bluuebunny/crossref_metadata_2025 huggingface dataset:
Prenatal development of the cerebellar system in the rat. I. Cytogenesis and histogenesis of the deep nuclei and the cortex of the cerebellum
Authors: Altman Joseph , Bayer Shirley A.
Published: May 2005

Prenatal cerebellar development was investigated with three approaches. In normal embryos sectioned in three planes morphological and cytological changes were determined at daily intervals beginning on embryonic day 13 (E13). A similar series of X‐irradiated embryos was used to study changes in neuroepithelial organization and in the location of primitive (radiosensitive) or differentiated cells. Finally, to quantify the time of origin of different classes of cerebellar neurons with the progressively delayed labelling procedure, we used autoradiograms from adult rats whose mothers were injected with two successive daily doses of 3H‐thymidine on overlapping days from day E13 on.

The cerebellar anlage was delineated in the dorsal metencephalon by the collapse of its ventricular lining after X‐irradiation. This “collapsing neuroepithelium” was located laterally on day E13, then it spread medially and reached the midline on day E16. Deep nuclear neurons began to differentiate on day E13, with two‐thirds forming on day E14; Purkinje cell formation peaked on day E15, with a few cells still forming on day E16. It was postulated that the deep nuclear neurons settled first in the superficial “nuclear zone,” and that the Purkinje cells gathered temporarily in the underlying “transitory zone,” adjacent to the collapsing neuroepithelium.

In the next period of cerebellar development four major events were recognized. (1) Beginning on day E17 the cells of the nuclear and transitory zones became intermingled. It was postulated that the Purkinje cells were migrating radially through the ranks of the stationary deep nuclear neurons and assembled under the spreading canopy of a fibrous plexus and the external germinal layer. (2) It was also on day E17 that the external germinal layer began to form as one of the prongs of the “germinal trigone” in the posteroventral aspect of the cerebellum. On the succeeding days the external germinal layer spread over the surface of the cerebellum; in the vermis in a rostral direction. (3) Two cell types destined to settle in the future granular layer, the pale cells and the Golgi cells, began to form at a relatively slow rate on day E19. Chronological considerations suggested that they were generated in the regressing, noncollapsing neuroepithelium of the cerebellar ventricle. (4) From the beginning (day E17) of its genesis posteroventrally, the primitive cerebellar cortex bridged the midline. As the fused cortex spread rostrally, the vertical ventricular cleft separating the underlying portions of the cerebellum became shallower and then disappeared; the process was completed in the anterior cerebellum by day E22. By the time of birth the maturation of the neurons of the deep nuclei appeared advanced but the maturation of the prenatally produced neurons of the cortex does not start until after birth when a new class of neurons is generated in the external germinal layer.
The neurons in the gelatinosal complex (laminae II and III) of the monkey (Macaca mulatta): A golgi study
Authors: Beal John A. , Cooper Margaret H.
Published: May 2005

The nerve cells of the gelatinosal complex (laminae II and III) were examined in various planes of section in Golgi and Nissl preparations of the lumbosacral spinal cord of the adult monkey. An attempt was made to characterize the neurons based on morphological variations and establish criteria for consolidation or separation of laminae II and III. In Nissl preparations the laminae essentially conform to Rexed's ('52) description for the cat. In Golgi preparations impregnated neurons of the gelatinosal complex show a spectrum of morphological variation. These variations, however, are not restricted by Rexed's border between laminae II and III. In either lamina the cells vary in size from small (12 µm × 8 µm) to medium (30 µm × 25 µm) and in shape from fusiform to polygonal. Polygonal neurons are prevalent in the dorsal part of lamina II (Rexed's outer zone) and some have craggy contours.

Axons of the cells of the gelatinosal complex vary in diameter, but most measure around 1.0 µm with some up to 2.0 µm. Their course is often a meandering one which cannot be followed. Those from cells in the outer zone of lamina II are different. They issue collaterals to lamina I then immediately enter the overlying white matter. Golgi type II (short axoned) cells were not definitively demonstrated. Nonetheless, the neurons of the gelationosal complex display stalked dendritic appendages and axon‐like processes which are similar to those described on Golgi type II interneurons elsewhere in the central nervous system. For this reason, in spite of the long axons and relatively large dimensions of the neurons of the gelationosal complex, their circuitry is suspected to be similar to that of local circuit interneurons.

The dendritic arbor of the cells of the gelatinosal complex, as viewed in horizontal sections, generally extends longitudinally with little mediolateral spread. In sagittal sections a stratified pattern of dendritic arborization divides the gelatinosal complex into three regions: (1) an outer region which corresponds to Rexed's ('52) outer zone of lamina II, (2) a middle region composed of the remainder of lamina II and the dorsal portion of lamina III, and (3) an inner region or ventral part of lamina III. A large portion of the dendritic arbors of cells in the outer region spread ventrally at oblique angles while those from the inner region spread dorsally. Dendrites arising from cells in the middle region, on the other hand, extend almost exclusively in the longitudinal plane, are often of considerable lengths, and give rise to unique recurrent branches. The dendritic arborization is discussed in relation to the primary afferents to the gelatinosal complex.
The sensory trigeminal system of a snake in the possession of infrared receptors. I. The sensory trigeminal nuclei
Authors: Molenaar Gerard J.
Published: May 2005

This study was undertaken to examine the relation between the possession of the so‐called pit organs, which are sensitive infrared receptors innervated by the trigeminal nerve, and the sensory trigeminal nuclei. The sensory trigeminal system of Python reticulatus was investigated by means of myelin and Nissl staining techniques.

