bluuebunny/crossref_metadata_2025 huggingface dataset:
The development of hippocampal and dorsolateral pallial region of the cerebral hemisphere in fetal rabbits. V. Sixty millimeter stage, glial cell morphology
Authors: Stensaas L. J.
Published: January 2005

The structure of the cerebral hemisphere of the 60 mm rabbit embryo was studied with aniline and Golgi stains. Two types of neuroglial cells are present for the first time at this stage and are described in detail: (1) Young neuroglial cells are elongate cells whose smooth somata are connected to an arbor of fine porcesses by a peduncle of varying length. They appear to develop from freely arborizing spongioblasts as somata lose their attachment to the ventricular surface and migrate toward the cortical plate. This suggests that astrocytes will be formed at a later state from freely arborizing spongioblasts rather than from typical spongioblasts whose connection to the pia has atrophied. (2) Small glial cells are present at all levels above the matrix lamina. They have small, smooth somata and fine, mossy processes arising from a short trunk at one pole of the cell. Although their origin is unknown, their small soze suggests they arise directly from germinal cells rather than from freely arborizing spongioblasts. Lacking conclusive evidence of their identity, they are tentatively regarded as a primitive type of oligodendrocyte.
Coding in tuberous and ampullary organs of a gymnotid electric fish
Authors: Suga Nonuo
Published: January 2005

The coding mechanisms of the tuberous and ampullary organs of Gymnotus carapo were studied. The tuberous fibers had no or irregular spontaneous discharges and showed phasic on and/or off responses to 50 msec electric pulses, while the ampullary fibers had regular spontaneous discharges and showed tonic responses to the pulses. The threshold measured with the electric pulses was 1.5 mV/cm on the average for the tuberous fibers and 0.26 mV/cm for the ampullary fibers. For the tuberous fibers, a 0.5–1.0 msec electric pulse was sufficiently long to evoke the maximum response when the intensity of the pulse was 3–10 times higher than the threshold of a given fiber. However, responses of the ampullary fibers were more dependent on duration.

To repetitive stimuli of 0.5 msec electric pulses, the tuberous fibers discharged several impulses per stimulus; while the ampullary fibers responded by changingpontaneous discharges from an unlocked to a locked state only in a certain range of intensity and repetition rate of stimulus pulses. The number of impulses per stimulus in the locked state was not modified by change in stimulus intensity. More than half the tuberous fibers and all amullary fibers were mechanically excitable. However, these organs are not considered to act as mechanoreceptors in natural conditions, but to act as electroreceptors.
The fine structure of the caudate nucleus of the cat
Authors: Adinolfi Anthony M. , Pappas George D.
Published: January 2005

The fine structure of the caudate nucleus was studied by electron microscopy. Examination of various regions revealed (1) the majority of neurons are small (10–15 μ ) and can be distinguished from larger neurons by the absence of Nissl bodies, (2) synapses occur most often on dendritic spines, and (3) myelinated fibers in the neuropil have a mean diameter of about 630 mμ and occur singly or in small bundles. These observations suggest a functional organization involving predominantly axodendritic synapses. In addition, small diameter, slow‐conducting efferent fibers might explain, in part, the long latency of responses in thalamic, lenticular and entopeduncular elements following caudate stimulation. This is discussed in conjunction with recent physiological findings.
The septum in the human brain
Authors: Andy Orlando J. , Stephan Heinz
Published: January 2005

The septum of the human brain was studied in relation to its location, composition and development. It was possible to divide it into two parts: septum pellucidum, composed of fiber tracts and glia, and septum verum (true septum) which in addition to fiber tracts and glia, contain neurons arranged in a nuclear pattern. The septum verum in the human corresponds to the septum as described in lower forms. The human septum has been thought to have regressed and be nearly functionless in contrast to lower forms. However, the nucleus septalis triangularis is the only septal nucleus which regressed in development when compared to that in the brains of insectivores and primates. The rest of the septal nuclei progressively increased in size during primate development. Finally, it should be emphasized that the septum verum of the human has attained its highest degree of development in primate phylogeny.
The main sensory trigeminal nucleus in the pigeon: A single‐unit analysis
Authors: Zeigler H. Philip , Witkovsky Paul
Published: January 2005

A single‐unit analysis of the main sensory trigeminal nucleus of the pigeon was carried out. A total of 130 units from 20 birds were isolated and their modality, adaptive properties and receptive field characteristics were defined.

Seventy‐two percent of the cells were activated by mechanical stimulation ranging from very light touch to pressure. Receptive field areas were generally less than five mm2 in extent. Six units had receptive fields in the region of the orbit, but the receptive fields of most units were confined to the ipsilateral dorsal or ventral beak. Both inner and outer beak surfaces were represented, but no units responsive to tongue stimulation were encountered. Somatotopic organization was evident only in the dorso‐ventral plane where there was a clear sequence of representation from mandibular to maxillary to opthalmic areas. Of the units responsive to mechanical stimulation, 60% were slowly‐adapting, 40% were fast‐adapting.

A number of cells (28%) were driven by opening or closing the mouth. Most of these signalled the displacement by a change in their steady discharge rate; a few cells responded to beak displacement with a transient burst.

