bluuebunny/crossref_metadata_2025_split huggingface dataset:
The cortical projections of the mediodorsal nucleus and adjacent thalamic nuclei in the rat
Authors: Krettek J. E. , Price J. L. 
Published: December 2004

AbstractThe mediodorsal nucleus of the rat thalamus has been divided into medial, central and lateral segments on the basis of its structure and axonal connections, and these segments have been shown by experiments using the autoradiographic method of demonstrating axonal connections to project to seven distinct cortical areas covering most of the frontal pole of the hemisphere. The position and cytoarchitectonic characteristics of these areas are described. The medial segment of the nucleus projects to the prelimbic area (32) on the medial surface of the hemisphere, and to the dorsal agranular insular area, dorsal to the rhinal sulcus on the lateral surface. The lateral segment projects to the anterior cingulate area (area 24) and the medial precentral area on the dorsomedial shoulder of the hemisphere, while the central segment projects to the ventral agranular insular area in the dorsal bank of the rhinal sulcus, and to a lateral part of the orbital cortex further rostrally. (The term “orbital” is used to refer to the cortex on the ventral surface of the frontal pole of the hemisphere.) A ventral part of this orbital cortex also receives fibers from the mediodorsal nucleus, possibly its lateral segment, but the medial part of the orbital cortex, and the ventrolateral orbital area in the fundus of the rhinal sulcus receive projections from the paratenial nucleus and the submedial nucleus, respectively. All of these thalamocortical projections end in layer III, and in the outer part of layer I. The basal nucleus of the ventromedial complex (the thalamic taste relay) has been shown to have a similar laminar projection (layer I and layers III/IV) to the granular insular area immediately dorsal to, but not overlapping, the mediodorsal projection field. However, the principal nucleus of the ventromedial complex appears to project to layer I, and possibly layer VI, of the entire frontal pole of the hemisphere. The anteromedial nucleus does not appear to project to layer III of the projection field of the mediodorsal nucleus, although it may project to layers I and VI, especially in the anterior cingulate and medial precentral areas.A thalamoamygdaloid projection from the medial segment of the mediodorsal nucleus to the basolateral nucleus of the amygdala has also been demonstrated, which reciprocates an amygdalothalamic projection from the basolateral nucleus to the medial segment. The habenular nuclei also appear to project to the central nucleus of the amygdala.These results are discussed in relation to the delineation and subdivision of the prefrontal cortex in the rat, and to amygdalothalamic and amygdalocortical projections which are described in a subsequent paper (Krettek and Price, '77).
The specificity of re‐innervation by identified sensory and motor neurons in the leech
Authors: Van Essen D. C. , Jansen J. K. S. 
Published: December 2004

AbstractRe‐innervation of skin and muscle by identified sensory and motor neurons in segmental ganglia of the leech was studied using physiological techniques. After lesions of peripheral nerves, sensory axons which re‐innervated the skin always regained sensitivity to their original stimulus modality (touch, pressure or noxious stimuli). Motor neurons invariably re‐innervated the appropriate type of body wall muscle, such as longitudinal or circular muscle layers. Both sensory and motor axons usually returned to the appropriate region of the body wall (dorsal, lateral, or ventral) when regenerating after a nerve crush or cut. This capacity was lost, however, when growth along old nerve branches was prevented by evulsing long segments of the nerve. Re‐innervation usually occurred by way of growth of new axons all the way the periphery, but in a few cases reconnection with the surviving distal segment of the original axon had taken place. The specificity of reinnervation can be accounted for by a combination of selective growth along appropriate nerve branches and specific interactions with target tissues.
The postnatal development of neurons in the dorsal lateral geniculate nucleus of the rat: A Golgi study
Authors: Parnavelas J. G. , Mounty E. J. , Bradford R. , Lieberman A. R. 
Published: December 2004

