bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of the blood vessels and extracellular spaces during postnatal maturation of rat cerebral cortex
Authors: Caley David W. , Maxwell David S.
Published: December 2004

As part of a larger study of the development of postnatal rat cerebral cortex, this report deals with the maturation of the cortex as a tissue from birth to twenty‐one days of age. The changes in the numerical density of cells and blood vessels and the thickness of the cortex at successive ages were followed on light micrographs, and both were related to the ultrastructural observations on routine electron microscopic preparations. The maturation of the cortex is divided into two periods: The first ten days during which the growth to adult dimensions occurs and few patent blood vessels but large extracellular spaces are to be found, and the second ten days in which the majority of the vessels develop patent lumina, the perivascular sheath of astrocyte end‐feet develops, and the large extracellular spaces disappear concomitant with the maturation of the neuropil.

The blood vessels appear to develop during the first ten days as solid cords of mesodermal elements which form a network of primordial vessels with thick walls and slit‐like lumina containing a flocculent material. The formation of a blood filled, patent lumen apparently occurs synchronously over a brief period of time for the majority of the vessels during the early part of the second ten‐day period. The basal lamina is ill‐defined initially but takes on mature appearance parallel with the development of the perivascular glial sheath.

The volume of the extracellular space was found to be largest during the phase of rapid growth of axons and dendrites when few patent vessels exist. The disappearance of these large extracellular spaces during maturation of the blood vessels and neuropil is discussed in terms of the possible artifactitious nature of these spaces in both immature and mature cortex.
Thalamo‐cortical organization of the visual system in the cat
Authors: Niimi Kahee , Sprague James M.
Published: December 2004

Thalamo‐cortical relationships in the visual system of the cat were studied by the method of retrograde degeneration. Localized lesions limited to area 17 result in degeneration only in the dorsolateral geniculate body; cell changes are marked in 3 laminae (A, A1, B), mild in nucleus interlaminaris centralis and minimal in nucleus interlaminaris medialis. Lesions limited to areas 18 and 19 are followed by marked degeneration in the medial interlaminar nucleus, mild in the other laminae; in addition, the lateral part of the posterior thalamic nucleus (ventral or inferior pulvinar) is also atrophied. Following large striate lesions which marginally involved areas 18 and 19, there is also mild, localozed degeneration in the anteroventral and reticular thalamic nuclei. Whin cortical lesions are limited to the convexity of the suprasylvian gyri, degeneration is present in the lateral aspect of laminae A, A1, B and nucleus interlaminaris centralis and in the medial part of the posterior nucleus, in addition to lateral dorsal, lateral posterior and pulvinar nuclei. Lesions in the ectosylvian gyri result in slight but definite degeneration in the lateral part of lamina A of the dorsal lateral geniculate, but nothing in the posterior nucleus. The geniculate projections to areas 17, 18 and 19, to the suprasylvian and ectosylvian gyri all show a rostrocaudal organization. The geniculostriate projection is also topographically organized in a mediolateral manner.

Thus, the geniculocortical projection in the cat is not striate specific but spreads over the occipito‐temporal cortex at least as far as the acoustic areas of the ectosylvian gyri. In this species the dorsal lateral geniculate body is not a unitary structure but is a complex of nuclei, all of which receive retinal fibers, and the cortical projections of which overlap those of the posterior, lateral dorsal, lateral posterior, pulvinar, medial geniculate, reticular and anterior thalamic nuclei.
The amygdala of the box turtle, Terrapene c. carolina
Authors: Carey Joshua H.
Published: December 2004

The amygdala of the box turtle lies beneath the posterior hypopallial ridge. Three nuclear groups may be distinguished in it: (1) the anterior amygdaloid area, (2) the basolateral group and (3) the corticomedial group. The anterior amygdaloid area shows no subdivisions; its location ventral and ventromedial to the caudal part of the small‐celled portion of the piriform area is evident. The basolateral group is subdivided into lateral and basal amygdaloid nuclei. The interconnections of this group through the anterior commissure with the comparable area in the opposite amygdala and with the corticomedial group indicate that it is functionally a vicarious cortex. The corticomedial group is divisible into medial and cortical amygdaloid nuclei. The medial nucleus is poorly defined. The cortical nucleus is bounded by the medial amygdaloid nucleus on the medial side and the ventral border of the piriform cortex laterally, and is comparable to the cortical amygdaloid nucleus of higher vertebrates.

The lateral olfactory tract arises from mitral cells of the olfactory bulb and accessory olfactory bulb and neurons of the anterior olfactory nucleus. The lateral part of the anterior olfactory nucleus, the lateral and the intermediate parts of the tuberculum olfactorium and the small‐celled part of the piriform cortex contribute to and receive fibers from the lateral olfactory tract. The lateral olfactory tract sends fibers to the anterior amygdaloid area and the corticomedial group. The lateral corticohabenular tract has an anterior and a posterior division. The anterior division arises from cells of the nucleus of the lateral olfactory tract and the lateroventral portion of the piriform cortex. It is joined by those fascicles arising in the corticomedial group and designated as the amygdalohabenular tract. This tract crosses in the habenular commissure and retraces its course to enter the corticomedial amygdaloid nuclear group on the side opposite its origin. The basolateral group is interconnected through the anterior commissure.

