bluuebunny/crossref_metadata_2025 huggingface dataset:
A brainstem atlas of catecholaminergic neurons and serotonergic perikarya in a pygmy primate (Cebuella pygmaea)
Authors: Jacobowitz David M. , MacLean Paul D.
Published: January 2005

The present paper provides a brainsem atlas showing the disribution of catecholaminergic cells and processes, as well as serotonergic perikarya, in the pygmy marmoset. The findings revealed by the Falck and Hillarp histofluorescence method conform in essential details to what has been described in rodents. These and other comparative data indicate that a prototypical pattern of organization of aminergic systems has been retained in the evolution of primates.
The distribution of substance P immunoreactive fibers in the rat central nervous system
Authors: Cuello A. Claudio , Kanazawa Ichiro
Published: January 2005

A detailed account of the distribution of immunoreactive substance P‐containing structures in the rat central nervous system is presented, from results obtained by applying an indirect immunofluorescent technique. High densities of substance P‐containing nerve terminals were present in sensory nuclei and other non‐sensory structures such as thalamus, hypothalamus and extrapyramidal system. Substance P‐reactive neuron cell bodies were present in spinal root ganglia, nucleus habenulae medialis, nucleus interpeduncularis, caudoputamen and globus pallidus. Most of the neocortex and the cerebellar cortices had no substance P‐positive elements. The results support the hypothesis that substance P may be a widespread neurotransmitter in the central nervous system.
Depth‐marking in the proximal negative response in the pigeon retina
Authors: Hayes B. P. , Holden A. L.
Published: January 2005

The depth distribution of proximal negativity in the pigeon retina was investigated with a dye‐marking technique. Proximal negativity is recorded in three stages as the retina is penetrated. At the near the surface (level 1) the response is small and phasic: next, during “level 2” the on response exceeds the off response in amplitude: then, at “level 3” the off response exceeds the on response in amplitude. The dye marks were located in thin light microscope sections; they were about 20 μ in diameter, and were associated with larger areas of tissue damage. Level of 3 dye marks were centred at the middle of the inner plexiform layer, and level 2 dye‐marks were distributed more proximally. The amplitude maxima of the PNR are close to the middle of the inner plexiform layer, and are separated by approximately 15 μm.
Golgi studies on Purkinje cell development in the frog during spontaneous metamorphosis I. General pattern of development
Authors: Uray Náandor J. , Gona Amos G.
Published: January 2005

The development of Purkinje cells was studied in the bullfrog from prometamorphic tadpoles to 10‐week‐old postmetamorphic froglets by the Golgi‐Kopsch method. In this species, the rate of Purkinje cell development is unusually slow and proceeds in two waves. The first wave of development begins prior to the establishment of the external granular layer (EGL), and proceeds slowly for two to three months during the formation of the EGL; then accelerating as metamorphosis is being completed, the cells reach near‐adult dimensions a month later. Even prior to the formation of the EGL these cells are already present in the stage of dendritic orientation and flattening which, however, varies from the norm. The second wave of Purkinje cell development begins during metamorphosis and proceeds at a more rapid pace until two months after metamorphosis, at which time they appear to have reached adult dimensions. In these cells the development of the apical dendrite does not always coincide with the stellate stage but may proceed directly to the stage of dendritic orientation and flattening which, in accordance with the norm, is towards the pia and in the sagittal plane.

Many variations are present in the dendritic trees and orientation of the dendritic branches of Purkinje cells throughout their development. These variations are similar to those seen in mammals, however, since the frog cerebellum consists of a simple plate, they cannot be attributed to a Cartesian transformation of dendrites to accommodate the curvatures of a folial pattern. Similarly, since these morphological variations occur in the course of normal development they cannot be attributed to a reaction to, or recovery from, injury during development.
The effects of dark rearing on the development of the visual cortex of the rat
Authors: Borges S. , Berry M.
Published: January 2005

The effects of dark rearing on the development of the visual cortex has been studied in Wistar rats, as have the effects of subsequent light exposure on recovery. Five groups of animals were used: (1) light exposed until 30‐40 days post partum (dpp) (2) dark reared until 30‐40 dpp (3) dark reared until 80‐120 dpp (4) dark reared to 21 dpp, then light exposed until 40 dpp (5) light exposed to 21 dpp and then dark reared until 40 dpp. Golgi‐Cox impregnations of layer IV stellate cell dendritic fields were analysed and total neuronal and glial counts were also done within layer IV of the primary visual cortex.

