bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic organization of the nucleus gracilis of the cat. Experimental identification of dorsal root fibers and cortical afferents
Authors: Rustioni Aldo , Sotelo Constantino 
Published: January 2005

AbstractThe synaptic organization throughout the nucleus gracilis has been investigated in unoperated cats. Axon terminals of variable size can establish synaptic contacts with neuronal somata, dendritic processes, initial segment of axons or with other axon terminals at “complex synaptic arrangements.” Large boutons with rounded vesicles are regularly associated with smaller boutons containing flattened vesicles; the latter type of bouton forms frequently a double synapse being presynaptic to the large bouton and to the element postsynaptic to this (“complex synaptic arrangements”). Medium‐sized to small axon terminals of the “isolated” type contain primarily either rounded or flattened vesicles. These boutons are surrounded by a thin glial process which also wraps the postsynaptic element, mostly represented by a small dendritic profile. The “isolated” type of bouton seems to be more abundant in the rostral than in the caudal part of the nucleus. In all unoperated control animals altered axons and axon terminals are present. They are enlarged and display hyperplasia and dilatation of tubular profiles of smooth endoplasmic reticulum as well as proliferation of microtubules and various aspects of mitochondrial degeneration.In cats sacrificed 48 hours after section of lumbo‐sacral dorsal roots a high number of “dark” boutons are observed in various stages of degeneration. These terminals are identifiable with the large boutons containing rounded vesicles and postsynaptic to the smaller boutons with flattened vesicles. The morphology of dorsal root terminals in the nucleus gracilis is discussed in relation to that of primary afferent terminals in other central structures and to the functional aspects of axo‐axonic contacts.The sensori‐motor cortex was removed in another series of animals which were sacrificed after one to four days. As a consequence of such lesions cortical fiber terminals in the nucleus gracilis may undergo either the “dark” or the “light” type of degeneration. These terminals are of smaller size than those of primary afferents, they usually synapse on dendritic profiles of small diameter, are not involved in axo‐axonic contacts and seem to contain rounded vesicles. Therefore they can be identified with at least some of the small and medium‐sized boutons of the “isolated” type.
An electron microscopic study of the newt (Triturus viridescens) Optic Nerve
Authors: Turner James E. , Singer Marcus 
Published: January 2005

AbstractThe newt (Triturus viridescens) optic nerve appears to be more primitive than that of higher vertebrates. Only one type of glial cell is present and their stellate cell bodies are located in the core of the nerve. They send radiating processes to the surface to form a glial limitans beneath the meninges. The processes and their branches enwrap fascicles of naked axons and scattered myelinated fibers. The position and cytological character of these cells and their processes suggest that they are primitive ependyma. They subserve the functions of astrocytes and oligodendrocytes, in the latter case forming myelin wrappings. The position of their cell bodies is reminiscent of that of embryonic ependymal cells which surround the lumen of the optic stalk of vertebrates during eye development. Their cytoplasm is of medium to high cytoplasmic density, contains numerous cytoplasmic organelles and exhibit both microtubules and microfilaments.
Ablation study of the superior colliculus in the tree shrew (Tupaia glis)
Authors: Casagrande V. A. , Diamond I. T. 
Published: January 2005

AbstractThe main conclusions rest on the results obtained by ablating the superior colliculus in eight tree shrews. Additional animals either normal or with lesions of the superior collculus or striate cortex were studied to support or extend the basic findings. All eight tree shrews showed a profound loss of pattern discrimination which could not be attributed to some general factor such as inattention or an incapacity to learn. Thus, all succeeded in discriminating differences in the orientation of stripes but all failed to learn a habit based on discriminating the orientation of triangles. Two of the eight appeared normal in their capacity to orient toward, follow and track objects on the basis of vision. Six of the eight showed a remarkable unresponsiveness to visual stimuli manifested by a failure to follow, track, orient or even avoid what normal animals would regard as a threatening stimulus. This difference was clearly related to the extent of the lesion. In the two cases with normal visually guided behavior only the superficial three layers of the superior colliculus were removed. In the six cases with visual neglect the lesions included the deeper layers of the superior colliculus and invaded adjacent structures, notably the pretectum. It was concluded on the basis of differences between superficial and deep layers in their connections and in the behavioral effects of their ablation that the superior colliculus consists of at least two subdivisions.
Prenatal development of the human chief sensory trigeminal nucleus
Authors: Brown Jerry William 
Published: January 2005

