bluuebunny/crossref_metadata_2025 huggingface dataset:
The olivocerebellar projection studied with the method of retrograde axonal transport of horseradish peroxidase. V. The projections to the flocculonodular lobe and the paraflocculus in the rabbit
Authors: Hoddevik G. H. , Brodal A.
Published: January 2005

HRP was injected in the flocculonodular lobe and the paraflocculus in the rabbit to determine the areas of the inferior olive which project onto these cerebellar regions. Following injections in the flocculus labeled cells occurred in the dorsal cap and the rostralmost tip of the medial accessory olive. Following injections in the nodulus labeled cells were likewise found in the dorsal cap, but in addition in the rostralmost part of the dorsomedial cell column and the adjoining part of the medial accessory olive. Injections in the dorsal paraflocculus gave rise to labeling in the rostrolateral part of the medial accessory olive, while injections in the ventral paraflocculus resulted in labeling in the principal olive, mainly in the lateral part of the ventral lamella. Injections in the lateral thired of the dentate nucleus gave rise to labeling mainly in the dorsal lamella of the principal olive.

The results are discussed with reference to those obtained by previous authors. There are both similarities and discrepancies. It appears from what is known of afferents from areas mediating visual impulses to the inferior olive that the olivary areas projecting onto the flocculondular lobe, and possibly the dorsal paraflocculus, may mediate visual impulses to these lobules.
A histochemical study of the innervation of cerebral blood vessels in the turtle
Authors: Iijima Tadahiko
Published: January 2005

Specific histochemical techniques for the demonstration of noradrenaline and of acetylcholinesterase have been used to study the distribution of adrenergic and cholinergic nerves to the cerebral blood vessels of turtle, Geoclemys reevesii.

The major and medium‐sized cerebral arteries were supplied with dense adrenergic nerve plexuses, the plexuses were particularly dense in the medium‐sized pial arteries of very thick vascular wall, indicating the functional significance of these arteries in the cerebral circulation. The parenchymal arterioles and capillaries were also supplied with adrenergic nerves.

On the other hand, the cholinergic innervation was less dense than the adrenergic one and the acetylcholinesterase activity of the nerve fibres was remarkably weak. By contrast, the parenchymal small arterioles and capillaries exhibited heavy acetylcholinesterase activity on the vascular wall and, in addition, the capillaries were supplied with the well‐stained acetylcholinesterase‐positive nerve fibres. These fibres and also the adrenergic fibres associating with the capillaries appear to be of central origin. It is suggested that the cholinergic mechanisms in the parenchymal small vessels also play an important role in the cerebral circulation.

The basophil leucocytes observed abundantly in the blood of turtle emitted an intensive greenish yellow fluorescence after formaldehyde gas‐treatment.
Experimental analysis of embryogenesis of cerebellum in rat. I. Subnormal growth following X‐ray irradiation on day 15 of gestation
Authors: Das Gopal D.
Published: January 2005

Rat embryos of 15 days gestation were exposed in utero to 170 R of X‐ray irradiation. Embryos collected 6 hours, 1, 2 and 3 days after irradiation, and animals of 2, 6, 15 and 30 days postanatal age were used for this study. Six hours after irradiation cells in the neuroepithelium and mantle layer along the roof of fourth ventricle were observed destroyed. Neuroepithelium showed only fragmentary regeneration during next two days, and it contributed to a small number of Purkinje cells. During postnatal development of cerebellum the external granular layer, the zone of proliferative cells that gives rise to neurons of postanatal origin, was found reduced. Other structures such as internal granular layer, molecular layer and medullary layer also were reduced. These multiple temporally sequenced developmental events resulted in a subnormal‐sized cerebellum. Various quantitative measures helped established that grossly the cerebellum in the X‐ray irradiated animals was aout half of that in the normal animals. Problems related to regeneration in the embryonic cerebellum, and to the factors determining the subnormal size of the adult cerebellum are discussed. Viewing this as an experimental approach to the study of neuroembryogenesis of cerebellum, the role of Purkinje cells in the regulationo f development of cerebellum is brought out.
Ultrastructural basis of impulse propagation failure in a nonbranching axon
Authors: Smith Dean O.
Published: January 2005

The morphological basis of intermittent conduction failure in the excitor axon innervating the crayfish opener and stretcher muscles was investigated using the electron microscope. The connective tissue component of the sheath surrounding the axon was found consistently to be thinner in the region at which blocking occurs than in control regions located one cm either proximally or distally, at which blocking does not occur. Otherwise, in these regions differences in the width of the periaxonal spaces, the length or width of the mesaxons, the density of mitochondria, the width of the adaxonal glial cell layer, or the structure of the lamination of the sheath are not observed. Because of the thinner connective tissue component of the sheath in the joint region, neighboring axons are distributed more densely around the excitor, and the volume of the extracellular space is reduced. The possibility that the reduced extracellular space might allow excessive accumulation of potassium during repetitive discharge, causing conduction block, is discussed. Alternative mechanisms consistent with this morphology are also considered.
An X‐ray diffraction comparison of myelins from the human nervous system
Authors: Chandross Ronald J. , Bear Richard S. , Montgomery Royce L.
Published: January 2005

