bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of spinal neurons and tracts in the zebrafish embryo
Authors: Kuwada John Y. , Bernhardt Robert R. , Nguyen Nguyen 
Published: January 2005

AbstractWe have analyzed pathfinding by growth cones in the spinal cord of the early zebrafish embryo, because it is an extremely simple system. At 18–20 hours of development the spinal cord contains approximately 18 lateral and presumably post‐mitotic cell bodies per hemisegment. Of these 8–11 have projected growth cones by 18 hr of development and fall into five classes of neurons (Bernhardt et al., J. Comp. Neurol, preceding paper), including a set of mechanosensory (RB) neurons, three classes of interneurons (DoLA, ascending commissural, and VeLD), and previously characterized primary motor neurons (Eisen et al., '86: Nature 320:269–271). Of these five classes we analyzed pathfinding by the RB, DoLA, early ascending commissural, and VeLD neurons. These neurons are distinguishable at the earliest stages of axonogenesis based on the location of their somata and the number and initial directionality of their growth cones. In each case they follow stereotyped, cell‐specific pathways to reach their termination sites. Up through larval stages exuberant axons have not been observed.The longitudinal axons of each neuronal class form bundles in the early cord. This apparently occurs because growth cones extend in close association with the longitudinal axons of the same neuronal class. At later stages spatially discrete commissural tracts are found in the cord suggesting that commissural growth cones may follow earlier commissural axons as well.
Sex difference in the bed nucleus of the stria terminalis of the human brain
Authors: Allen Laura S. , Gorski Roger A. 
Published: January 2005

AbstractA quantitative analysis of the volume of the darkly staining region of the posteromedial bed nucleus of the stria terminalis was performed on the brains of 26 age‐matched male and female human subjects. We suggest the term “darkly staining posteromedial” component of the bed nucleus of the stria terminalis (BNST‐dspm) to describe this sexually dimorphic region of the human brain. The volume of the BNST‐dspm was 2.47 times greater in males than in females. This region in humans appears to correspond to an area of the bed nucleus of the stria terminalis in laboratory animals that exhibits volumetric and neurochemical sexual dimorphisms, concentrates gonadal steroids, and is anatomically connected to several other sexually dimorphic nuclei. Furthermore, the bed nucleus of the stria terminalis is involved in sexually dimorphic functions, including aggressive behavior, sexual behavior, and gonadotropin secretion, which are also influenced by gonadal steroids. Therefore, it is possible that in human beings as well, gonadal hormones influence the sexual dimorphism in the BNST‐dspm and that this morphological difference, in part, underlies sexually dimorphic function.
Ventral respiratory group projections to phrenic motoneurons: Electron microscopic evidence for monosynaptic connections
Authors: Ellenberger Howard H. , Feldman Jack L. , Goshgarian Harry G. 
Published: January 2005

AbstractThe hypothesis that excitatory drive is transmitted monosynaptically from bulbospinal medullary respiratory neurons to spinal respiratory motoneurons was tested by an ultrastructural analysis of the phrenic motoneuronal pool in the rat. Combined anterograde labeling of the principal inspiratory bulbospinal neuron population (ventral respiratory group) and retrograde labeling of the phrenic motoneuron pool demonstrated the presence of labeled synaptic profiles, indicating that at least some bulbospinal inspiratory neurons make monosynaptic contacts with phrenic motoneurons. The synaptic boutons of ventral respiratory group neurons that were labeled in the phrenic nucleus had asymmetrical membrane densities at sites of synaptic contact with labeled phrenic somal or dendritic profiles, supporting the notion that this bulbospinal pathway has excitatory contacts with phrenic motoneurons. The morphological types of labeled boutons included three of the eight previously identified bouton types in the phrenic nucleus (Goshgarian and Rafols: Journal of Neurocytology 13:85–109, 1984), including the “S”‐terminal, the “NFs”‐terminal, and the “F”‐terminal. There was no conclusive evidence of labeled double synapses, indicating that this type of synaptic contact is not common in the intact bulbospinal pathway.
Two classes of Limulus ventral photoreceptors
Authors: Herman Karen G. 
Published: January 2005