These results clarify the nature of the feeding deficits produced by lesions of the main sensory trigeminal nucleus and suggest an involvement of the nucleus in the sensory control of mandibulation during feeding in the pigeon.
Light and electron microscopical obervations of the ventral horn and ventral root in long term cultures of the spinal cord of the fetal mouse
Authors: Guillery R. W. , Sobkowicz Hanna M. , Scott G. L.
Published: January 2005

Segments of spinal cord from 14 to 16 day old fetal mice, grown in vitro for three weeks or longer, show some of the cytoarchitectonic subdivisions of adults cord and several characterstic fiber bundles. In the ventral horns the largest cells have thick axons which leave the explants in well defined ventral roots. These axons run a long course through the outgrowth zone and branch repeatedly there. They have no branches that ramify in the explants nor do they return to the explants. Smaller cells in the ventral horns from a distinct class of cells. Their axons ramify entirely within the explants, mainly within the homo‐ or contralateral ventral horn. Axons of dorsal horn cells also ramify within the ventral horns. Some of their branches pass into a fiber band that surrounds the explant while others enter the outgrowth zone. These last generally return to the explant and form terminal ramifications there.

The development of fiber bundles and the appearance of cell groups can be followed in unstained explants, and it appears that each of the characteristic axon patterns develops in vitro.

Dendrites of ventral horn cells enter the outgrowth zone and in the ventral roots they are closely related to many passing axons. At some distance from the original explant these processes from a tissue that resembles the central nervous system. New synaptic junctions are formed and the neuronal elements lie embedded amongst glial cells and their processes. The glial cells also from a more or less continuous epithelium separating the feeding solution from the neuronal elements.
Limb immobilization and the diameters and number of nerve fibers
Authors: Tomanek Robert J.
Published: January 2005

The right hind limbs of young and adult male albino rats (aged 35 and 101 days) were immobilized with plaster of paris casts for a period of 11 weeks. The medial gastrocnemius nerve was then excised, and fixed under slight temsion in 0.5% osmium tetroxide. Transverse sections of the nerve were projected onto drawing paper and the diameters of all myelinated fibers were measured.

While the results demonstrated a disuse atrophy of the gastrocnemius muscle, the mean nerve fiber diameters of the immoblized groups did not differ from those of the controls. However, immoblization in adult animals was associated with a reduction in the frequency of fibers < 7 μ. On the basis of these data, it is suggested that muscle atrophy may proceed without concomitant alterations in nerve fiber diameter.

The number of myelinated fibers in nerves from animals immobilized during postnatal growth is significantly liwer than those of the controls. This finding indicates that limb immobilization retards myelination.
The origins, course and distribution of the dorsal and intermediate acoustic striae in the rhesus monkey
Authors: Strominger Norman L.
Published: January 2005

Attempts were made to produce discrete stereotactic lesions in the dorsal cochlear nucleus (Dc) in a series of rhesus monkeys. Anterograde degeneration was studied using Nauta and Fink‐Heimer techniques. Following lesions confined to the caudal pole of Dc, a few degenerated fibers projected to the contralateral lateral superior olivary nucleus via the dorsal acoustic stria. Degeneration was distributed to the contralateral ventral and to a lesser extent dorsal nuclei of the lateral lemniscus. The contralateral central nucleus of the inferior colliculus was a major site of termination of second order auditory fibers; a small number of degenerated fibers ascended to this nucleus ipsilaterally, and a few crossed in its commissure. A few degenerated fibers also were present in the contralateral magnocellular division of the medial geniculate body.

When Dc was damaged at levels which overlie the posteroventral cochlear nucleus (Pv), or after lesions involving both subdivisions, degeneration was seen in the intermediate as well as in the dorsal acoustic stria. Fibers arising in Pv coursed through Dc and were interrupted by lesions in the latter. In addition to degeneration described above, fibers projected to the ipsilateral lateral superior olivary nucleus, contralateral medial trapezoid nucleus, and bilaterally to dorsal retroolivary and to preolivary cell groups. No degeneration was seen in the trapezoid body. Lesions involving the posteroventral and anteroventral (Av) cochlear nuclei produced degeneration in the intermediate acoustic stria and in the trapezoid body, but not in the dorsal stria. Degeneration in the intermediate acoustic stria was similar to that present after lesions affecting Dc and Pv. Thus, since Av does not project crossed fibers to this structure, these findings indicate that Pv sends some fibers to the contralateral as well as ipsilateral lateral superior olivary nucleus.
Organization of neurons in the visual cortex, area 17, of the monkey (Macaca mulatta)
Authors: Lund Jennifer S.
Published: January 2005

A study of neuron morphology in Golgi Rapid and Kopsch preparations of area 17 of the monkey has shown three basic cell groups— pyramidal neurons, stellate neurons with spinous dendrites and stellate neurons with spine‐free or sparsely spined dendrites. These three neuron groups show different distributions in depth from pia to white matter and differ in their relationship to zones of concentrated termination of geniculo‐cortical axons. The neuron type most closely related to the laminae receiving a heavy geniculo‐cortical projection is the spinous stellate cell. This cell type is restricted to lamina IV. Included in this zone is the broadest band of geniculo‐cortical axon projection (lamina IVC), the horizontal fiber band (lamina IVB) comprising the major portion of the stria of Gennari (receiving little or no thalamic projection) and the narrow band of thalamo‐cortical fiber termination which occurs superficial to the stria of Gennari (lamina IVA). Pyramidal neuron cell bodies are almost totally excluded from lamina IVC and the apical dendrites of lower pyramidal neurons bear many fewer spines in lamina IVC than in laminae V and VI. The basal dendrites of upper pyramidal cells spread superficial and deep to lamina IVA rather than within it. Spine‐free stellate neurons occur at all cortical levels and sparselyspined varieties have not been impregnated in lamina IV, but occur in the other laminae.