Earlier small‐angle X‐ray diffraction studies have indicated that central and peripheral nerve myelins may be significantly different structurally, although relatively few examples for each system and for individual species have been examined. In order tounderstand better the intra‐ and inter‐system relationships, this study has developed more extensive information for a single species: six cases centrally and ten peripherally, featuring cranial nerves and a few others of the human nervous system. Peripheral myelin spacings (membrane pair thicknesses) are relatively similar, 184.4 ± 1.40 Å, and the ratios of diffraction peak height intensities of the second to fourth orders are also closelybunched: 1.85 ± 0.216. Central myelin spacings and intensity ratios are distinctly different and more variable: spacings 160.3‐165.8 A and intensity ratios 2.81‐4.46. It appears that within a given species or between closely related (e.g., mammalian) species peripheral myelins possess relatively invariant structures, though significant spacing declines are encountered for both systems as phylogenetic relationships become more distant. The observed greater variability of CNS structures within a singlespecies may correspond to known compositional differences between CNS regionsor result from observational difficulties. In any case there is a marked discontinuity between the myelin structures of CNS and PNS nerves.
Discontinuous transition of myelin structure at the junction between central and peripheral components of the eighth cranial nerve, as disclosed by X‐ray diffraction
Authors: Chandross Ronald J. , Adams Jerry B. , Bear Richard S.
Published: January 2005

Scanning along human acoustovestibular nerves from cross‐sections closely proximal to the brain to locations distinctly peripheral thereto, by means of small‐angle X‐ray diffraction, has disclosed transitional junctions at which the myelin structure typical of central nervous system (CNS) axons gives way to one characteristic of peripheral (PNS) fibers. The junctions correspond to regions along the nerves, previously recognized histologically, at which the satellite cells responsible for axon myelination change character, from the oligodendrocytes of the CNS to the Schwann cells of the PNS. Thus the structural discontinuity between the CNS and PNS myelins can be ascribed to differences in the biosynthetic processes of the respective satellite cells. Junctions of this kind are to be expected in all cranial and spinal roots near the locations where they leave the CNS.
Cortico‐cortical connections of somatic sensory cortex (areas 3, 1 and 2) in the rhesus monkey
Authors: Vogt Brent A. , Pandya Deepak N.
Published: January 2005

The connections of areas 3, 1 and 2 in the postcentral gyrus of the rhesus monkey are investigated using ablation‐degeneration techniques following both full depth lesions and lesions which involved fewer than six cortical layers. Analysis of the topographic and laminar organization of these connections reveal that each of these areas has a differential connection pattern both within the parietal lobe and with respect to motor cortex. Area 3 projects predominantly to area 1 via a horizontal, intracortical fiber system which courses through layers III and V without entering the white matter while other efferents of area 3 to areas 2, 3a and second somatosensory cortex (SII) are less dense and course through the white matter. There is no indication that area 3 efferents terminate in areas 4 or 5. In comparison to area 3, area 1 has a wider projection field. Its primary outflow reaches area 2 via a white matter course while moderately strong connections are directed to areas 3a, S II, 4 and supplementary motor cortex (M II) and a minor projection to area 5. Lesions involving the supragranular layers of area 1 demonstrate that efferents from these layers (II‐III) travel directly through the cortex to terminate in layer I of area 3 as well as entering the white matter before terminating in area 2 ventral to the tip of the intraparietal sulcus. Finally, area 2 projects primarily to area 5 via both an intracortical fiber system in layers III‐V as well as through the white matter. While area 2 also has connections with areas 1, 3a, S II, 6 and M II, it was not observed to project to area 3. In addition, layers I‐IV of area 2 ventral to the intraparietal sulcus send a number of horizontally oriented fibers mainly through layer IIIb to terminate in rostral area 7 (area PF of Bonin and Bailey, '47).

Thus, the projections of these three subdivisions of the postcentral gyrus indicate that there is a strong and sequential outflow of connections from area 3 to areas 1 and 2, then from area 1 to area 2 and finally from area 2 to area 5 and rostral area 7. Each of these connections originates to a large extent from the supragranular layers. In contrast, connections of these areas in the opposite direction toward the central sulcus are less pronounced.
The retinotopic organization of area 17 (striate cortex) in the cat
Authors: Tusa R. J. , Palmer L. A. , Rosenquist A. C.
Published: January 2005

The location and retinotopic organization of visual areas in the cat cortex were determined by systematically mapping visual cortex in over 100 cats. The positions of the receptive fields of single neurons or small clusters of neurons were related to the locations of the corresponding recording sites in the cortex to determine the representations of the visual field in these cortical areas. In this report, the first of a series, we describe the organization of area 17. A single representation of the cat's entire visual field corresponds closely to the cytoarchitectonically defined area 17.

