bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of the cortical degeneration in the visual regions of the temporal lobe of the monkey following section of the anterior commissure and the splenium
Authors: Zeki S. M. 
Published: January 2005

AbstractThe patterns of degeneration in the visual centers of the temporal lobe of the rhesus monkey following section of the anterior commissure and the splenium of the corpus callosum have been compared. Both commissural systems distribute interhemispheric fibres to the anterior part of the inferior temporal neocortex whereas the posterior part receives commissural fibres predominantly from the splenium.There were hints that the temporal visual neocortex may be further subdivided into discrete areas since the degeneration that follows section of either commissure does not fall within one continuous region but in patches, these patches being separated from one another either by cortex showing no degeneration or by cortex in which the density of degeneration is much reduced.
Contribution to the quantitative analysis of neuronal parameters: The effects of biased sampling procedures on estimates of neuronal volume, surface area and packing density
Authors: Mayhew T. M. , Momoh C. K. 
Published: January 2005

AbstractPhotomicrographs of motoneuron perikarya from the anterior horn of the rat cervical enlargement were analysed by various histometric and stereological procedures to compare the volumetric, volume‐to‐surface ratio, and packing density estimates obtained by several distinct sampling regimes. Information derived from unbiased motoneuron samples was compared with quantitative data derived from samples biased towards the nucleolus and from others containing cells above a minimal size (dimension‐biased samples). Nucleolarbiasing and dimension‐biasing techniques were found to produce only gross estimates of neuronal parameters. They produced substantial overestimates of cellular volume and perikaryal volume‐to‐surface ratio, together with significant underestimates of neuronal population density, perikaryal volume proportion and cytoplasmic volume/nuclear volume ratio. Unbiased sampling increased the amount of available material which could be analysed. It is concluded that meaningful estimates of these neuronal parameters are best obtained by the unbiased stereological approach, thereby giving a more accurate picture of the structural composition of nervous tissue.
Anterograde degeneration study of the superior colliculus in Tupaia glis: Evidence for a subdivision between superficial and deep layers
Authors: Harting J. K. , Hall W. C. , Diamond I. T. , Martin G. F. 
Published: January 2005

AbstractThe large, well developed superior colliculus of the tree shrew with its highly differentiated layers is ideal for analyzing the connections of individual layers. Our most significant finding concerns the differences between the projections of the superficial and deep layers. Lesions limited to those strata which receive projections from the retina and striate cortex (superficial 3 layers) result in terminal degeneration almost exclusively within the pulvinar, the pretectal area, and the dorsal and ventral lateral geniculate nuclei. In each case, the greatest amount of degeneration was present in the pulvinar, supporting previous suggestions that the tecto‐pulvinar pathway conveys visual information. In sharp contrast, lesions limited to the deep layers which receive multimodal input from nonstriate areas of the neocortex and from a variety of subcortical centers, produce terminal degeneration in entirely different thalamic nuclei — certain intralaminar nuclei, the subthalamic region, and a region homologous to the posterior nuclear group of Rose and Woolsey ('49). The deep lesions also result in terminal degeneration within the inferior colliculus, the parabigeminal nucleus, the reticulo‐tegmental nucleus, and the inferior olivary nucleus, as well as in the brainstem reticular formation. Finally, deep lesions produced scattered degenerating fibers in the motor facial nucleus. Our results favor a division of the tree shrew superior colliculus into superficial and deep portions based on strikingly different projection patterns and may be useful in resolving certain problems of thalamic homology.
An electron microscopic study of synaptic organization in the medial superior olive of normal and experimental chinchillas
Authors: Perkins Randolph E. 
Published: January 2005