AbstractVentral photoreceptors of the horseshoe crab, Limulus polyphemus, have been important in the study of visual transduction, due to their large size and hardiness in vitro. This study shows that there are two classes of ventral photoreceptors that can be distinguished on the basis of differences in cellular and nuclear dimensions, soma and rhabdom morphology, and axon size. Large photoreceptors, which have been the subject of many physiological studies, have an extensive superficial rhabdom, a nuclear diameter of 20–24 μm, and measure 100–150 μm in length. In contrast, small photoreceptors measure 45–65 μm in length and have a nucleus 13–16 μm across. Small photoreceptors are found singly or in association with large photoreceptors. The rhabdom of isolated small photoreceptors is surrounded by a calyx originating from the soma, so that it appears to be located internally. The rhabdomeral lobe of small photoreceptors associated with large photoreceptors characteristically is divided into several segments, each of which invaginates the rhabdomeral lobe of the adjacent large photoreceptor. The entire external rhabdom of the associated small photoreceptor abuts the rhabdom of the large photoreceptor. Morphometric analysis of the ventral nerves shows that there are two size classes of photoreceptor axons, corresponding to the two classes of photoreceptors. The numbers of axons in each size class are nearly equal. Unlike the ventral eye, none of the other eyes of Limulus have been reported to have more than one morphological class of photoreceptor. Functional differences between the two classes of ventral photoreceptors are suggested by experiments, reported in the accompanying paper (Herman (1991), J. Comp. Neurol. 303:11–21), showing that the large photoreceptors exhibit light‐stimulated rhabdom turnover while the small ones do not.
The cells of origin of the spinohypothalamic tract in cats
Authors: Katter James T. , Burstein Rami , Giesler Glenn J. 
Published: January 2005

AbstractVarious cutaneous and visceral stimuli alter the discharge rates of neurons in the hypothalamus. Changes in the activity of hypothalamic neurons are thought to play important roles in eliciting neuroendocrine, autonomic, and affective responses to somatosensory and visceral stimuli. Information from peripheral structures has been considered generally to reach the hypothalamus via multisynaptic ascending pathways. Recently, a direct projection from the spinal cord to the hypothalamus was demonstrated in rats. The goal of this study was to determine whether a similar projection exists in cats. Either wheat germ agglutinin conjugated to horseradish peroxidase, a mixture of this tracer and the B subunit of cholera toxin conjugated to horseradish peroxidase, or fast blue was injected into the hypothalamus of cats. Injections were centered in the hypothalamus in seven cats and did not spread to the thalamus, zona incerta or midbrain. After these injections, retrogradely labeled neurons were observed bilaterally in each of the 17 spinal segments that were examined. A total of approximately 400–500 labeled neurons was observed in alternate sections through these segments in the most effective cases. Roughly 70% of the labeled neurons were located contralaterally. Labeled neurons were found predominantly in the deep dorsal horn, the intermediate zone/ventral horn and in the area surrounding the central canal. A few were also noted in the superficial dorsal horn. The first and second sacral segments contained the largest numbers of retrogradely labeled neurons in the spinal cord.The number of spinohypothalamic tract neurons observed in this study in cats was roughly an order of magnitude smaller than that previously reported for rats. This finding suggested either that the spinohypothalamic tract is relatively small in cats or that our tracing techniques did not label many spinohypothalamic tract neurons in cats. To test the sensitivity of one of our tracing techniques, control injections of wheat germ agglutinin conjugated to horseradish peroxidase that filled the ventrobasal thalamus were made in two cats. In both cases, thousands of spinal cord neurons were labeled.In summary, our results indicate that a spinohypothalamic tract exists in cats. However, our findings also suggest that the total number of spinohypothalamic tract neurons in cats may be an order of magnitude smaller than it is in rats.
Galanin mRNA in the nucleus basalis of Meynert complex of baboons and humans
Authors: Walker Lary C. , Rance Naomi E. , Price Donald L. , Young W. Scott 
Published: January 2005

