bluuebunny/crossref_metadata_2025 huggingface dataset:
The distribution of autonomic nerves in the musculature of the rat vas deferens. A light and electron microscope investigation
Authors: Dixon J. S. , Gosling J. A.
Published: December 2004

Light microscope histochemical techniques and electron microscopy were used to study the distribution of autonomic nerves in the muscle coat of the rat vas deferens. Numerous fluorescent catecholamine containing nerves were demonstrated throughout the length of the vas; muscle cells on its inner aspect were particularly well innervated. This distribution differed markedly from that of acetylcholinesterase containing fibres, the majority of which occurred at the testicular end. Few similar nerves were observed in the muscle coat further towards the urethral end of the vas. The distribution of fluorescent and acetylcholinesterase‐positive nerves correlated well with the arrangement of adrenergic and non‐adrenergic terminal regions identified on permanganate fixed sections using the electron microscope. Their distribution was endorsed using 6‐hydroxydopamine to selectively damage adrenergic terminals. Adrenergic nerve terminals were frequently observed in isolation amongst smooth muscle cells while the non‐adrenergic type were almost invariably associated with other axons. The significance of these observations is discussed.
Topographical development of the ganglion cell fiber layer in the chick retina. A whole mount study
Authors: Goldberg Stephen , Coulombre Alfred J.
Published: December 2004

Three hundred and forty whole mounts of retinas from domestic fowl aged two days of incubation to several months post‐hatching were examined using a modified pyridine‐silver technique. The first visible ganglion cell axons appeared near the posterior retinal pole between two and three days of incubation. These early axons grew immediately toward the optic stalk and became grouped in fascicles even before reaching it. The fascicles increased in number, diameter and length, became interconnected and became more parallel and orderly with age. The mean fascicle diameter and concentration increased with nearness to the optic fissure. Growth cones were seen only in the most vitread portion of the fiber layer.

Two main groups of fascicles, one superficial and one deep, surrounded the head of the fissure by five days of incubation, each group entering the fissure at a different angle. At this time an arcuate pattern of fibers arose near the posterior pole of the retina. Fiber bundles were relatively thin and sparse in the center of this pattern. The distance between the fissure and the center of the pattern increased with age. The arcuate pattern virtually disappeared within several weeks, possibly indicating an abortive formation of a macula and fovea.

The fibers at the periphery of the older retinas ran parallel to the iris, encircling but not entering it. These circumferential fibers, which first developed on the temporal side of the retina and later nasally, diverged from a point on the dorsal periphery of the retina. The relative position of this divergence point swung about 90° around the retinal periphery between five and one‐half and eight days of incubation.

Probable centrifugal fibers were first seen at 17 days of incubation.
Xenoplastic eye transplantation between chick and quail embryos: Some neuroanatomical and functional aspects
Authors: Heaton Marieta Barrow
Published: December 2004

Xenoplastic eye exchanges were made between domestic chick and Bobwhite quail embryos, using microsurgical techniques at early stage 11. Donor (quail) eyes were found to be incorporated in 78% of the operations, and it was suggested that an optimal period (late stage 10 ‐ early stage 11, approximately 10.3 somites) exists, during which transplantation of these organs may be maximally successful. The majority of the transplanted eyes appeared normal, and histological examination revealed normally decussating and ingrowing optic nerves which formed normal appearing optic tracts and found terminations within the contralateral tecta. Inspection of donor retinae and the isthmo‐optic nuclei contralateral to the transplant, both known to undergo cellular degeneration in the absence of their appropriate projection fields, showed normal cellular complements and organization in most cases. Functional capacities of the transplanted eyes were assessed by viewing the pupillary light reflex. This test indicated that functional connections were made, at least as far as mesencephalic centers, with the latencies of and threshold intensities for elicitation of the reflex virtually identical in normal and transplanted eyes. The latencies of the reflex virtually identical in normal and transplanted eyes. The latencies of the donor (quail) eyes were considerably shorter than those usually found in these embryos at the age viewed. Some form of host induction of precocial responsiveness is discussed in this connection.
Reduction of the naturally occurring motor neuron loss by enlargement of the periphery
Authors: Hollyday Margaret , Hamburger Viktor
Published: December 2004

Motor hyperplasia following the enlargement of the periphery by implantation of a supernumerary leg is not due to “remote control” of proliferation, as shown by motor neuron counts in 6‐day chick embryos. We have tested the alternative hypothesis that we are dealing with reduction of the naturally occurring cell death. In normal development, the lumbar lateral motor column (l.m.c.) undergoes motor neuron degeneration resulting in a cell loss of at least 40%, which occurs between six and one‐half and nine and one‐half days. Following transplantation of supernumerary legs, cases selected for vigorous motility showed a numerical difference between experimental and contralateral (control) sides amounting to +11.0% to +27.5%. The transplants were innervated by varying combinations of thoracic and rostral lumbar nerves. We interpret our data in terms of survival of motor neurons which normally would have failed in a competition at the periphery but which were sustained by the enlarged peripheral fields. Our data do not permit a decision between the two alternatives: competition for synaptic sites or for a trophic agent. The surviving motor neurons are not limited to the rostral segments of the motor column but in most instances distributed along its entire rostro‐caudal extent, implying a redistribution of all l.m.c. axons. The term “hyperplasia” is no longer appropriate for the phenomenon under consideration and should be replaced by the term “hypothanasia.”
An ultrastructural morphometric study of mossy fiber endings in pigeon, rat and man
Authors: Paula‐barbosa M. M. , Sobrinho‐simões M. A.
Published: December 2004

