bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogeny of enteric serotonergic neurons
Authors: Goodrich James T. , Bernd Paulette , Sherman Diane , Gershon Michael D.
Published: January 2005

Serotonergic neurons have previously been identified in the enteric nervous systems of humans, subhuman primates, rodents, and rabbits. The distribution of enteric serotonergic neurons in lower vertebrates was examined in order to determine if these neurons are restricted to mammals and, if they are found more generally amongst vertebrates, when they first appear in vertebrate phylogeny. Since mammalian enteric serotonergic neurons take up 3H‐serotonin by a highly specific mechanism, the radioautographic demonstration of axonal uptake of 3H‐serotonin was used as the primary tool in looking for these neurons. As controls, conditions known to interfere with 3H‐serotonin uptake by mammalian enteric neurons were also examined. These controls included incubation with 10 μ fluoxetine, a specific antagonist, incubation in Na+‐free medium, and incubation in the presence of a 100‐fold excess of nonradioactive serotonin. Radioautographic labeling had to be absent or greatly reduced under all three control conditions for labeling by 3H‐serotonin to be considered specific. Labeled enteric axons were found in cyclostomes (hagfish), teleosts (goldfish), and amphibia (bullfrog) but not in tunicates (sea squirt; sea vase) or echinoderms (sea cucumber). In addition, the serotonin concentration was measured in the intestine of two vertebrates, hagfish and goldfish, that do not have serotonin‐containing enterochromaffin cells. Serotonin was found in both; in hagfish, the amine concentration was highest in preparations of muscularis externa containing the myenteric plexus. It is concluded that enteric serotonergic neurons arose early in vertebrate evolution, possibly in an ancestral chordate resembling amphioxus, although probably not in more primitive prevertebrates, and that they are a general feature of the vertebrate bowel.
The potential binocular field and its tectal representation in rana pipiens
Authors: Grobstein Paul , Comer Christopher , Kostyk Sandra
Published: January 2005

We have studied binocularity in Rana pipiens using optical, behavioral, and electrophysiological assays. The first two assays yielded a consistent picture of the size and shape of the area of uniocular visual field overlap, the potential binocular field. Potential binocular field has an extent of about 90° on the horizontal in front of the frog, narrows to about 60° above the frog's head, and continues to a point well behind the frog. This differs somewhat from a previous report (Fite, '73). Uniocular visual field extent on the horizontal is in excess of 225°, permitting both a large binocular field and panoramic vision. The electrophysiological assay confirms the large uniocular visual field extent. It further shows that physiological binocularity closely reflects uniocular visual field overlap, in the sense that tectal loci representing positions in the potential binocular field, including those behind the frog's head, display convergent inputs from the two eyes.
Subnuclear organization of the ophidian trigeminal motor nucleus. II. Ultrastructural measurements on motoneurons innervating antagonistic muscles
Authors: Moody Sally A. , Meszler Richard M.
Published: January 2005

Horseradish peroxidase (HRP), injected intramuscularly, specifically labeled motoneurons innervating antagonistic jaw muscles in the cottonmouth mocassin, Agkistrodon piscivorus piscivorus. Adductor mandibulae profundus, part 3a, motoneurons were localized in the lateral regions of the ventral and intermediate subnuclei of the trigeminal (V) motor nucleus. These were large cells containing fine, granular reaction product characteristic of α‐motoneurons. Small cells, which contained large coarse reaction granules characteristic of γ‐motoneurons were localized in a separate cluster in the lateral regions of the dorsal subnucleus of the V motor nucleus. Depressor mandibulae motoneurons were localized in the ventromedial regions of the facial (VII) motor nucleus, primarily in the caudal half. Cell sizes ranged from 30–50 μm in diameter and HRP staining characteristics were variable, indicating a mixed population of motoneuron functional types without the segregation noted in the V motor nucleus.

Boutons which made synaptic contact with labeled somata or processes were classified according to morphological type and their frequency of appearance. Boutons containing spherical vesicles (S‐, C‐, T‐) were distributed similarly on motoneurons of both muscles, but more F‐boutons, those with flattened vesicles, synapsed on the adductor motoneurons.

Comparison of snake bouton distribution with that in mammalian spinal cord indicates that synaptology on all these motoneurons are remarkably similar. The more frequent occurrence of C‐boutons, those with a subsynaptic cistern, on reptilian motoneurons may indicate a stronger intrasegmental input, as determined from mammalian degeneration studies.
Effect of protein malnutrition on development of mouse cortical barrels
Authors: Vongdokmai Ratree
Published: January 2005

Undernutrition has been shown to have a profound effect on the central nervous system of maturing experimental animals, not only on gross brain weight and chemical constitution but also on cell structure and function. The present study was undertaken to determine the effect of protein malnutrition on the cortical barrels of mouse. Animals were conceived in and suckled by mothers maintained on an 8% casein diet or on a stock diet. After weaning, mouselings were maintained on their respective diets ad libitum. Four experiments were performed on these mouselings: (1) study of the development of the barrels by the Nissl method; (2) study of the effect of vibrissal damage at different postnatal ages; (3) study of the size of the barrel area and the number of neurons at different postnatal ages; and (4) study of the selectivity of the Golgi‐Cox method.

