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At least 19 recordsLinked to original sources
PubMed1993

Avian photogenic epilepsy and embryonic brain chimeras: neuronal activity of the adult prosencephalon and mesencephalon.

Photogenic genetic epilepsy was studied in an avian model, using either the Fayoumi epileptic chicken (Fepi) or neural chimeras obtained by replacement of embryonic brain vesicles in normal chickens with those of Fepi embryos. In these two kinds of animals motor seizures accompanied by electroencephalographic (EEG) desynchronization and flattening (DF) were evoked by intermittent light stimulation (ILS). In chimeras with only the prosencephalon grafted, motor seizures were less severe but DF remained. ILS-induced DF persisted under paralysis by gallamine triethiodide (Flaxedil). Extracellular recordings were made in the prosencephalon (wulst) and in the mesencephalon (optic tectum) of paralysed animals. Units recorded in the prosencephalon of Fepi and chimeras showed abnormal interictal bursting activity, distinctly different from the non-epileptic Fayoumi heterozygotes (Fhtz) and normal chickens. The mesencephalic units of Fepi and chimeras having both prosencephalon and mesencephalon grafted showed two types of abnormal activities during ILS-induced DF, which were distinct from the non-epileptic chickens: type I neurons displaying early, high sensitivity to ILS followed by a prolonged suppression of activity; type II neurons displaying an early and prolonged suppression of activity. The results are discussed with respect to the brain structures generating ictal and interictal EEG activities and motor seizures.

Animals↗
PubMed1991

Induction of a mesencephalic phenotype in the 2-day-old chick prosencephalon is preceded by the early expression of the homeobox gene en.

The homeobox gene en, homologous to the gene en-grailed of Drosophila, is expressed in the metencephalic-mesencephalic segment of the vertebrate neural tube. Using quail-chick chimeras, an antibody against en proteins, and cytoarchitectonic techniques, we demonstrate that metencephalon transplanted to prosencephalon, at E2, maintains a high level of en proteins and its presumptive cerebellar fate. The ectopic metencephalon induces in the contiguous host prosencephalon the expression of en and, subsequently, a mesencephalic phenotype. These related genetic and phenotypic expressions indicate that the transcriptional regulatory en gene is involved in cerebellar and mesencephalic cyto-differentiation. The expression of en can also be induced in chick prosencephalon by a mammalian metencephalic graft, indicating that the factors regulating the transcription of en are phylogenetically well conserved.

Animals↗
PubMed2001

Coordinate expression of Fgf8, Otx2, Bmp4, and Shh in the rostral prosencephalon during development of the telencephalic and optic vesicles.

Previous studies suggest that Fgf8 has a key role in regulating vertebrate development. In the rostral head of the embryonic chicken, there are increasing numbers of separate Fgf8 domains; these are present in tissues that appear to have previously expressed Otx2. As Fgf8 expression becomes established, Otx2 expression weakens, but remains in cells abutting the Fgf8 expression domain. These Fgf8 expression domains are closely associated with tissues expressing Bmp4 and Shh. Based on analogy with the embryonic limb, we suggest that Fgf8, Bmp4 and Shh function together in patterning regions of the embryonic head. Gene expression changes are particularly prominent in 14-21 somite stage embryos in the rostral forebrain, during early morphogenesis of the telencephalic and optic vesicles, when several new interfaces of Fgf8, Bmp4 and Shh are generated. To gain insights into the functions of fibroblast growth factor 8 (FGF8) in the embryonic forebrain, we studied the effects of implanting beads containing this protein in the dorsal prosencephalon of embryonic day 2 chicken embryos. Ectopic FGF8 had profound effects on morphogenesis of the telencephalic and optic vesicles. It disrupted formation of the optic stalk and caused a transformation of the pigment epithelium into neural retina. Within the telencephalon, FGF8 beads frequently induced a sulcus that had features of an ectopic rostral midline. The sulcus separated the telencephalon into rostral and caudal vesicles. Furthermore, we present evidence that FGF8 can regulate regionalization of the prosencephalon through inhibition of Otx2 and Emx2 expression. Thus, these experiments provide evidence that FGF8 can regulate both morphogenesis and patterning of the rostral prosencephalon (telencephalic and optic vesicles). FGF8 beads can induce midline properties (e.g. a sulcus) and can modulate the specification and differentiation of adjacent tissues. We suggest that some of these effects are through regulating the expression of homeobox genes (Otx2 and Emx2) that are known to participate in forebrain patterning.

