bluuebunny/crossref_metadata_2025 huggingface dataset:
Preservation of binocularity after monocular deprivation in the striate cortex of kittens treated with 6‐Hydroxydopamine
Authors: Kasamatsu Takuji , Pettigrew John D.
Published: January 2005

The results of single unit recordings from Area 17 of monocularly deprived kittens were compared with similar ones from littermates who had been monocularly lid‐sutured for the same period of time, but who had in addition been given intraventricular injections of 6‐hydroxydopamine (6‐OHDA) to deplete brain catecholamines. The visual cortices of all catecholamine‐depleted kittens showed high proportions of binocular neurons, in contrast to the control group, a majority of whose visual cortical neurons were driven exclusively by the non‐deprived eye. Preservation of binocularity in 6‐OHDA‐treated kittens was dose‐related. Even after a 1 to 2‐week period of lidsuture which reduced binocularity to 20% in controls, normal proportions of binocular neurons (>75%) were preserved if the cumulative dose had been 10 mg 6‐OHDA or more. The density of single neurons sampled from electrode tracks through the cortex of drug‐treated kittens was high and did not differ significantly from controls. Neurons were isolated every 100 μm on the average. There was some indication that the drug's effect in preventing an ocular dominance shift disappears by six weeks following cessation of 6‐OHDA treatment. This reversal of the physiological effects in cortex is preceded by recovery from the behavioral manifestations of 6‐OHDA treatments. Binocularity was only slightly increased in a kitten who received large doses of 6‐OHDA after a period of monocular deprivation. This observation, together with control recordings from normal kittens and adults treated with 6‐OHDA, indicates that the direct effects of 6‐OHDA on cortical neurons' response properties play a minor role in comparison to its effects in reducing the sensitivity of the cortex to monocular deprivation. The overwhelming majority of cortical neurons in 6‐OHDA‐treated kittens remained normal in receptive field properties after a period of monocular deprivation. These data support the hypothesis that catecholamines are required for the maintenance of visual cortical plasticity during the critical period.
Intracellular marking with Lucifer Yellow CH and horseradish peroxidase of cells electrophysiologically characterized as glia in the cerebral cortex of the cat
Authors: Takato Michiaki , Goldring Sidney
Published: January 2005

Intracellular microelectrodes filled with either Lucifer Yellow CH, a highly florescent dye, or horseradish peroxidase (HRP) were used to electrophysiolgically characterize and mark cells in the cerebral cortex of cat. Fifty‐eight cells, characterized electrophysiologically as glia, were marked with Lucifer Yellow CH. All were identified as protoplasmic astrocytes, and included cells in the glia limitans of the molecular layer. An additional 54 cells, similarly characterized as glia, were labeled with HRP. The results were the same; only protoplasmic astrocytes were labeled. The “staining quality” of the glia labeled with HRP was superior to that of cells injected with Lucifer Yellow; greater lengths of individual processes were revealed, and they could often be followed to blood vessels where they ended on the walls of vessels with expanded perivascular end‐feet. The observations indicate that the many previously reported studies on presumed glial cells in the cat cerebral cortex have characterized the behavior of protoplasmic astrocytes.

Neurons were also marked during these experiments. The “staining” quality of the Lucifer Yellow filled neurons was excellent; dendritic spines, axons, and axon collaterals were clearly visible. These fine neuronal details were not as well revealed after HRP labeling. High resting membrane potentials (RMPs) were not a prerequisite for obtaining well‐marked neurons (mean RMP of Lucifer Yellow filled neurons was −33.6 mV; mean RMP of HRP filled neurons was 42.3 mV). In contrast, the mean RMPs of Lucifer Yellow and HRP marked glia was −68 Mv and −75 mV respectively, and the quality of “staining” appeared to be more closely related to the RMP.
Excess DNA in the nuclei of the subseophagel region of octopus brain
Authors: De Marianis Bruna , Olmo Ettore , Giuditta Antonio
Published: January 2005

Cytophotometric analyses of Feulgen‐stained nuclei present in homogenates of vertical and subseophageal lobes of octopus brain have shown that the latter region contains larger nuclei with up to several times the amount of DNA present in vertical nuclei. No obvious relationship was found between DNA content and nuclear size. Except for a rather small minority, nuclei of the vertical lobe have a uniform size and the expected diploid amount of DNA. These parameters are not substantially dependent on body weight. In contrast, the DNA content of subesophageal nuclei increases progressively with body weight. The amount of DNA found in subesophageal nuclei does not seem to be a simple multiple of the diploid or haploid value.
The specificity of innervation of regenerating motor neurons in the cockroach
Authors: Whitington Paul M.
Published: January 2005

The pattern of neuromuscular connections of cockroach motor neurons regenerating to an intact mesothoracic leg after crushing nerve 5 has been investigated. While a number of anatomically identified motor neurons re‐established functional connections with their correct target muscles, some of the same and other motor neurons were found to functionally innervate inappropriate muscles. Muscles, and in some cases individual fibres, were often simultaneously innervated by both correct and foreign motor neurons. The frequency of innervation errors decreased with increasing post‐operative times, although some errors persisted to the latest stages examined (227 days).
Excitatory synaptic ensemble properties in the visual cortex of the macaque monkey: A current source density analysis of electrically evoked potentials
Authors: Mitzdorf U. , Singer W.
Published: January 2005

The spatio‐temporal distributions of excitatory synaptic ensemble activities in A17 and A18 of the visual cortex of the macaque monkey have been investigated. The synaptic activities were elicited by electrical stimulation of the primary afferents and were localized by applying the current source density analysis to the intracortically recorded field potentials. The principal results are as follows.

