bluuebunny/crossref_metadata_2025_split huggingface dataset:
A quantitative assessment of the development of synapses and neurons in the visual cortex of control and undernourished rats
Authors: Warren M. A. , Bedi K. S. 
Published: January 2005

AbstractMale rats undernourished from the 18th day of gestation until 100 days of age were nutritionally rehabilitated until 200 days of age. Six control and six experimental rats at each of 12, 25, 50, 100, and 200 days of age were killed by perfusion with buffered 2.5% glutaraldehyde. Pieces of visual cortex from each rat were postfixed in osmium tetroxide and embedded in resin. Stereological procedures at the light and electron microscope levels were used to estimate the synapse‐to‐neuron ratios in cortical layers II to IV.There were no statistically significant differences in the synapse‐to‐neuron ratio between control and undernourished rats at 12, 25, and 50 days of age. However 100‐day‐old undernourished rats had a significant deficit in this ratio compared to age‐matched controls. Despite this, 200‐day‐old nutritionally rehabilitated rats were found to have, on average, 23% more synapses per neuron than controls.In both the control and the undernourished groups the synapse‐to‐neuron ratio increased to a peak by 50 days of age. This was followed by a significant fall in the ratio by 100 days of age. Although there was no further change in the control rats, the experimental group showed a substantial increase in the ratio by 200 days of age. This latter increase appeared to be related to the period of nutritional rehabilitation.
Cartwheel neurons of the dorsal cochlear nucleus: A Golgi‐electron microscopic study in rat
Authors: Wouterlood Floris G. , Mugnaini Enrico 
Published: January 2005

AbstractCartwheel neurons in rat dorsal cochlear nucleus (DCN) were studied by Golgi impregnation‐electron microscopy. Usually situated in layers 1–2, cartwheel neurons (10–14 μm in mean cell body diameter) have dendritic trees predominantly in layer 1. The dendrites branch at wide angles. Most primary dendrites are short, nontapering, and bear only a few sessile spines. Secondary and tertiary dendrites are short, curved, and spine‐laden. The perikaryon forms symmetric synapses with at least two kinds of boutons containing pleomorphic vesicles. The euchromatic nucleus is indented and has an eccentric nucleolus. The cytoplasm shows several small Nissl bodies, a conspicuous Golgi apparatus, and numerous subsurface and cytoplasmic cisterns of endoplasmic reticulum with a narrow lumen, joined by mitochondria in single or multiple assemblies. In primary dendrites mitochondria are situated peripherally, while in distal branches they become ubiquitous and relatively more numerous. Dendritic shafts usually form symmetric synapses with boutons that contain pleomorphic vesicles. The majority of the dendritic spines are provided with a vesiculo‐saccular spine apparatus. All dendritic spines have asymmetric synapses. Most of these are formed with varicosities of thin, unmyelinated fibers (presumably axons of granule cells) running parallel to the long axis of the DCN or radially. These varicosities contain round, clear synaptic vesicles. On the initial axon segment few symmetric synapses are present. The axon acquires a thin myelin sheath after a short trajectory. Cartwheel neurons outnumber all other neurons in layers 1–2 (with the exception of granule cells), and presumably correspond to type C cells with thinly myelinated axons described by Lorente de Nó. The axons of these neurons provide a dense plexus in the superficial layers without leaving the DCN. The possible functional role of cartwheel neurons is discussed.
Identifiable neurons in the locust central nervous system that react with antibodies to serotonin
Authors: Tyrer N. Mark , Turner Jon D. , Altman Jennifer S. 
Published: January 2005

AbstractA detailed account is given of a number of neurons in the locust central nervous system that react with antibody raised to serotonin‐albumin complex. The antibody was applied to a series of frozen sections of locust ganglia and visualized by using the peroxidase immunohistochemical procedure. The neurons described include certain afferents and their related neuropiles, a small number of efferents and several systems of interneurons, some of which are segmentally repeated, some run from the brain through the whole nerve cord, while others are confined to the brain. It has been possible to identify many of the neurons from previous descriptions obtained from cobalt, Golgi, and osmium ethyl gallate methods.
Long‐term effect of mossy fiber degeneration in the rat
Authors: Anderson W. A. , Flumerfelt B. A. 
Published: January 2005