This area has the largest cortical surface area (380 mm2) and the highest cortical magnification factor (3.6 mm2/degree2 at area centralis) of all the cortical areas we have studied. There was perfect agreement between the borders of area 17 determined electrophysiologically and cytoarchitecturally. This area contains a first order transformation of the visual hemifield in which every adjacent point in the visual field is represented as an adjacent point in the cortex. Some variability exists among cats in the extent and retinotopic representation of the visual field in area 17.
The retinotopic organization of lateral suprasylvian visual areas in the cat
Authors: Palmer L. A. , Rosenquist A. C. , Tusa R. J.
Published: January 2005

This is the second in a series of papers in which we describe our continuing efforts to define functional units of visual cortex based upon electrophysiological mapping of single and multiple unit activity in both awake and the nitrous oxide anesthetized cats. In the first paper (Tusa, Palmer and Rosenquist, '78), the extent and retinotopic organization of area 17 were described. In this paper, we describe the somewhat more complex organization of the visual cortex lying on the banks of the middle and posterior suprasylvian sulci. This region of cortex consists of six retinotopically organized units. These areas are arranged as three roughly mirror symmetrical pairs separated in each case by the fundus of the middle or posterior suprasylvian sulci. Some thalamo‐cortical autoradiographic material is presented which supports this parcellation of the cortex.
Expansion of the half retinal projection to the tectum in goldfish: An electrophysiological and Anatomical study
Authors: Schmidt John T. , Cicerone Carol M. , Easter Stephen S.
Published: January 2005

The topographical retino‐tectal projection of goldfish was electrophysiologically mapped at various intervals after surgical removal of the nasal half of the retina and pigment epithelium. The remaining projection was initially restricted to the appropriate rostral half of the tectum, even if the nerve was crushed and allowed to regenerate. But later, after 137 days or more, it showed a progressive expansion onto the foreign caudal half of the tectum. The magnification factor, the number of micrometers of tectum per degree in the visual field, doubled in the rostro‐caudal but not in the medio‐lateral direction. Analysis of the sequence of the expansion showed that a few fibers originally projecting nearest the denervated area were the first to spread over it. Then, progressively more fibers moved caudally until a nearly uniform representation of the half retina was established on the tectum. Radioautography also demonstrated that retinal fiber terminals had invaded the caudal tectum. The retinae of these fish were also examined histologically. The density of ganglion cells had not increased, but they consistently showed the axonal reaction. This was not found to be associated with any initial surgical trauma, but rather with the movement of their fiber terminals within the tectum. Frozen sections, through half retinal and normal eyes, were cut and photographed for comparison of ocular geometry. Operated eyes were normal except for a slight but consistent loss of ocular volume. Analysis of the optical geometry showed that recording with fish in air produced two effects: Myopia (10° blur circle, or less) and enlargement of the visual field by 15% to 20%.
Retinal fibers alter tectal positional markers during the expansion of the half retinal projection in goldfish
Authors: Schmidt John T.
Published: January 2005

Although widely accepted, the theory, that neurones carry immutable cytochemical markers which specify their synaptic connections, is not consistent with plastic reorganizations. Half retinal fish were therefore tested for changed markers following expansion. Optic nerve crush at the time of the half retinal ablation resulted in regeneration of a normal, restricted projection; but nerve crush following expansion (many months later) resulted in reestablishment of the expanded projection, assessed both by electrophysiological mapping and by radioautography. Since this implied changed markers, the half retina and tectum were tested independently using the ipsilateral tectum and eye as controls. In normal fish, removal of one tectum and deflection of the corresponding optic tract toward the remaining tectum resulted in regeneration of a positionally normal but ipsilateral map. In experimental fish, after the half retina had expanded its projection to the contralateral tectum, its optic tract was deflected to the control tectum. After 40 days it had regenerated a normal, restricted map indicating that the retinal markers had not changed. Such restricted projections did not expand in the presence of the normal projection even after a year or more. Similarly, the optic tract from the normal eye was deflected to cause innervation of the tectum containing the expanded half retinal projection. After 40 days, the projection regenerated from the normal eye was similar to the expanded half retinal projection. Areas of the normal retina corresponding to the missing areas of the half retina were not represented. Tectal markers had been altered by the half retinal fibers. In a final group, tecta were denervated and tested at various intervals by innervation from ipsilateral half retinal eyes. After five months of denervation, the regenerating fibers were no longer restricted to the rostral tectum but formed an expanded projection initially. Apparently tectal markers are induced by the retinal fibers, changed during expansion, and disappear during long‐term denervation.
Excitation of marginal and substantia gelatinosa neurons in the primate spinal cord: Indications of their place in dorsal horn functional organization
Authors: Kumazawa T. , Perl E. R.
Published: January 2005

