bluuebunny/crossref_metadata_2025 huggingface dataset:
Degeneration of some intralaminar thalamic nuclei after cortical removals in the cat
Authors: Murray Marion
Published: January 2005

The projections of the central medial, paracentral, and central lateral nuclei of the cat have been studied by the method of retrograde degeneration.

Following removal of neocortex, with preservation of rhinencephalic and sub‐cortical structures, the central medial, paracentral, and central lateral nuclei degenerate severely.

The central medial and paracentral nuclei degenerate only after extensive cortical lesions which include limbic cortex. There is evidence of a topographical organization of the projection since rostral sectors of central medial and paracentral nuclei show cell loss after lesions involving anterior limbic and orbitofrontal cortex while caudal sectors degenerate after lesions involving cingulate and parieto‐occipital cortex.

The central lateral nucleus projects to cortex of the parieto‐occipital region.

Some findings are considered which indicate that fibers from the central medial, paracentral, and central lateral nuclei travel rostrally to the region of the head of the caudate nucleus before turning caudally to distribute to cortical areas.
Descending hypothalamic medullary pathways in the cat
Authors: Cheatham Melvin L. , Matzke Howard A.
Published: January 2005

Posterior hypothalamic electrocoagulative lesions were stereotaxically placed in 20 cats. The resulting degenerating pathways to the medullary centers were studied using the Nauta technique. The size of the lesions was less than 1 mm in diameter. The resulting degeneration did not conform to a discrete pathway but passed in a diffuse manner into the brainstem reticular formation. In the lower medulla the degenerating axons appeared to become more concentrated in the dorso‐lateral visceral gray in close association with the dorsal motor nuclei of X. Pre‐terminal axons were noted adjacent to large and medium sized neurons in this area. A progressive decrease in degenerating fibers was apparent below this level. A small number of degenerating axons could be identified in the lateral reticular process of the central gray matter at the level of C2.
Projections from the fornix to the hippocampal formation in the squirrel monkey
Authors: DeVito June Logan , White Lowell Elmond
Published: January 2005

In six squirrel monkeys, lesions involving the septum and fornix were made during aseptic operations. After postoperative survival periods ranging from 9 to 22 days, the animals were sacrificed under anesthesia by intracardiac perfusion of 10% formalin. The brains were sectioned and stained with the Nauta method for demonstrating degenerating axis cylinders. Degenerating fibers were traced from the fimbria into the hippocampal formation. Although degenerating fibers were present in all regions of the hippocampal formation, the main sites of degeneration were the hilus of the fascia dentata; the strata oriens, pyramidale and radiatum of the cornu ammonis; the caudal presubiculum; the parasubiculum and the entorhinal area.
The microscopic anatomy and ulrastructure of the nervous system in the earthworm (Lumbricus sp.) with emphasis on the relationship between glial cells and neurons
Authors: Levi Joe U. , Cowden Ronald R. , Collins George H.
Published: January 2005

Subesophageal ganglia and the first four ventral chain ganglia from earthworms of the genus Lumbricus were examined by light and electron microscopy. Trypan blue injections indicated that this substance does not pass beyond the cord sheath. Tritiated isoleucine displayed a general non‐neuronal distribution after one‐half hour exposure but the amino acid was progressively concentrated in neurons at 1 and 2 hours. Ultrastructural studies indicated that a form of cytoplasmic inclusion was common to glial cells and neurons, and that a similar type material was present extracellularly in the cord sheath. Three distinct variations of glial cytoplasm were recognized at the ultrastructural level, and these appeared to be conditioned by the location of the glial cell in the nervous system. A sequence of morphology was observed which suggests that glial cells in the earthworm transport material from the cord sheath to the neurons. The glia directly associated with neurons sent a number of invaginating processes into the neuron which may from the anatomical basis for exchange of materials.
The lumbar, sacral and coccygeal tactile dermatomes of the dog
Authors: Fletcher Thomas F. , Kitchell Ralph L.
Published: January 2005

Tactile dermatomes L1 through Co5 were determined in the dog by electrophysiological recording. All dermatomes were continuous skin fields which extended from the dorsal to the ventral midlines and displayed considerable cranio‐caudal overlap. Most cutaneous regions were innervated by three dorsal roots, although some loci were supplied by two or four segments.

The dermatomes boundaries, which were determined in relation to palpable skeltal landmarks, displayed an inherent variability from subject to subject, around a most common distribution. This variability was limited to the distance of one vertebral spine, cranial or caudal to the mode boundaries.