AbstractThe postnatal differentiation of neurons in the dorsal lateral geniculate nucleus of the albino rat was studied using the Golgi‐Cox technique. At least four animals were used at postnatal ages 12 hours, 2, 4, 6, 8, 10, 11, 12, 13, 14, 15, 16, 18, 20, 24, 28, 35 days and adult.Presumptive thalamo‐cortical projection cells (Class A cells of Grossman et al., '73) and non‐projection, intrinsic neurons (Class B cells), are distinguishable at 12 hours after birth. At this stage both types of neuron are immature, with prominent growth cones at their dendritic extremities. Dendritic growth and differentiation appear to be complete by 18 days.Relay cells display two apparent “growth spurts” characterized by noticeable enlargement of the perikaryon and a marked increase in dendritic length and complexity. One occurs between days 4 and 6 and coincides with a period of enhanced synaptogenesis and gliogenesis: the second occurs between days 14 and 15, around the time of eye opening (day 14) and may be related to a further phase of increased synaptogenesis and gliogenesis (Karlsson, '67; Biesold et al., '76).Class B cells appear to “lag” behind class A cells in their initial postnatal differentiation, but also reach their mature condition by day 18.
Ultrastructural studies of the superior cervical trunk of the mouse: Distribution, cytochemistry and stability of fibrous elements in preganglionic fibers
Authors: Lewis Jon C. , Burton Paul R. 
Published: December 2004

AbstractThe ultrastructure of axons in the preganglionic cervical sympathetic trunk of the mouse is described with emphasis on the number, distribution and stability of fibrous elements in the axoplasm. Neurofilaments outnumbered microtubules in myelinated and non‐myelinated axons of all sizes, and the ratio of neurofilaments to microtubules in non‐myelinated axons at each point studied was fairly consistent and independent of axonal diameter. The density of neurofilaments and microtubules, however, was greater in axons of progressively smaller dismeter. In non‐myelinated axons and small myelinated axons neurofilaments were uniformly distributed throughout the axoplams resulting in minimum and maximum interfilament distances of 300 Å and 500 Å respectively; the spacing of fibrous elements within any one axon was dependent upon its diameter and position with respect to the superior cervical ganglion in the preganglionic trunk. The maximum interfilament distance was also found in large myelinated axons where neurofilaments, occurring in fascicles, were separated by distances of approximately 500 Å. Cytochemical staining of axons with lanthanum hydroxide, ruthenium red or alkaline bismuth delineated the delicate filamentous matrix interconnecting microtubules, neurofilaments and other organelles in the axoplasm. Alkaline bismuth stain was most intense in myelinated axons where heaviest deposition of reaction product was associated with neurofilaments. Treatment in vitro of the cervical sympathetic trunk with 5 × 10−5 M vinblastine sulfate dissociated microtubules and induced formation of crystalline arrays of “tubular” elements. A uniform center to center spacing of 250–300 Å was found for crystalloids in nonmyelinated axons; however, in myelinated axons the center to center spacing was not uniform and varied in the range 300–600 Å. Neurofilaments and their surface projections were unaffected by vinblastine. Fixation in the presence of lanthanum enhanced delineation of crystalloid elements. Exposure of 0–4°C for up to three hours had no consistent effect on microtubules or neurofilaments. In contrast, cold treatment disrupted the delicate axonal matrix and resulted in the formation of aggregates of coarse flocculent material in the axoplasm.
The ultrastructure of cutaneous type I mechanoreceptors (Haarscheiben) in cats following denervation
Authors: English Kathleen B. 
Published: December 2004

AbstractDenervation of specialized cutaneous mechanoreceptors (Haarscheiben or domes) in cats was followed after 20 and 25 days by the following alterations in receptor structure: (1) reduced numbers of Merkel cells, (2) Merkel cells degenerating in situ, (3) fewer dense‐core granules in the cytoplasm of Merkel cells, (4) an increased number of agranular dendritic cells and Langerhans cells in the dome, (5) the apparent phagocytosis of Merkel cells by Schwann and Langerhans cells, (6) fewer epithelial cell layers over the dome, and (7) a decrease in the number of transitional cells.Skin excised between the domes in the denervated nerve field appeared normal when compared to innervated skin, and it was considered unlikely that the alterations in dome structure were due to generalized nutritional changes in the skin caused by transection of sympathetic axons or to some other side effect of denervation. Since domes are formed in new locations on the skin after nerves have regenerated (Burgess et al.,1974), changes in dome structure following nerve transection are probably due to loss of the “trophic” influence of the nerves supplying the dome.
The vestibular complex of the american opossum Didelphis virginiana. II. Afferent and efferent connections
Authors: Henkel C. K. , Martin G. F. 
Published: December 2004

