bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple cortical targets of one thalamic nucleus: The projections of the ventral medial nucleus in the cat studied with retrograde tracers
Authors: Minciacchi D. , Bentivoglio M. , Molinari M. , Kultas‐Ilinsky K. , Ilinsky I. A. , Macchi G. 
Published: January 2005

AbstractThe organization of the cortical projections of the ventral medial thalamic nucleus (VM) was studied in the cat with retrograde tracers. The extent of the VM‐cortical projections was first investigated with horseradish peroxidase injected in different cortical fields. The results obtained in the experiments indicated that (1) the main target of VM efferents is represented by a large territory anterior to the cruciate sulcus involving area 6 and the gyrus proreus and extending into the anterior part of the medial cortical surface. The afferents to these precruciate fields arise from throughout the VM. In addition, the lateral third of VM projects upon the lateral precruciate cortex that is coextensive with the precruciate part of area 4, whereas VM efferents do not extend into the posterior sigmoid gyrus. (2) A second major target of VM efferents is represented by the insular cortex in the anterior sylvian gyrus. (3) VM projections also reach the prepyriform cortex and the cingulate gyrus. An anteroposterior decrease of density was found in the VM‐cingulate projections. (4) Sparse VM projections reach the temporal cortex, the adjacent posterior sylvian and ectosylvian fields, and the anterior ectosylvian gyrus. (5) No VM projections were found either upon the visual areas 17 and 18 or upon the primary auditory cortex.The interrelations between some VM‐cortical cell populations and their divergent collateralization were studied by using double retrograde labeling with fluorescent tracers. The results of these experiments demonstrated that a relatively high number (at least 20%) of VM cells projecting to the insula are also connected to the precruciate fields by means of axon collaterals. This finding indicates that VM is a highly collateralized structure of the cat's thalamus. Very few branched cells were found in the other combinations of cortical fields here examined (precruciate vs. posterior sylvian fields, lateral precruciate vs. proreal cortex, anterior vs. posterior cingulate fields). Altogether these data indicate that VM branched cells preferentially interconnect the two main cortical targets of the nucleus, i.e., precruciate and insular fields.The results of the present study are discussed in regard to the literature on the VM projections in the rat and the previously available data in the cat, to the afferent VM organization in the cat, to the relationship between VM and the nucleus submedius, and to the anatomical and functional role of VM in relation to the so‐called “nonspecific” thalamocortical system.
Species differences in the distribution of substance p and tyrosine hydroxylase immunoreactivity in the olfactory bulb
Authors: Baker Harriet 
Published: January 2005

AbstractThese studies document species differences in the distribution of the peptide substance P and the catecholamine‐synthesizing enzyme tyrosine hydroxylase (TH) within a central nervous system region of a number of mammalian species including the mouse, rat, guinea pig, rabbit, cat, and two species of hamster (Chinese and Syrian). Substance P‐containing neuronal perikarya were observed in the main olfactory bulb (MOB) of both species of the hamster, but not in the MOB of the other species examined. In the accessory olfactory bulb (AOB), however, neuronal staining was observed in all species except the mouse. The number of stained somata and their intensity varied such that label was most prominent in the rat followed in decreasing order by the rabbit, guinea pig, cat, and hamster. The mouse displayed no perikaryal staining. Stained somata in AOB were found in the internal granule cell layer with dendritic processes ramifying through the internal plexiform layer to arborize within the mitral cell layer.The distribution of substance P‐stained neurons in the MOB also differed between the two hamster strains. In the Syrian hamster, neurons were primarily juxtaglomerular. In the Chinese hamster, labeled perikarya were found in both the juxtaglomerular region and within the superficial aspect of the external plexiform layer (EPL). The mean longest diameter of the majority of substance P‐labeled neurons in both species was greater than 10 μm, suggesting that they were tufted cells. Those in the EPL of the Chinese hamster were the largest (17 μm). Species differences also were observed in the distribution of substance P‐positive axons and terminals within the MOB. Lable was distributed primarily in the internal granule cell layer of the Syrian hamster and the internal plexiform layer of the Chinese hamster.Tyrosine hydroxylase staining was similar among species with the exception of the Syrian hamster. In the latter species, an additional large population of neurons was found within the external plexiform layer. In all other species, TH‐stained neurons were found scattered throughout the MOB and occasionally the AOB but were not numerous in the EPL. Although most TH neurons were larger than 10 μm, in all species a population of smaller TH cells was observed primarily in the glomerular layer, suggesting that most neurons labeled with TH are tufted cells but that some may be periglomerular cells.In conclusion, these data suggest that either substance P is present in the MOB of hamsters but is not found in juxtaglomerular neurons of the main olfactory bulb of the mouse, rat, guinea pig, rabbit, or cat, or that species differences exist in the level of substance P or in its processing from precursors. In either case, by using the same fixation and staining procedures, the peptides can be localized in some and not other species, whereas tyrosine hydroxylase staining is similar in all species examined.
Cerebellar nucleocortical projection with a survey of factors affecting the transport of radioactive tracers
Authors: Legendre A. , Courville J. 
Published: January 2005