Normal visual stellate cell dendritic fields were radially organised, with the highest dendritic density being recorded below the soma. In short term visually deprived animals and in those exposed only for 21 dpp and then reared in light until 40 dpp the radial distribution of dendrites was maintained but the peak density shifted to above the soma. In all other experimental groups this abnormal polarisation was still present but not as marked. Measurement of branching indices suggested that these field changes resulted from increased branching and growth in the superficial domain and not from the reorientation of dendrites. Differential glial counts revealed a significantly higher number of microglia in dark reared animals than in controls. Neuronal numbers were not affected.
Sequence of neuron origin in experimentally distorted brains of chick embryos
Authors: Wilson Doris B.
Published: January 2005

The effects of proliferative disorders on the time and sequence of neuron origin in the optic tectum were studied in chick embryos in which “overgrowth” had been experimentally induced. Sixteen normal and fourteen abnormal embryos ranging in age from four through ten days of incubation were each given a single dose of thymidine[3H]. Comparisons were then made between 16‐day normal and abnormal chick embryos with respect to the distribution of unlabeled and labeled neurons in the dorsolateral regions of the optic tectum midway between its rostral and caudal boundaries. In the normal and abnormal tecta layers I‐IV were generated on days 3–6. Differences occurred in the generation of the remaining layers. In the normal embryos layers V‐VII arose on days 5–8 and layers VIII‐XV on days 4–7; in the abnormal embryos layers V‐VII originated on days 6–8 and layers VIII‐XV on days 5–8. In addition to the delay in onset of neuron origin, the abnormal tectum also showed distorted lamination, particularly in layers VIII‐XV which constitute the superficial regions of the stratum griseum and fibrosum superficiale. Despite the defect in time and sequence of neuron origin, the rostroventrolateral to caudodorsomedial gradient of maturity characteristic of the normal tecta was not disturbed in the abnormal tecta.
Retrograde responses of developing lateral motor column neurons
Authors: Decker Robert S.
Published: January 2005

Removing the right hind limb of Rana pipiens larvae at different stages during development initiates diverse responses within lateral motor column (LMC) neurons whose axons have entered the limb and are forming neuromuscular junctions. Severing the hind limb at stage V inhibits the future differentiation of LMC neurons and, ultimately, 95% of the presumably injured cells degenerate. Ultrastructural observations indicate that the affected neurons become pyknotic, but display little evidence of lysosomal involvement. However, a quite different reaction is encountered when limb ablation is delayed to stage X. At this stage, LMC neurons rapidly disclose an intense retrograde response, which includes the genesis of numerous secondary lysosomes in degenerating cells. If, however, limb removal is postponed until stage XV or XX then a classic chromatolysis can be recognized in axotomized neurons. The intensity of the chromatolysis appears to be inversely related to the age of the neurons. This investigation tends to support the premise that differentiating LMC neurons pass through three crucial stages in their development which can be identified following axotomy.
Projections to the visual cortex in the golden hamster
Authors: Dürsteler M. R. , Blakemore Colin , Garey L. J.
Published: January 2005

Retrograde transport of horseradish peroxidase (HRP) was used to determine the origins of afferent connexions to the visual cortex (areas 17, 18a and 18b) in the hamster. The distribution of neurons projecting to the visual cortex from other cortical areas, from the thalamus and from the brainstem was studied using a computer technique for three‐dimensional reconstruction.

There is a topographically organized projection from the dorsal lateral geniculate nucleus to area 17, but probably to no other of the areas studied. The lateral posterior nucleus of the thalamus (LP) projects to area 18a and weakly to area 17. The lateral nucleus (L) projects to area 18b and also, probably, weakly to area 17. The cortical projections from LP and L are also organized topographically but relatively grossly compared with the geniculo‐cortical pathway.

There are reciprocal association projections between area 17 and areas 18a and 18b. Area 18a projects weakly to 18b. The main commissural connexions of the posterior neocortex are between the area 17/18a boundary zones in the two hemispheres, with little between the bodies of area 17.

Labelled neurons were found bilaterally in the locus coeruleus, more ipsilaterally than contralaterally, after multiple injections into the visual cortex: single, small injections sometimes resulted in the labelling of a single cell body in the locus coeruleus.
Unmyelinated axons in the trigeminal motor root of human and cat
Authors: Young Ronald F. , Stevens Richard
Published: January 2005

The fiber composition of the human and cat trigeminal “motor roots” were studied utilizing the electron microscope. Twelve to twenty percent of fibers in the human trigeminal motor root are unmyelinated whereas 9–15% are unmyelinated in the cat. The only previous examination of the fiber composition of the peripheral trigeminal motor nerve utilized the light microscope and indicated that less than 5% of fibers were unmyelinated in cat. No study of the fiber composition of the motor nerve root is available. The present results are similar to those recently obtained by others for spinal ventral roots. The function of unmyelinated fibers in the trigeminal “motor root” is unknown, however indirect evidence, both laboratory and clinical, suggests a potential sensory function for them. The findings question seriously the concept that the functional separation of the nervous system into motor and sensory systems has anatomical correlates in the spinal and cranial nerve roots. The results relate directly to our conceptualization of the nervous system and also to the design of methods for the treatment of intractable pain.
The organization of afferents to the cerebellar cortex in the cat: Projections from the deep cerebellar nuclei
Authors: Gould Barbara Brown
Published: January 2005

