both striatum and cerebral cortex. Finally, it is proposed on the basis of morphological, histochemical and hodological criteria that the caudal part of the posterior thalamic group in the rat is homologous to the suprageniculate‐limitans nuclei of cats and primates.