bluuebunny/crossref_metadata_2025_split huggingface dataset:
The synaptic glomerulus and the intrinsic neuron in the dorsal lateral geniculate nucleus of the cat
Authors: Famiglietti Edward V. , Peters Alan 
Published: December 2004

AbstractThe morphological characteristics of Class III, Golgi Type II neurons are analyzed in Golgi impregnations of the lateral geniculate nucleus (LGN) in the cat with special attention given to the complex dendritic appendages of these cells, the multilobed dendritic terminals. In addition, electron microscopic studies demonstrate the presence of presynaptic dendritic (ID) terminals as major components of synaptic glomeruli. Electron microscopic analysis of serial thin sections confirm the dendritic origin and the complex, multilobed nature of these terminals. An hypothesis is proposed identifying the ID terminal with the multilobed dendritic terminals of light microscopically identified Class III cells and the IA terminal, the “peripheral axon” of the glomerulus, with the axonal endings of all Golgi Type II cells.The Class III neuron has a short axon ramifying near the cell of origin. The axon terminates in boutons en passant and boutons terminaux: single, bilobed or “claw‐like” endings. Optic axons terminate not in “claw‐like” fashion, as previously thought, but in club‐shaped endings with scalloped silhouettes. The principal dendrites of Class III cells are characterized by long‐stalked appendages, often multilobed and occurring at the end of preterminal stalks 5 to 100 μ in length. One impregnated multilobed terminal studied in the electron microscope was found to innervate two adjacent glomeruli.The relationship of ID terminals to optic axon terminals and to other processes in synaptic glomeruli is analysed with the aid of the electron microscope. The ID terminal contains vesicles of the same size as those in presynaptic dendrites and makes small, macular synaptic contacts with other pre‐ and postsynaptic dendrites. ID terminals are the only elements in the LGN which synapse on others of their own kind, and are postsynaptic to all types of axon identified. As the only postsynaptic processes containing synaptic vesicles in the dorsal layers of the LGN, they support the conclusion that there are no axo‐axonic synapses in these layers. The ID terminal, the optic terminal and spinous dendrites originating presumably from geniculo‐cortical relay (GCR) cells, are seen to enter into a triadic relationship characteristic of the synaptic glomerulus in which the presynaptic dendrite synapses on the spinous dendrites and the optic terminal synapses on both dendrites. ID terminals reconstructed from serial sections communicate as “internuncial” presynaptic dendrites between optic central axons in adjacent synaptic glomeruli. IA terminals, which like ID terminals contain flattened vesicles, are presynaptic to ID terminals, as well as to postsynaptic dendrites, cell somata and axon initial segments.A model for the internuncial character of multilobed dendritic terminals and the potential for inhibition of Golgi Type II axon terminals is proposed, and theories about the function of Golgi Type II cells in lateral geniculate transmission are briefly considered.
Projection of the cochlear nuclei on the inferior colliculus in the cat
Authors: Osen Kirsten Kjelsberg 
Published: December 2004

AbstractThe present study was carried out in order to define the topographical organization and the cells of origin of the second order auditory fibers terminating in the inferior colliculus. The findings are based on anterograde fiber degeneration studies in Nauta preparations of adult cats following stereotactical lesions of the cochlear nuclei, and on retrograde cell degeneration studies in Nissl sections of kittens following transection of the ascending auditory fiber tracts. Both the dorsal and ventral cochlear nuclei were found to contribute fibers to the central nucleus of the contralateral inferior colliculus in a definite topographical order supporting the tonotopical organization of the inferior colliculus revealed physiologically by Rose, Greenwood, Goldberg and Hind (′63). The fibers leading to the inferior colliculus from the dorsal cochlear nucleus, undoubtedly originate in the pyramidal cells, while no definite conclusions could be drawn regarding the cells of origin of fibers derived from the ventral cochlear nucleus.
The effects of dorsal root lesions on Clarke neurons in cats of different ages
Authors: Loewy Arthur D. 
Published: December 2004