It appears from the study that the sensory trigeminal system consists of two separate components. One of these resembles the sensory trigeminal system, known of other vertebrates, and is referred to as the common sensory trigeminal system. It comprises a short ascending part to the principal sensory trigeminal nucleus and a longer descending part to the nucleus of the descending trigeminal tract and upper cervical segments. The subdivision of the trigeminal system, as proposed by Olszewski ('50) for mammals, could be applied to the common sensory trigeminal system of the python.

The second component is situated laterally to the common descending system. It is composed of descending fibres which terminate in a huge, separate nucleus. This is called the nucleus of the lateral descending trigeminal tract. This component was initially recognized in snakes possessing infrared receptors, but seems not to be restricted to these animals.
Golgi‐staining of “primary” and “secondary” motoneurons in the developing spinal cord of an amphibian
Authors: Blight Andrew R.
Published: May 2005

The Golgi technique was used to study the morphology of spinal motoneurons at various stages in the early development of swimming behavior in embryos and larvae of the palmate newt, Triturus helveticus (Razoumowsky). The earliest motoneurons stained appeared to be Associated with the Mauthner‐cell system. The overall morphology of these “primary” motoneurons seems to be similar throughout the lower vertebrates and the distinctive characteristics found in earlier descriptions of those from caudate amphibia were probably due to misinterpretation. At about the time of hatching and the development of low‐frequency swimming behaviour, other motoneurons were found to innervate the axial musculature, cells with a central morphology different from those of the “primary” type. It was found likely that these “secondary” motoneurons innervate a separate muscle system concerned with tonic and “slow phasic” activity, while “fast phasic” activity in rapid swimming is supplied by “primary” cells.
Gustatory pathways in the bullhead catfish. II. Facial lobe connections
Authors: Finger Thomas E.
Published: May 2005

The second order projections of the gustatory system in catfish were examined using both retrograde (HRP) and anterograde (degeneration and autoradiographic) hodological methods. Golgi‐stained material was used to demonstrate the different cell types in the primary gustatory sensory area, the facial lobe.

Efferents from the facial lobe gather into ascending tract terminates largely in the medial funicular nucleus and the commissural nucleus of Cajal in the region of the obex. A small portion of the descending tract continues caudally to terminate in the dorsal horn of the spinal cord. The ascending secondary gustatory tract terminates mostly in the ipsilateral superior secondary gustatory nucleus in terminate in the isthmic region. A small portion of the ascending tract continues rostrally to terminate in the posterior thalamic nucleus and in the region of the nucleus lobo‐bulbaris. Sparser contralateral projections are also seen in the posterior thalamus and isthmic gustatory regions.

Three cell types can be discerned in the facial lobe: small, medium and large. The small cells are intrinsic neurons, the medium cells project to the isthmic gustatory nucleus, and the large cells send fibers to the other terminal areas described above, as summarized in figure 19.
Internal organization of membranes at end bulbs of held in the anteroventral cochlear nucleus
Authors: Gulley R. L. , Landis D. M. D. , Reese T. S.
Published: May 2005

The end bulb of Held in the rostral ventral cochlear nucleus of the chinchilla and guinea pig was studied with the freeze‐fracture technique. The end bulb has multiple, small active zones which are uniformly distributed within the calyceal portion of this terminal. Single or small groups of active zones are surrounded by enlarged channels of extracellular space often containing processes of astrocytes. Small plasmalemmal deformations occur at these active zones. The number of these deformations is thought to be indicative of exocytotic transmitter release because they are more frequent in animals fixed in a noisy environment compared to animals fixed in a quiet environment. Thus, our study provides a basis for the quantitative study of changes in transmitter secretion at a central nervous system synapse driven by a controllable natural stimulus.

The postsynaptic active zone at end bulbs resembles other excitatory synapses in the central nervous system in having an aggregate of large particles on the external membrane leaflet. This junctional aggregate of particles is coextensive with the presynaptic active zone and with the postsynaptic density seen in thin sections. Several perisynaptic aggregates of particles are deployed around each active zone on the external membrane leaflet. These irregularly‐shaped aggregates occur preferentially opposite the channels of enlarged extracellular space and along the edge of the end bulb and are not components of intercellular junctions or plasmalemmal contacts with cytoplasmic organelles. Although the function of the different particle aggregates on the postsynaptic membrane is not clear, our findings provide a basis for studying the factors controlling and maintaining their structure as well as more evidence that a consistent relationship exists between types of synaptic action and structure of the postsynaptic membrane.
Sites of termination of the saccular macula of auditory nerve fibers in the goldfish as determined by intracellular injection of procion yellow
Authors: Furukawa Taro
Published: May 2005

Procion yellow dye was injected intracellularly into large auditory fiber of goldfish to investigate the relationship between the response type of these fiber and their site of termination in the saccular macula.