The findings from comparison of malnourished mice with mice on a normal diet were: (1) a two‐day delay in the development of the barrels; (2) a two‐day lengthening of the period of vulnerability of barrel field neurons to neonatal vibrissal damage; (3) the barrel field area and the relative number of neurons were reduced, with the percentage of reduction decreasing with age; and (4) there was no significant difference in the average percentage of Golgi‐stained neurons at different ages.

These results suggest that poor nutrition has a profound effect on the development and final form of a well‐defined neocortical region. The data presented here provide a useful base line against which various therapeutic regimens to reverse the effects of malnutrition on brain structure may be tested. They also suggest that inducing malnutrition may be an important way in which to manipulate the development of the nervous system in order to study the mechanisms responsible for its final form and function.
Localization of acetylcholinesterase in the main and accessory olfactory bulbs of the mouse by light and electron microscopic histochemistry
Authors: Carson Keith A. , Burd Gail D.
Published: January 2005

Experiments were conducted to examine by light and electron microscopy the localization of acetylcholinesterase (AChE) in the main (MOB) and accessory (AOB) olfactory bulbs of the normal mouse. Evidence from the literature for cholinergic innervation of the mammalian olfactory bulb was then assessed in light of possible correlation between reported sites of termination of centrifugal fibers to the olfactory bulb and the localization of AChE.

AChE‐positive nerve fibers were concentrated in the periglomerular region and internal plexiform layer of the MOB. Stained fibers were also present in the granule cell, mitral cell, and external plexiform layers as well as within glomeruli. A few neurons in all layers of the MOB contained AChE reaction product. Unlike the MOB, AChE‐positive fibers were not present in the glomerular layer of the AOB. AChE‐positive fibers were concentrated in the inner plexiform layer, whereas fewer stained fibers were observed in the external plexiform and mitral cell layer and granule cell layer. Lightly stained neurons were found in the deeper portions of the external plexiform and mitral cell layer and granule cell layer.

Ultrastructurally, AChE reaction product in the MOB and AOB was predominantly associated with small unmyelinated axons. Reaction product was also observed adjacent to axon terminals and dendrites. Occasionally within the MOB, AChE activity was found within periglomerular, tufted, short‐axon, mitral, and granule cells. In the AOB, however, intracellular AChE activity was observed within some mitral/tufted cells and only a few granule cells.

In conclusion, the AChE reaction product was mainly associated with axons in regions of the MOB where centrifugal fibers have been reported. Accessory olfactory bulb AChE localization was different from that of the MOB, suggesting a different pattern of cholinergic input to the AOB. The small amounts and sites of intraneuronal AChE reaction product in cells of the olfactory bulb indicate cholinoceptive rather than cholinergic function.
Histogenesis of the goldfish retina
Authors: Sharma S. C. , Ungar F.
Published: January 2005

The order of production of retinal cells was studied in embryos of the goldfish, Carassius auratus using 3H‐thymidine autoradiography. Cell division ceases first in the neuroepithelium at the fundus of the eye between embryonic stages 19 and 20 and gradually becomes restricted to the retinal margin by stage 24. In the fundus the cell whose nuclei will reside in the inner layer of the retina stop dividing earlier than the cells whose nuclei will reside in the outer retinal layers. Thus the ganglion cells in the fundus of the retina are produced first and the receptors and horizontal cells last.
The infrared trigemino‐tectal pathway in the rattlesnake and in the python
Authors: Newman Eric A. , Gruberg Edward R. , Hartline Peter H.
Published: January 2005

We have studied the infrared trigemino‐tectal pathway of the rattlesnake (Crotalus viridis) and the python (P. reticulatus). In the rattlesnake, horseradish peroxidase (HRP) injections into the nucleus reticularis caloris (RC) result in retrograde filling of cells in the ipsilateral nucleus of the lateral descending trigeminal tract (LTTD) and in the anterograde labelling of terminal fields in the contralateral optic tectum, confirming our previous finding of an RC‐tectal projection. The primary projection of the pit organ of the rattlesnake was traced by injecting cobalt chloride into the pit, demonstrating that the pit organ projects exclusively to the ipsilateral LTTD. Electrophysiological recording from single units in the RC shows that these cells respond to infrared stimulation. Taken together, these results demonstrate that the infrared pathway in the rattlesnake proceeds from the pit organ to the LTTD, to the RC, to the contralateral tectum. In contrast, HRP injection into the tectum of the python results in the retrograde filling of the large cells of the contralateral LTTD. Thus, a direct LTTD‐tectal projection occurs in the python. The cells of the rattlesnake RC and the larger cells of the python LTTD stain heavily for acetylcholinesterse activity and have a similar multipolar appearnce, suggesting that the tectal‐projecting cells in the two species may have a common origin.
Pattern of development of ascending and descending fibers in embryonic spinal cord of chick: II. A correlation with behavioral studies
Authors: Nornes Howard O. , Hart Henry , Carry Michael
Published: January 2005

