bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of neuronal differentiation in developing cultures of neonatal mouse cerebellum: A living and silver impregnation study
Authors: Allerand C. Dominique
Published: December 2004

Organotypic explants of neonatal mouse cerebellum were cultured for periods up to 56 days in vitro. Living cultures were compared to those fixed and stained by the Holmes' reduced silver nitrate method. The explants consist of a heterologous neuronal population comparable to that found in situ. Since the differentiation of the cerebellum is actively in progress during the neonatal and postnatal periods, cultures derived from such tissue demonstrate the developmental phases that are present at the time of explantation.

The in vitro. maintenance of neonatal mouse cerebellum allows the expression of those aspects of neuronal development which are intrinsic to the cell proper and primarily concerned with type‐specific differentiation, e.g., neurofibrillary development; axonal growth; myelination; and the acquiring of basic dendritic patterns. The secondary aspects of differentiation, which determine the adult state and which are characterized primarily by the increasing complexity of dendritic formation and of synaptic interactions, occur to a much lesser extent in vitro.

The importance of recognizing transitional forms as normal and not peculiar to the in vitro situation is emphasized.
Hippocampal efferents to the ipsilateral entorhinal area: An experimental study in the rat
Authors: Hjorth‐Simonsen A.
Published: December 2004

A hitherto undescribed pathway from the hippocampus to the entorhinal area has been found in the albino rat in experimental studies by the silver‐impregnation technique of Fink and Heimer ('67) and a modification there of by the present author ('70). Animals in which the hippocampal formation had been deprived of commissural and other afferents by a preliminary operation at the age of eight days were used to faciliate the search for the site of origin of the pathway. Lesions in various parts of the hippocampus showed the origin to be restricted to subfield CA3 in approximately the temporal third of the hippocampus. The axons run caudally in the stratum radiatum and stratum lacunosummoleculare, and terminate in the medial part of the entorhinal area in a distinct zone corresponding to layer IV of Lorente de Nó ('33, '34). By the aid of alternating series of sections impregnated with silver and incubated for acetyl‐cholinesterase, the zone of termination was shown to be identical with the acetyl‐cholinesterase positive band at the level of layer IV. In the dorso‐ventral sense the fibers exhibit a topical organization, terminal degeneration at different levels of the entorhinal area depending on the levels of CA3 damaged. The mean course of the fibers from each level of CA3 seems to be roughly horizontal. A hippocampoentorhinal neuron circuit is proposed.
The telencephalon and hypothalamus of the bluegill (Lepomis macrochirus): Evoked feeding, aggressive and reproductive behavior with representative frontal sections
Authors: Demski Leo S. , Knigge Karl M.
Published: December 2004

Bluegills were stimulated electrically while swimming free in an aquarium containing other bluegills, a mirro, gravel and food. Stimulation sites have been plotted on representative frontal sections for which a nomenclature system was developed. Nestbuilding was evoked in both sexes by stimulation near the area dorsalis telencephali pars centralis, while strong after‐responses were elicited from the ventral preoptic region. Stimulation in the preoptic region slightly rostral to the habenula simultaneusly inhibited aggressive behavior and evoked courtship. Feeding (snaping up prey, gravel or debris) and aggressive behavior (chasing and biting another bluegill) resulted from stimulation in the region surrounding the lateral recess of the third ventricle of the inferior lobe of the hypothalamus. In several cases feeding and aggressive responses alternated during stimulation; a similar pattern was observed as an after‐response to stimulation in the nucleus rotundus. These results are discussed with regrard to stimulation in the nucleus rotundus. These results are discussed with regard to possible anatomical systems controlling reproductive, feeding and aggressive behavior in fishes.
An electron microscopic study of synaptic morphology in the oculomotor nuclei of three inframammalian species
Authors: Waxman Stephen G. , Pappas George D.
Published: December 2004

The fine structure and distribution of synapses in the oculomotor nuclei of three inframammalian species (spiny boxfish Chilomycterus schoepfi, grass frog Rana pipiens, American chameleon Anolis carolilzensis) were studied by electron microscopy. Oculomotor neurons in Chilomycterus are approximately 40 μ in diameter, and have one or a few large dendrites which extend in a ventro‐ lateral direction and ramify in the tegmental neuropil. Axons establish numerous en passant synapses and sometimes extend into indentations in the surfaces of the motoneurons. Approximately one‐sixth of synaptic profiles include regions of close membrane apposition (gap junctions). Presynaptic processes at these synapses contain electron‐lucent and dense core vesicles. Similar synapses occur on fine dendrites in the neuropil but are rare. Somatosomatic and dendroden‐ dritic close appositions are not present, so that electrotonic coupling between oculomotor neurons occurs via a presynaptic pathway. Synapses commonly arise at nodes of Ranvier. Rana oculomotor nucleus consists of motoneurons about 30 p in diameter with one or a few dendrites which ramify in the ventrolateral neuro‐ pil, and smaller and less common multipolar interneurons. The two neuronal types differ in their relationships with glial elements. The majority of synapses on large neurons exhibit distinct synaptic clefts. Close membrane appositions are present at approximately 8% of synaptic contacts on large neurons, but are rare on small diameter dendrites. Subsynaptic cisterns are present at some synapses, but were never observed subjacent to close appositions. Axosomatic synapses are uncommon on the smaller interneurons. A cryptlike extension of the cerebral aqueduct separates contralateral oculomotor nuclei in Anolis. Oculomotor neu‐ rons in dorsolateral and ventromedial divisjons of the nucleus are multipolar and approximately 25 p in diameter. Large areas of the cell bodies are covered by glial lamellae, and axodendritic synapses predominate. At 5% of synapses on somata and proximal dendrites, there are close appositions. Subjunctional dense bodies are present at other synapses. Previous electrophysiological studies have demonstrated electrotonic coupling between homonymous oculomotor neurons, and between neurons and presynaptic fibers in teleosts. The present results pro‐ vide morphological evidence for electrotonic transmission in the oculomotor nuclei of three diverse species of vertebrates.
Fiber systems of medial and anterior thalamus of macaque
Authors: Wright Sanford J. , Locke Simeon
Published: December 2004