AbstractThe development of the chief (main or principal) sensory nucleus of V was studied in 27 human embryos and fetuses, 7 to 30 weeks of menstrual age (19 to 261 mm CR length). Nissl and protargol silver preparations were used.The chief sensory nucleus develops by the migration of neuroblasts from the neuroepithelium lateral to the sulcus limitans. Migrations occur cAUdally at levels of the entering sensory root fibers and posterior trigeminal nucleus in the 18 mm, 7‐week embryo and later (24 mm, 8 weeks) at levels rostral to the motor nucleus of V. Cell differentiation within the nucleus progresses in a similar cAUdorostral sequence (cAUdally at 8.5 weeks, 27.4 mm and rostrally at 12.5 weeks, 65.5 mm) as well as in a dorsoventral sequence. Correlations between neuronal differentiation and functional activity indicate that the dorsal part of the chief sensory nucleus serves the maxillo‐mandibular divisions and the ventral part serves the ophthalamic division of V. In general, the ontogenetic development of the human chief sensory nucleus and the phylogenetic development of this nucleus are comparable.At 7.5 weeks (20.7 mm) a group of better differentiated cells appears cAUdally in the dorsomedial region of the primitive chief sensory nucleus (level of the posterior trigeminal nucleus). In 8.5‐week fetuses the cells of this group exhibit characteristics of functional neurons and form a distinct island. Neurons in this position remain the largest and best differentiated of those in the chief sensory nucleus throughout the fetal period studied. These large, dorsomedially located cells appear at progressively more rostral levels so that at 12.5 weeks they extend nearly to the rostral pole of the nucleus. It is suggested that these neurons constitute at least part of the supratrigeminal nucleus and that they serve as an integral part of the reflex arc concerned with mouth opening which occurs as a part of the total pattern response of the human fetus to perioral stimulation at 8.5 weeks and later with other reflex jaw muscle activity.
The telencephalon, diencephalon, and mesencephalon of the canary, Serinus canaria, in stereotaxic coordinates
Authors: Stokes Tegner M. , Leonard Christiana M. , Nottebohm Fernando 
Published: January 2005

AbstractA stereotaxic atlas of the telencephalon, diencephalon and mesencephalon of the canary, Serinus canaria, was prepared for use in anatomical and behavioral experiments. Canaries have a complex vocal and behavioral repertoire many of whose components are under hormonal control in the male, and are therefore useful for many physiological and anatomical experiments. They are available commercially, breed easily in captivity, are quite hardy and respond well to anesthetic and surgical procedures.The atlas consists of 30 frontal plates from the frontal pole to the level of the motor nucleus of the trigeminus. One sagittal plate is included for reference purposes. Six birds (three males and three females) with marking lesions were used to make the atlas. Their brains were embedded in albumin‐gelatin media, cut at 50 and 25μ and stained with cresyl violet for cell bodies, Weil stain for myelinated fibers and the Fink‐Schneider method for unmyelinated fibers. Plates were drawn from the cresyl violet series and labeled using all three stains.The completed atlas was tested for accuracy by making 12 small lesions in a number of predetermined discrete loci in several birds and evaluating their placement. Eleven of these lesions were found to be within the targeted structure. The results of this test, combined with the results of experiments in over 50 birds, have shown the atlas to be accurate in 80% of all cases.
Scanning electron microscopy of the subarachnoid space in the dog. II. Spinal nerve exits
Authors: Malloy John J. , Low Frank N. 
Published: January 2005