Studies on the embryonic spinal cord were extended to include the development of the ascending and descending fibers from the brachial level. This study was designed to correlate morphological development of the intersegmental system with physiological and behavioral observations of early embryonic behavior. Chick embryos were analyzed prior to day 6 of incubation, which is before closure of the reflex arc and arrival of supraspinal inputs to the embryonic spinal cord. Injections of 3H‐proline were made in the upper brachial level of chick embryos of stages 27–29 (5–6 days). The location of radioactive label in the marginal zone was analyzed autoradiographically to show the projection of labeled axonal flow from the site of injection. The majority of the labeled axons in the marginal zone was in the first 2–3 segments in both ascending and descending directions from the site of injection. By stage 27 (day 5), ascending labeled axons extended to the upper cervical level and labeled descending axons extended only about 4–5 segments to the upper thoracic level. By stage 29 (day 6) labeled ascending axons extended into the medulla oblongata, and labeled descending axons still extended only 4–5 segments caudally. These studies (Parts I and II) show that at stage 27 (day 5) there was considerable axoplasmic flow of radioactive label in the marginal zone from the lumbar to the brachial plexus but not in the opposite direction from the brachial to the lumbar plexus. Also, axoplasmic flow of label initially extended from the brachial plexus to the medulla oblongata sometime between stages 27–29. It was concluded that the intersegmental system of the embryonic spinal cord is well developed by day 6 of incubation and provides the neuro‐anatomical substrate for early embryonic behavior.
An axonal transport study of the ascending projection of medial lemniscal neurons in the rat
Authors: Feldman Sanford G. , Kruger Lawrence
Published: January 2005

The pattern of projection of the rat medial lemniscus was studied by axonal transport labeling following injections of tritiated leucine, proline and/or adenosine, or of horseradish peroxidase for retrograde identification of the neurons of origin. The vast majority of neurons in the gracile, cuneate, and principal trigeminal nuclei contribute to an almost totally crossed projection primarily to the thalamic ventrobasal complex. Additional thalamic components were traced to specific sites within the “posterior group”, including a medial component largely traversed by lemniscal axons and a caudolateral component lying between the principal nucleus of the medial geniculate and ventral nucleus of the lateral geniculate. We have designated this latter zone “intermediate geniculate”, distinguishing a somatosensory portion of the geniculate group on the basis of its myelo‐and cytoarchitecture, as well as its connections.

Other projections replicated in several animals included the zona incerta and nearby sectors of the substantia nigra; three distinct mesencephalic arrangements within the deep layers of the superior colliculus, the external nucleus of the inferior colliculus, and the intercollicular nucleus; the anterior pretectal nucleus; dorsal sectors of the inferior olivary complex and the ipsilateral cerebellar cortex. The results are compared with findings in other species (with emphasis on the caudal thalamic region) in an attempt to resolve some of the apparent inconsistencies in nomenclature.
Sensory nerve endings in rhesus monkey sinus hairs
Authors: Halata Zdenek , Munger Bryce L.
Published: January 2005

The sensory innervation of primate sinus hairs has been studied by light and electron microscopy. For light microscopy paraffin sections as well as thick frozen sections were impregnated with silver and compared with serial semi‐thin sections of tissue prepared for electron microscopy. One type of sensory terminal is present in the epidermis surrounding the hair follicle, and four specific nerve terminals have been identified within the blood sinus. An epidermal rete ridge collar encircles the hair shaft and contains ∽200 Merkel cellneurite complexes. Numerous other Merkel cell‐neurite complexes are present in the external root sheath of the hair follicle beneath a thick glassy membrane innervated by ∽65 nerve fibers. At this level 10–15 lanceolate or palisade terminals are situated in the connective tissue. Up to 10 simple encapsulated corpuscles can be identified above the level of lanceolate endings and Merkel cell terminals. Ruffini corpuscles are closely applied to the glassy membrane below the lanceolate and Merkel terminals at the level where nerve fibers penetrate the capsule of the sinus. All of these terminals are supplied by 80–100 large diameter myelinated fibers distributed approximately as follows: 65 innervate Merkel cell‐neurite complexes, 15 to lanceolate, 10 to simple corpuscles, and 10 to Ruffini corpuscles. The innervation of the rete ridge collar is independent of that of the sinus consisting of 10–12 fibers derived from the superficial dermal network. Each of these sensory terminals can be correlated with specific functional parameters as described in numerous neurophysiologic studies. Merkel cell‐neurite complexes and Ruffini corpuscles are slowly adapting receptors; lanceolate terminals and simple corpuscles are rapidly adapting receptors.
Medullary and cerebellar projections of the statoacoustic nerve of the dogfish, Scyliorhinus canicula
Authors: Boord Robert L. , Roberts Barry L.
Published: January 2005