Elecrophysiological recordings were made from superficial parts of the spinal dorsal horn in monkeys, using dye‐filled micropipette electrodes to permit iontophoretic marking of the recording sites for subsequent histological recovery. Focal field potentials and unitary activity evoked by dorsal root volleys including slowly‐conducting components (both myelinated and unmyelinated) were found in the posteromarginal zone and the substantia gelatinosa (SG). Unitary potentials identified as being of the type recorded from cellular regions wee separated into categories according to which groups of slowly‐conducting fibers and which kinds of cutaneous stimulation evoked the discharge. Recording locations for units exicted by volleys in myelinated fibers conducting under 35 m/sec, by the types of skin stimulation activating either highthreshold mechanoreceptors (nociceptos) or cooling thermoreceptors, and giving no evidence of suprathreshold C‐fiber excitation were centered on the posteromarginal zone. In conrast, recording loci for units exhibiting a strong C‐fiber excitation and responses to cutaneous stimulation known to effectively excite C‐fiber polymodal nociceptors or C‐mechanoreceptors were centered in the SG. There appeared varying degrees of convergence of primary afferent input to the neuronal units, although most showed substantial specificity in their afferent excitation. On the bases of these esults and consideration of existing morphological daa, it is proposed that the marginal zone is a major synaptic termination region for the affeent fibers from high‐threshold mechanoreceptors, cooling thermoreceptors, and perhaps otehr receptors with fine myelinated peripheral fibers. The SG, on the other hand, is suggested to be the terminal region for all types of unmyelinated primary afferent sensory neurons, and to have the complex role of integrating and distributing this input.
The connections of the nucleus reuniens thalami: Evidence for a direct thalamo‐hippocampal pathway in the rat
Authors: Herkenham Miles
Published: January 2005

The afferent and efferent connections of the rat's midline nucleus reunions thalami (reuniens) were studied by experiments using the methods of retrograde cell marking by horseradish peroxidase (HRP) and anterograde fiber tracing by autoradiography. A microelectrophoretic deposit of tritiated amino acids in reuniens provided the first evidence of a direct thalamo‐hippocampal connection. Labeled reuniens efferents ascend to the genu of the corpus callosum and turn caudally in the cingulate fasciculus, from which fibers distribute to layer I of the anterior medial, cingulate, and retrosplenial cortices. A longer component of this system curves around the callosal splenium and forms a massive rostrally directed fiber sheet that innervates entorhinal and parahippocampal areas and Ammon's horn. Entorhinal afferents are localized to layers I and III, whereas the hippocampal afferent plexus is remarkably restricted to the stratum lacunosum‐moleculare of the CA1 field and the corresponding stratum of the ventral subiculum.

Reuniens projects more sparsely and diffusely to many subcortical structures, a number of which lie in the limbic domain: the anterior olfactory nucleus, nucleus accumbens, olfactory tubercle, amygdala, claustrum, septum, preoptic area, medial and lateral hypothalamic regions, deep portions of the pretectum and superior colliculus, rostral levels of the ventral tegmental area and central gray substance and, perhaps, the median eminence.

The efferent connections of reuniens were examined with HRP. HRP deposited in the nucleus labeled small to moderate numbers of neurons in many structures extending from the frontal cortex to caudal midbrain levels. The appearance of cell labeling in regions projected upon by reuniens suggests a reciprocity of connections between it and the medial cortex, septum, preoptic area, amygdala, medial and lateral hypothalamic regions, ventral tegmental area, central gray substance, pretectum, superior colliculus and the subiculum. Cell labeling in regions not receiving its efferents – the ventral thalamus, midbrain tegmentum, mesencephalic raphe, and parabrachial nuclei – may hold another clue to the future understanding of the role of the nucleus reuniens in limbic functions.
Early motoneuron formation in the cervical spinal cord of the mouse: An electron microscopic, serial section analysis
Authors: Wentworth Lee E. , Hinds James W.
Published: January 2005

Cells of the ventrolateral region of the cervical spinal cord were reconstructed from serial thin sections in order to provide direct evidence concerning the early stages of motoneuron differentiation. Analysis of 321 sections from the spinal cord of a mouse embryo on the tenth day of gestation (E10) was performed. At E10 the general appearance of the ventrolateral region is that of a pseudostratified columnar epithelium. It consists primarily of radially oriented ventricular cells, while the remaining cells are either rounded mitotic cells (located at the neurocoel) or cells differentiating into either accessory root or ventral root motoneurons. The following early stages of motoneuron differentiation have been distinguished: anaxonic primitive bipolar cells (stage 1); primitive bipolar cells with an axon (stage 2); unipolar cells (stage 3); and secondary bipolar cells (stage 4). The earliest morphological change in the differentiation of both types of motoneurons appears to be the withdrawal of the apical process from the neurocoel and the migration of the Golgi apparatus, centrioles and cilium along the apical process toward the nucleus (anaxonic primitive bipolar cell). The nucleus then appears to migrate peripherally and the basal process (which never completely withdraws) to transform into an axon (primitive bipolar cell with an axon). Subsequent stages have only been identified in accessory root motoneurons; it appears that ventral root motoneurons are not as advanced in their differentiation at E10. In the unipolar stage the apical process has completely withdrawn, and the nucleus appears paler and rounder than that of earlier cells. Finally, in the secondary bipolar stage the cell is oriented dorsoventrally with an axon directed dorsally and a dendrite ventrally from the opposite pole of the cell. During differentiation of accessory root motoneurons, the Golgi apparatus, centrioles and cilium are found first in the apical process, then at the base of the axon, and finally at the base of the dendrite. The translocation of these organelles occurs secondary to the initial formation of first the axonal and then the dendritic process.
Qualitative and quantitative study of synaptic displacement in chromatolyzed spinal motoneurons of the cat
Authors: Chen D. H.
Published: January 2005

