bluuebunny/crossref_metadata_2025 huggingface dataset:
An electrophysiological study of the visual projection to the superior colliculus of the rat
Authors: Siminoff Robert , Schwassmann Horst Otto , Kruger Lawrence
Published: January 2005

The topographical relations of the visual field with the superior colliculus of the rat was investigated using constant small visual stimuli and recording the electrical response of aggregate unit activity with fine tip metal microelectrodes. A precise essentially linear projection onto the contralateral colliculus was demonstrated after appropriate corrections for brain curvature were performed. The general pattern and arrangement of the retinotopic projection is similar to that found in infra‐mammalian vertebrates. An ipsilateral projection appears to be absent. The phasic properties and rhythmic discharge patterns of single units in the coliculus were studied with stationary and moving luminous stimuli.
Effect of vitamin A on development of the central nervous system
Authors: Langman Jan , Welch Gary W.
Published: January 2005

Pregnant rats and mice were treated with large doses of vitamin A to examine its effect on the closure of the neural groove in the developing embryo. In the rat the most effective dose was 30,000 U.S.P. units given at day 8, 9, and 10 of pregnancy. Twenty‐six per cent of the implanted embryos showed anencephaly and/or myeloschisis. In the mouse the results of vitamin A treatment were inconsistent.

In 12‐day rat embryos, the lateral walls of the diencephalon and mesencephalon were slightly everted. Mitotic neuro‐epithelial cells were frequently piled up two or three rows thick, causing a disruption of the internal limiting membrane. Many cells were characterized by a bleb‐like cytoplasmic evagination protruding into the lumen.

During the following days, the everted walls of the diencephalon and mesencephalon expanded farther and farther over the sides of the head, thereby often covering the lateral hemispheres and the eyes. Although the hemispheres were displaced by the everted diencephalic plates and the eyes were frequently buried deep inside the head, histological differentiation proceeded normally and a primitive cerebral cortex as well as normal eye structures were observed. The accumulation of mitotic figures, the formation of cytoplasmic protrusions, and the presence of small neuro‐epithelial rosettes throughout the brain were the most striking cytological anomalies.

By the eighteenth day of development, small hemorrhages occurred in the mesenchyme surrounding the brain and degeneration became apparent. At birth a small amount of degenerated brain tissue was all that remained from the large exencephalic brain, and the newborn had the appearance of an anencephalic. It is concluded that large doses of vitamin A prevent the neural groove from closing, possibly by interfering with the Cell membrane and/or the mitotic activity of the neuro‐epithelial cells.
Numerical estimates of neurons and glia in lateral geniculate body during retrograde degeneration
Authors: Chow Kao Liang , Dewson James H.
Published: January 2005

Studies were made of decrease of neurons and proliferation of glial cells in the dorsal nuclei of lateral geniculate body of 32 rabbits and 12 cats who had undergone unilateral ablation of visual cortex up to 50 weeks prior to sacrifice. Results show that degeneration occurred in 80% of neurons in rabbit lateral geniculate body within three days, and 95% disappeared within four weeks. In comparison, degeneration was present in only 70% of neurons in the cat nucleus at the seventh post‐operative day, and about 26% remained normal up to the fiftieth week. Glial cell reactions were differential and complex: astrocytes showed rapid proliferation with gradual return to normal, while oligodendrocytes and microglia increased more slowly, maintaining a high level over 50 weeks.
Failure to produce postural tremor by mesencephalic lesions in cats
Authors: Ganes T. , Kaada B. R. , Nyberg‐Hansen R.
Published: January 2005

Attempts were made to produce postural tremor (i.e., tremor at rest) in 24 cats by electrolytic lesions of the ventromedial tegmental area of the mesencephalon. In a number of previous studies in primates destruction of apparently the same region has resulted in postural tremor. The primary target was interruption of nigrofugal fibers or destruction of the pars compacta of the substantia nigra. Such lesions were combined with lesions of the nucleus ruber or the rubrospinal fibers, the reticular substance, the brachium conjunctivum, the medial part of the pes pedunculi, and others. No tremor was produced in cats by such lesions. The different results in primates and cats are possibly explained as due to a species difference.
Nuclear configuration of the diencephalon of Tamandua tetradactyla and Myrmecophaga jubata
Authors: Kaelber William W.
Published: January 2005

The nuclear configuration of the diencephalon of Tamandua tetradactyla (lesser anteater) is figured, described and compared with that of Myrmecophaga jubata (greater anteater) and other mammals, particularly the cat. Their nuclear organization represents, in general, all the elements (or their homologues) found in the mammalian diencephalon.

There is an unusually large nucleus centralis lateralis which penetrates into the nucleus medialis dorsalis from above. The size of the latter group, in the presence of a poorly developed orbitofrontal cortex, suggests that it is primarily dependent upon the marked development of the corpus striatum. The nuclei of the tractus habenulopeduncularis are displaced ventrally, apparently by the medial enlargement of the nucleus centralis lateralis. The nuclei parataeniales bear strong resemblance to those in the armadillo.

There is no nucleus ventralis pars anterior in either Tamandua or Myrmecophaga. The nucleus ventralis medialis is much larger than that in carnivores. The presence of the nucleus submedius and its intimate relation to the nucleus anterior medialis of the anterior nuclear complex, accounts fairly well for questionable homologues in such forms as Tarsius.