In A17, two groups of activity, evoked by fast and slow afferents, respectively, were distinguishable.

The fast afferents induce monosynaptic activity in layer IV Cα and layer VI, disynaptic activity in layer IV Cα and in the supragranular layers and trisynaptic activity in layer IV B.

The slow afferents induce monosynaptic activity in lower layer IV Cβ and layer VI, disynaptic activity via strong connections in upper layer IV Cβ, further disynaptic activity in layers III and IV B and trisynaptic activity in layers V A and II.

With the exception that the CSD data reveal more polysynaptic activity within layer IV, there is good agreement between the spatio‐temporal distribution of synaptic activities and the cortical circuit diagrams proposed in anatomical studies.

In A18, activities from the slow and fast conducting afferent systems are revealed in layer IV, both most likely mediated by the monosynaptically activated target cells of A17. These activities are passed on to the supra‐ and infragranular lavers.

In the lateral geniculate nucleus the safety factor of transmission is higher for activity conveyed by slow‐ than by fast‐conducting retinal afferents.

The spatial distribution of monocularly evoked surface potentials failed to reveal the ocular dominance columns.

Comparison with the cat indicates that, with respect to the intracortical circuitry and LGN‐transmission, there are more similarities between the fast‐group activity in the monkey and the x‐system in the cat and between the slow‐group activity in the monkey and the y‐system in the cat than vice versa.
Inteneuron circuits in the lateral geniculate nucleus of monocularly deprived cats
Authors: Mooney Richard D. , Dubin Mark Wm. , Rusoff Anne C.
Published: January 2005

This work investigated the function of interneurons and other types of cells in the lateral geniculate nucleus (LGN) in cats raised to adulthood with one eye sutured closed. In order to understand the basis of the commonly found deficit of Y‐type relay cells in the deprived layers of the LGN, we looked for reduced or defective activity in other cells which also receive an afferent projection from Y‐type ganglion cells in the visually deprived retina.

Monocular deprivation did not produce a deficit in the activity of a class of interneurons which receive direct optic inputs from the same ganglion cells in the deprived eye that also drive the Y‐type relay cells. Likewise, the Y‐type afferent input from the deprived eye to XY‐type relay cells was normal. The XY‐type cells have mixed or hybrid receptive field properties and both X and Y excitatory inputs; although the Y‐inputs to these cells are often much weaker than the X‐inputs. The normal properties of Y‐type interneurons and XY‐type relay cells in the deprived LGN suggest that neither a retinal dysfunction nor an inherent inability of the Y‐type optic tract axons to form adequate synapses onto LGN neurons are factors which would readily account for the reduction of y‐type relay cells in monocularly deprived cats.

The hypothesis that the deprived Y‐type relay cells may have difficulty in forming synaptic connections onto postsynaptic, binocular neurons was supported by observations of responses of cells in the perigeniculate region. Normally, perigeniculate neurons receive a strong binocular input from Y‐type relay cells as well as an X‐input in at least some cases. In binocular perigeniculate cells of the sutured cats, no inputs from deprived Y‐type relay cells could be identified although a longer latency input, typical of that from X‐type relay cells, was present.
Postnatal neurogenesis in the kitten retina
Authors: Johns Pamela Raymond , Rusoff Anne C. , Dubin Mark Wm.
Published: January 2005

Postnatal neurogenesis in the kitten retina was studied using 3H‐thymidine radioautography. Kittens were injected with 3H‐thymidine at 1 day, 10 days, 3 weeks or 4 weeks after birth and allowed to survive until 14 weeks of age. Labeled neuronal nuclei were not found in the ganglion cell layer in any of the retinas, but they were seen in the other nuclear layers of the same retinas. In retinas from kittens injected at one day after birth, the peripheral 80% of the length of the retina (in sections cut parallel to the dorsoventral meridian) contained labeled nuclei; the central 20%, around the optic disc, contained no labeled nuclei. Near the ora serrata most nuclei in both inner and outer nuclear layers were labeled. Away from the ora serrata the proportion of labeled to unlabeled nuclei gradually decreased. Labeled nuclei extended farther centrally in the inner than the outer nuclear layer. The same pattern of labeling was repeated in retinas from kittens injected at ten days after birth, but fewer nuclei were labeled, and the central, unlabeled region around the optic disc was longer–55% of the length of the retina. Only a few nuclei near the ora serrata were labeled in retinas from kittens injected at three weeks after birth, and no labeled neurons were found in kittens injected at four weeks.

From these results we conclude that all of the ganglion cells in the kitten retina are present by one day after birth, as are all of the other neurons in the central retina. In peripheral regions of the inner and outer nuclear layers, proliferation of cells destined to become neurons continues up to three weeks after birth.
The structural organization of the inferior and lateral subdivision of the Macaca monkey pulvinar
Authors: Ogren Marilee P. , Hendrickson Anita E.
Published: January 2005

Previous light microscopic studies of Macaca pulvinar have demonstrated that both the inferior and adjacent portion of the lateral pulvinar subdivisions are reciprocally connected to the entire occipital lobe, including striate cortex. They differ in that inferior but not lateral pulvinar receives a projection from the superficial layers of the superior colliculus. In this study, the internal organization of these two subdivisions is compared by relating light microscopic Golgi morphology to the synaptic organization observed by electron microscopy.