AbstractThe nucleocortical projection has been studied with the method of anterograde transport of tritiated amino acids and autoradiography. It was observed that this projection is made up of a small number of fibers. Counts of silver grain aggregates in projection sites of the granular layer were compared with counts from material on the cuneocerebellar projection. As it had been concluded in previous studies that the projection is quantitatively important, several modifications of the experimental conditions were tested. Radioactive leucine of high or low specific activity as well as a mixture of amino acids were used. It was observed that labeling is always more intense with a high specific activity tracer. Variations of the aspect and density of the projection were observed with survival periods lasting from a few hours to several days. With survival times between 9 and 15 hours, round aggregates of silver grains measuring from 10 to 20 μm were observed in the granular layer of labeled regions. At longer survival periods, the terminal structures in the granular layer appeared as coarse linear aggregates. It is suggested that the latter represent preterminal labeled fragments while the round accumulations correspond to terminal rosettes. Maximum density of the labeling in the granular layer occured between 9 and 15 hours. At 2 days, the density was lowest, and at 5 or 6 days it was somewhat higher. Even under optimal conditions, the density of the nucleocortical terminals was low.
Comparative anatomy of the ventromedial mesencephalic tegmentum in the rat, cat, monkey and human
Authors: Halliday Glenda M. , Törk Istvan 
Published: January 2005

AbstractThe five component nuclei of the ventromedial mesencephalic tegmentum (VMT) were studied on Nissl stained serial sections of the brain stem of rat, cat, monkey (Macaca nemestrina) and human. Models of the VMT nuclei were constructed to compare their size, shape and disposition across species. For each nucleus ineach species the following were calculated: the volume, the number of neurons, the size distribution of neurons, the mean soma size and the packing density of neurons. The morphology of the cells in the different nuclei is also described.The parabrachial pigmented nucleus (PBP) forms, on average, 51% of the VMT volume and cell number. The paranigral nucleus (PN) and the central linear nucleus (LC) formed 19% and 14% of the VMT volume and cell number respectively. The relatively small, but compact interfascicular nucleus (IF) was on average 9% of the VMT volume and cell number and the rostral linear nucleus (LR) formed its remaining 7%. However, in different species the relative prominence varies between species. Thus PBP is the largest of the VMT nuclei in the monkey, PN is particularly well developed in the human, IF contains a particularly large number of cells in the rat, and LR and LC are strongly developed in the cat.This study presents a cytoarchitectonic description of the five nuclei in each species. The distinctive cytoarchitectonic appearance of each nucleus suggests that their functions may differ. This possibility, which is strengthened by evidence that the projections of the VMT nuclei are differential, may need to be considered in the interpretation of the results of experimental investigations using stimulation and/or lesion experiments in the VMT region and in the interpretation of pathological findings in the human brain.
Colonization of the bowel by the precursors of enteric glia: Studies of normal and congenitally aganglionic mutant mice
Authors: Rothman Taube P. , Tennyson Virginia M. , Gershon Michael D. 
Published: January 2005

