bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron microscopic features and proliferation of astrocytes in the corpus callosum of the rat
Authors: Mori S. , Leblond C. P. 
Published: December 2004

AbstractThe gold chloride sublimate method of Ramón y Cajal was used to stain astrocytes in the corpus callosum of 60–80 g male rats. The opacity of the metal‐stained astrocytes to the electron beam allowed their study in the electron microscope. It was thus found that metal deposits are absent from the nucleus but are present over two cytoplasmic structures: bundles of filaments and dense bodies.Once the features of astrocytes had been observed in metal stained preparations, it became possible to identify them in sections stained for electron microscopy by the routine uranyl‐lead sequence. The presence of filament bundles in the cytoplasm was the most useful diagnostic feature. Dense bodies also helped. The nucleus was relatively large and light with a very distinct, often irregular nuclear envelope. The rather light cytoplasm contained glycogen granules, with few ribosomes and cisterns of endoplasmic reticulusm. However, a few otherwise typical astrocytes had fairly dark nucleus and cytoplasm.After gaining experience with the electron microscope, it was possible to identify most astrocytes in the light microscope by their nuclear features. Counts of the frequency of astrocytes using either the light or electron microscope revealed that they make up about one quarter of the glial population of the corpus callosum.The main properties of astrocytes seemed to be: (1) plasticity of the cell surface, which infiltrates all available spaces around it; (2) apparent rigidity of the bundles of filaments present in the processes, where they may play a supporting role; and (3) ability of astrocytes to undergo division, as demonstrated both by the uptake of 3H‐thymidine into 1.7% of these cells and by the presence of mitotic figures.
Identification of preganglionic parasympathetic neurons in the sacral spinal cord of the cat
Authors: Oliver John E. , Bradley William E. , Fletcher Thomas F. 
Published: December 2004

AbstractThe preganglionic parasympathetic neurons in the sacral spinal cord of the cat have been demonstrated by retrogade changes following section of the pelvic nerve.Transection of the pelvic nerve twice, a week apart, was necessary to produce reliable signs of chromatolysis in the preganglionic neurons. Serial sections of the sacral spinal cord were made and the location of affected cells plotted.The sacral parasympathetic nucleus was located in the intermediate region of S‐2 and S‐3. The majority of the perikarya were located in the intermediolateral cell column, but a significant number were also found in the intermediomedial column.The distribution of afferent fibers in the pelvic nerve was demonstrated by chromatolysis in cells of the dorsal root ganglia. Retrograde changes were limited to the ganglia of S‐2 and S‐3 in five cats, while a few cells with chromatolysis were found also in the S‐1 ganglion of four cats.
Autoradiographic and histological studies of postnatal neurogenesis. IV. Cell proliferation and migration in the anterior forebrain, with special reference to persisting neurogenesis in the olfactory bulb
Authors: Altman Joseph 
Published: December 2004

AbstractThe properties and fate of the cells of the subependymal layer of the anterior lateral ventricle and its rostral extension into the olfactory bulb were examined. In one experiment, histological analysis was made of this structure in a large group of rats, ranging in age from newborn to adults. It was established that the ventricular subependymal layer and its rostral extension are present as proliferative and migratory matrices throughout the period studied, with relatively little reduction in size from birth to adulthood. In another, autoradiographic study, the proliferation and migration of cells of this system, and their destination and mode of differentiation, were studied in rats that were injected with thymidine‐H3 at 30 days of age and killed at intervals ranging from 1 hour to 180 days. There was a declining gradient in cell proliferation in a caudorostral direction from a high level near the lateral ventricle to the absence of cell proliferation in the olfactory bulb. The labeled cells that were present in high proportion near the lateral ventricle in the rats killed 1–24 hours after injection had further multiplied and moved to the middle portion of the “rostral migratory stream” by the third day, and were located in the subependymal layer of the olfactory bulb by the sixth day after injection. By the twentieth day the labeled cells disappeared from the subependymal layer of the olfactory bulb and were distributed throughout the internal granular layer. The differentiated cells were tentatively identified as granular nerve cells and neuroglia cells. These results established that the major target structure of cell production in the subependymal layer of the lateral ventricle in young‐adult rats is the olfactory bulb, with only moderate contribution made to the anterior neocortex and basal ganglia. It was postulated that the function of cell migration to the olfactory bulb is the renewal of its cell population.
The structure of the terminal ganglionic mass of the locust, Schistocera gregaria (forskäl)
Authors: Seabrook W. D. 
Published: December 2004

