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At least 289 records · Page 16Linked to original sources
PubMed1991

Spectrin breakdown products increase with age in telencephalon of mouse brain.

Calcium activated proteolysis of brain spectrin produces characteristic breakdown products (BDPs), the concentrations of which increase markedly in many instances of brain pathology. Results reported here indicate that levels of the BDPs rise with age (3-30 months) in the telencephalon but not in the hindbrain of Balb/c mice. These observations suggest that spectrin breakdown is a pathologic biochemical marker which increases with age in some but not all brain regions.

Aging↗
PubMed1995

Cellular expression of alpha 4 subunit mRNA of the nicotinic acetylcholine receptor in the developing rat telencephalon.

By contrast to adult brain, little is known on the development of nicotinic acetylcholine receptor (nAChR) expression. Using a digoxigenin-labeled riboprobe for in situ hybridization, alpha 4 nAChR subunit mRNA expression was studied in embryonic and postnatal rat neocortex and hippocampus where it was transiently increased in neuronal subpopulations and preceded cholinergic fiber ingrowth. alpha 4 expression was increased in neocortical layer VIb between E20 and P2 and, about birth, in dentate gyrus granule cells subsequently decreasing to adult levels. nAChR mRNA expression is increased at the developing neuromuscular endplate preceding cholinergic innervation which triggers changes in non-alpha nAChR isoform expression. It has to be elucidated whether similar changes may occur in the telencephalon.

Animals↗
PubMed1995

Tangential migration of luteinizing hormone-releasing hormone (LHRH) neurons in the medial telencephalon in association with transient axons extending from the olfactory nerve.

During embryonic development, luteinizing hormone-releasing hormone (LHRH) neurons migrate to the brain from the medial olfactory epithelium through the olfactory nerve. LHRH neurons enter the brain and migrate tangentially along the medial edge of the telencephalon in close association with a neural cell adhesion molecule (N-CAM) enriched fiber bundle. In the current work we wished to determine whether this N-CAM enriched fiber bundle is an extension of the olfactory nerve. Ablation experiments, immunocytochemistry and diI implants all suggest that LHRH neurons migrate in association with a very small subset of transient N-CAM enriched neuronal processes which extend out of the olfactory nerve proper to the septal-preoptic area.

Animals↗
PubMed1996

L3, a novel murine LIM-homeodomain transcription factor expressed in the ventral telencephalon and the mesenchyme surrounding the oral cavity.

By reverse-transcription polymerase chain reaction method, we isolated a novel murine LIM-homeodomain gene, L3. In situ hybridization analyses revealed that L3 mRNA was localized to the ventral telencephalon and the mesenchyme surrounding the oral cavity of mouse embryo, suggesting that L3 may be involved in the region-specific differentiation of these areas.

Amino Acid Sequence↗
PubMed1992

The influence of the olfactory placode on the development of the telencephalon in Xenopus laevis.

Removal of the sensory plate in Xenopus laevis embryos was performed to study the influence of the olfactory anlage on the development of the forebrain. Embryos, which at stage 22-23 underwent removal of the olfactory anlagen, were killed from stage 47 to 60. In 79% of the animals, two olfactory organs reformed and gave origin to two olfactory nerves which contacted the forebrain. In this instance, the telencephalic hemispheres developed normally. In 14% of the animals, one olfactory organ reformed which contacted the brain by means of one olfactory nerve. This resulted in the development of a unique, reduced in size, cone-shaped telencephalic lobe. In the remaining animals, only a rudiment of the olfactory organ, unconnected with the brain, was present; in these cases, the telencephalon did not develop. Similar results were observed in embryos where olfactory anlagen removal was coupled with damage to, or partial removal of, the prosencephalic vesicle. In animals where lesion of the forebrain was performed without placodal removal, normal development of the forebrain was observed. The developmental relationship observed between the olfactory organ and the forebrain suggests an active role of the nose on the development of the brain.

Animals↗
PubMed1995

Distribution of preproenkephalin messenger RNA in the basal ganglia and limbic-associated regions of the monkey telencephalon.