The stria terminalis contains three components which interconnect the corticomedial amygdaloid nuclear group with the septum, the preoptic area and the hypothalamus. The supracommissural and the intracommissural components relate the cortical and the medial nuclei to the septum, the preoptic area and the hypothalamus of the same side. The infracommissural component interconnects the cortical and the medial amygdaloid nuclei with the septum, the preoptic area and the hypothalamus of the same and the opposite side.

The dorsal and the ventral olfactory projection tracts arise from the corticomedial amygdaloid nuclear group. They terminate in the preoptic area and anterior hypothalamus.
Viscerotopic organization of the vagus
Authors: Kerr F. W. L. , Hendler N. , Bowron P.
Published: December 2004

The represetation in the vagal rootlets of visceral efferent fibers to the heart and to the smooth muscle of the bronchi, esophagus and duodenum has been investigated in cats whose vagus had undergone chronic selective rhizotomies.

Cardiodecelerator fibers are well known to be the caudal rootlets and this was confirmed. Motor fibers to the esophagus and to the bronchi are present at all levels, while effernts to the duodenum are limited to the caudal fibers of the root complex.

Because the vagal efferents emerge in the same plane as their somata, these data have been extrapolated to the medullary centers.
The axonal pathways of spinal neurons in the cat
Authors: Matsushita Matsuo
Published: December 2004

The axonal pathways of spinal neurons were studied in the cat using Ramón y Cajal's silver method.

The cells of the ventral group of the nucleus supraspinalis contribute to the ventral roots of C1 and the cells of the dorsal group send their axons to the contralateral ventral funiculus. The cells of lamina VII send their axons to the ipsilateral lateral or ventrolateral funiculus. The subnucleus ventralis of the nucleus medullae oblongatae centralis sends axons to the lateral funiculus or to the ventral roots of C1. The cells of lamina V send their axons to the lateral funiculus and the contralateral ventral funiculus. The cells of lamina VII send their axons to the ipsilateral lateral funiculus and to the contralateral ventral funiculus. Numbers of spinal border cells were were observed in lamina IX at the level of the cervical and lumbar enlargement. It was found that the cell groups which were classified cytoarchitectonically contained numbers of different types of cells as judged by their axonal pathways.
The lateral cervical nucleus of cat, dog and man
Authors: Truex R. C. , Taylor M. J. , Smythe M. Q. , Gildenberg P. L.
Published: December 2004

This nucleus was identified in four cats, four dogs and nine human spinal cords, but was not identifiable in seven other human specimens. In all three species the nucleus extends rostrally into the lower third of the medulla. Cell measurements of the perikarya yielded a mean diameter of 34.1 μ in the dog, 26.7 μ in the cat, and 15.7 μ in man. Nuclear diameters as well as the nucleus‐cytoplasm and volume ratios were determined. The lateral cervical nucleus is considered to be rudimentary in man and was a well‐defined structure in only 2 of 16 specimens. In one of these two cases a total of 5173 cells were counted in the nuclei of both sides at the C1 and medullary levels. The pertinence of these observations to the preservation of tactile sensation after injury of the dorsal columns in man, is discussed.
Postnatal maturation in the cochlea of the cat
Authors: Pujol Remy , Marty Robert
Published: December 2004

At birth, the cochlea of the cat, though generally developed, is still immature. Maturation of the organ of Corti begins at the base and gradually reaches the apex. In two weeks the process is complete. The most significant morphological criteria of the epithelial maturation are the formation of the tunnel of Corti and of the space of Nuel, the lengthening of the outer hair cells and the freeing of the internal spiral sulcus. On the third day after birth, the appearance of these criteria at the level of the first coil of the lamina spiralis coincides with the general physiological awakening of the auditory systems, as testified by the recording of evoked potentials from the cerebral cortex. Since such responses can be provoked by electrical stimulation of the nerve from birth onwards, the maturation of the organ of Corti appears to be the final stage in the development of the auditory system.
Time of neuron origin in the diencephalon of the mouse. An autoradiographic study
Authors: Angevine Jay B.
Published: December 2004

Time of origin of neurons of thalamus ventralis, thalamus dorsalis, and epithalamus was determined autoradiographically at three transverse levels in adults which received thymidine‐H3 once during gestation. A ventrodorsal gradient in the entire region demonstrates a wave of neuron origin in the forebrain, probably rostrocaudal originally but revectored by rearrangement of neuromeres I–III. A caudorostral gradient in dorsal thalamus similarly may represent redirection of an earlier ventrodorsal one. A lateromedial gradient in dorsal thalamus and epithalamus (opposite that in cortex) may reflect lateral displacement of neuroblasts (or their nuclei) by younger elements. Large neurons generally arise before small ones, as seen in epithalamus; the two habenular nuclei illustrate programmed origin of large and small neurons and glia consecutively, with progressively restricted potentiality by the primitive ependyma. Phylogenetically, slight differences in duration of proliferation might radically alter the numbers of small neurons. Although dorsal thalamic nuclei “appear” in external germinal and mantle layers, their neuroblasts originate in primitive ependyma; time of origin accords with subsequent recognition of nuclei and appearance of thalamocortical connections. Massive proliferation (from the 10th to 15th days of gestation) and the gradients overshadow nuclear differences and demonstrate a developmental unity in the dorsal thalamus. The findings further validate Herrick's diencephalic zones and suggest some orderly mechanism, probably at the molecular level, underlying generation of the neurons in this complex brain region.
Thalamo‐cortical projections in the tree shrew (Tupaia glis)
Authors: Diamond I. T. , Snyder M. , Killackey H. , Jane J. , Hall W. C.
Published: December 2004