The statoacoustic nerve of the dogfish, Scyliorhinus canicula, was transected medial to the ganglion for the purpose of elucidating its central pathways and terminal fields. Following two to six weeks postoperative survival times, transverse, horizontal, and sagittal sections of the brain stem were stained by the Fink‐Heimer silver‐impregnation method to reveal degenerating axons and terminals. Fragmented axons enter the medulla and give rise to medial, descending, and ascending pathway. Fibers of the medial pathway terminate about the soma and lateral dendrites of the large cells that comprise nucleus magnocellularis; descending and ascending flbers terminate on the dendrites of the cells of ventral and superior nuclei respectively. In addition, fibers emanate from fascicles of the descending pathway to form a large field of degenerating axons and terminals within the ventromedial part of the medulla, and a substantial proportion of the fibers of the ascending pathway continues beyond the superior nucleus to terminate among the granule cells of the medial part of the vestibulolateral lobe of the cerebellum. No fragmented axons are traceable to the lateral part (auricles) of the vestibulolateral lobe, cerebellar nucleus or corpus, or those nuclei associated with the lateral‐line lobes. It appears therefore that octavus terminal fields are separate from those of the lateral line at both cerebellar and medullary levels, at least at the level of the first‐order neuron.
Binding of horseradish peroxidase‐α‐bungarotoxin to axonal membranes at the node of ranvier
Authors: Freedman Steven D. , Lentz Thomas L.
Published: January 2005

The binding of horseradish peroxidase (HRP)‐labeled α‐bungarotoxin (α‐BuTx) was investigated in rat sciatic nerve. Activity was found to be localized to the axolemma of myelinated nerve fibers at the nodes of Ranvier. Activity was also seen in other regions of the axolemma where the myelin sheath was separated from the axon by enzymatic treatment. Pretreatment of nerves with native α‐BuTx or curare blocked the binding of HRP‐α‐BuTx to the axonal membranes. This study demonstrates binding of α‐BuTx to axonal membranes although the nature and significance of the toxin receptor is uncertain.
Retinotopic organization of striate and extrastriate visual cortex in the mouse
Authors: Wagor Earl , Mangini Nancy J. , Pearlman Alan L.
Published: January 2005

Detailed retinotopic maps of primary visual cortex (area 17) and the extrastriate visual regions surrounding it (areas 18a and 18b) have been constructed for the C57BL/6J mouse using standard electrophysiological mapping techniques.

Primary visual cortex (area 17), as defined cytoarchitectonically, contains one complete representation of the contralateral visual field, termed V1, in which azimuth and elevation lines are approximately orthogonal. The upper visual field is represented caudally and the nasal field laterally. Binocular cells are encountered in the cortical representation of the nasal 30–40° of the visual field, and there is an expanded representation of the nasal field.

Extrastriate visual cortex of the mouse, like that of other mammals, contains multiple representations of the visual field. The cytoarchitectonic region of cortex lateral and rostral to area 17, termed area 18a, contains at least two such representations. The more medial of these, which by convention we have called V2, is a narrow strip surrounding V1 on its lateral and rostral aspects; the vertical meridian lies along a portion of its common border with V1. The visual field representation in V2 is not a mirror image of that in V1; the representation of the horizontal meridian forms the lateral border of V2, and the visual field representation is split so that adjacent points on either side of the horizontal meridan are represented in nonadjacent parts of V2. The other visual field representation within area 18a, which we have termed V3, is a small but apparently complete representation that lies lateral to V2. The visual field representations medial to area 17 correspond to cytoarchitectonic area 18b. Area 18b contains two representations of the temporal visual field that we have labeled Vm‐r and Vm‐c, and contains little or no representation of the most nasal aspect of the field.
The organization of afferents to the lateral posterior nucleus in the golden hamster after different combinations of neonatal lesions
Authors: Crain Barbara J. , Hall William C.
Published: January 2005

After a neonatal lesion of the ipsilateral superior colliculus, the projections to the lateral posterior nucleus from the contralateral superior colliculus and retina expand their terminal fields until they share a common border. In the first experiment described in this paper, we removed both superior colliculi at birth and used the Fink‐Heimer method to show that the optic tract projection could expand even further and enter the region which would have been occupied by the terminals of the crossed colliculus projection. Similarly, in the second experiment, we showed that the crossed collicular projection could be increased even more if the contralateral eye as well as the ipsilateral colliculus was removed at birth.

Another result of a neonatal superior colliculus lesion is that the projection from the optic tract shares a border with the posterior neocortical projection. In the third experiment, we removed both the ipsilateral superior colliculus and the posterior neocortex at birth and demonstrated that the optic tract projection expanded more than after an ipsilateral colliculus lesion alone.