The existence of both the large‐celled nucleus of the optic tract and the nucleus limitans indicates the gradual incorporation, at least in part, of the former into the latter. Hypothalamic nuclei, except for the supraoptic and paraventricular groups, are rather poorly differentiated.
The red nucleus and its efferent nervous pathways in the monkey
Authors: Poirier L. J. , Bouvier G.
Published: January 2005

A morphological study of the red nucleus and its efferent nervous pathways based on retrograde cellular degeneration (cell loss) and on degenerated fibers impregnated with osmic acid gave the folowing results. Interruption of the rubro‐tegmentospinal tract was associated with a complete disappearance of the cells in the contralateral magnocellular red nucleus and some cell loss in the adjoining tegmental gray. Interruption of the central tegmental bundle results in a complete cell loss in the parvicellular part of the ipsilateral red nucleus. Such a lesion is associated with degeneration of the rubro‐olivary fibers that terminate along the dorsal lamella of the ipsilateral principal olive. The interruption of the superior cerebellar peduncle does not lead to any cell loss in the red nuclei. The above findings suggest that in the monkey the red nucleus proper discharges exclusively downwards. The small‐celled part gives rise to fibers that travel in the ipsilateral central tegmental bundle and the large‐celled part gives rise to entirely crossed axons that descend in the rubro‐tegmentospinal tract. There apparently exist marked differences in the distribution of the nervous elements within the red nucleus and, correspondingly, in the origin of the efferent nervous pathways in the cat and in the monkey. The interruption of the rubro‐tegmentospinal tract does not lead per se to any noticeable motor impairment but appears to be an essential feature in the appearance of postural tremor and possibly in the production of other extrapyramidal signs in the monkey.
Cytoarchitectonic appearance of the isolated hypothalamus of the cat
Authors: Bleier Ruth , Bard Philip , Woods James W.
Published: January 2005

Neuronal changes in the hypothalamus were studied in 24 cats following extensive forebrain ablations, usually accompanied by mesencephalic transaction. Postoperative survival periods ranged from 13 to 283 days.

In the intact but isolated hypothalamus, severe degeneration was observed in the mamillary nuclei and nucleus of the diagonal band of Broca. Degenerative changes also occurred in portions of the lateral and posterior hypothalamic areas and the area of tuber cinereum. There was a suggestion of cell loss in the suprachiasmatic and infundibular nuclei. Cell loss and atrophy were seen also in subthalamic and entopeduncular nuclei and in globus pallidus. It was possible to correlate degenerative changes in some cells groups with removal of particular regions of the brain.

When entire regions of the hypothalamus itself were also removed, little additional degeneration was seen until the ablation included all but a narrow rim of hypothalamic tissue dorsal and caudal to the optic chiasm.

The lateral hypothalamic area is proposed as the main site of interconnections between medial hypothalamic cell groups and extrahypothalamic structures. The mamillary nuclei alone appear to be dependent upon extrahypothalamic connections. The possible significance of extensive connections between medial hypothalamic cell groups and the neurohypophysis is discussed as well as the possible role of hormones in the maintenance of hypothalamic neuron.
Dimensions of the dendritic spine in the sensorimotor cortex of the rat, cat, squirrel monkey and man
Authors: Jacobson Stanley
Published: January 2005

Measurements of dendritic spines have suggested that there is similarity in the dimensions of the spines in various mammals. The present study was undertaken to determine if there is any variation in the dimension of the dendritic spine in sensorimotor cortex of rat, cat, squirrel monkey and man.

Unfixed slices of rat, cat, squirrel monkey and human sensorimotor cortex were stained with either the Golgi‐rapid or Golgi‐Cox technique. Ultrastructural observations were confined to albino rats that were perfuse‐fixed with buffered 2% osmium. With the electron microscope it was very difficult to find spines. In contradistinction, the Golgi method revealed hundreds of spines; consequently the random sample was made from the Golgi stained material.

In all the examined mammals the mean length of the entire spine was about 2.0 μ (1.5–3.5) with its component parts, the stalk 1.0 μ long (0.5–2.0) and the bulb 1.0 μ in diameter (0.5–2.0). The bulb connects via the stalk with the dendrite. Synapses are only seen on the bulb; they were never found on the stalk. The size of the spine was similar in light and electron microscopy. Comparison of the size of the spines in cortex impregnated with Golgi‐rapid to those impregnated with the Golgi‐Cox technique shows that the size of the spine is the same regardless of the animal or Golgi method used.
Distribution of cholinesterase in the basal rhinencephalic structures of the coypu (Myocastor coypus)
Authors: Girgis M.
Published: January 2005

This paper describes the distribution of cholinesterase in the rhinencephalon of a macrosmatic rodent which had not been investigated previously. A detailed description is given of the arrangement of stained elements in the basal rhinencephalon and this is compared to the cytoarchitectonic arrangement revealed by the classical neurohistological methods. The basic pattern of staining in the coypu is similar to other macrosmatic mammals; points of difference are discussed. The effect of varying the incubation time and other factors are described and discussed fully. It is concluded that cholinesterase–containing fibers are in general better developed in older parts of the brain.
The distribution of 5′‐nucleotidase in the brain of the mouse
Authors: Scott Thomas Gilbert
Published: January 2005