Mossy fiber endings and their synapses have an increasing morphological complexity along the phylogenetic scale which is specially evident when the evolution from reptiles to birds is considered. Among birds and mammals, only scanty and merely qualitative differences have been noticed in the mossy fiber organization. In the present study, the mossy fiber endings organization within the neuropil of four pigeons, four rats and six men was studied at optic and ultrastructural levels using morphometric methods. No significant differences were found in the fraction of volume of the neuropil and in the number of granule cells per unit volume of granular layer in all the three species. In man, a significant decrease in the volume of mossy fiber endings per unit volume of neuropil, and significant increases in their surface‐to‐volume ratio, in the fraction of their neurolemma occupied by synaptic contacts and in the average length of their synaptic contact zones, were found. The total synaptic area of mossy fiber endings per unit volume of neuropil was larger in man than in other animals in spite of their more reduced volume.

These results show that significant differences in mossy fiber organization can be demonstrated when man is compared with a small mammal (the rat) and a bird (the pigeon). It is suggested that differences in the stereological organization of man's terminals might be related to his capacity for making finely graded movements. Moreover, it is suggested that the phylogenetic evolution of the mossy fiber organization has progressed among the higher vertebrates as it did in the rest of the animal scale.
Central projections of the chorda tympani nerve in the mallard, Anas platyrhynchos L
Authors: Dubbeldam Jacob L. , Karten Harvey J. , Menken Steph B. J.
Published: December 2004

The central projections of the chorda tympani nerve in the duck were studied by means of the Fink‐Heimer technique. Following section of the VIIth nerve proximal to the geniculate ganglion terminal projections of the CT are found in the sensory nucleus N VII (sVIId) on the dorsum of the descending trigeminal root, the n. presulcalis anterior solitarii, the n. sulcalis anterior solitarii p. dorsalis and p. ventralis, and the n. ventrolateralis anterior solitarii (Vla). Small quantities of terminal degeneration are also found in the n. intermedius anterior and the lateral substantia gelatinosa of the solitary complex. A number of fibers decussate to terminate contralaterally in corresponding portions of the opposite solitary complex. Comparison with data of the pigeon reveals a limited overlap of projections of the chorda tympani nerve and of the nodose ganglion, respectively, in the dorsal and ventral parts of the n. sulcalis anterior. We suggest that the regions sVIId and Vla alone may convey gustatory information.
The anatomical organization of the cerebello‐olivary projection in the cat
Authors: Tolbert D. L. , Massopust L. C. , Murphy M. G. , Young P. A.
Published: December 2004

The cerebello‐olivary pathway in the cat has been examined using orthograde and retrograde neuroanatomical tracing techniques.

The orthograde transport of 3H‐leucine from injection sites in the deep cerebellar nuclei labeled dentate and interpositus projections to the rostral two‐thirds of the contralateral inferior olivary complex. These projections are topographically organized, with the dentate nucleus projecting to the principal olivary nucleus and the posterior and anterior interpositus nuclei projecting to the medial and dorsal accessory olives respectively. Fibers from the ventral half of the dentate nucleus terminate in the lateral bend and ventral lamina of the principal olive, whereas the medial and lateral parts of the dorsal half of the nucleus project to the medial and lateral regions of the dorsal lamina respectively. It is apparent that the more caudal parts of the interpositus nuclei project to areas of the medial and dorsal accessory olives near the caudal end of the principal olivary nucleus, whereas neurons in the more rostral parts of the interpositus nuclei project to the more rostral areas of the accessory olivary nuclei. A connection between the fastigial nucleus and the inferior olive could not be demonstrated.

The retrograde transport of horseradish peroxidase (HRP) from injections sites in the inferior olive labeled cells throughout the contralateral dentate and interpositus nuclei. The labeled cells were especially numerous in the ventral parts of the dentate and posterior interpositus nuclei. These HRP‐positive neurons were consistently small (10–15 μ) ovoid or spindle‐shaped cells, with relatively large nuclei and light‐staining Nissl substance.