The Golgi impregnated neurons in inferior and lateral pulvinar are typical of other thalamic nuclei and are not qualitatively different in the two subdivisions. Projection neurons (PN) vary in cell body (15–40 μm) and dendritic tree (150–600 μm) diameters but bear the same varieties of dendritic appendages; spine‐like, hair‐like, and knot‐like. Local circuit neurons (LCN) have smaller cell body diameters (10–20 μm) but can have very large dendritic field diameters (150–600 μm). They are best distinguished from PNs by their elaborate dendritic appendages, which have been identified as pre‐synaptic dendrites in the EM. LCN axons are infrequently seen.

In the EM both subdivisions contain four types of synaptic terminals. RS and RL terminals both contain round synaptic vesicles and make asymmetric synaptic contacts, but are subdivided on the basis of small (RS = 0.09 μm) versus large (RL = 2.2 μm) cross sectional diameters and organelle content. RLs contact larger caliber dendrites and frequently form synaptic complexes with presynaptic dendrites of LCNs, while RSs contact fine caliber dendrites and rarely take part in synaptic complexes. F terminals and P boutons both contain flat and pleomorphic vesicles and make symmetric synaptic contacts. They are characterized by vesicle number and cytoplasmic density. Fs are infrequently observed in pulvinar compared to P boutons and are of uncertain origin. P boutons can be equated with LCN dendritic appendages and have been identified as pre‐synaptic dendrites. The quantitative distribution of each type is very similar in both subdivisions, averaging RS 85%, RL5%, F 0.3%, P 8% and unidentified 2%.
Abducens internuclear neurons and their role in conjugate horizontal gaze
Authors: Carpenter Malcolm B. , Batton Robert R.
Published: January 2005

Experimental evidence suggests that brain stem lesions producing paralysis of lateral gaze and dissociation of conjugate horizontal eye movements have certain common features. Both of these disturbances involve abducens internuclear neurons (Abd IN) or their projections. Attempts were made to determine the course and terminal distribution of Abd IN in the monkey by autoradiographic techniques. Tritiated amino acids injected in the abducens nucleus (Abd N) labeled: (1) root fibers ipsilaterally, and (2) fibers that ascended in medial parts of the contralateral medial longitudinal fasciculus (MLF). In the opposite oculomotor complex (OMC) silver grains were profuse over the ventral nucleus (VN, medial rectus muscle) and patchy over caudal parts of the dorsal nucleus (DN, inferior rectus muscle). Labeling of cells in the reticular formation ventral to Abd N resulted in transport ipsilaterally, outside the MLF, to the rostral interstitial nucleus of the MLF (RiMLF), a cell group considered to be concerned with vertical eye movements.

Bilateral labeling of Abd N and cells of the nucleus prepositus (NPP) resulted in bilateral: (1) transport of isotope via root fibers and the MLF, and (2) selective distribution of silver grains in the OMC. Bilateral silver grain distribution in the OMC suggested profuse terminations in VN, patchy terminations in DN and vertical, linear terminations in caudal parts of the medial nucleus (MN, superior rectus muscle). Comparisons with more discrete unilateral labeling of cells in Abd N suggested that cells of the NPP project selectively to terminations in MN, and may be related to upward eye movements.

Two conclusions were drawn: (1) The paresis of ocular adduction which occurs in both anterior internuclear ophthalmophlegia and in paralysis of lateral gaze results from involvement of Abd IN or their ascending projections, and (2) the NPP appears to project selectively to parts of MN of the OMC, a cell group said to provide crossed innervation for the superior rectus muscle.
A quantitative comparison between the ganglion cell populations and axonal outflows of the visual streak and periphery of the rabbit retina
Authors: Vaney David I.
Published: January 2005

A vertical density profile of the ganglion cells 2 mm temporal of the optic nerve head in the rabbit retina has been produced by counting somata in the cresyl‐violet‐stained, ganglion cell layer of a flat‐mounted retina. Somata classified as ganglion cells were characterized by obvious Nissl staining in an extensive cytoplasm and typically had diameters greater than 9 μm. The accuracy of the profile, and thus of the classification criteria, has been substantiated by electron micrographic determination of the numbers of ganglion cell axons arising within local regions of known area on the same retina

This study indicates that Vaney and Hughes' estimate ('76) of 547,100 presumed ganglion cells in the rabbit retina should be changed to 373,500 ganglion cells. The latter value is within the statistical error of their optic nerve count of 394,000 fibers

The mean diameter of ganglion cells 6 mm from the visual streak in the inferior periphery (density: 550 cells/mm2) was 28% greater than that of cells on the peak of the streak (density: 5,400 cells/mm2), although the form of the ganglion cell diameter distribution did not change markedly with eccentricity. The increase in the mean size of ganglion cells in the periphery appeared to be approximately matched by an increase in the size of their axons. Larger axons became myelinated farther from the edge of the myelinated band than did smaller axons