The distribution of the enzyme 5′‐nucleotidase in the brain of the mouse is described in detail. The structures showing the greatest amount of activity are the corpus striatum, the substantia gelatinosa, the lateral longitudinal stria, the nodulus of the cerebellum and parts of the retina. In the cerebellum in particular, and to some extent in the hippocampus, the distribution is such as to suggest that the enzyme may be actively involved not only in simple biochemical processes but possibly also in some neurophysiological function.
Specific subtotal labyrinthectomy of the superior semicircular canals of the kangaroo rat
Authors: Clark David L. , Burns Roebrt D.
Published: January 2005

Unlike most mammals the semicircular canals of the kangaroo rat (Dipodomys) are free of petrous bone in the cavity of the mastoid sinus. This particular anatomical feature enabled the extirpation of individual semicircular canals with little or no damage to other portions of the inner ear or nearby vessels and nerves.

Removal of the two superior semicircular canals resulted in: (a) a deviation of the eyes in an anterioventral direction, (b) an extension of the hindlimbs posteriorly. (c) a bending of the head ventrally, and (d) a falling to the right or left side in an anterior direction. The duration of these symptoms lasted 20 to 22 minutes. A loss of balance and falling while grooming or standing on the hindlimbs was observed to last up to three weeks. There were apparently no chronic symptoms.
The organization of projections from the thalamic mediodorsal nucleus to the prefrontal cortex of the dog
Authors: Narkiewicz Olgierd , Brutkowski Stefan
Published: January 2005

A study of the thalamofrontal connections of the dog was made by placing total or restricted lesions in the prefrontal cortex and examining the resulting retrograde degeneration in the mediodorsal nucleus of the thalamus as demonstrated by Nissl and Klüver‐Barrera techniques. While there is some overlap the general arrangement of the thalamofrontal projection has been established as follows: (1) the intermediate area of the thalamic mediodorsal nucleus, extending obliquely throughout the entire length of the nucleus, projects to the most rostral portion of the prefrontal cortex; (2) the posterolateral portion of the mediodorsal nucleus projects to the proreal gyrus and the caudal part of the orbital gyrus; (3) the antero‐medial portion of the nucleus sends projection fibers to the subproreal gyrus and a greater part of the orbital gyrus; (4) the anterodorsal portion of the nucleus projects to the medial surface of the prefrontal cortex.
Cytoarchitecture of the frontal lobe of the squirrel monkey
Authors: Rosabal Fabio
Published: January 2005

Six Saimiri sciurea brains were studied. Coronal, horizontal, and sagittal sections were stained with cresyl violet. The frontal lobe map shows, anterior to the cental sulcus, a triangular area 4, agranularis giganto‐pyramidalis (FA). Anterior to area 4 is area 6, frontalis agranularis (FB), which differs from area 4 by the absence of Betz cells. Rostral to area 6 is area 8, frontalis intermedia (FC), a narrow, thick band of cortex, with a faint layer IV. Anterior to area 8 the cortex becomes thinner and more granular, its cells are smaller and this region is subdivided into area 9, frontalis granularis (FD), and area 10, fronto‐polaris (FE). Area 44 (FCBm) is on the inferior frontal gyrus, this cortex is granular limb of the arcuate sulcus is thin and granular, contains very large pyramidal cells in layers V and III: area 8a (FDT). The orbital cortex posteriorly shows an evident loss of layer IV; area 11 (FF). Area 50 is a narrow band of koniocortex in the inner wall of the fronto‐parietal operculum. On the gyrus rectus the cortex develops allocortical characteristics with a heavy layer V, area 12 (FG). The characteristics of limbic cortex (mesocortex) are present on the cingulate gyrus, area 24 (LA). Area 25 is found in the subcallosal region.
Excess vitamin A and development of the cerebral cortex
Authors: Langman Jan , Welch Gary W.
Published: January 2005

In previous experiments excess vitamin A, administered to pregnant rats during the early stages of gestation, was found to interfere with the mitotic activity of the neuro‐epithelial cells bordering the neural groove. The result was exencephaly and anencephaly in a high percentage of the newborn. The present work was undertaken to examine the influence of hypervitaminosis A on the behavior of the neuro‐epithelial cells of the cerebral hemisphere and the subsequent migration and differentiation of the neuroblasts during the later stages of development.

Swiss‐Webster mice were treated with large doses of vitamin A on days 14 and 15 of gestation. When subsequently the cell cycle of the neuro‐epithelial cells lining the lateral ventricle of 15‐day fetuses was determined, vitamin A was found to increase both the duration of the mitosis and DNA synthetic period. In comparison with the controls, the total generation time was prolonged by approximately 40%. Since almost all neuroblasts of the cerebral cortex originate in the neuro‐epithelial zone bordering the lateral ventricle, the total number of neuroblast formed is in all probability less than normal. Indeed, prelimiinary data on the number of cells present in the cerebral cortex of 10‐day postnatal rats treated with excess vitamin A toward the end of pregnancy showed a decrease in cell density, indicating either a reduction in the number of cells formed or a degeneration of existing cells.