Three groups of presumed thalamo‐cortical axons have been identified, two of which resemble each other in morphology (having long collaterals which appear to terminate by means of spine‐like projections of the axonal surface) but not in distribution. One group of these axons bearing spine‐like projections distributes in laminae IVC (principally in the deeper half, IVCβ) and IVA; the other is restricted in distribution to the upper half of lamina IVC (IVCα). The third group of thalamo‐cortical axons distributes to lamina I and appears to lack the spine‐like projections shown by the other two axon groups.
Transneuronal changes in the gracile nucleus
Authors: Loewy Arthur D.
Published: January 2005

The gracile nucleus was studied in the monkey and man with light microscopic methods after lesions to the posterior columns. The medullas from six autopsy cases were studied; four of these were from patients who had survived spinal cord transections for periods of 2, 22, 41 days, and 22 years. The deafferented gracile neurons did not show changes in Nissl substance, in neurofibrillar patterns, or in nuclear structure that could be directly related to posterior column denervation. Neuron counts of the gracile nucleus were made in one case of a T9 spinal transection of 22 years standing and yielded figures not significantly different from those established by systematic counts in other human autopsy material in which CNS lesions were not present.

In the monkey, the neuronal population of the gracile nucleus did not change as a result of posterior column transection. In cases of six months standing, the denervated neurons showed a 25% decrease in mean cell body area and about a 20% decrease in mean nuclear area. About 1% of the neurons on the operated side appeared darker in reduced silver preparations than any of the gracile neurons from the unoperated side.
The connections between bipolar cells and photoreceptors in the retina of the domestic cat
Authors: Boycott B. B. , Kolb H.
Published: January 2005

An invaginating bipolar cell that has dendritic terminals forming the central elements of the cone triads is described for the retina of the cat. This type of bipolar contacts a minimum of four or five and a maximum of nine or ten cones. There is no evidence for a bipolar cell which contacts only one cone, i.e., a midget bipolar cell as in simians. There are flat bipolar cells that make superficial contacts with the bases of the cone pedicles and are postsynaptic to between 8 and 14 cones. One cone can be in contact with both an invaginating and a flat bipolar cell. There is evidence suggestive of two kinds of flat bipolars. A comparison is made between the bipolar connections in simians and the cat. The comparison is summarized in figures 29 and 30.
Growth, differentiation and ribonucleic acid content of the fetal rat spinal ganglion cells in culture
Authors: Sobkowicz Hanna M. , Hartmann Henrik A. , Monzain Rachel , Desnoyers Patricia
Published: January 2005

Observations were made on 324 cultures of spinal ganglia which were excised from fetal rats between the tenth and eighteenth day of gestation. The cultures were maintained up to 81 days in vitro. As a control sixteen Sprague‐Dawley rats from two litters were sacrificed at different ages. RNA content of the cell bodies in both normal and cultured spinal ganglia was determined by the Edström method. The volume of the cell bodies was determined by the optical reconstruction method of Micklewright. Spinal ganglion cells in culture develop at a much slower pace than in situ, but show the normal sequential order of cytodifferentiation. A few days after explantation, the cells increase rapidly in size and a large fibrillogenous zone becomes apparent around the centrosome. All of the neurofibrillar network of the cell and the axon seem to derive from this zone. At this stage the Nissl material is found mainly at the periphery of the cell body since the fibrillogenous zone is essentially free from Nissl granules. The initial development of the zone in culture is accompanied by no or a very small increase in the cellular RNA content present at the time of explantation though the cell volume increases greatly. In later stages, the fibrillogenous zone disappears slowly as a separate entity while the Nissl bodies invade the entire soma of the cell. When this is accomplished the neurofibrillar network becomes complex, the Nissl bodies form distinct patterns, the growing fibers start to myelinate. The cells increase only slowly in size. After four to ten weeks in culture the typical spinal ganglion cell is a monopolar neuron which is morphologically advanced to various degrees. However, some less common morphological forms can be seen occasionally in culture as is also the case in normal material.