The topography of the cerebellar nucleo‐cortical projection was investigated in the cat by experiments employing the horseradish peroxidase (HRP) technique or by combined HRP‐autoradiographic methods. The results of the HRP studies extend previous findings showing that neurons in the deep nuclei project to the cerebellar cortex in an orderly way. Thus, it appears that the cortex of the vermis‐proper receives projections fron neurons located predominately in the fastigial nucleus. Intermediate and lateral zones of mid‐vermal cerebellar cortex are projected on by neurons located in the interposed and dentate nuclei. Crus II receives input from neurons located predominately in the dentate nucleus, while the paramedian lobule is projected on by neurons located in a large postero‐dorsal sector of the interposed nucleus and in a smaller medial strip of the dentate nucleus. Neurons in the ventral part of the dentate nucleus and the lateral part of the interposed nucleus send fibers to the paraflocculus. The nucleo‐cortical pathway to the flocculus and nodulus arises largely from a population of neurons located in a ventral region stretching from the medial border of the dentate nucleus to the lateral border of the fastigial nucleus.

The results of experiments using the combined HRP‐autoradiographic method show that clusters of neurons in the deep cerebellar nuclei project back to the cerebellar cortical areas from which they receive input, establishing a fairly precise feedback loop between the cerebellar cortex and deep nuclei.
A study of the synaptogenesis in the cerebellar cortex through chronic treatment and immunocytochemistry of β‐Bungarotoxin
Authors: Hirokawa Nobutaka
Published: January 2005

The mechanism of synaptogenesis between dendritic spines of Purkinje cells and parallel fibers in the chicken cerebellum was studied through chronic treatment and immunocytochemistry of β‐Bungarotoxin (β‐BT). Attention was directed to the question of whether the presynaptic specializations (presynaptic vesicular grids composed of presynaptic dense projections and associated vesicles) of the parallel fibers can differentiate in the absence of the Purkinje cells.

Normal cerebella from 18‐day and 21‐day chick embryos, incubated with β‐BT and reacted with HRP‐labeled anti β‐BT guinea pig IgG, showed a positive HRP reaction on Purkinje cells but not on external and internal granule cells. Thus, in chicken cerebellum, β‐BT primarily affects Purkinje cells.

When β‐BT was applied to chick embryos at 3‐day intervals, beginning on the 4th day of incubation, the cerebella were markedly reduced in size and most of the Purkinje cells as well as the nerve fibers in the white matter disappeared between the 18th and the 21st day of incubation. Folia of the 21st day experimental cerebella were irregular in shape and the area of the midsagittal section was one fourth that of the controls. In the 21st day cerebella treated with β‐BT, the majority of Purkinje cells disappear. However, the external granule cells remain intact and showed the usual mitotic activity. The majority of the inner granule cells were normal. Some of the parallel fibers, which display presynaptic vesicular grids, established synaptic contact with stellate cells and the dendritic spines of the few Purkinje cells that survived the treatment. However, vast areas of the molecular layer contained neither dendrites of Purkinje cells, nor parallel fibers displaying presynaptic vesicular grids devoid of their postsynaptic counterpart. In such areas, the molecular layer consisted of parallel fibers of uniform diameter, some of which contained accumulations of vesicles, but displaying no presynaptic dense projections. This suggests that parallel fibers may not be able to completely develop the presynaptic vesicular grids in the absence of their target cells.
Two modes of cutaneous reinnervation following peripheral nerve injury
Authors: Devor M. , Schonfeld D. , Seltzer Z. , Wall P. D.
Published: January 2005

The return of sensation to the foot following sciatic nerve crush injury was analyzed behaviorally and electrophysiologically in the rat. Functional recovery begins within four days. Its early phase is accounted for by expansion of the functional distribution of intact neighboring fibers of the saphenous n. It occurs even if the sciatic n. is ligated, and it disappears with section of the saphenous n. Accompanying this functional expansion we began to encounter in electrophysiological recordings from the saphenous n., fibers with unusually large receptive fields (RF's) extending onto the plantar surface of the foot, well beyond their limits in intact rats. All of the expanded RF's were high threshold mechanoreceptors. On about the twentieth day after crushing, the regenerating sciatic n. began to make a functional contribution. This was seen by return of sensation to zones not invaded by the saphenous n. and by the onset of sensation in rats in which the saphenous n. had previously been ligated. With return of the sciatic n. the expanded distribution of the saphenous n. went back to its original boundaries. Correspondingly, we could no longer find expanded saphenous n. RF's. We conclude that cutaneous reinnervation begins with the collateral expansion of high threshold afferents from intact neighboring nerves. This alien innervation is later replaced upon regeneration of the original nerve.
Projections from cortex to tectum in the tree shrew, Tupaia glis
Authors: Casseday J. H. , Jones D. R. , Diamond I. T.
Published: January 2005

