bluuebunny/crossref_metadata_2025_split huggingface dataset:
Projections to the spinal cord from medullary somatosensory relay nuclei
Authors: Burton H. , Loewy A. D. 
Published: December 2004

AbstractDescending projections to the spinal card from the dorsal column nuclei were studied in the cat, rat and monkey with the retrograde horseradish peroxidase (HRP) technique, and in the cat with the autoradiographic anterograde axonal transport technique. Retrogradely labeled neurons were seen in the dorsal column nuclei after HRP injections at all levels of the spinal cord and additionally in the magnocellular division of the spinal caudalis nucleus of the trigeminal nerve after injections into cervical spinal segments in all three species. HRP‐positive neurons were predominantly located along the middle of the rostro‐caudal axis of the dorsal column nuclei and amongst the fusiform, triangular and polygonal cells that surround, especially ventrally, the cell nest zone containing thalamic relay neurons. The labeled neurons are densely concentrated in those portions of the dorsal column nuclei where most corticofugal and non‐primary afferent projections terminate and where the terminal distribution of primary afferent fibers is overlapping and diffuse. Previous studies have shown that most neurons in this middle and ventral region do not project to the thalamus or cerebellum. The majority of the cells in the dorsal column nuclei with descending axons or axon collaterals project by way of the ipsilateral dorsal columns, but some fibers project into the dorsolateral funiculus; the descending trigeminal fibers course in the dorsolateral funiculus. The terminal fields for these fibers in the cervical spinal cord include the lateral cervical nucleus, laminae IV and V, and possibly lamina I. These results indicate that the dorsal column nuclei may contribute to a feedback mechanism regulating the flow of sensory information ascending along other somatosensory spinal pathways.
The organization of the sensory and motor areas of cerebral cortex in the platypus (Ornithorhynchus anatinus)
Authors: Bohringer R. C. , Rowe M. J. 
Published: December 2004

AbstractThe organization of sensory and motor regions of the cerebral cortex has been studied in the platypus (Ornithorhynchus anatinus), of the order Monotremata. Comparisons were made with the organization found in the other representative of this order, the echidna, and with primitive species of eutherian and metatherian mammals. Evoked potential and single neuron studies revealed a large single area of somatosensory representation in the posterior region of the hemisphere, extending from an approximately mid‐sagittal position around to the region of the rhinal sulcus on the ventrolateral surface of the hemisphere. The mediolateral representation of contralateral body parts was consistent with the pattern in the primary somatosensory area of other mammalian species. No evidence of a second somatosensory area was found. Neurons with similar receptive fields were grouped in columns normal to the cortical surface and a highly ordered pattern of somatotopic representation was found. Within the large area of bill representation individual neurons had receptive fields which were often punctate and no more than 1 mm in diameter. They responded to dynamic components of tactile stimuli delivered to their receptive fields on the bill.Movements on the contralateral side of the body could be elicited by bipolar electrical stimulation over an area on the dorsal surface of the hemisphere which largely overlapped the somatosensory area, but extended further anteriorly towards the frontal pole of the hemisphere. Visual and auditory projection regions were found overlapping the somatosensory area in the posterior part of the hemisphere. The auditory area overlapped the visual area and appeared to be displaced posteromedially in relation to its position in other species, a displacement which may be a consequence of the large expanse of cortical area associated with the bill.The observation that a large proportion of cortical area is devoted to specific sensory and motor function in platypus corresponds with earlier findings in primitive eutherian and metatherian species. The platypus neocortex appears to represent a more primitive stage of cortical development than that found in the other member of the order Monotremata, the echidna.
The neural organization of the first optic ganglion of the principal eyes of jumping spiders (Salticidae)
Authors: Oberdorfer Michael D. 
Published: December 2004