Qualitative and quantitative cytological evidences show a reduction in number and percentage of coverage of terminals on chromatolyzed spinal motoneurons 4 to 90 days after severance of their axons in the ventral root. The reduction in number and percentage of boutons on the surface membrane is due to detachment of synapses. This detachment is associated with changes in specialized regions (synaptic complexes: Conradi, '69) of synapses which involve disappearance of both pre‐ and postsynaptic membrane thickenings and widening of the synaptic cleft (width of 400‐1,400 A). The separation of terminals from surface membrane is also associated with the presence of reactive astrocytes and microglia. Most areas of surface membrane bared of synaptic contact are occupied by astrocytic processes. The astroglial responses coincide with the loss of synapses. Microglial cells, although extending to neuronal surface membrane, cover only a small portion of it. An extensive separation of boutons by microglia is not observed. Most microglia are seen located at some distance from surface membrane and are frequently separated by sheets of astrocytic processes. Synaptic restoration occurs by about 90 days after axotomy. Some motoneurons show good recovery, while others show only a limited amount.
Afferent projections to the rat locus coeruleus as determined by a retrograde tracing technique
Authors: Cedarbaum Jesse M. , Aghajanian George K.
Published: January 2005

Afferent connections to the rat locus coeruleus (LC), which contains exclusively noradrenergic neurons, have been traced using the technique of retrograde transport of horseradish peroxidase (HRP). In order to ensure accurate placement of adequate amounts of HRP in the LC, a microiontophoretic delivery technique coupled with single cell recording was employed. The use of electrophysiological “landmarks” as aids in placing the injections is described. Following HRP injections into the LC, forebrain structures containing labelled neurons included the insular cortex, the central nucleus of the amygdala, the medial, lateral and magnocellular preoptic areas, the bed nucleus of the stria terminalis, and the dorsomedial, paraventricular and lateral hypothalamic areas. In the brainstem reactive neurons were observed in the central grey substance, the reticular formation, the raphe, vestibular, solitary tract and lateral reticular nuclei. In particular, the areas of catecholamine cell groups A1, A2 and A5 appeared to contain many reactive cells. Labelled neurons were also observed in the fastigial nuclei and in the marginal zones of the dorsal horns of the spinal cord. This pattern of afferent innervation supports suggestions for a role for the LC in behavioral arousal mechanisms and autonomic regulation.
Cytology of neurons of the hypothalamic ventromedial nucleus in the adult male rat
Authors: Van Houten Mark , Brawer James R.
Published: January 2005

Recent evidence suggests that the hypothalamic ventromedial nucleus contains a wide variety of functionally specialized neurons, some of which are located within discrete regions of the nucleus. However, regional morphologic variations in neuronal populations within the HVM have not been demonstrated. In the present report, the neurons of the HVM were studied in young adult, male rats with the electron microscope. The collection and analysis of cytologic data were systematized with reference to location on a histologic map of the HVM, which was prepared prior to fine structural study.

Neurons of the HVM were observed to exhibit regional variations in cytology. For example, cisternae of the rough endoplasmic reticulum in the anterior and dorsomedial regions of the nucleus are commonly collected into regular stacks typical of Nissl bodies. In contrast, rough cisternae in the posterior ventrolateral region of the HVM are often extremely long and pleomorphic, and form broad, loosely organized Nissl zones, in which occur myelin figures and wide varieties of cytoplasmic filamentous bodies.

Other neurons located principally in the ventrolateral and posterior regions of the nucleus are characterized by the presence of whorled bodies. Still others restricted to the lateral rim of the nucleus are conspicuous by virtue of their enormous size and massive accumulation of Nissl material.

One extremely unusual variety of HVM neuron is distinguished by the presence of large, acristic mitochondria, polysomal disaggregation, and aberrant nucleolar morphology. These cytologic features may indicate metabolic quiescence and perhaps anaerobiosis.

Possibly these region‐centered variations in neuronal cytology reflect the functional parcellation of the HVM.
A quantitative study of synaptic patterns in turtle visual cortex
Authors: Ebner Ford F. , Colonnier Marc
Published: January 2005