Cortical lesions were placed in 18 hemispheres, and thalamic degeneration was studied after a survival period of at least six weeks. Very small lesions within the striate area produced complete degeneration of neurons in a column through the lateral geniculate, from medial to lateral borders and comprising all of the laminae. Lesions of various loci within the striate area reveal a precise topographic projection, with the rostral lateral geniculate sending fibers to the caudal extremity of the striate area and the caudal lateral geniculate projecting to the rostral extremity of the striate; further, the dorso‐ventral dimension in the lateral geniculate projects to the medio‐lateral dimension in the striate area. Finally, the evidence from striate area lesions suggests that the lateral geniculate projections are confined to the striate area as defined by cytoarchitecture, which in turn corresponds precisely with visual area I as defined by electrophysiological recording. This conclusion is supported by the failure to find retrograde degeneration after lesions of the belt of cortex adjacent to the striate area. The temporal area which occupies an extensive section from V II to the rhinal fissure and the auditory cortex and which has been shown to be a visual receiving area, is the target of essential projections from the pulvinar. The pulvinar also sends sustaining collaterals within the temporal area and probably outside as well, especially to V II. However, the very crude topographic organization apparent in the pulvinar projections does not seem to be sufficiently refined to account for the organization of V II. A suggestion was made in closing that V II may be the result of convergent evolution in different mammalian lines of descent.
Functional variation in dermatomes in the macaque monkey following dorsal root lesions
Authors: Kirk Edwin J. , Denny‐Brown D.
Published: December 2004

Previous definitions of dermatomes, in various species, have revealed a characteristic pattern of serial overlapping root areas. Most investigators have used either the method of “remaining sensibility” or recordings of dorsal nerve root potentials, and have sectioned the dorsal nerve roots within the spinal canal, proximal to the dorsal root ganglia.

We have used the method of “remaining sensibility” in experiments in macaque monkeys. Section of the neighboring dorsal roots proximal to their ganglia produced dermatomes which resembled closely those isolated by Sherrington. However, we found consistently that when the neighboring spinal nerves were sectioned distal to their dorsal root ganglia, the isolated root areas on the trunk were approximately twice as large as before and now also showed persistent hyperesthesia. Re‐sectioning of the dorsal roots of these nerves within the dura reduced the isolated root areas to their “classical” size, but usually only after a delay of three or four days. The injection of subconvulsive doses of strychnine sulfate solution produced an enormous expansion of an isolated dermatome, irrespective of whether the neighboring roots had been sectioned intradurally or beyond their ganglia; no change in area was observed after the injection of morphine sulfate solution. Conversely, the size of a dermatome which had been isolated by intradural section of three dorsal roots above and below was reduced by subsequent section of three additional roots above and below.

We have concluded that the observed size of an isolated dermatome is a variable quantity and can be taken as an index of the efficiency of sensory transmission within the same and neighboring segments of the spinal cord.
The salivatory nuclei in the brainstem of the monkey (Macaca mulatta)
Authors: Bijlani Veena , Keswani N. H.
Published: December 2004

By inducing retrograde degeneration the salivatory nuclei were localized in the brainstem of the Macaca mulatta. It was observed that the neurons sending efferent fibres to the three salivary glands lie in two discrete groups, the lateral and medial salivatory nuclei situated under the floor of the fourth ventricle at the level of the pontomedullary junction. The lateral nucleus was in close relation to the medial and lateral vestibular nuclei, was about 0.3 mm long and consisted of mediumsized neurons. The medial nucleus was situated close to the median raphe, was about 0.5 mm long and consisted of smaller‐sized neurons. The caudal parts of the nuclei showed evidence of sending fibres to the ipsilateral glands, the cranial parts to the contralateral glands, and that the intermediate zones sent fibres bilaterally.
A quantitative study of the purkinje cells in the cerebellum of the albino rat
Authors: Armstrong David M. , Schild Renée F.
Published: December 2004

Histological techniques have been used to study the layer of Purkinje cells in the cerebellum of the albino rat. A method has been devised for “unfolding” the layer into two dimensions. The shape after unfolding strikingly resembled the shape of the unfolded human cerebellar cortex. The total area of the Purkinje cell layer after histological processing was estimated at between 270 and 280 mm 2 in four rats, and at 240 mm 2 in a fifth. Approximately 25% of the layer lies rostral to the primary fissure. In each of three rats the mean density of cells in the Purkinje cell layer was approximately 1,200 cells/mm2. There were considerable local variations in cell density. In these theree rats the total number of Purkinje cells present in the cerebellar cortex was estimated to be 3.2 × 105, 3.2 × 105 and 3.6 × 105 cells. The limitations of the methods used have been discussed.
Projection fibers from the main sensory trigeminal nucleus and the supratrigeminal region
Authors: Mizuno Noboru
Published: December 2004

Fiber projections from the main sensory trigeminal nucleus and the supratrigeminal region (reticular formation dorsal and rostrodorsal to the motor trigeminal nucleus) in the cat and monkey have been studied by the Nauta, Fink‐Heimer and Marchi methods.