Our cytochemical determinations suggest that a growth‐curve relationship exists in normal material between the RNA content of the cell and the age of the animal up to about eighth to eleventh day after birth. The largest increase in RNA content in normal material occurs in the second week after birth when nearly adult values are reached. In culture, a similar relationship exists between the age of the culture and the RNA content of the cells though the data points are scattered considerably. In sharp contrast to the normal material, however, the slope of the growth‐curve is very much less steep and no plateau is apparent up to 81 days in vitro. Since the initial increase in cell volume in culture is due to a formation of the fibrillogenous zone and is not accompanied by a proportional increase in RNA it seems likely that the increase in RNA content of the cell during normal development is primarily due to the formation and differentiation of Nissl material.
Electron microscopy of non‐neuronal cellular changes accompanying neural degeneration in thalamic nuclei of the rabbit. I. Reactive hematogenous and perivascular elements within the basal lamina
Authors: Matthews Murray A. , Kruger Lawrence
Published: January 2005

Electron microscopic examination of several thalamic nuclei undergoing neural degeneration following ablation of their cortical projection fields revealed reactive changes in vessels unrelated to direct mechanical trauma. A series of 30 rabbits were studied at post‐operative survivals of one to 238 days. Many neurons display signs of retrograde atrophy within the first week accompanied by a distinct increase in the number of perivascular cells within the basal lamina surrounding venules and large capillaries. This reaction was optimally observed between 5 and 98 days post‐operatively and was limited to the circumscribed zones of degeneration. In early stages, some vessels displayed margination of hematogenous elements, predominantly agranular leukocytes, of which some examples were seen in phases suggestive of diapedesis. Cells within the perivascular space exhibited diverse morphology. In addition to the indigenous “pericyte” population, there were numerous agranular leukocytes, and a few plasma cells and eosinophils. Within the second to third week postoperatively, some perivascular elements become enlarged and display electron‐lucent lipid vacuoles and PTA‐positive dense bodies of complex morphology, many of which are clearly lysosomal in nature. This cellular reaction persists for three to four months, after which time the cytoplasm displays evidence of cholesterol crystals and lysosomal transformations suggestive of terminal or residual bodies. Morphological criteria for identifying the possible origin of vacuolated, lysosomeladen perivascular cells are presented for a consideration of their possible derivation from pericytes and/or hematogenous elements. Of the several hypotheses considered to account for these findings, it appears likely that lipid and protein end‐products of neural degeneration provide the stimulus for perivascular aggregation and subsequent transformation.
Cytoarchitectural subdivisions of the periaqueductal gray matter in the cat
Authors: Hamilton Betty L.
Published: January 2005

The neuronal population of the PAG consists of relatively small cells, ranging from approximately 8 μ to 30 μ in diameter. These neurons are of three different types and are classified as I, II, and III for the sake of convenience. Each class aggregates in certain areas of the central gray to form subdivisions distinguishable by differing neuronal distributions as well as by cellular characteristics. Class I neurons are small, spindle shaped cells that stain darkly with cresyl violet. They aggregate loosely around the cerebral aqueduct, thus forming the comparatively acellular inner ring of the PAG, the nucleus medialis. The class II cells are also small and darkly staining, but they are fusiform to spherical in shape. These cells cluster more closely and are surrounded by many glial cells. They congregate in the area dorsal to the cerebral aqueduct to form the nucleus dorsalis. The largest cells of the PAG, the class III neurons are spherical or tringular in shape and stain lightly due to their sparse Nissl substance. Frequently glial cells abut the perikaryon of these neurons. They aggregate very closely to form the dense cellular outer portion of the PAG. This mantle of cells is called the nucleus lateralis.
Architectonic studies of the diencephalon of Iguana iguana (Linnaeus)
Authors: Butler Ann B. , Northcutt R. Glenn
Published: January 2005

The normal anatomy of the nuclei and major fiber tracts of the diencephalon and pretectum of the lizard, Iguana iguana, are described and compared to descriptions of the diencephalon of other reptiles. Clarification of variations in the nomenclature has been attempted, based on comparison of normal and experimental material. Experimental studies of afferent and efferent projections of the diencephalon of various reptiles are reviewed and discussed. The earlier literature on thalamic homologies between reptiles and other vertebrates is re‐examined, and a new interpretation offered based on these new results.
A comparative study of spinocerebellar systems in three classes of poikilothermic vertebrates
Authors: Hayle T. H.
Published: January 2005

Spinocerebellar systems have been investigated in three classes of poikilothermic vertebrates. Lesions were made in the spinal cord of a number of dogfish, rudd and frogs which were selected as representatives of their classes. After a postoperative survival period the resulting fibre degeneration was demonstrated by means of a suitable silver impregnation technique. The findings have provided experimental confirmation of a spinocerebellar pathway in each species examined. In the dogfish these fibres form part of a mixed spinal lemniscus, which ascends through the brainstem, and leave it to enter the corpus cerebelli, through its peduncles. In the rudd two separate systems were found, one of which corresponds to that seen in the dogfish. The other forms a separate compact fasciculus which lies more dorsally in the brainstem throughout its course. This one can be followed into the cerebellum through the peduncle. Within the corpus cerebelli it was not possible to distinguish between the two systems. In the frog also two separate systems were seen. These retained their individual identity from the spinal cord to their entrance into the cerebellar peduncle beyond which they appeared to merge. These findings have been compared with the results of other authors, and an attempt has been made to show how and why such systems have evolved.
Impulses in dorsal spinal nerve rootlets in cats and rabbits arising from dorsal root ganglia isolated from the periphery
Authors: Kirk E. J.
Published: January 2005

Spontaneous discharges arising within lumbar dorsal root ganglia that had been isolated from the periphery by section of the corresponding spinal nerves were recorded in dorsal spinal nerve rootlets in cats and rabbits. Those dorsal rootlet fibers that were individually isolated had conduction velocities of less than 22 meters/second, i.e., they were Aδ fibers. The chronic preparations had been kept alive for between 1 and 21 days, and spontaneous activity was present in each of them. In acute preparations in which hemorrhage was minimal, spontaneous activity first appeared three to three and one‐half hours after section of the spinal nerve. Spontaneous activity in the dorsal rootlets continued for approximately 25 minutes after physical separation, by dissection, of the active nervous tissue from the remainder of the preparation. The activity was not recorded in either the distal parts of sectioned ventral rootlets or the portion of a sectioned spinal nerve that remained in continuity with its dorsal root ganglion.