Within the ganglion cell layer there was another population of cells which were quite distinct from the obvious neuroglia: Their nuclei were similar to those of the larger ganglion cells and many appeared to have Nissl granules within their limited cytoplasm. About half of this heterogeneous population was classified as “coronate cells,” which were characterized by the partial nuclear encapsulation of their eccentric cytoplasm.
Somatic sensory cortex (SmI) of the prosimian primate Galago crassicaudatus: Organization of mechanoreceptive input from the hand in relation to cytoarchitecture
Authors: Carlson Mary , Welt Carol
Published: January 2005

Mechanoreceptive input from the hand to the somatic sensory cortex (SmI) of the prosimian primate Galago crassicaudatus was examined with microelectrode mapping methods. In anesthetized animals, low threshold cutaneous input from the hand projects to SmI cortex in a single, complete, somatotopically organized pattern. Within this single pattern, cells with receptive fields on the glabrous skin of the palm, digits and digit tips are located in the rostral half, and cells with RFs on the hairy skin of the dorsal hand and digits are located in the caudal half of the hand area. The cutaneous hand area is coextensive with the densely granular architectonic region of SmI.

Studies of single cells in this region of awake galagos reveal the same pattern of cutaneous input and, in addition, demonstrate the presence of cells responding to joint movement not detected in anesthetized animals. Cells responsive to joint movement are arranged in vertically oriented columns located adjacent to cutaneous columns with receptive fields on the same part of the hand.

In anesthetized animals, cells rostral to the granular region, in an area typified by increasing numbers of pyramidal cells in layer V and decreasing numbers of granular cells in upper layers, respond to high threshold stimulation of large areas of the hand. The few cells isolated in this area in awake animals respond to either active or passive hand movements. In such animals, cells caudal to the granular region, in an area characterized as agranular and alaminar cortex, respond to either passive stimulation of single or multiple joints or to active hand movements.

These results, together with similar findings in a related prosimian, Nycticebus coucang, emphasize the generality of a single cutaneous hand area in SmI of prosimian species. The demonstration of multiple hand areas corresponding to multiple cytoarchitectonic subdivisions in SmI of Old and New World simians illustrates the increased degree of SmI differentiation from the prosimian to the simian grade of organization. The present results further suggest that determination of the homologues of multiple areas or subdivisions within and surrounding SmI in primates will require comparisons of somatotopy, submodality, sulcal patterns, cytoarchitecture, and connectivity in representative members of prosimian and simian families.
Rohon‐beard cells and other large neurons in Xenopus embryos originate during gastrulation
Authors: Lamborghini Janet E.
Published: January 2005

The time of origin (birthday) of Rohon‐Beard cells in Xenopus laevis was studied by 3H‐thymidine autoradiography. Rohon‐Beard cells were selected because they are a morphologically identifiable population of neurons in which the development of chemical and electrical excitability has been studied. A single injection of a radioactive DNA precursor was given to animals in successive stages of development from blastula to late tail bud (Nieuwkoop and Faber stages 8–33/34). The label was available throughout the stage of injection and longer. The labeling pattern was examined when animals had reached stage 42, when Rohon‐Beard cells are easily recognized. All neurons including Rohon‐Beard cells were labeled in animals injected with 3H‐thymidine before stage 10 1/2 (early gastrula). Unlabeled Rohon‐Beard cells were observed in animals injected with 3H‐thymidine in and after stage 10 1/2. The percentage of unlabeled Rohon‐Beard cells increased as development progressed. About 80% were born by the completion of gastrulation (stage 13). The other ∼20% were born during neurulation and early tail bud stages. By stage 27, no Rohon‐Beard neuron incorporated 3H‐thymidine. In addition to Rohon‐Beard neurons, five other neuronal populations begin generation during gastrulation: Mauthner neurons (Vargas‐Lizardi and Lyser, '74), trigeminal ganglion cells, large basal plate cells of the medulla, extramedullary neurons, and primary motor neurons. The first birthdays in any of the six populations are temporally close to but appear to be independent of the others.
Development of the dorsal lateral geniculate nucleus in normal and visually deprived cats
Authors: Hickey T. L.
Published: January 2005

Although much is known about the cell size changes that take place in the cat dorsal lateral geniculate nucleus as a result of visual deprivation, very little is known about the time course of either of these changes or the changes that occur during normal development. In addition, all previous studies of lateral geniculate nucleus cell size have been confined to the dorsal laminae A and A1 since the more ventral “C” laminae are impossible to identify in normal Nissl stained material. However, it is possible to extend the cell measurement data to laminae C, C1, and C2 by using autoradiographic techniques.

Cross‐sectional area measurements of dorsal lateral geniculate nucleus cells were made in 47 normally reared kittens and 45 monocularly deprived kittens. All of the normal kittens and 39 of the 45 deprived kittens were studied during the first 70 days of postnatal life. Six deprived cats used to study the deprivatin induced changes in cell size in the “C” laminae were allowed to survive for longer periods.

In normal kittens, lateral geniculate nucleus cells grow rapidly during the first four weeks of life. Cells in the deprived layers also grow rapidly during this time, however, at the end of the first month their growth stops and a slow shrinkage takes place over the next several weeks. In the ‘C’ laminae of deprived cats significant changes in cell size are confined to layer C.

