bluuebunny/crossref_metadata_2025_split huggingface dataset:
Timing and positioning of reopening of the occluded spinal neurocele in the chick embryo
Authors: Schoenwolf Gary C. , Desmond Mary E. 
Published: January 2005

AbstractOcclusion and reopening of the spinal neurocele are important morphogenetic events occurring during rapid brain enlargement in amphibians, birds, and mammals. The purpose of the present study, a companion to a previous one on occlusion, is to examine reopening. We determined when reopening occurred and at what frequency, whether it occurred suddenly or gradually, the extents of the neurocele that were patent at particular stages of reopening, and the morphological pattern of reopening. Reopening begins at stages 14 + to 15 and is virtually complete at stages 16–17. Thus, reopening of the spinal neurocele occurs suddenly and occlusion is a relatively short‐lived developmental event. Because rapid brain enlargement still occurs after reopening, occlusion probably functions principally in the initial phases of enlargement prior to closure of the posterior neuropore. Further studies on the mechanisms of occlusion and reopening are under way.
Retrograde transport of fluorescent tracers reveals extensive ipsi‐ and contralateral claustrocortical connections in the rat
Authors: Sloniewski P. , Usunoff K. G. , Pilgrim Ch. 
Published: January 2005

AbstractThe projections from the claustrum to the cerebral cortex in the rat were examined by means of retrogradely transported fluorescent tracers Fast Blue (FB) and Diamidino Yellow dihydrochloride (DY), injected in the prefrontal, motor, somatosensory, auditory, and visual fields. In all cases, substantial numbers of retroo adely labeled neurons were observed in the ipsilateral and moderate to scant numbers in the contralateral claustrum insulare. Symmetrical bilateral injections of FB and DY as well as simultaneous injections of the tracers in the motor and visual cortex of the same hemisphere revealed no double‐labeled neurons in the claustrum.The following conclusions may be drawn: The claustral projections to the motor, somatosensory, and visual cortex are prominent. The projection to the prefrontal cortex is less substantial and that to the auditory cortex is relatively modest. The claustrocortical connections lack the clear‐cut topographic pattern of the thalamic nuclei but are, to some degree, preferentially arranged, albeit with considerable overlapping of the subpopulations of corticopetal neurons, a coarse anteroposterior topographic distribution appears to exist also in rodents. Neurons contributing to the claustrocortical connection project either ipsilaterally or contralaterally but not bilaterally. Projections to different cortical fields of one hemisphere also originate from separate claustral neurons.
Location and connections of visual cortical areas in the cat's suprasylvian sulcus
Authors: Sherk Helen 
Published: January 2005

AbstractThe initial aim of the experiments described here was to identify and quantify the cortical and thalamic connections of visual cortical areas located in the vicinity of the suprasylvian sulcus. Inputs to various sites in this region were studied by making small injections of wheat germ agglutinin (conjugated to horseradish peroxidase) at physiologically identified locations. Retrogradely labeled cells were counted in each identifiable area of cortex and in thalamic nuclei.Some injections yielded quantitatively similar distributions of labeled cells, and it is suggested that such evidence provides a useful way of dividing the cortex into areas. By this criterion, a single, relatively large, cortical area was identified that occupied most of the medial bank of the suprasylvian sulcus, all or most of its posterior bank, and a small segment of its lateral bank. It was referred to as the Clare‐Bishop area. Because neighboring visual areas were found to lack input from area 17, while the Clare‐Bishop area received a strong striate input, its boundaries were investigated by labeling afferents from area 17. Together with the results of retrograde tracer injections, these data suggested that the Clare‐Bishop area cuts across several of the visual areas defined physiologically by Tusa et al. ('81). As a consequence, its retinotopic organization must be relatively complex, with duplications of some parts of the visual field.Three other visual areas were tentatively identified on the basis of their distinctive connections. One was situated on the lateral bank of the suprasylvian sulcus and appeared to border the Clare‐Bishop area laterally. Another, referred to as area 21, lay adjacent to area 19, and, for part of its length, also appeared to bound the Clare‐Bishop area. The third, corresponding approximately to Heath and Jones's ('71) posterior suprasylvian region, lay lateral and anterior to the Clare‐Bishop area' in the depths of the posterior suprasylvian sulcus.
The intercalated cells of the amygdala
Authors: Millhouse O. E. 
Published: January 2005