It is suggested that the occurrence of these discharges could partly explain the observed differences in the extent and reactivity of cutaneous sensory areas between animals in which dorsal spinal nerve rootlets were sectioned close to the spinal cord and animals in which the corresponding spinal nerves were sectioned distal to their dorsal root ganglia.
The neuronal architecture of the cochlear nucleus of the cat
Authors: Brawer James R. , Morest D. Kent , Kane Eileen Cohen
Published: January 2005

A detailed parcellation of the entire cochlear nucleus of the cat was prepared with the Nissl and Protargol methods in the form of a cytoarchitectonic atlas. Neuronal cell types were characterized in rapid Golgi impregnations. Golgi impregnations were used to define the specific features of the mature neuronal types. Neurons from the Golgi preparations were systematically mapped according to type and location in serial sections. These neurons were then plotted in corresponding positions in the cytoarchitectonic atlas. This combined Golgi‐Nissl approach provides a scheme in which neuronal types, defined in terms of a number of functionally significant features, can be precisely localized within the cochlear nucleus.
The naso‐temporal division of the cat's retina re‐examined in terms of Y‐, X‐ and W‐cells
Authors: Stone Jonathan , Fukuda Yutaka
Published: January 2005

In the cat, as in all mammals, optic nerve fibres decussate only partially, so that some of the ganglion cells in one retina project to the contralateral side of the brain, and some to the ipsilateral side. The retinal distribution of ipsi‐ and contralaterally projecting ganglion cells, described in a previous study, has been re‐examined in the context of the recent classification of cat retinal ganglion cells into three major types (W‐, X‐ and Y‐cells). Evidence is presented of significant differences between the three cell types in the retinal distribution of ipsi‐ and contralaterally projecting cells. The pattern of naso‐temporal division of retina described previously thus appears to be a composite of the different patterns of the three cell types. Functional implications of these different patterns are considered.
Projections from the striate cortex to the diencephalon in the squirrel monkey (Saimiri sciureus). A light microscopic radioautographic study following intracortical injection of H3 leucine
Authors: Holländer Horstmar
Published: January 2005

Tritiated leucine was injected into three different regions of the striate cortex in nine squirrel monkeys and the axoplasmic transport of labelled protein in the neurons was used to identify terminal fields of projection in the thalamus. The regions of injection corresponded to those representing about 3°, 10°, and 30° eccentricity in the contralateral visual field. The periods of post‐injection survival were 9–19 hours, 8 days, and 23 days. The exposure was about three weeks in all cases. In the thalamus terminal fields of projection were identified in the lateral geniculate nucleus, the posterior nucleus of the thalamus, the inferior and lateral pulvinar nucleus, the reticular nucleus of the thalamus and the pregeniculate nucleus. In most of the projections the location of the terminal fields varied systematically with the location of the injection site indicating a retinotopic organization. In eight of the nine experiments all of the thalamic projections were observed. In the cases with postinjection survival times of 8 and 23 days pronounced axonal labelling was seen, and the corticothalamic pathway could be traced from the site of injection to the thalamus. In one experiment in which only the superficial layers of the cortex were labelled by the injection no thalamic projection was found.
Photoreceptor degeneration and synaptogenesis in retinal‐degenerative (rd) mice
Authors: Blanks Janet C. , Adinolfi Anthony M. , Lolley Richard N.
Published: January 2005

The influence of photoreceptor degeneration upon synaptogenesis in the photoreceptor terminal of developing retinae of rd mice (C3H/HeJ and C57BL rd le) is outlined and compared to the sequential development of the photoreceptor terminals of the retinae of normal mice. The initial phases of synaptogenesis in the photoreceptor terminal of the rd retina appear normal during the first postnatal week. Appositional contacts form between the photoreceptor terminal and neuronal processes before invagination of horizontal processes occurs to form a dyad configuration. A virtual absence of triad configurations in the photoreceptor terminal suggests that synaptogenesis is arrested in the photoreceptor terminal of the rd retina between the 7th and 10th day, at which time the central (bipolar) process normally invaginates into the photoreceptor terminal. During this period, photoreceptor cell death proceeds rapidly but few signs of degeneration are apparent. It is suggested that the inherited abnormality influences the maturation of bipolar cells more than that of horizontal cells. The b‐wave component of the electroretinogram (ERG) of the immature rd retina is discussed in terms of photoreceptor/bipolar cell synaptic contacts.
Quantitative studies on motoneurons. II. Spatial and dimensional organization of hypoglossal motoneurons in the boa constrictor, Constrictor constrictor
Authors: Ulinski Philip S.
Published: January 2005