AbstractYoung dogs were perfused with buffered aldehydes. For scanning electron microscopy MICROFIL was injected to help prevent vascular collapse. The dura‐arachnoid was exposed leaving the nerve exits and rootlets intact. These were identified according to level and dissected free. Selected specimens were photographed at low magnification. Others were embedded in Epon 812 and sectioned for light and transmission electron microscopy. Similar specimens were prepared by critical point drying and palladium‐gold coating for scanning electron microscopy.Nerve roots pierce the dura through single exits (upper cervical, lower lumbar, sacral), or by exits separate for dorsal and ventral roots (lower cervical, thoracic, lumbar), or by multiple exits (cervical). Scanning electron microscopy reveals complicated tissue relationships chiefly involving arachnoid trabeculae. At the point of nerve root exits the arachnoid gives rise to numerous arachnoid trabeculae which form highly fenestrated sheets. These attach to blood vessels and nerve roots. A lateral recess occurs between dorsal and ventral roots (cervical, lumbar). Numerous macrophages are present on the various surfaces studied.
The topographical organization of the hippocampal projection to the septal area: A comparative neuroanatomical analysis in the gerbil, rat, rabbit, and cat
Authors: Siegel Allan , Edinger Henry , Ohgami Shoichiro 
Published: January 2005

AbstractAn experiment was performed to determine the origin of the projection from the hippocampus to the septal area in the subrimate mammalian nervous system. Lesions were made by aspiration or by radio frequency in 4 gerbils, 17 rats, 8 rabbits, and 7 cats. Survival times varied from 2–5 days. Tissues were stained principally with the Fink Heimer I method for identification of degenerating axons and their terminals. Following lesions destroying any one or more of the fields of the dorsal hippocampus of the gerbil, rat, rabbit, or cat, terminal degeneration was observed only in the medial septal area, olfactory tubercle, and adjacent portions of the diagonal band. In addition, lesions producing total destruction of all dorsal hippocampal fields also resulted in the presence of terminal degeneration restricted to the medial septal area. In contrast, superficial lesions of field CA1 of the ventral hippocampus produced terminal degeneration in the lateral septal area, nucleus accumbens, olfactory tubercle, and adjacent portions of the diagonal band. Similar findings were also observed following more widespread lesions of the ventral hippocampus which produced damage to other CA fields as well. Superficial lesions of the posterior crus of the hippocampus (i.e., a position midway between dorsal and ventral hippocampus) resulted in terminal degeneration localized to an intermediolateral region of the septum. Combined lesions of the dorsal hippocampus and fimbria produced widespread terminal degeneration in both the lateral and medial septum indicating that the axons contained within the fimbria arise only from the ventral hippocampus. Finally, lesions of the medial and lateral segments of the fornix of the cat produced terminal degeneration in the medial and lateral regions of the septum, respectively. These findings, collectively, indicate that the origin of the topographical projection to the medial and lateral septum are the dorsal and ventral hippocampus, respectively. This projection is unrelated to cytoarchitectonic fields within the hippocampus and is also invariant among the species considered in this study.
Some histochemical observations on the telencephalon of the bullfrog, Rana catesbeiana shaw
Authors: Northcutt R. Glenn 
Published: January 2005

AbstractThe histochemically determined distribution of acetylcholinesterase, monoamine oxidase and succinate dehydrogenase in the telencephalon of the bullfrog supports the classically recognized divisions of the pallium and subpallium. Analysis also corroborates the following gernerally recognized anuran‐amniotic homologies: anuran medial pallium to amniotic medial cortex anuran septal nuclei to amniotic septal nuclei, anuran striatum to amniotic corpus striatum. On topographical and histochemical criteria the ventrocaudal and basomedial portions of the anuran telencephalon are considered possible homologues to the mammalian amygdala. It is suggested that two divisions can be recognized: a pars lateralis which may be homologous to the mammalian cortico‐medial group. And a pars medialis which may be homologous to the mammalian baso‐lateral group. Further analysis suggests, particularly when viewed in the light of recent experimental anatomical studies, that the anuran lateral pallium consists of a pars dorsalis and a pars ventralis. The pars dorsalis may be the reptilian homologue of the dorsal cortex and the pars ventralis may be the field homologue of both the reptilian piriform cortex and the dorsal ventricular ridge.
Mechanosensory projections to cerebral cortex of sheep
Authors: Johnson John Irwin , Rubel Edwin W. , Hatton Glenn Irwin 
Published: January 2005