AbstractThe medial superior olive (MSO) was studied in normal animals to determine the types of synaptic endings and their distribution over the surface of MSO neurons. Unilateral lesions were made in the anteroventral cochlear nucleus (AVCN) of experimental animals to determine the source of at least one synaptic type in the MSO.The surfaces of MSO neurons in normal animals were studded with three distinct types of synaptic endings distinguished mainly by the size of their synaptic vesicles. There were endings with large vesicles, 510 Å in mean diameter; endings with small vesicles, 380 Å; and endings with vesicles intermediate in size. 435 Å. The large vesicle ending typically was greater than 2 μm in maximum diameter. It appeared as the termination of a myelinated axon or as a swollen portion of a node and made multiple asymmetrical synapses. Large vesicle endings occurred exclusively on dendrites where they formed 85% of the synaptic endings. Small vesicle endings typically were less than 2 μm in diameter. They appeared as the termination of a fine unmyelinated axon and made only one symmetrical synapse. Small vesicle boutons occurred infrequently over the entire neuronal surface. Intermediate vesicle synaptic endings were similar to large vesicle endings except that they were present only on the cell body, axon hillock, and proximal portions of the dendrites where they formed most of the synapses.In AVCN lesioned animals degenerating myelinated axons and large vesicle synaptic endings were distributed to the lateral dendrites of the ipsilateral MSO and medial dendrites of the contralateral one. In addition, a few degenerating axons and large vesicle endings were found among the ipsilateral medial dendrites. The changes in the degenerating endings were characterized by an early proliferation of neurofilaments and swelling of the endings followed by collapse of the endings and increase in electron density, disappearance of filaments and synaptic vesicles, and phagocytosis of the degenerated endings by reactive glial cells. No degenerative changes were observed in the small and intermediate vesicle endings.The results of this study indicate that the more numerous large vesicle endings presynaptic to the MSO dendrites are the axon terminals of neurons in the AVCN. The persistence after lesions of the small and intermediate vesicle endings suggests that they arise from as yet unidentified sources.
Reciprocal point‐to‐point connections between parastriate and striate cortex in the squirrel monkey (Saimiri)
Authors: Tigges J. , Spatz W. B. , Tigges Margarete 
Published: January 2005

AbstractExperimental‐anatomical evidence is presented that in Saimiri two fiber systems project from area 18 upon area 17. Both systems terminate exclusively in layer I of area 17; in some other respects they exhibit characteristic differences.The fibers of the Horizontal System ascend from their origin in area 18 directly into layer I where they travel horizontally and parallel to each other to their termination site in area 17. This system is locally restricted since it connects only posterior area 18 with anterior area 17, i.e., it connects portions of both areas located near the representation line of the zero vertical meridian of the visual field.The fibers of the U‐fiber System arise from the supragranular layers of area 18. They reach their termination site in area 17 via the white matter from which they ascend perpendicularly into layer I. The U‐fiber system establishes a mirrorimage point‐to‐point connection between area 18 and area 17. This finding combined with the results of previous reports describing the similarly ordered association of area 17 with area 18 demonstrates a precisely organized reciprocal point‐to‐point connection between areas 17 and 18.
Investigation of glial cells in semithin sections. I. Identification of glial cells in the brain of young rats
Authors: Ling E. A. , Paterson Jean A. , Privat A. , Mori S. , Leblond C. P. 
Published: January 2005

AbstractThe staining of half‐micron thick Epon sections with toluidine blue provides a reliable method for the identification of glial cells. The diagnostic features of these cells observed in the corpus callosum of one‐month‐old rats are as follows: (1) Astrocytes have a very pale nucleus and cytoplasm; the nuclear envelope is sharply outlined by a thin chromatin lining with occasional chromatin beads; (2) Microglia have a small nucleus in which large, dark chromatin masses contrast with the nucleoplasm; the nucleus is round or elongated, and may be somewhat angular. The pericytes, which have a similar but usually crescentic nucleus, may be related to microglia. (3) Oligodendrocytes vary from pale to very dense and may be arbitrarily classified into three subgroups: The light oligodendrocytes are large pale cells with round to ovoid nucleus containing a prominent nucleolus and little or no condensed chromatin; the cytoplasm is extensive and appears pale, although less so than the nucleus. The medium shade oligodendrocytes are smaller cells that have an ovoid nucleus carrying small chromatin clumps and appearing moderately basophilic throughout; the cytoplasm is less extensive and somewhat darker than in the “light” subgroup. The dark oligodendrocytes are usually smaller than medium shade cells and often have an indented or angular nucleus with large chromatin masses; both nucleoplasm and cytoplasm are densely stained; the cytoplasm is often scanty and accumulated on one side of the nucleus.Semithin sections of the cerebral cortex show glia with similar features, with the exception of the astrocytes, which have a smaller but more basophilic cytoplasm than in corpus callosum.The cells of the subependymal layer of the lateral ventricle, when examined in semithin sections in the neighborhood of the corpus callosum, display a patchy, irregular nucleus and a scanty cytoplasm. Similar cells with a more regular nucleus are found outside the layer and in the corpus callosum; they are designated free subependymal cells.
Neuromuscular responses of sloths
Authors: Toole James F. , Bullock Theodore H. 
Published: January 2005