Age Factors↗
PubMed1976

Effect of stagnant hypoxia on acid ribonuclease activity in the rat prosencephalon during ontogenesis.

In the rat prosencephalon it proved possible to differentiate lysosomal ribonuclease from alkaline ribonuclease activity, which could be detected only in the presence of p-chlormercuribenzoate. Acid RNase activity related to the amount of protein in the prosencephalon fell during ontogenesis. It was not significantly affected by four hours' stagnant hypoxia induced by ligation of both carotids. Its release from the lysosomes rose, however (when isotonic homogenates were spun at 20,000 g, acid ribonuclease activity in the supernatants was elevated). The absence of correlation between this activation and the degree of maturity of the nervous tissue refutes the hypothesis that regulation of this enzyme is per se responsible for the known changes induced by hypoxia in the RNA content of the prosencephalon of rats of different ages. On the contrary, the results indirectly support studies which demonstrate changes in the extent of RNA synthesis after hypoxia.

Age Factors↗
PubMed2001

Intrasexual and intersexual dimorphisms of the red salmon prosencephalon.

Intrasexual as well as intersexual dimorphisms were found in the prosencephalon and mesencephalon of adult Oncorhynchus nerka (red/sockeye salmon). These dimorphisms are concerned with the position of the preoptic nucleus, nucleus lateralis tuberis, habenula, third ventricle, tectal ventricles, preoptic recess, recessus lateralis, horizontal commissure, posterior commissure, and toral commissure. The intrasexual dimorphism was characterized by either a rostral ("r"-pattern) or a caudal ("c"-pattern) position of the preoptic region as well as varying locations of other structures within the prosencephalon. As compared to "c"-pattern fish, the preoptic nucleus and nucleus lateralis tuberis were located more rostral, and the habenula was positioned further caudal, in "r"-type animals. The intersexual dimorphism was also characterized by different positions of the structures listed above. With the exception of the preoptic nucleus, all of these were located further rostral in "r"-pattern females than in type "r" males. In "c"-pattern females, they were positioned further caudal than in type "c" males. The number of neurons in the parvocellular and in the magnocellular portion of the preoptic region differed in the two genders with respect to "r"- as well as "c"-pattern fish. Males had more neurons than females in both the magno- and the parvocellular subdivisions of the preoptic region. In "r"- and "c"-pattern fish, the average size of magnocellular preoptic neurons was larger in females than in males. The observed intersexual variations may reflect gender-specific differences in the control of the pituitary. Functional correlates of intrasexual dimorphism are obscure.

Animals↗
PubMed2002

Coordinate regulation and synergistic actions of BMP4, SHH and FGF8 in the rostral prosencephalon regulate morphogenesis of the telencephalic and optic vesicles.