AbstractWe have demonstrated the connectivity of the opossum's vestibular nuclei using degeneration, autoradiographic and horseradish peroxidase techniques and have found it to be generally comparable to that reported for the cat. Apart from the primary input described in Part I of our study, the cerebellum provides the major source of afferent connections to the vestibular complex. Axons from the cerebellar cortex distribute mainly to vestibular areas which receive no primary afferent projections, e.g., the dorsal part of the lateral vestibular nucleus, the dorsolateral margin of the inferior vestibular nucleus as well as cell groups comparable to “f” and “x” In contrast, fastigial fibers show considerable overlap with primary vestibular input, particularly in the ventral part of the lateral nucleus, the central part of the inferior nucleus and the medial nucleus. Axons of fastigial origin also distribute to the superior vestibular nucleus, to subnuclei “f” and “x” and to the parasolitary region. Although spinal fibers are diffuse within the main vestibular nuclei, they ramify quite densely within subnucleus “x”. Most of th spinovestibular projection appears to arise in the cervical spinal cord of the opossum.Ipsilateral connections from the interstitial nucleus of Cajal and surrounding aras end predominantly, but not exclusively, in the medial vestibular nucleus. A crossed midbrain projection has been verified from the red nucleus to cell group “x” and the lateral part of the inferior nuclues, as well as to an area possibly comparable to cell group “z,” as described for the cat.In Part I of our study we have shown that the major targets of primary vestibular fibers are the central part of the superior nuclues, a portion of parabrachial complex possibly comparabale to subnuclues “y,” the ventral part of th lateral nucleus and the medial nucleus. All of these primary zones give rise to fibers supplying extraocular nuclei and surrounding areas (present study). The ascending midbrain fibers from the superior nucleus end mainly ipsilaterally, whereas those from the putative subnucleus “y” and the medial vestibular nucleus distribute contralaterally for the most part.Although the dorsal part of the lateral vestibular nucleus has no primary vestibular input, it does receive a major projection from the cerebellar cortex. This same region of the lateral nuclues projects to the spinal cord, but not to extraocular nuclei. The ventral part of the lateral nucleus, and perhaps the medial nucleus, also relay to the spinal cord. Additional projections from all vestibular nuclei can potentially affect multiple systems, including those innervating the spinal cord. Finally, commissural vestibular connections of the opossum are shown to arise within all four major nuclei.
Second order auditory pathways in the chimpanzee
Authors: Strominger Norman L. , Nelson Louis R. , Dougherty William J. 
Published: December 2004

AbstractSubstantial portions of the dorsal, and almost the entire posteroventral and anteroventral (Av) cochlear nuclei were aspirated unilaterally in a chimpanzee. Axonal degeneration was studied by the Fink‐Heimer method. The greatest amount of degeneration was followed medially from the region of Av into the lateral part of the trapezoid body. Degeneration also coursed around the superior surface of the restiform body and was traced into the dorsal and intermediate acoustic striae.Within the superior olivary complex, degeneration was distributed to: the ipsilateral lateral superior olive; laterally and medially oriented dendrites of the ipsilateral and contralateral medial superior olivary nuclei respectively (some periosomatic degeneration also was present bilaterally); the contralateral medial trapezoid nucleus; retro‐olivary and preolivary cell groups bilaterally. Abundunt degeneration passed into the contralateral lateral lemniscus and was distributed largely to its ventral nucleus. The contralateral central nucleus of the inferior colliculus was a major site of termination of ascending second order auditory fibers. The caudal tip of the ipsilateral ventral nucleus of the lateral lemniscus received abundant degeneration, but this diminished rostrally. The ipsilateral inferior colliculus contained a moderate amount of degeneration.A fair number of degenerated second order auditory fibers ascended in the contralateral brachium of the inferior colliculus and were distributed both to the principal and magnocellular divisions of the medial geniculate body. This pathway appears to represent a phylogenetic advance in the brain of the great ape.
The locust wing hinge stretch receptors. I. Primary sensory neurones with enormous central arborizations
Authors: Altman J. S. , Tyrer N. M. 
Published: December 2004