Fibers which responded to the rarefaction phases of sound were found to terminate on the hair cells located in the ventral half of the saccular macula, while those which responded to the compression phases were found to terminate on the dorsally locate hair cells. A third group of fibers, which responded to both sound phases, was found to bifurcate outside the saccular macula and terminate on both dorsally and ventrally located hair cells. Some of the fibers of this group were found to trifurcate before entering the sacular macula. Results obtained in the present study, in conjunction with the findings on the orientation of hair cells within the sensory macula, can explain the mechanism underlying the presence of three different response types of fibers in the auditory nerve of the goldfish.
Reconstruction of trajectory of primary afferent collaterals in the dorsal horn of the cat spinal cord, using golgi‐stained serial sections
Authors: Hamano Kenzo , Mannen Hajime , Ishizuka Norio
Published: May 2005

Using Golgi‐stained serial sections obtained at the sacro‐caudal levels of the cat spinal cord, it was possible to reconstruct the trajectory of primary afferents. They were classified into two groups: reliable primary afferents directly traced from the dorsal root and probable primary afferents traced from the dorsal funiculus or Lissauer's tract.

The diameters of the reliable primary afferents vary from 0.88–1.88 μm. According to their courses, reliable primary afferents as well as probable primary afferents were classified into three groups: the first is distributed to both medial and lateral halves of the dorsal horn, the second to the medial half, and the third to the lateral half. Commissural fibers were also observed among the probable primary afferents. The rostro‐caudal and medio‐lateral extents of reliable primary afferents are found to be between 250 and 950 μm and 270 and 700 μm respectively, while those of the probable primary afferents were between 125 and 670 μm and 270 and 1,640 μm respectively. These primary afferent fibers are connected with at least two or more laminae of the dorsal horn gray matter.
The distribution and orientation of noradrenergic fibers in neocortex of the rat: An immunofluorescence study
Authors: Morrison John H. , Grzanna Reinhard , Molliver Mark E. , Coyle Joseph T.
Published: May 2005

A homologous antiserum directed against rat dopamine‐β‐hydroxylase (DBH) was employed in the indirect immunofluorescence technique of Coons ('58) to describe the distribution and orientation of noradrenergic (NA) axons in the cerebral neocortex of the adult albino rat. DBH is the terminal enzyme in the biosynthesis of noradrenaline and is a sensitive anatomic marker for NA neurons and their processes. Cryostat sections in three standard planes (coronal, sagittal and tangential) taken from four cortical fields (somatosensory, motor, visual and anterior cingulate) were processed for immunofluorescence, and adjacent sections were stained with a Nissl method to relate the pattern of NA axons to specific cortical laminae. Noradrenaline levels and DBH activity were measured in the same cortical fields by radioenzymatic assays.

A rich network of DBH immunoreactive axons was observed throughout all cortical layers in each of the areas examined. The pattern of NA distribution is not diffuse, but is characterized by a geometric orderliness that is uniform throughout the neocortex, with only minor regional variations. In layer I the DBH‐positive fibers are predominantly parallel to the pial surface and thus form a tangential grid‐like pattern. Layers II and III are characterized by straight, radial fibers that rarely extend through layer IV to the infragranular layers. There appears to be a NA terminal field in layers IV and V where there is a network of short, oblique or tortuous axon segments, especially prominent in lateral neocortex. Layer VI is unique in that the prevailing orientation of NA fibers is in the anterior‐posterior direction. This band of fibers does not extend into the sub‐cortical white matter, where very few NA fibers are seen. The strong tangential projection of the NA neurons, particularly in layers I and VI, emerges as a dominant feature of this afferent system and appears to be superimposed on the predominantly vertical organization of the cortex. This tangential pattern of organization may allow the locus coeruleus to modulate the activity of adjacent columns synchronously over a vast expanse of cerebral cortex.
Effect of neonatal deafferentation on synaptogenesis in the rat interpeduncular nucleus
Authors: Lenn Nicholas J.
Published: May 2005

Changes in the normal synaptogenetic pattern of the interpeduncular nucleus (IPN) were induced by destruction of one or both habenular nuclei in neonatal rats. The S synapses, the principal habenulointerpeduncular (H‐IPN) afferents, were reduced in number and delayed in time of appearance by unilateral lesions. They were eliminated by bilateral lesions. The crest synapses, also of habenular origin, appeared at ten days of age and were apparently normal in structure after unilateral lesions. However, this actually represented a change in connectivity, since normal crest synapses are of bilateral origin. Following bilateral habenular lesions abnormal crest synapses appeared at 28 days of age. These had normal postsynaptic structure, but presynaptically were formed by non‐habenular axons, usually of two different types at each crest synapse. Lesions induced an early appearance of F synapses, at three days, instead of the normal time after six days of age. Apparently similar processes containing flattened vesicles formed somatic contacts only in lesioned animals beginning at 21 days of age. The axosomatic synapses which were only occasional appeared in the adult appeared at the normal time in lesioned animals. At 28 days of age in both unilaterally and bilaterally lesioned animals these was an increase in number of somatic synapses. This increase was due to an increase of the normal somatic endings plus the appearance of somatic synapses containing flattened vesicles. Both types of somatic contacts were found in similar numbers at subsequent ages up to three months.