Dermatomes exhibited central regions of maximal innervation where the response per rootlet appeared greater than at the periphery. The central‐peripheral sensitivity distinction was more remarkable in the limb dermatomes where proprioceptive afferents decreased tactile resolution at the periphery of the field. The maximal innervation zones appeared to approximate the locations of the major cutaneous nerves. The experimental findings suggest the hypothesis that the afferent fibers comprising a canine dorsal root are intermixed in the spinal nerve and are distributed at random within the dermatome.
Autoradiographic and histological studies of postnatal neurogenesis. II. A longitudinal investigation of the kinetics, migration and transformation of cells incorporating tritiated thymidine in infant rats, with special reference to postnatal neurogenesis in some brain regions
Authors: Altman Joseph
Published: January 2005

Thymidine‐H3 was injected intraperitoneally into 6‐ and 13‐day old rats and they lived afterwards for periods ranging from one hour to 60 days. Autoradiographic data obtained from animals surviving for short periods were used to estimate rates of regional cell proliferation. Animals with longer survival were used to deduce the movements of new cells from germinal sites, through migratory channels, to target areas, and to determine their mode of differentiation.

The formation and differentiation of microneurons goes on during infancy, though in most structures at a declining rate. In the wall of the olfactory ventricle cell multiplication continued at a high rate at six days, with a decline at 13 days, and the new cells migrated to the layers of the olfactory bulb. The migration of labeled cells from the lateral ventricle was traced, by way of the fimbria, to the polymorph cell layer of the dentate gyrus, and from there to the granular layer. The “older” granule cells were located in the upper part of the granular layer, the “younger” cells at its base. Cell multiplication continued at a very high rate in the external granular layer of the cerebellar cortex, whence cells migrated to the molecular layer and internal granular layer. Speed of migration was approximately 50 μU/day in the olfactory bulb, and 60–70 μ/day in the cerebellum. The possible significance of these findings was discussed.
A functional and histochemical characterization of motor units in a heterogeneous muscle (flexor digitorum longus) of the cat
Authors: Olson Camille B. , Swett Chester P.
Published: January 2005

This paper reports an attempt to differentiate motor units of several types both physiologically and histochemically.

The average characteristics of the motor units in the flexor digitorum longus (FDL), flexor hallucis longus (FHL) and soleus muscles of cats with one chronically deafferented hind limb were studied. The average maximal tension per motor unit was calculated to be 14.5 g for FDL, 25.8 g for FHL and 19.7 g for soleus. In general, the average size of the motor units in each muscle increased with the weight of the animal. The total number of motor units to each muscle and the diameters of all efferent nerve fibers were determined in histological cross‐sections of the deafferented nerve.

The FDL muscle was selected for study of individual units isolated from the ventral roots of 15 cats. The conduction velocities of 108 axons ranged from 71.3 to 114.3 m/sec. These units developed maximal isometric tensions ranging from 0.4 to 100.0 g, with an average of 9.6 g. The frequency distribution of maximal tensions was markedly skewed, with 83 units developing less than 10 g. The twitch tensions of 90 units averaged 0.9 g, with a range of 0.1 to 10.0 g. All units in which no twitch was detected developed less than 5 g of maximal tension. The small size of the units and the limitations of the equipment were thought responsible for the occasional failure to record a twitch. The contraction times of 85 units fell between 13 and 81 msec, with a modal class of 30 to 35 msec. During continuous stimulation at 100/sec, large units usually proved more susceptible to fatigue than small units. Regression analyses of conduction velocity versus maximal tetanic tension revealed that large units (> 19 g) belonged to a different population than units developing less than 19 g of maximal tension. In addition, the findings suggest that small units may perhaps be divided into a slow and fast group according to their contraction times.

Mitochondrial adenosine triphosphatase activity was demonstrated in cross‐sections of FDL muscle fibers. A correlation between histochemically distinguishable fiber types and functionally distinguishable motor units is proposed.
The development of hippocampal and dorsolateral pallial regions of the cerebral hemisphere in fetal rabbits. I. Fifteen millimeter stage, spongioblast morphology
Authors: Stensaas Larry J.
Published: January 2005

The structure of the cerebral hemisphere of 15 mm rabbit embryos was studied with aniline and Golgi stains. Three layers of successively less denselypacked cells were identified in aniline stained sections–matrix, intermediate, and marginal laminae.

In the matrix lamina two types of cells were identified in Golgi impregnations:

(1) neuroblasts with axons ascending to the intermediate and marginal laminae, (2) spongioblasts attached to the ventricular surface by a short proximal process. Two varieties of spongioblasts can be distinguished according to the mode of termination of long distal processes: (1) typical spongioblasts with claviform enlargements terminating at the pial surface, (2) freely‐arborizing spongioblasts with multiple short processes arborizing in the intermediate and marginal laminae.

The terminal arbors of freely arborizing spongioblasts, here recognized for the first time, may represent either the growing processes of immature spongioblasts destined to reach the pial surface, or an apparatus having special relations to the embryonic vessels and nerve processes.

In the intermediate lamina, pyramidal cells outline the plan of the cortex and subcortical white matter. They have apical dendrites that ascend and ramify in the marginal lamina and axons which descend and turn toward the base of the hemisphere. Neurons with ascending axons are also present, and elements with horizontal axons are located in both the marginal and intermediate laminae.
Degeneration of the presynaptic terminals (boutons) in the spinal cord of the cat after rhizotomy
Authors: Von Mihálik Peter
Published: January 2005

The degeneration of the boutons, following rhizotomy of the C2 roots, has been studied in cats' spinal cords fixed in Susa and stained by albumin‐silver impregnation on slides (Mihálik, '50).

