bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some aspects of synaptogenesis in the spinal cord of the chick embryo: A quantitative electron microscopic study
Authors: Oppenheim Ronald W. , Chu‐Wang I‐Wu , Foelix Rainer F. 
Published: January 2005

AbstractWe have quantitatively examined the development of synapses in the ventral part of the lumbar spinal cord of the chick from embryonic day 4 until adulthood. The first synapses occur on day 4 and are of the axo‐dendritic type; they are invariably located adjacent to the border between the intermediate and marginal zones. Initially there are more synapses in the presumptive white matter than in the motoneuron neuropil, but this trend is later reversed; however, we found numerous axo‐dendritic synapses throughout much of the ventrolateral white matter even in the adult stage. The first axo‐dendritic synapses always contain spherical synaptic vesicles and have symmetric membrane specializations. By day 7 a few of these synapses were found to have mixed populations of spherical and flattened vesicles and asymmetric membrane specializations. After hatching there are still considerably more axo‐dendritic synapses with symmetric membrane specializations.Axo‐somatic synapses were first found on embryonic day 6 and were typically located on motoneurons lying adjacent to the marginal zone. These axo‐somatic synapses contain a few spherical synaptic vesicles and have symmetric membrane densities. Flattened synaptic vesicles were first found on day 10 and increased throughout development. Although a few axo‐somatic synapses with asymmetric membrane specializations were found at practically all stages, the symmetric type was always in the majority. An attempt was made to relate these observations with physiological, behavioral and neuroembryological findings from birds and other forms. For example, the fact that axo‐dendritic synapses always appear prior to axo‐somatic contacts would seem to rule out the role of somatic synapses in the initial induction of dendritic growth in the spinal cord.
The pulvinar nucleus of Galago senegalensis
Authors: Glendenning K. K. , Hall J. A. , Diamond I. T. , Hall W. C. 
Published: January 2005

AbstractThe present study was undertaken to analyze the connections of the pulvinar nucleus in a prosimian. The experiments, which rely on the Fink‐Heimer ('67) method for staining degenerating axons and their terminals, fall into two parts: first, the tracing of ascending tectal projections to the caudal thalamus and second, the tracing of projections from this thalamic target to the cortex. Large lesions of the superior colliculus resulted in dense degeneration in the caudal half of the inferior subdivision of the pulvinar complex. This pathway could be identified when the lesion was restricted to the superficial layers of the superior colliculus, signifying that it is a visual pathway. In general, the projections of the deep and superficial layers of the superior colliculus were distinct and in this respect Galago resembles Tupaia. The inferior pulvinar nucleus in turn projects to area MT, a conspicuous subdivision of the temporal cortex. The superior division of the pulvinar, in contrast to the inferior division, is not a major target of ascending projections from the superior colliculus and projects to the areas of the occipital and temporal lobe intercalated between areas MT and 17. When these results are compared with similar studies in nonprimates, notably studies of Tupaia, a striking difference in organization emerges. In Tupaia, and in distantly related mammals such as the squirrel, the target of the tecto‐pulvinar system includes area 18 adjacent to area 17. This feature is important since the two parallel projection systems seem to be related to each other in terms of the way in which the zero vertical meridian is spatially represented. However, in Galago the subdivision of the pulvinar receiving projections arising from the superior colliculus does not project to area 18. Area 18 is indeed the target of pulvinar projections, but these projections arise from that portion of the pulvinar which is not a recipient of ascending tectal projections. It is not easy to see how this primate organization, if indeed the Galago is representative of primates, evolved from the organization reflected in Tupaia.
An ultrastructural study of the red nucleus in the rat
Authors: Reid J. M. , Flumerfelt B. A. , Gwyn D. G. 
Published: January 2005

AbstractThe red nuclei of 14 adult male rats of the Wistar strain were prepared for electron microscopic study following perfusion with a mixture of aldehydes. Neurons of four size categories were identified in 1 μ Epon sections and their ultrastructural characteristics were studied in adjacent thin sections. Giant ( >40 μ) and large (20–40 μ) neurons are distinguished primarily by size and possess similar ultrastructural features: extensive areas of rough endoplasmic reticulum (RER), a prominent perinuclear Golgi complex, numerous mitochondria and pigment granules and a large, ovoid nucleus which occasionally contains intranuclear rodlets. Medium size neurons (20–25 μ) have less extensive, poorly organized RER and randomly distributed Golgi complexes. The nuclear envelopes of these cells fraquently show multiple invaginations and continuity with the RER cisternae. In small neurons (<20μ) the RER occurs as single or anastomosing strands while Golgi complexes and pigment granules are few. In both medium size and small neurons, aggregates of condensed chromatin are adherent to the inner nuclear membrane.Three main types of synaptic terminals may be distinguished in the red nucleus: (1) small terminals with flattened vesicles and symmetrical densties (F terminals), (2) small terminals with rounded vesicles and asymmetrical densities (RS terminals), and (3) large (10–15 μ) asymmetrical, rounded vesical terminals which form multiple contacts along their length (RL terminals). The small neurons receive both F and RS terminals on their dendrites and infrequently on their cell somes. The large and giant neurons receive F, RS and RL terminals on their somes and proximal dendrites and F and RS terminals on their distal dendrites. The somas and dendrites of medium size neurons receive both F and RS terminals but RL terminals do not lie in relation to them. Spine contacts are common throughout the nucleus and occur on both somas and dendrites.
Taste pathways to hypothalamus and amygdala
Authors: Norgren Ralph 
Published: January 2005