Following experimental lesions in the main sensory trigeminal nucleus and its vicinity, the crossed ventral and the uncrossed dorsal trigeminal tracts were traced rostrally to the posteromedial ventral nucleus of the thalamus. The uncrossed dorsal trigeminal tract ascended through Forel's tegmental fascicle (tractus fasciculorum tegmenti Foreli). However, Forel's tegmental fascicle was composed mainly of the ascending reticular fibers terminating in the intralaminar nuclei of the thalamus and in the subthalamus. Commissural components distributing chidfly to the motor trigeminal nucleus of the opposite side appeared to arise from the supratrigeminal region as well as from the main sensory trigeminal nucleus. A fiber bundle, arising from the reticular zones surrounding the motor trigeminal nucleus, descended through the lateral reticular formation immediately ventromedial to the spinal trigeminal nucleus down to lower levels of the medulla oblongata.

The functional significance of the supratrigeminal region as an interneuron system intercalated between the trigeminal sensory and the cranial motor systems is discussed.
Anatomy of cultured mouse cerebellum. I. Golgi and electron microscopic demonstrations of granule cells, their afferent and efferent synapses
Authors: Wolf Merrill K. , Dubois‐Dalcq Monique
Published: December 2004

The development of granule cells and their connections was reinvestigated in organotypic cultures of cerebellum. Modified Golgi‐Cox preparations showed numerous maturing granule cells, some with fully mature claw‐shaped dendritic endings, within presumptive cortex. Large cortical neurons often had dendrites richly encrusted with synaptic spines. Sometimes bundles of thin parallel processes were oriented orthogonally to the spiny dendrites. Semithin sections and electron micrographs showed granule cell somas distributed in closely packed clusters, with directly apposed cell membranes. Several types of glio‐glial membrane apposition were observed, including extensive desmosome‐like junctions. The neuropil contained closely packed bundles of thin parallel processes and numerous synaptic complexes, often within the parallel bundles. The postsynaptic elements, when identifiable, often proved to be dendritic spines; axodendritic and axosomatic synapses were less common than axospinous. A few synaptic complexes resembled glomeruli, with linked granule cell dendrites surrounding a presynaptic element. The concurrence of several lines of evidence proves the identity of granule cells in presumptive cortex, but the existence of basket and Golgi Type II neurons and the source of presynaptic element in the glomerulus cannot be demonstrated. The criteria and importance of rigorous cell identification in cultures are discussed.
The inner plexiform layer of the vertebrate retina: A quantitative and comparative electron microscopic analysis
Authors: Dubin M. W.
Published: December 2004

The inner plexiform layer of human, monkey, cat, rat, rabbit, ground squirrel, frog and pigeon retinas was studied by electron microscopy. All showed the same qualitative synaptic arrangements: bipolar cells made dyad ribbon synapses onto amacrine and ganglion cells; amacrine cells made conventional synaptic contacts onto bipolar, ganglion cells; amacrine cells montage of electron micrographs through the full thickness of the inner plexiform layer were made for each species and were scored for synaptic contacts. Both absolute and relative quantitative differences were found between species. The ratio of amacrine cell (conventional) synapses to bipolar cell (ribbon) synapses, the absolute number of amacrine cell synapses and the number of inter‐amacrine cell synapses were all found to be higher in those animals which are known to have relatively complex retinal ganglion cell receptive field properties. It is suggested that the amacrine cell is involved in mediating complex visual transformations in certain vertebrate retinas.
Distribution of thymidine‐H3 in the overgrown brain of the chick embryo
Authors: Wilson Doris Burda
Published: December 2004

The pattern of incororation of thymidine‐H3 was studied in chick embryos in which overgrowth was experimentally induced in the optic tectum. Radioautograhs were prepared for experimental and control embryos ranging in age from three to five days' incubation at post‐label periods of one hours, and eight hours. Under conditions of overgrowth, S‐phase cells are situated not only in the periphery of the wall of the tectum, but are also found scattered among mitotic cells along the ventricular border. Labeled intraventricular cells are commonly seen in the defective brains. The onset of neuroblast differentiation, as indicated by a loss in ability of certain cells to incorporate thymidine‐H3, appears to be the same in the tectum of experimental and normal embryos and takes place toward the end of the fourth day of incubation. As development continues, the pattern of labeling becomes increasingly distorted in the severely affected potions of the overgrown tectum, and neuroepithelial cells become interspersed among differentiated neuroblasts.
Projections of the subnucleus caudalis of the trigeminal nucleus in the sheep
Authors: Roberts P. A. , Matzke H. A.
Published: December 2004