Although many of the deprived cats show greater deprivation induced changes in cell size in the binocular segment of the lateral geniculate nucleus than in the monocular segment, other cats show approximately equal changes in cell size in the two regions. In addition, some cats exhibit little, if any, deprivation induced change in lamina A cell size but do show quite severe cell shrinkage in lamina A1.
Subcortical afferents to the hippocampal formation in the monkey
Authors: Amaral David G. , Cowan W. Maxwell
Published: January 2005

The distribution of neurons in the basal telencephalon, the diencephalon, and the brainstem that project to the hippocampal formation has been analyzed in mature cynomolgus monkeys (Macaca fascicularis) by the injection of horseradish peroxidase into different rostro‐caudal levels of the hippocampal formation. After injections which involve Ammon's horn, the dentate gyrus, and the subicular complex, retrogradely labeled neurons are found in the following regions: in the amygdala (specifically in the anterior amygdaloid area, the basolateral nucleus, and the periamygdaloid cortex); in the medial septal nucleus and the nucleus of the diagonal band; in the ventral part of the claustrum; in the substantia innominata and the basal nucleus of Meynert; in the rostral thalamus (specifically in the anterior nuclear complex, the laterodorsal nucleus, the paraventricular and parataenial nuclei, the nucleus reuniens, and the nucleus centralis medialis); in the lateral preoptic and lateral hypothalamic areas, and especially in the supramammillary and retromammillary regions; in the ventral tegmental area, the tegmental reticular fields, the raphé nuclei (specifically in nucleus centralis superior and the dorsal raphé nucleus), in the nucleus reticularis tegmenti pontis, the central gray, the dorsal tegmental nucleus, and in the locus coeruleus.
Immunocytochemical localization of enkephalin in the neostriatum of rat brain: A light and electron microscopic study
Authors: Pickel Virginia M. , Sumal Khushdev K. , Beckley Susan C. , Miller Richard J. , Reis Donald J.
Published: January 2005

The peroxidase‐antiperoxidase (PAP) immunocytochemical technique was used to determine the light and electron microscopic localization of antisera directed against either methionine [Met5]‐ or leucine [Leu5]‐enkephalin in the neostriatum of brains from untreated rats. By light microscopy, neuronal perikarya and processes showing enkephalin‐like immunoreactivity (ELI) were unevently distributed throughout the neostriatum. The greatest accumulation of neuronal structures showing ELI was in the ventro‐ and caudo‐ lateral portions of the nucleus. The labeled perikarya measured 10–15 μm in diameter and constituted about 15–20% of the total neurons in the enostriatum. By electron microscopy, examination of three areas from horizontal and coronal sections revealed no regional differences in types of neurons showing ELI or in their synaptic organization. All labeled neurons showed a relatively low intensity reaction product which was diffusely distributed throughout the perikarya and dendrites. The cytoplasm contained relatively few organelles, which included mitochondria, endoplasmic reticulum and numerous “alveolate” vesicles. The dendrites had many spiny processes which formed asymmetric synapses with unlabeled axon terminals containing all small clear vesicles. In contrast to the perikarya and dendrites a dense accumulation of reaction product was present in a few myelinated and numerous unmyelinated axons and axonal varicosties. Approximately 75% of the labeled varicosities did not form a specialized synaptic junction in a single plane of section. The remaining 25% of the labeled terminals formed asymmetric junctions primarily with unlabeled dendrites and rerely with unlabeled perikarya or axons. The morphology and synaptic relations of the neurons showing ELI suggest that they may belong to the general group of medium‐sized spiny cells characterized in Golgi studies by Kemp and Powell ('71a). At least some of the peptide‐containing neurons may also have a myelinated efferent axon.
Development of the hippocampal region in the rat II. Morphogenesis during embryonic and early postnatal life
Authors: Bayer Shirley A.
Published: January 2005

Morphogenesis of the entire hippocampal region was examined in normal rats from embryonic (E) day E10 to E22 and on postnatal (P) days P1, P7, and P21, and was correlated with autoradiographic datings (Bayer, '79c). This region is postulated to form from two connected primordia in the telencephalon, easily recognizable on E16. One lies in the dorsomedial wall and generates a portion of the subiculum, Ammon's horn and the dentate gyrus. The other lies in the dorsoposterior wall and generates the entorhinal cortex and part of the parasubiculum and presubiculum. A cortical plate appears in the presumptive entorhinal region on E17; a cell‐sparse fibrous zone appears in the middle of the cortical plate on E19. Lamination in the entorhinal cortex proceeds from lateral to medial and from deep to superficial, with the thickening of layer III being the last to appear on E22. Lamination in the subiculum starts on E18, but the distinction between superficial laminae in the para‐ and presubiculum cannot be made until E22. The stratum pyramidale is small on E20 in presumptive Ammon's horn, then greatly lengthens between E21‐P1. In early dentate gyrus development, cells migrate from the neuroepithelium near the outgrowth of the fimbria and adjacent to the choroid plexus toward a subpial location. The ectal limb of the granular layer appears at the two extremes of the dentate gyrus on E20; the endal limb apears perinatally and develops rapidly to become morphologically similar to the ectal limb by P7.

A volumetric analysis of growth in Ammon's horn (including a portion of the subiculum), dentate gyrus, fimbria, and fornix was made from E15 to P21. The neuroepithelium increases to a peak volume on E18 and disappears by P1. The subependymal zone becomes distinct on E18, reaches a peak volume on E20 and disappears by P7. Rapid rates of growth in the stratum oriens and strata radiatum, lacunosum‐moleculare occur between E16‐E17 and between E22‐P1. The pyramidal layer grows rapidly between E18‐E19 (presumptive subicular pyramids) and between E22‐P1 (presumptive Ammon's horn pyramids). Growth rates of the dentate hilus are rapid prenatally and decline postnatally, while dentate granular and molecular layers maintain high postnatal growth rates. The fimbria and fornix have early (E18‐E19) and late (E21‐E22) spurts of growth.