Our results support the hypotheses that the projections from the ipsilateral and contralateral superior colliculi and the retina compete for synaptic space in the lateral posterior nucleus, and that a similar competition between the retinal and cortical projections may also occur.
Motor axon sprouting and site of synapse formation in intact innervated skeletal muscle of the frog
Authors: Rotshenker Shlomo , Reichert Fanny
Published: January 2005

The pattern of motor innervation to the cutaneous‐pectoris muscle of the frog is altered after injuring the motor nerve to the contralateral muscle in that muscle fibers innervated by a single motor nerve cell become polyneuronally innervated. This polyneuronal pattern of innervation was detected by single cell recordings of multiple end‐plate potentials from muscle fibers. The present study shows that the anatomical basis for this electrophysiological observation is the formation of new additional synapses by intact motor neurons on already innervated muscle fibers at new sites. Light and electron microscopical examination of muscles stained with Zinc Iodide and Osmium revealed that the sources for the new axon terminals were the intact motor axons and nerve endings that gave rise to sprouts that formed synaptic connections with muscle fibers apparently not innervated by their parent axons. Furthermore, new synapses were formed at new synaptic sites. The increased incidence of polyneuronal innervation that was detected electrophysiologically was associated, in the same muscles, with a proportional increase in the average end‐plate size estimated from the measurements of cholinesterase‐stained sites. Additional evidence that synapses were formed at new sites was that the shape of the different components of multiple end‐plate potentials in some polyneuronally innervated muscle fibers differed in their rise‐times. No such recordings were observed in polyneuronally innervated muscle fibers of normal frogs.
Substance P in the vagal sensory ganglia: Localization in cell bodies and pericellular arborizations
Authors: Katz David Miles , Karten Harvey J.
Published: January 2005

The distribution of Substance P‐like immunoreactivity in the jugular and nodose ganglia of rabbits and pigeons has been studied using immunocytochemical staining techniques. Substance P‐like immunoreactivity is localized to neuronal cell bodies and processes in the jugular and nodose ganglia, and to pericellular fiber plexi in the nodose ganglia of both species. The numbers and sizes of cells which exhibited Substance P‐like immunoreactivity in each ganglion were determined using quantitative morphometric techniques.

The distribution of Substance P‐like immunoreactivity in the rabbit and pigeon vagal sensory ganglia is characterized by several general features. In most of the ganglia, immunoreactive neurons factor into discrete types which can be distinguished from one another, and from non‐immunoreactive neurons, by size. In addition, immunoreactive nodose and jugular ganglion cells, respectively, are distinguishable on the basis of size. Finally, a considerably higher percentage of immunoreactive neurons is found in the jugular ganglion than in the nodose ganglion.

Substance P‐like immunoreactivity was also seen in pericellular fiber plexi which encircle individual neurons in the nodose ganglion of rabbits and pigeons. These plexi are composed of varicose fibers which appear to terminate as boutons on the surfaces of the cells which they encircle.

The distribution of Substance P‐like immunoreactivity within the vagal sensory ganglia is discussed with respect to the possible peripheral targets and functions of Substance P‐containing vagal afferents. Our findings suggest that Substance P‐containing vagal sensory neurons are involved in a variety of visceral and somatic afferent functions.
The early development of the nervous system in staged insectivore and primate embryos
Authors: Müller F. , O'Rahilly R.
Published: January 2005

The early development of the nervous system was studied in staged embryos of Hemicentetes semispinosus, Microcebus murinus, Alouatta seniculus, Cebus appella, Cebus albifrons, Macaca mulatta, and Homo sapiens. The specimens were assigned to Carnegie stages 11–13. Serial transverse sections were examined and graphic reconstructions were prepared. The early development of the neural tube is basically similar in all the species investigated but differences in detail are noticeable. The mesencephalic flexure serves in all cases as a landmark for Malpighi's tripartite subdivision of the brain. The nonhuman embryos seem to show a little more variation than the human in the closure of the neuropores in relation to somitic count. With the exception of the later‐appearing terminal‐vomeronasal component, all major portions of the neural crest as classified by O'Rahilly ('65) are represented in both the nonhuman and the human embryos studied. No crest is present at the level of rhombomere 1, nor at rhombomere 3 except in the platyrrhines and some human embryos, nor at rhombomere 5 except in certain human specimens. An indication of the division of the trigeminal ganglion into its primary divisions is rare at stage 11 (C. apella), may be visible at stage 12 (Alouatta, Macaca, Homo), and is definite (in Homo) at stage 13. Ganglionic contributions from head ectoderm (epipharyngeal placodes), as previously described in the human and some other vertebrate embryos, were sought and found in Cebus apella. In both nonhuman and human, a tendency is noted whereby the rostral limit of the occipitospinal crest, high at stage 11, seems to descend relatively at stage 12, and ascend again at stage 13 (at least in the human) to become associated with the appearance of the accessory and hypoglossal nerves. In general, the motor components of the nerves are identifiable before the sensory elements, and, in the present study, nerve fibers were first observed in the human at stage 13 in some of the cranial nerves and in the ventral roots of the spinal nerves.
Propriospinal fibers interconnecting the spinal enlargements in some quadrupedal reptiles
Authors: Kusuma A. , ten Donkelaar H. J.
Published: January 2005