Lesions were produced in the anterior limb of the internal capsule of three Macaca mulatta. The resulting median, paramedian, and lateral vertical bands of thalamic degeneration appeared to disregard nuclear boundaries and extend from the anterior tubercle to the habenula. A mediolateral gradient in the dorsomedial nucleus was related to a basal, middle and lateral disposition of lesions in the capsular fan. The possible significance of these observations as underscoring a more general theme of thalamocortical relationship was explored.
The role of the arcuate nucleus in the brain‐pituitary‐gonad axis
Authors: Brawer James R.
Published: December 2004

Recent evidence indicates that the arcuate nucleus of the hypothalamus is involved in the control of gonadotrophin secretion. In the present work the neurons of the arcuate nucleus were studied in normal and castrated adult male rats with the electron microscope.

The neurons of normal animals appear quite ordinary in many respects and contain the same types of organelles that are common to neurons in general. In addition, however, many neurons contain structures resembling the chromatoid bodies commonly found in developing spermatids. There are also some peculiar features of nuclear structure such as nucleolar association with the nuclear envelope and the fragmentation of the nucleolus.

Arcuate neurons of castrated animals show two variations, the most obvious of which is the occurrence of whoreled formations of closely apposed concentric cisternae of the smooth endoplasmic reticulum. These whorled bodies appear in several different forms. The simplest consist of complete uninterrupted cisternal rings. Variations from the simple form involve anastomoses between adjacent cisternal shells, areas in which the regular layered structure is obliterated by confluence of cisternal rings, areas of irregular spacing in which varying amounts of cytoplasm are trapped between adjacent rings, and the presence of semicircular incomplete outer rings. As many as five whorled bodies have been observed in a single cell. The whorled bodies in such a group are continuous with one another and with the common endoplasmic reticulum.

Whorled bodies appear four days after castration, and by two weeks about one tenth of the neurons exhibit them. Very few whorled bodies appear in castrated animals that received daily injections of 2 μg testosterone propionate per gram body weight. Castration produced no obvious qualitative changes in the ependymal cells or their processes.

The second variation resulting from castration is the presence of large populations of dense core vesicles in some of the neurons of the arcuate nucleus. Dense core vesicles are sparse in the neurons of normal animals. The significance of these variations is discussed.

There is evidence to suggest that the whorled bodies may be an indication of enhanced synthetic activity following release from gonadal steroid inhibition. In any case, the whorled bodies label the cells in which they occur as direct links in the brain‐pituitary‐gonad axis.
Corticobulbar projections of the marsupial phalanger (Trichosurus vulpecula). II. Projections to the mesencephalon
Authors: Martin George F. , Megirian David
Published: December 2004

The pattern of neocortical projections to the mesencephalon was studied in the marsupial phalanger (Trichosurus vulpecula). Lesions were placed in selected neocortical areas in 29 adult phalangers. After a one to two week survival time, the animals were perfused, the brains and spinal cords removed and processed by either the Nauta‐Gygax technique or the method of Fink and Heimer. The cytoarchictecture of the neocortex was studied also and those results pertaining to the ablated cortical areas are reported. The cortex just rostral to the orbital sulcus (motor area for the head and neck) contains numerous dark staining pyramidal neurons which measure up to 35μ at their widest dimension. Lesions within this region produce fiber degeneration within the ventral tegmental area, the nucleus linearis, the periaqueductal gray, the deeper layers of the superior colliculus and the lateral tegmental area. The frontal pole cortex contains very few large pyramidal neurons. Ablations of this cortex result in a similar pattern of fiber degeneration, although few, if any, degenerating fibers are present within either the superior colliculus or the lateral tegmentum.

Cytoarchitecturally the cortex just caudal to the orbital sulcus (forelimb motor and some sensory cortex) is strikingly similar to the immediate preobital region. However, destruction of this region produces fiber degeneration within the nucleus of Darkschewitsch, the nucleus of the medial longitudinal fasciculus, the periaqueductal gray, the lateral and deep tegmental areas, the caudal pretectal nucleus and the red nucleus. The motor‐sensory hindlimb area also contains numerous large pyramidal neurons, but the internal granular layer is somewhat better developed than it is in the bulk of the forelimb region. Lesions within the motor‐sensory area for the hindlimb produce fiber degeneration within the same general regions as do ablations of the forelimb cortex, although more degenerating fibers are present within the red nucleus and fewer within the caudal pretectal nucleus.

