Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Rhombencephalon”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1988

Tyrosine hydroxylase and serotonin containing cells in embryonic rat rhombencephalon: a whole-mount immunocytochemical study.

Rhombencephala from rat embryos were processed as whole-mounts for immunocytochemical detection of monoaminergic cell populations, using antibodies to tyrosine hydroxylase (TH) and serotonin (5-HT). Specific advantages of the whole-mount technique over the classical serial-section method were that even isolated immunoreactive (IR) cells could be detected easily, and three-dimensional relationships could be ascertained without the need for serial reconstruction. Embryos between embryonic days (E) 12 and 16 (the day following nocturnal mating being considered as E1) were used in this study. Both TH and 5-HT immunoreactivities were already detectable at E12, even in the smallest embryos (crown-rump length: 6 mm), but there was a striking difference in the number and regional distribution of these two types of IR cells. TH was expressed in several cell groups located in the rostral rhombencephalon (the presumed anlage of the A4-7 complex) as well as in the caudal rhombencephalon (the presumed anlagen of groups A1-2 and C1-3), whereas 5-HT was expressed in very few cells located near the rostral border of the rhombencephalon (presumed anlage of the B4-9 complex). Although the three-dimensional distribution of the TH-IR cell groups underwent some modifications during the period studied, its general pattern remained relatively stable after E12. This contrasted with the sequential appearance of the 5-HT-IR cell groups and their spatial transformations during this period. Using the rhombencephalic isthmus as a landmark, we found that conspicuous 5-HT-IR fibre bundles penetrated into the mesencephalon from E13 onwards, but that the 5-HT IR cell bodies were exclusively located caudal to the borderline between the mesencephalon and the rhombencephalon (the rhombencephalic isthmus). We therefore suggest the term "rostral rhombencephalic raphe nuclei" for the rostral 5-HT cell groups instead of "mesencephalic raphe nuclei," which is a misnomer. Close spatial association between TH and 5-HT-IR elements was observed mainly in the caudal rhombencephalon, where 5-HT-IR fibres coursed through an area containing numerous TH-IR cell bodies (the presumed anlagen of groups A1-2 and C1-3).

Animals↗
PubMed1987

Development of the precerebellar nuclei in the rat: I. The precerebellar neuroepithelium of the rhombencephalon.

Short-survival thymidine radiograms from rat embryos aged 13-19 days were analyzed to delineate the precerebellar neuroepithelium of the rhombencephalon. The original definition of the term "rhombencephalon" was modified to refer only to the unique dorsal portion (surface plate) of the medulla and pons where the neural groove fails to fuse and, instead, the medullary velum covers the rhomboid lumen of the fourth ventricle. Initially, the neuroepithelial tissue of the rhombencephalon consists of a pair of rostral and caudal bridgeheads: the former the primary neuroepithelium of the cerebellum and the latter the primary neuroepithelium of the octavo-precerebellar system. The spatial relationship between the cerebellar and precerebellar neuroepithelia soon changes as a result of ongoing morphogenetic events, such that the cerebellar primordium assumes a dorsal position and the precerebellar primordium a ventral position, and the distance between the two decreases. Concurrently the tela choroidea invaginates into the fourth ventricle and a secondary precerebellar neuroepithelium develops. The rostral portion of the secondary precerebellar neuroepithelium grows forward along the choroid plexus and forms the medial recess of the anterior fourth ventricle, while its caudal portion grows in the opposite direction beneath the medullary velum and forms the rostral wall of the posterior fourth ventricle. Evidence will be presented in the succeeding papers that the primary precerebellar neuroepithelium first generates the neurons of the inferior olive that migrate by a circumferential intramural (parenchymal) route to their destination. Next, the neurons of the lateral reticular and external cuneate nuclei are generated. These migrate by a posterior extramural (superficial) route and settle contralaterally. Subsequently, the primary precerebellar neuroepithelium produces the neurons of the nucleus reticularis tegmenti pontis and these form the anterior extramural migratory stream and settle ipsilaterally. Finally, the secondary precerebellar neuroepithelium produces the latest generated neurons of the basal pontine gray that follow the anterior extramural stream and settle ipsilaterally.

