bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetically‐associated variations in the development of reflex movements and synaptic junctions within an early reflex pathway of mouse spinal cord
Authors: Vaughn James E. , Henrikson Charles K. , Chernow Charlene R. , Grieshaber Judith A. , Wimer Cynthia C. 
Published: May 2005

AbstractThe embryonic development of reflex forelimb movements produced by cutaneous stimulation of the forepaw was examined in five inbred strains of the house mouse, Mus musculus. A quantitative electron microscopic study of synapse formation between the neurons that comprise the spinal cutaneous reflex arc was also carried out on specimens from three of the strains subjected to reflex testing. This investigation provides evidence that there is significant genetically‐associated variability in the developmental timing of synapse formation within this disynaptic pathway and in the reflex behavior which it mediates. Specifically, it was found that C57BL/6J embryos had greater numbers of synaptic junctions in the reflex pathway at embryonic days 14–16, and they also showed reflex movements earlier than LP/J embryos. C57BL/6J embryos also showed a more rapid increase in the number of boutons during this embryonic period. CBA/CaJ embryos displayed a temporal pattern of development that differed from both C57BL/6J and LP/J. At E15, CBA/CaJ embryos were more similar to LP/J with regard to both reflex activity and synapse number, but by E16, CBA/CaJ values for both of these measures were more similar to C57BL/6J. On the basis of the data detailed in the text, we suggest that the strains differ in the following manner: C57BL/6J embryos develop boutons rapidly but appear to be relatively inefficient in the actual formation of synaptic junctions; CBA/CaJ embryos develop boutons at a slower rate than C57BL/6J but form synaptic junctions more efficiently; LP/J embryos develop boutons slowly and are also relatively inefficient in forming synaptic junctions. The genetic implications of — and some developmental processes which might be responsible for — the observed strain differences in the timing of synaptic development are discussed in the text.There was no detectable genetic variability of the basic sequence in which the neurons of the cutaneous reflex arc develop their synaptic connections. For all three strains examined, the data indicated that synaptic closure occurred in a retrograde sequence with respect to the direction that neurotransmission normally flows between the neurons of this pathway. This finding agrees with results obtained by other investigators from a number of diverse vertebrate species, and such a widespread lack of variability implies that a retrograde sequencing of synapse formation is involved in the development of specific neuronal connectivities.
The fine structure of pulse labeled (3H‐thymidine cells) in degenerating rat optic nerve
Authors: Skoff Robert P. 
Published: May 2005

AbstractThe ultrastructure of pulse labeled (3H‐thymidine) cells in rat optic nerve undergoing Wallerian degeneration is described. The study was limited to the first ten days after enucleation since cell proliferation during this interval is greater than in normal optic nerve (Skoff and Vaughn, '71). Approximately one‐third of the pulse labeled cells are astrocytes. The majority of the proliferating astrocytes are in a reactive state, having changed their normal fibrous appearance to one showing a paucity of filaments. Thirty percent of the pulsed cells can be classified as microglia. Only immature oligodendrocytes proliferate, and they account for less than 10% of the pulse labeled cells. About 30% of the labeled population are undifferentiated glial precursor cells. Electron microscopic autoradiographic data obtained from normal optic nerve and presented in this paper indicates that glial precursor cells which have divided shortly before enucleation continue to proliferate after it. The evidence suggests that recently formed glial precursor cells transform into phagocytes following enucleation. Less than 3% of the pulse labeled cells examined in this study are ultrastructurally similar to mononuclear leukocytes. The results of the present study together with previous studies of degenerating optic nerve indicate that most phagocytes in Wallerian degeneration are derived from proliferation of intrinsic glia rather than from an invasion of exogenous cells.
Spinal terminal fields of dorsal root fibers in the pigeon (Columba livia)
Authors: Leonard Robert B. , Cohen David H. 
Published: May 2005