AbstractGalanin, a 29‐amino acid peptide, has been shown by immunocytochemistry to occur in most large acetylcholinergic neurons of the complex that includes the nucleus basalis of Meynert and the nucleus of the diagonal band of Broca in nonhuman primates. In contrast, several studies have reported that most large neurons of the human nucleus basalis of Meynert complex appear to lack galanin immunoreactivity. We investigated this apparent species‐difference by hybridization histochemistry for galanin messenger ribonucleic acid (mRNA) in humans and baboons. The results confirm previous immunocytochemical data; very few large neurons of the nucleus basalis of Meynert complex in humans contained detectable galanin messenger RNA, whereas most such cells in baboons were labeled by the oligodeoxynucleotide probe. The few labeled neurons in humans were primarily medial or ventral to the main body of the nucleus basalis of Meynert and corresponded in location to a minor population of relatively intensely labeled cells in baboons. These findings indicate that the indetectability of immunoreactive galanin in most cells of the nucleus basalis of Meynert complex in humans is due to a paucity or an absence of galanin messenger RNA and not to differences in posttranslational processing or transport of the peptide. Inasmuch as the probe labeled neurons in several other nuclei of both species, it is unlikely that differences in galanin messenger RNA sequences underlie the species‐related disparity in hybridization in the nucleus basalis of Meynert complex. The indetectability of galanin messenger RNA in most cells of the human nucleus basalis of Meynert complex indicates that the expression of the galanin gene is regulated by as yet unidentified influences that differ in human and nonhuman primates. The varying phenotypes of galanin in primates suggest potentially important species‐differences in the function of galanin in neurons of the nucleus basalis of Meynert complex.
Distribution and morphology of area 17 neurons that project to the cat's extrastriate cortex
Authors: Einstein Gillian , Fitzpatrick David 
Published: January 2005

AbstractWe used intracellular dye injections in lightly fixed cortical slices to examine the distribution and morphology of area 17 neurons that project to extrastriate cortex. Both the projection to the medial bank of the posterior lateral suprasylvian sulcus (PMLS) and the projection to area 18 arise from a number of different morphological types distributed throughout layers 2–6. The majority are found in the superficial layers and include large, medium, and small pyramidal neurons. Some are also found in the deep layers and they include very large, pyramidal neurons as well as some heretofore undescribed, fusiform neurons. The projection to area 18 contains two types not found in the projection to PMLS: Spinous stellate neurons in layer 4 and inverted pyramidal neurons in layer 3. Finding that a variety of morphological types contribute projections to a single cortical area raises the possibility that corticocortical projections, like retinogeniculate and geniculocortical projections, comprise multiple parallel pathways with different physiological properties and patterns of termination. Finding that the projection to area 18 contains morphological types that do not project to PMLS indicates that the projections from area 17 are likely to contribute to the functional specialization of extrastriate visual areas.
Synapses made by axons of callosal projection neurons in mouse somatosensory cortex: Emphasis on intrinsic connections
Authors: White Edward L. , Czeiger David 
Published: January 2005

AbstractThis is one of a series of papers aimed at identifying the synaptic output patterns of the local and distant projections of subgroups of pyramidal neurons. The subgroups are defined by the target site to which their main axon projects. Pyramidal neurons in areas 1 and 40 of mouse cerebral cortex were labeled by the retrograde transport of horseradish peroxidase (HRP) transported from severed callosal axons in the contralateral hemisphere. Terminals of the local axon collaterals of these neurons (“intrinsic” terminals) were identified in somatosensory areas 1 and 40, and their distribution and synaptic connectivity were examined. Also examined were the synaptic connections of “extrinsic” callosal axon terminals labeled by lesion induced degeneration consequent to the severing of callosal fibers. A post‐lesion survival time of 3 days was chosen because by this time the extrinsic terminals were all degenerating, whereas the intrinsic terminals were labeled by HRP.Both intrinsic and extrinsic callosal axon terminals occurred in all layers of the cortex where they formed only asymmetrical synapses. Layers II and III contained the highest concentrations of both types of callosal axon terminal. Analyses of serial thin sections through layers II and III in both areas 1 and 40 yielded similar results: 97% of the extrinsic (277 total sample) and of the intrinsic (1215 total sample) callosal axon terminals synapsed onto dendritic spines, likely those of pyramidal neurons; the remainder synapsed onto dendritic shafts of both spiny and nonspiny neurons. Thus the synaptic output patterns of intrinsic vs. extrinsic callosal axon terminals are strikingly similar. Moreover, the high proportion of axospinous synapses formed by both types of terminal contrasts with the proportion of asymmetrical, axospinous synapses that occur in the surrounding neuropil where only about 80% of the asymmetrical synapses are onto spines. This result is in accord with previous quantitative studies of the synaptic connectivities of both extrinsic and intrinsic axonal pathways in the cortex (White and Keller, 1989: Cortical Circuits: Boston: Birkhauser): in all instances, axonal pathways are highly selective for the types of elements with which they synapse.
Factors determining the migration of astrocytes into the developing retina: Migration does not depend on intact axons or patent vessels
Authors: Chan‐Ling Tailoi , Stone Jonathan 
Published: January 2005