AbstractThe transneuronal effects of dorsal root lesions on Clarke neurons in cats of varying ages were studied. Chromatolytic and degenerative lumbar Clarke neurons were observed 5 to 15 days following dorsal rhizotomy from the lower thoracic to the coccygeal levels in the adult cat. Fiber degeneration was seen in the ipsilateral dorsal and dorsolateral columns in the cervical spinal cord. The finding of fiber degeneration in dorsolateral columns is supportive evidence for the hypothesis that the chromatolytic and neurofibrillar hypertrophic neurons are the result of ischemic myelopathy or direct surgical trauma to the lateral columns during the dorsal root surgery. Within 15 days post‐operatively, degenerative changes were not seen in lumber Clarke neurons when the dorsal root lesions were begun at the L 4 level.The effects of dorsal root lesions at different ages with an increased postoperative survival period were studied. Unilateral dorsal rhizotomies were done beginning at the L 4 level in kittens of two, four, and six weeks of age and adult cats. The degree of mean perikaryal and nuclear shrinkage in Clarke neurons was determined from Nissl preparations after these cells were partially denervated. The kittens of each age group showed approximately the same area reduction, and the adult cats did not show this shrinkage. It is deduced that the differentiation of Clarke neurons is almost completed by two weeks of age and that partial dorsal root denervation causes an arrest of growth rather than a transneuronal atrophy.
Blood supply to primitive mammalian brains
Authors: Gillilan Lois A. 
Published: December 2004

AbstractBrains of mammals are supplied by paired internal carotid arteries and also by paired vertebral arteries. The internal carotids distribute to the forebrain with its developing neopallium. The hindbrain with the expanding cerebellum and newly acquired middle cerebellar peduncle are supplied by the vertebral‐basilar system. In the opossum and armadillo the caudal rami of the internal carotid arteries resemble the patterns seen in submammals. The major source of blood to the posterior cerebral arteries is variable, coming from the basilar, the internal carotids or both. The ventral arterial circle (circulus arteriosus) is open as there is no anterior communicating artery in the two forms described. With the increase in size of the lateral lobes, the cerebellum of lower mammals is sufficiently larger and better developed to require a pair of inferior cerebellar arteries in addition to the phylogenetically older superior cerebellar arteries which originate from the basilar trunks. The latter are formed by the bifurcation of the basilar artery. The tectum in these forms is supplied by branches from the posterior cerebral and superior cerebellar arteries as well as tectal rami arising from the basilar trunks. Branches of the basilar artery going to the brainstem have a branching pattern similar to that seen in the submammals.The intrinsic patterns in both the opssum and armadillo are essentially like those observed in all vertebrates. They are remarkably constant and are easily recognized from one form to another. The arterioles penetrating the armadillo brain terminate in a continuous capillary plexus like the intrinsic plexuses observed in most of the submammals as well as in all mammals except marsupials. Arterioles penetrating the brain of the American opossum, as well as of all other marsupials, do not form a capillary plexus but terminate in capillary loops. Every penetrating arteriole is accompanied by a venule; each pair of vessels terminates in one or more capillary loops, thus constituting a true end‐system. However, as in the rest of its body, capillaries in the infundibular process and stalk, choroid plexuses, area postrema, supraoptic crest and subfornical organ are not paired but form freely anastomosing plexuses.The major developmental advance, i.e., the “mammalian shift,” in the blood supply to brains of primitive mammals is the addition of the vertebral arteries to supply the brainstem and an inferior cerebellar branch going to the cerebellum. The implications of these phylogenetic changes are discussed and related to the functional development.
Postnatal development of the cerebellar cortex in the rat. I. The external germinal layer and the transitional molecular layer
Authors: Altman Joseph 
Published: December 2004