AbstractBecause sloths are among the slowest moving of mammals, it is of interest to determine whether the rate limiting factor is in their motivation, central nervous system, or their muscles.Muscle characteristics of ten sloths (Choloepus hoffmanni and Bradypus tridactylus) were studied by neuromuscular examination, electrophysiological, biochemical, and histological methods. Muscle twitch contraction averages 120 msec and one‐half relaxation time was 108 msec. Muscle contraction and relaxation are extremely sensitive to cold but were unaltered by calcium, quinine or procaine amide.Biochemical studies showed ATPase activity to be extremely low.Ultrastructure conformed closely to that of mammalian twitch fibers.Our data suggest that although muscle mechanics undoubtedly contribute to the slow movements of the sloth, they are not the only rate limiting factor.
The tectopontine projection in the cat: An experimental anatomical study with comments on pathways for teleceptive impulses to the cerebellum
Authors: Kawamura Koki , Brodal Alf 
Published: January 2005

AbstractFollowing lesions of different sizes and locations of the superior colliculus the distribution of degenerating fibers in the pontine nuclei was determined in the cat in Nauta and Fink and Heimer impregnated sections. The superior colliculus projects exclusively to most of the dorsolateral nucleus in the ipsilateral pontine nuclei. There appears to be some degree of topical arrangement in the projection.Three cases with lesions of the superior colliculus on one side and of the inferior colliculus, the cerebral auditory or cerebral visual areas, respectively, on the other side, permit comparisons between the projections of the superior colliculus with those from the other structures mentioned. The inferior colliculus projects onto the dorsolateral nucleus of the pons in an area which overlaps to some extent with that of the superior colliculus. Confirming more systematic studies of P. Brodal it is found that the pontine projection area of the auditory cortex to a large extent coincides with that of the superior colliculus, while the pontine projection area of the visual cortex is entirely different.These findings, together with other data from the literature, strongly suggest that the pathway for optic impulses to the vermal visual area of the cerebellum passes via the superior colliculus and the dorsolateral pontine nucleus. Direct tectocerebellar fibers or pathways via the reticular formation are scarcely involved in this process. Anatomically there is evidence for another route for visual impulses to the cerebellum: via the visual cerebral cortex and the pons to regions in the cerebellar hemisphere. This is in agreement with physiological findings and suggests that there may be at least two visual areas in the cerebellum.The anatomical data show that there are ample possibilities for an integration of optic, acoustic and other impulses in the superior colliculus as well as in its projection area in the pons.
A comparative study of spinal projections to the brain (except cerebellum) in three classes of poikilothermic vertebrates
Authors: Hayle T. H. 
Published: January 2005

AbstractLesions were made at varying levels in the spinal cords of a number of dogfish, rudd, and frogs. After a suitable survival period the resulting fibre degeneration was demonstrated by means of a silver impregnation technique. The findings have provided experimental confirmation of a profuse spinal projection to the reticular formation of the hindbrain in all three classes examined. These fibres were found to project to a constant sector of the reticular formation which closely corresponded not only between individual specimens of the same species, but between the three species, and which was situated ventrolaterally in the medulla oblongata. The density of this dengeneration was always greatest in the caudal brainstem and became progressively less at more rostral levels. All spinal projections to the reticular formation exhibited some degree of bilaterality, including those in specimens with lesions of hemisections or less. A spinotectal pathway was also demonstrated in certain specimens of dogfish. No involvement of cranial nerve nuclei was seen. These findings are discussed.
The effects of monocular lid suture upon the development of the lateral geniculate nucleus in squirrels (Sciureus carolinensis)
Authors: Guillery R. W. , Kaas J. H. 
Published: January 2005

AbstractThree infant squirrels had the lids of one eye sutured prior to eye opening. The animals were killed when they were adults and the cells in the lateral geniculate nucleus were studied after Nissl staining.The nerve cells within the deprived geniculate layers are smaller than the normally innervated cells. However, this asymmetry is seen only in the segment of the lateral geniculate nucleus that receives its inputs from the binocular portion of the visual field. Areas receiving from the monocular portion show no significant changes in cell size or cell packing. Thus, visual deprivation by itself does not affect perikaryal growth in the lateral geniculate nucleus. Growth is affected only in those parts of the geniculo‐cortical system in which the deprived cells have to compete with cells that are normally innervated.
The effects of age upon the main nucleus of the inferior olive in the human
Authors: Monagle Renee Dambiermont , Brody Harold 
Published: January 2005

AbstractThe neuronal population of the main inferior olivary nucleus was determined by complete cell counts of this structure in 18 human subjects of various ages. The age groups represent a progression from an immature infant of 23 weeks gestation to an 89 year old. The cell population was found to be lowest in the most immature infant (233,360), increasing in number up to the time of birth, the neo‐natal values being 327,330 for the three day old and 380,460 for the three month old. While minor cell fluctuations were noted in the specimens selected from the first to ninth decades, all values were relatively close to a post‐natal mean value of 363,784. A low value of 317,600 was found in an 82 year old and a high value of 405,580 in a 73 year old. Within comparable age groups the cell populations showed a similar pattern of distribution throughout the length of the nucleus.The structural evolution of the inferior olive during the lifespan is characterized by a period of growth from a calculated length of 7.1 mm before nine years of age to the 14.5 mm calculated average length for all the specimens in the series beyond the nine year stage.
The development of bergmann glia in mutant mice with cerebellar malformations: Reeler, staggerer and weaver. Immunofluorescence study with antibodies to the glial fibrillary acidic protein
Authors: Bignami A. , Dahl D. 
Published: January 2005