The changes in S synapses represent Wallerian degeneration. The formation of unilaterally derived crest synapses in unilaterally lesioned animals is interpreted as evidence for a specific recognition mechanism. A postsynaptic control mechanism is proposed to explain the formation of heterologous crest synapses, with the usual distinctive geometry but involving abnormal, non‐habenular presynaptic elements four weeks following neonatal bilateral lesions. The increase in axosomatic synapses is unusual since the dendrites of IPN neurons were deafferented, not their somata. The factors leading to the changes in somatic synapses are discussed. The findings reveal new examples of the complexity of neuronal adaptation to CNS lesions in early life.
Cerebellar afferents in teleost catfish (lctaluridae)
Authors: Finger Thomas E.
Published: May 2005

The cerebellar afferents in the bullhead catfish (Teleostei) were labeled by relying on the retrograde transport of horseradish peroxidase (HRP). Retrogradely labeled neurons were seen in: spinal cord, lateral cuneate nucleus, inferior olive, reticular nuclei, vestibular nuclei, nucleus subeminentialis, n. lateralis valvulae, locus coeruleus, n. mesencephalicus dorsalis, the basal optic nuclei, and a nucleus at the isthmic level which may be equivalent to the pontine nuclei of birds and mammals. Inputs to the molecular layer arise from the inferior olive, locus coeruleus and n. lateralis valvulae in addition to subjacent granule cells.

No projections to cerebellum were seen to arise from either the optic tectum or from the inferior lobe. The so‐called “lobo‐cerebellar” tract in teleosts was reported by Goldstein, amongst many others, who mistook the superior secondary nucleus for a deep cerebellar nucleus.
Myelin sheath thickness and conduction latency groups in the cat optic nerve
Authors: Freeman Brian
Published: May 2005

In many animals, the optic nerve has multiple conduction latency groups of fibres yet displays a unimodal frequency distribution of fibre sizes. An attempt has been made to resolve this discrepancy in the cat.

Examination of teased preparations of fixed cat optic nerve fibres by polarizing interference light microscopy indicated that a fiber's size may change abruptly along its length. Furthermore, the diameters of single nerve fibres followed for distances of up to 30 μm in serial transverse sections of cat optic nerve showed variations of up to 100% of a fibre's average diameter over that distance. On the other hand, the myelin sheath thickness of these fibres appeared to be relatively constant along any one fibres.

A population of cat optic nerve fibres which had a unimodal axon diameter frequency distribution was found to have a myelin sheath thickness frequency distribution with five modes. These modes have been interpreted as indicating the existence of five groups of fibres in the cat optic nerve. Four of these groups may be related to four negative peaks seen in the antidromic compound action potential recorded at the margin of the cat optic disc following stimulation of the optic chiasm. The fifth myelin thickness group appears to represent the slowly conducting fibres which do not make an obvious contribution to the antidromic compound action potential.

It is concluded that for the cat optic nerve, the conclusion latency groups seen in the compound action potential may be more directly correlated with the frequency distribution of fixed nerve myelin thickness than with the frequency distribution of fixed nerve fibre diameter.
The afferent connections of the main and the accessory olfactory bulb formations in the rat: An experimental HRP‐study
Authors: de Olmos Jose , Hardy Hay , Heimer Lennart
Published: May 2005

The afferent connections of the main and accessory olfactory bulbs in the rat were examined by injecting horseradish peroxidase (HRP) into one or the other of these structures either by microelectrophoresis or by hydraulic pressure. Alternate sections were stained with newly developed HRP‐procedures using either benzidine dihydrochloride (de Olmos and Heimer, '77) or tetramethyl‐benzidine.

Eighteen to twenty‐four hours after unilateral HRP injections confined to the main olfactory bulb, a large number of HRP‐labeled perikaria appeared in the following telencephalic structures on the ipsilateral side: All portions of the anterior olfactory nucleus (AON) except its external part, the lateral transitional field (LT) between AON and the paleocortex, the whole extent of the primary olfactory cortex (POC); The medial forebrain bundle area deep to the olfactory tubercle, the nucleus of the horizontal limb of the diagonal band (NHDB) and the nucleus of the lateral olfactory tract (NLOT). A moderate to small number of labeled cells, furthermore, were seen in the dorsal (DT) and medial (MT) transition fields, the ventral praecommissural hippocampus (tt2), the ventral superficial part of the nucleus of the vertical limb of the diagonal band (NVDB), the sublenticular part of the substantia innominata (SI), the anterior amygdaloid area, the posterolateral cortical amygdaloid nucleus (C2) and the transition region (28 L') between the olfactory cortex and the lateral entorhinal area proper. On the contralateral side a large number of labeled cells were found in all parts of the AON, with especially heavy labeling in its external part. A moderate number of labeled cells could also be detected in the lateral transition field (LT) and the NLOT.