The spatial distribution and sizes of degenerating hypoglossal neurons were studied following the removal of the genioglossus or hyoglossus muscles or of unilateral glossectomy in common boas with survival times of 7, 14, 21 or 40 days. The spatial organization of this nucleus differs from that of most cranial nerve nuclei in lacking a subnuclear organization: genioglossus and hyoglossus motoneurons are spread evenly throughout the nucleus and intrinsic tongue neurons show only a slight tendency to accumulate in the caudal half of the nucleus. The genioglossus and tongue neurons probably serve both ipsilateral and contralateral muscles with the ipsilateral innervation being largest; the hyoglossus motoneurons probably innervate only ipsilateral muscles. Complementary analyses of the transverse sectional areas of both degenerating and non‐degenerating neurons indicates that, although their size ranges overlap, genioglossus motoneurons are small and tongue and hyoglossus motoneurons are progressively larger.
Topographic atlas of catecholamine and acetylcholinesterase‐containing neurons in the rat brain. II. Hindbrain (mesencephalon, rhombencephalon)
Authors: Palkovits Miklos , Jacobowitz David M.
Published: January 2005

A complete stereotaxic neuroanatomical atlas of the rat hindbrain was prepared using transverse serial sections stained with Luxol fast blue and cresyl violet. Catecholamine‐containing cell bodies and fiber terminals were identified by the histofluorescence method. The acetylcholinesterase distribution was histochemically localized. A detailed stereotaxic atlas of the catecholaminergic and acetylcholinesterase‐containing structures is presented.
Formation and regression of inappropriate nerve sprouts ing trochlear nerve regeneration in Xenopus laevis
Authors: Fangboner Raymond F. , Vanable Joseph W.
Published: January 2005

After sectioning N IV in Xenopus laevis larvae, in addition to the regeneration of that never to the superior oblique muscle (SOM), sprouts form from N III, chiefly from the branch supplying the inferior oblique muscle (IOM). these were shown to innervate the SOM by methylene blue staining, silver and zinc iodide‐osmium impregnations, and electrical stimulation of N III. The competition thus established is resolved in favor of N IV, in a way suggesting a displacement of the inappropriate sprouts by the returning N IV fibers. This hypothesis received support by two anatomical findings: a delay in the decline of N III sprouts on the SOM when the return of N IV is delayed and a significant inverse relationship between the number of N III sprouts and regenerated N IV fibers on the SOM 39 days after N IV sectioning. Degenerating N III sprouts were detected while their number was declining. The physiological studies showed a significant reduction in the function of N III sprouts tested 30–34 days after N IV sectioning as compared with larvae tested 11–15 days after sectioning, which correlated with the anatomical observations We conclude that there is a withdrawal of inappropriate nerve fibers during the resolution of competition between the regenerating N IV fibers and these sprouts from N III.
Histochemistry of cholinesterase in amphioxus (Branchiostoma lanceolatum, pallas)
Authors: Flood Per R.
Published: January 2005

Biochemical and histochemical experiments showed that the cholinesterase activity in amphioxus is due to specific acetylcholinesterase. Light and electron microscopic histochemical staining methods demonstrated that the acetylcholinesterase activity is localized to the junctions between processes of the trunk muscle fibres and the lateral surface of the spinal cord (the central motor end plate) to the junction between processes of the muscular notochordal lamellae and the ventral surface of the spinal cord (the neuro‐chordal junction) and to the junctions between the peterygal axon plexus and processes of the pterygealmuscle fibres. In the central motor end plate the dorsal and the ventral compartments, innervating superficial “red” and deep “white” trunk muscle fibres respectively, were equally intensely stained. Lower activities were seen in the spinal cord, trunk muscle. pterygeal muscle and notochord. It is concluded that most of the specific acetylcholinesterase found in amphioxus tissues is related to various kinds of neuro‐muscular junction and accordingly that these probably are cholinergic.
Anatomical analysis of pupillary reflex pathways in the rhesus monkey
Authors: Pierson Roberta J. , Carpenter Malcolm B.
Published: January 2005

The pupillary light reflex was analyzed by producing lesions in afferent and efferent pathways in a series of monkeys. Unilateral enucleation and autoradiographic technics utilizing axoplasmic flow were used to determine afferent pathways. Lesions also were made in the pregeniculate nucleus (PGN) and individual components of the oculomotor visceral nuclei. Degeneration was studied in Wiitanen and Nissl stained sections. Infrared pupillographic records were made before and after surgery. Enucleation and autoradiographic studies revealed: (1) bilateral retinal projections to the pretectal olivary nuclei (PON) and PGN, and (2) predominautly contralateral projections to parts of the optic tract and sublentiform nuclei. PGN appeared to project to the ipsilateral PON. Unilateral lesions in the anterior median nucleus (AM) with direct, or indirect, involvement of the medial visceral cell column (MVCC) produced: (1) “static” and “dynamic contraction” anisocoria and (2) ipsilateral reductions in direct and consensual pupillary responses. Lesions in the rostral MVCC with no involvement of AM produced only static anisocoria. Degeneration from these lesions was found rostrally in the ipsilateral oculomotor roots, but no retrograde cell changes were detected in the pretectal region. Lesions in the caudal MVCC, the lateral visceral cell column (LVCC) and PGN produced no anisocoria or reductions in the pupillary light reflex. Both anterograde and retrograde degeneration in the contralateral PON were observed with lesions in LVCC, but no degeneration was seen in the oculomotor root fibers.
Monoamine distribution in primate brain. I. Catecholamine‐containing perikarya in the brain stem of Macaca speciosa
Authors: Garver David L. , Sladek John R.
Published: January 2005