AbstractThe first optic ganglion (FOG) of the principal eyes of jumping spider has been studied by both light and electron microscopy. Each FOG receives projections from the ipsilateral principal eye in a compact optic nerve. Some of the retinal axons, as they pass to the ganglion, cross in a chiasm within the optic nerve. The FOG is composed of a rind of nerve cell bodies which are unipolar cells giving rise anteriorly to second order nerve fibers in the central neuropile of the ganglion and posteriorly to processes which pass into the second optic ganglion. The neuropil is composed of neural and glial processes and of scattered glial cell bodies and it can be divided into a terminal zone and a fibrous zone. The terminal zone is the site of termination for all of the retinal axons. A unique feature of the retinal axon terminals is the presence of numerous fine post‐terminal processes extending away from the main portion of the retinal terminal. The fibrous zone is composed of second order nerve fibers with terminals in the terminal zone and it is continuous with a connective between the FOG and the second optic ganglion called the chiasm where the majority of the second order fibers cross.All of the synapses in the FOG are modified ribbon synapses and occur in the terminal zone within ensheathed synaptic glomeruli as dyads or triads. Large retinal terminals containing pleomorphic vesicles are presynaptic to smaller second order terminals containing spherical vesicles. Second order terminals are also presynaptic to retinal terminals in addition to forming serial‐like synapses with each other.
Acetylcholinesterase staining in subdivisions of the cat's inferior olive
Authors: Marani E. , Voogd J. , Boekee A. 
Published: December 2004

AbstractThe present paper describes a unique distribution of true AChE activity in the IO. In the dorsal accessory olive three areas with high AChE activity can be distinguished. The medial accessory olive can be subdivided into a caudal part which shows rostro‐caudally directed bands with different enzymatic activity, and a rostral part which shows a more uniform, medium activity. In the nucleus beta and the dorso‐medial cell column, AChE activity is low. The ventral and dorsal lamellae of the principal olive contain areas with high, medium, and low activity. The dorsal cap is strongly positive, while the ventrolateral outgrowth is negative for AChE.Enzyme distribution cannot be fully explained on the base of the known afferent and efferent connections with the IO. However, histochemical results provide evidence that generally supports a subdivision of the IO that mirrors these connections (Brodal, 1940; Armstrong et al., 1974; Boesten and Voogd, 1975; Groenewegen et al., 1975).
Ultrastructure of supraependymal cells and ependyma of hypothalamic third ventricle of mouse
Authors: Bleier Ruth 
Published: December 2004

AbstractThis study examines some ultrastructural features of the ependyma and supraependymal cells of hypothalamic third ventricle of the mouse in the region medial to the dorsomedial and ventromedial nuclei and dorsal part of infundibular nucleus. The brains of two males and 12 females in various phases of the estrous and reproductive cycle were studied.In the ependyma, large variations were found in the incidence of various organelles and surface features both among ependymal cells and among animals. These variations suggest that different ependymal cells have different functions and that the hypothalamic ependymal layer as a whole reflects in its morphology changing metabolic states of the animal.The main variations were found in the cytoplasm lying between the cell nucleus and ventricular surface. In some specimens the Golgi complexes were extensive and associated with many vesicles at the cell surface. Lipid‐like droplets may be large and abundant, sometimes bulging into the ventricle. Cytoplasmic surface protrusions may be large, irregular, and bulging with droplets, vacuoles or vesicles. These features, along with others, suggest a dynamic relationship between ependyma and cerebrospinal fluid (csf). Relations between tanycyte processes and neuropil are also described.Supraependymal cells varied in incidence, the largest numbers being found in a proestrous, an estrous and a lactating mouse. Their shape and nucleus, the abundance of dense bodies and lysosome‐producing structures and other features suggest that many supraependymal cells are macrophages. Noteworthy in some cells were bizarre imtochondrial profiles associated with Golgi, endoplasmic reticulum, lysosomes and lipid droplets (GERL and LERL)It is suggested that phagocytic supraependymal cells are engaged in processing the debris that results from changing metabolic activities, including secretion and exocytosis, blebbing and necrosis, of ependymal cells and also in the ingestion of foreign particles invading csf or ependyma.
Ultrastructural characterization of synaptosomes from neonatal and adult rats with special reference to monoamines
Authors: Kanerva Lasse , Tissari Anja H. , Suurhasko Birgit V. A. , Hervonen Antti 
Published: December 2004