AbstractIn locusts a single‐celled stretch receptor (SR) neurone at the base of each wing monitors wing elevation and contributes to the control of the flight motor output. The central projections of these neurones are very complex but consistent in detail in the three species studied (Chortoicetes, Locusta and Schistocerca). The hindwing SR projects to the second and third thoracic ganglia, the forewing SR to the first, second and third thoracic ganglia. Both send fine axons into the abdominal connective.Within the ganglia each SR forms an extensive arborization, entirely ipsilateral and mainly in the dorsal neuropile, divided into medial, mediolateral, and lateral branches. The projections of the two ipsilateral SR neurones overlap almost completely in the second and third ganglia. There are recurrent loops between branches of a single neurone both within and between ganglia.Light microscope analysis shows apparent contacts between the SR neurones and flight motor neurones and other wing sensory afferents, as well as long inter‐neurones, other motor neurones and two types of multiaxonal neurones of unknown function. There are three groups of contacts between each SR and a flight motor neurone: laterally on the main branches, medially with the terminal twigs; and in the anterior dorsorriedial glomerulus, where the interganglionic recurrent branch also terminates. All contacts are ipsilateral except for those with the contralateral branches of the dorsal longitudinal muscle motor neurones.We suggest that the SR neurones are multifunctional. Differential information transfer could result both from the spatial distribution of synaptic connections with the motor neurones from filtering caused by low safety factors at branch junctions. Information in the lateral branching could be used for general excitation and control of firing frequency of the motor neurones; that in the medial branch for wing control and coordination.
Preterminal and terminal axon arborizations in the substantia gelatinosa of cat's spinal cord
Authors: Réthelyi Miklós 
Published: December 2004

AbstractExtensive terminal branchings of fine fibers in the substantia gelatinosa of Golgi‐Kopsch preparations of the adult cat spinal cord were subjected to a semi‐quantitative analysis. Transverse sections suggest that these fibers are probably unmyelinated primary afferent elements of dorsal root origin. In transverse sections these elements pass medially and ventrally and shortly disappear due to a change in orientation. Similar thin fibers in sagittal sections can be followed for several hundred microns as they give rise to side branches that also run mainly in a longitudinal direction. The side branches divide in turn to produce preterminal axon arborizations. The arborizations were distributed in 150 μ wide zones in the dorsal horn region corresponding to Rexed's lamina II. The end terminals are large bulbs, usually preceded by two to three equally large en passant enlargements. Seven to eight terminals stem from each side branch. The terminals and enlargements are arranged in narrow (16‐26μ m thick) sagittal sheets. The terminals of several side branches often converge upon a common region so that clusters of ter minals occur within the sagittal sheet. It is proposed that these observations are consistent with the substantia gelatinosa (lamina II) as the termination of unmyelinated (C) primary afferent fibers and that the latter are the only type of primary fibers ending in this portion of the spinal cord.
The substantia nigra of the rat: A golgi study
Authors: Juraska Janice M. , Wilson Charles J. , Groves Philip M. 
Published: December 2004