The distribution of catecholamine‐containing cell bodies was examined in the brain of Macaca speciosa using the Falck‐Hillarp histofluorescence technique. Extensive accumulations of such cells were seen in the ventral tegmental area, locus coeruleus, mesencephalic reticular formation and ventrolateral reticular formation of pons and medulla. This distribution was compared to that previously reported in rat, cat, squirrel monkey and human brain. Apparent species dissimilarities and similarities are reported.
Fine structure and distribution of axon terminals from cochlear nucleus on neurons in the medial superior olivary nucleus of the cat
Authors: Lindsey Bruce G.
Published: January 2005

The morphology and distribution of axon terminals on central column and marginal neurons of the cat medial superior olivary nucleus (MSO) were analyzed by electron microscopy. Individual neurons or groups of cells oriented such that substantial lengths of their dendrites were within a 5–7 μthick section were selected for detailed study. Thin sections were cut from remounted thick sections. Boutons with spherical vesicles arise directly from myelinated axons; more than one synaptic region of an axon, each separated by a myelinated segment, may contact a given dendrite. Boutons with flattened and occasionally dense core vesicles arise from both myelinated and unmyelinated portions of axons; these axons may also have more than one synaptic region. Both dinds of synaptic profiles are found on the somata and dendrits of all MSO neurons.

To determine which nerve endings are from the cochlear nucleus (CN) lesions were made to produce othograde degeneration. Following unilateral CN lesion degenerating spherical vesicle terminals were observed on the lateral dendrites and somata of ipsilateral central column cells and the medial dendrites and somata of contralateral neurons. Degenerating terminals were rarely seen on the opposite dendrite (three of 48 cells). In six of seven instances where medial and lateral dendrites of two cells overlapped degeneration was limited to the one oriented toward the lesion. Marginal cells examined received virtually all spherical vesicle terminals from only one CN. Terminals with flattened vesicles persisted on the somata and dendrites of all neurons studied including cells from cats with bilateral lesions.
Electron microscopical reconstruction of the anterior sensory anatomy of the nematode caenorhabditis elegans
Authors: Ward Samuel , Thomson Nichol , White John G. , Brenner Sydney
Published: January 2005

The complete structure of the anterior sensory nervous system of the small nematode C. elegans has been determined by reconstruction from serial section electronmicrographs. There are 58 neurons in the tip of the head. Fifty‐two of these are arranged in sensilla. These include six inner labial sensilla, six outer labial sensilla, four cephalic sensilla and two amphids. Each sensillum consists of ciliated sensory neurons ending in a channel enclosed by two nonneuronal cells, the sheath and socket cells. The amphidial channel opens to the outside as does that of the inner labial sensilla so that these probably contain chemoreceptive neurons. The endings of the other sensilla are embedded in the cuticle and may be mechanoreceptive. The cell bodies of all the neurons lie near the nerve ring and their axons project into the ring or into ventral ganglia. One of the ciliated sensory neurons in each of the six inner labial sensilla makes direct chemical synapses onto a muscle making these sensory‐motor neurons. The anatomy of four isogenic animals was compared in detail and found to be largely invariant. The anatomy of juveniles is nearly identical to that of the adult, but males have four additional neuron processes.
Ascending afferents to the telencephalon of ranid frogs: An anterograde degeneration study
Authors: Kicliter Earl , Northcutt R. Glenn
Published: January 2005

Sources of telencephalic afferents were examined in two species of frogs, Rana catesbeiana and Rana pipiens, by study of anterograde degeneration resulting from hemisection of the brain at the isthmus or at the caudal border of the thalamus and from electrolytic lesions in various portions of the diencephalon. The results indicate that some telencephalic afferents arise from levels caudal to the isthmus, that some striatal afferents arise from the level between the isthmus and the caudal border of the thalamus, and that a projection to the ipsilateral striatum arises from the anterior and/or middle portions of the dorsal thalamus. Diencephalic projections to pallial portions of the hemisphere were also observed. These results demonstrate substantial non‐olfactory afferent projections to the telencephalon in ranid frogs.
Autoradiographic studies of the projections of the midbrain reticular formation: Descending projections of nucleus cuneiformis
Authors: Edwards Stephen B.
Published: January 2005