AbstractThe projections of a third order gustatory relay in the dorsal pons of rats have been traced using tritiated proline autoradiography and antidromic activation of pontine neurons from electrodes in the thalamus and amygdala. Labelled axons collect in the central tegmental tract and ascend to the thalamic taste area in the medial extension of the ventrobasal complex. The majority of the fibers remain ipsilateral, but a few cross in the rostral pons and midbrain. The largest crossing occurs at the level of the thalamic termination. Many fascicles of fibers continue rostrally by passing beneath the thalamic taste area, piercing the medial lemniscus, and spreading out along the dorsomedial corner of the internal capsule (IC). The terminal field at this level caps IC from the subthalamic nucleus down into the far‐lateral hypothalamus. Labelled axons gradually penetrate through the internal capsule, and ramify throughout the underlying substantia innominata. This terminal zone extends laterally into the rostral end of the central nucleus of the amygdala, which is densely labelled to its caudal extremity. At the caudal end of the amygdala labelled fibers are visible in one component of the stria terminalis. These fibers can be followed over the dorsal thalamus into a smaller, but equally dense terminal area in the dorsolateral bed nucleus of the stria terminalis. The electrophysiological data demonstrate that pontine gustatory units can be antidromically activated by electrodes located in or near the central nucleus of the amygdala. Since many of the same units can also be driven from the thalamic taste area, at least some of the axons traced autoradiographically probably convey gustatory information to the hypothalamus and amygdala.
Receptive fields of barrels in the somatosensory neocortex of the rat
Authors: Welker Carol 
Published: January 2005

AbstractPeripheral receptive fields of “barrels” in the somatosensory neocortex (SmI) of rats were determined with microelectrode recording and anatomical techniques. A method of flattening each hemisphere prior to embedding was devised so that the organization of layer IV could be seen through the full extent of SmI on a single section. All of the barrels in the rat are located within layer IV of SmI. Sinus hairs on the lateral and rostral face and furry buccal pad project to a continuous sheet of barrels in the head area of the contralateral SmI. The pattern of projections in this area indicates that each barrel receives information from one sinus hair. Large whisking vibrissae project to the largest celldense barrels and smaller non‐whisking sinus hairs project to smaller barrels that are relatively cell‐sparse. Barrels were also found outside of the head area in regions that receive projections from the forepaw and hindfoot. Receptive fields of these barrels are located on glabrous and hairy surfaces of the appendages that do not include any sinus hairs. Other parts of the body project to celldense areas of SmI that do not appear to contain barrels. Barrel subgroups and other somatotopic areas are separated by narrow barrel‐free zones. As a result of this pattern of contrasting cell densities, an outline of the rat's body is delneated within layer IV.
A somatotopic and functional representation of the respiratory muscles in the trigeminal and facial motor nuclei of the carp (Cyprinus carpio L.)
Authors: Luiten P. G. M. 
Published: January 2005

AbstractThe place of the cells innervating six most important respiratory muscles in the carp (Cyprinus carpio L.) were determined by means of the horseradish peroxidase technique. It was found that these muscles are represented in the rostral and caudal subdivisions of the trigeminal and facial motor nuclei. All connections were ipsilateral. The distribution of the various cell populations over the different subnuclei has been related to the function of the respective muscles in the respiratory cycle. On these grounds it could be concluded that muscles active in the contraction phase of respiration are represented in the rostral subnuclei, the expansion muscles in the caudal subnuclei. This arrangement appears to be a compromise between a somatotopic and functional organization.
Efferent connections of the caudate nucleus in the virginia opossum
Authors: Mickle John Parker 
Published: January 2005