A study has been made of the efferent connections of the trigeminal sibnucleus caudalis in 12 shep. Lesions were placed in this nucleus either surgically or by means of an electrical cautery device. Resulting degeneration was determined by staining serially prepared frozen sections according to the silver techniques of Nauta and Fink‐Heimer. Ipsilateral connections are desribed with the fifth, seventh eleventh and twelfth cranial nerve motor nuclei, and ascending ipsilateral connections with all of the more rostral portions of the trigeminal nuclear complex. Evidence of widespread bilateral trigemino‐reticular connections is reported. By contrast, only a small number of fibers from the subnucleus caudalis were found to ascend in the mdial lemniscus; few of these lemniscal fibers appear to ascend beyond mesencephalic levels.
Neuron‐glia relationship during granule cell migration in developing cerebellar cortex. A Golgi and electonmicroscopic study in Macacus rhesus
Authors: Rakic Pasko
Published: December 2004

The cytology of the postmitotic migratory granule cell and its relationship to Bergmann glial processes was examined with Golgi staining and electron microscopy in the three cardinal planes in the developing cerebellar cortex of Macacus rhesus at various late fetal and early postnatal ages. After final mitosis the granule cell body transforms from a nearly round shape in the superficial zone of the external granular layer to a horizontal bipolar form with elongated processes oriented longitudinally to the folium, at the outer border of the molecular layer. Another descending process develops, and the cell soma becomes a pyramid flattened in the plane longitudinal to the folium. The nucleus moves into the descending process and the cell soma assumes a vertically oriented spindle shape while migrating among previously formed parallel fibers deeper in the molecular layer, and finally attains a round shape again when it lies deep to the Purkinje cell layer. During these transformations, the cell cytoplasm becomes more voluminous and contains a prominent Golgi apparatus, numerous free ribosomes, mitochondria, multivesicular and dense bodies, and fascicles of microtubules Longitudinally oriented microtubules concentrated in the vertical leading process disappear by the time the cell soma enters the granular layer. The slender trailing process loss most of its cytoplasmic organelles, acquires microtubules and together with the horizontal processes forms the characteristic T‐shaped axon. The axon forms synapses with Purkinje and stellate cell dendrites at a time when other granule cells are still migrating among them.

During the entire course of their migration across the molecular layer, granule cells are directly apposed to vertically oriented Bergmann fibers belonging to the Golgi epithelial cells. The sequence of developmental stages indicates that Golgi epithelial cells are a type of protoplasmic astrocyte. The Bergmann fibers were present at all stages examined, and their constant apposition to granule cells suggests a role in the lartter's migration. Numerous electronluscent beady enlargements are seen along the fiber except at sites were the surface is in contact with migrating cells; probably these enlargements change position as the granule cells pass along the Bergmann fiber. Lamellate expansions also project from the main shaft of the glial fiber and envelop the synaptic sites on spines of Purkinje cell dendrites. These expansions seem more durable, and the young neuron appears to avoid collision with them by sprialling around the glial shaft during its descent to the granular layer. The neuron‐glia relationship apparently provides the necessary conditions for the migration of the young granule cell. Especially at late developmental stages when the molecular layer is more than 250 μ wide and is densely packed with highly oriented cell processes that have already established synaptic connections.
Synapses made by myelinated fibers running to teleost and elasmobranch retinas
Authors: Witkovsky Paul
Published: December 2004

Myelinated fibers are described in teleost (carp, goldfish) and elasmobranch (dogfish) retinas which make synapses onto amacrine cell bodies and bipolar cell terminals. The fibers run in parallel with bundles of optic nerve fibers radiating from the optic disk until at some point they traverse the inner plexiform layer, turning again horizontally to course under the layer of amacrine cell bodies for 0.5–0.75 mm. En route each fiber makes several en passant synapses characterized by a cessation of the myelin sheath, a local increase in axonal diameter, an accumulation of agranular vesicles 300–400 Å in diameter and increased densification of pre‐ and post‐synaptic membranes. These fibers are not post‐synaptic to any retinal element. The evidence that the myelinated fibers described form an efferent system is based on their resemblance in many particulars to the centrifugal fiber system innervating the pigeon retina. Degeneration experiments, however, could not distinguish conclusively between a true efferent system, originating in some central nucleus, and a recurrent collateral system branching from afferent optic nerve axons.
Changes in the numbers of neurons and glial cells in the lateral geniculate nucleus of the monkey during retrograde cell degeneration
Authors: Mihailović Ljubodrag T. , Čupić Dragoslava , Dekleva Nikola
Published: December 2004

The time‐course of disintegration of neurons, and the concomitant reactions of various types of glial cells, in the dorsal nucleus of the lateral geniculate body (LG) were studied in 12 Rhesus monkeys sacrificed in groups of two at time intervals of 1, 3, 6, 12, 25 and 50 weeks following unilateral removal of the occipital lobe. The change in the mean number of neurons, astrocytes, oligodendrocytes and microglia, found per unit of volume, in Nissl preparations, of the degenerated LG, was expressed as a percentage of the mean number of the corresponding cells estimated in the normal LG on the same slide. The number of degenerating neurons decreased progressively. While 12 weeks following surgery a few isolated nerve cell nuclei could still be seen in the LG, by the end of the twenty‐fifth postoperative week the nucleus was practically devoid of neurons. The reaction of the astrocytes indicated a biphasic process—proliferation with subsequent reversal to an almost normal level. The oligodendrocytes and microglia multiplied at a somewhat slower rate, but remained far above the control values over a period of 50 postoperative weeks.
Projection of dorsal column nuclei and spinal cord to brainstem and thalamus in the tree shrew, Tupaia glis
Authors: Schroeder Dolores M. , Jane John A.
Published: December 2004