This evidence strongly suggests that the cerebello‐olivary pathway originates from a population of small neurons in the dentate and interpositus nuclei and projects to specific, topographically defined areas in the contralateral inferior olive.
Ultrastructure of the feline area postrema
Authors: Klara P. M. , Brizzee K. R.
Published: December 2004

The morphology of the feline area postrema (AP), a circumventricular organ, has been studied by scanning (SEM) and transmission electron microscopy (TEM). In SEM preparations the boundary of the AP was sharply delineated by the absence of kinocilia. Microvilli were numerous and seemed to be concentrated at the junction between ependymal cells, imparting a polygonal surface pattern superimposed on cell boundaries. Some cell processes were present on the AP surface, but no supra‐ependymal cell bodies could be seen over the AP proper. In TEM preparations the AP was characterized by blood vessels with distinct perivascular spaces. These spaces contained fibroblasts and collagen, and were limited by basal laminae. Capillary endothelial cells were typically fenestrated and contained numerous pinocytotic vesicles. Bulbous endings of attenuated cellular processes terminated on the external basal laminae of AP vasculature. Some of these endings could be traced to the cells covering the ventricular surface of the AP. These cells demonstrated several features common to ependymal cells which have been identified as tanycytes. The presence of small neurons frequently seen in groups of three or four confirm previous light microscopic studies. Synapses predominantly of the axodendritic variety were observed, and both dense cored and clear cored vesicles were present on the same ending. Myelinated and unmyelinated axons were a consistent finding in the AP with the former being more abundant in the lateral margins of the AP and in the region of the area subpostrema. The chemoreceptive function of the AP has been widely accepted; however, studies indicate that it is not possible to distinguish species possessing an emetic reflex on the basis of ultrastructural morphology. The possibility that the AP serves functions in addition to emetic chemoreception is considered.
Age‐related deterioration of pyramidal cell basal dendrites in rat auditory cortex
Authors: Vaughan Deborah W.
Published: December 2004

The basal dendritic trees of layer V pyramidal cells in the rat auditory cortex were examined quantitatively in a group of 3‐month‐old and a group of 34‐ and 36‐month‐old rats. Two forms of analysis were used on the Golgi preparations: (1) the number of intersections between the basal dendrites and a series of concentric circles whose common center lies over the perikaryon center, and (2) the number of dendritic branches, by order, per neuron. The data indicate that in the old animals the density of the dendritic tree has decreased significantly within a radius of about 150 μ of the perikaryon, yet the extent of the dendritic domain has not changed appreciably. Analysis of the dendritic branching suggests that there has been a deterioration not only in the peripheral branches of the dendritic tree, but also that entire dendrites have been lost. This loss of primary branches was confirmed through the reconstruction of layer V neuronal perikarya and their proximal dendrites from 1‐μ plastic serial sections of auditory cortex. Concomitant with the loss of dendrites which accompanies advancing age is a tendency for the perikaryon to be smaller, but not distorted, in the old animals.
The olivocerebellar projection in the cat studied with the method of retrograde axonal transport of horseradish peroxidase. IV. The projection to the anterior lobe
Authors: Brodal Alf , Walberg Fred
Published: December 2004

Following injections of horseradish peroxidase (HRP) in the cerebellar cortex of the anterior lobe of the cat, the distribution of labeled cells in the inferior olive was mapped. The findings largely confirm those made previously in studies of olivary retrograde cell loss following cerebellar ablations (Brodal, 1940b). In addition, they reveal further olivary areas projecting onto the anterior lobe, and permit a more detailed analysis of the pattern in this projection. Concerning major points the results are in agreement with physiological studies by Armstrong et al. (1974). They bring supporting evidence for a longitudinal zonal pattern in the anterior lobe (fig. 6C).

The middle zone of the vermis receives its fibers from a large central area in the caudal half of the medial accessory olive, a lateral zone of the vermis from the lateral half of the dorsal accessory olive. Both olivary areas project to the corresponding cerebellar zone throughout lobules V‐I.

The lateralmost part of the anterior lobe (lobules IV‐V) receives afferents from an area in the dorsal lamella of the principal olive. The intermediate part of lobules IV‐V receives afferents from the medial half of the dorsal accessory olive and from an area in the rostral half of the medial accessory olive. There is suggestive evidence that the latter projects lo a middle zone, the former to a medial and a lateral zone within the intermediate part as found physiologically. Conclusions concerning projections to the intermediate part of lobules III‐II could not be made.

The findings in this and preceding studies with the HRP‐method show that the concept of a longitudinal pattern in the cerebellum is scarcely generally valid of the entire olivocerebellar projection.

Within the projections of the lateral half of the dorsal accessory olive and the area in the rostral part of the medial accessory olive there appears to be a topical relation with the folial pattern in the anterior lobe.