Sensory neocortex of the tree shrew was divided into three main areas: the visual field, the auditory field, and the somatic field which includes motor cortex. Cortical cells which project to the tectum were identified by injecting HRP into superficial or deep layers of the superior colliculus and into various parts of the inferior colliculus. The main result is that these descending projections are well organized according to their origin in the three main sensory fields of the cortex. (1) Auditory field: labeled cells are found only in the core or auditory koniocortex, after injections of HRP in the pericentral area of the inferior colliculus; labeled cells are found in auditory belt areas after injections in posterior parts of the intermediate and deep layers of the superior colliculus, adjacent to the inferior colliculus. (2) Somatic field: labeled cells are also found in the somatic field after injections in the intermediate and deep layers of the superior colliculus, so that auditory and somatic fields probably overlap to some extent. The results do not exclude the possibility that somatic koniocortex has an exclusive target in the intermediate or deep layers of the superior colliculus. (3) Visual field: labeled cells are found only in the core or striate cortex after injections in the superficial layers of the superior colliculus. Labeled cells are found in the visual belt after injections in the rostral parts of the intermediate layers of the superior colliculus. When these results are related to ascending sensory pathways a picture emerges of a series of circuits or loops which interconnect parallel sensory pathways. These loops eventually reach the deep layers of the superior colliculus which of course have indirect access to motor neurons.
Development of abnormal recrossing retinotectal projections after superior colliculus lesions in newborn Syrian hamsters
Authors: So Kwok‐Fai
Published: January 2005

The development of the retinal projections to the roof of the midbrain was studied in Syrian hamsters after right superior colliculus (SC) lesions on the day of birth, using both autoradiographic and degeneration techniques. The dead tissue resulting from the heat lesion is not completely removed until the eighth day after birth. Normally the midline of the SC is defined by a pia‐lined fissure separating the left and right colliculi, but in the animals with early unilateral lesions, the pia at the midline is damaged. When it regrows, together with vascular and other meningeal tissues, it forms a flat tissue bridge across the midline as early as two days after the lesion.

When the axons from the left eye reach the right SC, they encounter the dead tissue and separate into two bundles. One bundle courses over the surface of the dead tissue and one grows underneath it. It is not until the third to fourth day that axons in the dorsal bundle cross the midline, via the tissue bridge, to terminate anomalously in the medial wall of the left SC. When the quantity of such recrossing axons is small, they overlap extensively with the optic tract fibers from the other (right) eye which normally have innervated the entire SC by day 3. However, it appears that as the density of the recrossing axons increases they displace the axons originating in the other eye from the medial wall of the left SC. Thus, eventually fibers from both eyes terminate in the left SC, occupying separate territories with little, if any, overlap.

Axons in the ventral bundle begin to innervate the deep layers of the right SC on day 2. These axons were never observed to recross the midline.

These results indicate that mechanical guidance and axonal segregation dependent on relative densities are two processes that govern the development of retinotectal projections after early SC lesions in hamsters.
Golgi and EM studies of the formation of dendritic and axonal arbors: The interneurons of the substantia gelatinosa of rolando in newborn kittens
Authors: Falls William , Gobel Stephen
Published: January 2005

Golgi studies in newborn kittens show that the two most prevalent interneurons in Rexed's lamina II of the dorsal horn of the medulla, the stalked cell and islet cell (Gobel, 1975a,b, 1978b) form their dendritic arbors in a similar fashion. At birth, both cell types are present in forms ranging from immature, in which numerous short dendrites radiate from the cell body in all directions, to relatively mature in which their dendritic arbors have elongated in specific directions and the adult branching pattern is already evident. During postnatal maturation, many dendrites are lost while only a few go on to lengthen. The unmyelinated axons of both cells are first recognized in forms in which lengthening dendrites have taken on their preferred direction of orientation.

The two parts of Rexed's lamina II, i.e., layers IIa and IIb have already reached their adult mediolateral width at birth and the neuropil has nearly achieved its adult compactness. Space in the compact neuropil for elongating neuronal and astrocytic processes becomes available through the disintegration of many existing dendrites and by an overall fourfold increase in the rostrocaudal length of the dorsal horn of the medulla during postnatal maturation. At birth, the lengthening of the plasma membranes of elongating neuronal and astrocytic processes proceeds as vesicles (addition vesicles) found in aggregates throughout dendrites, unmyelinated axons and astrocytic processes fuse with and become incorporated into the existing plasma membranes.

In addition, many dendrites in layers IIa and IIb are beading up and disintegrating. Within the beads, neurotubules are lost and addition vesicles fuse with each other to form small cavities. These cavities continue to enlarge, hollowing out the beads. The cavities ultimately open to the intercellular space as their membranes fuse with the plasma membrane of the beads. Finally, the beads disintegrate and their plasma membranes fragment. The thread‐like segments between adjacent disintegrating beads shrivel until they ultimately disappear. Disintegration of beaded dendrites results in very little debris and does not provoke a phagocytic glial reaction. The disintegration of a dendritic branch takes place in spite of synaptic input from non‐primary axons and is thought to occur from a failure to establish synaptic connections with primary axonal endings.
Rod photoreceptors and scotopic vision in ground squirrels
Authors: Jacobs Gerald H. , Tootell R. B. H. , Fisher Steven K. , Anderson Don H.
Published: January 2005