The somatic sensory face cortex (ventral and lateral to the motor‐sensory limb areas) is characterized by a particularly well developed internal granular layer. Lesions of this area produce axonal degeneration in both superficial and deep layers of the superior colliculus. The striate and peristriate areas can be distinguished from one another by the development of the internal granular layer. Lesions in these areas result in fiber degeneration which is limited to the superficial layers of the superior colliculus.

The neocortex of the phalanger temporal pole cannot be distinguished by the development of any particular layer. Indirect evidence suggests that this cortical region projects to the nucleus of the inferior colliculus as well as to the deeper layers of the superior colliculus.
Topological analysis of the brain stem of the lamprey Lampetra fluviatilis
Authors: Nieuwenhuys Rudolf
Published: December 2004

The investigations of His, Herrick, Johnston and many others have led to the doctrine that the central nervous system fundamentally consists of a number of longitudinally arranged zones or columns, some of which are delimited from each other by distinct ventricular sulci. In order to facilitate the study of this basic morphological pattern in the brain stem, a procedure has been developed, making it possible to survey in one figure the neuronal structures and their relationship to the ventricular grooves in this region. Essentially this procedure involves two steps: first the cell masses and large individual cells are projected upon the ventricular surface, and next the ventricular surface is flattened out, i.e., subjected to a one‐to‐one continuous topological transformation. Such a topological analysis was carried out on the brain stem of the lamprey, Lampetra fluviatilis, and yielded the following results: The sulcus limitans of His extends throughout the rhombencephalon, but does not enter the midbrain. The rhombencephalic basal plate can be clearly divided into a medial somato‐motor, and a lateral viscero‐motor zone. The somato‐motor zone consists of a rostral extension of the spinal motor column and three reticular nuclei. Rostrally this zone is continuous with the tegmentum mesencephali, which contains another reticular nucleus and the superficial and deep nuclei of III. The reticular nuclei contain groups of large cells. On either side seven of these large cells, three in the midbrain, one in the isthmus and three in the hindbrain, are significantly larger than the others, and are designated as Müller cells. The viscero‐motor zone is confined to the hindbrain. It consists of a continuous chain of discrete cell masses: the motor nuclei of V, VII, IX and X. This zone contains in addition the large Mauthner neuron, which is situated between the nuclei of V and VII.

In the rhombencephalic alar plate, separate viscero‐sensory and somatosensory zones could not be recognized. The delimitable nuclei in this region all belong to the somato‐sensory octavo‐lateralis complex. The latter complex extends rostrally into the very small cerebellum which, apart from a zone of periventricular gray and a nucleus cerebelli, harbours the motor nucleus of IV. The sensory centers of the midbrain, i.e., the torus emicircularis and the tectum are caudally continuous with the gray substance of the alar plate of the hindbrain. Large, presumably primary sensory, elements occur in the caudal and ventral part of the rhombencephalic alar plate. Such “dorsal cells” are also present in the spinal cord, but a midbrain equivalent, i.e., nucleus mesencephalicus of V, is entirely lacking.
Primary optic pathways in the duckbill platypus, Ornithorynchus anatinus: An experimental degeneration study
Authors: Campbell C. B. G. , Hayhow W. R.
Published: December 2004

The retinal efferent axons of Ornithorhynchus anatinus project, as in the echidna, to two diencephalic nuclei disparate in size and location and designated provisionally as LGNa and LGNb, and to the pretectum and superior colliculus. The primary optic pathways of the platypus are crossed except for a small number of fibers which project to the ipsilateral LGNa and b. The optic input to the superior colliculus enters via a sheet of retinal fibers which runs over the surface of the colliculus and distributes terminal endings to the stratum griseum superficiale. A similar situation exists in the echidna, birds and reptiles, but is not known to be present in therian mammals. No interstitial nuclei were found in the optic tract as are present in the echidna. In addition, no nucleus which could possibly be identified as a dorsal terminal nucleus of the accessory optic system was found in the platypus. Such a nucleus is present in the echidna. Projection of optic axons to a medial terminal nucleus of the accessory optic system is present, although discrete inferior and superior accessory optic fasciculi are not. The primary optic pathways of the platypus appear to be less complex than those of the echidna, possibly due to a more limited use of vision.
The structure of the ventral part of the lateral geniculate nucleus. A cyto‐ and myeloarchitectonic study in the cat
Authors: Jordan Hans , Holländer Horstmar
Published: December 2004