An analysis of the findings with reference to the afferents traced anatomically to the various olivary areas permits some conclusions as to the functional role of the olivary areas. Comparison with Oscarsson's (1973) diagram of the sites of termination of two of the spinal‐olivary pathways (his DF‐SOCP and VF‐SOCP) permits an anatomical explanation as concerns the projections to the vermis, while correlations as concerns the intermediate part are less satisfactory.
The effect of cortical and tectal lesions on the visual fields of binocularly deprived cats
Authors: Sherman S. Murray
Published: December 2004

The visual fields of seven cats raised with binocular lid suture were measured before and after various neural lesions. Each of the cats preoperatively responded with each eye to stimuli from 90° ipsilateral through to the midline. A transection of the optic chiasm rendered one cat bline on the visual field tests. Large bilateral occipito‐temporal cortical ablations (4 cats) did not measurably affect orienting responses or the extent of visual field. Unilateral occipito‐temporal cortical ablations (2 cats) also had no affect on the visual fields, but subsequent ablations of the contralateral superior colliculus produced permanent blindness in the hemifield contralateral to the ablated tectum. These two cats also were apparently blind with the eye contralateral to the ablated tectum; but with the other eye, the cats retained their preoperative orienting responses. These data are consistent with the hypothesis that, with early binocular deprivation, cats develop dependence upon retinotectal and not thalamocortical pathways for visually guided orienting behavior.
An autoradiographic investigation of the subcortical visual system in chimpanzee
Authors: Tigges Johannes , Bos Jane , Tigges Margarete
Published: December 2004

Based on one adult chimpanze monocularly injected with radioactive proline, retinofugal fibers were found to terminate bilaterally in the suprachiasmatic, prgeniculate, lateral geniculate, olivary, pretectal and lateral terminal nuclei, and the superior colliculi; the existence of a dorsal terminal nucleus of the accessory optic system is in doubt. In the ipsilateral geniculat nucleus, the fibers terminat in layers 2, 3 and 5; in the contralateral nucleus, they end in layers 1, 4, and 6. Miday throuh the geniculate nucleus, 3 and 4 split medially into two daughter layers 3 and 4 split medially into two daughter layers each. In the superior colliculi, most of the retinal terminals are aggregated superficially in a band located in the stratum griseum superficiale. The contralateral band is interrupted by gaps; the ipsilateral band has fewer gaps, is slightly thicker and located more deeply. There is a limited second tier of terminals in the contralateral superficial gray.
The commissural projection of the superior colliculus in the cat
Authors: Edwards Stephen B.
Published: December 2004

The origin, course, and termination of the commissural projection of the superior colliculus were studied using the orthograde autoradiographic tracing method and the retrograde method utilizing horseradish peroxidase.

The complementary and mutually confirming sets of data showed that the commissural fibers interconnect a restricted region of the colliculi. This region includes the strata grisea intermedium and profundum and to a lesser degree the stratum opticum. It extends throughout only the rostral part of the colliculus where it ends abruptly at a level slightly less than half the distance from the anterior border of the deep gray layers. By using the needle used for isotope injection to record multiunit reponses to somatic and visual stimuli, direct evidence was obtained that this region falls within that functional area of the colliculus devoted to face representation and central vision. The results also suggested that more commissural fibers arise from lateral than medial parts of this region and that many fibers interconnect corresponding points in the colliculi. In addition to intertectal connections, the commissural projection contains decussating axons which terminate in tegmental structures and within a restricted zone of the central gray matter directly overlying the oculomotor complex.

The results are discussed in relation to the possible role the commissural projection plays in the regulation of eye and head movements.
Normal nerve fibers in the barrel region of developing and adult mouse cortex
Authors: Waite Phil M. E.
Published: December 2004

The pattern of normal nerve fibers associated with barrel‐shaped structures in the somatosensory cortex of both young and adult mice, has been studied using a reduced silver method. In adult animals, the [barrel] sides and septa can be seen to contain densely packed bundles of nerve fibers running vertically between layers III and V. In parasagittal sections, these fibers appear as very dark bands between adjacent barrels, while in tangential sections the fibers, cut in crosssection, appear as rings of dark spots concentrated around the barrel edges. In contrast to this, barrels in immature animals have dark, evenly stained centers and pale, cell dense sides. This immature pattern can first be distinguished in 2‐day‐old animals and persists until 18 to 19 days. Between 18 and 24 days a change from the immature to the adult pattern occurs with the appearance of darkly stained, fine fibers within layer IV, particularly within the barrel sides. It is suggested that the immature pattern is due, primarily, to the staining of thalamic afferents while the adult pattern appears with the development of intracortical and association fibers. Electron microscopy, on tissue previously treated by the silver method, shows that the silver deposits are mainly attached to longitudinal elements of the axoplasm and not associated with myelin. This may explain the success of this method in showing fibers in young, unmyelinated brains.
The prenatal development of some of the visual pathways in the cat
Authors: Anker Robyn L.
Published: December 2004

Lesions were made in the visual system in a series of cat fetuses of known gestational age, and fiber and terminal degeneration were stained by the Eager method.

The times of development of the retinal projection, of the thalamocortical and corticothalamic projections of area 17 of the visual cortex, and of the intrinsic fibers in the visual cortex were examined.