It was found that, three days after the lesion, large rosette shaped argyrophilic structures appeared around the nerve cells and their dendrites. These structures disappeared the fourth day.

It was concluded that the presynaptic end‐branches of the severed postior root fibers do not undergo a granular degeneration in situ but first retract and metamorphose into “rosettes” and then disappear by further degeneration and absorbtion. This rosette forming is considered to be an agony reaction at the terminals of the severed posterior root fibers, and it is considered to be homologous to the metamorphic agony reaction (at the stump of the amputated part of the peripheral nerves) described by Cajal.
Mitotic division of neuroglia in the normal adult rat
Authors: Hommes Otto R. , Leblond C. P.
Published: January 2005

Twenty‐four adult rats were given an injection of 3H‐thymidine at 4.00 p.m. and sacrificed two at a time everyhour for the next 12 hours. Another 24 adult rats were similarly treated but after inejction at 4.00 a.m. The brainswere fixed by immersion in Bouin fluid. Sections were stained with hematoxylin‐eosin and radioautographed. In another experiment two animals were sacrificed two and nine hours respectively after 3H‐thymidine injection and the brains were fixed in formalin. The sections were stained by silver impregnation and radioautographed.

One hour after 3H‐thymidine injection, a number of glial nuclei were labeled: all were in intrphase. By 2–3 hours, labeled mitotic figures appeared and increased in number with time. From 4–5 hours after injection on, pairs of labeled nuclei were seen in increasing numbers. This sequence of events, which was observed with slight differences in the two main groups, indicated that labeled glia nuclei go through mitotic division.

It is concluded that a low degree of mitotic activity continually takes place in the glial population of adult rats. About one fifth of the divisions seem to be in microglia. Most of the others seem to occur in cells of the oligodendrocyte family.
Motor function and the corticospinal tracts in the dog and raccoon
Authors: Buxton Donald F. , Goodman Donald C.
Published: January 2005

Following unilateral somatomotor cerebral cortex ablation in three raccoons and ten Beagle dogs similar functional deficits of hypotonia, hypokinesia and dysmetria limited to the side opposite the lesion were observed in both species. Only in the raccoon was a loss of digital manipulative ability of the contralateral forepaw observed.

The Nauta‐Gygax method was used to trace corticospinal projections into the grey matter of the spinal cord. In both species preterminal degeneration was found ipsilaterally and contralaterally in Rexed's laminae V, VI, VII and VIII. Furthermore, in the raccoon preterminal corticospinal degeneration was followed into the dorsal portion of contralateral lamina IX at the level C7–8. Although direct corticospinal projections to motoneurones of lamina IX occur in greater quantity and in increasing quantity with increasing complexity of digital abilities among the primate species, it appears that such connections are not limited phylogenetically to primates and probably are correlated with the ability of a species to manipulate the digits.

Comparison of these anatomical findings with those reported for the cat revealed a progressive ventral shift of corticospinal terminations in ventral horn neuronal groups from cat to dog to raccoon, specifically into lamina IX in the raccoon. No single pattern of corticospinal terminations appears typical for the Order Carnivora.

Data on dogs varying in age from one month to adult support the suggestion that there is a direct correlation between some motor cortex functions and postnatal maturation of corticospinal connections.
Cortical projections to the lower brain stem and spinal cord in the tree shrew (Tupaia glis)
Authors: Shriver Joyce E. , Noback Charles R.
Published: January 2005

A study was made of corticofugal projections to the lower brain stem and spinal cord in the tree shrew (Tupaia glis). Degeneration resulting from selective ablations of the motor, sensory and frontal cortex in ten animals was studied by the Nauta technique. Following ablations of motor and sensory cortex degeneration was found bilaterally: (1) throughout the rostrocaudal extent of the lateral reticular formation, (2) in all trigeminal sensory nuclei and, (3) in the dorsal column nuclei (contralateral predominance). All three cortical areas projected fibers to the ipsilateral pontine nuclei and bilaterally to the medial reticular formation (ipsilateral predominance). Fibers from the motor cortex were distributed throughout the medial reticular formation; fibers from sensory and frontal cortex were distributed to selective regions of the medial reticular formation. The majority of corticospinal fibers decussated and descended to lower cervical (frontal fibers) and lower thoracic (motor and sensory fibers) levels. The small uncrossed component descended in the ipsilateral dorsal funiculus only throughout cervical segments. Corticospinal degeneration terminated primarily in the internal basilar region (medial half of lamina VI), medial aspect of the neck (lamina V) and, to a lesser extent, in the head (laminae III and IV) of the dorsal horn. Relatively few fibers projected to the zona intermedia (lamina VII) and no terminations were present in the motor nuclei (lamina IX) of the spinal nerves.
A comparative study of the extrinsic and intrinsic arterial blood supply to brains of submammalian vertebrates
Authors: Gillilan Lois A.
Published: January 2005

The brains of submammalian vertebrates are supplied only by the paired internal carotid arteries each of which divides into a caudal and a rostral division. In fishes,where the necessities of existence are taken care of largely by the respiratory and taste centers in the brainstem augmented by olfaction, the caudal division is the larger. As locomotion becomes more important and complex in reptiles and birds, the corpus striatum and the cerebellum become larger, necessitating a gradual shift of arterial blood into the rostral division. At the reptilian level the cerebral branches have evolved sufficiently to be recognized as having a mammalianlike pattern, and it is at this point that the mammalian terminology can be applied. Branches of the basilar artery, which is formed by the union of the two caudal rami, retain their basically segmental arrangement. The vertebral artery has not yet appeared.