Animals↗
PubMed1995

[Comparative studies of rhombencephalon vascularization in rabbit and man in light of anatomic and microangiographic studies].

A comparative study of a microvascularization of the rhombencephalon, especially pre- and capillary system, in rabbits and in humans was performed. It was intended to find out whether there were any similarities and differences in rhombencephalon microvascularization of a rabbit and man. The study was carried out on 75 (50--female, 25--male) mixed-race rabbits aged 4 months, as well as on 30 (15--females, 10--males) human brains that had been dissected free from cadavers, aged from 20 up to 70 years. Angiography of sections of the rhombencephalon in rabbits and cadavers was performed. The vessels were investigated after the introduction of Micropaque contrast medium, under controlled pressure, into an investigated vessel. Intravital injection of the contrast into rabbit's vessel was beneficial for the experiment. Radiography of intact brains as well as sections of the frontal plane was accomplished. Large arterial vessels were measured, with the results being subjected to statistical analysis (Table 1-2, Fig. 1-7). Microvascularization of the medulla oblongata and of the pons in rabbits were similar to those in its human counterparts, whereas the vascular system of the cerebellum was different. The results of micrographic studies were not always the same as described by Bochenek et al. The anatomical forms that had not been previously described were noted: para--medial arteries to the medulla oblongata and the pons; lateral arteries to the medulla oblongata and the pons; posterior arteries to the medulla oblongata; branches of the upper artery of the cerebellum branching and the simple ones with few lateral branches. The central or medial artery that follows the central sulcus was separate.

Adult↗
PubMed1990

The human rhombencephalon at the end of the embryonic period proper.

The human rhombencephalon at 8 postovulatory weeks (stage 23) is described and illustrated for the first time with the aid of silver-impregnated sections and graphic reconstructions. The motor and sensory trigeminal nuclei were among those studied, and the latter was found to be almost contiguous to the dentate nucleus. Fibers to the principal sensory nucleus join the mesencephalic trigeminal tract, which also seems to be connected with the motor fibers. Fine fibers from the sensory root join the tractus solitarius, which appears to receive connections from the facial, glossopharyngeal, and vagal nerves. Main and accessory abducent nuclei are evident. A part (the Kappenkern des Facialisknies) of the nucleus funiculi teretis is particularly prominent. The presence of the pyramidal decussation during the embryonic period is noted for the first time. The arrangement of nuclei and tracts at 8 weeks is shown to be closely similar to that present in the newborn, and it is likely that the rapid growth of the rhombencephalon during the embryonic period proper is associated with correspondingly early functional activity.

Cell Movement↗
PubMed1992

Glial fibrillary acidic protein and vimentin immunohistochemistry in the posterior rhombencephalon of the Iberian barb (Barbus comiza).

The gustatory centers (vagal lobes and facial lobe) and the tegment of the posterior rhombencephalon of the Iberian barb (Barbus comiza) have been studied using anti-glial fibrillary acidic protein (anti-GFAP) and anti-vimentin immunohistochemical techniques. GFAP immunoreactivity was found in the tegment and in a part of the vagal lobes while vimentin immunoreactivity was located in the tegment. Two immunopositive cell types were found: ependymocytes and radial astrocytes. Since the distribution of GFAP in the barb rhombencephalon corresponds with zones previously described as cholinergic, the GFAP-immunopositive radial astrocytes might be involved in acetylcholine metabolism.

Animals↗
PubMed1995

A concept of the development of the mammalian rhombencephalon based on physical rotational forces.