Enucleation of one eye resulted in degeneration being detected bilaterally in the lateral geniculate nuclei (LGN), superior colliculi (SC) and optic tracts. The optic nerves reached the optic chiasm by the thirtieth embryonic day (E30) and the optic tract connections with the LGN and SC were made by E37. The projection always appeared stronger in the contralateral LGN and SC, and the amount of degeneration increased in both sides with increasing age.

A parasagittal knife cut was made in the dorsomedial crest of the visual cortex. Where the lesion passed through the cellular layers of the cortex, intrinsic fibers were cut when these were present. The deeper part of the incision through the white matter undercut the medial wall of the visual cortex, interrupting thalamocortical and corticothalamic fibers when these were present.

The longer horizontal fibers that were intrinsic to the visual cortex began to develop during the last two weeks of gestation but were not fully developed at birth. In the undercut visual cortex distant from the place of entry of the lesion, and before the intrinsic fibers of the cortex had developed, degeneration was found in layers 1 and 4, demonstrating the presence of a thalamocortical pathway. The youngest fetus to show this degeneration was operated at E48. This degeneration was not present three days earlier at E45. Fiber plexuses that have been described earlier in development (Marin‐Padilla, '71; Cragg, 75) do not appear to degenerate after undercutting the cortex.

The corticothalamic pathway to the lateral posterior nucleus medial to the LGN was developed at E45. The descending pathways to the ipsilateral LGN and SC were developed by E48, but it is not known whether they are present before this.

Thus degeneration has been used to detect the development of axonal pathways in the fetus for the first time; the major afferent and efferent pathways are developed at an earlier stage than has previously been described.
A study of aging in the Human abducens nucleus
Authors: Vijayashankar Narayanakurup , Brody Harold
Published: December 2004

As part of a continuing study of the relationship between age and neuronal number within the human brainstem, the abducens nucleus was examined in a total of 20 brains. While the nucleus almost doubles in length between birth and adulthood, there is no significant change in cell number after birth. With the exception of some specimens which may indicate an individual variation, the average number of cells in this nucleus for all specimens examined was found to be 6,454. Approximately the same number is found in the nucleus of the newborn (6,500), confined within a length of 1.5 mm. With maturity, the nucleus enlarges to 3.0 mm but since the cell number does not significantly change, the cell density in any one section of the nucleus is considerably decreased, thus emphasizing the importance of absolute counts in such studies. At least among the brainstem nuclei already examined by various investigators it appears that neuronal loss is not a concomitant of aging as has been described for the cerebral and cerebellar cortices.
Projections from cortical visual areas 17, 18, and MT onto the dorsal lateral geniculate nucleus in owl monkeys
Authors: Lin C. S. , Kaas J. H.
Published: December 2004

Projections from cortical visual Areas 17, 18, and MT to the dorsal lateral geniculate nucleus of owl monkeys were revealed by the use of the autoradi‐ographic tracing method. Restricted injections of H‐proline into Area 17 resulted in dense columns of labeled tissue extending through all layers of the nucleus and roughly perpendicular to the layers. There was some lateral spread of the label in the interlaminar zones. Projections from Areas 18 and MT were distributed over the ventral layers of the nucleus including the magnocellular layers, layer S, and the adjoining interlaminar zones. The input from Area 18 was relatively sparse. The projections from all three cortical visual areas appear to connect hornotopic locations in the geniculate and cortical representations of the visual field.
The projection from the lateral geniculate nucleus onto the visual cortex in the cat. A quantitative study with horseradish‐peroxidase
Authors: Hollaänder Horstmar , Vanegas Horacio
Published: December 2004

Horseradish‐peroxidase (HRP) was injected (9‐18 μg in 0.03‐0.06 μl) into cortical areas 17, 18 or 19 of 11 adult cats. After survival times of 17 hours to 7 days, the thalamus was examined for retrogradely HRP labelled nerve cells in serial transverse sections. From these sections, the percentage of labelled cells occurring in each subdivision of the dorsal lateral geniculate nucleus (LGNd) was calculated for each animal. One case each for injections in areas 17, 18 and 19 was then chosen for nerve cell size measurements in each LGNd subdivision. The peri‐karyal area of each labelled cell (N=689), and of representative samples of unlabelled cells (N=1137), was measured by planimetry. Size distribution histograms, mean values, standard deviations, and statistical significance levels were obtained by computer.

It was found that area 17 receives a projection almost exclusively from laminae A and Al, and that the projecting cells belong to all cell size classes. Area 18 receives a projection mainly from laminae C and Al, and from the medial interlaminar nucleus (MIN). The projecting cells belong mainly to the large cell size classes. Area 19 receives a projection largely from MIN, and also from the C‐laminae and extrageniculate cell groups. The projecting cells belong to all cell size classes, with some emphasis on the large cells of lamina C. A significant projection was found to exist from the parvocellular laminae of LGNd onto area 19 and, to a lesser degree, area 18. In conclusion, as one goes from area 17 to 18 and to 19 the projection source shifts from the A‐laminae through the C‐laminae on to MIN and extrageniculate cell groups. The cells which project to area 18 are on the whole larger, than those which project to areas 17 and 19. A significant proportion of the contralateral visual input to area 18 is relayed via lamina G.