AbstractMossy fiber‐deafferentated rats (20) were permitted to survive from 34 to to 120 days and subsequently examined following Golgi‐Cox preparation or after processing for electron microscopy. The primary response to mossy fiber deafferentation was transneuronal degeneration of the granule cell system. Morphological evidence is provided that suggests that the mossy fiber varicosity plays an important role in the fragmentation and removal of the granule cell digitiform dendrite. Computer‐assisted image analysis of Golgi‐impregnated Purkinje cells indicated significant losses in both smooth branch and spiny branchlet numbers following loss of the mossy fiber input. Ultrastructural examination revealed that a secondary transneuronal degeneration occurred within the dendritic arborization of both Purkinje cells and molecular layer interneurons. Although an overall reduction in the number of dendritic spines occurred along the terminal branchlets following mossy fiber deafferentation, several of the existing spines underwent marked changes in length, with some elongating to more than twice their size. By increasing the length of their spines, denervated Purkinje cells may acquire new synaptic contacts.
Cerebellar cortical efferent fibers in the North American opossum, Didelphis virginiana. I. The anterior lobe
Authors: Klinkhachorn P. S. , Haines D. E. , Culberson J. L. 
Published: January 2005

AbstractThe distribution of cerebellar corticonuclear and corticovestibular fibers from the anterior lobe of the North American opossum, Didelphis virginiana, was studied using the Fink and Heimer (1967) technique.Corticonuclear fibers from medial areas of anterior lobe project into the medial cerebellar nucleus (NM) in a topographically organized manner. Fibers from lobules II and III enter rostral and rostrodorsal NM, while those from lobules IV and V terminate in progressively more caudal parts of the nucleus. Collectively the terminal fields in NM for axons from lobules II–V occupy about the rostral two–thirds of the nucleus.Those areas of lobules II‐V of opossum that project into NM presumably correspond to zone A of cat and primate. Cerebellar corticovestibular fibers originate from cortex located immediately lateral to areas projecting to NM. The predominance of corticovestibular projections into the lateral vestibular nucleus suggests the presence of a B zone and identifies its points of interface with the A zone. The results further suggest that zones A and B overlap at their respective margins. In contrast to other mammals studied to date, zones A and B of opossum anterior lobe are comparatively wide. Corticonuclear fibers to anterior and posterior interposed nuclei and to the lateral cerebellar nucleus (NL) originate from relatively narrow lateral portions of anterior lobe. These results also suggest that the intermediate cortex of opossum anterior lobe is not clearly divisible into individual zones C1, C2 or C3. The cortical area that innervates NL is very narrow and presumably corresponds to zone D of other forms.
A developmental gradient of dendritic loss in the avian cochlear nucleus occurring independently of primary afferents
Authors: Parks Thomas N. , Jackson Hunter 
Published: January 2005

AbstractCochlear nerve axons and their target neurons in nucleus magnocellularis (NM) of the chicken undergo extensive parallel structural transformations during development. Between embryonic days 12 and 17 (E12–E17), each immature highly branched axon condenses into a mature calyxlike ending applied to a single NM neuron. Simultaneously, NM neurons are transformed from multipolar cells with many long dendrites into spherical unipolar neurons with only an axon. We tested the hypothesis that cochlear nerve input is necessary for the transformation of NM cells by surgically destroying one otocyst on E3, thereby preventing formation of the nerve. Nucleus magnocellularis neurons from embryos at E11–E12, E13–14, and E17–18 were stained by horseradish peroxidase injected into their axons or by a Golgi‐Hortega method. In camera lucida drawings, the number of dendrites on each cell was counted and the cell's position along the posteriorto‐anterior and lateral‐to‐medial axes of the nucleus quantified. At E11–12, neurons throughout NM on both the deafferented and normally innervated sides of the brain have about ten dendrites. At E13–14, there is a steep spatial gradient in dendritic number bilaterally; cells at anteromedial positions have about two dendrites, while cells in posterolateral positions have an average of nine dendrites. By E17–18, only 14% of the neurons on either side have a dendrite, and these cells are evenly distributed throughout the nucleus. We conclude that cochlear nerve axons are not required for normal spatio‐temporal gradients of dendritic loss, even though the absence of these axons causes severe atrophic changes in NM. Thus, it appears that the characteristic forms of the afferent axon and target neuron in this system must develop in one of two ways. Either NM cells control the structural differentiation of their cochlear nerve afferents, or the forms of axon terminals and their target cells develop independently. These alternative, hypotheses can be evaluated experimentally.
The visual field representation of the rat ventral lateral geniculate nucleus
Authors: Nagata Tetsu , Hayashi Yasumasa 
Published: January 2005

