bluuebunny/crossref_metadata_2025 huggingface dataset:
Time course of reactive synaptogenesis in the subcortical somatosensory system
Authors: Wells Joseph , Tripp Leslie N.
Published: January 2005

These experiments were designed to determine when synaptogenesis begins in the adult rat ventral posterolateral nucleus of the thalamus following lesions of the dorsal column nuclei. Given the relatively uncomplicated structure of the neuropil in the ventral posterolateral nucleus of the rat, the specificity of reactive synaptogenesis of the lemniscal input and the effect of the loss of lemniscal terminals on terminals from other sources could be determined. By use of morphometric analysis of electron micrographs, the numerical density of the 3 terminal types in the neuropil was determined at a series of postlesion survival times ranging from 12 hours to 50 days. Synaptogenesis began about 30 days after the lesions of the dorsal column nuclei and was complete by 50 days. The slow onset of synaptogenesis was in response to a loss of the lemniscal terminals, which account for only 3% of the total number of synapses in the ventral posterolateral nucleus. The low level of synaptogenesis early in the recovery process differs from the recovery seen in other central nervous system sites, which show an early rapid increase in synapses in response to much greater denervation. The loss of lemniscal terminals has relatively little effect on the numerical density or distribution of the terminals of other types. The new terminals that are formed come both from axons that originate from the undamaged portion of the dorsal column nuclei and from axons originating in the spinal cord.
The ventral striatopallidothalamic projection: II. The ventral pallidothalamic link
Authors: Zahm D. S. , Zaborszky L. , Alheid G. F. , Heimer L.
Published: January 2005

The projection of ventral pallidal neurons to the mediodorsal nucleus of the thalamus (MD) was examined in rats by combined retrograde transport of horseradish peroxidase (HRP) after injections in the MD and glutamate decarboxylase (GAD) immunocytochemistry at light and electron microscopic levels, with and without prior exposure of the brains to colchicine. HRP was transported Lo the soma of medium‐sized and large ventral pallidum neurons, which along with their long, large dendrites were contacted by many glutamate decarboxylase immunoreactive synaptic boutons. The retrograde tracer positive neurons bore a remarkable resemblance to the projecting cells of the globus pallidus and entopeduncular nucleus. When colchine exposure was included in the tissue preparation, some but not all tracer positive cells also exhibited cytoplasmic GAD immunoreactivity.
Selective retrograde labeling of lateral olivocochlear neurons in the brainstem based on preferential uptake of 3H‐D‐aspartic acid in the cochlea
Authors: Ryan Allen F. , Schwartz Ilsa R. , Helfert Robert H. , Keithley Elizabeth , Wang Zhi‐Xian
Published: January 2005

We have previously shown that perfusion of the gerbil cochlea with probe concentrations of 3H‐D‐aspartic acid (D‐ASP) results in immediate, selective labeling of 50–60% of the efferent terminals under the inner hair cells, presumably by high‐affinity uptake. The present study was undertaken to determine the origin of these endings. Twenty‐four hours after cochlear perfusion with D‐ASP, labeled neurons were observed in the ipsilateral, and to a much lesser extent in the centralateral, lateral superior olivary nucleus (LSO). The cells were small, primarily fusiform, and showed fewer synaptic contacts than other LSO cells. Combined transport of D‐ASP and horseradish peroxidase indicated that all olivocochlear neurons within the LSO that projected to the injected cochlea were labeled by D‐ASP.

Labeled fibers coursed dorsally from the LSO, joined contralateral fibers that had passed under the floor of the fourth ventricle, and entered the VIIIth nerve root at its ventromedial edge. Adjacent to the ventral cochlear nucleus (VCN), densely labeled collateral fibers crossed the nerve root to enter the VCN. Labeled fibers and terminals were prominent in the central VCN.

Neither retrograde transport of D‐ASP by medial olivocochlear and vestibular efferents nor anterograde transport by VIIIth nerve afferents was observed.

The D‐ASP‐labeled cells and fibers are clearly lateral olivocochlear efferents. Retrograde transport of D‐ASP thus allows the cells, axons, and collaterals of the lateral olivocochlear system to be studied, morphologically, in isolation from other cells that project to the cochlea. Since the olivocochlear neurons are almost certainly cholinergic, retrograde amino acid transport does not necessarily identify the primary neurotransmitter of a neuron. Rather, it indicates the presence of selective uptake by the processes of that neuron at the site of amino acid injection. Retrograde labeling appears to be markedly enhanced by the use of metabolically inert compounds such as d‐isomer amino acids.
The chandelier cell of the human visual cortex: A Golgi study
Authors: Marin‐Padilla Miguel
Published: January 2005