The premammalian forms do not show the metencephalic and myelencephalic divisions of the rhombencephalon. The seven longitudinal grey columns, in relation to the seven nerve components are direct cranial uninterrupted continuations from the spinal cord. The isthmus rhombencephali is a tubular structure. The phylogenetically ancient ependyma rich in tanycytes lines the fourth ventricle. The neural canal does not open into the subarachnoid space and the ependyma never becomes directly continuous with the pia mater. On the other hand, in mammals, the rhombencephalon is divided into the metencephalon and myelencephalon. The seven longitudinal grey columns get fragmented and their cell masses undergo migrations. The isthmus loses its tubular nature and undergoes modifications. The fourth ventricle opens into the subarachnoid space through three openings. The phylogenetically ancient ependyma is retained as a continuous structure only along the inferolateral angle of the fourth ventricle. At the openings of the lateral recesses, the ependyma becomes directly continuous with the pia, a neural crest derivative. The oval bundle, the corpus trapezoideum and the myelencephalic component of the nuclei pontis show extensive migrations. The above phenomena can be explained by physical rotation forces and not merely by migrations.

Animals↗
PubMed1976

Comparative anatomy of the locus coeruleus. II. Organization and projection of the catecholamine containing neurons in the upper rhombencephalon of the frog, Rana catesbiana.

The organization and projection of the catecholamine (CA) containing neurons in the upper rhombencephalon were experimentally investigated with histofluorescence method in the brain of the bullfrog, Rana catesbiana. A small number of catecholamine containing neurons are located in the upper rhombencephalon. These neurons do not send ascending fibers to contribute CA projection to the forebrain, but give rise to relatively short axons to innervate the cerebellum and neighbouring reticular formation. Judging from their anatomical aspects, it seems that the structure homologous to the mammalian locus coeruleus is not present in the amphibian brain.

Animals↗
PubMed1986

Volumetric development of the fetal telencephalon, cerebral cortex, diencephalon, and rhombencephalon including the cerebellum in man.

Fresh volumes of the human telencephalon, cerebral cortex, diencephalon, and of the rhombencephalon including cerebellum were determined in a series of 10 normal specimens ranging in age from 63 to 176 days after conception. The volumetric growth of these parts shows a nonlinear dependence on age with a smaller increase during the 3d ontogenetic month and a stronger increase from the 4th month on. These data were analyzed together with previous measurements of 28 brains taken from the Yakovlev Collection in Washington, D.C., and the Vogt Collection in Düsseldorf. These brains range in age from 137 to 22,900 days after conception. These samples were reproduced in a model using sigmoid logistic functions. The entire brain and all analyzed parts show a monotonous growth. The individual regions develop heterochronously. The diencephalon is the first part to reach its ideal volume, with a main growth spurt between 100 and 420 days after conception. The rhombencephalon including the cerebellum is the last, with its main growth spurt between 240 and 650 days after conception. The growth of the entire brain is determined to a great extent by that of the telencephalon, having a main growth spurt between 175 and 580 days after conception. The prenatal growth is described separately with the asymmetric sigmoid function according to Gompertz. This yields a better approximation of the data collected from the early prenatal period.

Cerebellum↗
PubMed1991

Population-specific modulation of 5-HT expression in cultures of embryonic rat rhombencephalon.

This study aimed at analyzing the regulation of in vitro serotonin expression by neurons taken from different regions of the embryonic rat rhombencephalon. We studied the influence of co-culture with alarplate tissue using immunocytochemical and biochemical methods. Computer-assisted densitometry was used to estimate the co-culture effects on the serotonin content of the cell bodies. The more dynamic aspects of serotonin expression, such as synthesis and release, were studied by measuring (3H)serotonin newly synthesized from (3H)tryptophan. The density of the immunostaining was significantly decreased in B1,B2 cells by co-culture with both caudal and rostral alar-plate tissue. For B4-B9 cells, only co-culture with rostral alar-plate tissue produced a significant decrease. The de novo synthesis of serotonin was significantly decreased in B1,B2 neurons co-cultured with caudal alar-plate tissue only. Once again, the B4-B9 cells proved to be less influenced by the experimental conditions, as co-culture with both types of alar-plate tissue produced no significant effect. We concluded that the in vitro expression of serotonin can be modulated by environmental factors, but the relative influence of these factors is very different in rostral versus caudal serotonin expressing cell populations.

Animals↗
PubMed1989

Distribution of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes in the rat brain. II. Mesencephalon, rhombencephalon and spinal cord.