Ground squirrel retinas contain a relatively small complement of rods (5–10% of all photoreceptors) which are thought to provide the basis for a weak scotopic visual capacity. In a previous investigation of the California ground squirrel (Spermophilus beecheyi) involving the recording of a retinal gross potential, the electroretinogram (ERG), electrophysiological evidence for a viable scotopic signal could be obtained from some, but not all of the ground squirrels examined. To further pursue the possibility that there is a structural/functional discrepancy in the relationship between rod photoreceptors and scotopic vision in the ground squirrel, several experiments involving electrophysiological, behavioral, and anatomical observations have been conducted. We found that although about one‐third of the ERGs recorded from a large sample of California ground squirrels lack those characteristics which would indicate the presence of a viable scotopic signal, the retinas of all the squirrels appear to contain the same small population of rod photoreceptors. Additional experiments on the golden‐mantled ground squirrel (Spermophilus lateralis), including behavioral as well as ERG measurements and anatomical observations, lead to this same conclusion.
Rod and cone inputs to bipolar cells in goldfish retina
Authors: Ishida A. T. , Stell W. K. , Lightfoot D. O.
Published: January 2005

Five morphological types of bipolar cells which make synaptic contact with rods and cones are distinguished in the retina of adult goldfish (Carassius auratus) by characteristics readily observable in the light microscope. Cells were designated type a or type b according to whether their axons terminate in the distal part (sublamina a) or proximal part (sublamina b) of the inner plexiform layer, respectively. Analysis of serial semi‐thin sections of Golgiimpregnated cells demonstrates that each subtype of bipolar contacts rods and a characteristic set of chromatic subtypes of cones: types al and bl cells contact rods and red‐sensitive cones, while types a2, b2, and b3 contact rods and red and green‐sensitive cones. Comparison with published descriptions of cells stained with Procion Yellow after intracellular recordings had been made suggests that type a cells should be off‐center types and type b on‐center. Furthermore, it is suggested that the receptive fields of cell types al and bl should be non‐color‐coded, and those of a2, b2, and b3 color‐coded.
Somatotopographic organization in the second somatosensory area of M. fascicularis
Authors: Robinson C. J. , Burton H.
Published: January 2005

The second somatosensory area (SII) of awake, untrained cynomolgus monkeys was surveyed with recordings from nearly 1,000 single neurons. A detailed somatotopographic organization could be demonstrated in SII because the majority of these neurons had contralateral, moderate to well‐defined receptive fields of < 10cm2, and because neighboring neurons possessed receptive fields that were only slightly displaced from one another. Different body regions were represented in successive anterior to posterior strips that were oriented across the parietal operculum with an anterolateral to posteromedial slant. Neurons with trigeminal receptive fields were found in the anterior portion of SII; these neurons were the only ones in SII with predominantly bilateral receptive fields (r.f.'s). Neurons with digit or hand r.f.'s form the largest component of the map, and were located posterior to those with face r.f.s. Most of these neurons had only contralateral activation. The hand and digit region was followed in turn by the arm, the upper and lower trunk, and the hindlimb regions. Although the overall SII orientation was along an anterior‐posterior gradient, recordings at individual coronal planes often demonstrated isolated sequences of receptive fields that exhibited a medial‐lateral progression. The principle example of this latter gradient was seen in the forelimb region where digits one through five were represented in an overlapping sequence across the parietal operculum. Except for portions of the digit representation, neighboring sequences of neurons in SII do not form a precise topologic map of the body that is comparable to the somatotopic maps observed in areas 3b and 1. The present findings contrast with previous physiological studies of SII in the primate. These discrepancies are discussed in relation to methodological differences and in terms of distinctions used to define the boundaries of SII.
Autoradiographic tracing of developing subcortical projections of the occipital region in fetal rabbits
Authors: Distel H. , Holländer H.
Published: January 2005

Thirty rabbit embryos and two neonates (E18‐P1) received micropipette injections of 3H‐Leucine into the occipital region of one hemisphere and were killed after 0.5–5 hours. Incorporated tracer was demonstrated by autoradiography of serial sections of the brains. The first axons were seen in the intermediate zone of the developing cerebral cortex, on day E20, and by day E22 they reached the internal capsule. The entire cortico‐peduncular bundle and a short branch of the superficial (thalamic) bundle were labeled on day E24. On day E25, additional branches directed to claustrum, thalamus (deep bundle), and cerebellum were distinguished. By day E28 the first indications of terminal field development were observed. One day before birth (E30), the neonate pattern of subcortical pathways was fully established and silver grain condensations were present over most of the subcortical target areas.

Subcortically, the axons followed preferentially preexisting fiber tracts. There was a period of at least 2–3 days between the arrival of the supplying bundles at the target sites and the onset of terminal field formation: The axon bundles grew first towards more distal targets, and even beyond, before terminal fields developed proximally. Transient axon bundles reaching the cerebellar paraflocculus and traveling along the pyramidal tract and the external and extreme capsules failed to form terminal fields and disappeared around birth. The data suggest that growth of long axonal tracts and the development of terminal fields are separate phenomena possibly regulated by different mechanisms.
Fluorescence and electron microscopical observations on the amine‐accumulating neurons of the cebus monkey retina
Authors: Dowling John E. , Ehinger Berndt , Florén Ingrid
Published: January 2005

The organization of the Cebus monkey retina was analysed after the intraocular injection of 5,6‐dihydroxytryptamine. This amine was taken up not only by the previously known dopaminergic neurons, but also by a set of indoleamine‐accumulating neurons, whose processes are confined to the inner plexiform layer.