AbstractThis study mapped the mechanosensory projections to cerebral cortex of sheep, to complete earlier partial maps and to relate cortical projections to the organization previously determined in ventrobasal thalamus. Tungsten microelectrodes were used to explore thoroughly the walls and depths of cortical sulci as well as the previously studied gyral crowns, for regions responsive to mechanical stimulation of peripheral receptors, in sheep anesthetized with Dialurethane or nitrous oxide with either halothane or methoxyflurane. Earlier findings of a large projection from the ipsilateral mouth, lips and nose were confirmed. In addition, a small representation of the contralateral body and limbs was found which corresponds in most respects to the “second” sensory area (SII) of other mammals. In the primary (SI) sensory cortex, representations of the body and limbs were not found despite thorough fine‐grain mapping. Responses possibly representing a vestige of primary sensory cortex, and mechanosensory responses in claustro‐cortex, were also observed.
The structure and connections of the developing inferior olivary nucleus of the rhesus monkey (Macaca mulatta)
Authors: Robertson Lee T. , Stotler William A. 
Published: January 2005

AbstractStructural and morphological changes were examined in the inferior olivary complex of 25 rhesus monkeys that were 60 days gestation to three months after parturition. At different ages, one‐half brain stem was sectioned sagittaly, and when possible the symmetrical half was sectioned in either the coronal or the horizontal plane. Serial sections were stained by the silver reduction method of Stotler ('51).The olivary complex undergoes its major development between 60 and 129 days gestation when its length, cellular morphology, and afferent patterns resemble those of the adult organ. Structurally, the three major divisions—the principal nucleus, the dorsal accessory nucleus, and the medial accessory nucleus—can be identified at 60 days gestation. At that time, the medial accessory nucleus, the largest of the three, can be subdivided into a ventrolateral and a dorsomedial section; as it develops, it extends caudally and acquires a small cap of cells on its dorsomedial part. By 80 days, the dorsal lamella of the principal nucleus, initially smaller than the ventral, equals the ventral lamella in size and continues to enlarge until by 100 days it has developed two large sulci. The dorsal accessory nucleus, the smallest of the three divisions, initially has a distinct connection with the caudal part of the dorsal lamella of the principal nucleus but it is lost by 92 days.Major afferents to the inferior olive could easily be identified in the early fetal tissue—before the development of the dense neuropil. Afferents first arise from the lateral funiculus of the spinal cord at 60 days and project primarily onto the ventrolateral part of the medial accessory. As they develop, they gradually project more rostrally along the ventrolateral section, onto the dorsomedial section of the medial accessory, onto the caudal part of the ventral lamella, and along the caudomedial part of the dorsal accessory. At 92 days gestation the central tegmental fasciculus, most of which originates from the red nucleus projects into the rostral and later into the middle section of the dorsal lamella, into the rostral ventral lamella, and a few into the rostrolateral part of the dorsal accessory and to the rostral third of the medial accessory. A few fibers arising from the corticospinal tract enter the caudal section of medial accessory, and a few fibers project vertically from the dorsomedial tegmental region of the medulla into the medial section of the dorsal accessory.
Neurons of the dorsal lateral geniculate nucleus of the albino rat
Authors: Kriebel R. M. 
Published: January 2005

AbstractLight and electron microscopic observations were made on the dorsal lateral geniculate nucleus (DLGN) of 33 young adult male albino rats. Three variants of the Golgi silver impregnation technique were employed in the light microscopic studies.Neurons were classified into three categories based on location, dendritic pattern, and dendritic appendages. Type 1 and type 3 neurons were distributed throughout the DLGN. Type 2 neurons were located in the superficial zone. Dendritic appendages of type 1 and type 2 neurons indicated these cells may function as geniculocortical relay neurons. The type 3 neurons had lobulated dendritic appendages and an axon that terminated within the nucleus. Type 3 neurons may represent Golgi‐type II interneurons. Camera lucida drawings, photomicrographs, and electronmicrographs illustrate the characteristics of the three cell types. The literature on ultrastructural and neurophysiological findings may substantiate the presence of three neuronal types. Initially, the rat DLGN does not appear as elaborately organized as the nucleus observed in cats and primates; however, there are notable similarities in neuronal morphology and synaptology.
A stereotaxic atlas and technique for forebrain nuclei of the killifish, Fundulus heteroclitus
Authors: Peter R. E. , Macey M. J. , Gill V. E. 
Published: January 2005