We investigated the roles of bare morphogenetic protein (BMP), sonic hedgehog (SHH) and fibroblast growth factor (FGF)-expressing signaling centers in regulating the patterned outgrowth of the telencephalic and optic vesicles. Implantation of BMP4 beads in the anterior neuropore of stage 10 chicken embryos repressed FGF8 and SHH expression. Similarly, loss of SHH expression in Shh mutant mice leads to increased BMP signaling and loss of Fgf8 expression in the prosencephalon. Increased BMP signaling and loss of FGF and SHH expression was correlated with decreased proliferation, increased cell death, and hypoplasia of the telencephalic and optic vesicles. However, decreased BMP signaling, through ectopic expression of Noggin, a BMP-binding protein, also caused decreased proliferation and hypoplasia of the telencephalic and optic vesicles, but with maintenance of Fgf8 and Shh expression, and no detectable increase in cell death. These results suggest that optimal growth requires a balance of BMP, FGF8 and SHH signaling. We suggest that the juxtaposition of Fgf8, Bmp4 and Shh expression domains generate patterning centers that coordinate the growth of the telencephalic and optic vesicles, similar to how Fgf8, Bmp4 and Shh regulate growth of the limb bud. Furthermore, these patterning centers regulate regional specification within the forebrain and eye, as exemplified by the regulation of Emx2 expression by different levels of BMP signaling. In summary, we present evidence that there is cross-regulation between BMP-, FGF- and SHH-expressing signaling centers in the prosencephalon which regulate morphogenesis of, and regional specification within, the telencephalic and optic vesicles.

Abnormalities, Drug-Induced↗
PubMed1998

Mediobasal and mantle defect of the prosencephalon: lobar holoprosencephaly, schizencephaly and diabetes insipidus.

An infant is described who had a combination of lobar holoprosencephaly and open-lip schizencephaly. Midline fusion of the basal ganglia was associated with bilateral absence of abundant parts of the brain mantle. Agenesis of the corpus callosum, hypoplasia of the optic nerves and chiasm, absence of the septum pellucidum, posterior pituitary and olfactory bulbs were further components of the malformation. Blindness, intractable seizures, spastic tetraplegia, somatomental retardation and diabetes insipidus were the main clinical features. A defect in the induction of the mediobasal part of the prosencephalon and failure of cell proliferation can be responsible for this complex malformation. Recent results of homeobox gene research relevant to the development of the prosencephalon are discussed.

Brain↗
PubMed1986

[Morphological characteristics of the changes in the prosencephalon of guinea pigs exposed to general vibrations].

After 7 or 30 days of exposure to general vibration (frequency: 40 Hz, amplitude: 1 mm) for 3 hours per day, the prosencephalon of guinea pigs exhibited a wide range of morphological changes, including congestion, haemorrhages, the presence of the heterochromic neurons and perivascular spaces as well as diffuse spongiosis. In contrast, after 14 days' exposure to general vibration of the same parameters, diffuse spongiosis of the prosencephalon was found in all the animals under examination. Hypothalamus, cerebral cortex and periventricular gray matter were unaffected by spongiosis in most of the animals. The nerve fibre sheats were unchanged in all cases.

Animals↗
PubMed1980

[A new concept about the morphogenesis of the prosencephalon in mammals (author's transl)].

The development of the prosencephalon of the mouse has been studied from the 8th to the 13th day post-conception, and some details of mammalian prosencephalic morphogenesis have thus been elucidated. The temporal pattern of development has been analysed in serial semithin coronal sections, and the prosencephalon reconstructed at different ages. The morphological differentiation of the cerebral hemispheres is dependent on a combination of cell proliferation and cell death. Necrosis thins the prosencephalic walls in certain regions (lamina terminalis and "choroid plate"). It is around the lamina terminalis, the choroid plate, and the zone of fusion of the walls of the dorsal and ventral telodiencephalic sulci that the prosencephalic vesicle develops. Thus, the olfactory bulbs are formed rostrally and the lateral ventricles laterally. The fusion between the telencephalic and diencephalic walls occurs at the ependymal surfaces of the dorsal and ventral telodiencephalic sulci, and not at their pial surfaces. The limits between the lateral ventricles and the 3rd ventricle are constituted rostrally by the lamina terminalis, dorsally and ventrally by a region where the corpus striatum mediale and the "choroid plate" meet, and caudalli by the fusion of the ependymal surfaces of the dorsal and ventral telodiencephalic sulci.

Animals↗
PubMed1998

Lectin staining in the basal nucleus (Meynert) and the hypothalamic tuberomamillary nucleus of the developing human prosencephalon.