AbstractThe intercalated cell groups, or massa intercalata, of the amygdala have been studied in rodent brains with Golgi methods. They also have been examined in gallocyanin‐chromalum‐, AChE‐, and Timm‐stained rat brains.The Golgi data indicate that the intercalated cells are not confined to a series of isolated cell clumps but form a neuronal net that covers the rostral half of the lateral‐basolateral nuclear complex, stretches across a major portion of rostral amygdala, and continues rostrally beneath the anterior commissure. There are two general types of intercalated neuron‐medium and large neurons. The medium intercalated neurons are more common. They have round to elongate somata, 9‐18 μm in diameter, and round to bipolar dendritic tress, depending on their location. Most of the dendrites are spine‐bearing, as are 20% of the somata. Their axons often have locally ramifying collaterals. The parent axons apparently terminate in either the lateral‐basolateral or central nuclei and some of them appear to enter the external capsule. There is a unique medium intercalated neuron that has nearly spine‐free, varicose dendrites and an axon that is typical of short axon (Golgi II) cells. There are two varieties of large intercalated neuron‐spiny and aspiny. Most of them are aspiny, although they usually have a few spines scattered along their dendrites. Both varieties have elongate, sometimes round, somata that can be as much as 60 μm long. Their dendrites are long, thick, and have few branch points. Only the initial part of the large aspiny cell axon has been impregnated. The large spiny cell axons have several local collaterals; the destination of the parent axons is unknown.The intercalated cells occur along fiber bundles, which are probably afferent to them. The axons that travel among the intercalated cells give off short collaterals and boutons en passant. The sources of these fibers are not known. From the published experimental data, it is likely that they originate in the piriform and entorhinal cortices, the lateral preoptic area, lateral hypothalamus, and ventral pallidum. Axon collaterals of basolateral nucleus pyramidal cells appear to terminate among the intercalated cells. It is suggested that the intercalated cells serve as sites for integration of the output of these various areas and, in turn, communicate it to the lateral basolateral and central amygdaloid nuclei.The intercalated cells closely resemble neurons in the corpus striatum. Thus the question is raised and discussed of whether the intercalated cells are a ventral extension of the corpus striatum.
Anatomical and electrophysiological study of multitransmitter neuron r14 of aplysia
Authors: Rittenhouse Ann R. , Price Christopher H. 
Published: January 2005

AbstractThis study provides detailed information on the Aplysia neuron R14, including its endogenous electrical activity and extensive axonal projections to a variety of vascular and vascular‐related tissues. With the aid of intracellular recording techniques, R14 was found to display in vitro variable spontaneous patterns of silent, beating, or bursting activity. Electrophysiological tracing and intracellular cobalt staining revealed the peripheral processes and target tissues of R14. The white‐colored axons of R14 exit the parietovisceral ganglion in the genito‐pericardial, spermathecal, branchial, and vulvar nerves. These processes extended 20 mm or more into peripheral tissues: the pericardial wall and lumen, digestive gland sheath, aortae, arteries, and veins. R14 axons also project to the right bag cell cluster. Its extensive axonal projections to tissues associated with the cardiovascular system verify physiological studies that show that R14 plays a role in cardiovascular regulation. This neuron appears to have a wide influence over several aspects of circulation in contrast to individual neurons of the R3‐13 group, each of which projects to limited numbers of vascular and vascular‐related tissues. R14 also uniquely innervates digestive tissues, thus suggesting that it may act as a nexus between influences on digestive and renal physiology such as ion/water regulation, in addition to modulating cardiovascular homeostasis.
Projections from the anteroventral cochlear nucleus to the lateral and medial superior olivary nuclei
Authors: Cant Nell Beatty , Casseday J. H. 
Published: January 2005