These results provide a quantitative confirmation and extension of previous anatomical findings, and are in close relationship with physiological results regarding parallel channel processing in the visual system.
The origin of spinocerebellar pathways. II. The nucleus centrobasalis of the cervical enlargement and the nucleus dorsalis of the thoracolumbar spinal cord
Authors: Petras J. M. , Cummings J. F.
Published: December 2004

The origin of spinocerebellar projections from the caudal cervical, the thoracic, and the cranial lumbar regions of the spinal cord was studied in neonatal dogs.

The present cytoarchitectonic and experimental studies of the cervical intumescence of the spinal cord led to the description of a cell group prominent in the dorsal horn, the nucleus centrobasalis. This nucleus, comprised of neurons of varying size and shape, extended over the length of the cervical intumescence. The largest neurons of then. centrobasahexhibited retrograde reaction following cerebellar injury or they accumulated horseradish peroxidase (HRP) after injection of the enzyme into the cerebellum. Unilateral cerebellar ablation or cordotomy evoked retrograde changes in the ipsilateral nucleus. The cerebellar‐projecting neurons were large, multipolar and chromatophilic. They occured singly, in small clusters, or in columns. The columnar arrangement was common at caudal levels of the cervical intumescence where these large cells were most abundant.

The results of earlier experiments with cats and rhesus monkeys have demonstrated massive fiber degeneration in then. centrobasahfollowing dorsal rhizotomy (Petras, '65, '66; Petras and Cummings, '72). The presence of spinal afferents in this nucleus suggests that its largest neurons may serve as a link for the passage of forelimb afferent information to the cerebellum by way of an uncrossed brachiospinocerebellar projection. The present anatomical data suggest too that these large neurons are the cells of origin for the rostral spinocerebellar tract (Oscarsson and Uddenberg, '64; Oscarsson, '65).

The cellular composition of the nucleus dorsalis was studied also, and the results compared with Loewy's ('70) findings in the cat. Three types of neurons were present in then. dorsalis. These have been classified as giant, medium, and small‐sized neurons. The giant and medium‐sized neurons responded to cerebellectomy, and accumulated enzyme following HRP injections into the cerebellum. The retrograde responses, generally, were most pronounced in cranial thoracic segments and diminished progressively in more caudal segments. Unilateral cerebellar ablations, cerebellar pedunculotomy, and cordotomy almost exclusively affected ipsilateral neurons. The present study provides the first demonstration of discrete retrograde changes in the giant cells of Clarke's column following cerebellectomy. The contribution of the medium‐sized neurons of then. dorsalisto spinocerebellar projections is established for the first time.
Projections to the spinal cord from medullary somatosensory relay nuclei
Authors: Burton H. , Loewy A. D.
Published: December 2004

Descending projections to the spinal card from the dorsal column nuclei were studied in the cat, rat and monkey with the retrograde horseradish peroxidase (HRP) technique, and in the cat with the autoradiographic anterograde axonal transport technique. Retrogradely labeled neurons were seen in the dorsal column nuclei after HRP injections at all levels of the spinal cord and additionally in the magnocellular division of the spinal caudalis nucleus of the trigeminal nerve after injections into cervical spinal segments in all three species. HRP‐positive neurons were predominantly located along the middle of the rostro‐caudal axis of the dorsal column nuclei and amongst the fusiform, triangular and polygonal cells that surround, especially ventrally, the cell nest zone containing thalamic relay neurons. The labeled neurons are densely concentrated in those portions of the dorsal column nuclei where most corticofugal and non‐primary afferent projections terminate and where the terminal distribution of primary afferent fibers is overlapping and diffuse. Previous studies have shown that most neurons in this middle and ventral region do not project to the thalamus or cerebellum. The majority of the cells in the dorsal column nuclei with descending axons or axon collaterals project by way of the ipsilateral dorsal columns, but some fibers project into the dorsolateral funiculus; the descending trigeminal fibers course in the dorsolateral funiculus. The terminal fields for these fibers in the cervical spinal cord include the lateral cervical nucleus, laminae IV and V, and possibly lamina I. These results indicate that the dorsal column nuclei may contribute to a feedback mechanism regulating the flow of sensory information ascending along other somatosensory spinal pathways.
The organization of the sensory and motor areas of cerebral cortex in the platypus (Ornithorhynchus anatinus)
Authors: Bohringer R. C. , Rowe M. J.
Published: December 2004

The organization of sensory and motor regions of the cerebral cortex has been studied in the platypus (Ornithorhynchus anatinus), of the order Monotremata. Comparisons were made with the organization found in the other representative of this order, the echidna, and with primitive species of eutherian and metatherian mammals. Evoked potential and single neuron studies revealed a large single area of somatosensory representation in the posterior region of the hemisphere, extending from an approximately mid‐sagittal position around to the region of the rhinal sulcus on the ventrolateral surface of the hemisphere. The mediolateral representation of contralateral body parts was consistent with the pattern in the primary somatosensory area of other mammalian species. No evidence of a second somatosensory area was found. Neurons with similar receptive fields were grouped in columns normal to the cortical surface and a highly ordered pattern of somatotopic representation was found. Within the large area of bill representation individual neurons had receptive fields which were often punctate and no more than 1 mm in diameter. They responded to dynamic components of tactile stimuli delivered to their receptive fields on the bill.