AbstractThe multiplication of cells in the proliferative zone of the external germinal layer and the early steps in the differentiation of basket, stellate and granule cells were studied in the cerebellar cortex of rats aged 0, 3, 5, 7, 10, 12, 15, 21 and 30 days with histological, histochemical, autoradiographic and electron microscopic techniques. Between 0–9 days the proliferative zone has a constant depth of four to five cells; the bipolar cells in the underlying premigratory zone increase in depth during this period from 0–6 cells. Thereafter, there is a decline in the cell depth of both zones. In the premigratory zone there is a gradient in the length of the extruded processes of the bipolar cells (concentration of such profiles), the future parallel fibers. Presumably when the latter reach their final length, the cell body migrates downward and the parallel fiber becomes part of the upper zone of the molecular layer.Thus, parallel fibers are progessively formed on the surface of others from the bottom upward by a stacking process and the external germinal layer, as a consequence, is continually pushed upward. This design makes possible the assembly of a matrix of very long, thin and straight beams of horizontally oriented parallel fibers which pile up vertically according to their age. When synaptogenesis starts during the second week in the molecular layer the enlarging junctional processes produce a spurt in the growth of this layer.Basket cells which are formed in the pyramis on days 6–7 are arrested in the formative molecular layer because their processes are oriented at a right angle to the underlying bed of parallel fibers. Therefore, there is also a stacking of the cells of the molecular layer from the bottom upward as a function of time of onset of their differentiation. Parallel fiber synapses may be seen on differentiating basket cells as early as the seventh day, forming connections with these inhibitory interneurons before they synapse with spines of Purkinje cells.
The fine structure of glial cells in the chicken
Authors: Lyser Katherine M. 
Published: December 2004

AbstractThe glial cells of the chicken spinal cord and optic nerve, studied after aldehyde fixation, are comparable in fine structure to those of mammals and other vertebrates. Most astrocytes are characterized by an overall low density and cytoplasmic filaments, which vary in quantity and may occur in prominent bundles or may be scattered. Particular features in the chicken include the observations that the lumbar level of the spinal cord seems to be the only region, of those studied, in which astrocytes contain glycogen particles. Astrocyte processes with very dense cytoplasm, in addition to typical light ones, were observed, particularly in the glia limitans. Oligodendrocytes are characterized by a greater overall density, more extensive granular endoplasmic reticulum, more numerous microtubules, and absence of cytoplasmic filaments. The variations in cell type involve mainly the granular endoplasmic reticulum, ranging from short, scattered to long, stacked cisternae, and the texture of the nuclei.
Development of the cetacean spinal cord
Authors: Sinclair John G. 
Published: December 2004

AbstractEmbryos of dolphins and whales have been studied in sectional series ranging from 4.2 mm to 95 mm crown rump (CR) in length. The species include Stenella ceruleoalbus, Prodelphinius ceruleoalbus, Escherichtius robustus, Physeter catodon. Development of the spinal cord is similar in all these forms and differs from that of the seals and primates largely in the much slower expansion of the brain and eyes. By a 26 mm CR stage the lumbar swelling is relatively suppressed, but is still evident at the 95 mm CR length. This retention is based on the development of the tail muscles and the profuse autonomic system. The dorsal horn also is repressed, probably because of the relatively insensitive trunk skin. Paired intravertebral vessels form a blood reservoir, particularly in the thoracic region, but still large to lumbar levels.
Experimental reorganization of the cerebellar cortex. I. Morphological effects of elimination of all microneurons with prolonged x‐irradiation started at birth
Authors: Altman Joseph , Anderson William J. 
Published: December 2004

AbstractThe heads of Long‐Evans rats were irradiated from birth with a schedule of repeated doses of low‐level x‐ray which prevented the acquisition of the postnatally‐forming basket, stellate and granule cells. The absence of these microneurons led to several changes in the organization of the cerebellar cortex, studied at 30 days of age with light and electron microscopy. The somata of Purkinje cells were not strung out in a monolayer. Their primary dendrites were randomly oriented and arborized differently depending on the position of their somata in the depth of the cortex. Many Purkinje cell perisomatic processes, normally seen only in infants, were retained. Climbing and mossy fibers formed inconspicuous, symmetrical synapses with the somata and conspicuous, asymmetrical synapses with the perisomatic processes and dendritic thorns of Purkinje cells. Massive Purkinje cell dendrites with innumerable thorns made up much of the neuropil of the cortex. The dendritic thorns, in addition to forming true synapses, also established pseudosynapses with glial processes and synapses devoid of vesicles with the surface or the interior of Purkinje cell dendrites. The latter type of contact apparently led to autolysis of part of the dendrite, which was the only clear pathological phenomenon observed. These results indicated considerable autonomy in the growth of Purkinje cell dendrites, which arborized richly and sprouted innumerable small processes in the absence of parallel fibers, and formed postsynaptic dense membranes in contiguity with inappropriate processes, such as those of Purkinje cells or astrocytes.
Relationship between the septum and the cingulate gyrus in Macaca mulatta
Authors: Kemper Thomas L. , Wright Sanford J. , Locke Simeon 
Published: December 2004