The intrinsic vascular patterns are in the form of a wide‐meshed plexus, at first uniformly distributed among cells and fibers, but later more ldense in the nuclear areas. The first evidence of specialization in the vascular arrangement is the formation of a perineuronal plexus within the optic lobes in amphibians and in the appearance of a definitive striate artery. The vascular patterns are correlated with the phylogenetic development and the general functional development of members of each of the classes described.
Patterns of fiber degeneration in the dorsal lateral geniculate nucleus of the cat following lesions in the visual cortex
Authors: Guillery R. W.
Published: January 2005

Golgi preparations show a group of relatively fine axons ending in the dorsal lateral geniculate nucleus. These, the type I axons, are characterized by many short collateral terminal branches and form a well oriented plexus within the lateral geniculate nucleus. Individual axons distribute terminals to more than one geniculate lamina and some can be seen to come from the region of the internal capsule.

Four or more days after damage to the visual cortex, the Nauta method shows relatively fine degenerating fibers that approach the lateral geniculate nucleus from a rostral direction. Some pass straight into lamina a, While others enter the three major laminae via the central interlaminar nucleus. The appearance of this degeneration suggests that the type I axons are cortico‐genciulate, as does the sequence of the diencephalic degenerative changes. Thus, relatively coarse corticofugal fibers to the lateral thalamus and tectum show heavy degeneration within three days. The fine axons in the lateral geniculate nucleus show slight, early degeneration after three days, extensive degeneration after four days. They are possibly collaterals of the coarser corticofugal fibers. A second group of coarse fibers which runs laterally from the lateral geniculate nucleus shows early degeneration after four days but does not show consistent and clear degeneration until five or more days. Since retrograde cell changes are already recognizable after four days the third group is regarded as geniculo‐cortical.
Electron microscopic studies of the dentate gyrus of the rat. II. Degeneration of commissural afferents
Authors: Laatsch R. H. , Cowan W. M.
Published: January 2005

Experimental degeneration of the commissural afferents to the dentate gyrus of the rat has been studied using the electron microscope. Four and six days after unilater fimbrial section, unequivocal degeneration of axon terminals is found in the inner part of the molecular layer of the dentate gyrus of the opposite side. The affected endings are in synaptic contact both with the shafts of the granule cell dendrites and with the short dendritic spines which occur on the granule cell dendrites in this part of the molecular layer. These degenerating terminals show changes ranging from an increased axoplasmic density with aggregation of the synaptic vesicles, to a complete disappearance of the vesicles and mitochondria, and the engulfment of the endings by glycogen‐containing processes of glial cells. There is no proliferation of neurofilaments at any stage during this degeneration. Glial processes in the vicinity of degenerating axon terminals show reactive changes in the form of swelling and accumulation of glycogen, and probably proceed to phagocytosis of the degenerating nerve endings. On the side of the lesion the glial cells also show fibril proliferation, an even greater accumulation of glycogen, and a variety of ingested cellular debris.
Thalamic afferents from the dorsal column nuclei. An experimental anatomical study in the rat
Authors: Lund R. D. , Webster K. E.
Published: January 2005

The distribution of axons originating in the dorsal column nuclei has been studied using the Nauta technique on brains witth lesions restricted to small parts of the gracile and cuneate nuclei. The caudal area of each nucleus projects contralaterally to the ventrobasal complex in a topographical manner and in small amount to the pars medialis of the medial geniculate body. In addition, the rostral part of each nucleus sends axons to the contralateral zona incerta, anterior pretectal nucleus and posterolateral complex within the diencephalon as well as to the collicular plate and pontine protuberance of the brain stem. There is no clear evidence of a projection to the area comparable to the posterior thalamic complex of the cat.

This work establishes the identity of some of the cytoarchitectonic divisions of the rat diencephalon, and indicates that the rostro‐caudal differences shown for the dorsal column nuclei are reflected in their ascending projections.
Formation and differentiation of the external granular layer of the chick cerebellum
Authors: Hanaway Joseph
Published: January 2005

To examine the formation and differentiation of the external granular layer, chick embryos ranging in age from two to 20 days were treated with tritiated thymidine and sacrificed after various time intervals. By studying the migration of the labeled cells at different stages of development, the following observations were made: (1) cells originating from the neuro‐epithelial layer along the ventricular surface of the cerebellar plate migrate through previously formed cell layers of neuroblasts to the surface; (2) the development of the lateral portion of the cerebellar plate is approximately 24 hours more advanced than that of the medial region, thus explaining the appearance of the external granular layer first laterally and then medially; (3) at no time during development can a proliferation center be found in the ventrolateral angle of the fourth ventricle. Based on theses results, it is concluded that the cells of the external granular layer originate from the neuroepithelium bordering the ventricular surface of the cerebellar plate and migrate from this position straight to the surface. No evidence for a surface migration from the ventrolateral angle in a dorsomedial direction can be found.