Movements on the contralateral side of the body could be elicited by bipolar electrical stimulation over an area on the dorsal surface of the hemisphere which largely overlapped the somatosensory area, but extended further anteriorly towards the frontal pole of the hemisphere. Visual and auditory projection regions were found overlapping the somatosensory area in the posterior part of the hemisphere. The auditory area overlapped the visual area and appeared to be displaced posteromedially in relation to its position in other species, a displacement which may be a consequence of the large expanse of cortical area associated with the bill.

The observation that a large proportion of cortical area is devoted to specific sensory and motor function in platypus corresponds with earlier findings in primitive eutherian and metatherian species. The platypus neocortex appears to represent a more primitive stage of cortical development than that found in the other member of the order Monotremata, the echidna.
The neural organization of the first optic ganglion of the principal eyes of jumping spiders (Salticidae)
Authors: Oberdorfer Michael D.
Published: December 2004

The first optic ganglion (FOG) of the principal eyes of jumping spider has been studied by both light and electron microscopy. Each FOG receives projections from the ipsilateral principal eye in a compact optic nerve. Some of the retinal axons, as they pass to the ganglion, cross in a chiasm within the optic nerve. The FOG is composed of a rind of nerve cell bodies which are unipolar cells giving rise anteriorly to second order nerve fibers in the central neuropile of the ganglion and posteriorly to processes which pass into the second optic ganglion. The neuropil is composed of neural and glial processes and of scattered glial cell bodies and it can be divided into a terminal zone and a fibrous zone. The terminal zone is the site of termination for all of the retinal axons. A unique feature of the retinal axon terminals is the presence of numerous fine post‐terminal processes extending away from the main portion of the retinal terminal. The fibrous zone is composed of second order nerve fibers with terminals in the terminal zone and it is continuous with a connective between the FOG and the second optic ganglion called the chiasm where the majority of the second order fibers cross.

All of the synapses in the FOG are modified ribbon synapses and occur in the terminal zone within ensheathed synaptic glomeruli as dyads or triads. Large retinal terminals containing pleomorphic vesicles are presynaptic to smaller second order terminals containing spherical vesicles. Second order terminals are also presynaptic to retinal terminals in addition to forming serial‐like synapses with each other.
Acetylcholinesterase staining in subdivisions of the cat's inferior olive
Authors: Marani E. , Voogd J. , Boekee A.
Published: December 2004

The present paper describes a unique distribution of true AChE activity in the IO. In the dorsal accessory olive three areas with high AChE activity can be distinguished. The medial accessory olive can be subdivided into a caudal part which shows rostro‐caudally directed bands with different enzymatic activity, and a rostral part which shows a more uniform, medium activity. In the nucleus beta and the dorso‐medial cell column, AChE activity is low. The ventral and dorsal lamellae of the principal olive contain areas with high, medium, and low activity. The dorsal cap is strongly positive, while the ventrolateral outgrowth is negative for AChE.

Enzyme distribution cannot be fully explained on the base of the known afferent and efferent connections with the IO. However, histochemical results provide evidence that generally supports a subdivision of the IO that mirrors these connections (Brodal, 1940; Armstrong et al., 1974; Boesten and Voogd, 1975; Groenewegen et al., 1975).
Ultrastructure of supraependymal cells and ependyma of hypothalamic third ventricle of mouse
Authors: Bleier Ruth
Published: December 2004

This study examines some ultrastructural features of the ependyma and supraependymal cells of hypothalamic third ventricle of the mouse in the region medial to the dorsomedial and ventromedial nuclei and dorsal part of infundibular nucleus. The brains of two males and 12 females in various phases of the estrous and reproductive cycle were studied.

In the ependyma, large variations were found in the incidence of various organelles and surface features both among ependymal cells and among animals. These variations suggest that different ependymal cells have different functions and that the hypothalamic ependymal layer as a whole reflects in its morphology changing metabolic states of the animal.

The main variations were found in the cytoplasm lying between the cell nucleus and ventricular surface. In some specimens the Golgi complexes were extensive and associated with many vesicles at the cell surface. Lipid‐like droplets may be large and abundant, sometimes bulging into the ventricle. Cytoplasmic surface protrusions may be large, irregular, and bulging with droplets, vacuoles or vesicles. These features, along with others, suggest a dynamic relationship between ependyma and cerebrospinal fluid (csf). Relations between tanycyte processes and neuropil are also described.