AbstractThe efferents of the opossum's caudate nucleus were investigated by charting the fiber degenerations produced by electrolytic lesions in various parts of this nucleus. By the aid of a modified Fink‐Heimer procedure, degenerating fibers were traced from each of the lesions to the small globus pallidus in which they appeared to be distributed in an orderly dorsoventral pattern. Fibers From all lesion sites in the caudate nucleus were found to terminate in the entopeduncular nucleus. In the substantia nigra, caudatofugal‐fiber degeneration was confined in all cases to the rostral part of the pars reticulata, and was densest in the medial one‐half of this nucleus. Only from lesions in the ventromedial part of the caudate nucleus could degenerating fibers be traced to the nucleus ansae lenticularis. No fiber degeneration could be traced rostrally from the lesions, or to the putamen, red nucleus, subthalamic nucleus, or pons.
Postnatal maturation of subcortical projections from the prefrontal cortex in the rhesus monkey
Authors: Johnson Thomas N. , Enger Rosvold H. , Galkin Thelma W. , Goldman Patricia S. 
Published: January 2005

AbstractOrbital and dorsolateral prefrontal lesions were performed on a series of rhesus monkeys at 2, 6, or 24 months of age. The consequent degeneration in the efferent pathways from these cortical regions to the caudate nucleus, the dorsomedial nucleus of the thalamus and adjacent structures was studied at 5‐ and 15‐day survival times by a modification of the Nauta‐Gygax method for tracing degenerating fibers. Following dorsolateral lesions, considerable numbers of black‐impregnated degenerating fibers were found in the parvocellular division of the dorsomedial nucleus and in the fiber bundles of the internal capsule and the subcallosal fasciculus at all ages. In contrast, the degree of Nauta‐Gygax degeneration in the anterodorsal sector of the head of the caudate nucleus was age‐dependent: degenerating fibers were found in increasing numbers from two months of age, when virtually none could be detected, to 24 months of age, when they appeared in relatively dense concentration. Similar results were obtained following orbital prefrontal lesions at the same three ages: degeneration in the magnocellular division of the dorsomedial nucleus of the thalamus and in the internal capsule were not related to age, but anterograde degeneration in the ventral and lateral capsular region of the caudate increased substantially with advancing age. Negative results with the Nauta‐Gygax technique in very young animals may not signify an actual absence of the connection in question, but our findings, together with those of other studies employing silver degeneration methods, at least suggest that in the primate, certain cortical efferents undergo maturational changes during postnatal life, a fact which may be related to the differential behavioral consequences of cortical injuries at different stages of development.
The facial motor nucleus of the opossum: Cytology and axosomatic synapses
Authors: Falls William M. , King James S. 
Published: January 2005

AbstractThe normal cytology and synaptic organization of the opossum facial motor nucleus was determined by use of Nissl preparations, Golgi impregnations, one‐micron plastic sections and electron microscopy. Neurons from all regions of the nucleus can be classified into three categories based on the size and shape of their perikarya, the distribution of Nissl substance and extent of their dendritic arbors. Large neurons (30–50 μ) exhibit numerous Nissl granules and their dendrites often span more than one‐half the width of the nucleus in the transverse plane. Their proximal dendrites measure 4–7 μ in diameter, taper to 0.5–2 μ and display few spines. Medium neurons (20–30 μ) can be distinguished from the large nerve cells by their size and their less extensive dendritic arbor. Proximal dendrites measure 4–7 μ in diameter, tapes to 0.5–2 μ and are realtively aspinous. Small neurons (10–20 μ)display a thin rim of cytoplasm which is either uniformly basophilic or achromatic. The dendrites of these neurons are relatively unbranched and taper from 4–5 μ proximally to 0.5–2 μ distally. Their axons give off one or two collaterals within the nuclear borders. More than one‐half the perikaryal membrane of large and medium neurons is covered by presynaptic profiles which were grouped into three primary categories based upon, differences in their vesicle shape (spherical, pleomorphic, or ellipsoidal). Only a few axosomatic contacts are present on small neurons. Further differentiation of axosomatic synaptic endings is suggested by differences in vesicle size, in pre‐ and postsynaptic membrane densities and in the size of the synaptic terminals. Vesicle size was determined by a cybergraphic tablet and a PDP‐12 computer system and is expressed as a mean area in nm2.
Desending pathways from the brain stem to the spinal cord in some reptiles. I. Origin
Authors: ten Donkelaar H. J. 
Published: January 2005

AbstractIn the present study the origin of the pathways descending from the brain stem to the spinal cord has been investigated in the reptiles Testudo hermanni, Pseudemys scripta elegans, Tupinambis nigropunctatus and Python reticulatus. These reptiles, using highly different types of progression, have been selected, because fundamental variations in the organization of the central motor apparatus are to be expected.The origin of the descending pathways has been demonstrated by recording the occurrence of retrograde cell changes following hemicordotomies and by searching for labeled cells following injection into the spinal cord of the enzyme horseradish peroxidase.In the reptiles studied the presence of interstitiospinal, vestibulospinal and reticulospinal pathways could be demonstrated. A crossed rubrospinal tract has been shown in the turtles and in the lizard, but could not be demonstrated in the Python. The presence of a direct tectospinal pathway could not be shown.
Descending pathways from the brain stem to the spinal cord in some reptiles. II. Course and site of termination
Authors: Ten Donkelaar H. J. 
Published: January 2005