AbstractThis paper describes the spinal pattern of brachial and lumbosacral dorsal root terminations in the pigeon. These are presented within the framework of the cytoarchitectonic analysis of the preceding report (Leonard and Cohen, '75).At the level of dorsal root section and immediately adjacent sections dense terminal fields were evident throughout the ipsilateral dorsal horn (Layers I–V), including the substantia gelatinosa. However, degeneration in the substantia gelatinosa was prominent only with short survival times. There were mediolateral differences in the density of degenerating material in the dorsal horn, as well as variations between the patterns at the cervical and lumbosacral enlargements. The general pattern of degeneration in the dorsal horn extended approximately three segments rostral and two segments caudal to the level of root section, becoming progressively less dense with distance from the level of rhizotomy. An exception to this was degeneration in the dorsal magnocellular (Clarke's) column where, following section of either brachial or lumbosacral roots, degeneration could be traced into the thoracic spinal cord. However, these ascending and descending projections upon the column at thoracic levels overlap minimally if at all.Degeneration was sparse in the intermediate zone and ventral horn (Layers VI–IX). It tended to concentrate centrally in Layer VI at the enlargements, and much of the degeneration ventral to this was interpreted as fibers en passage to the motoneuronal cell groups, Layer IX. Terminal fields in Layer IX were evident at both cervical and lumbosacral enlargements. They were largely restricted to the lateral motoneuronal cell group and were more prominent at cervical levels where degeneration was commonly observed around cell bodies and their proximal dendrites.As with the cytoarchitectonic organization of the spinal gray in the pigeon, the terminal fields of brachial and lumbosacral dorsal root fibers appear to have a pattern similar to that reported in the mammalian literature.
The pattern of projection of cortical areas 17, 18, and 19 onto the laminae of the dorsal lateral geniculate nucleus in the cat
Authors: Updyke B. V. 
Published: May 2005

AbstractThe projection of cortical areas 17, 18, and 19 onto the laminar part of the dorsal lateral geniculate nucleus was investigated with degeneration methods and with the autoradiographic axon tracing method. In agreement with previous accounts, degenerating cortical axons stained by the Nauta method were restricted to laminae A, A1, C and to the interlaminar zones. In contrast, adjacent sections stained with the Fink‐Heimer method showed fine dust like degeneration throughout all of the laminae of the nucleus. Comparisons of Fink‐Heimer degeneration resulting from lesions of area 17 with that resulting from lesions of areas 18 and 19 further suggested that the area 17 projection is heavier and more uniform than the projections from areas 18 and 19.Autoradiographic tracing of axons after intracortical injections of 3H‐proline provided detailed demonstrations of the cortical projection patterns that confirmed the Fink‐Heimer results. Following restricted injections of areas 17 or 18 the termination zones in the dorsal lateral geniculate nucleus consisted of columns of labeled tissue oriented perpendicular to the laminae of the nucleus. Area 17 was found to project heavily and uniformly throughout all of the laminae of the nucleus. The projection from area 18 also extended throughout all of the laminae of the nucleus, but was sparser and less uniformly distributed than that from area 17. Projections from area 18 distributed more heavily to the interlaminar zones and to lamina C than to laminae A, A1, C1, C2, or C3. A projection from area 19 to laminae C1, C2, and C3 was also demonstrated autoradiographically.
The organisation of the spinotectal projection. An experimental study in the rat
Authors: Antonetty C. M. , Webster K. E. 
Published: May 2005

AbstractThe spinal grey projects upon the contralateral superior colliculus via two overlapping pathways in the lateral funiculus. One, more ventrally placed, is the classical spinotectal tract, which crosses immediately in the spinal cord and remains crossed. The other, lying more dorsally, ascends homolaterally but is subject to delayed crossing in the brainstem (especially the intertectal) commissures to reach the contralateral colliculus. Both sets of fibers end only in the caudal half of the colliculus, predominantly in the stratum album intermedium. The projections from individual cord segments distribute in an ordered fashion as a series of transverse, overlapping bands, the cervical cord projecting most rostrally, the sacro‐coccygeal most caudally. Additional fibers, which distribute with less marked topography, end in the lateral extreme of the stratum griseum profundum and stratum album profundum.
Non‐randomness in the sequential formation of principal cones in small areas of the developing chick retina
Authors: Morris Valerie B. 
Published: May 2005