In the diencephalon and the brain stem a moderate number of HRP‐labeled perikaria were observed in the dorsal, perifornical, and lateral hypothalamus, as well as in locus coeruleus and the dorsal and medial raphae nuclei.

Following large HRP injections in the main olfactory bulb a moderate to small number of labeled cells were seen also in the posterior and premammillary hypothalamus and in field CA1 of the retrocommissural hippocampus on the ipsilateral side, as well as in POC on the contralateral side. It is possible, however, that the uptake of label took place in an undetected pool of HRP in the very rostral part of AON rather than in the olfactory bulb.

HRP injections in the accessory olfactory bulb resulted in labeled neurons in the posterior ventro‐lateral part of the bed nucleus of the stria terminalis, the nucleus of the accessory olfactory tract, the rostrodorsal portions of the medial amygdaloid nucleus, and whole extent of the posteromedial cortical amygdaloid nucleus (C3) on the ipsilateral side. A few lightly labeled cells were seen also in the contralateral C3.
An autoradiographic study of the commissural and ipsilateral hippocampo‐dentate projections in the adult rat
Authors: Fricke R. , Cowan W. M.
Published: May 2005

The distribution of the associational and commissural afferents to the inner one‐fourth of the molecular layer of the dentate gyrus of the rat, has been studied autoradiographically following small injections of 3H‐proline into the hilar region of the dentate (from which both groups of afferents arise). Different patterns of axonal labeling are observed after injections into the temporal (i.e., caudal), middle, or septal (rostral) thirds of the hippocampus. Thus after temporal injections labeled commissural and associational afferents are found only in the caudal third of the dentate gyrus, and the grain densities observed on the two sides are markedly asymmetrical around the short, or transverse, axis of the dentate. On the other hand, injections into the middle third of the hippocampus lead to extensive labeling of the commissural and associational afferents throughout the rostral two‐thirds of the dentate gyrus, and their distribution, as judged by grain density estimates, is symmetrical on the two sides. Septal injections label fibers over the rostral half of the dentate, and again the labeling pattern of the two sides is asymmetrical (but in the reverse pattern from that seen after temporal injections).

These distinctive patterns in the distribution of the two classes of afferents can generally be accounted for on the following assumptions: (1) the commissural and associational afferents share a common cytochemical specificity; (2) they compete with each other for the limited number of synaptic sites available upon the proximal portions of the granule cells; (3) the granule cells are generated along two distinct morphogenetic gradients: from the temporal to the septal pole of the dentate gyrus, and from the tip of its dorsal (or external) to the tip of its ventral (internal) blade; and (4) the first fibers to arrive monopolize the majority of the available synaptic sites, and those that reach their target field later, synapse predominantly upon the last‐formed granule cell dendrites. To this extent our findings are consonant with the “temporal hypothesis” first formulated by Gottlieb and Cowan ('72). However, to account for the restricted distribution of afferents from the temporal part of the hippocampus, it is necessary to further postulate that there is some degree of topographic (or region‐to‐region) specificity in the ipsilateral and contralateral hippocampodentate projections.
Categories of axons in mammalian rami communicantes, Part II
Authors: Coggeshall Richard E. , Galbraith Samuel L.
Published: May 2005

The Mammalian rami communicantes consist of preganglionic, postganglionic and sensory axons. The present study focusses on the number of sensory axons in the midthoracic rami communicantes in the cat. The conclusions are that the white rami contain approximately 250 myelinated and 200 unmyelinated sensory axons and the grey rami 4 to 5 myelinated and 20 to 25 unmyelinated sensory axons. A previous study determined the numbers of pre‐ and postganglionic fibers in these same rami. Thus the total number of axons in these rami are as follows: for the grey rami there are: (1) 3,000 to 5,000 unmyelinated postganglionic axons, (2) 25 myelinated postganglionic axons, (3) 20 to 25 unmyelinated sensory axons and; (4) 4 to 5 myelinated sensory axons; and for the white rami there are approximately: (1) 1,000 unmyelinated preganglionic axons, (2) 1,500 myelinated preganglionic axons, (3) 2,000 unmyelinated postganglionic axons, (4) 250 unmyelinated sensory axons and (5) 200 myelinated sensory axons. The implications of these findings are discussed.
The ultrastructure of the basilar papilla of the chick
Authors: Hirokawa Nobutaka
Published: May 2005