The size, location, distribution, and spatial orientation of the chandelier cell of the human visual cortex are described for the first time. The rapid Golgi method has been utilized to study the structural features of these inhibitory interneurons. The human chandelier cell is a small stellate interneuron with prominent idiodendritic and idioaxonic arborizations. These arborizations are distributed within a narrow rectangular tissue slab that measures approximately 300 × 200 × 100 m̈m. This relatively small and narrow functional territory is oriented perpendicular to the pial surface and to the long axis of the gyrus. The territory of distribution of its axon is larger than and encloses that of its dendrites. The number of specific axonic terminals (candles) per chandelier cell is also relatively small, ranging from 60 to 80 units. These axonic terminals represent the functional units of the neuron and reflect the number of pyramidal cell axons contacted by it. The chandelier cell of the human visual cortex possibly represents the smallest neuron of this kind described to date. The size of its functional territory and the number of its specific axonic terminals are among the smallest of any neuron of this kind thus far described. It is postulated herein that in the course of mammalian phylogeny the chandelier cell shows a tendency toward a progressive reduction in the size of its functional territory and in the number of its functional units (candles), as well as a tendency toward a more “idio” pattern of distribution for its axonic and dendritic arborizations. Perhaps, these progressive evolutionary modifications could reflect a tendency of this type of interneuron toward an increasing specialization. The possible existence of a relationship between the progressive transformation of the chandelier cell and the increasing visual acuity, dexterity, and skillfulness in the course of mammalian phylogeny should be explored.
Morphology of pontomedullary raphe and reticular formation neurons in the brainstem of the cat: An intracellular HRP study
Authors: Edwards D. Louise , Johnston Karen M. , Poletti Charles E. , Foote Warren E.
Published: January 2005

In order to understand better the anatomical substrates underlying processing of sensory information, the cytoarchitecture of neurons in the pontomedullary raphe and reticular formation was investigated following intracellular injections of horseradish peroxidase in the cat. Raphe cells studied were located in the nucleus raphe magnus, nucleus raphe obscurus, and nucleus raphe pallidus. The most prominent type had a smooth, oval cell body and oval dendritic tree with dendrites extending laterally into the adjacent reticular formation. Two other raphe cell types, large cells with a dorsoventral orientation of both cell body and dendritic tree, and very small cells, were rarer. The primary dendritic orientation lay in the coronal plane for all three raphe cell types. Wispy, straight, or clublike spines were located on more distal regions of dendrites, although we also found spineless dendrites. Raphe cells lying near longitudinal fiber pathways exhibited bundling of dendrites around the passing axon fascicles. Reticular formation cells studied were located in the nucleus gigantocellularis, nucleus magnocellularis, nucleus paragigantocellularis dorsalis, and nucleus reticularis paramedianus. Two morphological types were found on the basis of dendritic branching patterns: sparsely branched and densely branched. Most reticular formation cells had round dendritic trees as viewed in the coronal plane and polygonal cell bodies that were medium to large in size. There was no correlation between reticular formation cell morphology and nuclear location. Spines were more common on the densely branched cells, but for both reticular cell types they were usually absent from cell bodies and proximal dendrites. Thus, by using the criteria of dendritic branching and arbor shape along with distance from the midline it was possible to identify raphe cells as distinct from reticular formation cells. In contrast, no morphological characteristics were found that would differentiate cells in the two major median reticular formation nuclei, gigantocellularis and magnocellularis.
Afferent connections of anterior thalamus in rats: Sources and association with muscarinic acetylcholine receptors
Authors: Sikes Robert W. , Vogt Brent A.
Published: January 2005

Afferent connections of the anterior thalamic nuclei (ATN) are classically thought to originate in the mammillary body and limbic cortex. This study explores nonlimbic sources of ATN afferents by using retrograde transport of horseradish peroxidase (HUP) to ascertain the relative contribution of these connections. Spread of HRP into adjacent regions was prevented either by removing the overlying cortex or by injecting through permanently implanted cannulas.

The main sources of nonlimbic ATN afferents are the pretectum and central gray. Pretectal neurons were HRP‐labeled primarily in the contralateral medial pretectal nucleus with a smaller number in the ipsilateral posterior pretectal nucleus. In the central gray, labeled cells were concentrated ipsilaterally in the laterodorsal tegmental nucleus. Additional projections to ATN originate in the reticular and ventral lateral geniculate nuclei of the thalamus, raphe nuclei, peripontine tegmental nucleus, and locus coeruleus.

The association of ATN afferents with muscarinic receptors was also explored by means of in vitro receptor autoradiography with the muscarinic ligands propylbenzilylcholine mustard (PrBCM) and pirenzepine (PZ) in normal rats and rats with ablations. Ibotenic acid injections into ATN were used to destroy intrinsic neurons while leaving afferent fibers intact. Whereas such ablations produced statistically significant decreases in PrBCM binding in the anterior dorsal (AD, −45%) and anterior ventral, magnocellular part (AVm, −51%) nuclei, binding in the anterior ventral, parvicellular part (AVp) and anterior medial (AM) nuclei was not significantly decreased. Furthermore, PZ binding in normal rat ATN was significantly less (−72%) than PrBCM binding. These results suggest that a major proportion of muscarinic binding is associated with presynaptic elements.