The distribution of different synaptic types has been analyzed quantitatively in the molecular and subcellular layers of turtle „vislual”︁ cortex. The density of vesicle‐containing‐profiles (VCPs) is 122.2/400 square μm in the molecular layer and 61.0/400 square μm in the subcellular layer. In both layers, approximately 85% of VCPs conatin round vesicles (RVCPs), 12%, flat vesicles (FVCPs) and 1%, dense core vesicles (DVCPs). Vacuolar invaginations (VIs) are not uncommon in the molecular layer (3.4%) but are rare in the subcellular layer (0.6%). Synaptic conatacts are formed in the plane of section by three out of ten RVCPs and FVCPs, while only one out of the 146 DVCPs sampled in this study was associated with a membrane differentiation. In the molecualr layer, the percentage distribution of the different subgroups of synaptic types is as follows: round‐asymmetrical contacts, 82.5% (77.5% on dendritic spines and 5.0% on dendritic shafts); round‐symmetrical contacts, 3.8% (2.3% on spines and 1.5% on shafts);flat‐symmetrical contacts, 13.1% (8.8% on shafts and 4.3% on spines; flatasymmetrical contacts 0.6% (0.4% on spines and 0.2% on shafts)). In the subcellular layer, the distribution is quite different: round‐asymmetrical contacts. 72.4% (38.6% on shafts and 33.8% on spines); round‐symmertical contacts, 12.8% (8.2% on shafts and 4.6% on spines); flat‐symmetrical contacts, 13.9% (9.3% on shafts and 4.6% on spines); flat‐asymmetrical contacts, 0.9% all on dendritic shafts. The density distribution of VCPs in the molecular layer changes with depth. RVCPs are fewer on the distal third of the apical dendrites, and most numerous in the middle third with a small dercease in number in th proximal third. FVCPs are more homogeneously distributed, perhaps increasing slightly in number towards the proximal parts of the dendritets. RVCPs are most numerous on dendritic spines. These spines are of two types whose relative number varies with depth. Large organelle‐filled spines predominate in the upper third while small „empty”︁ spines are most numerous in the lower third of the molecular layer.
Atlas of the distribution of monoamine‐containing nerve cell bodies in the brain stem of the cat
Authors: Poitras D. , Parent A.
Published: January 2005

The distribution and morphological characteristics of monoamine (MA)‐containing neuronal somata in the brain stem of kittens and of adult cats were studied by means of the Falck‐Hillarp histofluorescence method. This investigation has shown, among other things, that in the mibrain of the cat the catecholamine (CA) perikarya are chiefly confined to the pars compacta of the substantia nigra, the ventromedial tegmental area, the nucleus linearis rostralis and the nucleus parabrachialis pigmentosus. Numerous CA neurons are also present in the dorsolateral part of the pontine tegmentum but also within the nucleus subcoeruleus, in nuclei lemnisci lateralis dorsalis and in nuclei parabrachialis lateralis and medialis. In the medulla, a few CA neuronal somata are lying near the hypoglossal nucleus whereas a larger number of CA cell bodies occur at the level of nucleus reticularis lateralis and in nucleus paragigantocellularis lateralis. On the other hand, most of the serotonin (5‐HT) perikarya are confined to the raphe nuclei of the brain stem: nuclei raphe dorsalis, centralis superior, raphe pontis, raphe magnus, raphe pallidus and raphe obscurus. Some 5‐HT neuronal somata are also found lateral to the pyramidal tract and to the inferior olivary complex. The various similarities and differences in respect to the pattern of the topographical distribution of MA neurons in the brain stem of the cat as compared to that of other mammals are discussed.
Projections to the inferior olive of the cat II. Comparisons of input from the gracile, cuneate and the spinal trigeminal nuclel
Authors: Berkley K. J. , Hand P. J.
Published: January 2005

The present experiments compare the pojections to the inferior olive of the cat from the gracile, cuneate and spinal trigeminal nuclei. A differential labeling strategy was used for these comparisons.

It was found that all three somatic sensory nuclei project to portions of all three major divisions of the contralateral inferior olive. The spinal trigeminal n. may also project less densely to the ipsilateral medial accessory olive. Projections to the dorsal accessory nucleus (DAO) and the medially‐adjacent ventral lamella of the principal nucleus are roughly somatotopically organized. Although there is considerable overlap between the projections predominantly to medial DAO, and the spinal trigeminal nucleus pars caudalis projects predominantly to the most medial portions of DAO and the ventral lamella of principal olive. Projections to the medial accessory olive, on the other hand, are not as highly organized. Instead, they overlap extensively within a small eggshaped area in the middle of the caudal half of the nucleus.

Whereas all portions of the gracile and cuneate nuclei project to the inferior olive, only the pars caudalis of the spinal trigeminal nucleus appears to do so.

These results were compared with the three available olivocerebellar maps as well as with the available behavioral and electrophysiological evidence on cerebellar somatotopic organization. This comparison indicated that the inputs to the cerebellum from the three second‐order somatosensory nuclei via the inferior olive appear to be generally consistent with cerebellar somatotopic organization. This consistency is apparent not only with respect to the longitudinally‐organized, vermal and paravermal differences in the anterior lobe, but also with respect to the transversely‐organized specific somatotopy of the intermediate zone of the anterior lobe and the paramedian lobule.
In situ injection of kainic acid: A new method for selectively lesioning neuronal cell bodies while sparing axons of passage
Authors: Coyle Joseph T. , Molliver Mark E. , Kuhar Michael J.
Published: January 2005