The aim of this study was to compare the projections of the dorsal column nuclei and spinal pathways to the brainstem and thalamus in Tupaia glis. Animals with unilateral lesions in the dorsal column nuclei or with lateral hemisections were perfused after 5 to 14 days survival time and sections were treated with Nauta or Fink/Heimer silver impregnation methods. The findings indicate that efferent fibers of dorsal column nuclei terminate not only in the thalamus but also in the dorsal accessory nucleus of the inferior olive and bilaterally in the external nucleus of the inferior colliculus. Some fibers terminate in periaqueductal gray and a few in pontine nuclei. In the diencephalon, efferents of the dorsal column nuclei were found to terminate in the posterior group (PO), ventroposterior nucleus (VP) and zona incerta. Spinal efferents were traced to the medial and dorsal accessory nuclei of the inferior olive, medullary and mesencephalic reticular formation, facial and vestibular nuclei, cuneiform nucleus, locus caeruleus, parabrachial nuclei and periaqueductal gray, and also to the external nucleus of the inferior colliculus. Evidence was found of more limited additional spinal projections to PO intralaminar nuclei and VP. The results of this study indicate that the dorsal column system, generally considered to be a phylogenetically new direct pathway to the thalamus, contains other components comparable to some of the spinal efferent connections with the brainstem. Moreover, even in this intermediate form, whose exact taxonomic position is unsettled, the dorsal column‐medial lemniscus system to the thalamus appears to be of greater volume than the anterolateral spinothalamic connection.
Histogenesis of the cerebellar climbing fiber in the rat
Authors: O'Leary James L. , Inukai Joseph , Smith Jeanne M.
Published: December 2004

Early climbing fiber metamorphosis has been studied in 250 Golgi preparations of 5–12 day postnatal rat cerebellum, and in less numerous 12–18 day ones. EM controls were provided for the early phase covering maturation of Purkinje cytoplasm, status of axonal neuropil, and synapses between the evanescent nid structure and Purkinje soma membrane.

Ramon y Cajal (1890, '11), Athias (1897) and others have contributed extensively to climbing fiber histogenesis. Our results are confirmatory but support more varied developmental detail including that of axonal collateralization within the granular layer, all of which may not persist to maturity. Distinguishing characteristics of climbing fibers are recognized early in histogenesis, including varicosities, redundancies in course, and a manner of branching called cross‐over. The curvaceous path a climbing fiber pursues across the granular layer can be corrected at the ganglionic level by a horizontal segment having length equivalent to the offset. These and other redundancies may straighten out with areal expansion of cortical surface as compared to the restricted white matter base.

While supporting multiple innervation of nids by local collateralizations proceeding from stem axons in white matter, the study does not preclude a one to one relationship between adult climbing fiber and Purkinje cell as basic design. Unknown factors are the relative amounts of local collateralization proceeding from several versus a single axon stem, and the extent to which branches are issued from a single fiber to different folia.
Ipsilateral afferents to the commissural zone of the fascia dentata, demonstrated in decommissurated rats by silver impregnation
Authors: Zimmer Jens
Published: December 2004

An ipsilateral pathway to the commissural zone of the dentate fascia has been demonstrated in the rat using the Fink‐Heimer silver impregnation method. The pathway arises in one or both of the CA3c and CA4 hippocampal subfields. As lesions of these structures normally will cause degeneration of commissural fibers terminating in the dentate fascia, animals without commissural fibers were provided for this study. This was done by transecting the hippocampal commissures in eight day old rats which were allowed to survive until the adult stage at which time all stainable, degenerating commissural fibers had disappeared. Lesions involving the CA3c/4‐subfields were then made. The resulting degeneration in the commissural zone of the dentate fascia was shown to be of purely ipsilateral origin.

Fibers of this pathway display a spread along the longitudinal septotemporal axis of the hippocampal formation. The spread in the “septal” direction (ascent) is in general greater than the descent in the temporal direction, and the more “septal” the lesion is placed, the further does the degeneration extend in the septal direction. The most ascending fibers occupy a juxtagranular position along the medial crus of the dentate granule cells. The most descending (temporal) fibers are seen superficially in the commissural zone along the lateral crus.

The pyramids of CA3c and the modified pyramids of CA4 are considered the most probable cells of origin of this system.

The ipsilateral system may possibly be absent in normal rats. In view of the early age at which decommissuration was carried out in the experimental animals, axonal sprouting, resulting in the appearance of fibers which may normally be absent, cannot be excluded.
The red nucleus of the opossum (Didelphis marsupialis virginiana): A light and electron microscopic study
Authors: King James S. , Bowman Michael H. , Martin George F.
Published: December 2004

The opossum midbrain was sectioned in frontal, sagittal and horizontal planes and subsequently stained with cresyl violet to determine the cytoarchitecture of the red nucleus. The neurons were visualized in more detail in Golgi preparations, one micron plastic sections and by employing electron microscopy.