The cells of origin, course and site of termination of long propriospinal fibers interconnecting the intumescences have been studied with the aid of the horseradish peroxidase technique, as well as with anterograde degeneration techniques, in some quadrupedal reptiles (the lizards Tupinambis nigropunctatus and Varanus exanthematicus, and the turtles Testudo hermanni and Pseudemys scripta elegans). The anterograde degeneration findings suggest that long descending propriospinal fibers from the cervical intumescence are distributed bilaterally to the ventral gray of the lumbar enlargement, including the lateral motoneuron column. Long ascending fibers from the lumbar to the cervical intumescence are distributed, also bilaterally, to the ventromedial part of area VII–VIII. The cells of origin of long descending propriospinal fibers were found in the medial part of area VII–VIII in the cervical intumescence, particularly contralateral to the injection side. The cells of origin of long ascending propriospinal fibers were found in the lumbar intumescence, also particularly contralateral to the injection side, in the ventromedial part of area VII–VIII. It seems likely that in the reptiles studied the long propriospinal fibers interconnecting the spinal enlargements are in large part organized as crossed connections.

The demonstration of long propriospinal fibers in lizards and turtles—i.e. quadrupedal reptiles that move their limbs in a particular diagonal pattern—suggests that these pathways are of great importance for the coordination of forelimb and hindlimb movements.
Effects of undernutrition on gliogenesis and glial maturation in rat corpus callosum
Authors: Lai Mabel , Lewis Paul D. , Patel Ambrish J.
Published: January 2005

Rats were undernourished by halving the mother's food intake from the sixth day of pregnancy onwards and through lactation. At weaning, the young rats were restricted to half the normal weight of food. A combination of light and electron microscopic techniques was used to study the effects of this regime on gliogenesis and glial maturation in the corpus callosum of animals aged between 15 and 48 days.

A disturbance of neuroglial proliferation was suggested by the finding of an increased proportion of astroglia relative to oligodendroglia in the 15‐day‐old undernourished rats, indicating a delay in the acquisition of cells produced relatively late in development. Impaired differentiation of oligodendroglia was suggested by the finding in treated animals of increased light oligodendrocytes at 15 days and a deficit of dark oligodendrocytes at 48 days, relative to controls. The previously observed retardation in myelin acquisition seems thus to be related to a dealy in the differentiation of oligodendroglia, although it seems likely that the proliferation of these cells is also disturbed in undernutrition.
Gracilo‐diencephalic relay cells: A quantitative study in the cat using retrograde transport of horseradish peroxidase
Authors: Blomqvist Anders
Published: January 2005

In a quantitative study in the cat, gracilo‐diencephalic relay cells were labeled by the use of retrograde axonal transport of horseradish peroxidase injected into the ventroposterolateral nucleus of the thalamus. An initial series comprising 22 animals with survival periods varying between 2 h and 4 days showed maximal labeling in the gracile nucleus after 24–48 h. The earliest appearing peroxidase‐positive neurons were found after only 6 h, implying a transport rate in the medial lemniscus of at least 100 mm/day. In a second series of five cats, which were killed 24 h after injection, serial sections from the gracile nucleus were embedded in Epon following peroxidase processing, and cut at 2 μm. By stratified random sampling, about 2,000 cells were selected for light microscopic examination.

The total number of nerve cells in a single gracile nucleus was calculated to be about 50,000, out of which about 15,000 were retrogradely labeled. In agreement with previous reports, rostrocaudal differences were observed. Thus, less than a third of the neurons in the rostral part of the nucleus were peroxidase‐positive, whereas about half of those in the middle and caudal regions were retrogradely labeled. The total number of labeled neurons was, however, about the same in the rostral as in the middle‐caudal part of the nucleus. The size of the nerve cell bodies, measured as the cross‐sectional area in the nucleolar plane, differed significantly between labeled and unlabeled neurons. The estimated average diameter of the former was 22 μm and of the latter 17 μm. There was a considerable overlap between the two groups, however, and labeled cells as small as 12 μm in diameter were found. Mainly because of the uneven distribution of labeled neurons, cells in the rostral region were, on the average, significantly smaller than those in the middle and caudal regions; these mean diameters were calculated to be 18, 23, and 21 μm, respectively.

The results of this study support the idea of a heterogeneous organization of the gracile nucleus. However, a much larger proportion of the gracilo‐diencephalic relay cells is situated in the rostral part of the gracile nucleus than has previously been thought. The concept that only medium‐sized neurons project to the diencephalon also seems to need revision. It is concluded that although gracilo‐diencephalic relay cells are, on the average, larger than the nonlabeled neurons, single nerve cells cannot be identified on the basis of size alone. The function of the unlabeled neurons is discussed. Although many of these might relay to various extra‐diencephalic sites, it is suggested that a large number are internuncial neurons.
Representation of the body surface in somatosensory area I of tree shrews, Tupaia glis
Authors: Sur Mriganka , Weller Rosalyn E. , Kaas Jon H.
Published: January 2005