The topographical mapping of glial fibrillary acidic protein (GFAP)-immunoreactivity was performed in coronal serial sections of the rat mesencephalon, rhombencephalon and spinal cord. Relative to a background of poor or moderate overall staining of the mesencephalon, the interpeduncular nucleus, substantia nigra and the periaqueductal grey matter were prominent by their intense GFAP-immunoreactivity. The pons and particularly the medulla contained more GFAP-labelled elements compared with the mesencephalon. The spinal trigeminal nucleus and Rolando substance were distinguished by their intense staining. Large fibre tracts were usually poor in immunoreactive GFAP. In a concluding discussion, findings relevant to the GFAP-mapping of the whole rat CNS are evaluated with regard to possible reasons underlying the observed differential distribution of GFAP-immunoreactivity.

Animals↗
PubMed1993

Effects of experimentally induced hyperammonemia on glial fibrillary acidic protein (GFAP) in the rhombencephalon of goldfish (Carassius auratus L.).

This experimental study was made to know the effect of hyperammonemia on glial fibrillary acidic protein (GFAP) in the glial cells of posterior rhombencephalon in the goldfish (Carassius auratus L.). Hyperammonemia was induced by elevating the ammonia concentration in the tank water to 0.88 mM with ammonium chloride; the ammonia level in the control tank water was < 0.1 mM. The GFAP levels were measured at 8, 16, 30, 60, 90 and 120 days. GFAP was quantified with a digital analysis system and a transient heterogeneous decrease of GFAP was observed. Hyperammonemia mostly affected GFAP in the astrocyte processes associated with cholinergic pathways. An explanation for the adaptive response to hyperammonemia by fish astrocytes is suggested.

Ammonia↗
PubMed1997

Morphological and morphometric analysis of serotonin-containing neurons in primary dissociated cultures of human rhombencephalon: a study of development.

Primary dissociated cultures of rhombencephalon were prepared from 5-9-week-old human fetuses. Half of some cultures were treated by two non-competitive N-methyl-D-aspartate antagonists, namely 1-(2-thienyl)cyclohexylpiperidine (TCP) and cis-Pip/Mel-[1-(2-thienyl)-2-methyl-cyclohexyl]piperidine (GK11) in negative enantiomeric form, which enhance the survival of human fetal central nervous system cells in culture. At different days in vitro, the treated and the control cultures were processed for immunocytochemical detection of serotonin-containing neurons which were studied by morphological and morphometric analysis. Statistical analysis showed that the surface of the stained neurons increased as a function of two parameters of time, the gestational age of the cells and the duration of the cultures. The complexity of the shape of the serotonin neurons characterized by the shape factor, the number of bifurcations and the morphological feature (bipolar or multipolar) was found to increase with the gestational age. It appears that the in vitro development of the embryonic cells which represents stages of maturation and differentiation can be specifically evaluated. Such an analysis of fetal central nervous system cells improves the knowledge of factors important in grafting experiments. We verified that the two drugs do not appreciably alter the in vitro development of the treated cells; thus they may be considered as promising drugs for human neuroprotection.

Cell Differentiation↗
PubMed1988

Fetal rhombencephalon: normal US findings.

Using ultrasound (US), the authors examined 25 embryos that were 8-10 menstrual weeks old for gestational age and the presence of a small cystic structure (3-4 mm) in the posterior aspect of the cranium. This structure was seen in all embryos. The US images of an in vitro embryo at 8 weeks menstrual age were also evaluated for anatomic correlation. Analysis of these US images determined that the cystic structure was the open rhombencephalon or hindbrain. Follow-up US studies or postpartum clinical examinations of the 25 in utero embryos demonstrated no abnormal posterior cranial cystic structures or neurologic deficits. This first-trimester structure should be considered a normal finding, since it develops into the normally proportioned fourth ventricle after the 11th menstrual week.

Female↗
PubMed1997

[Genetic control of rhombencephalon development by Hox genes studied in bird embryo by the quail-chick chimera method].