AbstractA stereotaxic apparatus and technique for electrode placement in forebrain nuclei of the killifish, Fundulus heteroclitus, is described. An atlas of forebrain nuclei is given. A new nuclear region in the telencephalon is described.
Electrophysiological evidence for rod‐like receptors in the gray squirrel, ground squirrel and prairie dog retinas
Authors: Green Daniel G. , Dowling John E. 
Published: January 2005

AbstractSpectral sensitivities of the gray squirrel, Mexican and 13‐line ground squirrel and prairie dog were determined by electroretinography under both dark‐ and light‐adapted conditions. The dark‐adapted spectral sensitivity function obtained from intact eyes of these species peaks between 515—525 nm; however, when corrected for lens absorption or recorded from the lensless eye, it peaks near 500 nm and closely matches in shape a rhodopsin nomogram curve (λmax = 502 nm). Upon light adaptation all these retinas become relatively more sensitive to long‐wave stimuli (i.e., they show a small Purkinje shift). The light‐adapted spectral sensitivity function is broader than that obtained from the dark‐adapted eye, especially toward the longer wavelengths. We conclude that in all these species the dark‐adapted spectral sensitivity is mediated by a single, rhodopsin‐like photopigment and that light‐adapted sensitivity is mediated by two (or more) photopigments.
Synaptic patterns in the visual cortex of turtle: An electron microscopic study
Authors: Ebner Ford F. , Colonnier Marc 
Published: January 2005

AbstractThe part of turtle general cortex that receives afferent fibers from the dorsal lateral geniculate nucleus and that shows evoked potentials to light stimuli has been studied with the electron microscope. This cortex consists of an outer molecular layer, a perikaryal layer, and a subcellular layer lying on a row of ependymal cell bodies. Neurons in the perikaryal lamina are characterized by long spine‐bearing apical dendrites ascending through the outer molecular layer and short finer basal dendrites in the subcellular zone. Scattered neurons without apical dendrites occur in both the molecular and subcellular zones. Two types of dendritic spines can be distinguished. Some are large, have a complex irregular shape, contain a variety of membranous sacs and mitochondria, and occasionally, a single bundle of microtubules embedded in an electron‐dense background opacity. These large spines are the most common postsynaptic element in the outer third of the molecular layer, where they are located on the distal tips of the apical dendrites. Other spines are small, with a simple spherical distal enlargement that contains only electron‐dense fuzz. They are the most common post‐synaptic element in the lower two‐thirds of the molecular layer where they arise from the proximal portion of apical dendrites. Most synaptic contacts are found on the dendritic spines and are of the “round‐asymmetrical” type. Not infrequently “flat‐symmetrical” synapses are seen coupled to “round‐asymmetrical” contacts on individual large spines. The few contacts present on spine‐bearing dendritic shafts are of both types. Axo‐somatic contacts are mainly of the “flat‐symmetrical” variety. Thus the synaptic patterns on the principal cells of turtle visual cortex are remarkably similar to those found on pyramidal cells of mammalian neocortex. In addition, however, axon terminals, dendrites and glial (ependymal) processes were often seen to give rise to membranous pouches containing large vacuoles and invaginating into dendritic shafts or spines. Rarely, axon terminals were seen to form contacts, identical in appearance to synaptic contacts, on cell bodies in the ependymal lining. More frequently, unusual types of membrane differentiations were present at the site of apposition of the membranes of axon terminals and ependymal processes. They are interpreted as functional neuroependymal contacts.
Cytoarchitecture of the optic tectum in the nurse shark
Authors: Schroeder Dolores M. , Ebbesson Sven O. E. 
Published: January 2005

AbstractThe cytoarchitecture of the optic tectum of the nurse shark is described and related to the arrangements of afferents from retina, telencephalon and contralateral tectum. Its lamination is not pronounced when compared to tecta of most other non‐mammalian species but more comparable to those of mamals. The absence of highly differentiated cells such as pyramidal and true horizontal cells is perhaps correlated with the poor differentiation in general, including the apparent partial overlap of inputs. Some neurons near the midline were found to posses dendrites extending into the contralateral tectum.