AbstractAstrocytes migrate into the cat retina from the optic nerve, beginning from embryonic day (E) 52. Once they have entered the retina they concentrate along major axon bundles and fail to enter regions of the retina with high densities of neurones, in particular the area centralis region of the ganglion cell layer. These nonuniformities appear as the astrocytes spread over the retina during development, and in this study we have examined factors that might control their spread. First we examined astrocytes in a retina in which the axon bundles had degenerated following an optic nerve lesion at birth. The area over which astrocytes had spread was normal, suggesting that their spread does not depend on the presence of intact axons. Second, we noted that, despite the degeneration of all ganglion cells following the nerve lesion, astrocytes still did not spread over the area centralis. Their spread is apparently not inhibited by concentrations of neurones. Third, we examined astrocytes in retinas of animals raised in an atmosphere containing 70–80% oxygen, which prevents the formation of retinal vessels. Again, the area over which the astrocytes had spread was normal, suggesting that their spread does not depend on the presence of patent blood vessels. These negative findings led us to compare the distribution of spindle cells (precursors of retinal vasculature) and astrocytes in the cat during development. The close correspondence in their topographical distribution and the earlier spread of the spindle cells lead us to suggest that spindle cells provide a basal lamina component that may guide the migration of astrocytes.
Continuous growth of the motor system in the axolotl
Authors: Holder Nigel , Clarke J. D. W. , Stephens Nigel , Wilson Stephen W. , Orsi Claudia , Bloomer Timothy , Tonge D. A. 
Published: January 2005

AbstractDuring growth of the axolotl, motor neurons, and muscle fibres are added to the motor system. By double labelling neurons with tritiated thymidine and retrogradely transported HRP, we show that some motor neurons are born at postembryonic stages. Further analysis of motor neurons with the aid of HRP reveals this population of newly, born cells relatively frequently in small (5–7 cm long) axolotls, but only rarely in large (7–13 cm long) axolotls. Evidence is presented that suggests that these immature cells are in the process of migrating from close to the ependyma out to the ventral horn. HRP transport also reveals growth cones of advancing axons within spinal nerves in animals up to 6 cm in length. Cell counts by light and electron microscopic methods show that muscle fibres are generated throughout larval life in the iliotibialis, a typical limb muscle. This analysis provides data consistent with the notion that new muscle fibres are added from a localised growth zone situated at the superficial edge of the muscle. These results are discussed in terms of the correlation between continuous growth of the motor system and the ability of the axolotl to functionally repair lesions to the peripheral nervous system.
Prefrontal cortical projections to the cholinergic neurons in the basal forebrain
Authors: Gaykema Ronald P. A. , Van Weeghel Rob , Hersh Louis B. , Luiten Paul G. M. 
Published: January 2005