The basilar papilla of the chicken was studied by transmission and scanning electron microscopy. It is composed of two distinct types of hair cells, a tall hair cell (THC) and a short hair cell (SHC). Gradual transitions exist between these two forms. The THC occurs mainly in the anterior part of the neuroepithelium and is situated on the superior fibro‐cartilagenous plate, while the SHC dominates in the posterior part and is found on the free basilar membrane. The THC is a tall columnar cell with an elongated hexagonal apical surface. One kinocilium and 150 to 220 stereocilia protrude from the center of its surface. The THC makes synaptic contact with several large afferent nerve terminals and with small bouton‐shaped efferent terminals. The SHC is short and thick, having a much wider surface area than the THC. From the inferior part of the surface of the SHC 90 to 120 stereocilia protrude, whereas the kinocilium is lacking. The nucleus is located near the base of the cell. Small afferent nerve terminals and extremely large efferent nerve endings synapse with the SHC.
Morphological and electrophysiological characteristics of projection neurons in the nucleus interpositus of the cat cerebellum
Authors: McCrea R. A. , Bishop G. A. , Kitai S. T.
Published: May 2005

The populations of neurons in the nucleus interpositus (IP) of the cat cerebellum which project to the ventral lateral nucleus of the thalamus (VL), the red nucleus (RN), the nucleus reticularis tegmenti pontis (NRTP), the pontine nuclei (PN), the inferior olive (IO), and the cerebellar cortex were identified by intracellular and extracellular injections of HRP and studied electrophysiologically.

When HRP was simultaneously injected into the VL, RN, and IO, over 95% of the neurons in the IP nuclei were labeled; indicating that there are few, if any, local circuit neurons. The vast majority (86%) of the larger IP neurons (soma length ≥ 20 μm) project rostrally to the RN and thalamus. These neurons typically have long, relatively spine free dendrites and axons which in a few cases gave rise to recurrent collaterals. Two intracellularly stained projection neurons which had exceptionally long spiny dendrites had axons which gave rise to nucleocortical collaterals in addition to several local collaterals. IP neurons projecting to the NRTP and PN were located primarily in the lateral aspect of the nucleus interpositus anterior. Electrophysiological experiments established that neurons projecting to the NRTP also project to the VL. The IP neurons projecting to the IO have small fusiform or multipolar somata, long thin dendrites, and receive excitatory inputs from the IO. At least 73% of the small neurons in the IP project to the IO, and some of these, in addition, project to the VL.

There are at least three morphologically distinguishable populations of projection neurons in the IP, large VL projection neurons, small IO projection neurons, and neurons with nucleocortical collaterals. The projection of the IP to diverse regions of the brain is accomplished mainly by axon collateralization, but regional and morphological specialization also play a role in the organization of the output of the IP.
Organization of corticocortical connections in the parietal cortex of the rat
Authors: Akers Rebecca M. , Killackey Herbert P.
Published: May 2005

An analysis based on Nissl, anterograde degeneration, and sucinic dehydrogenase histochemical techniques reveals that there are two distinct regions of parietal cortex which are characterized by different cytoarchitectonic features and anatomical connections. The “granular” cortical zone possesses a well‐defined fourth layer composed of small, densely‐packed cells, receives dense projections from the ventral posterior nucleus of the thalamus, and is essentially free of callosal inputs. “Agranular” cortical areas which surround or lie embedded within the granular zone lack a well‐defined fourth layer, receive sparse projection from the ventral posterior nucleus, but send and receive extensive callosal projections. These findings suggest that thalamic and callosal projections to the parietal cortex maintain a pattern of areal segregation. The granular cortical zone, which apparently corresponds to SmI, projects ipsilaterally to motor cortex, SmII, and adjacent agranular areas. The superficial layers of the granular cortex also project heavily upon the underlying layer V. This intracortical projection is not organized in discrete clusters within the “barrel field” cortex. This suggests that the specialized organization of thalamic afferents and granule cells within the “barrel field” is not maintained in the intracortical circuitry of this region.
The hypothalamic magnocellular system of the rhesus monkey: An immunocytochemical study
Authors: Lobo Antunes J. , Zimmerman Earl A.
Published: May 2005

The hypothalamic magnocellular system of the adult female rhesus monkey is studied here, using immunoperoxidase technique and antisera to estrogen stimulated neurophysin (ESN), nicotine stimulated neurophysin (NSN), oxytocin (OT) and vasopressin (VP). These observations confirm and enlarge previous descriptions by others using Gomori techniques.

It is apparent from this study that the magnocellular system spreads through a broader area than is generally accepted. A group of cells ventral to the head of the caudate nucleus and medial to the internal capsule is described.

The general orientation of the nuclei and their tracts can only be appreciated when coronal, horizontal and sagittal sections are compared. Our observations suggest that the supraoptic nucleus is made up of a single group of cells that straddles the optic pathways, and is not divided in three segments, as it is generally described. It is also shown that the rostral extensions of the paraventricular and supraoptic nuclei merge above the optic chiasm.

Cells containing ESN/OT and NSN/VP are evenly dispersed in the paraventricular nucleus but a topographical arrangement is present in the supraoptic nucleus.

The magnocellular nuclei project to the organum vasculosum of the lamina terminalis, zona externa of the median eminence and pars nervosa of the pituitary gland. Reactive fibers were also seen within islets of cells from the pars in termedia located inside the pars nervosa.