AbstractSystematic variation in the stage of development within small retinal areas could account for the overlap between the times of formation of the receptor types in the chick retina. The distributions of unlabelled and labelled principal cones in maps of the receptor mosaic, constructed from retinae exposed to tritiated thymidine during incubation, were analysed by grid analysis (Greig‐Smith, '64) and by two computer programmes. The computer programmes were generally more successful than grid analysis in detecting contagion in the distribution of unlabelled and labelled principal cones in the receptor maps. The contagion has been interpreted as evidence that the stage of development varies systematically in small retinal areas and that the overlap between the times of formation of the receptor types may be absent amongst small groups of cells.
Histochemical characterization of a neocortical projection of the nucleus locus coeruleus in the squirrel monkey
Authors: Freedman Robert , Foote Stephen L. , Bloom Floyd E. 
Published: May 2005

AbstractHistochemical evidence is presented for a catecholamine‐containing projection from the nucleus locus coeruleus to the neocortex in the squirrel monkey. The innervation of superior temporal gyrus has been examined in particular. Glyoxylic acid‐induced fluorescence shows an extensive arborization of fine, catecholamine‐containing fibers with prominent varicosities in all layers of the neocortex. The nucleus locus coeruleus is identified as a source of these fibers by both ortho‐ and retrograde axonal tracing techniques. After injection of horseradish peroxidase into the neocortex, labelled cell bodies are localized throughout the major portions of the locus coeruleus. Conversely, after microinjection into the nucleus locus coeruleus, tritiated proline is transported into the neocortex where it appears within fibers similar in distribution to those revealed by fluorescence histochemistry. Both transport techniques indicate that cortical projections of the locus coeruleus originate from both ipsilateral and contralateral nuclei.
The origin of efferent pathways from the primary visual cortex, area 17, of the macaque monkey as shown by retrograde transport of horseradish peroxidase
Authors: Lund Jennifer S. , Lund Raymond D. , Hendrickson Anita E. , Bunt Ann H. , Fuchs Albert F. 
Published: May 2005

AbstractThe retrograde transport of horseradish peroxidase has been used to identify efferent cells in area 17 of the macaque. Cells projecting to the lateral geniculate nucleus are small to medium sized pyramidal neurons with somata in lamina 6 and the adjacent white matter. The projection to the parvocellular division arises preferentially from the upper half of lamina 6, while that to the magnocellular division arises preferentially from the lower part of the lamina. The projection to both superior colliculus and inferior pulvinar arises from all sizes of pyramidal neurons lying in lamina 5B (Lund and Boothe, '75); at least the largest pyramidal neurons of lamina 5B send collateral axon branches to both destinations. Injections with extensive spread of horseradish peroxidase show that many cells of lamina 4B and the large pyramidal neurons of upper lamina 6 also project extrinsically but their terminal sites have not been identified.Other studies have indicated that cells of laminae 2 and 3 project to areas 18 and 19. Therefore every lamina of the visual cortex, with the exception of those receiving a direct thalamic input, contains cells projecting extrinsically. Further, each lamina projects to a different destination and from Golgi studies can be shown to contain cells with specific patterns of dendritic branching which relate to the distribution of thalamic afferents and to the patterns of intracortical connections. These findings emphasise the significance of the horizontal organisation of the cortex with relation to the flow of information through it and contrast with the current concept of columnar organisation shown in physiological studies.
Organization and development of brain stem auditory nuclei of the chicken: Tonotopic organization of N. magnocellularis and N. laminaris
Authors: Rubel Edwin W. , Parks Thomas N. 
Published: May 2005