The cyto‐ and myeloarchitectonic organization of the ventral nucleus of the lateral geniculate body (LGV) were investigated by means of several histological series sectioned in different planes. Twenty‐one hemispheres of normal adult cats were used. The shape of the nucleus and its anatomical relationships with the optic tract, the dorsal nucleus of the lateral geniculate body (LGD) and the zona incerta were established. The LGV is club‐shaped with a broad main part and a slender stalk, which is twisted around the rostrolateral aspect of the optic tract. Caudolaterally the LGV is covered by the optic tract and dorsomedially it is apposed to the LGD. Rostromedially it merges with the thalamic reticular nucleus and ventromedially its stalk is continuous with the transition zone between the reticular nucleus and the zona incerta. Cell sizes were also measured. Five subdivisions of the nucleus were identified and their spatial interrelationships were determined: LGVa, LGVd and LGVe being composed of small cells exclusively, LGVb and LGVc containing both small‐ and medium‐sized nerve cells. LGVa and LGVb are situated at the rostral part of the nucleus both fusing rostrally with the reticular nucleus of thalamus. LGVd occupies the caudal end of the nucleus. LGVe is situated along the contact zone with the optic tract and is combined with LGVc. LGVb is located between LGVa, LGVc and LGVd.
Ultrastructure of the pulvinar of the squirrel monkey
Authors: Mathers Lawrence H.
Published: December 2004

Three divisions of the squirrel monkey pulvinar, p. inferior (PI), p. lateralis (PL), and p. medialis (PM), have been studied with light‐ and electron‐microscopic techniques. Two populations of neurons exist. The first neuron is a thalamocortical relay cell (TCR), averaging about 26 μ in diameter, with radial dendritic pattern and thin dendritic appendages. The second is a Golgi type II neuron, about 16 μ average diameter, with more complex dendritic appendages and an axon ramifying in the vicinity of the soma. The TCR: Golgi type II ratio is about 7:3 in PL and PI, and 9:2 in PM.

Three types of synaptic terminals are observed: the RS, comprising about 80% of the total population; the RL, comprising about 10%; and the F, comprising about 10%. The first two contain round vesicles and make asymmetrical synaptic contacts, while the third contains both round and flat vesicles and makes symmetrical synaptic contacts. Characteristic groupings of synaptic terminals and dendrites, called “glomeruli”, appear to be organized for structured and efficient interactions. Adhesive contacts are observed between synaptic and non‐synaptic and non‐synaptic structures.

Comparisons with other thalamic nuclei are made, and the ultrastructural resemblance among all thalamic nuclei studied thus far is noted. The presence of glomeruli in all is discussed.
The synaptic organization of the cortical projection to the pulvinar of the squirrel monkey
Authors: Mathers Lawrence H.
Published: December 2004

The synaptic morphology of the pulvinar has been examined following cortical lesions in peristriate, posterior temporal and posterior parietal areas. Light‐microscopic stains demonstrate orthograde degeneration in p. lateralis, p. inferior, and the posterior nucleus, with a convergent input to the medial one‐half of p. inferior and the posterior nucleus. Electron microscopic examination shows that parts of two different populations of synaptic terminals degenerate as a result of the cortical lesions: the RS terminal, which rapidly becomes electron‐dense and later is phagocytosed, and the RL terminal, which initially exhibits signs of neurofilamentous hyperplasia and later becomes electron‐dense.

Comparisons are made between the pulvinar and other thalamic nuclei with respect to synaptic organization and the origin of extrinsic synaptic terminals. It is pointed out that while the overall arrangements within the pulvinar are equivalent to those in VB, MGB or dLGN, the fact that two different populations of synaptic terminals originate in the cortex suggests functional differences between the pulvinar and other parts of the thalamus examined thus far. The possible phylogenetic origins of different parts of the pulvinar are also discussed.
The dendritic tree of spinal neurons in dogs with experimental hind‐limb rigidity
Authors: Gelfan Samuel , Kao Grace , Ling Hannah
Published: December 2004

The dendritic tree of lumbosacral neurons from dogs with experimental hind‐limb rigidity, produced by temporary lumbosacral ischemia, was reduced to about one‐third of the mean normal size, as previously established in Golgi‐Kopsch preparations. The size reduction was due to the loss only of the more distal segments of the tree by the neurons which survived the ischemic episode, thus decreasing the mean radius of the dendritic projections. The mean number of primary dendrites/neuron remained essentially the same as in the normal but the portions extending beyond about 100 μ from cell body, and all their branches, suffered truncation: the branches originating closer to the cell body suffered the same truncation beyond the 100 μ border. The mean perikaryon size and size range in the sample of 300 neurons from three rigid dogs was not reduced from that of the 360 neuron sample from three normal animals. The loss of nearly two‐thirds of dendrite surface, with consequent loss of all contacts with other neurons normally handled by this major fraction of the dendritic tree, compounded the denervation and isolation sustained by the cell body and surviving proximal part of the tree, due to the marked mortality of interneurons during the ischemic episode. The reduction of the mean of the calculated synaptic endings/neuron for the entire sample to less than one‐fifth of normal and the narrowing of the range of synaptic populations/neuron to one‐seventh of normal are some indications of the magnitude and consequences of this morphological alteration; an alteration concomitant with the demonstrated functional alterations in such neurons. The orderliness of the dendrite organization, as found in the sample of normal neurons, however, did not change to randomness in the altered, „spastic”︁ ones. The peripheral portion of the dendritic arborization failed to survive the denervation and was promptly sloughed, it is postulated, because of its greater vulnerability to denervation, due to a greater dependency upon a continuous transneuronal supply of neurotrophic factors. This dependency may increase exponentially with increasing distance of dendrite segments from cell body. The concept of neuronal interdependence (Gelfan, '64) is extended to include viability of at least part of the dendritic tree.
The projection field of the stria terminalis in the rat brain. An experimental study
Authors: De Olmos Jose S. , Ingram W. R.
Published: December 2004