AbstractThe relation between the lateral septal nucleus and the cingulate cortex of the monkey was investigated by the technique of retrograde cell degeneration. One hemidecorticate animal in which the gyrus cinguli was relatively preserved showed no cell loss in the lateral septal nucleus. Three animals, two with bilateral anterior cingulate gyrus lesions and one with a posterior cingulate gyrus lesion, showed cell loss in the lateral septal nucleus. These findings suggest that in the monkey there is a projection from the lateral septal nucleus to the gyrus cinguli.
The nucleus basalis of the pigeon: A single‐unit analysis
Authors: Witkovsky Paul , Zeigler H. Philip , Silver Rae 
Published: December 2004

AbstractSingle unit responses were recorded from neurons in the nucleus basalis of the pigeon. Two hundred and twelve basalis cells, from 23 birds, were characterized in terms of modality, receptive area and adaptive properties. Most basalis units (97%) fired spontaneously in bursts of a few spikes separated by one to two seconds of silence. All units were activated by light mechanical stimulation of the beak or buccal cavity. The units adapted rapidly to a maintained stimulus, but fired vigorously when the stimulating probe moved back and forth across the surface of the receptive area. Receptive fields fell into two clearly separable groups with respect to size: small fields, less than 15 mm2, generally clustered near the beak tips, and large fields occupying from one‐third to the entire beak surface. Both unilateral (ipsilateral or contralateral) and bilateral receptive areas were encountered. Nucleus basalis units could be driven electrically by stimulation of the beak surface or the main sensory trigeminal nucleus (PrV). The data suggest that n. basalis cells are particularly responsive to movement of food (grains) within the mouth and that this information is relayed by trigeminal afferents to the PrV, thence to the n. basalis via a partially decussating quinto‐rontal tract. The results are discussed in relation to the role of the n. basalis in the control of feeding behavior in the pigeon.
The mode of innervation of the dorsal lateral geniculate nucleus and the pulvinar of the rabbit by axons arising from the visual cortex
Authors: Giolli Roland A. , Pope James E. 
Published: December 2004

AbstractSections prepared by the Nauta method were used to study the fiber degeneration in the dorsal lateral geniculate nucleus and the pulvinar of the rabbit after lesions in the visual cortex, and sections processed by the Golgi and the Cajal methods provided the material needed to study the normal fiber architecture of these nuclei.Two distinct systems of fibers are recognizable in the dorsal lateral geniculate nucleus and in the pulvinar. One is a transverse system formed by the fiber bundles which run within these nuclei oriented in parallel with the optic tract; some of these bundles mingle with the fibers of the optic tract. The other is a longitudinal system whose fibers course perpendicularly to those of the transverse system. Lesions in the visual cortex produce degeneration within both of these fiber systems, in the geniculate nucleus as well as in the pulvinar. The degenerating transverse fibers are corticopretectal and corticotectal axons, and these send collateral branches into the longitudinal systems of these nuclei.The degenerating longitudinal fibers are of two types. One type consists of fibers which are fine in caliber, give rise to numerous short terminal branches, and degenerate early (undegenerated fibers showing this same morphology are identified in the Golgi preparations). These longitudinal fibers are the collateral branches of the degenerating transverse fibers and at the same time they represent the terminal portions of the fibers which provide the visual cortical input to the geniculate nucleus and the pulvinar. It is noteworthy that within the geniculate nucleus these terminal fibers run along the lines of projection for individual points on the visual field.The second type of degenerating longitudinal fibers is found in the dorsal lateral geniculate nucleus but not in the pulvinar. Its fibers are coarser and degenerate later than the longitudinal fibers described above, and they are probably geniculocortical axons undergoing retrograde degeneration.
The connective tissue coverings of leech peripheral nerves: Anatomical evidence for the absence of cerebrospinal fluid in the leech
Authors: Wilkinson Joyce M. , Coggeshall Richard E. 
Published: December 2004