We studied the distribution of preproenkephalin messenger RNA in the monkey forebrain, using a free-floating method for in situ hybridization histochemistry. Autoradiographs reveal a high level of specific hybridization to preproenkephalin messenger RNA in the monkey striatum and forebrain regions. In the monkey striatum, the distribution of preproenkephalin messenger RNA is heterogeneous. There is variation in the general labeling pattern between regions of the striatum. For example, a particularly densely labeled area of preproenkephalin messenger RNA is observed in the ventral part of the caudal putamen. In addition, at the macroscopic level, there are patches of specific hybridization intermingled with areas containing less specific labeling. This forms a mosaic-like pattern. At the microscopic level, densely labeled individual cells are found among those with little or no specific labeling. Adjacent sections, processed for in situ hybridization and immunohistochemistry, show some correlation between the perikarya containing preproenkephalin messenger RNA and enkephalin-positive fibers in the striatum. Specific hybridization to preproenkephalin messenger RNA is evident throughout the cortical mantle, primarily concentrated in layers 2 and 3. Particularly high levels of preproenkephalin messenger RNA are found in specific limbic-associated cortices, including the piriform allocortex, the agranular area of the orbitofrontal cortex, the agranular insular cortex and the caudal field of the entorhinal cortex. Specific labeling is also present in the granular cell layer of the dentate gyrus and in the amygdaloid complex. This study reveals heterogeneous distribution of dense preproenkephalin messenger RNA in the basal ganglia and high levels of preproenkephalin messenger RNA in specific limbic-associated regions of the monkey telencephalon.

Animals↗
PubMed1996

Neurogranin in the development of the rat telencephalon.

We have used a novel antibody to map the distribution of the protein kinase C substrate protein RC3/neurogranin during the development of the rat telencephalon. Neurogranin appearance in the rat brain is biphasic: it shows an early stage of anatomically restricted, low-intensity expression, and a juvenile stage of anatomically widespread, high-intensity expression. Most of the structures that express neurogranin during development conserve it in the adult stage. Neurogranin expression starts on embryonic day 18 in two different sites-the amygdalar primordium and in the piriform cortex-and is confined to these structures until the first postnatal day (P1). On P1, neurogranin expression increases dramatically in intensity, and appears in the olfactory cortex, isocortex, subiculum and hippocampus. In the striatum, expression starts on P1 and extends to the caudoputamen and parts of the globus pallidus and septum. Particularly complex patterns of labelling can be seen in the amygdala and cerebral cortex. Cortical layers showing early expression are the presumptive layers 4 and 5 in the somatosensory cortex, and layers 2 and 5 in the anterior cingulate and agranular insular cortices. Immunoreactivity is found mostly in cell bodies during the early and juvenile stages, but by the end of the first postnatal week it starts being more apparent in the neuropil. This phenomenon probably reflects the intracellular translocation of neurogranin to distal parts of the dendrites and dendritic spines. This process culminates by the end of the second postnatal week, when the adult pattern is reached. According to the timing and anatomy of its distribution, expression of neurogranin seems to be independently regulated in each telencephalic region by specific signalling mechanisms. It is proposed, on this basis, that neurogranin could be implicated in neuronal differentiation and synaptogenesis during telencephalic development.

Aging↗
PubMed1985

Efferents from the supracommissural ventral telencephalon in the hime salmon (landlocked red salmon, Oncorhynchus nerka): an anterograde degeneration study.

Efferents from the area ventralis telencephali pars supracommissuralis (Vs) of hime salmon (landlocked red salmon, Oncorhynchus nerka) were studied using anterograde degeneration methods. It was found that Vs sends intratelencephalic fibers bilaterally to the internal cell layer of the olfactory bulb and wide areas of telencephalon, while it sends extratelencephalic fibers bilaterally to habenulae, inferior lobes and midbrain tegmenti through medial and lateral forebrain bundles and lateral preoptic area. A possibility was pointed out that some of these extratelencephalic projections are involved in the pathway controlling the sexual behavior which are suggested from behavioral experiments.

Animals↗
PubMed2005

Cellular and molecular control of neurogenesis in the mammalian telencephalon.