AbstractThe representation of the visual field in the ventral lateral geniculate nucleus (LGNv) was studied in rats anesthetized with urethane by recording the response of single units to visual stimulation. Receptive fields of LGNv units were plotted on a campimeter, 60 cm in diameter, which was placed 30 cm from the contralateral eye. LGNv neurons responded mainly to stimulation of the contralateral eye with on‐tonic characteristics. Few neurons responded only to stimulation of the ipsilateral eye and no binocular interaction was observed.Retinotopic organization was clearly seen in the LGNv; the nasal visual fields were represented dorsally, the temporal fields ventrally, and the upper to lower visual fields were in the rostrolateral to caudomedial parts of the LGNv. A given point in the visual field is represented along a line running through the LGNv in a rostrocaudal direction.Almost the entire horizontal extent of the contralateral visual field was represented in the LGNv, whereas vertically the visual field between 40° above and 20° below the distribution axis was represented. The major axis of the strip of the visual field containing all the RF centers, which is referred to as the distribution axis, inclined nasally up and temporally down at an angle of 10.4° to the 0° horizontal meridian line. The representation of the distribution axis in the retina was in accordance with the major axis of retinal ganglion cell distribution (Fukuda, 1977; Schober and Gruschka, 1977).
Somatosensory thalamocortical connections in the racoon: An HRP study
Authors: Warren Susan , Pubols Benjamin H. 
Published: January 2005

AbstractIn the North American raccoon (Procyon lotor), representations of the glabrous surfaces of the hand digits are found within separate subnuclei of the thalamic ventrobasal complex (VB) and on separate subgyri of the somatosensory cortex (SmI). In the present study, the retrograde transport of horseradish peroxidase from SmI to VB was utilized to study relationships between physiologically identified cortical subgyri and somatotopically corresponding thalamic subnuclei.Single large or multiple small injections confined to a single gyral crown led to retrograde labeling of large groupings of cells filling the entire VB subnucleus for the appropriate digit. In the aggregate, the regions of label appeared as thin, wedge‐shaped sheets extended in the dorsoventral and anteroposterior dimensions, but flattened mediolaterally, and curving to form a laterally directed convexity; these appear to correspond to the lamellae of monkey VB described by others. These large injections led to labeling of approximately 80% of all large (18–30‐μm diameter) cells within the lamella. Single, small, focal injections of a gyral crown led to variable amounts of labeling, ranging from an entire digital lamella to only a small focal cluster of cells. No evidence was obtained for the existence of anteroposteriorly extending “rods” of cells, as reported in primates. Finally, there was a sparse, but consistent labeling of cells of the posterior nuclear group (Po) following gyral crown injections.These results are in agreement with expectations based on prior electrophysiological studies of raccoon VB and SmI, as well as prior anatomical studies of thalamocortical relationships.
Anterograde degeneration in the superior colliculus following kainic acid and radiofrequency lesions of the macaque pulvinar
Authors: Bender D. B. , Baizer J. S. 
Published: January 2005