A globular structure containing small blood vessels surrounded by positive fibers was noticed protruding into the floor of the third ventricle, at the level of the median eminence.
Identified neurons in mouse smi cortex which are postsynaptic to thalamocortical axon terminals: A combined golgi‐electron microscopic and degeneration study
Authors: White Edward L.
Published: May 2005

A recently developed Golgi‐electron microscopic technique (Fairén et al., '77) has been used to identify neurons in mouse SmI cortex which that thalamic axon terminals synapsed with dendrites of several distinct neuronal types whose cell bodies occurred either in layer III, IV or V. The procedures employed were as follows: electrolytic lesions were used to destroy the cortical projections of the nucleus ventralis posterior pars lateralis thalami (homologous to medial portion of ventrobasal complex) and the nucleus posterior thalami. These two thalamic nuclei project to the posteromedial barrel subfield (PMBSF) in mouse somatosensory cortex. Blocks of cortex containing the PMBSF were processed by the Golgi method, sectioned at 150 μm and examined with the light microscope. Neurons of interest were then selected for Golgi deimpregnation (Fairén et al., '77). Portions of these cells were serial thin sectioned and subsequently examined with the electron microscope to determine if they synapsed with degenerating axon terminals.

Degenerating thalamocortical axon terminals synapsed at asymmetrical synaptic junctions with dendritic spines of pyramidal cells whose somata occurred in layers III and V, and with dendritic spines of spiny stellate cells with somata in layer IV. Only normal, symmetrical synapses occurred on the cell bodies of these neurons, and no degenerating axon terminals synapsed with the shafts of their dendrites. Two, unimpregnated, non‐spiny stellate cells whose somata occurred in layers IV and IV/V were partially reconstructed from serial thin sections. Many degenerating thalamocortical axon terminals synapsed with the dendrites and somata of these non‐spiny cells. In fact, for similar lengths of dendrite, the non‐spiny stellate cells made the most synapses with thalamocortical axon terminals, followed in order of decreasing frequency by the layer IV spiny stellate cells, the layer III pyramids and finally the layer V pyramids which received only few synapses from thalamocortical axon terminals.

Direct evidence has been provided that at least six different types of neurons whose somata occur in several layers of the neocortex receive synapses from thalamocortically projecting neurons. It has been proposed that the cortex is organized such that thalamic input is processed sequentially by neurons of increasingly complex response properties beginning with cells in layer IV and proceeding to cells in other layers (Hubel and Wiesel, '62, '68). The results of this study now suggest that any such hierarchical processing of thalamic input must occur in conjunction with the parallel, and perhaps simultaneous, processing of thalamic input by neurons at several hierarchical levels. The evidence for, and some implications of, a newly proposed model of cortical organization which combines hierarchical and parallel processing are discussed.
Characterization of the monoaminergic innervation of immature rat neocortex: A histofluorescence analysis
Authors: Lidov H. G. W. , Molliver M. E. , Zecevic N. R.
Published: May 2005

In the neocortex of 6‐day‐old rat, abundant axon terminals which exhibit specific catecholamine fluorescence are found in all regions and throughout all cortical layers. The overall density of axons in 6‐day‐old cortex in similar to the density in the adult cortex. In immature cortex, there are two distinct fluorescent plexuses, both presumably noradrenergic, one in the molecular layer and another in the lower half of the cortex. The superficial plexus is composed primarily of horizontal fibers, and the deep plexus of a dense feltwork of obliquely oriented fibers suggestive of a terminal field. The cortical plate itself is traversed by a few vertical processes. Following lesions of the midbrain tegmentum no fluorescent axons are seen in cortex, providing evidence that the fluorescent axons in cortex arise from brain stem neurons. The deep and superficial plexuses can be differentially visualized depending on the histochemical techniques employed and on pharmacological treatment, such as loading with a monoamine congener. Both deep and superficial axons are shown to contain endogenous catecholamines but those fibers in the deep plexus are filled to far less than their maximum capacity. The pharmaco‐histochemical differences between axons in the two plexuses suggest that there may exist two distinct catecholaminergic projections to lateral neocortex. The demonstration of an extensive cortical monoamine innervation early in ontogeny supports the possibility that monoamine neurons play an important role in information processing and/or developmental interactions in the immature brain.
Localization of enkephalin‐like immunoreactivity to identified axonal and neuronal populations of the rat hippocampus
Authors: Gall Christine , Brecha Nicholas , Karten H. J. , Chang Kwen‐Jen
Published: May 2005