The problem of the stria terminalis projection field has been examined by use of two versions of the cupric‐silver technique as well as variations of the Fink‐Heimer and Nauta‐Gygax techniques applied to material fixed under different conditions using brains from very young rats surviving 30 hours to four days after production of lesions at different levels of the course of the stria terminalis and related structures. The findings are as follows:

A dorsal subventricular portion of the stria terminalis divides into retrocommissural and supracommissural contingents which together account for degenerating terminals seen in the ipsilateral bed nuclei of the stria terminalis and of the anterior commissure, and in the medial preoptic‐hypothalamic junction area. The supracommissural bundle also disseminates into the laterobasal septum, nucleus accumbens, olfactory tubercle, the posterior and medial divisions of the anterior olfactory nucleus, and the granular layer of the accessory olfactory bulb. Additional fibers end in the paucicellular capsule of the ventromedial hypothalamic nucleus, also in a small lateral parvocellular tuberal nuclear area, and throughout the premammillary nuclei. A small truly commissural division of the dorsal component was traced to the contralateral cortical amygdaloid nucleus and to small clusters of medial amygdaloid cells.

A ventral juxtacapsular portion of the stria terminalis was traced to the ipsilateral strial bed nucleus, medial preoptic‐hypothalamic junction area, the entire ventromedial hypothalamic nucleus, the lateral tuberal area and the premammillary nuclei. The lateralmost fibers of the dorsal strial component as well as those of the ventral component which lie lateral to the “commissural bundle” appear to terminate exclusively in the lateral portions of the bed nucleus of the stria.

A “commissural bundle” or component, after crossing the midline in the anterior commissure, ends in the bed nucleus of the posterior limb of the latter, in the olfactory tubercle, prepiriform cortex, lateral amygdaloid nucleus and the strial bed nucleus. It is thus a decussation rather than a commissure. No contribution from stria terminalis to stria medullaris could be identified.
Retinofugal pathways in two marsupials
Authors: Royce G. James , Ward Jeanette P. , Harting J. K.
Published: December 2004

Autoradiographic and anterograde degeneration tracing methods were used to study and compare the organization of retinofugal pathways in two marsupial opossums, Didelphis virginiana and Marmosa mitis. Seven identical retinal targets were demonstrated for each opossum. These include: (1) the suprachiasmatic nucleus of the hypothalamus, (2) the dorsal and (3) ventral lateral geniculate nuclei, (4) the lateral posterior nucleus, (5) the pretectal complex, (6) the superior colliculus and (7) the accessory optic nuclei.

While the pattern of retinal input to six of the seven targets was quite similar in the two species, the organization of the retinogeniculate pathways exhibited striking differences. In particular, our autoradiographs reveal no separation of ocular inputs within the lateral geniculate nucleus of Didelphis, i.e. the ipsilateral input is overlapped completely by the more extensive contralateral projection.

In contrast, there is considerable separation, as well as overlap, of the ocular inputs within the lateral geniculate nucleus of Marmosa. Our autoradiographs reveal several distinct bands of label within each geniculate nucleus, and upon superimposing the nuclei, ipsilateral and contralateral to the placement it is apparent that two of the bands overlap, while five do not (three ipsi, two contra).
An anatomical study of some somesthetic afferents to the intercollicular terminal zone of the midbrain of the opossum
Authors: RoBards Martine J. , Watkins David W. , Masterton R. Bruce
Published: December 2004

Following lesions of the dorsal column nuclei, spinal cord and sensorimotor cortex, anterograde degeneration was traced to a common target in the central midbrain: the intercollicular terminal zone. Although not all the midbrain projections of the three pathways are contained within this zone, it receives overlapping projections from each of the three body‐related somesthetic pathways studied. The intercollicular terminal zone covers the entirety of the external nucleus of the inferior colliculus and the intercollicular nucleus of Mehler, spilling over into adjacent parts of the central gray and deep layers of the superior colliculus. Little evidence of somatotopy in the somesthetic projections was disclosed, and bilateral input was found in each experimental case, regardless of the type of lesion. Golgi‐stained material was examined to explore the basis of the extensiveness of the terminal zone. These materials showed that the dendritic spread of neurons in the external nucleus of the inferior colliculus and the intercollicular nucleus, taken together, covers the entirety of the intercollicular terminal zone. That is, the dendrites invade the same portions of the central gray and deep layers of the superior colliculus which are covered by the terminal field. We conclude that a tripartite division of the sensory midbrain may be justified: with the somesthetic modality being represented anatomically in a fashion at least roughly analogous to that of vision and audition.
Postnatal development of the cerebellar cortex in the rat: V. Spatial organization of Purkinje cell perikarya
Authors: Altman Joseph , Winfree Arthur T.
Published: December 2004

The development of the spatial organization of Purkinje cell perikarya was examined in the rat cerebellum from birth to adulthood. Dispersion of the perikarya following birth is made possible by the rapid expansion of the cortical surface. Their subsequent regular monocellular alignment is ensured by mechanical factors, the pressure exerted from below by the expanding granular layer and the barrier formed above by the pile of parallel fibers which prevent the penetration of the bulky perikarya into the molecular layer. The perikarya remain in this position even after the slender stem dendrite pierces the molecular layer along the descending axons of basket cells.