Shortly after the formation of the external granular layer at day six, its cells begin to proliferate. During this period, which lasts until day 15, relatively few cells leave the external granular layer to migrate inwards. After this day a massive inward migration occurs, and the cells of the external granular layer differentiate into the granular cells and perhaps the glia cells. In the internal granular layer they intermingle with the Purkinje cells and Golgi II neurons, which originate in the neuro‐epithelial layer between days three and six of development. Shortly after hatching, when the external granular layer has fulfilled its function in cell production, it disappears.
Thalamic projection of the anterior ectosylvian gyrus (somatic area II) in the cat
Authors: DeVito June L.
Published: January 2005

Thalamic degeneration following discrete lesions of the portion of somatic area II lying within the anterior ectosylvian gyrus was observed in coronal and parasagittal sections. The sections had been treated by Nauta's silver impregnation method and stained alternately with cresyl violet or the Luxol fast preparation. The main site of degeneration lay in the posterior nuclear group, in a band of cells and fibers interposed between the ventrobasal complex and the medial geniculate body. Terminal degeneration was also present throughout the lateral region of the ventrobasal complex, being most dense caudolaterally. The dual thalamic connections reinforce electrical evidence of two populations of cells in somatic area II.
Pattern and field in cortical structure: The rabbit
Authors: Globus Albert , Scheibel Arnold B.
Published: January 2005

Previous attempts at classification of cortical neurons have been based on a number of anatomical characteristics, some of doubtful physiological significance. In seeking a functionally more relevant scheme, we have based our classification on three neural attributes; (a) size and shape of the dendritic domain, (b) presence or absence of dendritic spines, and (c) intra or extra‐cortical trajectory of the axon, as revealed in Golgi stained material. Our data indicate that neurons with extra‐cortically projecting axons (long axons) invariably possess spine‐rich dendrites forming domains with remarkably regular horizontal parameters (i.e. modular domains). Cells with axons limited to intra‐cortical paths (short axons) are characterized by spine‐poor or spine‐free dendrites forming domains which are highly variable in size and shape. These two categories appear dependant on structural characteristics related both to input and output functions of cortical neurons, and are called Class I and II, respectively. The significance of synaptic arrangements along horizontal and vertical components of Class I dendritic modules are compared with those for Class II cells, and possible relationships between dendritic structure and temporo‐spatial activity patterns are considered.
The non‐crossing of the pyramidal tract in procavia capensis (storr) and other instances of absence of the pyramidal crossing
Authors: Verhaart W. J. C.
Published: January 2005

In Procavia capensis the pyramidal tract descends uncrossed in the ventral funiculus of the cord, in which it can be followed throughout, the thoracic and lumbar segments. Termination of it fibers is almost entirely crossed similar to mammals with a substantial pyramidal corssing. Other instances of absence of a substantial pyramidal crossing are reported and it is concluded that the pyramidal crossing does not depend only on the termination of the pyramidal fibers in the medulla and the cord, and that the fibers can reach their contralateral endings without such a crossing.
Electrosensitivity of canal and free neuromast organs in a gymnotid electric fish
Authors: Suga Nobuo
Published: January 2005

The posterior lateral line nerve was studied by recording singel unit activity with glass miocropipette electrodes to examine the electrosensitivity of the canal and free neuromast organs. The fibers innervating these organs has no or irregular spontaneous discharges. For a 50 msec electric pulse applied through a pair of electrodes at the two ends of the fish, almost all fibers discharged impulses during the pulse, irrespective of its polarity. The electrosensitivity for a 50 msec electric pulse was 37 mV/cm on the average. When a 0.5–1.0 msec electric pulse was used, these fibers showed no responses to it, even if it was stronger than 40 mV/cm. Responses to organ discharges were not found at all. These organs do not seem to function as electroreceptors.

The canal organ was excited by water ripple and by weak water currents allied to the trunk and can be considered a mechanoreceptor. The free neuromast of the trunk was mechanically excitable, but it did not respond to moderately strong water current, and its function remains unclear.
Helweg's triangular fasciculus in anencephalic fetuses
Authors: Mizuno Noboru , Yoshida Masami , Okamoto Michio
Published: January 2005

Helweg's triangular fasciculi were identified in two human anencephalic fetuses, and the structures of their central nervous systems were compared with those of other anencephalic fetuses without the fasciculi.

Since the inferior olivary nuclei and the brain regions above the level of the mesencephalon were not developed, these portions could be ruled out as the site of origin of Helweg's fasciculi.