To accurately locate regions of primitive migratory and mitotic cells within each lamina of Ammon's horn and the dentate gyrus, the number of cells surviving a single exposure to 200 R X‐rays in embryonic brains (E15‐E22) were compared with controls. The neuroepithelium increases its radioresistance from E15‐E21 and reaches control levels by E22; the subependymal zone is highly radiosensitive throughout development. In contrast, radioresistance in the stratum oriens and dentate hilus declines and reaches a low point on E20. Over 70% of the cells in the strata pyramidale, radiatum, lacunosum‐moleculare, and dentate granular layer are radioresistant throughout development.
Ultrastructure of HRP‐identified sympathetic preganglionic neurons in cats
Authors: Chung Kyungsoon , La Velle F. W. , Wurster R. D.
Published: January 2005

Electron microscopic studies were conducted on cat sympathetic preganglionic neurons which were labeled using retrograde transport of horseradish peroxidase from the injection site in the stellate ganglion to somas in the thoracic spinal cord. Based on size, the identified somas were divided into two groups: large multipolar somas (25–35 μm), usually having three dendrites with a mean diameter of 8 μm, and small fusiform somas (12–24 μm), with two primary dendrites with a mean diameter of about 4 μm. The ultrastructures of the perikarya and dendrites were similar to other spinal neurons. Three types of terminals were identified: 1) round asymmetric terminals, 2) pleomorphic symmetric terminals, and 3) round symmetric terminals. On the soma, pleomorphic terminals were more numerous than round asymmetric terminals. On the dendrites, the density of round asymmetric terminals was similar to plemorphic symmetric terminals. Round symmetric terminals represent only a small percent on either the soma or dendrites. Because of the greater total density of terminals on the dendrites than soma, pleomorphic symmetric and round asymmetric terminals are primarily located on the dendrites. Very few dense‐core vesicles characteristic of monoamine terminals were observed, perhaps due to the fixative used.
Efferent projections of the deep mesencephalic nucleus (pars lateralis) in the rat
Authors: Veazey R. B. , Severin C. M.
Published: January 2005

The projections of the lateral part of the deep mesencephalic nucleus (DMN) were traced by autoradiography and retrograde horseradish peroxidase (HRP) techniques. At the level of the DMN, projections from its lateral part crossed the midline and terminated in the medial and lateral part of the contralateral DMN. Furthermore, two labeled tracts passed rostrally from the lateral part of the DMN. One tract coursed dorsolaterally from the lateral DMN to terminate in the ipsilateral lateral thalamic nucleus. The second tract coursed ventrally and rostrally over the substantia nigra toward the ipsilateral zona incerta. At the caudal part of the zona incerta these fibers divided into two bundles. One bundle coursed superiorly to terminate bilaterally in the mediodorsal nucleus of the thalamus. The second bundle of fibers passed anteriorly to enter the ipsilateral zona incerta. Some of these fibers terminated upon neurons of the zona incerta and the ventromedial part of the subthalamic nucleus. The remaining fibers within the zona incerta coursed anteriorly to enter the internal capsule. These fibers terminated in the entopeduncular nucleus and medial part of the globus pallidus. These findings indicate that the lateral part of the DMN is likely to be involved in the ascending activating system of the reticular formation by connections with thalamic nuclei. Furthermore, the lateral part of the DMN may play a part in suprasegmental motor control via connections with rostral brain stem motor centers.
Strain‐specific variations in the folial pattern of the mouse cerebellum
Authors: Inouye Minoru , Oda Sen‐Ichi
Published: January 2005

The folial pattern of the mouse cerebellum was compared in 13 inbred strains and a closed colony. The morphological variation of the cerebellum among individual animals was slight within each inbred strain, whereas it was marked in the closed colony. There was no sex‐related difference in the cerebellar folial pattern. The cerebellum of mice from each inbred strain presented a characteristic folial pattern in which some similarties were recognized among animals from genetically related strains. These findings revealed that the morphological variation in the folial pattern of the cerebellum was strain‐specific in mice and had an intimate connection with the genetic control.
Central origins of cranial nerve parasympathetic neurons in the rat
Authors: Contreras Robert J. , Gomez Maximo M. , Norgren Ralph
Published: January 2005

The location of central neurons that contribute preganglionic parasympathetic axons to cranial nerves VII, IX, and X in rats has been identified using horseradish peroxidase (HRP) tracting methods. Collectively, these neurons form an uniterrupted dorsal column that extends over the entire length of the medulla. The cephalic end of this column turns ventrally with neurons scattered in the parvicellular reticular formation between the rotral pole of the nucleus of the solitary tract (NST) and the facial motor nucleus. Applying HRP crystals to the cut cervical vagus labels neurons in the classically defined dorsal motor nucleus. Rostrally, this distribution continues along the medial edge of NST, ending just caudal to neurons exiting in the lingual‐tonsilar branch of IX. At the rostral pole of the NST and ventral to it, neurons occur that serve the lingual‐tonsilar and tympanic branches of IX, as well as the chorda tympani and greater superficial petrosal (GSP) branches of VII. Central neurons of the chorda tympani and tympanic nerves spread ventrally from NST into a sparse but largely coextensive distribution in the reticular formation lateral to the ascending radiations of the facial motor nucleus. Immediately ventral to this distribution, a dense accumulation of GSP efferent neurons appears rostrolateral to the facial motor nucleus. Although they vary considerably in number and packing density, the neurons of the dorsal efferent column and those extending from it into the reticular formation have similar morphological characteristics. The somata are medium‐sized, fusiform, or multipolar, but with usually no more than five or six major processes.
The thalamocortical projection in Pseudemys turtles: A quantitative electron microscopic study
Authors: Smith Leslie M. , Ebner Ford F. , Colonnier Marc
Published: January 2005