Supraependymal cells varied in incidence, the largest numbers being found in a proestrous, an estrous and a lactating mouse. Their shape and nucleus, the abundance of dense bodies and lysosome‐producing structures and other features suggest that many supraependymal cells are macrophages. Noteworthy in some cells were bizarre imtochondrial profiles associated with Golgi, endoplasmic reticulum, lysosomes and lipid droplets (GERL and LERL)

It is suggested that phagocytic supraependymal cells are engaged in processing the debris that results from changing metabolic activities, including secretion and exocytosis, blebbing and necrosis, of ependymal cells and also in the ingestion of foreign particles invading csf or ependyma.
Ultrastructural characterization of synaptosomes from neonatal and adult rats with special reference to monoamines
Authors: Kanerva Lasse , Tissari Anja H. , Suurhasko Birgit V. A. , Hervonen Antti
Published: December 2004

The crude mitochondrial fraction P2 and subfractions of it were prepared from the brain stem, hemispheres, hypothalamus and striatum of adult rats and from the hemispheres and brain stem or diencephalon‐mesencephalon and pons‐medulla oblongata of 1‐day‐old rats. Samples were fixed in glutaraldehyde‐osmium, KMnO4 or by Tranzer's triple fixation method (aldehydes‐chromate‐dichromate‐osmium) and examined by electron microscopy. With all these fixation techniques 80‐95% of processes in the adult samples were found to be mature synaptosomes. After incubation with either 10‐100 μg/ml of 5‐hydroxydopamine or α‐methylnoradrenaline, and after permanganate or triple fixation, monoamine synaptosomes, containing small granular vesicles were detected. They were found in all the brain regions studied and in the fraction P2 and subfractions C and D but only at a frequency of less than 1%. In samples from 1‐day‐old rats using the different fixatives, synaptosomes comprised 10‐30% of all processes. Nerve endings were at very different stages of maturation in sharp contrast to the rather uniform type of adult synaptosomes. They varied from processes still without any substructures to mature synaptosomes containing synaptic junctions. Monoamine synaptosomes containing small granular vesicles were detected after amine incubation and KMnO4 or triple fixation. Their frequency was lower than that in the adult. Most common were very immature terminals containing smooth endoplasmic reticulum and a very few small granular vesicles, indicating a very early appearance of the capacity to form small granular vesicles under experimental conditions. The immature terminals had all the characteristics of the growth cone and might partly have originated from growth cones at the tips of growing axons and dendrites. Less frequent were more mature synaptosomes containing a greater number of small granular vesicles and no longer any smooth endoplasmic reticulum. The crude microsomal fraction P3 was also examined in the adult brain regions and the brain stem of 1‐day‐olds. This fraction contained a small number of small agranular vesicles originating from cell bodies and nonterminal axons; their number was smaller in 1‐day‐old than in adult rats. The present results are in agreement with the high proportion of immature monoamine terminals in newborn rat brain detected earlier by fluorescence histochemistry.
Fornix system efferent projections in the squirrel monkey: An experimental degeneration study
Authors: Poletti Charles E. , Creswell George
Published: December 2004

The efferent projections of the fornix system have been studied in the squirrel monkey using modified silver staining techniques to delineate degenerating fibers and terminal boutons after inducing careful lesions of the subcallosal fornix and dorsal fornix.

Subcallosal fornix projections, after supplying the medial and lateral septal nuclei, are traced via precommissural fibers to terminal degeneration in the nucleus of the diagonal band of Broca, nucleus accumbens, gyrus rectus, olfactory tubercle, medial and lateral preoptic areas, and medial hypothalamus. Degenerating precommissural subcallosal fornix fibers course with the medial forebrain bundle throughout the extent of the lateral hypothalamus, extending caudally to the medial mammillary nucleus with specific hypothalamic offsets to the tuberal region and nucleus intercalatus (“lateral cortico‐hypothalamic tract”). Subcallosal postcommissural fornix fibers are traced to terminal degeneration in the bed nucleus of the stria terminalis and medial preoptic and anterior hypothalamic structures (“medial cortico‐hypothalamic tract”); fornix column fibers disperse throughout the perifornical nucleus; these fibers more caudally supply nucleus intercalatus and medial mamillary nucleus. In the thalamus postcommissural fibers supply the nucleus reuniens, the paraventricular, anterior ventral, and lateral dorsal nuclei. In the mammillary nucleus a laminated radiation is described with some fibers extending caudally to the prerubral field.

A “midline subcallosal stria,” derived from the subcallosal fornices, distributes fibers to the subfornical organ, the dorsal part of the medial septum, the precommissural fornix and especially the medial cortico‐hypothalamic tract.

The dorsal fornix projection is predominantly pericallosal to the gyrus rectus and parolfactory area, with only a minor callosal‐penetrating contribution to pre‐ and postcommissural fibers.

The composite projections of the hippocampal formation fornix system appear more extensive than those of the amygdala to basal forebrain, preoptic, and hypothalamic areas.