AbstractThe projections from the cochlear nucleus to the lateral and medial superior olivary nuclei were studied in the cat by use of retrograde transport of horseradish peroxidase to demonstrate the connections. The medial superior olivary nucleus receives input only from the anterior and posterodorsal subdivisions of the anterior division of the anteroventral cochlear nucleus (AA and APD, respectively; Brawer, Morest, and Kane: J. Comp. Neurol 155: 251‐300, 1974). These two subdivisions are populated almost exclusively by spherical bushy cells. Like the medial superior olivary nucleus, the lateral, superior olivary nucleus receives inputs from AA and APD, In addition, the lateral superior olivary nucleus receives projections from the posterior subdivision (AP) of the anterior division and also from the posterior division of the anteroventral cochlear nucleus. The projections to the medial superior olivary nucleus are bilateral, whereas the projections to the lateral superior olivary nucleus are almost entirely ipsilateral. One implication of the results is that the medial superior olivary nucleus receives inputs from only one cell type‐the spherical bushy cell‐but that, at the least, two cell types project to the lateral superior olivary nucleus. Both the olivary nuclei receive input from most, if not all, of the dorsoventral extent of the anteroventral cochlear nucleus, implying that both receive input from neurons arrayed across the entire frequency representation of the anteroventral cochlear nucleus. All of the projections appear to be organized topographically such that frequency representation is preserved.
A quantitative study of neuronal and glial numerical density in the visual cortex of the bottlenose dolphin: Evidence for a specialized subarea and changes with age
Authors: Garey L. J. , Leuba G. 
Published: January 2005

AbstractNeuronal and glial numerical densities were measured in the lateral gyrus of the cerebral hemisphere of dolphins (Tursiops truncatus) from the neonatal period to adulthood. The cortex studied is the area known to be visually excitable in evoked potential studies. Two distinct parts of the adult lateral gyrus are identifiable, one relatively anterior, in which neuronal density is 23,000/mm3, the other more posterior, with' almost double this density. In a neonate, the neuronal density in the anterior lateral gyrus was found to be more than double that of the adult. No samples from the immature posterior area were available.Glial density varies much less than neuronal density, both with age and between areas. Soon after birth the glia/neuron ratio is 1.6 in anterior lateral gyrus, rising to around 3 in the adult anterior lateral area, and rather less in the posterior region, where neuronal density is high.We speculate that the existence of a high numerical density of neurons in the posterior part of the dolphin visual cortex could perhaps indicate a specialized area corresponding to the primate primary visual cortex, also known to have high neuronal density.
Somatosensory cortical representation in the Australian ghost bat, Macroderma gigas
Authors: Wise Lisa Z. , Pettigrew John D. , Calford Michael B. 
Published: January 2005

AbstractBats of the two suborders Microchiroptera and Megachiroptera have a modified hand in which the digits of the forelimb are caudally oriented to form the wing. In a previous study of a megachiropteran species, this modification of body plan was found to be reflected in the somatosensory cortical representation such that the orientation of the digit representation was reversed compared with walking mammals. This finding suggests that the precisedetails of arrangement of topographical maps are functionally significant and do not merely reflect an order imposed by peripheral innervation. Recentevidence for separate origins of Microchiroptera and Megachiroptera raises the question of whether the cortical somatosensory representation in Microchiroptera will also have a reversal of digit orientation compared with walking mammals. We recorded multiunit activity from the somatosensory cortex of a microchiropteran bat, Macroderma gigas. We found two orderly representations of the body surface, SI and SII, in both of which the digit orientation was opposite to the head orientation in accordance with adaptation for flight, and reversed with respect to equivalent maps in other mammals. We also found minor variations in body surface representation compared with Megachiroptera, in line with their proposed independent evolution.
Myelination of the corpus callosum in the cat: Time course, topography, and functional implications
Authors: Looney Greg A. , Elberger Andrea J. 
Published: January 2005