AbstractThree variants of the Golgi method were employed to examine the cell types, their dendritic fields and organization and azonal trajectories within the substantia nigra of albino and hooded rats. In both sagittal and coronal sections, large, medium and small neurons were classified on the basis of soma size, extent of dendritic fields and dendritic caliber. In general nigral cells have three to five primary dendrites that branch relatively infrequently. Some dendrites of all cell types have thinly scattered spines or varicosities.Small cells, found in all areas of the nucleus, have thin dendrites and small, nondirectional dendritic fields. These are considered to be interneurons. The medium cells found in pars compacta, presumed to be the dopaminergic cells of the nigroneostriatal pathway, send long dendrites into pars reticulata perpendicular to the course of pars compacta. In addition, these cells have a number of dendrites which remain in pars compacta. These cells have axons that run medio‐dorsaslly. No axon collaterals were detected. Both large and medium cells are found in pars reticulata. Cells in the dorso‐medial aspect of pars reticulata orient rostro‐caudally and roughly perpendicular to the course of pars compacta, while cells in the perpeduncular area show a strict orientation which is parallel to the crus cerebri. Some pars reticulata cells emit axon collaterals while others remain unbranched for their observable length. Both large and medium cells are also seen in pars lateralis. These cells send long dendrites ventrally into pars reticulata where they run parellel to the crus cerebri, while some shorter dendrites remain in pars lateralis.In total, the substantia nigra appears to have a layered organization: the superior layer is the cellular pars compacta, the second is the dorso‐medial area of pars reticulata where both pars compacta and pars reticulata dendrites run rostro‐caudally and dorso‐ventrally and the third layer is the perpenduncular region where dendrites from all areas run parallel to the crus cerebri.
Formation of hemi‐desmosomes during regeneration of crayfish nerve root sheath as studied with freeze fracture
Authors: Shivers Richard R. , Brightman Milton W. 
Published: December 2004

AbstractThe multilamellate glial sheath of mixed nerve roots of the sixth abdominal ganglion of crayfish contains numerous hemi‐desmosomes which appear to attach glial lamellae to material in adjacent extracellular clefts. These junctions, which have been described in detail in an earlier report (Shivers and Brightman, '76), are irregular in shape, punctuate and may be as large as 1 μm in diameter. Surgical interruption of sixth ganglion nerve roots results in regeneration of motor axons and their multilamellate glial sheaths. As the glial processes grow and re‐establish a highly organized axon sheath, hemi‐desmosomes appear. These junctions are present at the advancing edge of glial processes as well as on their lateral margins. Developing hemi‐desmosomes are characterized as a diffuse aggregation of 120–130 Å intramembrane particles which are present three weeks following nerve section. As growth and reorganization of the sheath proceeds, the intramembrane particles appear to aggregate and form irregular clusters of varying dimensions. Regenerating nerves freeze‐cleaved 8 to 16 weeks following surgery exhibit junctional particle aggregates similar to those in normal unoperated nerve roots. Origin of the intramembrane particles which comprise the junctional aggre gates in unknown. Perhaps they are synthesized de novo by the regenerating glial cells or, they may be remnants of complexes which became dispersed following surgery. This is the first report of a freeze‐fracture study of hemi‐desmosome plasticity in an invertebrate nervous system.
Postnatal maturation of neurons in the rabbit superior Colliculus
Authors: Mathers Lawrence H. 
Published: December 2004

AbstractThe superior colliculi of Dutch‐belted rabbits aged 1 to 30 days were prepared according to Nissl and Golgi techniques and examined in comparison to the neuronal populations in the adult. It was found that the laminar dimensions of the adult are attained at 15 to 20 days, presumably due to glial and dendritic enlargement. The largest neuron in the superficial gray, the vertical cell, was found to mature earliest and to display the least evidence of dendritic development postnatally. Its dendrites do elongate from 0 to 15 days, but there are no growth cones or other unusual dendritic configurations. The intrinsic neurons of the superficial gray, the piriform and stellate cells show more evidence of postnatal dendritic development. Particularly in the case of stellate cells, there are dendritic growth cones present at birth, and early in development spines are found on the soma and large dendrites. Only at 15 to 20 days do the dendritic arbors of these cells assume normal adult shapes and sizes. These and other observations suggest that there are two phases of postnatal cellular maturation in the upper layers of the superior colliculus, one involving the smaller “interneurons.” This phased maturation is compared with the known sequence of physiological maturation as studied by the method of receptive‐field mapping.