AbstractExtracellular recordings of responses to tone‐burst stimulation were used to determine the tonotopic organization of n. magnocellularis (NM) and n. laminaris (NL) in hatchling chickens. NM cells show “primary‐like” response patterns to ipsilateral stimulation, and are arranged in dorso‐ventral isofrequency columns. Units responding to the highest frequency tones (about 4,100 Hz) are situated at the rostromedial pole of the medial division. Units with lower characteristic frequencies (CF's) are found at successively caudal and lateral sites, until extremely low CF's (<500 Hz) are represented dorsoventrally in the caudolateral tail of the lateral division. No evidence was found of auditory input to the region which receives projections from the macula lagena. NL receives polarized, binaural, excitatory input. Units have similar CF's and thresholds to tones presented to either ear. The tonotopic organization in NL matches that found in NM — high CF's rostromedially and low CF's caudal and lateral. Quantitative procedures were developed for relating CF to the position of a unit within either nucleus. These analyses account for 79% and 89% of the frequency variance found within NM and NL, respectively, and predict the CF of a neuron by its position within each nucleus.
The olivocerebellar projection in the cat studied with the method of retrograde axonal transport of horseradish peroxidase
Authors: Brodal Alf , Walberg Fred , Hoddevik Grethe H. 
Published: May 2005

AbstractThe distribution of labeled cells in the inferior olive of the cat has been mapped following injections of small amounts of horseradish peroxidase in the paramedian lobule of the cerebellum.The distribution of labeled cells was plotted in drawings of approximately serial transverse sections. The findings in each case were transferred to a standard diagram of the olive to facilitate comparison of cases.Previous studies of the distribution of retrograde cell loss in the inferior olive following cerebellar lesions (Brodal, '40b) showed that fibers ending in the paramedian lobule come from the caudal part of the ventral lamella of the principal olive. This was confirmed with the peroxidase method, but in addition three other separate and well circumscribed areas of the olive showed labeling: one in the dorsal accessory olive, another in the rostral part of the medial accessory olive, a third in the caudal part of the dorsal lamella of the principal olive (fig. 7). There is some degree of topical arrangement within the projection of each of these olivary areas to the paramedian lobule. It is particularly striking that the projection areas of the caudal one‐third of the lobule are different from and overlap only little with those of the rostral two‐thirds. On account of diffusion of the injected peroxidase solution in the folia it could not be decided whether the different olivary areas project to particular longitudinal zones in the paramedian lobule.The main findings can be correlated with the physiological observations of Armstrong et al. ('74). Some of the “paramedian” olivary areas are labeled also following peroxidase injections in other cerebellar parts, among them the nuclei interpositus anterior and posterior. The findings are compatible with the notion that olivocerebellar fibers branch to supply more than one cerebellar region.It is confirmed that the olivocerebellar projection, including that of the nuclei, is almost completely crossed. In the DISCUSSION it is emphasized that afferents from several sources converge on all four olivary regions projecting onto the paramedian lobule. The olivocerebellar projection obviously allows for divergence as well as convergence of impulses from the olive to the cerebellum.For further insight into the anatomical organization of the inferior olive, the entire olivocerebellar projection has to be mapped with the peroxidase method, and further studies of the afferents to the olive are needed. In such studies, as well as in physiological ones, it is essential that findings are described with meticulous reference to the topography of the olivary subdivisions.
An electron microscopic study of the neuromuscular junction in the myotomes of larval lamprey, Lampetra japonica
Authors: Nakao Taisuke 
Published: May 2005