In a second experiment Swiss‐Webster mice were treated with excess vitamin A during three successive days in the second half of pregnancy. The cerebral cortex of the newborn was examined one to ten days after birth. Histological examination revealed a rather sharply delineated zone of abnormal cells characterized by a lightly stained cytoplasm, a thick nuclear memberane, a desely stained nucleoplasm and several dark chromatin bodies. When the position of the zone containing the abnormal cells was analyzed and correlated with the day of formation in the neuroepithelial zone, it was found that the affected cells were neuroblasts already present in the cortex before the vitamin treatment was started. This indicates that excess vitamin A, given to pregnant mice during the later stages of gestation, influences the development of the cerebral cortex, not only by interfering with the production of cells in the neuroepithelial zone, but also by affecting the differentiation of existing neuroblasts. As a result of these anomalies, some of the newborn appeared to have abnormal patterns of behavior.
The striatum of the opossum, Didelphis virginiana. Description and experimental studies
Authors: Martin G. F. , Hamel Earl G.
Published: January 2005

The relationships and cytoarchitecture of the putamen, the caudate, the claustrum, the globus pallidus and the entopeduncular nuclei have been described for the opossum.

The neocortical projections to these nuclei have ben studied by employing the Nauta‐Gygax technique ('54) and the Swank Davenport modification of the Marchi technique ('34) on animals in which neocortical lesions were previously placed. Degenerating fibers from every cortical lesion were observed to terminate in both the putamen and the caudate with the Nauta‐Gygax technique, whereas such connections were traced only to putamen woth the Marchi method. Terminations were present within the claustrum, but equivocal in the globus pallidus. In general, fibers from the more rostral cortices terminate in the rostral parts of both striatal nuclei, whereas fibers from more caudal neocortical areas project to more caudal parts of these same nuclei. In addition, the more dorsal or dorsomedial neocortical areas distribute more fibers to the caudate than to the putamen, whereas the opposite is true for the ventral or ventrolateral neocortical areas. Neocortical fibers did not project to the ventral, medial part of the head of the caudate which was cytoarchitectually different from the rest of the nucleus. A few fascicles of frontal, orbital and parietal origin terminated in the contralateral putamen and caudate after having decussated in the anterior commissure.
The lateral geniculate nucleus of the marsupial phalanger, Trichosurus vulpecula. An experimental study of cytoarchitecture in relation to the intranuclear optic nerve projection fields
Authors: Hayhow W. R.
Published: January 2005

From a cytoarchitectural viewpoint four laminae are apparent in the normal dorsal lateral geniculate nucleus of the marsupial phalanger. The contra‐ and ipsilateral Nauta preterminal degeneration patterns produced by previous unilateral optic nerve section have been precisely delineated and related to these laminae. The terminations of the optic nerve fibers fractionate the nucleus into six laminae of which the crossed and uncrossed optic fibers each mainly supply three; crossed fibers terminate in laminae 2a, 3 and 6, uncrossed fibers terminate in laminae 1, 2b and 4+5. The “crossed” and “uncrossed” laminae alternate. Concealed lamination is a prominent and hitherto unsuspected characteristic of the organisation of the phalanger lateral geniculate nucleus. The most superficial lamina (1) is unusual in so far as it is mainly “uncrossed”. No other reported mammal except the primitive primate Tupaia shows this feature. Although the two intranuclear optic nerve projection fields are largely segregated, the segregation is only complete in laminae 3 and 4+5. Binocular overlap occurs in the remaining laminae, particularly in lamina 2b. The ventral lateral geniculate nucleus and the pretectal nuclear complex are confirmed as primary optic centers supplied by both crossed and uncrossed optic nerve fibers. Within the superior colliculus cells of the zonal, superficial gray and optic layers are in synaptic relationship with crossed fibers while the ipsilateral optic nerve fibers mainly terminate in a circumscribed region of the optic layer. There is no evidence that any component of the lateral thalamic nuclear complex is a terminal center for nerve fibers of retinal origin.
The development of the human amygdala during early embryonic life,
Authors: Humphrey Tryphena
Published: January 2005

The development of the human amygdaloid complex is described beginning at the time that it first appears, when the cerebral hemispheres begin to evaginate (approximately 8‐‐9 mm), and including a fetus of 27.4 mm CR length Both Nissl and protargol silver series, transversely and sagittally sectioned, were used.

The earliest cell migration representing the striatal complex is from the germinal epithelium in the region of the interventricular foramen, lateral to the primordial hippocampal formation. This is the characteristic topographic location of the amygdala, which, therefore, is the first portion of the human striatal complex to appear embryologically. All of the amygdaloid nuclei identified develop by the migration of neuroblasts from the germinal epithelium.

The three main subdivisions of the amygdaloid complex (anterior amygdaloid area, corticomedial complex and basolateral nuclear group) are identifiable almost immediately after the primordial amygdala appears (9.5 mm in the material studied). In this embryo the cortical and medial nuclei are identifiable, but the central nucleus was not seen until 22.2 mm and the nucleus of the lateral olfactory tract was not identified even in the oldest fetuses.

The basolateral complex differentiates much later than the corticomedial complex and all of the nuclear components became identifiable at the same time (20.7 mm embryo). However the basal nucleus is best represented, the accessory basal next in size, and the lateral only just appearing. In the oldest fetus the subdivisions of the basal and accessory basal nuclei seen in the adult brain are recognizable. Even before the individual nuclei appear, the basolateral complex is much larger than the corticomedial complex. The lateral to medial rotation of the amygdaloid complex has not yet begun in the oldest fetuses, but the posterior end of the lateral ventricle is beginning to turn anteriorly.