The mammalian telencephalon exhibits an amazing diversity of neuronal types. The generation of this diversity relies on multiple developmental strategies, including the regional patterning of progenitors, their temporal specification, and the generation of intermediate progenitor populations. Progress has recently been made in characterizing some of the mechanisms involved. In particular, intermediate progenitors have been shown to play important roles in the generation of neurons in the cerebral cortex, and the properties and lineage relationships between radial glial cells and these intermediate progenitors have recently been examined by elegant time-lapse microscopic studies. Multiple pathways control the progression of neural lineages from multipotent stem cells to intermediate progenitors, postmitotic precursors and finally mature neurons. The regulation of two essential steps, neuronal commitment and specification of subtype identities, is increasingly well understood. These two steps are clearly distinct but co-ordinately regulated by common transcription factors such as neurogenins and Pax6. As our knowledge of the mechanisms of subtype specification of telencephalic neurons progresses, it will become possible to direct stem cells into generating particular telencephalic neuronal populations, opening the way to efficient neuronal replacement therapies.

Animals↗
PubMed2003

Phenotypic expression of monoamines and GABA in the early development of human telencephalon, transient or not transient.

We review the phenotypic expression of molecules involved in monoamine and GABA neurotransmission in the developing human brain. Recent experimental reports have analyzed neurotransmitter signaling before the onset of synaptogenesis, which could act to influence early developmental events such as proliferation, migration, and differentiation of animal brain development. Such signaling may also occur in human development. The expression of molecules involved in neurotransmission in precocious human brain may reflect either the differentiation of a permanent neurotransmitter system of the adult brain or transient expression to serve specific developmental functions different from those in the adult brain. We review the changes observed in the expression of various catecholamine markers such as tyrosine-hydroxylase (TH) immunoreactivity in various neuronal populations of the developing human telencephalon. The specific transporter for serotonin, serotonin transporter (SERT) has been detected in fibers of the internal capsule (IC) during the restricted time period of 12-14 gestational weeks in humans. These serotonin-containing fibers do not correspond to serotoninergic ascending axons from the raphe nuclei. They may be the human counterpart of the thalamo-cortical axons that have been shown to uptake serotonin during the critical period of development of the sensory systems in rodents. GABA phenotypes are expressed in numerous cells of the human ganglionic eminence (GE) and cerebral wall at the end of the embryonic period proper. These results are similar to that described at comparable developmental stages in the mouse and support the hypothesis of an early migration from ganglionic progenitors in humans. But one cannot exclude a transient expression of GABA within the post-mitotic neurons, which could influence early developmental events. In conclusion, data showing the phenotypic expression of molecules in discrete areas of the brain at various points in the protracted human development require careful interpretation.

Animals↗
PubMed2004

Methods for chronic neural recording in the telencephalon of freely behaving fish.

We have adapted for use in fish several of the procedures employed for recording single neuron activity in freely behaving rodents. Developing a method for single unit chronic recording in freely behaving fish was motivated by a need for a comparison across taxa of telencephalic neural activity evoked during spatial navigation by animals of their environments. However, the procedures outlined here can be modified easily for underwater recording from most aquatic species and from other brain areas. Under anesthesia, bundles of stereotrodes or tetrodes were implanted into the dorsolateral region of the goldfish or cichlid telencephalon. An infrared light emitting diode (LED) was also fixed to the fish's head at the time of surgery. After recovery from anesthesia, fish were allowed to swim freely within a large aquarium. Single unit activity was analyzed and correlated with stimulus conditions, behavior, and the location and movement of the LED recorded by a camera tracking system. The value of this technique is demonstrated by providing the first evidence in fish for navigation-related neural firing, including "place cells" that display location-specific discharge.

Action Potentials↗
PubMed2006

Spatial learning and goldfish telencephalon NMDA receptors.

Recent results have demonstrated that the mammalian hippocampus and the dorso-lateral telencephalon of ray-finned fishes share functional similarities in relation to spatial memory systems. In the present study, we investigated whether the physiological mechanisms of this hippocampus-dependent spatial memory system were also similar in mammals and ray-finned fishes, and therefore possibly conserved through evolution in vertebrates. In Experiment 1, we studied the effects of the intracranial administration of the noncompetitive NMDA receptor antagonist MK-801 during the acquisition of a spatial task. The results indicated dose-dependent drug-induced impairment of spatial memory. Experiment 2 evaluated if the MK-801 produced disruption of retrieval of a learned spatial response. Data showed that the administration of MK-801 did not impair the retrieval of the information previously stored. The last experiment analyzed the involvement of the telencephalic NMDA receptors in a spatial and in a cue task. Results showed a clear impairment in spatial learning but not in cue learning when NMDA receptors were blocked. As a whole, these results indicate that physiological mechanisms of this hippocampus-dependent system could be a general feature in vertebrate, and therefore phylogenetically conserved.