AbstractThe parameters of myelin development were ascertained in two specific regions of the corpus callosum in a series of cats aged 12 postnatal days through adult. The posteriormost portion of the splenium and the anterior‐most portion of the genu were examined in cross section by using the electron microscope. Measurements were made to determine the age at which myelin first appeared, the number and distribution of myelinated fibers, the number and distribution of myelin lamellae, and cross‐sectional area of ensheathed axons during development. The results indicate that myelination begins and ends earlier in the anterior region of the callosum. Measurements of myelin lamellae indicate similarities between anterior and posterior regions of the callosum, although development occurs earlier in the genu than in the splenium. No evidence was found for a sequence in the size of axons acquiring myelin sheaths, except that extremely small fibers are the last to begin myelinating. Myelination of the splenium of the corpus callosum begins at the very end of the behaviorial and physiological critical period for the corpus callosum's role in visual functional development (Elberger: Behav. Brain Res. 11:223–231, '84; Elberger and Smith: Exp. Brain Res. 57:213–223,'85). Since myelination of a pathway is used as an index of functional reliability, this indicates that the basis for the callosal role in developing visual functions is probably not based on its physiological input to visual cortex.
Regeneration of normal afferent input does not eliminate aberrant synaptic connections of an identified auditory interneuron in the cricket, Teleogryllus oceanicus
Authors: Pallas Sarah L. , Hoy Ronald R. 
Published: January 2005

AbstractIn the cricket, Teleogryllus oceanicus, the dendritic arborizations of an identified auditory interneuron (Int‐1) are normally restricted to the ipsilateral auditory neuropile; unilateral deafferentation causes the medial portion of the dendritic field to sprout across the midline and make functional connections with the contralateral auditory neuropile (Hoy et al., '78: Soc. Neurosci. Abstr. 4:115, '85: Proc. Natl Acad Sci. USA 82:7772–7786; Hoy and Moiseff, '79: Soc. Neurosci. Abstr. 5:163). We have found that regeneration of the auditory afferents also results in an aberrant pattern of innervation of Int‐1.Crickets were unilaterally deafferented during postembryonic development by crushing or cutting the auditory nerve. Regeneration of afferent‐to‐Int‐1 connections was tested behaviorally. Of 86 nerve‐crushed crickets tested as adults in the behavioral assay, 66% showed functional regeneration of the afferents. Similar results were obtained from the nerve‐cut group. However, morphological investigations demonstrated that most of the regenerates still retained the aberrant contralateral dendritic projection. Electrophysiological recordings from these Int‐1s showed that not only are some of them driven by their regenerated auditory afferents (the normal pathway) but that they retain their excitability via their contralateral dendrites (the aberrant pathway). This demonstrates that reinnervation of Int1 by its normal afferent pool neither causes retraction nor prevents the formation of connections made with foreign, contralateral afferents.When the contralateral afferent pool was removed after Int‐1 had sprouted, the sprouts remained present, but preliminary results suggest that if the contralateral afferents are removed before Int‐1 is deafferented, sprouts are not formed.The results are discussed in relation to the roles of competition and conservation of membrane area in controlling synapse formation.
Distribution of neurons and axons immunoreactive with antisera against neuropeptide Y in the normal human hippocampus
Authors: Chan‐Palay V. , Köhler C. , Haesler U. , Lang W. , Yasargil G. 
Published: January 2005

AbstractThe detailed distribution of neuropeptide tyrosine (neuropeptide Y; NPY) immunoreactive neurons and fibers is given for the normal human hippocampus. These neuronal elements are detected by a polyclonal antibody raised against the unconjugated peptide and controls were obtained by using liquid phase absorption immunocytochemistry. The description covers the distribution in the area dentata, the hippocampal subfields CA3 and CA1, the subicular complex, and the entorhinal area. Each region is distinct in its NPY content. In general, the hippocampal NPY immunoreactive neurons fall into distinct classes—large hilar neurons; cortical small bipolar or bitufted neurons; medium‐sized multipolar neurons in the deep cortical layers; and finally the distinct, small bipolar NPY neurons of the white matter bundles. None of the NPY neurons are pyramidal; many are likely to be local circuit neurons, but some appear to have extrinsic connections. The NPY immunoreactive axonal innervation is dense throughout the hippocampus but shows distinct regional differences in the hippocampal subdivisions. The area dentata has hilar NPY immunoreactive neurons and radial varicose fibers scattered throughout without a clear laminar preference. Subfield CA3 is comparatively the weakest NPY‐containing region and contrasts with CA1, which is well endowed with reactive neurons and a rich and unusual axonal innervation, with distinct laminar axonal specializations. The subicular complex is well endowed with cells and fibers and the parasubiculum consistently displays unusually heavy NPY innervation. The entorhinal area exhibits a rich cortical distribution pattern, like that previously described for the human cerebral cortex (Chan‐Palay et al.; J. Comp. Neurol 238:382–390, '85a, b). The fimbria, alveus, and angular bundle have NPY neuron embedded within the white matter. Like the NPY immunoreactive innervation of the hippocampal regions of laboratory animals, the human NPY innervation seems to follow a common fundamental pattern with respect to cell locations, cell morphology, and axonal innervation. The difference, however, is the greater complexity and profusion of the NPY‐immunoreactive axonal plexuses in the human hippocampus. This rich peptide network within the hippocampus with likely extrahippocampal interconnections raises questions concerning coexistence with other neuroactive substances, the functions of such substantial networks, and how they are altered in human neurological disease.
A quantitative analysis of the spinal motor pool and its target muscle during growth in the dogfish, Scyliorhinus canicula
Authors: Mos W. , Williamson R. 
Published: January 2005