Thalamic fibers in the cortex of Pseudemys turtles were studied with the electron microscope to determine the type of synaptic vesicle they contain, the type of membrane differentiation they form, and the type of processes they contact. Following unilateral removal of the thalamus, all degenerating thalamic axon terminals are located in the outer third of the molecular layer in the rostral half of general cortex. In the middle of this zone they constitute as much as 25% of all vesicle‐containing profiles. The degenerated terminals appear as electron opaque profiles, most commonly with a uniform opacity. They contain round agranular vesicles and form synapses with asymmetrical membrane differentiations. They synapse mainly on dendritic spines containing mitochondria and/or membranous sacs, although some thalamic fibers contact small clear spines, dendrites, and, rarely, cell bodies. Counts show that 86% of degenerated contacts are on dendritic spines and 14% on dendritic shafts. The spines probably all belong to the dendrites of the pyramidal cells, whose somata are located in the deep cellular layer. The dendritic shafts and somata are most likely those of the aspinous stellate neurons located in the molecular layer. Although these stellate cells are not sufficiently numerous to form a cell “layer,” each transverse section through thalamic recipient cortex contains about nine of these cells and they occur in a ratio of 1:37 to pyramidal cells in the underlying main cell layer. We have calculated that in a rectangular solid of turtle cortex whose dimensions are 1 mm × 1 mm × the depth from pial surface to the underlying ventricle, there are 5.2 million thalamic fiber contacts (all in the outer 100 μm), 15,000 pyramidal neurons in the main cell layer, and 400 stellate cells in the molecular layer. Of the 5.2 million thalamic synapses, 0.7 million contact stellate cells and 4.5 million contact pyramidal cells. Thus each stellate cell in the molecular layer receives on the average 1,800 thalamic fiber contacts, while each pyramidal cell receives only 300 thalamic fiber synapses on the distal portion of its dendrites. The calculations lead to the conclusion that individual stellate cells receive at least six times more thalamic fiber synapses than individual pyramidal cells in turtle cortex. We suggest that the stellate cells in the thalamic input zone are inhibitory and that each thalamic volley not only excites efferent pyramidal cells but is also a powerful activator of inhibitory interneurons.
Selective retrograde labeling indicating the transmitter of neuronal pathways
Authors: Streit P.
Published: January 2005

A number of tritiated transmitter related compounds—amino acids and biogenic amines—were injected into the rat caudoputamen or substantia nigra in order to test (1) for the occurence of autoradiographic perikaryal labeling, (2) for a selectivity of perikaryal labeling relating certain compounds to certain pathways, and (3) for the relation of perikaryal labeling to known transmitter specificities of the systems involved. Perikaryal labeling was observed after injection of some but not all of the substances used and was best explained by retrograde labeling in pathways projecting to the injection sites. Six hours after injection of high concentrations of tritiated transmitter into the terminal area, perikaryal labeling was observed: (A) in substantial nigra compacta (A9), A10 (rostral) and A8 (all heavy), and in n. raphe dorsalis (light) after [3H]‐dopamine and [3H]‐norepinephrine injection into caudoputamen; (B) same pattern as in A, but heavy in n. raphe dorsalis after [3H]‐serotonin injection into caudoputamen; perikaryal labeling absent in cortex and thalamus after injection of substances mentioned in A and B; (C) only in substantia nigra compacta (minimally) after [3H]‐GABA injection into caudoputamen; (D) in cerebral cortex and thalamus but not in substantia nigra, A10, A8, nor in n. raphe dorsalis after injection of [3H]‐D‐aspartate into caudoputamen; (E) in the rat caudoputamen but not in n. raphe dorsalis after [3H]‐GABA injection into substantia nigra; (F) in n. raphe dorsalis but not in caudoputamen after [3H]‐serotonin into substantia nigra.

These results indicated, indeed, a certain selectivity—partly related to transmitter specificity—for perikaryal labeling patterns. As a method, transmitter specific retrograde tracing could be useful in pathways with dopamine‐, serotonin‐, and GABA‐mediated synaptic transmission.
Ascending projections of the inferior colliculus in the cat: An autoradiographic study
Authors: Kudo Motoi , Niimi Kahee
Published: January 2005

The ascending projections of the inferior colliculus (IC) in the cat were traced by the autoradiographic method, with special reference to the differential projections of each subnucleus of IC.