AbstractThe terminal portion of the ls/ls mouse is congenitally aganglionic because the precursors of enteric neurons fail to enter this region. This animal was studied in order to gain insight into the origin of enteric glia and into the process by which the precursors of these cells colonize the gut. In control (CD‐1) mice, immunoreactivity of the glial marker, glial fibrillary acidic protein, appeared for the first time in the fetal bowel at day E16 and, in adults, was much more intense within intraenteric neural elements than in nerves outside the bowel. Glial fibrillary acidic protein developed in tissue cultures of fetal intestine explanted before the protein appeared in situ, and before the bowel became innervated by extrinsic nerves; thus, the precursors of cells able to elaborate glial fibrillary acidic protein must have been present, but unrecognizable, in the original explants. This explant assay demonstrated that these glial precursors were present in all regions of the bowel of control mice, but not in the presumptive aganglionic bowel of ls/ls mice. The nerves (of extrinsic origin) in the aganglionic tissue of ls/ls mice showed a high level of immunoreactive glial fibrillary acidic protein; nevertheless, their ultrastructure was typical of peripheral nerve, not enteric plexus, and they contained Schwann cells, not enteric glia. These observations support the view that enteric glia are derived from the single wave of neural crest colonists that populates the enteric nervous system before the gut receives its extrinsic innervation. These glial precursors, like neuronal precursors, tend to be excluded from the presumptive aganglionic ls/ls bowel. In contrast, Schwann cells grow into the abnormal ls/ls gut with the extrinsic innervation. The enteric microenvironment appears to promote the expression of glial fibrillary acidic protein in both enteric glia and Schwann cells; however, even within the bowel, Schwann cells retain their characteristic morphology. It is thus probable that the normal enteric nervous system contains supporting cells of separate lineages, enteric glia and Schwann cells.
Synaptic relationships between neurons containing vasopressin, gastrin‐releasing peptide, vasoactive intestinal polypeptide, and glutamate decarboxylase immunoreactivity in the suprachiasmatic nucleus: Dual ultrastructural immunocytochemistry with gold‐substituted silver peroxidase
Authors: van den Pol Anthony N. , Gorcs Tamas 
Published: January 2005

AbstractIn order to examine the morphological substrates for neuronal connections between cells of the hypothalamic suprachiasmatic nucleus (SCN) that contain immunoreactivity for different neurotransmitters, a double ultrastructural immunocytochemical analysis was used. For double immunostaining, the first neuroactive substance antigen was labeled with goldsubstituted silver‐intensified peroxidase (GSSP), which results in a granular gold deposit of high electron and light opacity. The second antigen was labeled with peroxidase and a diaminobenzidine chromagen.The GSSP reaction product greatly increased the visibility of immunoreactive structures, with both light and electron microscopy. Intensification with the GSSP method worked at all depths of thick tissue sections as determined with analysis of immunostained sections cut perpendicular to their flat surface, and with analysis of thick 80‐μm sections of brain tissue into which horseradish peroxidase (HRP) has been microinjected. On a nitrocellulose dot‐blot comparison of different substrates for HRP, the GSSP intensification compared favorably with tetramethylbenzidine, but unlike tetramethylbenzidine, the GSSP was stable in a wide range of buffers. In addition to diaminobenzidine, the GSSP reaction was used to intensify and stabilize both the Hanker‐Yates reagent and tetramethylbenzidine on the nitrocellulose model system.Through the use of the GSSP reaction, five new synaptic relationships in the suprachiasmatic nucleus were revealed. By increasing the sensitivity of the peroxidase method by silver‐gold intensification, immunoreaction product could be found in dendrites at a greater distance from the perikaryon than in nonintensified material. Because of this greater sensitivity, the neuroactive substance contained in the cell of origin of a dendrite could sometimes be identified. Boutons immunoreactive for vasopressin‐associated neurophysin were found to make synaptic contact with postsynaptic dendrites that also contained vasopressin‐neurophysin immunoreactivity. Similarly, boutons containing gastrin‐releasing peptide immunoreactivity made synaptic contact with cells also exhibiting gastrin‐releasing peptide immunoreactivity.
Origin and ultrastructural identification of dorsal column nuclear synaptic terminals in the basilar pontine gray of rats
Authors: Kosinski R. J. , Azizi S. A. , Border B. G. , Mihailoff B. G. A. 
Published: January 2005