AbstractThe crude mitochondrial fraction P2 and subfractions of it were prepared from the brain stem, hemispheres, hypothalamus and striatum of adult rats and from the hemispheres and brain stem or diencephalon‐mesencephalon and pons‐medulla oblongata of 1‐day‐old rats. Samples were fixed in glutaraldehyde‐osmium, KMnO4 or by Tranzer's triple fixation method (aldehydes‐chromate‐dichromate‐osmium) and examined by electron microscopy. With all these fixation techniques 80‐95% of processes in the adult samples were found to be mature synaptosomes. After incubation with either 10‐100 μg/ml of 5‐hydroxydopamine or α‐methylnoradrenaline, and after permanganate or triple fixation, monoamine synaptosomes, containing small granular vesicles were detected. They were found in all the brain regions studied and in the fraction P2 and subfractions C and D but only at a frequency of less than 1%. In samples from 1‐day‐old rats using the different fixatives, synaptosomes comprised 10‐30% of all processes. Nerve endings were at very different stages of maturation in sharp contrast to the rather uniform type of adult synaptosomes. They varied from processes still without any substructures to mature synaptosomes containing synaptic junctions. Monoamine synaptosomes containing small granular vesicles were detected after amine incubation and KMnO4 or triple fixation. Their frequency was lower than that in the adult. Most common were very immature terminals containing smooth endoplasmic reticulum and a very few small granular vesicles, indicating a very early appearance of the capacity to form small granular vesicles under experimental conditions. The immature terminals had all the characteristics of the growth cone and might partly have originated from growth cones at the tips of growing axons and dendrites. Less frequent were more mature synaptosomes containing a greater number of small granular vesicles and no longer any smooth endoplasmic reticulum. The crude microsomal fraction P3 was also examined in the adult brain regions and the brain stem of 1‐day‐olds. This fraction contained a small number of small agranular vesicles originating from cell bodies and nonterminal axons; their number was smaller in 1‐day‐old than in adult rats. The present results are in agreement with the high proportion of immature monoamine terminals in newborn rat brain detected earlier by fluorescence histochemistry.
Fornix system efferent projections in the squirrel monkey: An experimental degeneration study
Authors: Poletti Charles E. , Creswell George 
Published: December 2004

AbstractThe efferent projections of the fornix system have been studied in the squirrel monkey using modified silver staining techniques to delineate degenerating fibers and terminal boutons after inducing careful lesions of the subcallosal fornix and dorsal fornix.Subcallosal fornix projections, after supplying the medial and lateral septal nuclei, are traced via precommissural fibers to terminal degeneration in the nucleus of the diagonal band of Broca, nucleus accumbens, gyrus rectus, olfactory tubercle, medial and lateral preoptic areas, and medial hypothalamus. Degenerating precommissural subcallosal fornix fibers course with the medial forebrain bundle throughout the extent of the lateral hypothalamus, extending caudally to the medial mammillary nucleus with specific hypothalamic offsets to the tuberal region and nucleus intercalatus (“lateral cortico‐hypothalamic tract”). Subcallosal postcommissural fornix fibers are traced to terminal degeneration in the bed nucleus of the stria terminalis and medial preoptic and anterior hypothalamic structures (“medial cortico‐hypothalamic tract”); fornix column fibers disperse throughout the perifornical nucleus; these fibers more caudally supply nucleus intercalatus and medial mamillary nucleus. In the thalamus postcommissural fibers supply the nucleus reuniens, the paraventricular, anterior ventral, and lateral dorsal nuclei. In the mammillary nucleus a laminated radiation is described with some fibers extending caudally to the prerubral field.A “midline subcallosal stria,” derived from the subcallosal fornices, distributes fibers to the subfornical organ, the dorsal part of the medial septum, the precommissural fornix and especially the medial cortico‐hypothalamic tract.The dorsal fornix projection is predominantly pericallosal to the gyrus rectus and parolfactory area, with only a minor callosal‐penetrating contribution to pre‐ and postcommissural fibers.The composite projections of the hippocampal formation fornix system appear more extensive than those of the amygdala to basal forebrain, preoptic, and hypothalamic areas.
Patterns of degeneration in the external cuneate nucleus after multiple dorsal rhizotomies
Authors: Rosenstein Jeffrey M. , Page Robert B. , Leure‐DuPree Alphonse E. 
Published: December 2004