The synaptic contacts of the dopaminergic neurons were analysed in the electron microscope after the processes of the indoleamine‐accumulating neurons were destroyed by the intrvitreal injection of the neurotoxic indoleamine, 5,7‐dihydroxytryptamine. The subsequent injection of 5,6‐dihydroxytryptamine induces certain changes in the dopaminergic neurons which accumulate the substance: electron‐dense cores appear in the synaptic vesicles, and increased electron‐density of mitochondrial and cellular membranes is often observed.

The dopaminergic neurons were found to be presynaptic to amacrine cell perikarya and processes in the inner plexiform layer. In the outer plexiform layer they were presynaptic to both bipolar and horizontal cells, but they did not contact photoreceptors. The dopaminergic neurons received synapses only in the inner plexiform layer, from amacrine cell processes. It is inferred that in Cebus most dopaminergic neurons belong to a special class of retinal neuron, the interplexiform cells, which appear to transmit information centrifugally within the retina, from the inner to the outer plexiform layers. There are considerable similarities between the synaptology of the dopaminergic interplexiform neurons in the Cebus monkey and the goldfish retina, and the function of interplexiform neurons may therefore be similar in these two species.
Neurons in cat lateral geniculate nucleus that concentrate exogenous [3H]‐γ‐aminobutyric acid (GABA)
Authors: Sterling Peter , Davis Thomas L.
Published: January 2005

About one‐quarter of the neurons in the A‐laminae of the cat lateral geniculate selectively accumulate exogenous [3H]‐γ‐aminobutyric acid (GABA), its analog, [3H]‐2,4‐diaminobutyric acid (DABA), and the GABA agonist, [3H] muscimol. These neurons are small (12–18 μm diameter) and lack a laminar body, which suggests that they correspond to the class III cell identified in Golgi material. GABA and DABA are also accumulated by F‐terminals which are post‐synaptic to retinal terminals and presynaptic to relay cell dendrites. It is suggested that GABA may be the transmitter for these small neurons which appear to mediate by means of local circuits a feed‐forward inhibition onto the relay cells.
Identification of early neurons in the brainstem and spinal cord: I. An autoradiographic study in the chick
Authors: McConnell Jo Ann , Sechrist John W.
Published: January 2005

Early stages in chick neurogenesis were investigated with tritiated thymidine (3H‐Tdr) autoradiography to determine the location and identity of the first neurons produced for the central nervous system. These cells have been shown to arise prior to neural tube closure (Sechrist, '75). Chicks were treated at selected intervals between 20 and 72 hours of incubation with 3H‐Tdr in a modified pulse‐labeling technique, and terminated on the 18th day of embryonic development (E18), when neuronal types could be determined. Some of the earliest neurons start their final DNA synthesis before 20 hours of incubation (head process, Hamburger‐Hamilton stage 5). These are primarily medium‐sized cells of the reticular formation in the medulla and at the diencephalic‐mesencephalic junction, but also in the intermediate zone of the spinal cord. Motor neurons of the brainstem and spinal cord begin to appear next, after 26–28 hours incubation; the first sensory neurons arise after 32 hours. Other workers (Ramon y Cajal, '60; Tello, '23; Windle and Austin, '36) found that neurons of the reticular formation were the first to differentiate neurofibrils, during the latter part of E2, indicating that fibrillogenesis in these cells begins about 24 hours after the initial cessation of DNA replication.
Neuromorphometric features and dimensional analysis of the vestibular end organ in the little brown bat (Myotis lucifugus)
Authors: Ramprashad Fred , Landolt Jack P. , Money Kenneth E. , Laufer Jerry
Published: January 2005

Neuromorphometric parameters of the vestibular system were determined from serial sections of temporal bones from four little brown bats. Well‐developed eminentiae cruciatae project from the cristae ampullares of the anterior and posterior membranous ampullae. A total of 4,500 bipolar ganglion cells were enumerated within the vestibular ganglion. The widths of the cell somas varied from 2.5 to 20μm, with 70% of them having widths between 5.0 and 12.5 μm. Two maxima were observed in a curve of ganglion cell density as a function of the length of the ganglion. The first maximum indicated a density of 4,800 cells per mm2 at a length 0.20 mm from the apex of the ganglion (in the pars dorsalis); the second, a density of 4,750 cells per mm2 at 0.38 mm (in the pars ventralis). The morphometric parameters studied were the radii of curvature of the semicircular ducts, the cross‐sectional diameters of the semicircular canals and ducts, the dimensions of the cristae ampullares and their membranous ampullae, and dimensions pertaining to the statoconial organs. Surface areas (measured from graphic projections) were determined as 0.098 mm2 and 0.016 mm2 and hair cell count 500 and 1,300 cells for the saccular and utricular maculae, respectively. The radii of curvature of the three semicircular ducts, R, were dissimilar, with the anterior duct having the largest radius (R = 0.91 mm) and the posterior duct the smallest one (R = 0.91 mm) and the posterior duct the smallest one (R = 0.69 mm). The average crosssectional diameters of the anterior, lateral, and posterior ducts were measured as 0.11 mm, 0.14 mm, and 0.13 mm, respectively. Some of the morphological parameters were used to ascertain information regarding the dynamics of semicircular–canal function. In particular, the coefficients θ and Π in the torsion pendulum model (Steinhausen, '31; Egmond et al., '49), and the time constants ζL ⋍ Π/Δ and ζS ⋍ θ/Π of the torsion pendulum model were estimated for the little brown bat from these parameters. Where appropriate, comparisons were made to time constants obtained for other species.
Freeze‐fracture study of the postsynaptic membrane of the cerebellar mossy fiber synapse in the frog
Authors: Korte Gary E. , Rosenbluth Jack
Published: January 2005