The laminated ventrolateral part of the central nucleus of IC (CNv) projects to the ventral and medial divisions of the ipsilateral medial geniculate body (MGB). The projections to the ventral division are topographically organized in the mediolateral direction, the terminals being arranged in the form of lamina, while those to the medial division are diffuse. The unlaminated dorsomedial part of the central nucleus of IC (CNd) sends fibers to every division of the ipsilateral MGB, particularly to the dorsal division and the ventromedial portion of the ventral division. It is noteworthy that the external nucleus of IC (EN) projects to the superior colliculus, part of the pretectum, and the anterior extremity of MGB ipsilaterally, in addition to the ventral and medial divisions of MGB. The posterior cap of IC, regarded as the pericentral nucleus of IC (PC), projects ipsilaterally to the ventral part of the caudal tip of MGB and the posterior part of the suprapeduncular nucleus. In addition to these projections, the parabrachial region and interstitial nucleus of the brachium of IC (BIC) are identified as common targets of projections of each nucleus of IC on the ipsilateral side. Contralaterally, every subnucleus of IC except for PC projects via the commissure of IC to areas corresponding to the targets of the ipsilateral projections, such as the ventral and medial divisions of MGB and the parabrachial region and the interstitial nucleus of BIC, although these contralateral projections are in general much sparser than those ipsilateral. Intrinsic and commissural connections within IC are also revealed in this study, providing characteristic configurations of each subnucleus of IC.

It is concluded that the ascending projections of IC in the cat are highly differentially organized according to its subnucleus.
Estrogen target cells in the forebrain of river lamprey, ichthyomyzon unicuspis
Authors: Kim Ye Soon , Stumpf Walter E. , Reid Frederic A. , Sar Madhabananda , Selzer Michael E.
Published: January 2005

Estrogen‐concentrating cells in the brain of river lamprey, Ichthyomyzon unicuspis, are identified and mapped by thaw‐mount autoradiography. After injection of 3H–estradiol–17β, cells with nuclear concentration of radioactivity are found in the ventral periventricular area of the telencephalon, and in preoptic, central hypothalamic, and thalamic regions of the diencephalon, while in the pallium no such target cells are found. Injection of unlabeled estradiol prior to the administration of 3H–estradiol reduces or eliminates the nuclear concentration of radioactivity.

The autoradiographic results demonstrate the presence of estrogen target cells in the brain of descendents of one of the phylogenetically earliest vertebrate lines. The topographical distribution of these target neurons, which are accumulated in certain periventricular structures, is similar to the distribution of estrogen target neurons described previously for other nonmammalian and mammalian vertebrates. Accordingly, estrogen feedback and activation sites are present throughout vertebrate phylogeny.
Central representation and somatotopic organization of the jaw muscles within the facial and trigeminal nuclei of the pigeon (Columba livia)
Authors: Wild J. Martin , Zeigler H. Philip
Published: January 2005

The location of facial and trigeminal brainstem motoneurons innervating the jaw muscles of the pigeon has been determined, using the technique of retrograde transport of horseradish peroxidase. Trigeminal motoneurons innervating the jaw closing muscles are located within the classically defined main trigeminal motor nucleus, and their organization exhibits approximately a mediolateral somatotopy. Trigeminal neurons innervating the opener muscle of the upper jaw are also located in the main trigeminal motor nucleus, but comprise a dorsomedial subnucleus which is continuous caudally with the dorsal facial nucleus whose neurons innervate the opener muscle of the lower jaw. The Vth and VIIth motor nuclei are thus linked in the rostrocaudal plane. The representations of other head muscles are arranged in a dorsoventral manner within the V–VII motor complex, with the lower eyelid muscle represented most dorsally and the hyoid and superficial neck muscles most ventrally.

Jaw closing muscles were well represented in both the Gasserian ganglion and trigeminal mesencephalic nucleus. No such representation was found for either of the jaw opening muscles. The HRP data indicate that the V–VII motor complex in birds is far more extensive than has previously been suggested.
Tonotopic organization in auditory cortex of the cat
Authors: Reale Richard A. , Imig Thomas J.
Published: January 2005

Microelectrode mapping techniques were employed in the cat's auditory cortex to relate the best frequencies of a large population of neurons with their spatial loci. Based upon the best‐frequency distribution, the auditory region was divided into four complete and orderly tonotopic representations and a surrounding belt of cortex in which the tonotopic organization was more complex. The four auditory fields occupy a crescent‐shaped band of tissue which comprises portions of both the exposed gyral surfaces and sulcal banks of the ectosylvian cortex. The anterior auditory field (A) is situated most rostrally upon the anterior ectosylvian gyrus. It extends upon the ventral bank of the suprasylvian sulcus and upon the banks of the anterior ectosylvian sulcus. Adjoining field A caudally is the primary auditory field (AI), which extends across the middle ectosylvian gyrus and portions of both banks of the posterior ectosylvian sulcus. The representations of the highest best frequencies in fields A and AI are contiguous. Caudal and ventral to AI are located the posterior (P) and ventroposterior (VP) auditory fields. They lie mainly upon the caudal bank of the posterior ectosylvian sulcus but also extend upon the rostral bank and upon the posterior ectosylvian gyrus. The low best‐frequency representations of fields AI and P are contiguous, whereas the low best‐frequency representation of field VP lies near the ventral end of the posterior ectosylvian sulcus. Fields P and VP are joined along their middle and high best‐frequency representations. Within each auditory field isofrequency lines defined by the spatial loci of neurons with similar best frequencies are oriented orthogonal to the low‐to‐high best‐frequency gradients.