AbstractSections of the terminal ganglionic mass reveal a neuropile comprising four fused units corresponding to the eighth, ninth, tenth, and eleventh abdominal ganglia. Segmentally arranged groups of interneurons further illustrated the segmental nature of this ganglionic mass. Condensation of the component ganglia has resulted in a reduction in the number of commissures, the eighth ganglion retaining five of the original eight found in a simple ganglion, and each subsequent ganglion retaining four. There is a reduction in the number of discrete neuron groups and in the number of lateral interneurons coincident with the degree of condensation. Associated with the degree of condensation is a relocation of the motor neurons from the lateral ventral regions of the ganglion to the dorsal surface. One‐hundred‐five neurons have been traced within the terminal ganglionic mass.
Distribution of hippocampal mossy fibers in the rat. An experimental study with silver impregnation methods
Authors: Blackstad T. W. , Brink K. , Hem J. , June B. 
Published: December 2004

AbstractThe paper deals with the distribution of the axons that arise in the fascia dentata and go to the hippocampus proper. lesions were placed in the fascia dentata and degenerating mossy fibers were mapped by silver impregnation, mostly according to the method of Fink and Heimer ('67). The fascia dentata and the layer of mossy fibers in the rat form a curved and twisted structure extending from the level of the posterior aspect of the septum to the temporal tip. The horizontal serial sections used for this study were, therefore, in part interpreted by means of three‐dimensional reconstructions.Mossy fibers do not enter the fimbria at any point. Degenerating fibers can be traced to the limit between regio superior (CA 1) and regio inferior. This dentato‐hippocampal connection displays a pattern of precise localization, each level of fascia dentata projecting onto a restricted level of regio inferior. The bands of degenerated mossy fibers produced by lesions in the fascia dentata were largely oriented in the transverse direction (slightly in a temporal direction) and were somewhat wider distally than at the origin from the hilus. Very narrow bands were seen in a few animals with particularly small lesions.
The distribution of recurrent purkinje collateral synapses in the mouse cerebellar cortex: An electron microscopic study
Authors: Larramendi L. M. H. , Lemkey‐Johnston N. 
Published: December 2004

AbstractMyelinated fibers found in the lower molecular layer of the mouse cerebellum form synaptic enlargements of a uniform morphological appearance. Similar synapses have been observed to come from myelinated fibers in the upper granularlower Purkinje cell layer. Both have been interpreted as Purkinje collateral boutons. The study of the distribution of Purkinje collateral synapses revealed that one third formed the supraganglionic plexus in the lower molecular layer and two thirds formed an infraganglionic plexus in the lower Purkinje upper granular zone. In the molecular layer, basket cell somata and dendrites received the gratest number of Purkinje collaterals, while Purkinje dendrites and branchlets received relatively few. In the infraganglionic plexus, the Purkinje collaterals terminated on “very low basket” cells and upon a dense dendritic “thicket” belived to be contributed largely by basket cells.
Electron microscopic identification of three classes of oligodendrocytes and a preliminary study of their proliferative activity in the corpus callosum of young rats
Authors: Mori S. , Leblond C. P. 
Published: December 2004