The spinal cords and the ascending fibers of these anencephalic fetuses were better preserved than the brain stem and descending fibers. In cases with existing Helweg's fasciculi the spinal gray matter was better developed than in cases without the fasciculus. Taking all these facts in account, it seems reasonable to assume that in the described cases Helweg's fasciculi consist, at least chiefly, of ascending fibers, especially spinoreticular fibers.
The efferent connections of the cerebellar nuclei in the pangolin,
Authors: Bautista Nestor S. , Foltz Floyd M.
Published: January 2005

The connections of the cerebellar nuclei were traced in a primitive and specialized eutherian mammal, the pangolin, by placing varied unilateral lesions in the basal cerebellar nuclei and staining the ensuing fiber degeneration with the selective staining techniques of Marchi and Nauta. The results showed a cerebellifugal system that is basically similar to the pattern described for other mammals. The brachium conjunctivum arises primarily from the interpositus and dentate nuclei and follows the typical mammalian course and termination in the red nucleus and thalamus. In addition, a rather extensive termination in the dorsal mesencephalic tegmentum is present. A variation was observed in the descending limb of the brachium conjunctivum which divides into two tracts, medial and lateral. The fastigial projections are directed mainly to caudal rather than rostral areas with extensive terminations in vestibular and reticular areas.

The present study establishes further the constancy of the general organization of cerebellar efferents in mammals and the primitive position of the cerebellifugal system in phylogeny. An assumption is made that the efferent connections of the cerebellum are present in one form in all therian mammals.
Observations on the abdominal stretch receptor and the fine structure of associated axo‐dendritic synapses and neuromuscular junctions in homarus
Authors: Nadol Joseph B. , de Lorenzo A. J. Darin
Published: January 2005

The abdominal stretch receptor of lobster has been examined. Fine structural details of the receptor nerves are presented and neurophysiological correlations are suggested. Both axo‐dendritic synapses and neuromuscular junctions were examined. Axo‐dendritic synapses are of one type only, possessing elongated, or flattened, presynaptic vesicles approximately 200 Å in diameter and 400–600 Å long. In contrast two distinct types of neuromuscular junctions were observed. The first possesses spherical synaptic vesicles 500–900 Å in diameter. The second possesses synaptic vesicles of dimensions similar to those of axo‐dendritic synapses. It is suggested that synapses, both axo‐dendritic and neuromuscular, with elongated or flattened vesicles, are inhibitory, and that neuromuscular junctions with spherical vesicles are excitatory.
The neural structure of Clarke's nucleus of the spinal cord,
Authors: Boehme Cameron Catlin
Published: January 2005

The neural elements of Clarke's nucleus stained by the Golgi method have been studied in the cat. Three types of cells are found: (1) large bodied cells with many dendrites and (2) small bodied cells with few dendrites. The dendritic arborizations of both types extend mainly in a longitudinal direction, remaining within the nucleus and spreading as far as one millimeter. (3) Large bodied cells are found which have, in addition to a longitudinally directed arborization in the nucleus, branches extending ventrally into the intermediate nucleus. In the nucleus are found dendrites of cells which lie outside it at the base of the dorsal horn and in the intermediate nucleus.

Three sources of afferents to Clarke's nucleus are confirmed: (1) dorsal column collaterals which terminate in the nucleus as longitudinally running knobbed fibrils, (2) lateral column collaterals terminating in small end‐feet and (3) heavy caliber endogenous fibers, some or all of which are axons of cells located in the base of the dorsal horn, and which terminate as fine fibrils in small end‐feet. Some dorsal column collaterals to Clarke's nucleus have terminal branches in the base of the dorsal horn as well. It is confirmed that small synaptic knobs such as those from lateral column collaterals and from heavy caliber endogenous fibers contact the bodies of cells in Clarke's nucleus. The large knobs from dorsal column collaterals are found contacting dendrites.
Avian nucleus isthmi and its relation to hippus
Authors: Showers Mary Jane C. , Lyons Patricia
Published: January 2005

The normal cytology and connections of the mesencephalic nucleus isthmi were examined in cell and fiber preparations of the brains of seven avian forms which included those of chicken, guinea hen, duck, ibis, turkey buzzard, pheasant and sparrow. In all these forms the isthmi complex consisted of three parts which appeared to be associated by position, connections and function. The magnocellular part begins at the region of junction of the diencephalon and the mesencephalon and lies ventral to the nucleus mesencephalicus lateralis pars dorsalis. The parvocellular portion of the nucleus isthmi is the largest subdivision of the complex. It appears and disappears within the rostrocaudal extent of the magnocellular portion of the nucleus. The third, most posterior, and most diminutive division of the nucleus isthmi is the nucleus semilunaris. The above description excludes the nucleus isthmo‐opticus as a representative of the nucleus isthmi. Connections of the isthmi complex, as assayed from normal and experimental methods, include the lateral lemniscus, the tectoisthmal, the isthmotectal, the isthmocerebellar, the isthmo‐oculomotor and the isthmostriatal pathways. Anatomicophysiologic investigation of the nucleus isthmi further supports its homology with scattered reticular cells along the lateral lemniscus in mammals rather than with the medial geniculate nucleus of mammals. The presence of the avian hippus might provide a useful investigative tool.
Studies on the developing cerebellums. Ultrastructure of the growth cones
Authors: Del Cerro Manuel P. , Snider Ray S. , Oster M. L.
Published: January 2005