AbstractThe ultrastructural characteristics of HRP‐WGA‐labeled or degenerating axon terminals arising from neurons in the dorsal column nuclei (DCN) were identified within the contralateral basilar pontine nuclei (BPN) following unilateral HRP‐WGA injections or ablations of the DCN. The cells of origin of these projections were also identified through the application of the retrograde tracer HRP‐WGA.Two groups of degenerating DCN‐pontine terminals were identified. Both formed asymmetrical synaptic contacts with dendritic shafts and/or dendritic appendages of pontine neurons. One group of degenerating terminals contained small, round synaptic vesicles, while the other exhibited a mixture of dense core and pleomorphic vesicles. The former group, which clearly represented the majority of degenerating terminals observed, was interpreted to progress from an early filamentous form of degeneration to a later electron‐dense variety and to originate from dorsally located DCN cells distributed primarily at the level of and just caudal to the area postrema. Other DCN‐labeled neurons were more ventrally located and were postulated to give rise to those degenerative boutons that contained a mixture of dense core and pleomorphic‐shaped vesicles. The present study also identified the cells of origin of two additional projections to the basilar pons: one from cells in the external cuneate nucleus and another from neurons of the medullary reticular formation.
Coincidence of patchy inputs from the lateral geniculate complex and area 17 to the cat's clare‐bishop area
Authors: Sherk Helen 
Published: January 2005

AbstractPathways from a variety of structures to the largest of the cat's suprasylvian visual areas, the Clare‐Bishop area, were found to be patchy. These inputs arose from the lateral geniculate complex, from area 18, from area 19, and, as noted by Montero (Brain Behav. Evol. 18:194–218, '81), from area 17. The Clare‐Bishop area was previously delineated on the basis of its uniform pattern of connections with cortex and thalamus (Sherk: J. Comp. Neurol. 247:1–31, '86) and found to incorporate pieces of several retinotopically defined areas (Tusa, Palmer, Rosenquist: Cortical Sensory Organization. Vol 2. Multiple Visual Areas. Clifton, NJ: Humana Press, pp. 1–31, '81). However, since individual patches did not correspond to particular retinotopically defined areas, other explanations of afferent patchiness were sought.An obvious question is whether the patches originating from different sources are systematically related to each other. Two hypotheses were considered. First, different inputs—for example, from the lateral geniculate nucleus (LGN) and from area 17—might terminate in intermingled but mutually exclusive zones in the Clare‐Bishop area. Second, multiple patches of input might reflect duplicate representations of the corresponding visual field segment in the Clare‐Bishop area. Both hypotheses were tested by injecting the lateral geniculate complex and either area 17 or area 19 with different anterograde tracers. In each case the two injections involved regions of the visual field that coincided to some degree, ranging from near‐total overlap to almost complete exclusion. The first hypothesis predicted that the different labels in the Clare‐Bishop area would never be found to overlap, while the second hypothesis predicted that when injections were closely matched retinotopically, there would be extensive overlap between patches.The results supported the second hypothesis: the better the retinotopic match between injections, the greater the overlap found between labeled geniculate and cortical input in the Clare‐Bishop area. However, the multiplicity of patches seen in some experiments, and the close spacing between some patches, suggested that an additional, nonretinotopic mechanism also contributes to patchiness in the projections to the Clare‐Bishop area.
Frontal eye field as defined by intracortical microstimulation in squirrel monkeys, owl monkeys, and macaque monkeys: I. Subcortical connections
Authors: Huerta Michael F. , Krubitzer Leah A. , Kaas Jon H. 
Published: January 2005