During early development, all cells of the amygdala are derived from the lateral striatal ridge, the only one present until 14.0 mm. At 20.7 mm and later neuroblasts are contributed from the medial striatal ridge also. Although the greater part of the basolateral amygdaloid complex is derived from the lateral ridge, some cells are contributed from the medial ridge, particularly to the accessory basal nucleus. By contrast, the corticomedial complex is derived in part from the medial striatal ridge, after it appears, even though the early development is from the lateral ridge.

Comparisons between the amygdala at different developmental stages and the amygdala in fishes, in amphibians, in reptiles and in lower mammals are made. The amygdala in fishes, in amphibians, in reptiles and in lower mammals are made. The topographic relationships between the amygdala and the hippocampal formation, the piriform cortex and the caudate, the putamen and the globus pallidus are considered.
Chromatolysis in the hypoglossal nucleus of the rat: An electron microscopic analysis
Authors: Kirkpatrick Joel B.
Published: January 2005

Chromatolysis was induced by cutting the hypoglossal nerve in young rats and the hypoglossal nucleus was examined by light and electron microscopy. Mitochondria in chromatolytic and control neurons, compared quantitatively, showed no change through the sixth day. A decrease in the mitochondria to cytoplasm ratio was present at the tenth day. The glial cells of the nucleus showed a hyperplastic reaction during early stages. Loosening of contact between neurons and glia as well as complex invagination of neurons by glial processes was observed. Other findings included a prominent juxtanuclear Nissl mass in chromatolyic neurons and degenerating neurites in both ipsi‐ and contralateral nuclei.
Studies on the epithalamus. I. Morphology of post‐mortem degeneration: The habenular nucleus in dog
Authors: Haines Duane E. , Jenkins Thomas W.
Published: January 2005

This study was undertaken to observe the structural changes occurring in myelin, axis cylinders, Nissl substance, nucleus, and general cell architecture at specific post‐mortem time intervals.

The habenulopedunclar tract and the habenular nucleus of 36 adult dogs were sectioned (6 μ to 14 μ) and stained with luxol fast blue‐cresyl echt violet, 2% osmium tetroxide, and a two hour Protargol method. At O hour post‐mortem the cell membrane is relatively distinct, nuclear membrane delicate but distinct, nucleolus clear, Nissl bodies are observed in larger cells of the habenular nuclei.

From 6–24 hours three main areas of change are noted: an agglutination, fragmentation, and obliteration of the Nissl substance; a progressive increase in the irregularity of the nuclear and cell membrane; a progressive increase in vaculation and in the perinuclear halo. From 24–36 hours the cytoplasm appears extremely granular with the granulation extending into the nucleus. Some cells appear swollen with indistinct nuclei or appear anucleated. From 36–48 hours the cytoplasm shows increased granulation and at 48 hours few cells show nuclei. Most cells show uniform color in the cytoplasm and nuclear area. Any remaining nuclei in the 36–48 hour interval appear pyknotic and finely granular. The myelin sheaths and axis cylinders show only limited structural change over the time span of this study.
Central projections of brachial and lumbar dorsal roots in reptiles
Authors: Joseph Barry S. , Whitlock David G.
Published: January 2005

The central distributions of single lumbar and brachial dorsal roots have been determined in the reptiles: Caiman sclerops, Ctenosaura hemophila and Iguana iguana. Degeneration resulting from root transections was assessed by means of the uranyl nitrate modification of the Nauta method. All dorsal root projections were entirely ipsilateral to the side of the damaged roots. A projection to the ventral horn was found in the lizards, but not in Caiman. A nuclear column, apparently homologous with Clarke's column of mammals, was observed in Ctenosaura and Caiman. A somatotopically organized dorsal column projection to gracile and cuneate nuclei was found in Ctenosaura and Caiman. No evidence was obtained for a projection to a lateral cuneate nucleus or to areas rostral to the level of the dorsal column nuclei. The findings are contrasted with previous descriptions of dorsal root projections in reptiles, as well as with the pattern of dorsal root distribution reported for amphibians and for mammals.
The development of synaptic contacts in the cerebellum of Macaca mulatta
Authors: Kornguth Steven E. , Anderson John W. , Scott Grayson
Published: January 2005

The maturation of various cerebellar cortical cells, the appearance of afferent fibers to the cerebellum, and the development of synaptic contacts in the cerebellar cortex and deep nuclei was investigated in the fetal macaque. Ultrastructural studies were done on cerebellum obtained from fetuses at 75, 100, 125 and 150 days after conception to interrelate the temporal development of these three systems. At 75 days, synaptic contacts were seen on somas and axons of neurons in the deep cerebellar nuclei, and climbing fibers formed pericellular baskets around Purkinje cells. By 100 days the climbing fibers synapsed with somatic spines of the Purkinje cells, and mossy fiber endings were present in the internal granule cell layer. Synaptic contacts were also seen on dendritic processes of neurons in the deep cerebellar nuclei at this time. In the 125 day cerebellum, Golgi cells were identified for the first time and climbing fibers and parallel fibers made synaptic contact with both Purkinje and Golgi cells. At 150 days parallel fibers made synaptic contact with superficial stellate cells and mature cerebellar glomeruli had appeared. At this stage, axosomatic contacts of climbing fibers on the soma of Purkinje cells had disappeared. The relationship of these anatomical observations to possible functional activity is discussed.
An electron microscopic study of neurons during postnatal development of the rat cerebral cortex
Authors: Caley David W. , Maxwell David S.
Published: January 2005