Previous studies have demonstrated that extracellular matrix glycoconjugates, shown by lectin-histochemistry with Vicia villosa agglutinin (VVA) and peanut agglutinin (PNA) as so-called perineuronal nets, play an important role in brain maturation. Concanavalin A (ConA) binding to neuronal surface glycoconjugates may be a marker of synaptic junctions. The present study was done to demonstrate the binding sites of these lectins in two functionally related nuclei of the prosencephalon, the basal nucleus (Meynert) and the hypothalamic tuberomamillary nucleus. Fetal brains of 16-36 weeks of gestation were examined by using VVA, PNA, and ConA to determine appearance and distribution patterns of specific lectin-binding sites on glycoconjugates during fetal brain development. The basal nucleus and the tuberomamillary nucleus showed a characteristic "cellular staining" that may have been due to cytoplasmatic labeling, surface labeling, or both. Lectin-staining occurred much earlier in the basal nucleus than in the tuberomamillary nucleus. Although all three lectins were bound to neurons of the basal nucleus, only ConA-positive neurons were observed in the tuberomamillary nucleus. In conclusion, lectin-labeled cells most probably represent projection neurons that are GABAergic (tuberomamillary nucleus) or cholinergic (basal nucleus). Labeling with the three lectins demonstrated nuclear-specific staining patterns that occur early in fetal development and gradually increase. Binding sites for lectins characterizing perineuronal nets (VVA, PNA) occurred only in the basal nucleus, whereas binding sites for ConA on neuronal-surface glycoconjugates, which seem to play a role in early synaptogenesis, were present in the basal and the tuberomamillary nucleus. The basal nucleus, however, expressed ConA binding sites distinctly earlier, probably indicating early arriving afferents.

Cell Nucleus↗
PubMed1996

Distribution of AVT gene expressing neurons in the prosencephalon of japanese quail and chicken.

Detailed anatomical studies about the distribution of arginine-vasotocin (AVT) gene expressing neurons in the avian brain are so far non-existent. Most of the investigations are limited to discrete brain nuclei in the chicken and concern particular experimental conditions. Since no data on AVT gene expression are up to now available in Japanese quail, we report here the distribution of AVT mRNA containing neurons within the prosencephalon of this bird and a comparison with the same system of the chicken. The AVT mRNA containing perikarya were detected with a specific AVT cDNA probe directed toward the distal 3' glycopeptide encoding part of the chicken AVT gene. The specificity of the probe was tested by Northern and Southern blot analysis. The AVT gene expressing neurons showed the same pattern of distribution in both species; however, a larger number of labelled neurons was observed in the chicken by visual inspection of the sections. AVT gene expressing neurons were distributed within the hypothalamus (in the medial and ventral aspects of the rostral preoptic area, in the lateral forebrain bundle, close to the ependyma of the third ventricle and in several periventricular hypothalamic nuclei) and in some extrahypothalamic regions (around the nucleus rotundus, close to the nucleus commissurae pallii and in a region probably corresponding to the nucleus strial terminalis). AVT gene expressing neurons were observed close to the organum septi laterale of the chicken. Taken together, these results confirm the specificity of the employed probe and its suitability for further studies on the modulation of AVT gene expression in quail.

Animals↗
PubMed1991

Projection of the retinal ganglion cells to the tectum differentiated from the prosencephalon.