AbstractIntracortical microstimulation was used to define the borders of the frontal eye fields in squirrel, owl, and macaque monkeys. The borders were marked with electrolytic lesions, and horseradish peroxidase conjugated to wheat germ agglutinin was injected within the field. Following tetramethyl benzidine histochemistry, afferent and efferent connections of the frontal eye field with subcortical structures were studied. Most connections were ipsilateral and were similar in all primates studied. These include reciprocal connections with the following nuclei: medial dorsal (lateral parts), ventral anterior (especially with pars magnocellularis), central lateral, paracentral, ventral lateral, parafascicular, medial pulvinar, limitans, and suprageniculate. The frontal eye field also projects to the ipsilateral pretectal nuclei, subthalamic nucleus, nucleus of the posterior commissure, superior colliculus (especially layer four), zona incerta, rostral interstitial nucleus of the medial longitudinal fasciculus, nucleus Darkschewitsch, dorsomedial parvocellular red nucleus, interstitial nucleus of Cajal, basilar pontine nuclei, and bilaterally to the paramedian pontine reticular formation and the nucleus reticularis tegmenti pontis. Many of these structures also receive input from deeper layers of the superior colliculus and are known to participate in visuomotor function. These results (1) reveal connections that account for the parallel influence of the superior colliculus and the frontal eye field on visuomotor function; (2) suggest that there has been little evolutionary change in subcortical connections, and therefore function, of the frontal eye fields since the time that these lines of primates diverged; and (3) support the conclusion that the frontal eye fields are homologous in New and Old World monkeys.
Changes in the numerical density of synaptic contacts with long‐term potentiation in the hippocampal dentate gyrus
Authors: Desmond Nancy L. , Levy William B. 
Published: January 2005

AbstractLong‐term potentiation (LTP) in the rat dentate gyrus is a multifaceted phenomenon, including synaptic potentiation; simultaneous synaptic depression at neighboring, unconditioned synapses; and a change in the amount of cell firing produced by a specified amount of synaptic current (see Levy and Desmond: In G. Buzsaki and C. Vanderwolf (eds): Electrical Activity of The archicortex. Budapest: Akademiai Kiado, pp. 359–373, ′85b). This study presents long‐term anatomical modifications that seem related to excitatory synaptic modification. These anatomical alterations appear early and persist for at least 60 minutes following conditioning stimulation.Each animal received test pulse stimulation delivered alternately to the angular bundles before and after brief, unilateral high‐frequency conditioning stimulation that is typical of many LTP paradigms. Anataomical preparation followed standard procedures. Double‐blind scoring procedures quantified the number of asymmetric synapses in the dentate molecular layer. These counts were converted to the number of synapses per unit volume using stereological corrections that combined geometrically derived theory and modest serial sectioning. Multivariate analysis of variance evaluated the statistical significance of changes in synapse density.Across all three groups of animals, conditioning stimulation does not significantly change the density of synaptic contacts across the entire molecular layer. There is a trend for a decreased density of synaptic contacts in the middle molecular layer, the region activated by the conditioning stimulation. Here the density of concave spine profiles increases significantly in all three groups of animals with conditioning stimulation. This increase accompanies significant decreases in the density of nonconcave, simple and ellipsoid, spine profiles. No significant changes in the density of shaft synapses occur with LTP‐inducing conditioning stimulation.These data suggest that the concave spine profiles are a correlate of LTP‐inducing stimulation and may be the potentiated synapses. We hypothesize that with synaptic potentiation there occurs an interconversion of spine synapses such that some nonconcave spine profiles become concave spine profiles. Such an interconversion apparently begins shortly after the conditioning stimulation and persists for at least 60 minutes.