The differentiation and maturation of the neurons of rat cerebral cortex during the first three weeks of postnatal life has been studied with the light and electron microscopes. At birth, the supeficial cortex is largely made up of undifferentiated cells, tightly packed together in vertical columns between which the developing process and blood vessels, and relatively extensive extracellular spaces are found. During the first two weeks, these cells diferentiate into either neuroblasts and neurons, or into spongioblasts and neuroglia. In the case of neurons but not neuroglia, this maturation occurs in a gradient from the depths toward the surface. The round undifferendtiated cells are characterized by an absence of processes, a thin rim of perinuclear cytoplasm containing few organelles, and a peripheral clumping of condensed nuclear chromatin. The differentiating neuroblasts display increasing numbers of cytoplasmic organelles, especially endoplasmic reticulum, evenly dispersed nuclear chromatin, and presumptive apical dendrites. The rough endoplasmic reticulum of neuroblasts become swollen during the transition into neurons during the second week. The endoplasmic reticulum forms subsurface cisterns that transiently evaginate the cell membrane, forming conspicuous diverticuli in the neuropil at the same time that the cells display an increase of cytoplasmic matrix density and increasing numbers of ribosomes. During the three weeks following birth, organelles increase in number and complexity, synapses develop, the extracellular spaces disappear, and the maturing neurons become separated from one another by the growth of neuropil and nonnervous elements. At the end of this three week period the cortical tissue and its neurons are apparently mature and the adult pattern of cortical fine structure is established.
Ventrolateral spinal cord afferents to the brain stem in the domestic pig
Authors: Breazile James E. , Kitchell Ralph L.
Published: January 2005

The distribution and termination within the brain stem of nerve fiber systems which comprise the ventrolateral funiculus of the spinal cord were studied in the domestic pig. Guillery et al. ('61) modification of the Nauta‐Gygax technique for silver impregnation of degenerating nerve fibers was utilized in this study. It is concluded that a spinothalamic tract does exist in the domestic pig, but that it is secondary in prominence to a large spinoreticular fiber system. The distribution and terminations of fibers within the brain stem of the pig resemble the pattern described by Anderson and Berry ('59) for the cat.
An electrophysiological study of the cerebellar projections to the nucleus ventralis lateralis of thalamus in the cat. I. Nuclei fastigii et interpositus
Authors: Angaut Pierre , Guilbaud Gisègle , Reymond Marie‐Claude
Published: January 2005

Stimulation of nucleus fastigii and interpositus of the cerebellum of the cat under chloralose anaesthesia evokes non‐relayed responses in the thalamic region including and surrounding n. ventralis lateralis (VL).

Monosynaptic responses to stimulation of nucleus interpositus are only contralateral whereas those of n. fastigii are bilateral.

Responses to fastigial stimulation appear in an area restricted to VL and n. ventralis medialis, contralateral projections being much more extensive than homolateral.

Projections of n. interpositus extend widely upon VL and n. ventralis anterior encroaching on a small rostral area of nucleus ventralis posterolateralis; some fiber responses are also recorded up to a capsular zone close to globus pallidus.

The results of the current study are discussed with regard to the data from anatomical and physiological literature.
Septohabenular connections in the rat, cat and monkey
Authors: Powell Ervin W.
Published: January 2005

Septohabenular projections were studied using the Nauta‐gygax method of staining degenerating axons. The results are in general agreement with those reported by others. However, the septum projects differentially to the habenula and the patterns differ slightly in the three species studied. Rostral parts of the septum projected to the lateral habenular nucleus and posterior parts to the medial nucleus. Dorsal and ventral structures of the septum had a slight dorsal ventral topography of projection in the stria medullaris thalami. Projection through the stria medullaris was confined to its medial part only in the rat. The largest number of fibers to bypass the habenula and terminate in the mesencephalic central gray occurred in the monkey.
The sympathetic trunks of a hibernator, the bat Myotis lucifugus
Authors: Webber Richard H. , Kallen Frank C.
Published: January 2005

The sympathetic trunks in Myotis lucifugus are each characterized by three unusually prominent ganglia: the superior cervical, the stellate and a “large lumbar” ganglion. The superior cervical appears to distribute only to the head region. The cervical sympathetic trunk connects with the vagus nerve but not to the cervical spinal nerves. The stellate is the largest of the trunk ganglia. A prominent nerve arising from it follows the vertebral artery. This vertebral nerve connects with the second to the seventh, and sometimes the eighth, cervical spinal nerves. Another prominent branch from this ganglion follows the cervical artery to ramify in the interscapular brown fat pad. The stellate ganglion supplies the brachial plexus directly and via the vertebral nerve. Its branches also supply thoracic viscera important for arousal from hibernation as well as for flight. The large lumbar ganglion contributes very few fibers to abdominal or pelvic viscera but, via the lumbosacral plexus, may affect vasoconstriction in the pelvic wall and posterior extremities. The prominent prevertebral ganglia in the abdomen and pelvis, which include an adrenal‐;renal complex, are probably supplied by the tenth thoracic to second lumbar spinal nerves.
The postnatal development of the canine cerebellar cortex
Authors: Phemister Robert D. , Young Stuart
Published: January 2005