Microelectrode mapping methods were used to determine the organization of the first somatosensory area, S‐I, of tree shrews. Tree shrews were chosen for study because of their generalized body form, phylogenetic relationship to primates, and smooth, easily mapped cortex. A systematic representation of the contralateral body surface was found in an architectonically distinct zone identified as somatic koniocortex. Overall features of somatotopic organization were similar to S‐I of other mammals, S‐I of prosimian primates, and the Area 3b “S‐I proper” representation of monkeys. Like Area 3b in monkeys and the somatic koniocortex in galagos, S‐I in tree shrews is bordered caudally by cortex also responsive to somatosensory stimuli. Several aspects of S‐I organization in tree shrews appear to be primitive and generalized. These include the representation of the trunk with the ventrum at the caudal margin of S‐I, the restriction of the glabrous digits of the hand and foot to the rostral half of the representation and pointed rostralward, the representation of an anterior strip of the forelimb lateral to the hand, and a posterior strip of hindlimb medial to the foot representation. As in a number of other mammals, a large portion of S‐I in tree shrews is devoted to the head. However, the proportion of S‐I activated from the glabrous nose is greater in tree shrews than in any previously studied mammal. We conclude that S‐I of tree shrews has both specialized and generalized features, and that the generalized features importantly relate to an understanding of the evolution of the primate somatosensory system.
Visuo‐oculomotor properties of cells in the superior colliculus of the alert cat
Authors: Peck Carol K. , Schlag‐Rey M. , Schlag J.
Published: January 2005

Visual responses and eye movement (EM) ‐related activities were studied in single units of the superior colliculus (SC) of alert cats. Spontaneous EMs were encouraged by training. Throughout the SC (i.e., in intermediate and deep layers as well as in superficial layers), units were found to respond well to visual stimuli. Strong and consistent responses could be elicited by very dim, low‐contrast stationary stimuli. Visual responses varied from phasic to tonic; some units responded tonically to stationary stimuli in the center of the receptive field, and phasically to peripheral stimuli. Many cells responded more vigorously to moving than to stationary stimuli, but very few responded exclusively to stimulus movement. The vast majority of cells were directionally selective.

A small number of units were sensitive to the absolute, as well as the retinal, position of visual stimuli. These cells were activated by visual stimuli which fell in the receptive field only if the cat's gaze was fixated on one half of the screen. It seems that these cells must receive information about both eye position and the retinal (receptive field) position of the stimulus. It is possible that they reflect coding of target location within a head (or body) frame of reference.

EM‐related units were of two types: (1) about 20% of the sample responded prior to spontaneous or visually‐triggered EMs, and (2) another 10% (or more) responded with, but not before, EMs. Some cells in the second group discharge almost synchronously with EMs and, thus, cannot plausibly be said to respond to the movement of images across the retina. All cells in the first group were directionally selective. The percentage of EM‐related cells in the deep layers of SC is lower in cat than in monkey. Possible reasons for such differences are discussed.
Temporal and spatial patterns of Purkinje cell formation in the mouse cerebellum
Authors: Inouye Minoru , Murakami Ujihiro
Published: January 2005

In an attempt to determine the time of origin and the final localization of Purkinje cells in the cerebellum, pregnant mice were injected with tritiated thymidine successively, four to six times daily, beginning on either day 10, 11, 12, 12.5, 13, or 14 of gestation, considering 6 a. m. on the day when vaginal plugs were found as day 0. Offspring were killed at 30 days of age, and serial sagittal sections of the cerebellum were prepared for autoradiography. Labeled and unlabeled Purkinje cells in the various regions of the cerebellum were counted, and unlabeled ones were considered to be formed earlier than the initiation of the injections. In the medial level of the vermis, the majority of the Purkinje cell population was formed on day 12 of gestation and a few on day 13, whereas the cells in the paravermian and hemispheric portions were formed on days 11 and 12. Thus, a slight lateromedial gradient of the time of Purkinje cell origin was demonstrated. Purkinje cells that were formed after day 12.5 were distributed more in the vermis than in the hemisphere, more in the ventral region of the vermis (lingula, ventral lobule of lobulus centralis, and nodulus) than in the dorsal region (culmen, declive, tuber, pyramis, and uvula), and deep in the vermian fissures, rather than on the surface of the lobules. These findings suggest that postnatally, early maturing regions of the cerebellum may have received many of the later formed Purkinje cells.
Distribution of acetylcholinesterase in the geniculo striate system of Galago senegalensis and Aotus trivirgatus: Evidence for the origin of the reaction product in the lateral geniculate body
Authors: Fitzpatrick David , Diamond Irving T.
Published: January 2005

This inquiry began with the discovery that just tow layers of the lateral geniculate nucleus (GL) of Galago contain large amounts of acetyl‐cholinesterase (AChE). These two layers (layers 3 and 6) are similar in cell size and Nissl‐staining characteristics and project to the same layer in the striate cortex.

To find out whether the pattern of staining is unique in the Galago, We examined the distribution in AChE in the lateral geniculate nucleus of the owl monkey, Aotus trivirgatus. In this species we found that the parvocellular layers (3 and 4) stained darkly for AChE while the magnocellular layers (1 and 2) were only slightly stained. The interlaminar zones as well as the “S” layers were also distinguished by a high level of AChE staining.