AbstractSeveral studies have reported behavioral deficits following thermocoagulation of the primate pulvinar. However, these deficits may have resulted from damage to corticotectal fibers as they pass through the pulvinar. To evaluate this possibility and to determine whether kainic acid can be used to destroy pulvinar cells without damaging corticotectal fibers, we compared anterograde degeneration in the superior colliculus following kainic acid and radiofrequency lesions of the pulvinar. Kainic acid injections into the pulvinar produced total loss of neuronal perikarya within the inferior and lateral pulvinar. Four to 7 days following the kainic acid lesions, terminal and fiber degeneration within the superior colliculus was no greater than that produced by control injections of saline. By contrast, thermocoagulation lesions of the inferior and lateral pulvinar produced dense fiber and terminal degeneration throughout the superficial and intermediate layers of the superior colliculus. We conclude that whereas thermocoagulation of the pulvinar severely damages the corticotectal tract, kainic acid lesions spare these fibers of passage. Thus kainic acid lesions should provide an effective tool for studying the functional significance of the pulvinar.
Somatic and visceral primary afferents in the lower thoracic dorsal root ganglia of the cat
Authors: Cervero F. , Connell Lynne A. , Lawson Sally N. 
Published: January 2005

AbstractAnterograde transport of horseradish peroxidase (HRP) through somatic and visceral nerves was used to estimate the proportions of somatic and visceral dorsal root ganglion (DRG) cells of the lower thoracic ganglia of the cat. A concentrated solution of HRP was applied for at least 5 hours to the central end of the right greater splanchnic nerve and of the left T9‐intercostal nerve of adult cats. Some animals remained under chloralose anaesthesia for the duration of the HRP transport time (up to 53 hours) whereas longer HRP application and transport times (4–5 days) were allowed in animals that recovered from barbiturate anaesthesia. Visceral DRG cells were found in approximately equal numbers in all ganglia examined (T7–T11). Population estimates were obtained for the T8 and T9 ganglia where visceral DRG cells were found to be 6.2% (T8) and 5.2% (T9) of the total cell population. In contrast, somatic DRG cells were found in large numbers in the ganglia examined (T8 and T9) where they amounted to over 90% of the cell population. Measurement of cross‐sectional areas and estimates of cell diameters of the DRG cells showed greater proportions of large somatic cells (diameter > 40 μm) than of large visceral cells. Similar distributions of cell size were found for both somatic and visceral DRG cells with diameters less than 40 μm.These results show that the proportion of visceral afferent fibres in the dorsal roots that mediate the spinal cord projection of the splanchnic nerve is very small. Since viscerosomatic convergence in the thoracic spinal cord is very extensive, the present results suggest considerable divergence of the visceral afferent input to the central nervous system.
Postnatal development of primary visual projections in the tammar wallaby (Macropus eugenii)
Authors: Wye‐Dvorak Judith 
Published: January 2005

AbstractThe time course and pattern of retinal innervation of primary visual areas was traced in pouch‐young wallabies. Tritiated proline was injected into one eye of animals ranging in age from 1 to 72 days after birth. These results are compared to the 11 primary visual areas found in the adult wallaby, seven of which receive binocular input while four are monocular. At birth retinal ganglion cell axons have not reached any visual areas. Two to 4 days after birth, all of the axons are crossing to the contralateral optic tract. Nine to 12 days after birth axons begin to invade the contralateral lateral geniculate nucleus, the superior colliculus, and the medial terminal nucleus. Twenty to 21 days after birth, ipsilateral axons invade the lateral geniculate nucleus and superior colliculus. The contralateral projection precedes the ipsilateral projection in all binocular visual areas. By 25 days, ipsilateral and contralateral afferents share common territory in the lateral geniculate nucleus; however, afferents from each eye are initially concentrated in appropriate areas. Between 52 and 72 days, afferents to the dorsal lateral geniculate nucleus are gradually segregated into nine terminal bands. Four are contralateral while five are ipsilateral. By 72 days, the ipsilateral component to the superior colliculus is clustered beneath the contralateral projection a deeper layer. Projections to four monocular visual areas—lateral posterior nucleus, dorsal terminal nucleus, lateral terminal nucleus, and nucleus of the optic tract—are established later than binocular visual areas, except the suprachiasmatic nucleus.The suprachiasmatic nucleus is the last to be bilaterally innervated even though it is situated closest to the optic chiasm. At the light microscope level a mature pattern of visual development is emerging by 72 days, although the eyes do not open until 140 days.
Thalamocortical connections in newborn mice
Authors: Crandall James E. , Caviness Verne S. 
Published: January 2005