The rhombencephalic neural tube is transiently segmented along the anteroposterior axis into 8 rhombomeres. Each rhombomere, as well as its derived neural crest cells, is characterized by the expression of a specific set of Hox genes which constitute its Hox code. This code is supposed to define the morphogenetic program of these cells according to their position. We took advantage of the quail/chick chimera system to study the regulation of Hox gene expression in neural tube and neural crest cells. We have therefore ectopically transplanted the presumptive territories of the future rhombomeres and studied the evolution of their Hox code. We evidence in the posterior rhombencephalon and the spinal cord a posteriorising signal able to induce Hox gene expression, to repress anterior molecular markers and to control the subsequent development of the neural tube. This signal is conveyed horizontally in the plane of the neuroepithelium and vertically from the mesoderm to the ectoderm. The anteroposterior identity of the neural crest cells seem independent from this inducer after formation of the neural fold.

Animals↗
PubMed1983

Retrograde HRP identification of neurons in the rhombencephalon and spinal cord of the rat that project to the dorsal mesencephalon.

Neurons in the rhombencephalon and spinal cord of the rat that project to the dorsal midbrain were identified using the HRP retrograde neuroanatomical tracing method. Retrogradely labeled neurons were most numerous in the reticular formation, specifically in nucleus pontis oralis, caudalis, and gigantocellularis and in the sensory trigeminal complex. Neurons that project were also found in certain raphe nuclei, the parabrachial nuclei, the deep cerebellar nuclei, the vestibular cochlear complex, and the spinal cord. The diverse distribution of neurons that project to the midbrain is understandable in the context of the known diverse functions of the region, which include a role in sexual and other behaviors, nociception, and various autonomic functions.

Animals↗
PubMed1981

Topographic atlas of somatostatin-containing neuron system in the avian brain in relation to catecholamine-containing neuron system. II. Mesencephalon, rhombencephalon, and spinal cord.

With the indirect immunofluorescence technique of Coon's and collaborators, overall distribution of the somatostatin (SRIF)-positive neurons system in the avian lower brain stem was explored. Numerous cell somata containing SRIF were identified in the interpeduncular nucleus and substantia grisea centralis (GCT) at the level of the nucleus nervi trochlearis. Furthermore, a moderate number of SRIF-positive neurons were seen in the tectum opticum, nucleus tractus solitarii, and spinal cord. Scattered labeled cells were noticed in the rhombencephalon. A dense network of SRIF-positive fibers was distributed widely in the lower brain stem of birds. Their locations corresponded in many cases to the areas where SRIF-positive neurons were found. The present study also presents the distribution of the catecholamine (CA) neuron system in the avian lower brain stem. Possible interactions between SRIF and CA neurons systems are briefly discussed.

Animals↗
PubMed1981

Transitory subependymal cysts in the developing rat rhombencephalon.

A bilaterally symmetrical cystic cavity is situated in the subependymal neuropil of the rostral rhombencephalon of the rat during the perinatal period of ontogeny. These cysts are formed by the confluence of enlarged extracellular spaces in this region between E18 and E20. The cysts are present for about 2 weeks but disappear on about P15 without trace. They have a maximal volume of about 0.004 to 0.006 mm3 on P2, with a rostrocaudal extension of about 200 microm. Their shape is characterized by a medial convexity and a lateral concavity, and they have their maximal circumference at about the middle of the rostrocaudal axis. The caudal portion is juxtaposed to the subependyma, while the rostral part lies in the neuropil of the presumptive griseum centrale pontis. In the lumen and the wall of the cysts are found numerous macrophages, glioblasts and some degenerating axons and dendrites. The significance of these cysts in the context of morphogenesis and the origin of the numerous macrophages within them are both unresolved.

Animals↗
PubMed1980

Familial brain tumors: rhombencephalon-astrocytoma grade I in father and son.

This report presents a clinico-pathologic study of low-grade astrocytoma in father and son whose relatives had multiple sclerosis and Cockayne syndrome. The corresponding location within the rhombencephalon and the coincidence of tumor type probably imply that an endogenous genetic factor has influenced the astrocyte cell line.

Adolescent↗