AbstractIn recent electron microscope studies of the corpus callosum in 60–80 gm male rats, some of the cells were identified as microglia by staining with the weak silver carbonate method of del Rio‐Hortega, and others as astrocytes by staining with the gold chloride sublimate method of Ramón y Cajal. In the present work, the cells which did not belong in one of these two groups were examined in the light microscope using semithin sections stained with toluidine blue and in the electron microscope using thin sections stained with uranyl‐lead.These cells make up a large, somewhat heterogeneous group, but they have a few common features: regular nucleus, cytoplasm rich in ribosomes and microtubules, and a variable number of narrow, non‐branching fine processes of uniform diameter. Because of these features, the cells are all taken to be oligodendrocytes.Three classes may be described within this group of cells: (a) light oligodendrocytes, which are large cells with pale nucleus, a large nucleolus, a cytoplasm containing rather small organelles as well as many free ribosomes, and giving off numerous fine processes; they make up about 6% of the glial cells in the corpus callosum; and they undergo mitosis at a rapid rate; (b) medium‐shade oligodendrocytes, which are somewhat smaller cells with moderately dense nucleus and cytoplasm, containing well developed organelles, and giving off a fair number of fine processes; they make up about a quarter of the glial cells; and they undergo mitosis at a moderate rate; (c) dark oligodendrocytes, which are even smaller cells with very dense nucleus and cytoplasm, containing a prominent Golgi and structures referred to as lamellar bodies, and giving off very few fine processes; these cells make up about 40% of the glial cells; they do not undergo mitosis and probably arise from divisions of medium oligodendrocytes.
An experimental silver study of the ascending projections of the central gray substance and adjacent tegmentum in the rat with observations in the cat
Authors: Chi Carl Chungming 
Published: December 2004

AbstractThe ascending projections of the central gray substance and adjacent tegmentum in the rat and cat were studied with the Fink‐Heimer (1967) modification of the Nauta method. Following lesions of the circumaqueductal gray, degeneration was traced along the dorsal longitudinal fasciculus of Schütz, a reciprocal association pathway between the central gray and the hypothalamus, into the dorsal and posterior hypothalamus, midline and intralaminar regions of the thalamus, and the zona incerta of the subthalamus. Another group of fibers travelled ventrally from the central grey to reach the ventral tegmental area of Tsai; some of these fibers continued rostrally to terminate in the lateral hypothalamus. Other fibers distributed to the midbrain tegmentum as components of Weisschedel's radiatio grisea tegmenti. Lesions which extended into the adjacent tegmentum produced a larger quantity of degeneration than did lesions confined to the central gray, but the patterns of degeneration were similar in both cases. The ascending projections of the central gray in the rat and cat were found to have similar distributions but were slightly more massive in the cat.No evidence of fiber degeneration was detected in the ventromedial hypothalamus. Negative results, however, must be interpreted with caution, for they may be due to an excessively small caliber of axons and/or peculiar modes of axon termination in hypothalamic tissue.
Telencephalic projections of the nucleus rotundus in the pigeon (Columba livia)
Authors: Karten Harvey J. , Hodos William 
Published: December 2004

AbstractThe nucleus rotundus receives a massive ascending projection from the optic tectum. Stereotaxic lesions were placed in the nucleus rotundus and its efferent projections studied by means of the Nauta‐Gygax and Fink‐Heimer methods for degenerating axons and terminals. Efferent rotundal axons form the lateral part of the fasciculus prosencephali lateralis (FPL), pass through the lateral portion of the paleostriatum primitivum (PP) and augmentatum (PA) and enter the overlying ectostriatum.The ectostriatum was found to consist of at least two distinct cytologic regions: a central core (E) containing larger and more scattered cells and a peripheral belt with smaller, more densely packed neurons (Ep). Rotundal efferents terminate on the full extent of the central core of larger neurons. No evidence was found of any significant projection to the overlying periectostriatal belt or to the surrounding neostriatum. All portions of the central core of the ectostriatum receive projections from the nucleus rotundus. This projection is topologically organized on a rostro‐caudal axis relative to the nucleus rotundus. There was no indication of the existence of inter‐rotundal, rotundo‐tectal or rotundus to contralateral ectostriatal projections.These findings demonstrate the existence of a massive ascending visual pathway to the telencephalon, arising from the optic tectum and terminating in a cytologically distinct projection field within the telencephalon. The relationship of this pathway to known visual pathways in mammals and reptiles is discussed.
Photically evoked unit activity in the tectum opticum of the squirrel monkey
Authors: Kadoya Satoru , Wolin Lee R. , Massopust Leo C. 
Published: December 2004