The fine structure of the cerebellar cortex in rats was examined between the first and forty‐fifth post‐natal day. The formation and growth of axon and dendrites are reported here. As inferred from these observations, the process starts under the cell membrane as a local accumulation of vesicles without any visible content, about 1,100 Å in size. This is followed by an outward bulging of the membrane which then becomes filled with vesicles and is known as the primary growth cone. In axons the synaptic and growth cone vesicles coexist until the third week or longer. In dendrites secondary growth cones exist at the tip of the branching dendrites and spines. Variations in the shape of the growth cone vesicles related to the age of the animal are described, and the importance of attempting to isolate the growth cones and the vesicles is emphasized.
The basilar pontine gray of the opossum (Didelphis virginiana). II. Experimental determination of neocortical input
Authors: Martin George F. , King James S.
Published: January 2005

The pattern of neocortical input into the basilar pons of the opossum was determined by employing the Nauta‐Gygax technique ('54) on the brains of animals previously subjected to neocortical lesions. The results indicate that every neocortical area projects to some portion of the basilar pons in this form. Degenerating fibers resulting from more rostral cortical lesions (frontal and preorbital areas) terminated profusely within the medial and ventral nuclei and, to a lesser extent, in the smaller dorsal nucleus. Fascicles from more caudal areas (striate and peristriate cortices) ended abundantly in the lateral nuclear group, and in the lateral part of the ventral nucleus. Every neocortical region studied projected to some portion of the ventral pontine nucleus. Degenerating fibers terminated to some extent within each nucleus of the basilar pons as a result of lesions in midcortical regions (paramarginal, postorbital and parietal cortices). A few fibers of frontal, orbital and parietal origin terminated in the contralateral basilar pontine gray.
Projections from the orbital gyrus in the cat. I. To brain stem structures
Authors: Mizuno Noboru , Sauerland Eberhardt K. , Clemente Carmine D.
Published: January 2005

Direct projections from the anterior part of the orbital gyrus and its immediate vicinity to the brain stem in the cat were investigated by means of the Nauta and Marchi methods. These experiments were carried out in an attempt to identify the anatomical substrates subserving orbital‐gyral inhibitory influences on somatic reflexes.

The cortical layers of the anterior orbital gyrus and the immediately surrounding cortex were ablated unilaterally. Preterminal degeneration was found bilaterally in the spinal trigeminal nucleus. The most consoicuous degeneration occurred in the interpoler nuclei, caudal parts of the oral nuclei, and rostral portions of the caudal nuclei of the spinal trigeminal complex. Thus, degeneration was found in the trigeminal sensory nucleus from the level of the inferior olive rostrally to levels just caudal to the obex. Preterminal degeneration was also observed bilaterally in the mesencephalic reticular formation. Heavy preterminal degeneration was found in the reticular formation of the rostral midbrain and moderate degeneration was observed in the caudal mesencephalic reticular formation, the pontile reticular substance and medullary reticular nuclei.

Based on these findings, the possible pathways involved in the mediation of orbital‐cortically induced inhibition on somatic reflexes were discussed.
Development of the sensory component of the respiratory mechanism of the toadfish (Opsanus tau)
Authors: Carroll Tracy Henry , Hogg Ira D.
Published: January 2005

This communication deals chiefly with the development of the sensory nerves that supply the portion of the head involved in respiration. It is a supplement to a previous paper (Tracy,′61) and describes in detail the origin of cells that form the sensory ganglia of four cranial nerves, V. VII, IX and X, together with their distribution, the branches that degenerate, motor distribution, and the time at which evidence of first motor movements controlled by them appears. It covers the details concerning the position of placodes which are the source of some of the cells from which the ganglia of these nerves are derived and the relative time at which they appear.

In this article more emphasis is placed on the development of cranial nerves V and VII than on IX and X. Apparently the former two nerves are more involved in the mechanism of respiration than the latter two.

Some incidental observations of importance are recorded that do not appear to bear particularly on the main thesis of the article. One of these concerns the paths of migration followed by the ectomesenchyme. Another statement is to the effect that the two kinds of mesenchyme do not mix but that a quite definite boundary region can usually be distinguished between them as if the process of differentiation has made them slightly incompatible.
Motor nerve endings in extraocular muscles
Authors: Namba Tatsuji , Nakamura Toshio , Takahashi Akira , Grob David
Published: January 2005