AbstractIn order to relate the phenomenon of continuous growth in fishes to the development of the neuromuscular system, we established the numbers and sizes of spinal motoneurons and red and white axial muscle fibers in late‐and post‐embryonic dogfish within the size range 6–71 cm. We found that (1) motoneuron somata, ventral root axons, and red and white muscle fibers increase their size throughout the life of the animal; (2) there is an initial increase in the number of motoneurons that ceases as the fish reaches a length of about 40 cm; (3) white muscle fibers initially decrease in number during post‐embryonic life; and (4) red muscle fibers increase in number, but this increase levels off at a fish length of about 40 cm.Spinal motoneurons innervating red myotomal muscle fibers or centrally located white muscle fibers were identified after retrograde labeling with horseradish peroxidase, which was injected in small amounts into the respective muscle areas. The motoneurons supplying the red muscle are smaller and occupy a more lateral position in the ventral horn than the white muscle motoneurons. The number of motoneurons in the ventral horn per unit area increases from medial to lateral and this is associated with a reduction in the sizes of the somata.Values for the ratio of number of muscle fibers to number of supplying motoneurons in the various muscle areas were based on axon counts within the peripheral nerves. This ratio was higher for the centrally located white muscle fibers than for the ventral or dorsal white fibers, but was highest for the red fibers.
Ventral root nonmedullated fibers: Proportion, calibers, and microtubular content
Authors: Vergara Ismael , Oberpaur Bernd , Alvarez Jaime 
Published: January 2005

AbstractProportion, caliber, and microtubular content of the L7 ventral root nonmedullated fibers were studied in the cat. Nonmedullated fibers constituted 28% of the axonal population at the far end of the root. The number of myelinated profiles at the far end of the root and in the vicinity of the ventral surface of the cord (1–2‐mm distance) was the same whereas the number of nonmedullated fibers decreased toward the proximal site of the root by 42%. Caliber and microtubular content of nonmedullated fibers were assessed only at the far end of the ventral root. Nearly 90% of the axons were smaller than 0.3 μm2. The average cross‐sectional area was 0.15 μm2, a value 35% below that of the L7 dorsal root fibers. The microtubular density was highest in the finest fibers (116 microtubules/μm2 in fibers smaller than 0.1 μm2) and decreased with the increase in cross‐sectional area (25 microtubules/μm2 for 0.7–0.8‐μm2 axons). The number of microtubules per axon in axons of both roots was similar in fibers smaller than 0.3 μm2; in larger axons, composing about 10% of the population, ventral root fibers had more microtubules than dorsal root fibers.The ventral and dorsal nonmedullated fibers differ slightly but significantly in caliber and microtubule content. However, they are similar in contrast to peripheral nonmedullated fibers, which are three to four times as big and contain two to three times as many microtubules as radicular fibers.Our results confirm the presence of a large admixture of nonmedullated profiles in the L7 ventral root of the cat, support the notion that a number of these fibers make a U turn in the ventral root, and suggest that these arise from the central process of the primary sensory axon.