The cerebellum of the neonatal puppy was found to be incompletely differentiated. Its gross dimensions were less than half those of the normal adult, and although major lobules were recognizable, folial development was rudimentary. Microscopically, the cortex on the second postnatal day was distinguished by a thick subpial external granular layer of actively dividing cells. Beneath this transient layer, permanent cortical layers were largely undeveloped and myelination was not yet evident. During the first two postnatal weeks, the width of the external granular layer remained relatively constant (at slightly more than 50 μ), while other cortical layers underwent considerable growth, with histologic and cytologic differentiation. After the second postnatal week, the width of the external granular layer declined steadily, so that by the tenth week only a vestige of the layer remained. Between the second and seventy‐second postnatal days, a tenfold increase occurred in the width of the molecular layer. Major growth and differentiation also occurred in the internal granular layer, which became almost tripled in its width during the first ten postnatal weeks. Myelination proceeded in a centrifugal direction and occurred earlier in the vermis than in the hemispheres. By the end of the first month, myelination of the vermis was practically complete, and by the tenth week, the arbor vitae of the hemispheres appeared fully myelinated.
The cytoarchitecture of the human anteroventral cochlear nucleus
Authors: Bacsik Robert D. , Strominger Norman L.
Published: January 2005

The cytoarchitecture of the anteroventral cochlear nucleus (Av) was studied in six human brain stems stained with cresyl violet. A compensating polar planimeter was used to measure the cross‐sectional area of perikarya drawn with a camera lucida device. The majority of neurons are ovoid in shape with somewhat eccentric nuclei and moderately coarse Nissl granules which are uniformly distributed throughout the neuroplasm. On a dimensional basis, there is a single population of cells which vary in size according to a normal distribution. The average perikaryal size is 370 sq. μ (18 × 26 μ). Cellular density is greatest along the lateral margin of Av near the rostral end. Neurons of all sizes intermingle in every part of the nucleus and no circumscribed area can be characterized as containing exclusively or even predominantly neurons of any given size. The cytoarchitecture of the human anteroventral cochlear nucleus so closely resembles that of the rhesus monkey as to suggest similar fiber projections and physiological properties in both species.
Distribution of cerebellar and somatic lemniscal projections in the ventral nuclear complex of the Virginia opossum
Authors: Walsh T. Myrick , Ebner Ford F.
Published: January 2005

The distributions of cerebellar and somatic lemniscal projections to the ventral nucleus of the thalamus were compared in the opossum to determine the extent of overlap in the terminal field of these two fiber systems. Following lesions of these structures, the degenerated fibers were traced to the thalamus using the Fink‐Heimer technique. The results indicate that the cerebellum projects only to the rostral portion of the ventral nucleus, while the gracile and cuneate nuclei project to the caudal portion of the ventral nucleus. We conclude from comparing these two afferent fiber systems that there is no detectable overlap in the cerebellar and lemniscal projections to the ventral thalamic nucleus of the opossum. These results support the hypothesis that the single somatic sensory‐motor area of the opossum's cortex receive afferent fibers from at least two separate subdivisions of the ventral nucleus. Outside the border of the ventral nucleus, cerebellar and lemniscal projection fields do overlap, especially in a cell group just dorsal to the ventral posterior nucleus. This is a distinctly different type of organization of these afferent fiber systems. This cell group has recently been shown likewise to project to the parietal somatic sensory‐motor cortex. Since the mode of intracortical termination of this projection differs markedly from that of the VP and VAL projections, the somatic sensory‐motor cortex of the opossum can be said to receive fundamentally different projections from two thalamic regions both of which are recipients of both cerebellar and somatic‐lemniscal information.
Retinal structure in the smooth dogfish, Mustelus canis: Light microscopy of bipolar cells
Authors: Witkovsky Paul , Stell William K.
Published: January 2005