In order to determine the source of the cholinesterase staining in layers 3 and 6 of Galago, we studies, in separate experiments, the effects of kainic acid injections into GL, of eye enucleations, and of lesions of the striate cortex. Injections of kainic acid, followed by survival time of 2 and 11 days, produced severe cellular destruction in GL, yet the AChE staining of layers 3 and 6 was undiminished. Eye enucleations had no effect upon the AChE staining of GL even after a survival period of 3 years. In contrast, a small lesion of the striate cortex, followed by a 9‐day survival period, produced conspicuous gaps in the AChE staining of layers 3 and 6. These results indicate that the AChE in layers 3 and 6 is not attributable to the cells within the layers, or to retinal fibers, but is dependent upon descending projections form the striate cortex.

Because of the dependence of AChE reaction product in layers 3 and 6 of GL upon and intact striate cortex, we turned our attention to the distribution of AChE in the striate cortex. In Galago, cholinesterase‐positive cells were found in layer VI of the striate cortex; and in both Galago and Aotus, the striate cortex was distinguished from other cortical areas by a prominent band of cholinesterase activity within layer IV. This band ended abruptly at the 17‐‐18 border. The precise origin of this cholinesterase staining within layer IV of the striate cortex remains to be determined.
Retinofugal pathways in two chondrichthyans, the shark scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J.
Published: January 2005

Retinofugal pathways in the spotted dogfish Scyliorhinus canicula and the thornback ray Raja clavata were studied with reduced silver techniques following unilateral eye enucleations. Optic nerve axons decussate in the chiasma opticum, except for a small ipsilateral projection to the area preoptica. After crossing, retinal projections distribute to the area preoptica, the thalamus dorsalis pars lateralis, the thalamus ventralis pars lateralis, the corpus geniculatum laterale, the nucleus pretectalis, and the superficial layers of the tectum mesencephali. In Scyliorhinus most primary optic fibers terminate in the stratum medullare externum of the mesencephalic tectum, while in Raja the zona externa of the stratum cellulare externum receives the bulk of the retinal input. A basal optic tract could be identified in Raja, but not in Scyliorhinus.

The retinofugal pathways of the two species studied are compared with those of other cartilaginous fishes and other anamniotes. It is concluded that the primary visual system in chondrichthyans resembles that of actinopterygians and amphibians. However, there is a striking difference in the way in which the primary optic fibers reach the tectal target areas. In elasmobranch fish the optic nerve fibers enter the tectum through the zona interna of the stratum cellulare externum and send their axons into the more superficial tectal layers, while in actinopterygians and amphibians the majority of the optic fibers enter the tectum through the superficial layer and distribute their axons to deeper tectal layers.
Efferent tectal pathways in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J.
Published: January 2005

The efferent connections of the tectum mesencephali in the shark Scyliorhinus canicula and the ray Raja clavata have been studied by using the silver impregnation methods of Nauta‐Gygax ('54) and Fink‐Heimer ('67). After a unilateral lesion made through all six tectal layers, three distinct pathways could be observed: (1) an ascending projection both ipsi‐ and contralateral to the pretectal area, the dorsomedial region of the thalamus, and the lateral geniculate body, (2) a commissural projection to the contralateral tectum and intercollicular nucleus, and (3) a descending projection to the rhombencephalic reticular formation. The last mentioned tract can be subdivided into (a) the ipsilateral tractus tectobulbaris ventralis and intermedius, giving off fibers to the intercollicular nucleus, the nucleus reticularis isthmi, and the medial and median reticular formation of the rhombencephalon and (b) the contralateral tractus tectobulbaris dorsalis, which connects the tectum with the contralateral medial reticular formation. Contrary to what has been found in other vertebrates there is no distinct segregation with respect to laterality of tectoreticular connections. Neither an ipsilateral projection to the nucleus isthmi nor a direct tectospinal pathway could be demonstrated with the techniques used.
Polysaccharide and cytoplasmic changes in motoneurons during “chromatolysis” in the opossum spinal cord
Authors: Magalhaẽs‐Castro Heloisa H. , Kruger Lawrence
Published: January 2005

Following axotomy, motoneurons of the opossum spinal cord display an early “axon reaction” or “chromatolysis” characterized by a redistribution of ribosomes accounting for a widespread basophilia and an apparent reduction in the size of two distinct varieties of Nissl bodies. This alteration is accompanied by zones of increased extracellular glycocalyx demonstrable in light and electron microscopy. In addition, large intracellular periodic acid‐Schiff‐positive vacuolated zones in the neuron periphery possess numerous free ribosomes, glycogen, lipids, and huge vacuolated sacs containing a flocculent matrix material similar to that found within the sacs of granular endoplasmic reticulum. “Artifacts” in the neuronal periphery associated with chromatolysis seen in light microscopy are probably related to polysaccharide alterations and redistribution of granular endoplasmic reticulum.