The increase in interperikaryal distance between Purkinje cells is rapid up to day 12, then declines. This is temporally associated with the growth of the basket cell plexus and glial envelope around the perikaryon. The increase in perikaryal size continues up to day 30. This may be temporally associated with the growth of the Purkinje cell dendritic arbor as reflected by the expansion of the molecular layer up to day 30.

The spatial arrangement of Purkinje cells within the monocellular sheet was graphically displayed with computer aid. In the adult cerebellum a hexagonal arrangement could be recognized in a proportion of “near‐neighborhoods,” consisting of about six Purkinje cells and their neighbors. When the neighborhoods were extended with fixed orientation with respect to the axis of the folium, the hexagonal arrangement disappeared. When orientation was ignored, the superimposed nearneighborhoods could be rotated to produce a hexagonal pattern. In the infant cerebellum the hexagonal arrangement could not be demonstrated before the alignment of Purkinje cells in a monolayer. Thereafter there appeared to be an increase with age in the proportion of hexagonally arranged near‐neighborhoods.

It was concluded that in the monocellular ganglionic layer Purkinje cells are not aligned in regular rows with respect to the geometrically arranged elements of the supraganglionic layer. The formation of an imprecise hexagonal pattern, like the alignment of Purkinje cells in a monolayer, was attributed to mechanical factors.
Effects of low‐level X‐irradiation on cat cerebella at different postnatal intervals: II changes in purkinje cell morphology
Authors: Anderson William J. , Stromberg Melvin W.
Published: December 2004

The whole‐head of infant kittens was irradiated with fractionated doses of 150 R and 200 R at different postnatal intervals. Experimental age conditions consisted of an irradiated newborn, 1‐week, 2‐week, 3‐week, and a 4‐week age condition while the age of sacrifice remained constant at 70 days. The molecular layer thickness was reduced by 47% in the newborn, 40% in the 1‐week group, 17% in the 2‐week group, 19% in the 3‐week group and by 9% in the 4‐week group. An evaluation of Golgi impregnated material revealed that the dendritic arborizations of Purkinje cells were consistently reduced the earlier the age at which radiation was begun. A reduction in spiny branchlets was seen in all of the experimental conditions. All experimental age conditions displayed the phenomenon of dendritic “damming” at the pial surface, which consisted of an excessive crowding of spiny branches at this level. An increased growth of the primary dendrite before branching tood place was seen in the newborn and 1‐week group. This became less but was still significant in the 2‐week group. A correlation of this phenomenon with the presence or lack of stellate cells is discussed. Purkinje cells with two or more dendrites emerging from their soma were classified and analyzed separately. It was found that the primary dendritic branching in these cells often followed separate morphological patterns and appeared to be independent of each other. Climbing fibers were found to conform to the abnormal dendritic arborizations of the Purkinje cells, and were reduced in complexity in the early radiation treatment groups. This suggested that climbing fibers had no influence upon the dendritic growth pattern, but instead were under the influence of the Purkinje cell dendritic growth.
Abnormal interhemispheric connections in the visual system of boston siamese cats: A physiological study
Authors: Shatz Carla
Published: December 2004

In the normal cat most visual fibers in the splenium of the corpus callosum are concerned with a representation of the vertical meridian of the visual field. These fibers for the most part originate from cortical regions forming the border between adjacent architectonic areas, such as the anatomical 17‐18 border. Due to a genetic mutation in Boston Siamese cats, the anatomical 17‐18 border now represents a region in the ipsilateral visual field roughly 20 degrees away from the vertical meridian, and the representation of the vertical midline is displaced from the border to regions within areas 17 and 18 proper. Do visual fibers in the Boston Siamese cat corpus callosum originate, as in normal cats, from the 17‐18 border even though the vertical meridian is no longer represented there? The present paper deals with this question from a physiological standpoint.

Single visual fibers in the corpus callosum of 11 Boston Siamese and two normal cats were recorded using extracellular microelectrodes. Receptive fields were mapped and their positions used to infer the likely cortical site of origin for each fiber. In confirmation of earlier findings, most callosal receptive fields in the normal cat were closely apposed to the vertical meridian, as would be expected if only those visual cortical regions which represent the vertical meridian, such as the border between areas 17 and 18, contribute to the corpus callosum. In Boston Siamese cats, however, an abnormally large amount of visual field was represented in the corpus callosum, with some receptive fields located as far as 25 degrees away from the vertical meridian. The representation of the vertical meridian was nevertheless substantial.