AbstractThalamocortical axons reach the developing neocortex and become distributed within the cortical subplate during the third week of gestation. The present study is an analysis of the organization of connections that link thalamus and cortical subplate (corresponding to future layers V and VI) at birth. This age antedates the ascent of thalamic axons to contact cells of the supragranular layers, their principal targets in the adult cortex. At birth thalamic nuclear subdivisions are explicit; field‐characteristic cytoarchitectonic features, relating principally to the infragranular layers, delineate the majority of neocortical fields. The projection of principal relay nuclei upon the majority of fields of the cerebral convexity has been mapped by means of retrograde transport of HRP. Nucleus‐to‐field interrelationships as well as topologic order of the overall thalamic projection prove to be identical to that in the adult animal. The neonatal projection appears to be somewhat more divergent than that of the adult.
Laminar origins of visual corticocortical connections in the cat
Authors: Symonds Laura L. , Rosenquist Alan C. 
Published: January 2005

AbstractThe interconnections among visual areas in cat cortex were studied with respect to the specific laminae in which the cortically projecting neurons are located. Single injections of HRP were made through recording micropipettes into nine different visual areas. In 15 cortical areas the laminar distribution of neurons which were retrogradely filled with HRP was plotted. In this way we determined the laminar origins of the cortical projections to the nine separate cortical visual areas which were injected. There are three major observations. First, areas 17 and 18 are the only two visual areas in which layers II and III are the primary site of cortically projecting cells; in the other 13 areas the deeper layers of cortex provide a large percentage of such neurons. Second, within any one cortical area, cortically projecting neurons may be distributed among different layers; the specific layer depends upon the cortical target of those neurons. Third, any one cortical area receives projections from several different cortical layers, the specific layers being dependent upon the area from which the projection originates. An individual cortical area, therefore, contributes to several different cortical visual circuits, with each of these circuits defined by the laminar connections of its neurons.
The ultrastructure and organization of methionine‐enkephalin immunoreactive profiles in the interpeduncular nucleus of the cat
Authors: Kapadia Shanta E. , De Lanerolle Nihal C. 
Published: January 2005

AbstractAn ultrastructural analysis of the dorso‐intermediate (CDIZ) and dorsomedian zones (CDMZ) at the caudal end of the interpeduncular nucleus was undertaken. Serial vibratome sections were stained for metenkephalin‐like immunoreactivity by using the indirect antibody peroxidase‐antiperoxidase method of Sternberger, and ultrathin sections were examined electron microscopically, Met‐enkephalin‐like immunoreactivity was observed in two different types of somata in the two regions. The dendritic architecture of the dorso‐intermediate zone was characterized by the presence of many dendritic crests. A large number of these dendritic crests were immunostained for metenkephalin. A variety of terminals was also seen in the CDIZ and CDMZ and they are categorized according to their vesicular morphology into three classes. One class contained mainly clear round vesicles. The metenkephalin‐like immunoreactive (MELI) terminal profiles in both regions were of this class and contained small round vesicles which were less than 35 nm in diameter. These MELI terminals appeared in significant numbers, sometimes in close proximity to unlabeled somata and dendrites. The dorso‐median zone had, in addition, two more classes of terminals. One class was characterized by a large number of dense‐cored vesicles—class II, and the other group had a large proportion of flat clear vesicles—class III. The possible neurochemical identities of some of the unlabeled terminals in relation to the MELI dendritic structures are discussed in the light of known neurochemically established afferent projections to the CDIZ and CDMZ of the interpeduncular nucleus.