The distribution of enkephalin‐like immunoreactivity in the hippocampal formation of the rat was analyzed. Two specific projection systems are described. The first emerges from the hilus of the dentate gyrus and appears to terminate with notably large boutons on the proximal apical and, to a lesser extent, basal dendrites of hippocampal regio inferior pyramidal cells. This projection corresponds in source, position, and character to the hippocampal mossy fiber system. The second axonal population enters the temporal hippocampal formation from the medial wall of the subicular complex and follows the hippocampal fissure to occupy stratum lacunosum‐moleculare of the hippocampus proper and the distal third of the dentate gyrus molecular layer; this pattern corresponds to the distribution of afferent input from the lateral entorhinal cortex and/or perirhinal area. Lesions of the hilus or retrohippocampal area caused a selective depletion of immunoreactivity in the mossy fiber fields and molecular layers of the dentate gyrus, respectively. Enkephalin‐like immunoreactivity was found within the somata of three types of hippocampal neurons: (1) granule cells of the dentate gyrus, (2) occasional pyramidal shaped cells of field CA1 stratum pyramidale, and (3) varied scattered interneurons. Of this last group, two types of interneurons were consistently seen. The first occupy the border between stratum radiatum and stratum lacunosum‐moleculare and extend processes at right angles to the long axis of the pyramidal cell dendrites, whereas the second lie within stratum radiatum of field CA1 and extend processes in alignment with the long axis of the pyramidal cell dendrites. Cells containing enkephalin‐like immunoreacactivity were also observed in the subiculum and retrohippocampal region, most notably including layers II and III of the lateral entorhinal cortex‐perirhinal area—the probable source of extrinsic immunoreactive input to the hippocampal formation. Intraventricular colchicine treatment intensified the immunoreactive staining of some hippocampal neurons but did not reveal any cell types not seen to be labeled in untreated rats.
Sources of descending afferents to the inferior olive from the upper brain stem in the cat as revealed by the retrograde transport of horseradish peroxidase
Authors: Saint‐Cyr Jean A. , Courville Jacques
Published: May 2005

The retrograde transport of horseradish peroxidase (HRP) was employed in 35 cats to trace the sources of descending afferents to the inferior olivary nucleus. The majority of HRP‐labeled cells were located in the ipsilateral mesencephalon, from the rostral pole of the red nucleus to the caudomedial border of the thalamus. Among the heavily labeled nuclear groups were the parvocellular red nucleus, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch, and the caudomedial extremity of the subparafascicular nucleus. Occasional cells were also labeled in the reticular formation lateral to the interstitial nucleus of Cajal, in the caudomedial parafascicular nucleus, in the nucleus of the fields of Forel, and in the centray gray. It was not possible to recognize a topographic distribution of the labeled cells corresponding to the loclization of the HRP deposits. Elsewhere in the midbrain, there were HRP‐labeled cells in the deep layers of the superior colliculus (IV and VI), predominantly on the side contralateral to the injection and in the nucleus of the optic tract, and in the anterior and posterior pretectal nuclei, ipsilaterally. These groups were best labeled after caudally located injections in the olive. Certain areas previously reported to project to the inferior olive were devoid of labeled cells; these included the basal ganglia, the rostral raphe nuclei, and the nucleus of Edinger‐Westphal. It appears that the mesecephalic nuclei bordering the central gray represent the major source of descending afferents to the olive.
Immunohistochemical localization of enkephalin in the central nervous system and pituitary of the lizard, Anolis carolinensis
Authors: Naik Dhruba Raj , Sar Madhabananda , Stumpf Walter E.
Published: May 2005

The topographical distribution of enkephalin in the central nervous system of the lizard, Anolis carolinensis, has been studied by the immunoperoxidase technique with antiserum to leucine‐enkephalin. Immunoreactive enkephalin perikarya, fibers and probably terminals are widely distributed throughout the central nervous system, which agrees well with the distribution of enkephalins in the mammalian brain. Enkephalin‐containing perikarya are found in the subpallium (septum, nucleus accumbens, striatum, amydgala), preoptic and hypothalamic region, ventromedial nucleus and ventromedial area of thalamus, pretectal geniculate nucleus and posterodorsal nucleus of pretectum, nucleus of the lateral lemniscus, locus ceruleus, spinal trigeminal nucleus, nucleus of the solitary tract, medial parvocelluar nucleus, and dorsal horn of the spinal cord. Enkephalinergic fibers and terminals are found in the above–mentioned areas as well as in the pallium (medial and dorsal cortex, dorsal ventricular ridge), dorsomedial and anterior dorsolateral nucleus of the thalamus, habenua, nucleus of the stria medullaris, torus semicircularis, mesencephalic tegmental area, interpeducular nucleus, mesencephalic trigeminal nucleus, central gray, reticular formation, raphe nucleus, substantia nigra, isthmus region, and nucleus of the trapezoid body. Enkephalinergic pathways appear to exist between the septum and the medial cortex, nucleus accumbens and nucleus of the lateral olfactory tract, striatum and certain mesencephalic structures, hypothalamus and tegmentum, and between nucleus of the lateral lemniscus and torus semicirculais. In the pituitary, cells of the pars intermedia, and certain cells of the rostral pars distalis also show immunoreactivity to enkephalin antiserum. The distribution of enkephalin immunoreactivity throughout the hypothalamus and in the median eminence suggests involvement in neuroendocrine regulation. Presence of enkephalin in many extrahypothalamic brain areas indicates its important role in various sensory functions and in behavioral and autonomic integration.