AbstractVisually evoked unit responses of the tectum were studied in the squirrel monkey. The results showed that the superior colliculus had a definite functional laminar organization. Units responding to diffuse light were found in the upper part of the stratum griseum superficiale, units having antagonistically segregated receptive fields in the middle portion, and units sensitive to moving objects in the lower portion as well as in the stratum opticum. Retinotopic projection was also observed. The pretectal region contained mainly “tonic‐on” and “inhibitory” units. No specific localization was observed in the distribution of these units.
The distribution of neurofibrils coextensive with microtubules and neurofilaments in dendrites and axons of the tectum, cerebellum, and pallium of the frog
Authors: Potter H. D. 
Published: December 2004

AbstractCorrelation of electron micrographs with the results of a variety of reduced silver stains for light microscopy indicates that neurofibrils may be stained in locations where either neurofilaments or microtubules predominate, depending upon the procedure. Reduced silver techniques following fixation with alcohol or aldehyde solutions (Cajal's block method II, methods of Nonidez, Bartelmez, DeCastro, Bodian, Guillery, and Holmes) stain neurofibrils coextensively with neurofilaments (fnf) in myelinated axons, large dendrites, and synaptic boutons but do not stain neurofibrils in most radial dendrites of the tectum or parallel fibers of the cerebellum, where numerous microtubules but few neurofilaments are present. In the latter locations neurofibrils (tnf) are stained following primary fixation in silver nitrate alone (Cajal's block method I) or alcoholic silver nitrate (method Ic), with gold toning of the sections. The methods staining tnf are highly successful in showing the distribution and orientation of the parallel fibers and radial dendrites as well as other thin axons and dendrites in the grey matter including the archipallium. Even in regions containing fnf in numerous processes, it is clear that the majority of fibers in the adult frog brain contain only tnf.
Terminal degeneration and glial reactions in the lateral geniculate nucleus of the squirrel monkey after eye removal
Authors: Wong‐Riley Margaret T. T. 
Published: December 2004

AbstractYoung adult squirrel monkeys were subjected to unilateral or bilateral enucleation, and allowed to survive for varying periods of time. Transneuronal degeneration confirms previous studies that the homogeneous parvocellular mass actually has four hidden laminae. Electron microscopic studies show that the retinal (RL) terminals undergo three stages of degenerative changes after enucleation: neurofilamentous hyperplasia; increased electron density; and phagocytosis by glial elements. The time course of these changes is correlated with those of the Glees and the Nauta preparations. The other types of axons remain normal. Three types of neuroglial cells are found in the normal and degenerating LGN: Oligodendrocytes, astrocytes and a phagocytic glial cell type. The oligodendrocytes do not appear to participate actively in phagocytosis. The astrocytes undergo a filamentous hyperplasia during degeneration; they may engulf some degenerating terminals, and contribute to the formation of gliosis. The phagocytic glial cells proliferate during the degenerative process, and actively phagocytose both the dense terminals and the degenerating myelinated axons.
Nigrostriatal and nigrothalamic fibers in the rhesus monkey
Authors: Carpenter Malcolm B. , Peter Philip 
Published: December 2004

AbstractLesions in caudal parts of the substantia nigra (SN) produced in 11 monkeys were localized to lateral, medial and central regions. Resulting degeneration was studied by the Wiitanen technic in transverse and sagittal sections. Ascending nigral efferents project into Forel's field H where they divide into medial and lateral bundles. Fibers of the medial bundle terminate in portions of the ventral lateral (VLm) and ventral anterior (VAmc) thalamic nuclei. Quantitatively larger numbers of fibers project laterally dorsal to, and within, the subthalamic nucleus. These nigral efferents traverse the internal capsule and globus pallidus to enter the putamen (P) and parts of the caudate nucleus (CN). Nigral efferent fibers in the globus pallidus appeared entirely en passage. The location of degeneration in the putamen appeared related to the part of the SN destroyed. An apparent correspondence exists between: (1) lateral parts of SN and dorsal regions of P, and (2) medial parts of SN and ventral regions of P.The pars reticularis of SN gives rise to nigrothalamic fibers while nigrostriatal fibers arise from the pars compacta. Data suggest that reciprocal topographic relationships may exist between nigrostriatal and strionigral projections and that these fibers appear to form a closed feedback loop concerned with dopamine transport. Lesions in SN concomitantly interrupt large numbers of corticotegmental and corticothalamic fibers.
The termination of retinal axons in the pretectal region of mammals
Authors: Scalia Frank 
Published: December 2004