AbstractThe course and termination of the pathways descending from the brain stem to the spinal cord have been studied by tracing the ensuing antero grade fiber degeneration, following appropriate lesions in the reptiles Testudo hermanni, Tupinambis nigropunctatus and Python reticulatus.In these reptiles the presence of interstitiospinal, vestibulospinal and reticulospinal pathways has been demonstrated. A crossed rubrospinal tract has been shown in the turtle and lizard, but could not be demonstrated in the Python. The presence of a tectospinal pathway of any importance could not be shown. However, the tectum mesencephali has been found to project profusely to the brain stem reticular formation.The interstitiospinal tract projects predominantly to the ipsilateral side of the spinal cord. The vestibulospinal projection, arising from the large‐celled nucleus vestibularis ventrolateralis, comprises a large uncrossed and a small decussating component.The rubrospinal pathway terminates in a particular area of the spinal gray, i.e., the intermediate zone, whereas the interstitiospinal, reticulospinal and vestibulospinal tracts all terminate in the medial part of the ventral horn.It appeared that the classification of descending pathways as advocated in mammals by Kuypers ('64) into lateral and medial systems can be readily applied to reptiles. The lateral system terminates in the dorsal and lateral parts of the intermediate zone, the medial system predominantly in the dorsomedial part of the ventral horn. This classification renders it likely that the absence of a lateral focus of termination as well as the absence of a rubrospinal tract in the Python, is correlated to the absence of limbs.A comparison of experimental data concerning the systems descending from the brain stem to the spinal cord in amphibians, reptiles, birds and mammals suggests that these systems with regard to origin, course and termination have a basic pattern in common.
The neurons in the centromedian‐parafascicular complex of the monkey (Macaca mulatta): A Golgi Study
Authors: Hazlett James C. , Dutta Chitta R. , Fox Clement A. 
Published: January 2005

AbstractThe neurons of the nucleus centrum medianum and the neurons of the nucleus parafascicularis were studied in Golgi preparations of the adult monkey(Macaca mulatta)The cell bodies of the principal neurons in the nucleus centrum medianum have a few somatic spines and vary in shape: some are cubical with protruding angles; some are egg‐shaped;some are elongated and sausage‐shaped. Four to six slightly branched dendrites of unequal thickness radiate from the cell body. Some dendrites extend for nearly 500 microns; all have dendritic spines.In the nucleus parafascicularis there are two varieties of principal neurons:(1) neurons with somatic spines and(2) neurons without somatic spines. The neurons with somatic spines are most numerous. They have polygonal‐shaped cell bodies, prominent somatic spines and processes, larger than spines but considerably smaller than dendrites. These processes bear spines and are designated here “microdendrites.” Spines and occasionally a “microdendrite” are found on the axon‐hillocks. Five to six dendrites of unequal thickness emerge from the cell bodies. Some extend for more than 500 microns; all have prominent dendritic spines.The neurons without somatic spines are relatively few. Usually three exceptionally long, slightly branched dendrites, one apical and two basal, emerge from their elongated, slim cell bodies. Some dendrites extend for more than 800 microns; all have a few scattered spines.The Golgi type II neurons found in both of these intralaminar nuclei have small cell bodies and a few, relatively long, undulating dendrites, which bear bulbous dendritic appendages and beaded axon‐like processes. Distally on these dendrites, where the appendages and processes are more numerous, the dendritic appendages and axon‐like processes form complex entanglements. Beaded axons are found on some but not all of the cell bodies. Morphologically these neurons resemble the local interneurons that have been described in various thalamic nuclei.
Polarization of the avian retina. Ocular transplantation studies
Authors: Goldberg Stephen 
Published: January 2005

AbstractThe optic fiber layer of the avian retina, as seen in flat mounts, contains morphological markers of vertical and horizontal polarity. Optic vesicles were rotated in chick embryos prior to the appearance of the optic fiber layer. Later, the optic fiber pattern was examined to determine if its polarity was inverted, or upright or if its right‐left asymmetry changed.Large grafts showed no tendency toward axial realignment, regardless of the stage of operation.Moderate size grafts became realigned mainly by derotation. In this process the vertical axis of the graft showed a greater tendency to derotate than the horizontal axis. Thus, left‐to‐right transplants, when performed prior to embryonic stage 12, developed as left retinas with normally aligned vertical axes, regardless of the degree of operative rotation.Small grafts mainly showed cross‐axial regulation, as opposed to derotation; the polarity of the horizontal axis became fixed prior to the vertical axis.The equatorial zone of the optic vesicle, which lies about midway between the distal tip of the vesicle and the midline of the embryo, was included in moderate size, but not in small grafts. This zone appears critical in the transfer of morphological information to the developing retina.