The descending projections of nucleus cuneiformis in the cat were traced by autoradiography in the transverse and sagittal planes following stereotaxically placed injections of 3H‐leucine. Many descending axons are organized into distinct fiber systems, of which the largest and most well‐defined crosses directly in the midbrain and descends through the ventromedial tegmentum of the brain stem. This fiber system first terminates profusely in n. reticularis tegmenti pontis and then proceeds through the rhombencephalic tegmentum emitting transversely oriented branches to n. reticularis pontis caudalis and gigantocellularis, the raphe magnus and the facial nucleus. Its most caudal field of termination is a restricted portion of the medial accessory olive. Because of its size, compactness, and ventromedial course, this fiber system was termed the ventral tegmental bundle. In contrast, fibers descending on the ipsilateral side are more loosely organized and describe many divergent paths. In their initial course they remain in a dorsolateral position and distribute to the n. locus coeruleus, n. raphe dorsalis, the central gray matter, and n. reticularis pontis oralis. At successively more caudal levels they converge ventromedially and descend through the rhombencephalic tegmentum in a position similar to that of the ventral tegmental bundle. At the level of the facial nucleus a group of fibers splits off to form a separate fiber bundle which descends lateral to the inferior olive and distributes to the lateral reticular nucleus. No evidence was found of projections to the spinal cord or cerebellum. A portion of the tegmentum ventromedial to nucleus cuneiformis was found to project bilaterally to the facial nucleus and to the ipsilateral medial accessory olive. The results of this study are discussed in relation to the role of the midbrain reticular formation in the elaboration of certain forms of behavior.
The dorsal column nuclear projections to the nucleus ventralis posterior lateralis thalami and the inferior olive in the cat: An autoradiographic study
Authors: Groenewegen H. J. , Boesten A. J. P. , Voogd J.
Published: January 2005

This autoradiographic study demonstrates a topical projection of the dorsal column nuclei to the contralateral nucleus ventralis posterior lateralis thalami and the accessory part of the inferior olive. In contrast to earlier anatomical studies the projections of the gracile nucleus and the internal cuneate nucleus proved to be independent and entirely contralateral.

Fibers from the gracile nucleus terminate only in the lateral part of the nucleus ventralis posterior lateralis (VPL1) and from the internal cuneate nucleus only in the medial part of this nucleus (VPLm). Projections of the gracile nucleus to the contralateral inferior olive are restricted to the caudal one‐third of the medial accessory olive and the ventrolateral part of the dorsal accessory olive. The internal cuneate nucleus is only connected with the dorsomedial part of the rostral two‐thirds of the dorsal accessory olive.

Our material does not allow conclusions about projections from the dorsal column nuclei to other thalamic nuclei and about rostrocaudal point to point relationships between the dorsal column nuclei and the thalamus or the inferior olive.
Species differences in mechanosensory projections from the mouth to the ventrobasal thalamus
Authors: Bombardieri Rocco A. , Johnson John Irwin , Campos Gilberto B.
Published: January 2005

To determine whether the largely ipsilateral, inverted representation of mouth parts in the ventrobasal thalamus of sheep was unique to that species or an expansion of a general mammalian pattern, the corresponding thalamic projections were mapped electrophysiologically in a selected series of mammals (opossums, agoutis, squirrel monkeys, cats, raccoons, and sheep) representing major branches of evolution among therian mammals. In mapping, tungsten microelectrodes were used to record multi‐unit discharges in the thalamus in response to mechanical stimulation of oral surfaces. The pattern of projections seen in sheep is not a general mammalian pattern; there is extensive variability among mammals in the laterality and internal organization of the projections from the mouth. In spite of the great variability, the results suggest an hypothesis concerning phylogenetic trends: descendants of palaeoryctoid insectivores (cats, raccoons, and sheep in our sample) have extensive ipsilateral projections from the mouth, in other therian mammals (opossums, agoutis, and squirrel monkeys in our sample) the ipsilateral component is small or absent.
Ontogeny of monoamine neurons in the locus coeruleus, raphe nuclei and substantia nigra of the rat
Authors: Lauder Jean M. , Bloom Floyd E.
Published: January 2005

Synaptogenesis was studied in the monoamine (MA) cell groups locus coeruleus (LC), dorsal and medial raphe nuclei (RN) and substantia nigra, zona compacta (SN) between day 18 of gestation and postnatal day 60 using ethanolic phosphotungstic acid (E‐PTA) to visualize synaptic profiles. Nuclear area, and cellular packing density (inversely proportional to area of neuropil) were also determined.

As determined using the E‐PTA method, synaptogenesis begins in the neuropil of the SN first, on or before 18 days of gestation, and in the LC and RN at 19 days. Synaptogenesis on MA cell perikarya is first observed in the SN, on or before 18 days, and in the LC and RN at 20 days. The onset of somatic synaptogenesis coincides with the beginning of nuclear growth and development of the neuropil (decrease in cellular packing density) in all MA cell areas, raising the possibility of common factors in the initiation of these processes.

Nonsynaptic contacts precede the appearance of synaptic profiles both in the neuropil and on the somata of the MA cells of the LC, RN and SN, and may represent precursors of mature synapses or desmosome‐like contacts. Somatosomatic nonsynaptic contacts occur only prenatally between adjacent MA neurons in the LC, RN and SN.

Although some synaptogenesis occurs prenatally in these MA cell groups (indicating that these parts of the MA circuitry may be functional before birth), most of this synaptogenesis occurs postnatally and continues into adulthood. Since such synaptogenesis does not begin until 2–4 days prior to birth, whereas these neurons and their processes exhibit MA fluorescence as early as 12–14 days of gestation, they apparently are capable of synthesizing transmitter and proliferating terminals before they themselves are innervated.