AbstractThe retinopretectal projection was investigated in the rat, mouse, rabbit and tree shrew primarily by means of the Fink‐Heimer technique. The experimental animals survived for varying periods of time following unilateral eye removal. The retinopretectal projection in each species was predominantly contralateral. A dense field of terminal degeneration was observed in the nucleus of the optic tract and in the olivary pretectal nucleus in each of the species. A less dense projection was observed for the posterior pretectal nucleus in each species. A sparse projection to the anterior pretectal nucleus was observed in the rabbit and tree shrew but not in the rat or mouse. A dense, ipsilateral projection to the olivary pretectal nucleus was observed in the rat, mouse and tree shrew. A sparse, ipsilateral projection was found in the anterior end of the posterior pretectal nucleus in the rat, mouse and tree shrew and in the posterior part of this nucleus in the rabbit. In the tree shrew, a small amount of terminal degeneration was found in the ipsilateral anterior pretectal nucleus. The nomenclature used here is uniformly applicable among the species described.
Retinal projections in the perch‐like teleost Eugerres plumieri
Authors: Vanegas Horacio , Ebbesson Sven O. E. 
Published: December 2004

AbstractAnatomical studies on the organization of the visual system of Eugeres plumieri have been initiated with an analysis of the distribution of retinal fibers in the brain. Twelve adult specimens were unilaterally enucleated. After postoperative survival periods ranging from six to 30 days, the fishes were perfused and the brains processed according to several modifications of the Nauta technique for the demonstration of degenerating axons and terminals (Ebbesson, '70). Although some terminal degeneration can be seen as early as six days, the degenerating fibers and terminals are best demonstrated in specimens with post‐operative survivals of 15 days or longer.The optic tract is entirely crossed and issues fascicles to the hypothalamus, nucleus geniculatus lateralis, nucleus opticus dorsolateralis thalami, nuclei pretectales, nucleus corticalis, and tectum opticum. The nucleus geniculatus lateralis is unusually large and well laminated, as is the optic tectum. The retinal input to the latter is distributed to, and terminates in, the stratum opticum and the highly differentiated stratum griseum et fibrosum superficiale. Debris of degeneration was also consistently seen in the stratum album centrale.
Patterns of cell and fiber distribution in the neocortex of the reeler mutant mouse
Authors: Caviness V. S. 
Published: December 2004

AbstractIn the neocortex of the reeler mutant mouse, there is inversion in the normal relative positions of polymorphic and pyramidal cells and of large with respect to medium‐sized and small pyramidal cells. Granule cells are concentrated at a near‐normal mid‐cortical level in the mutant. As in the normal animal, and despite cell malposition in reeler, the principal tangential fiber system lies in the zone of polymorphic cells. Large fiber fascicles, known from experimental studies to be principally thalamo‐cortical afferents, enter the tangential fiber system in the polymorphic cell zone of both reeler and normal neocortex. In the mutant these fascicles must traverse the full width of the cortex to reach this fiber system in its superficial location. In both normal and mutant animals single fibers, again principally thalamo‐cortical afferents, pass from the principal tangential fiber system to ramify in a fiber feltwork in the zone of granule cells. In the mutant these descend whereas in the normal animal they ascend. Also, as in the normal mouse, single fibers pass radially between all levels of the mutant cortex and the central white matter. Regional variations in the character, the pattern of distribution and the relative prominence of homologous cell and fiber elements are closely parallel in reeler and normal. This suggests that cell differentiation and the tangential organization of reeler neocortex are normal despite cell malposition in the mutant.