Animals↗
PubMed2005

Systemic prenatal insults disrupt telencephalon development: implications for potential interventions.

Infants born prematurely are prone to chronic neurologic deficits including cerebral palsy, epilepsy, cognitive delay, behavioral problems, and neurosensory impairments. In affected children, imaging and neuropathological findings demonstrate significant damage to white matter. The extent of cortical damage has been less obvious. Advances in the understanding of telencephalon development provide insights into how systemic intrauterine insults affect the developing white matter, subplate, and cortex, and lead to multiple neurologic impairments. In addition to white matter oligodendrocytes and axons, other elements at risk for perinatal brain injury include subplate neurons, GABAergic neurons migrating through white matter and subplate, and afferents of maturing neurotransmitter systems. Common insults including hypoxia-ischemia and infection often affect the developing brain differently than the mature brain, and insults precipitate a cascade of damage to multiple neural lineages. Insights from development can identify potential targets for therapies to repair the damaged neonatal brain before it has matured.

Adult↗
PubMed1996

Effects of intracellular K+ and Rb+ on gating of embryonic rat telencephalon Ca(2+)-activated K+ channels.

We have investigated the effects of intracellular K+ and Rb+ on single-channel currents recorded from the large-conductance Ca(2+)-activated K+ (BK) channel of the embryonic rat telencephalon using the inside-out patch-clamp technique. Our novel observation concerns the effects of these ions on rapid flickering of channel openings. Specifically, flicker gating was voltage dependent, i.e., it was reduced by depolarization in the -60 to -10 mV range with equimolar concentrations of K+ ions (150 Ko+/150 Ki+). Removal of Ki+ resulted in significant flickering at all potentials in this voltage range. In other words, the voltage dependence of flicker gating was effectively eliminated by the removal of Ki+. This suggests that a K+ ion entering the channel from the intracellular medium binds, in a voltage-dependent manner, at a site that locks the flicker gate in its open position. No effects of changes in Ki+ were observed on the primary, voltage-dependent gate of the channel. The change in flickering did not cause a change in the mean burst duration, which indicates that the primary gate is stochastically independent of the flicker gate. Intracellular Rb+ can substitute for--and is even more effective than--Ki+ with regard to suppression of flickering. Substitution of Rbi+ for Ki+ also increased the mean burst duration for V > or = -30 mV. Both effects of Rbi+ were removed by membrane hyperpolarization.

Animals↗
PubMed2001

Identification of visual pallial telencephalon in the goldfish, Carassius auratus: a combined cytochrome oxidase and electrophysiological study.

A strategy based upon a comparative decrease in bilateral symmetry of cytochrome oxidase (COX) histochemistry following unilateral eye enucleation was used to identify the primary visual area in the area dorsalis of the telencephalon of the goldfish, Carassius auratus. The lateral zone of area dorsalis (Dl) at about the level of the anterior commissure exhibits such a bilateral difference. A parallel decline in the symmetry COX reactivity was observed in the associated part of the central zone (Dc). Electrophysiological activity using extracellular techniques confirmed the visually-driven activity of neurons in these areas. Lesions confirmed the loci in the lateral zone of area dorsalis, including both its dorsal and ventral parts. Single- and multi-unit recordings exhibited a variety of responses to different light stimuli. Single unit latency measures proved not to be a reliable measure of target areas. Responses habituated to stimuli repeated within 5 s and were only reliably evoked with intervals greater than several seconds.

Action Potentials↗
PubMed1996

Comparison of the developmental effects of two mercury compounds on glial cells and neurons in aggregate cultures of rat telencephalon.