AbstractThe central nervous system of Hirudo medicinalis is contained within a blood vessel, the ventral longitudinal sinus, but the nervous system is separated from the blood by the visceral endothelium. The visceral endothelium possesses many pinocytotic vesicles and basal infoldings and thus appears active whereas the parietal endothelium appears inactive. The junction between the visceral and parietal endothelia is abrupt. Peripheral nerves in this animal, as in vertebrates, are covered by endoneurium, perineurium, and epineurium. The endoneurium is continuous with the fibrous tissue of the segmental ganglia. The perineurium, consisting of a single layer of flattened cells that surrounds the peripheral nerve like a sleeve, is not continuous with the endothelium of the ventral sinus, but is separated from it by 5–10 microns. Therefore, at the point where the peripheral nerve joins the segmental ganglion, the extracellular spaces of the central nervous system, the peripheral nervous system, and the body wall are all confluent. Thus, there are only two compartments of the extracellular space in the leech: the blood, which is enclosed by the endothelia of the coelomic sinuses, and the extracellular fluid of the body, which includes the extracellular fluid of the nervous system. There seems to be no equivalent of cerebrospinal fluid in the gnathobdellid leech.
Effects of low‐level X‐irradiation on cat cerebella at different postnatal intervals: I. Quantitative evaluation of morphological changes
Authors: Anderson William J. , Stromberg Melvin W. 
Published: December 2004

AbstractWhole head fractionated doses of 200 r and 150 r were initiated postnatally in five experimental age groups (birth, 1‐week, 2‐week, 3‐week and 4‐week) and continued over a period of 14 or 20 days to prevent reconstitution of the external granular layer. Animals irradiated at birth displayed minor deficits in behavior, which included ataxia, tremor, hypertonus and dysmetria, while animals irradiated at 1‐week showed only mild symptoms of hypermetria. All other animals displayed no motor deficits. Animals irradiated at birth had smaller eyes and ears, a reduction in the size of the entire head and were susceptible to seizures. All animals were sacrified at 70 days of age. The cerebellum was found to be reduced in size and weight, the greatest deficit being seen in animals x‐irradiated at the very early ages. Newborn condition animals were found to have large compliments of interneurons in the molecular layer, an established internal granular layer, and Purkinje cells were found to have a normal orientation, position, and to be unreduced in number or size. Total granule cell deficits were found to range from 83% at birth to 29% at four weeks. Quantitative changes for the molecular layer, internal granular layer, medullary layer, Purkinje cell to granule cell ratio, and granule cell density, all depicted the greatest changes in the newborn, 1‐week and 2‐week conditions. This experiment confirmed that the critical period in the development at which damage would result in behavioral abnormalities was from birth to five days, while for neuroanatomical abnormalities, this critical period was from birth to 18 days.
Anatomical studies of a temporal visual area in the rabbit
Authors: Mathers Lawrence H. , Douville Arthur , Chow Kao Liang 
Published: December 2004

AbstractUsing Fink‐Heimer, autoradiographic and horseradish peroxidase techniques, the connections of a temporal visual cortical region of the rabbit were explored. The temporal visual area covers portions of areas T1 and T2, and is reciprocally connected with the posterior nucleus and suprageniculate nuclei of the thalamus. It was also shown that the temporal visual area projects to a similar region in the opposite hemisphere, and to intermediate laminae of the superior colliculus.The temporal visual area is discussed in comparison to other similar regions in the cortex of primate species. It is pointed out that recent evidence indicates visual areas in the occipital cortex of non‐primate species may be no less numerous and complex than those in primate species.