The morphologic sequelae following stereotaxic injection into the rat striatum of kainic acid, a conformationally restricted analogue of glutamate, were examined by means of bright fields, histofluorescence and electron microscopic techniques. The neuropathologic response to kainate injection occurs in two distinct phases. Fist, the intrinsic neurons of the striatum undergo a rapid degeneration during the first 48 hours after injection; this is characterized by the sequential loss of cytoplasmic Nissl‐substance (chromatolysis), shrinkage of the perikarya, clumping of the nuclear chromatin and finally disruption of the nuclear membrane. Between one and three weeks after injection, a marked proliferation of astrocytes in the gray matter formerly populated by neurons characterizes the second phase. The region of several neuronal loss in the kainate injected stratum is approximately spherical in shape, and its extent is non‐linearly related to the amount of kainate injected. The neuropil of the injected striatum is markedly disrupted due to the death of intrinsic neurons and loss of their processes. Yet, histofluoresence microscopy demonstrates that the dopaminergic axons projecting from the substantia nigra do not degenerate in the kainate injected striatum; electron microscopic studies indicate that corticofugal fibers traversing the striatum also unaffected by kainate. Many presynaptic boutons, presumably of extrinsic origin, are intact up to ten days after injection; osmophilic vestiges of postsynaptic elements remain adherent to these boutons. Numerous phagocytic astrocytes are observed throughout the lesioned area. These morphologic studies provide (direct) evidence that in situ injection of kainic acid in brain causes a selective degeneration of neurons with cell bodies in the area of the injection but spares axons that arise from perikarya outside the region but pass through or terminate in the injected area. Thus, in situ injection of kainic acid is a new technique for making selective brain lesions that will be useful for examining neuronal connectivity.
Terminal proliferation and synaptogenesis following partial deafferentation: The reinnervation of the inner molecular layer of the dentate gyrus following removal of its commissural afferents
Authors: McWilliams Randall , Lynch Gary
Published: January 2005

The inner one‐third of the dendritic region of the dentate gyrus granule cells in adult rats receives projections primarily from the commissural fibers of the contralateral hippocampus and the associational fibers of the ipsilateral hippocampus. At two to four days following the complete removal of the contralateral hippocampus, approximately 25% of the terminals in the inner molecular layer are observed degenerating. This provides an excellent model system to investigate possible terminal proliferation induced by deafferentation since (1) the experimental lesion is easily reproducible, (2) no retrograde reactions occur in the granule cells as a direct result of the lesion, (3) no shrinkage is detected in this region following commissural deafferentation, (4) the same dendritic region can be relocated precisely in each animal, and (5) the synaptic counts are highly consistent between animals.

Results from this study and from previous investigations demonstrate that the commissural projection is contained within a 0–80 μ zone directly above the granule cell layer. Complete photomontages of this zone were taken, but only the 40–80 μ zone was quantified for neuronal and glial changes in three normal, five 2‐ to 4‐day, and five 50‐ to 75‐day postlesion animals. The average synaptic count dropped to 64% of control values by 2 to 4 days, but returned to 97% by 50‐ to 75 days postlesion. The number of terminals showing multiple synaptic contacts increased slightly in the long‐term animals. Measurements of average terminal area showed no change between the short‐ and long‐term survival groups. These results indicate that this dendritic region is reinnervated following partial deafferentation and that the reinnervation is due primarily to the formation of new terminals rather than the expansion of pre‐existing terminals.
Functional properties of the corticotectal projection in the golden hamster
Authors: Rhoades Robert W. , Chalupa Leo M.
Published: January 2005

Approximately 31% of the cells recorded in the hamster's superior colliculus could be activated by stimulation of the ipsilateral primary visual cortex. While cortically activated cells were encountered in all laminae of the colliculus where visual cells were isolated, the highest probability of driving visual cells was observed in the deeper laminae, that is, those ventral to the stratum opticum. Response latency, jitter (latency variability), latency shifts as a function of shock intensity, thresholds, and spike numbers did not vary as a function of depth in the colliculus. There was a clear correspondence between the visual fields of the best cortical stimulus points and the receptive fields of cortically activated cells recorded in the superficial laminae of the colliculus. However, there was considerably less retinotopic fidelity for the cortical areas from which cells isolated in the deeper laminae could be driven. This suggests a greater degree of convergence from relatively widespread cortical regions upon visual cells of the deeper laminae. The visual response properties (directional selectivity, speed preferences, and receptive field organization) of the cortically activated cells did not differ appreciably from the overall sample of visual cells recorded in the colliculus. Only 3 of the 159 cells tested were driven by stimulation of the contralateral visual cortex and two of these were responsive only at very long latencies.
A comparative study of the neurons of origin of the spinocerebellar afferents in the rat, Cat and squirrel monkey based on the retrograde transport of horseradish peroxidase
Authors: Snyder Russell L. , Faull Richard L. M. , Mehler William R.
Published: January 2005