The alar plate of the prosencephalon differentiates into a tectum-like structure when transplanted into the mesencephalon around the 10-somite stage. Here, we report on the projection pattern of the retinal ganglion cells to the transplants. Optic nerve fibers were labeled with horseradish peroxidase (HRP) and 3H-proline, and the innervation of the optic nerve fibers to the chimeric tectum was analyzed by HRP histochemistry on whole-mounted specimens, by autoradiography and by electron microscopy on embryonic day 16. In the chimeric tectum, the transplant was distinguished from the host by difference in nuclear structure between the quail and the chick cells. It was shown that the transplant had the laminar pattern of the optic tectum when the transplant was integrated into the host mesencephalon. The whole-mount HRP histochemistry showed that the optic nerve fibers extend to the transplants. Autoradiography showed that the distribution pattern of silver grains was similar in both the host and the transplant. These results may indicate that the optic nerve fibers turn to the transplant and terminate on the transplant. Electron microscopy further confirmed that optic nerve fibers ended by making synaptic contacts with the dendrites in the transplant region of the tectum. These results indicate that the transplant with the laminar pattern of the optic tectum is a true tectum receiving input from the eye.

Animals↗
PubMed1999

Fgf8 and Gbx2 induction concomitant with Otx2 repression is correlated with midbrain-hindbrain fate of caudal prosencephalon.

Chick/quail transplantation experiments were performed to analyse possible factors involved in the regionalisation of the midbrain-hindbrain domain. The caudal prosomeres, expressing Otx2, were transplanted at stage HH10 into rostrocaudal levels of the midbrain-hindbrain domain, either straddling the intra-metencephalic constriction (type 1 grafts), or at rostral and medial levels of pro-rhombomere A1 (type 2 and 3 grafts, respectively); thus, in all situations, one border of the graft was in contact with the host Gbx2- and Fgf8-expressing domains. The area containing the graft, recognised by QCPN immunohistochemistry, was first analysed 48 hours after transplantation for Otx2, Gbx2, En2 and Fgf8. Although in all three situations, a large part of the graft maintained Otx2 expression, another part became Otx2 negative and was induced to express Gbx2 and Fgf8. These inductive events occurred exclusively at the interface between the Otx2-positive transplanted domain and the ipsilateral host Gbx2-positive rhombomere 1, creating a new Otx2-Gbx2 boundary within the grafted territory. In type 1 and 2 grafts, the induced Fgf8 domain is in continuity with the host Fgf8 isthmic domain, whereas for type 3 grafts, these two domains are separate. High levels of En2 expression were also induced in the area expressing Gbx2 and Fgf8, and Wnt1 and Pax2 expressions, analysed in type 3 grafts, were induced at the intragraft Otx2-Gbx2 new boundary. Moreover, at later embryonic stages, the graft developed meso-isthmo-cerebellar structures. Thus, gene expressions induced in the grafted prosencephalon not only mimicked the pattern observed in the normal midbrain-hindbrain domain, but is followed by midbrain-hindbrain cytodifferentiation, indicating that not only Fgf8 but also confrontation of Otx2 and Gbx2 may play an essential role during midbrian-hindbrain regionalisation.

Animals↗
PubMed1993

Co-occurrence of substance P and enkephalin-like immunoreactivities in the prosencephalon of two amphibians.

We studied the co-occurrence of substance P-(SP) and leucine (or methionine) enkephalin (ENK)-like immunoreactivities in the prosencephalon of two amphibians: Rana esculenta L. (Anura) and Triturus carnifex Laur. (Urodela) using single and double immunohistochemical methods. The two peptides (SP-ENK) were sometimes found colocalized in neuronal cell bodies and processes. Double-labelled neurons were seen in the nucleus accumbens, lateral septal nucleus, preoptic area, dorsal and ventral hypothalamic nuclei of the frog, whereas in the newt co-occurrence was shown in neurons of the primordium pyriform, corpus striatum, pars ventralis thalami, preoptic area and nucleus infundibularis dorsalis and ventralis. Furthermore, in both amphibians, fibres simultaneously showing SP- and ENK-positivity were observed in the amygdaloid complex, preoptic area and in the posterior hypothalamus, around the infundibulum. Co-occurrence studies in comparative neuroanatomy are relevant, as shown in the present paper regarding the similarities of SP-ENK distribution in the striatopallidal and striatonigral systems of tetrapods.