The present findings suggest, therefore, that in Boston Siamese cats callosal fibers do not originate solely from the boundary regions between adjacent cortical areas, such as the anatomical 17‐18 border, but originate also from other cortical regions, especially the vertical meridian representation, regardless of their location with respect to such boundaries.
An intricately patterned prefronto‐caudate projection in the rhesus monkey
Authors: Goldman Patricia S. , Nauta Walle J. H.
Published: December 2004

The distribution of prefronto‐caudate fibers in the caudate nucleus was studied autoradiographically in monkeys of various ages in which tritiated amino acids had been injected into the middle one‐third of the length of the dorsal bank of the principal sulcus. The results indicate that, contrary to previous reports which had suggested a projection to only the head of the caudate nucleus, area 9 of Brodmann projects to the entire length of the nucleus.

In the head of the caudate nucleus the cortico‐caudate fibers are distributed in a pattern which is remarkable in two respects. First, the grains are not uniformly distributed but rather are segregated into clusters separated from one another by territories in which grain density does not exceed background. Second, individual clusters of grains, circular or elliptical in shape, surround grain free cores. These patterns of fiber distribution within the head of the nucleus are more sharply defined in newborn than in older monkeys. Our findings suggest that the caudate nucleus is organized more as an anatomic and functional mosaic than as the homogeneously organized structure that it is commonly considered to be.
Retinal projections in larval, transforming and adult sea lamprey, Petromyzon marinus
Authors: Kennedy Michael C. , Rubinson Kalman
Published: December 2004

Unilateral enucleations were performed on larval, transforming and adult sea lampreys. Following 5 to 11 days survival, the animals were sacrificed and the brains were processed using a modified Fink‐Heimer technique. In larvae, contralateral optic projections were found to the posterior one‐third of the dorsal thalamus, the pretectum, and the optic tectum. No ipsilateral projections were present in the larvae. In enucleated transforming and adult lampreys, degenerating axons were observed in the optic chiasm and bilaterally in the optic tracts. Retinal efferents projected bilaterally to a lateral neuropil region (“tractus opticus”) in the posterior one‐half of the dorsal thalamus. Contralaterally, a conspicuous dorsomedial cell group (lateral geniculate nucleus) also received a projection. Contralateral projections to the superficial layers of the pretectum and optic tectum were observed. Ipsilateral retinal projections to the pretectum and optic tectum in transforming and adult lampreys were restricted to a small zone at the ventrolateral margins of the pretectum and tectum. The changes in distribution of retinofugal projections during transformation appear to be occurring at the same time that the eye differentiates into its adult form.
Central connections of ventral root afferents as demonstrated by the HRP method
Authors: Maynard Christine W. , Leonard Robert B. , dan Coulter Joe , Coggeshall Richard E.
Published: December 2004

To study the central connections of ventral root afferents, horseradish peroxidase was injected into the lumbosacral spinal cord of the cat and the appropriate dorsal ganglia were examined from segments with (1) both dorsal and ventral roots intact, (2) both roots sectioned, and (3) only the dorsal root sectioned. The key finding was that a number of labeled cells (up to 133) were observed in the ganglion after dorsal rhizotomy. We interpret these findings to mean that the central processes of the labeled cells projected to the spinal cord through the ventral root. As expected, when both roots wer cut, almost no cells were labeled and when both roots were intact, there were large numbers of labeled cells.

Of the labeled cells observed in ganglia after dorsal rhizotomy, all were found to be within the ganglion itself. No labeled aberrant dorsal root ganglion cells could be found.
Neurogenesis in the epithalamus, dorsal thalamus and ventral thalamus of the rat: An autoradiographic and cytological study
Authors: McAllister James P. , Das Gopal D.
Published: December 2004

Times of final mitotic division for neurons of the epithalamic, dorsasl thalamic and subthalamic nuclei of the rat were determined with the aid of thymidine‐H3 autoradiography. Intensely labelled neurons were observed in the brains of animals injected with radiochemical from days 13 to 19 of gestation. The pattern of distribution of the labelled neurons indicated that neurogenesis in these regions followed caudorostral, lateromedial and ventrodorsal neurogenetic gradients, all of which were found to operate simultaneously. Since neurogenesis in the epithalamus, subthalamus and caudolateral thalamic regions began on days 13 and 14 of gestation, the ventrodorsal and lateromedial proliferative gradients were clearly discerned only within the ventral and dorsal thalamus exclusive of the epithalamus. These directional neurogenetic gradients were apparent throughout the entire thalamus and within individual thalamic nuclei. No neurogenetic pattern based upon neuronal size was observed, i.e., large neurons were not preferentially formed earlier than smaller ones. Detailed information has also been provided on the cytological character of each thalamic nucleus.
Genetically‐associated variations in the development of hippocampal pyramidal neurons may produce differences in mossy fiber connectivity
Authors: Vaughn James E. , Matthews Dee Ann , Barber Robert P. , Wimer Cynthia C. , Wimer Richard E.
Published: December 2004