AbstractUnilateral, intradural dorsal rhizotomies (C3‐C8) were performed on adult rats to study the patterns of synaptic organization of ascending dorsal root fibers in the external cuneate nucleus (ECN). Animals were permitted to survive for periods of time ranging from 3hours to 12 days. Sham‐operated animals presented a morphology indistinguishable from that of normal, unoperated animals. In rhizotomized animals, degeneration was observed ipsilaterally at all survival periods. After postoperative survivals of 3 to 14 hours some terminal boutons displayed clumbing and diminution in numbers of synaptic vesicles and, in addition, degenerating myelinated axons were observed at this time. There was considerable degeneration in the neuropil between 24 and 48 hours postoperative. Two forms of degeneration occurred in axons and terminal boutons with comparable frequency: electron lucent degeneration and electron opaque degeneration. Reactive phagocytic glial cells contained degenerated masses, lipoid droplets, lysosome‐like structures and myelin fragments. After postoperative survivals of four to six days, lucent and opaque degenerating terminals were less numerous. Neurofilamentous degeneration was observed only occasionally. Unaltered synaptic membrane specializations were present and were usually abutted by glia. At 12 days postoperative, synaptic glomeruli and serial synapses were not seen. Invaginating dendritic spines were rarely seen. Bouton populations that remained unaltered were: small (0.3‐3.0 μm) boutons that contact dendritic shafts and somata, nodal synaptic boutons and boutons containing granular vesicles (80–100nm).
Development of outer segments and synapses in the rabbit retina
Authors: McArdle Craig Bryant , Dowling John E. , Masland Richard H. 
Published: December 2004

AbstractThe peripheral retina of rabbits aged 0 to 60 days was studied by electron microscopy. Ribbon and conventional synaptogenesis was studied with serial sections, and the density of synapses of the inner plexiform layer was measured on large (1,500μm2) montages.Photoreceptor and bipolar ribbon synapses seem to develop similarly in that processes of the prospective dyad or triad contact the presynaptic ribbon‐containing terminal one at a time. No statistically significant difference in the lengths of ribbon lamellae was found at 11 and 30 days. Conventional synapses appear to result from the aggregation of synaptic vesicles on one side of junctions that first existed as symmetrical membrane densities without vesicles. The length of the synaptic membrane specialization remains constant between 0 and 30 days.The density of inner plexiform layer conventional synapses remains at a low and roughly constant level from 0 to 9 days, after which there is an abrupt increase to a plateau at about 20 days. After nine days the density of ribbon synapses also increases, with an initially steep time course similar to that of conventional synapses. All subcategories of synapse studied (amacrine‐to‐amacrine, amacrine‐to‐bipolar, serial, and reciprocal) participate in the general increase between 9 and 20 days. Functional circuits of the inner plexiform layer thus seem to be assembled primarily during the second and third weeks of life.
Maturation of function in the developing rabbit retina
Authors: Masland Richard H. 
Published: December 2004