The cell bodies of the neurons of the spinocerebellar pathways were examined using large injections of horseradish peroxidose into the cerebellum. Sections of each spinal segment were examined with both the DAB and the de Olmos O‐dianisidine techniques. Results common to all three species were found. In Clarke's nucleus, the central cervical nucleus, and the spinal border cells there were many heavily labeled cells. Clarke's nucleus was found to project primarily ipsilaterally; the spinal border cells primarily contralaterally; and the central cervical nucleus bilaterally. In addition to these aggregates of spinocerebellar neurons there were numerous labeled neurons scattered throughout the spinal grey. Labeled neurons were found in all portions of the spinal grey except the substantia gelatinosa and lateral cervical nucleus and occurred in all spinal segments. They varied in morphology from large multipolar neurons, found predominantly in the ventral horn to small globular and fusiform neurons that were most abundant in the dorsal horn. These cells were found to project both ipsilaterally and contralaterally. Results common to only two of the species examined were also found. In the squirrel monkey and the cat, but not the rat, the marginal layer of the dorsal horn in all segments of the spinal contained numerous labeled neurons. These marginal neurons were especially numerous in the squirrel monkey, where as many as 13 to 16 labeled neurons per section of the dorsal horn were found. In the rat and the squirrel monkey but not the cat, some intensely labeled large multipolar neurons were found in the sacral and caudal segments. These are the cells of Stilling's nucleus, a column of cells similar in position and orientation to that of Clarke's column but different in its projections and details of cytoarchitecture. Thus we have not only confirmed that Clarke's nucleus, the central cervical nucleus, and the spinal border cells project to the cerebellum but we have also found several new sources of spinocerebellar afferents.
Cell bodies of origin of reticular projections from the superior colliculus in the cat: An experimental study with the use of horseradish peroxidase as a tracer
Authors: Kawamura Koki , Hashikawa Tsutomu
Published: January 2005

By use of the retrograde axonal transport of horseradish peroxidase (HRP), the projection from the superior colliculus (SC) to the brain stem reticular formation (RF) was investigated in the cat. A 0.2–0.5 μl of a 50% suspension of Sigma VI HRP was injected stereotactically in various portions of the pontomedullary RF, and, as a control to the injection to the RF, in the inferior olive or in the spinal cord.

Labeled cells were found within and deep to the intermediate gray layer of the SC in the cats which survived for two or three days after HRP injection. The number of the labeled cells varied, according to the difference in the site of injection and the amount of injected HRP. About 400 labeled cells in twenty 50‐μm sections, taken every fifth of the SC, occurred throughout its rostrocaudal extent, particularly in the case where the medial portion of the border zone of the nucleus reticularis pontis oralis and the caudalis (R.p.o.‐R.p.c. zone) or the border zone of the nucleus reticularis pontis caudalis and the gigantocellularis (R.p.c.‐R.gc. zone) was heavily stained after three days of survival period. From 10 to 15% of these labeled cells were large in size (more than 40 μm in diameter), 20–30% were medium sized and the rest (60–70%) were small (10–25 μm). On the other hand, when HRP was placed in the inferior olive only eight cells were labeled in the SC, seven of which were small and medium sized. When HRP was injected in the gray matter of C1C3 level of the spinal cord, a total of 70 tectal cells (14, 42, and 14 were large, medium, and small cells, respectively) were observed to be labeled.

The findings of the tectoreticular neurons are discussed and compared with those of the tectoolivary and the tectospinal neurons. Thus the three kinds of tectal neurons are located within and deep to the intermediate gray layer. The number of the labeled cells and the percentage of the collicular neurons of different sizes are obviously different among the three different projections.

Topographic correlations between the SC and the RF could not be discerned in the present materials. These results were discussed in relation to possible influences of the tectoreticular neurons upon the extraocular and the spinal motoneurons.
Development of the dorsal lateral geniculate nucleus in the cat
Authors: Kalil Ronald
Published: January 2005

The development of the lateral geniculate nucleus has been studied systematically in Nissl preparations from a series of cats that ranged in age from newborn to adult. In addition, preliminary observations are reported at two stages of fetal development.

It was found that laminae develop in the lateral geniculate nucleus near the time of birth and continue to differentiate during the first postnatal week. During development the major axis of the lateral geniculate rotates approximately 180° in the sagittal plane. The rotation begins prenatally and is not completed until after the twentieth postnatal week.

The volume of the lateral geniculate was computed at different ages and it was determined that during the first postnatal month the nucleus attains two‐thirds of its adult size. However, the rate of growth declines markedly thereafter, and final volume, like final position, is not achieved until late in development.

The cross‐sectional areas of lateral geniculate neurons were measured at four locations in the nucleus in each animal. The locations represented the following parts of the visual field: the paracentral and inferior peripheral fields in the binocular segment of lamina A; the monocular segment of lamina A; and the paracentral field in lamina A1. Neurons in each of these locations grow at approximately the same rate and are essentially fully grown by 56 days. Cell size histograms show that more large cells are found in lamina A1 and more small cells in the monocular segment than elsewhere in the dorsal laminae. Unlike the retina, there appears not to be a gradient of development in the lateral geniculate nucleus from center to periphery, at least in terms of cell body size at the ages studied. On the contrary, that part of the lateral geniculate nucleus which represents the paracentral visual field is the last segment in the dorsal laminae to achieve a mature cell size distribution.

Finally, a discrete class of small spindle‐shaped neurons was observed in the lateral geniculate nucleus ventral and caudal to the C laminae during the first two postnatal weeks. These cells possess a leading and trailing cytoplasmic process and are distinctly different from cells in the main laminae. It is suggested that these spindle‐shaped cells may be neurons that are still in the process of migration or differentiation in the postnatal animal.