Distinct parvicellular and magnocellular subdivisions are not apparent in this species. The characteristic neurons can be divided into three types by utilizing the following criteria: size, distribution of Nissl bodies and dendritic patterns. The cytoplasm of the giant neurons (45–70 μ) is filled with Nissl granules and the dendrites are long and tapered, and display an occasional spine. The large‐medium neurons (40–25 μ) can be differentiated from the giant neurons on the basis of size and their less extensive pattern of dendritic branching. Small neurons (10–20 μ) are achromatic or have a uniformly basophilic cytoplasm and may be classified as Golgi type II neurons.

The large‐medium size neurons are the most numerous of the three types described and they are distributed throughout the entire extent of the nucleus. The small neurons, although found less frequently than the large‐medium size cells, also are scattered throughout the nucleus. The giant neurons are limited to the caudal medial 0.5 mm of the nucleus.

A morphological classification of synaptic terminals is described: (1) small (1–2 μ), (2) elongate (up to 10 μ), (3) boutons en passage and (4) large (2–4 × 5–9 μ). Differences in the population of synaptic vesicles in the four types of synaptic endings are described. In addition, differences in the distribution of the four types of synaptic terminals with respect to the soma, proximal dendrites and dendrites in the neuropil are illustrated.
Projection of the cochlea to cochlear nuclei in merriam's kangaroo rat
Authors: Webster Douglas B.
Published: December 2004

Projection of the cochlea onto the cochlear nuclei was studied by lesioning the spiral ganglion and tracing degenerating fibers and terminals by the Nauta‐Gygax and Fink‐Heimer methods. Basal turn lesions result in degeneration in the medial portion of anterior ventral cochlear nucleus (AVCN) including globular cell area, small spherical cell area, and a small portion of the large spherical cell area; in dorsomedial portion of posterior ventral cochlear nucleus (PVCN) including globular cell area and octopus cell area; and in the medial extreme of the central region of dorsal cochlear nucleus (DCN). Apical turn lesions result in degeneration in the lateral portion of AVCN including globular cell area, small spherical cell area, and a substantial amount of the large spherical cell area; in the ventrolateral portion of PVCN including globular cell area and multipolar cell area; and in the lateral extreme of the central region of DCN. Lesions in intermediate turns of the cochlea result in degeneration in correspondingly intermediate regions of the cochlear nuclear complex. The basal portion of the cochlea (high frequency) projects most strongly to the small spherical cell area and the octopus cell area. The apical turns (low frequency) project most strongly to the large spherical cell area and the multipolar cell area.
A comparison of somatotopic organization in sensory neocortex of newborn kittens and adult cats
Authors: Rubel Edwin W.
Published: December 2004

To determine the state of functional development in the newborn kitten's somatic sensory system, the organization of mechanoreceptive projections to the sensorimotor cortex was compared to that of the adult Cat. Microelectrode mapping procedures were used.

Projections from all contralateral body surfaces to the primary somatomotor cortex (SmI) are present at birth and respond to mechanical stimulation of the receptors. The somatotopic organization of these projections in the newborn kitten is similar to that in the adult cortex with respect to the cortical region receiving projections from each part of the body and to the detailed arrangement of the projections within each of these cortical subdivisions.

The relative sizes of peripheral receptive fields, and the intensity of stimulation effective for eliciting a response were similar for projections in SmI cortex of both kittens and adults. At both ages receptive field sizes decreased as their locations approached the distal portion of the limbs or rostral part of the face. In adults and newborns, over 75% of the neuronal responses were elicited by gentle bending of the hairs or light touch to the glabrous skin surfaces.

Other similarities between adult and newborn sensorimotor cortexes included: (a) receptive fields of projections to SmI cortex were of fixed, local field type; (b) projections to SmII cortex responded to mechanical stimulation of the receptors; (c) ipsilateral as well as contralateral body surfaces were represented in SmII cortex; (d) the columnar arrangement of neurons and their receptive fields were apparent in the SmI cortex; (e) the coronal sulcus formed a division between the representations of the forepaw and face.

Differences between newborn kittens and adult cats included: (a) shorter latency from electrical stimulation of the skin to a SmI cortical response in adults; (b) projections to SmI cortex having “disjunctive” receptive fields were not found in newborn kittens but existed in the adults; (c) the diversity of receptive field types found in neurons of the adult postcruciate MsI cortex was not found in newborn kittens; (d) newborn subjects displayed less variability in the somatotopic organization of projections and less overlap in the receptive fields of projections to SmI cortex.

It is suggested that the SmI cortex develops as a point‐to‐point reflection of the distribution of mechanosensitive receptors in the body and that the complexities in this organization seen in the adult cortex occur during postnatal development.
A study of retrograde cell degeneration in the lateral mammillary nucleus of the cat, with special reference to the role of axonal branching in the preservation of the cell
Authors: Fry Francis J. , Cowan W. Maxwell
Published: December 2004

The significance of axonal branches in maintaining the integrity of the neuronal soma after axon section has been studied in the lateral mammillary nucleus (LMN) of the cat. Earlier studies with the Golgi and reduced silver methods have shown that the axons of most, if not all, of the cells of this nucleus which enter the principal mammillary tract (PMT) bifurcate with one branch entering the mammillo‐thalamic tract (MThT) and the other the mammillo‐tegmental tract (MTgT). Some of the fibers in the MThT may again bifurcate before ending bilaterally in the anterodorsal nucleus of the thalamus (AD).