The neuronal generation patterns of hippocampal pyramids were analyzed in two inbred strains of house mice (SM/J and BALB/cJ) using tritiated thymidine radioautography. These two strains of mice possess markedly different patterns of mossy fiber synapses upon pyramidal neurons within a specific segment of regio inferior. The results of this study show that this same segment of regio inferior also displays markedly different patterns of pyramidal neuron generation in the two strains. Specifically, the pyramids of this segment of regio inferior are generated according to the typical [inside‐out] sequence in SM/J mice, but this pattern is reversed into an [outside‐in] sequence in BALB/cJ mice. The remaining segment of regio inferior, and all of regio superior, is formed in an inside‐out sequence in both strains. These results strongly suggest that altered temporal patterns of pyramidal neuron generation may play a major role in determining mossy fiber connectivity patterns.
Cells of origin and terminal distrubution of corticostriatal fibers arising in the sensory‐motor cortex of monkeys
Authors: Jones E. G. , Coulter J. D. , Burton H. , Porter R.
Published: December 2004

The cells of origin of the corticostriatal projection have been identified in squirrel monkeys by the use of the retrograde horseradish peroxidase method. In the subfields of the somatic sensory, motor, parietal and frontal areas of the cortex, cells projecting to the ipsilateral striatum are relatively sparsely distributed and form a group of small‐ to medium‐sized pyramidal cells with an average somal diameter from area to area of 14‐16 μm. Such cells are found only in layer V of the cortex (mainly in the more superficial parts of the layer). Since they are consistently smaller than the pyramidal cells of layer V that project to the brainstem and spinal cord and since they lie outside layer VI which gives rise to corticothalamic axons, the corticostriatal axons are unlikely to be collaterals of axons projecting to other sites.

The cells of origin of the'crossed corticostriatal projection are also found in layer V and are pyramidal cells with somal diameters in the same range as above. They are found only in areas 4, 8 and 6.

Studies with the anterograde, autoradiographic method in rhesus, cynomologous and squirrel monkeys, indicate that the somatic sensory areas project to most of the antero‐posterior extent of the ipsilateral putamen. Subareas 3a, 3b, 1 and 2 of the somatic sensory cortex project to the same region and the projection overlaps similarly extensive projections from the motor and certain other areas of the cortex. However, in each case the pattern of terminal labeling is in the form of interrupted clusters, strips and bands. A single small injection of the cortex is associated with only one or two such clusters of terminal labeling. This seems to imply that individual corticostriatal fibers end in a very restricted manner and that the terminal ramifications of fibers from one cortical area may alternate in the putamen with those arising in other areas.
Efferent connections of cortical, area 8 (frontal eye field) in Macaca fascicularis. A reinvestigation using the autoradiographic technique
Authors: Künzle H. , Akert K.
Published: December 2004

The efferent projections from the cortical area 8 (frontal eye field) have been re‐examined in four adult monkeys (Macaca fascicularis) by injecting small amounts of H3 ‐proline into the rostral bank of sulcus arcuatus and using the autoradiographic tracing technique. Ipsilateral cortical projections could be traced into specific areas of the depths of sulcus principalis, sulcus temporalis superior and sulcus intraparietalis. Label was found contralaterally in area 8. Subcortical connections were observed ipsilaterally to n. caudatus, putamen, claustrum, n. ventralis anterior pars magnocellularis, n. medialis dorsalis pars multiformis and pars densocellularis, n. centralis lateralis and paracentralis, n. parafascicularis, n. pulvinar oralis, zona incerta, n. subthalamicus, pretectal area, colliculus superior and griseum pontis as well as to the ipsi‐ and contralateral n. reticularis tegmenti pontis. Negative results were obtained with respect to the oculomotor nuclei, n. interstitialis and Darkschewitsch as well as to the paramedian pontine reticular formation.
The development of monoamine‐containing neurons in the brain and spinal cord of the salamander, Ambystoma mexicanum
Authors: Sims Terry J.
Published: December 2004

The distribution of monoamine‐containing neurons in the CNS of the developing and adult axolotl, Ambystoma mexicanum, has been investigated using the histochemical fluorescence technique of Falck and Hillarp combined with microspectrofluorimetry. The earliest catecholamine‐containing neurons to be detected are located in the ventral ependymal zone of the spinal cord at the time of hatching (Stage 41). Between stages 43 and 46, catecholamine fluorescence can be detected in neurons in the following regions: nucleus preopticus, the hypothalamic‐infundibular region, and the brain stem reticular fomation. 5‐HT‐containing neurons are only observed in the midbrain raphe region and are first detected at stage 44. In contrast to these early monoamine fluorescing groups, catecholamine‐containing neurons are not routinely detectable in the nucleus interpeduncularis until six months of age. All monoamine‐containing neuronal groups detected in developing axolotls are also present in both sexes of the adult. However, the fluorescence intensity is less in monoamine‐containing neurons observed in adults than in early developing subjects.

All catecholamine‐containing neuronal groups, with the exception of those located in the midbrain region (nucleus interpeduncularis, reticular zone) have fluorescent processes that contact the cerebrospinal fluid (CSF). The presence of CSF‐containing processes in the hypothalamic and spinal cord regions suggest that the CSF may act as a medium through which bioactive substances are transported from one brain region to another. Intense catecholamine fluorescence is observed in cells of the notochord prior to the detection of monoamine‐containing neurons in the CNS. A possible involvement of catecholamines in the inductive effects of the notochord during development is discussed.