Retinal bipolar cells of the smooth dogfish (Mustelus canis) were examined in the light microscope after vital staining with methylene blue or in Golgi‐impregnated preparations. Bipolars of Mustelus retina, as of other vertebrate retinas, were divisible into two broad categories: those with fine axons and those with bulbous axonal terminals. Further classification was made on the basis of the level of axonal termination within the inner synaptic layer (ISL). The wide, monostratified axons of some bipolar cells (type a1) ramify in the distal (outer) third of the ISL to a total horizontal span of 400–600 μm. These cells possess elliptical dendritic arbors 80–100 X 150–200 μm in diameter, variously shaped perikarya, and a cylindrical or bulbous Landolt's club. In flatmounted preparations, these cells often are seen to have all dendrites exiting horizontally from one side of the perikaryon, the axon exiting horizontally from the other side. The narrow, multistratified axons of a second class of bipolars (type a2) ramify within the distal half of the ISL to a horizontal span of 45–130 μm. Their dendritic arbors are round or elliptical and of a diameter similar to that of axonal spread. A filamentous or flask‐shaped Landolt's club is generally present. The axons of bipolars with bulbous axonal terminals (type b) end in the middle of the ISL. The perikaryon is tulip‐shaped and a circular dendritic arbor, 70–100 μm in diameter, spreads concentrically about it. These cells always lack a Landolt's club. In the proximal (inner) half of the ISL, both wide monostratified (type c1) and narrow multistratified (type c2) bipolar cell axons are encountered. The axons of cells which have monostratified endings in the proximal ISL (type c1) branch more frequently and have lesser horizontal extents than the axons of their counterparts (type a1) in the distal ISL. All bipolars ending in the proximal ISL lack a Landolt's club. The thick ISL of Mustelus retina is divided into at least three vertical sub‐layers, within each of which terminate axons of one or two classes of bipolar cells and dendrites of a single class of giant ganglion cells. If giant ganglion cells receive direct synaptic input from bipolar cells, the vertical strata of the ISL contain structurally distinct, and perhaps functionally different, bipolar‐ganglion cell pathways.
Projections of cervicothoracic dorsal roots to the cuneate nucleus of the rat, with observations on cellular “bricks”
Authors: Basbaum Allan I. , Hand Peter J.
Published: January 2005

The distribution of cervicothoracic (C1–T2) dorsal roots to the cuneate and accessory cuneate nuclei was studied in the rat with the Fink‐ Heimer I technique following single extradural rhizotomies. Cytoarchitectural analysis of the cuneate nucleus revealed an anatomically distinct caudal and rostral region. The caudal region was characterized by discrete aggregates of cells arranged as “slabs” or “bricks” which continue vertically almost to the ventral limit of the cuneate nucleus. In contrast, the cells of the rostral region were organized in a non‐focal manner.

The projection of the cervicothoracic dorsal roots to the cuneate nucleus reflected the cytoarchitectural pattern observed; non‐focal terminal fields of degeneration in the rostral region and discrete “terminal field bands” of degeneration isolated from one another by degeneration‐free zones in the caudal region. However, the projections of dorsal roots C5 and T2 to the caudal region is non‐focal.

In both regions of the cuneate nucleus, the distribution of dorsal root degeneration was topographically organized with cranial roots terminating ventrolaterally and more caudal roots, dorsomedially. The amount of intersegmental overlap of dorsal root terminal fields was greater in the rostral than in the caudal region.

Individual dorsal roots projected differentially to the two regions of the cuneate nucleus. Roots C3 and C4 distributed primarily to the rostral region whereas C5 to T1 distributed to both regions. T2 root projected primarily to the caudal region. Dorsal roots C1 and C2 did not terminate in either region of the cuneate nucleus.

All roots studied projected heavily and topographically to the accessory cuneate nucleus. Extensive overlap of the very dense terminal fields characterized the dorsal root projections to the accessory cuneate nucleus.

On the basis of cytoarchitectonics and dorsal root projections, a dual organization of the cuneate nucleus was revealed. This organization reflected previous anatomical and electrophysiological studies in the rat and paralleled the organization described in the dorsal column nuclei of the cat. The significance of the dual organization with respect to dorsal column function was discussed, as was the finding of the lack of C1 and C2 dorsal root projections to the cuneate nucleus.
Investigation of glial cells in semithin sections. II. Variation with age in the numbers of the various glial cell types in rat cortex and corpus callosum
Authors: Ling Eng‐Ang , Leblond C. P.
Published: January 2005

Semithin Epon sections stained with toluidine blue were used to enumerate astrocytes, microglia, the three subtypes of oligodendrocytes, and cells referred to as free subependymal cells, in the corpus callosum and cerebral cortex of male Sherman rats of various ages. The period covered extended from a few days before weaning (3/4 month of age) until the time when growth became negligible (5 months of age).

The total number of glial cells increases with age in both cortex and corpus callosum. However, the investigation of individual cell types reveals that the number of microglia remains fairly constant throughout the period under study. The number of astrocytes in corpus callosum increases up to the age of one month, but remains constant thereafter, while their number in the cortex is the same at all investigated times. In the case of oligodendrocytes, the three subtypes behave differently. About two‐thirds of the oligodendrocytes in rats aged three‐quarters of a month are of the light or medium shade types, but the number of these gradually decreases with age and becomes very low in five‐month‐old rats. In contrast, the dark cells which constitute about one‐third of the oligodendrocytes in young rats make up nearly the whole of this group in adults. Finally, free subependymal cells are absent in cortex throughout the period under study, but are present in corpus callosum, where their number steadily declines with age.

In conclusion, the numbers of astrocytes and microglia seem to remain constant in growing rats after the age of one month. Dark oligodendrocytes markedly increase in number with age, while the other types of oligodendrocytes and the free subependymal cells are reduced to negligible numbers by the age of five months.
Vestibular cortical projection in the rabbit
Authors: Ödkvist L. M. , Rubin A. M. , Schwarz D. W. F. , Fredrickson J. M.
Published: January 2005

The neocortical surface of the rabbit's brain was explored by macroelectrodes with isolated electrical stimulation of the vestibular nerve. Surface positive evoked potentials were recorded within the first somatosensory (SI) forelimb field. Negative field potentials in middle cortical layers were only found in a small area within the rostral part of this field. The rabbit's vestibular field is compared with those of rodents, carnivores and primates.