AbstractThe neuromuscular junction in the myotomes of larval and adult lampreys, Lampetra japonica, was studied with the electron microscope. In larval lampreys of 26 days after artificial insemination, the myotome consists of triangular lamellae of muscle cell with their bases laterally and apexes medially oriented and placed one on the other. The lateral aspect of the myotome is covered by a layer of flattened cell, and the other aspect is covered by an external lamina which does not extend into the intercellular space between adjacent cells within a myotome. A bundle of thin axons was found in a depression at the middle of medial edge (apex) of each muscle lamella of the myotome and neuromuscular junction was formed here. No nerve endings were found at the myoseptal ends or at the lateral borders of the muscle lamellae. Enlarged axon terminals contained numerous clear vesicles with a few cored vesicles, mitochondria and neurofilaments. The presynaptic axolemma was separated from the postsynaptic sarcolemma by an interspace (50–55 mμ wide) with an interposed external lamina.In the trunk musculature of adult lampreys, nerve endings were found on the surface of the parietal fibers whereas they were seen on both the myoseptal ends near the myotendinous junction along the medial border of each central fiber. Thickening and enhancement in the electron density and accumulation of filamentous material on the sarcoplasmic surface of the postsynaptic sarcolemma were noted in both the larval and adult lampreys. Any other specific alterations were not found on both the pre‐ and postsynaptic membrane in the neuromuscular junctions of larval and adult lampreys.A brief comment was made on the relationship in development of the characteristic muscle units and patterns of the motor innervation in the larval and adult lampreys. The significance of the neuromuscular junction in the very young larvae reported here was also discussed in respect to the evolution of the neuromuscular junction, particularly in lower chordates, and it was presumed to be the most primitive pattern of innervation in the vertebrate skeletal muscle.
Formation of cockroach interganglionic connectives: An in vitro analysis
Authors: Provine Robert R. , Seshan K. R. , Aloe Luigi 
Published: May 2005

AbstractIndividual ganglia of the cockroach embryo (Periplaneta americana) were explanted on clean glass coverslips immersed in a chemically defined liquid medium and incubated for periods up to eight weeks. Substantial, straight interganglionic connections were formed between: (1) rows of ganglia arranged in the normal in vivo configuration; (2) rows of ganglia placed in abnormal orders; (3) rows of ganglia which never form connections in vivo because they occur singly in the embryo; and (4) rows of ganglia in natural sequences but which have had their rostro‐caudal axes rotated 90° in relation to the line of the row. Therefore fascicles and interganglionic connectives were formed without regard to normal in vivo relationships.Daily observations with a Nomarski microscope indicated that several processes are involved in connective formation. (1) Initial outgrowth is in a random, radial pattern. (2) Intersecting fibers from adjacent ganglia are deflected toward each others' perikarya. (3) Initially bowed fiber connectives are straightened, perhaps by increases in fiber tension or by fiber shortening which may be brought about by neuronal or extraneuronal (glial) processes. (4) Outgrowing fibers follow already established fiber pathways.The present results indicate that fiber‐fiber and fiber‐target interactions play a significant role in the formation of interganglionic connectives. In this system, the spatial relationships between ganglia determine the patterns and varieties of permissible neuronal connections. Thus, major, straight nerve trunks may be formed between adjacent ganglia which are growing out fibers on a glass surface submerged in a liquid medium which offers minimal orientation cues and provides a growth substrate vastly different and simpler than that encountered by outgrowing fibers in vivo.
Experimental reorganization of the cerebellar cortex. V. Effects of X‐irradiation schedules that allow or prevent cell acquisition after basket cells are formed
Authors: Altman Joseph 
Published: May 2005

AbstractIn Long‐Evans rats the area of the cerebellum was X‐irradiated with two schedules beginning on day 8 by which time the bulk of basket cells were formed. The shorter schedule of four successive daily doses of 200 r between 8–11 days was designed to allow some cell recovery, the longer schedule between 8–15 days was expected to prevent it. Neither of the schedules interfered with the differentiation of basket cells. Purkinje cells remained aligned in a monocellular layer and formed singularly long, upright stem dendrites which were surrounded by the descending collaterals of basket cell axons. This supported the hypothesis that the directed growth of Purkinje cell stem dendrite is promoted by morphogenic interaction with basket cells. The upright stem dendrites had few or no smooth branches where cell recovery was prevented or had few such branches where recovery occurred. It was postulated that the outgrowth of smooth branches is dependent on interaction with stellate cells which form after the acquisition of basket cells. The absence or scarcity of smooth branches did not prevent the formation of spiny branchlets which grew downward to establish synaptic contacts with the spared parallel fibers of granule cells formed before the start of irradiation. In the group with some granule cell recovery, spiny branchlets grew to a limited extent upward into the pile of parallel fibers formed after the irradiation.