Animals↗
PubMed1990

Distribution of neuropeptide Y in the prosencephalon of man and cotton-head tamarin (Saguinus oedipus): colocalization with somatostatin in neurons of striatum and amygdala.

The presence, chromatographic properties and localization of neuropeptide Y was demonstrated in postmortem human brain areas of neurologically and neuropsychiatrically normative controls using immunocytochemistry and high performance liquid chromatography combined with radioimmunoassay. NPY-immunoreactivity was found in many regions of the prosencephalon. Numerous perikarya and fibers were present in the neocortex, basal ganglia and limbic-hypothalamic areas. A moderate number of neurons and fibers was observed in the basal forebrain, including the septal complex. A comparative immunohistochemical investigation in perfusion-fixed brains of the old-world ape Saguinus oedipus revealed an almost identical distribution of NPY-immunoreactivity with only minor differences. Colocalization experiments on 1-2 microns thin consecutive paraffin sections revealed a large number of NPY neurons throughout the human neostriatum and amygdaloid complex that were also positive for somatostatin. Our findings indicate that detection of neuropeptides in fresh or fixed post-mortem human tissue by different immunochemical methods may actually reflect the in vivo conditions. In addition, the wide distribution of NPY throughout the human brain and its colocalization with other neurotransmitters suggests a physiological role as neuroactive substance, i.e. neuromodulator in the primate central nervous system.

Amygdala↗
PubMed1986

[Vascularization of the tela choroidea of the prosencephalon of the sheep (Ovis aries)].

The tela choroidea of the prosencephalon in sheep is vascularized by an anterior choroidal artery arising from the rostral branch of the carotid cerebral artery and by a posterior choroidal artery, arising from the caudal cerebral artery, branch of the carotidobasilar system. These two choroidal arteries give off choroidal branches which nourish the capillary networks of the tela. The latter consist of a velar capillary network and of a choroidal capillary network. Together, they drain into choroidal veinules and veins which are tributary of the superficial and of the deep venous systems of the brain.

Animals↗
PubMed1985

[Vascularization of the tela choroidea of the prosencephalon in the cat (Felis domestica)].

The tela choroidea of the prosencephalon in cat is vascularized by an anterior choroidal artery arising from the carotid system and by a posterior choroidal artery arising from the vertebral basilar system. The first essentially supplies the tela and the choroid plexus of the lateral ventricle. The second above all supplies the tela choroidea of the third ventricle. Both, the anterior and posterior choroidal arteries anastomose with their terminal branches. The choroidal branches which arise from these arteries nourish the capillary networks of the tela. These vessels drain into venules and veins which are tributary of the venous circle of the base and of the internal cerebral veins.

Animals↗
PubMed1984

Preliminary report on macroscopic age changes in the human prosencephalon. A stereologic investigation.

The studies here reported were performed on the prosencephalons of 12 human brains between 37 and 86 years of age having no signs of neuropathological alteration. The evaluation was carried out on serial frontal sections with a mean thickness of 5 mm with stereological point counting procedures for volume and surface area. The results were mainly given in relative values since the range of variation is very high and the sample small. The aging process was evaluated with the aid of a linear regression function. The stereological investigation regarding the absolute values of volume and surface area (border face) of the macroscopical brain parts show a high interindividual variability. However, the relative volume of brain parts shows only small variations. Changes during aging could consequently only be revealed with the help of the relative values. The relative volumes and surface areas of the frontal lobe and the prosencephalic ganglia decrease with aging, while the parieto-occipital lobe and the striate cortex increase. However, if we refer these relative increases to the absolute decrease of brain volume, corresponding changes cannot be found in the parieto-occipital lobe until old age. The shrinkage of the frontal lobe, of the centrum semiovale and of the prosencephalic ganglia exceeds 10%. In the grays it is probably accompanied by a loss of neurons. The relative sizes of the surface area do not change significantly during aging with exception of the frontal cortex. The thickness of the cortex remains probably constant. The size of lateral ventricles increases with aging.

Adult↗