AbstractRetinas isolated from rabbits aged less than eight hours to adult were maintained in a flowing physiological medium. The electroretinogram or activity of single ganglion cells were recorded, and receptive fields were studied using stimulation of the retina with focused light. Retinal activity was stable for at least eight hours of incubation.Retinal ganglion cells are electrophysiologically active on the first day of life. They generate spontaneous bursts of action potentials at rates of 10 to 30 spikes/ sec, separated by silent intervals of one to six minutes. Maintained trains of action potentials follow elevation of the concentration of K+ in the incubating medium to 10 mM. Ganglion cells are also stimulated by acetylcholine, with apparent threshols equal to or lower than those of ganglion cells in adult retinas.The first response of the retina to light is a small cornea‐negative transretinal potential at day 6, presumably PIII of the electroretinogram. Responses of the ganglion cells are seen at eight days, but the responses are weak and adapt quickly to repeated stimulation. Many unresponsive cells are present. By ten days 60% of ganglion cells respond to light, and examples of mature receptive fields are present. Immature receptive fields at ten days fall into two rough classes, one characterized by a large responsive area with no antagonistic surround, and a second in which the surround can suppress the response to illumination of the center but can not itself cause a discharge. Immature fields are progressively replaced by mature ones, and by 20 days the qualitative organization of receptive fields is indistinguishable from adult.
Cytoarchitecture of the tectum mesencephali in two types of siluroid teleosts
Authors: Schroeder Dolores M. , Vanegas Horacio 
Published: December 2004

AbstractThe cytoarchitecture of the tectum mesencephali in the siluroid teleosts Bagrus and Ictalurus was studied by means of the Golgi method. These animals are known to have a restricted visual system and it seemed important to study whether this fact would affect the existence or the shape of the main neuron types which have been described for highly visual teleosts. It had been shown for a variety of teleosts that the retinotectal axons and terminals occupy almost exclusively the stratum opticum and the stratum fibrosum et griseum superficiale. The thickness of these strata in Bagrus and Ictalurus was found to be reduced. However, the main types of especially the vertically oriented neurons, such as the pyramidal, fusiform, large pyriform and periventricular neurons which have been described for highly visual species of teleosts, were also found in Bagrus and Ictalurus. Although their shape was somewhat distorted, these neurons, nevertheless, showed processes distributed to the same tectal layers as in highly visual teleosts and are accessible to horizontally distributed fiber systems such as marginal, telencephalotectal and commissural tectal fibers, as well as the retinotectal fibers. Nonvisual inputs appear to be considerably involved in the maintenance of the main neuron types in the siluroid tectum. For example, the pyramidal neuron's apical dendritic tree, which receives the excitatory input from the marginal fibers, is as well developed in siluroids as in highly visual teleosts.
Laminar differentiation of the hippocampus, fascia dentata and subiculum in developing rats, observed with the timm sulphide silver method
Authors: Zimmer Jens , Haug Finn‐Mogens Š. 
Published: December 2004

AbstractThe laminar staining of the rat hippocampal region with the Timm sulphide silver method is from studies on adult rats known to depend on the various fibersystems terminating in these laminae. In order to illustrate the development of these fibersystems the laminar differentiation of the Timm staining of fascia dentata, hippocampus and subiculum is presented for rats between 1 and 31 days old. Corresponding changes in cytoarchitectonics as revealed by thionin staining are briefly demonstrated.Even on the first postnatal day there are indications of the mature, laminar staining pattern, and between three and nine days all the laminae corresponding to the terminal fields of the major afferent and intrinsic systems appear. After 12 days only minor additions to the laminar pattern develop, but there are adjustments of absolute and relative dimensions of layers and fields, and also the staining densities of individual laminae change.These observations are in good correlation with the available information on both hippocampal neurogenesis and cytodifferentiation, and the few fiber tracing studies performed on the developing hippocampal region. Compared to the latter, which ideally marks only one system or one lamina per animal, the Timm method provides an excellent means for getting an overview of the general developmental situation at the different ages. Thus developmental gradients along septo‐temporal, medio‐lateral and basal‐apical axes are found, which should be heeded in future studies on hippocampal synaptogenesis.The observations are discussed in relation to current models for neuronal growth and formation of nervous connections.