A three-dimensional cell culture system was used as a model to study the influence of low levels of mercury in the developing brain. Aggregating cell cultures of fetal rat telencephalon were treated for 10 days either during an early developmental period (i.e., between days 5 and 15 in vitro) or during a phase of advanced maturation (i.e., between days 25 and 35) with mercury. An inorganic (HgCl2) and an organic mercury compound (monomethylmercury chloride, MeHgCl) were examined. By monitoring changes in cell type-specific enzymes activities, the concentration-dependent toxicity of the compounds was determined. In immature cultures, a general cytotoxicity was observed at 10(-6) M for both mercury compounds. In these cultures, HgCl2 appeared somewhat more toxic than MeHgCl. However, no appreciable demethylation of MeHgCl could be detected, indicating similar toxic potencies for both mercury compounds. In highly differentiated cultures, by contrast, MeHgCl exhibited a higher toxic potency than HgCl2. In addition, at 10(-6) M, MeHgCl showed pronounced neuron-specific toxicity. Below the cytotoxic concentrations, distinct glia-specific reactions could be observed with both mercury compounds. An increase in the immunoreactivity for glial fibrillary acidic protein, typical for gliosis, could be observed at concentrations between 10(-9) M and 10(-7) M in immature cultures, and between 10(-8) M and 3 x 10(-5) M in highly differentiated cultures. A conspicuous increase in the number and clustering of GSI-B4 lectin-binding cells, indicating a microglial response, was found at concentrations between 10(-10) M and 10(-7) M. These development-dependent and cell type-specific effects may reflect the pathogenic potential of long-term exposure to subclinical doses of mercury.

Animals↗
PubMed1997

The effect of unilateral neurotoxic lesions to serotonin fibres in the medial forebrain bundle on the metabolism of [3H]DOPA in the telencephalon of the living rat.

We used quantitative autoradiography to measure the contribution of the 5-hydroxytryptamine (5-HT, serotonin) innervation of rat telencephalon to the synthesis of dopamine (DA) from exogenous L-DOPA. One week after stereotaxic infusions of 5,7-dihydroxy-tryptamine (5,7-DHT, 1.6 micrograms) into the right medial forebrain bundle (MFB), rats received [3H]DOPA (200 microCi,i.v.), which circulated for 90 min. The specific bindings in vitro of the 5-HT uptake site ligand [3H]citalopram and the DA uptake site ligand [125I]RTI-55 were measured in cryostat sections from the prosencephalon. In most structures ipsilateral to the lesion, [3H]citalopram specific binding was substantially reduced (50-90%). In the lateral habenula specific binding declined by only 30-40%, reflecting the presence of a 5-HT pathway deviating from the MFB at the mesencephalic flexure. [125I]RTI-55 binding in the basal ganglia was reduced by 50% on the side of the 5,7-DHT lesion, but was unperturbed in rats pretreated with desmethylimipramine (DMI). 5,7-DHT infusions decreased the synthesis of [3H]DA from [3H]DOPA in vivo in the basal ganglia by (40-90%). Pretreatment with DMI protected [3H]DA synthesis in the basal ganglia, but not in the olfactory tubercle and amygdala ipsilateral to the lesion. Whereas the 5-HT innervation does not contribute greatly to [3H]DA synthesis in the basal ganglia, a substantial proportion of [3H]DA synthesis in olfactory tubercle and amygdala requires an intact 5-HT innervation.

5,7-Dihydroxytryptamine↗
PubMed1999

Augmented expression of macrophage migration inhibitory factor (MIF) in the telencephalon of the developing rat brain.

Macrophage migration inhibitory factor (MIF) has been characterized as a proinflammatory cytokine, hormone, and immunomodulator. We previously demonstrated the distribution of MIF in the adult rat brain and revealed its expression in neurons as well as glial cells. In this study, we investigated the localization of MIF in the developing rat brain from embryonic day (ED) 13 to ED19, and after birth from postnatal day (PD) 1 to PD28 using both immunohistochemistry and in situ hybridization. On ED16, the signals of MIF mRNA were high in the ventricular, subventricular, and intermediate zones of the telencephalon, in which 'neuropoietic' progenitor cells proliferate and migrate from the ventricular zone to the superficial layer in the cerebral cortex. The mRNA expression was detected throughout the postnatal period, and intense signals of the transcript were seen in the ventricle and in layers I, II and III of the cerebral cortex at PD5. Similarly, positive staining of MIF protein was seen in the ventricular zone by immunohistochemical analysis, although the positively stained area appeared to be smaller than the mRNA expression. Taken together, these results suggest that the increase in MIF mRNA in the developing brain reflects the growth and maturation of neurons and glial cells.

Animals↗