We have examined the postsynaptic membrane of the synaptic junctions of frog cerebellar mossy fibers by electron microscopy of freeze‐fracture replicas and thin sections. The intramembranous particles (imps) in the E fracture face of the postsynaptic membrane are approximately 10 nm in size and form conspicuous aggregates which we classified as macular, annular, or anastomotic in form, according to the occurrence and placement of imp‐free ‘windows’ within the aggregate. The size and shape of the aggregates appear related in that the area of macular aggregates is consistently smaller than the area of annular or anastomotic aggregates. Measurements of aggregate area range from 0.06 to 0.75 μm2. The variable size and shape of the imp aggregate in the postsynaptic membrane sets it apart from other excitatory synapses in the central nervous system, where macular aggregates are usually described. Examination of serial thin sections suggests that the shape of the postsynaptic density is equivalent to that of the imp aggregate observed in the postsynaptic membrane by freeze‐fracture. This supports the notion that the region of postsynaptic membrane associate with the postsynaptic density in thin sections correponds to the particle‐rich regions of E face membrane observed in freeze‐fracture replicas.
Descending projections from the spinal and mesencephalic nuclei of the trigeminal nerve to the spinal cord in the cat. A study with the horseradish peroxidase technique
Authors: Matsushita Matsuo , Okado Nobuo , Hosoya Yasuhiko , Ikeda Michiko
Published: January 2005

Descending projections from the spinal (Vsp) and the mesencephalic nuclei (Vme) of the trigeminal nerve to the spinal cord were studied by means of the retrograde horseradish peroxidase technique in the cat.

The number of labeled neurons was largest in the case of high cervical injections and decreased as the injections were placed caudally. Small laminae III and IV neurons of the nucleus caudalis (Vc) were labeled ipsilaterally following injections placed as caudally as the middle cervical segments (C4‐C5). Lamina I (marginal) neurons of the Vc were labeled ipsilaterally after injections at the middle thoracic level (T6) but those of C1 were labeled after lumbar injections (L3). Lamina V neurons of C1 and the medullary counterparts were labeled bilaterally after injections placed caudally to thoracic segments. A few small neurons were labeled in the ipsilateral nucleus interpolaris (Vi) after injections placed as caudally as the middle cervical segments (C6). Among the subdivisions of the Vsp, the labeled neurons were most numerous in the nucleus oralis (Vo). They were medium‐sized and large, and appeared bilaterally, with an ipsilateral predominance at the level of the superior olive. The great majority projected to the cervical segments but a few also projected to the lower cervical to the thoracic segments (C8‐T9). Neurons of the Vme projected ipsilaterally to the upper cervical segments (C1‐C3). No projections were found from the principal sensory nucleus.

The present study suggests that the trigeminospinal projections of the Vsp and the Vme are composed of various cells of origin and thereby subserve not only the trigeminospinal reflex but other unknown functions.
HRP study of the organization of auditory afferents ascending to central nucleus of inferior colliculus in cat
Authors: Brunso‐Bechtold J. K. , Thompson G. C. , Masterton R. B.
Published: January 2005

The ascending auditory projections to central nucleus of inferior colliculus its ventrolateral and dorsomedial subdivisions (ICVI, and ICDM) have been studied in cat using both pressure and electrophoretic injections of horseradish peroxidase (HRP). The results indicate that the predominant ascending projections to inferior colliculus orginate in (1) contralateral cochlear nucleus, (2) contralateral and ipsilateral lateral superior olive, (3) ipsilateral medial superior olive, (4) ipsilateral ventral nucleus of the lateral lemniscus, (5) ipsilateral and contralateral dorsal nucleus of the lateral lemniscus, and (6) contralateral inferior colliculus. In addition, ipsilateral cochlear nucleus, ipsilateral and contralateral intermediate nucleus of the lateral lemniscus, ipsilateral, and to a lesser extent contralateral, periolivary nuclei project to inferior colliculus. Of these nuclei, the lateral superior olive projects exclusively to ICVL and ipsilateral cochlear nucleus and contralateral inferior colliculus project mostly, if not exclusively, to ICDM. Many of these projections demonstrate a cochleotopic organization and frequently a nucleotopic organization as well. A cochleotopic organization of the projections is apparent for cochlear nucleus and superior olivary complex. A nucleotopic organization suggests that the heaviest terminations of contralateral inferior colliculus are medial and dorsal in inferior colliculus, of medial superior olive are dorsal and lateral, of superior olivary complex are rostral, of cochlear nucleus are caudal, and of ventral nucleus of the lateral leminiscus are caudal.
Freeze‐fracture study of photoreceptor outer segments and pigment epithelium in dystrophic and normal retinas
Authors: McLaughlin Barbara J. , Boykins Lou G.
Published: January 2005