Unilateral destruction of the AD results in no detectable retrograde cell degeneration in the LMN. Lesions of the MThT (below the interanteromedial nucleus) cause a slight (∼ 15%) cell loss in the LMN, while isolated lesions of the MTgT have no detectable effect upon the cells of the nucleus. Combined lesions of the MThT and the MTgT cause severe retrograde degeneration in the LMN: approximately 60% of the cells disappear and many of the surviving neurons are frankly atrophic. Lesions of the PMT involving the parent axons of the cells in the LMN result in about the same degree of cell loss as combined lesions of the MThT and MTgT, but the persisting neurons are more severely shrunken and pyknotic.

The implications of these findings for the organization of the connections of the LMN and for the interpretation of retrograde cell degeneration are discussed.
The fine structure of nerve fibers and endings in the lateral cerebral ventricles of the rat
Authors: Westergaard Erik
Published: December 2004

The brains of adult rats were fixed by vascular perfusion with glutaraldehyde. Tissue blocks were cut from the walls in the anterior horn of the lateral ventricles. The blocks were impregnated with uranyl magnesium acetate and embedded in Vestopal. Numerous nerve fibers lay supraependymally, singly or in groups, between the microvilli and cilia of the ependymal cells. Varicosities occurred along the fiber, often in close succession. The intraventricular nerve endings were flask‐shaped. Vesicles were present in the cytoplasm of the nerve processes, varying considerably in shape, size and content. They were round or flattened. Some contained a dense core, whilst others were more or less empty. A zonula adhaerens was sometimes observed between a nerve ending and the luminal plasma membrane of an ependymal cell.

The present study and other studies are compatible with the concept that the intraventricular nerve processes are receptors, possibly registering the composition of the cerebrospinal fluid. A further possibility is that the nerve processes give off a secretion to the cerebrospinal fluid.
Supraoptic nuclei of rodents adapted for mesic and xeric environments: Numbers of cells, multiple nucleoli, and their distributions
Authors: Hatton Glenn Irwin , Johnson John Irwin , Malatesta Carol Zander
Published: December 2004

Quantitative comparisons were made between the supraoptic nuclei (SON) of rodents from mesic and xeric habitats. Laboratory rats, Rattus norvegicus, mesically adapted, were compared with xerically adapted gerbils, Meriones unguiculatus, and kangaroo rats, Dipodomys merriami and Dipodomys spectabilis. As a close genetic control, California deer mice, Peromyscus californicus (mesic), were compared with cactus mice, Peromyscus eremicus (xeric), of the same subgenus. Measures were obtained separately for anterior (Soa) and tuberal (Sot) subdivisions of SON in each species; these measurements included numbers of cells, cell size and, following the discovery of multiple nucleoli in many cells, the proportion of cells showing 1, 2, 3, and 4 or more nucleoli. In mesic species, Sot had fewer cells than Soa; in all but one (D. spectabilis) of the xeric species, the two subdivisions had equal numbers of cells. Cell size was related to body size rather than adaptation. All xeric species showed higher proportions (20 to 60%) of cells with multiple nucleoli than did corresponding mesic species (0 to 20%). Adaptation to environments requiring conservation of body water is correlated with larger numbers of SON cells with multiple nucleoli; relatively larger numbers of cells in Sot but not in Soa; and there are no notable differences in size of cells between mesic‐ and xeric‐adapted species. The suggestion that number of nucleoli is realated to a SON cell's production of antidiuretic hormone is supported by other cytological studies.
The role of climbing fibers in the formation of Purkinje cell dendrites
Authors: Kornguth Steven Edward , Scott Grayson
Published: December 2004

The relationship of the climbing fibers to developing Purkinje cells in the cerebellums of fetal macaques at 75‐, 100‐, 125‐, and 150‐days after conception was studied using Golgi stains and electron microscopic techniques. Between 125 and 150 days of fetal life the somatic processes of the Purkinje cells were most prominent and the apical dendrites were in the initial stages of their development. Serial sections of Purkinje cells, in the cerebellums of 125‐day fetuses, were made and photographed in the electron microscope. Montages of individual Purkinje cells were prepared to permit tracing of the somatic processes and the climbing fibers. It was observed that Purkinje cells developed processes only after becoming associated with climbing fibers and that the climbing fiber terminals capped the growing ends of the processes at this critical stage. In several cases, growing tips of these processes penetrated the terminal boutons. The fine structure of the synaptic junction between the climbing fiber terminal and the Purkinje cell was analyzed using stereo‐electron micrographs (× 125,000). From these observations and those of other authors it was concluded that the climbing fiber induces the formation of somatic processes which then develop into the elaborate dendritic tree. Furthermore, it is proposed that synaptic connections have contractile properties, and that it is this contractility which induces dendrite elaboration.