In rat extraocular muscles, “en plaque” motor endings with subsynaptic folds were mainly localized at the terminal innervation band, and were present singly in muscle fibers having “Fidrillenstrucktur” and diameters of 18 to 30 μ. The “en grappe” motor endings without subsynaptic folds were found in the proximal and distal thirds of four rectus and two oblique muscles, and 10 to 16 endings were present in muscle fibers having “Felderstruktur” and diameters of 6 to 13 μ. The mean diameter of “en plaque” endings was 31.5 μ in the levator palpebrae and 32.1 μ in the rectus superior, which is larger compared with 27.1 μ in the tibialis anterior. The mean diameter of “en grappe” endings of the superior rectus muscle was 10.0 μ. The mean diameter of muscle fibers was 18.2 μ in the levator palpebrae, 18.5 μ in the superior rectus, and 33.1 μ in the tibialis anterior.
Retrohippocampal, hippocampal and related structures of the forebrain in the reeler mutant mouse
Authors: Caviness V. S. , Sidman R. L.
Published: January 2005

Retrohippocampal, hippocampal and some related forebrain regions of the reeler mutant mouse were examined in cresyl violet and myelin stained preparations. All cortical structures are abnormal. The entorhinal cortex, parasubiculum, presubiculum, subiculum, and anterior hippocampal cortex share an anomaly of common quality. All lack an external plexiform layer and their neurons are not arranged in the usual laminae. The positions of neurons are not random, however. Cells of smaller average size and of polymorphic shape are grouped in an outer relatively narrow zone external to a broad zone of larger cells. The histological features of these two cell zones in the mutant are similar to the deep polymorphic cell stratum and the superjacent pyramidal field respectively in the normal animal, but their relative depths in the cortex are reversed. The histological pattern of the mutant hippocampus is less disturbed. Its external plexiform layer is well developed and, although the positions of some neurons are abnormal, there is an explicit laminar pattern and the cytological features of the individual hippocampal cytoarchitectonic fields are readily recognized.

It appears from these observations that in a variety of cortical structures, even those which are most disturbed, the positions of neurons are systematically regulated, yet are controlled according to some rule that differs in normal and mutant. The basic developmental event which dictates eventual neuron position probably occurs early and its effects may depend on critical timing or precise location of interacting cells as influenced by the reeler locus.
An ultrastructural analysis of the photoreceptors of the squid and their synaptic connections. III. Photoreceptor terminations in the optic lobes
Authors: Cohen Adolph I.
Published: January 2005

An ultrastructural investigation of the optic lobe of the squid, Loligo pealei, revealed that the optic fibers, like those of Octopus, terminated in the outer plexiform layer in long carrot‐shaped bags containing small clear vesicles. The outer 4–5 μ of a terminal was devoid of conventional synapses but came into direct contiguity and specialized contacts with adjacent terminals. These specializations often included protrusions of finger‐like processes from one cell into another. At contact sites the intercellular space narrowed to a minimum of about 25 Å and immediately adjacent, in the cytoplasm of each contacting cell, was a sub‐membranal cistern. These contacts could be electrotonic junctions. The remainder of the receptor terminal received dendritic endings of post‐synaptic cells in deep invaginations. A pre‐synaptic accumulation of vesicles and increased membrane density was evident at these junctions. Neurons of the outer nuclear layer are described, as well as vertical fascicles of large pale neurites which pass through the outer nuclear and plexiform layers and which may include efferents to the retina. Specialized glial cells and a dense, intercellular material located in pools or clefts in certain regions of the cortex of the lobe are also noted.
The projection of nucleus lateralis dorsalis of monkey to basomedial temporal cortex
Authors: Locke Simeon , Kerr Clare
Published: January 2005

Retrograde degeneration in thalamus was studied in eight Macaque monkeys following resection of basomedial temporal cortex. In addition to its known projection to the posterior cingulate region, nucleus lateralis dorsalis (LD) projects, perhaps via the fornix, to the parahippocampal gyrus. Convexal temporal neocortex receives fibers from the medial pulvinar (PM). Nucleus lateralis posterior (LP) may project to cortex intervening between the projection fields for LD and PM. A stereotactic lesion in fornix of one animal demonstrates corticothalamic projection to LD, LP and to a lesser extent to PM, AV, AM, and AD.
The topographic organization of spinal afferents to the lateral reticular nucleus of the cat
Authors: Künzle Heinz
Published: January 2005

The topographic organization of spinal afferents to the lateral reticular nucleus (LRN) has been reexamined in 34 adult cats. Two modifications of the Nauta technique were used to show secondary terminal degeneration resulting from circumscribed lesions at various levels of the spinal cord. The results demonstrate that the “inner segment” of LRN corresponding roughly to Brodal's magnocellular portion, receives fibers from spinal segments C1–D3, while the “outer segment” corresponding approximately to Brodal's parvocellular protion receives fibers from spinal levels below L3. The “middle segment” — a transitional zone between the two former portions — represents the spinal segments D4–L3. The ascending fibers terminate predominantly on the ipsilateral side; only few degenerated elements are noted within the contralateral nucleus. The subtrigeminal portion does not seem to receive afferent fibers from the spinal cord. This finding raises the question of nomenclature, which is briefly discussed in the light of the classical “nucleus funiculi lateralis” concept. Finally, the present data are consistent with electrophysiological data of Oscarsson, Rosén and collaborators according to which LRN represents spinal levels of convergent inputs from large as well as bilateral receptive fields rather than somatotopically arranged projections from peripheral sense organs.