AbstractThe prefrontal cortex (PFC) projections to the basal forebrain cholinergic cell groups in the medial septum (MS), vertical and horizontal limbs of the diagonal band of Broca (VDB and HDB), and the magnocellular basal nucleus (MBN) in the rat were investigated by anterograde transport of Phaseolus vulgaris leuco‐agglutinin (PHA‐L) combined with acetylcholinesterase (AChE) histochemistry or choline acetyltransferase (ChAT) immunocytochemistry. The experiments revealed rich PHA‐L‐labeled projections to discrete parts of the basal forebrain cholinergic system (BFChS) essentially originating from all prefrontal areas investigated. The PFC afferents to the BFChS display a topographic organization, such that medial prefrontal areas project to the MS, VDB, and the medial part of the HDB, whereas the orbital and agranular insular areas predominantly innervate the HDB and MBN, respectively. Since the recurrent BFChS projection to the prefrontal cortex is arranged according to a similar topography, the relationship between the BFChS and the prefrontal cortex is characterized by reciprocal connections. Furthermore, tracer injections in the PFC resulted in anterograde labeling of numerous “en passant” and terminal boutons apposing perikarya and proximal dendrites of neurons in the basal forebrain, which were stained for the cholinergic marker enzymes. These results indicate that prefrontal cortical afferents make direct synaptic contacts upon the cholinergic neurons in the basal forebrain, although further analysis at the electron microscopic level will be needed to provide conclusive evidence.
Ontogeny of the F8Famide‐like (morphine‐modulating) peptides in the central nervous system of rats
Authors: Kivipelto L. , Panula P. , Rubenstein J. , Yang H.‐Y. T. 
Published: January 2005

AbstractFLFQPQRF‐NH2 (F8Famide; FMRFamide‐like peptide; morphine‐modulating peptide) is a peptide isolated from bovine brain. It has some opiate analgesia modulating effects. In an adult rat central nervous system, F8Famide‐like immunoreactivity is found in high concentrations in the posterior pituitary, hypothalamus, pons, medulla, and dorsal spinal cord.By using immunohistochemistry and radioimmunoassay, we studied the development of the F8Famide‐immunoreactive system in the rat central nervous system during the ontogeny. F8Famide‐immoreactive fibers and terminals first appeared in the median eminence on the twentieth embryonal day. Postnatally the F8Famide‐immunoreactive system developed rapidly both in the brain and spinal cord, the immunoreactive structures having an adultlike distribution by the age of 1 week. A transient increase of the F8Famide‐immunoreactive material was observed during the third and fourth postnatal weeks. By the age of 4 weeks, the F8Famide‐containing neuronal system was adultlike both in distribution and quantity.The results suggest that the F8Famide‐like peptides may act as neurotransmitters or neuromodulators from the time of their appearance in the brain and spinal cord. The early appearance and the distribution of the F8Famide‐like immunoreactivity suggest that these peptides may participate, in addition to nociceptive mechanisms, in the regulation of blood pressure, feeding behaviour, and endocrine functions.
Patterns of synaptic input on corticocortical and corticothalamic cells in the cat visual cortex. II. The axon initial segment
Authors: Fariñas Isabel , DeFelipe Javier 
Published: January 2005

AbstractIn the present study we examined the synaptology of the axon initial segments (AISs) of three populations of retrogradely labeled pyramidal cells: callosal, corticothalamic, and ipsilateral corticocortical projecting cells. The cells were labeled by horseradish peroxidase injected into the contralateral visual cortex, the ipsilateral lateral geniculate nucleus, or area 19 of the ipsilateral hemisphere. The AISs of these cells were completely reconstructed from tracings of serial electron micrographs and the number and type of synapses ending on them determined, These data were compared with that described in the companion paper (Fariñas and DeFelipe, J Comp Neurol 1991; 304:53–69), in which the ultrastructure and synaptology of the somata of callosal and corticothalamic cells was investigated. Together, these data permit comparisons to be made between the somatic and axonic innervation of the same cells.Our results show that each population of efferent cells examined received a characteristic and rather homogeneous number (in comparison with the number of axosomatic synapses) of axoaxonic synapses: 16 to 23 for AISs of callosal cells, 22 to 28 for ipsilateral corticocortical cells, and 1 to 5 for corticothalamic cells. Since most axoaxonic synapses are likely to be GABAergic, it is concluded that each population of pyramidal cells receives a distinct GABAergic inhibitory synaptic profile.