AbstractThe development of Bergmann glia has been studied by immunofluorescence with glial fibrillary acidic (GFA) protein antiserum in three mouse mutants with cerebellar malformations: reeler, staggerer and weaver. In none of these mutants was astrocytic differentiation delayed. The appearance of Bergmann glia in four‐day‐old reeler, staggerer and weaver mice was normal. Abnormalities of the neuroglial framework in the cerebellar cortex were observed later in development. In reeler mice immunofluorescent astrocytic fibers formed a mesh throughout the cerebellum. Radially oriented fibers were not observed. In staggerer mice Bergmann fibers shorter and more irregular than in littermate controls were still observed on the 14th day. Bergmann fibers were no more demonstrated by immunofluorescence in staggerer mice sacrificed later in development and little immunofluorescence was observed anywhere in the cerebellum of these animals. Heterozygous weaver and normal littermates were easily recognized in cryostat sections stained with toluidine blue, but the immunofluorescent pattern of Bergmann fibers was identical throughout development. Bergmann fibers were present and apparently not decreased in number in homozygous weaver mice but they had an immature appearance, i.e., they were shorter, less straight and less evenly spaced than in normal littermates of comparable age. In one‐month‐old homozygous weaver mice a dense mesh of immunofluorescent fibers with the general orientation of Bergmann fibers was present within the molecular layer of the cerebellum.
Origin of cerebellar climbing fibers in the rhesus monkey
Authors: Rivera‐Dominguez Manual , Mettler Fred A. , Noback Charles R. 
Published: January 2005

AbstractThe inferior olivary nuclear complex is generally considered to be the major source of climbing fibers to the cerebellum (Bell and Dow, '67). To test the validity of this statement, experiments using monkeys were designed in which the olivocerebellar fibers were transected in their course through the medulla to the contralateral hemicerebellum. After allowing for anterograde degeneration of these transected fibers, the cerebellum of each monkey was stained and examined for the presence and condition of climbing fibers. In each monkey olivocerebellar fibers were transected at one of three sites: (1) within the right inferior olivary nucleus in one rhesus monkey, (2) at the decussation of the olivocerebellar fibers, within the region of the raphe, in five monkeys and (3) in the left parasagittal plane, just lateral to the inferior olivary nucleus, in one monkey. No noticeable reduction was found in the number of silver stained climbing fibers associated with the Purkinje cells of each hemicerebellum after these lesions. None of the monkeys exhibited durable, specific cerebellar signs. On the basis of the histological evidence obtained from the above experiments, it is concluded that the inferior olivary complex is not the major source of climbing fibers to the cerebellum.Climbing fibers were readily identified in each of the sections examined. However, silver‐stained climbing fibers were not associated with many Purkinje cells in every one of these sections. There were 1.7 times more Purkinje cells without climbing fibers than those with climbing fibers. This ratio of 1.7 to 1 characterized normal cerebella as well as both hemispheres of the cerebella of the cerebella of the experimental monkeys.
Sequence of changes in neurofibrils (neurofilaments) induced in synaptic regions of bullfrogs by environmental temperature changes
Authors: Potter H. D. , Hafner G. S. 
Published: January 2005

AbstractProlonged exposure of bullfrogs (R. catesbeiana) to a cold (6°C) environment causes a progressive increase in numbers of neurofibrillar boutons in synaptic regions of the midbrain and induces thickening of perikaryal neurofibrils. Quantitative estimates of the numbers of boutons in lamina 5 of the optic tectum with controlled conditions for reduced silver staining, show the effects are graded with respect to both temperature and duration of exposure. Initial acclimation to 18°C results in few neurofibrillar rings but upon changing to 6°C the counts increase linearly with time to reach a 20 fold increase at three weeks. Rewarming to 18°C causes a return to the original numbers in less than one day.In electron micrographs ring‐shaped bundles of 100 Å diameter neurofilaments are coextensive with the cold induced neurofibrillar boutons of light microscopy; both are absent following acclimation to a warm environment. The cold exposure also causes large accumulations of β glycogen particles to appear in axons, dendrites, and synaptic knobs.