The intramembrane organization of outer segment (OS) membranes and pigment epithlial (PE) microvilli has been studied in rats (10–17 postnatal days) with inherited retinal degeneration (RCS) and in normal retinas from genetically controlled rats (RCS‐rdy +). The OS plasma membranes of both dystrophic and normal retinas are characterized by large particles surrounding circular, particle‐free zones on the P‐faces (cytoplasmic leaflets) and a sparse distribution of particles on the E‐faces (external leaflets). No regional differences in particle distribution are observed in either basal or distal plasma membrane regions. Outer segment disc membranes are characterized by large, densely packed P‐face particles and ridged E‐faces with very few particles. Small, particle‐free patches of membrane are present in the basal disc P‐faces of both normal and dystrophic retinas, which Andrews and Cohen (1979) have described as characteristic of newly added disc membrane. In dystrophic retinas, larger, particle‐free domains are observed in the distal disc membranes (P‐faces) and accumulating membranous debris. In older retinas, which have accumulated more debris, the particle‐free domains occupy vast areas of the membrane faces and it is not possible to identify these membranes as belonging to either discs or plasma membranes. No comparable areas of particle‐free membrane are observed in the distal discs and OS plasma membranes of normal retinas. Pigment epithelial microvillus membranes are characterized by an intermixture of large and medium‐sized particles surrounding irregular particleq‐free areas, but no differences between normal and dystrophic PE membranes are observed. The changes in particle distribution observed in the dystrophic retinas suggests that the intramembrane molecular composition of older disc membranes has become altered or rearranged as the OS membranes accumulate as debris.
Postnatal modifications of the dendritic tree of cells in the inferior coliicuius of the cat. A quantitative Golgi analysis
Authors: Meininger Vincent , Baudrimont Marie
Published: January 2005

Postnatal modifications of dendrites have been quantitatively studied by network analysis of the dendritic tree in the two central nuclei of the inferior colliculus in the cat. This analysis revealed cells with two types of branching patterns suggesting two different modes of growth. The predominant pattern is characterized by dichotomous branching on random segments (DR cells). However, a purely collateral branching pattern is particular to certain cells (CB cells). These two branching patterns were found in both nuclei of the IC in adult and young cats, but the exact significance of these two cell types remains unclear.

The dendritic trees ofcells in kittens differed from those ofthe adult cat. Also, the types of modification were different in the two functionally distinct nuclei of the inferior colliculus that we studied. The most dramatic modifications were observed in the dendritic tree of DR cells in the central nucleus, which receives fibers from the auditory nuclei in the brainstem. Two parameters were modified: the mean number of terminal segments and the mean total length of segments. Both parameters increased in the sagittal plane and decreased in the frontal plane. These modifications indicate a reorientation of the dendritic tree in the sagittal plane, along the incoming axons from the auditory nuclei. As these afferents become functionally mature only after birth, this spatial remodeling of the dendrites seems closely related to functional maturation of secondary auditory axons. In the dorsomedial nucleus that receives fibers from the auditory cortices, the dendritic tree of DR cells also undergoes spatial reorientation. This is more evident in the horizontal plane and with respect to the incoming axons.

Our results suggest that the characteristic orientation of the dendritic tree of cells observed in the inferior colliculus of the adult cat is established only after the first postnatal weeks. This orientation seems to result from an active process of remodeling concomitant with the functional maturation of afferents, a fact already established for various cell types in the nervous system.
The distribution of nine peptides in rat spinal cord with special emphasis on the substantia gelatinosa and on the area around the central canal (laminaX)
Authors: Gibson Sally J. , Polak Julia M. , Bloom Stephen R. , Wall Patrick D.
Published: January 2005

The comparative distribution of nine peptides was examined in the L4 segment of the rat cord using the peroxidase antiperoxidase technique. The peptides examined were substance P, neurotensin, cholecystokinin, methionine‐enkephalin, oxytocin, neurophysin, adrenocorticotrophin, thyrotropin releasing hormone, and vasoactive intestinal polypeptide. No transport blocking agents were used and in spite of this cell bodies containing substance P, neurotensin, cholecystokinin, and methionine‐enkephalin were observed. All peptides except for thyrotropin releasing hormone were observed in fibers in laminae I and II. All peptides were present in the area around the central canal, laminaX. Each peptide had its own characteristic distribution within fibers in the gray and white matter.