Ibotenic acid ablations of the mammillary body reduced PrBCM binding in ATN whereas lesions in cingulate cortex and laterodorsal tegmental nucleus had no effect. Compared to sham lesion controls, mammillary body lesions resulted in statistically significant decreases in binding bilaterally in AD (−15%), AVm (−19%), and AM (−20%).

In conclusion, ATN receive afferents from several nonlimbic regions. Of these inputs, the pretectum may be the primary route through which sensory information reaches ATN. In addition, cholinergic input may modulate activity in projections from the mammillary body to ATN through presynaptic muscarinic receptors.
Immunohistochemical study on the distribution of neuron‐specific enolase‐ and peptide‐containing nerves in the omasum of cattle
Authors: Kitamura N. , Yamada J. , Yamashita T.
Published: January 2005

The distribution of nerves containing immunoreactivity for substance P (SP), vasoactive intestinal polypeptide (VIP), leucine‐enkephalin (LENK), and gastrin‐releasing polypeptide (GRP) in the margin of the reticulo‐omasal orifice, omasum, and omasal pillar of calves and cows was studied by immunohistochemistry. The general distribution of nerves was determined by means of neuron‐specific enolase (NSE) antiserum and then compared to the distribution of immunoreactive (IR) nerves stained for the four peptides.

Marked differences in the distribution of immunoreactive nerves were associated with age and the segment examined. SP‐IR fibers were abundant in the musculature of the ungulate papillae at the reticulo‐omasal orifice and in the smooth muscle of the omasal leaves, moderately dense in the omasal pillar, and low in density in the inner muscle layer of the reticuio‐omasal orifice and in the muscle of the omasal wall. In order of decreasing abundance, the cell bodies of SP‐IR nerves were found at the reticulo‐omasal orifice, in the omasal wall, and in the omasal pillar. LENK‐IR fibers, though less abundant, showed a pattern of distribution that was similar to that of SP‐IR fibers. Nerve cell bodies showing weak immunoreactivity for LENK were detected rarely. Abundant VIP‐IR fibers were present in the inner muscle layer of the reticulo‐omasal orifice and in the omasal wall, while moderate numbers were seen in the omasal pillar: they were low in density in the ungulate papillae and omasal leaves. Cell bodies of VIP‐IR nerves decreased in number through the omasum, reticulo‐omasal orifice, and omasal pillar. The distribution of GRP‐IR nerve fibers was similar to that of VTP‐IR fibers, although GRP‐IR fibers were less abundant. Nerve cell bodies showing weak immunoreactivity for GRP were detected rarely. The individual distribution of peptide‐IR nerves was similar in the calf and cow, but immunoreactive nerves were far more abundant in the calf. The present study provides valuable information for discussion of the possible role of nerves in the regulation of omasal function.
Ultrastructure and distribution of substance P‐immunoreactive sensory collaterals in the guinea pig prevertebral sympathetic ganglia
Authors: Matthews M. R. , Connaughton M. , Cuello A. C.
Published: January 2005

A light and electron microscopic study has been made of the substance P‐immunoreactive networks formed by sensory nerve fibres in the prevertebral sympathetic ganglia of the guinea pig to seek confirmation that these networks arise from collateral branches of sensory fibres passing through the ganglia and to explore the synaptic and other specialized relationships established by these networks. Slices from coeliac‐superior mesenteric and inferior mesenteric ganglia of young adult males, perfusion‐fixed by para‐formaldehyde, were immunostained with a monoclonal antibody to substance P, and the immunolabelling was visualized by a peroxidase reaction.

Immunolabelled fibres passing through the ganglia were seen by light microscopy to give off varicose collaterals that ramified in the ganglionic neuropil. Electron microscopy showed that the parent fibres were almost exclusively unmyelinated. Many collaterals ran directly beneath the basal lamina bordering the intraganglionic tissue spaces, and the varicosities either remained superficially exposed under the basal lamina or sank deeper into the supporting Schwann cells, becoming apposed to dendrites of the ganglionic neurones, upon which they formed synapses, or to other nerve terminals. The incidence of these specific associations was quantified, singly and in combination. Synapses could be situated at the same level as unlabelled synapses on the same dendrite, and exposed varicosities could lie within 0.5 μm of exposed, postsynaptic dendrites. These observations confirm a collateral, synaptic nature for the networks and suggest additional nonsynaptic modes of release and sites of transmitter action. They are consistent with the hypothesis that the system serves a nocifensor function of axon reflex type.
Ultrastructural identification and localization of climbing fiber terminals in the fastigial nucleus of the cat
Authors: van der Want J. J. L. , Voogd J.
Published: January 2005

Following injections of 3H‐leucine and 35S‐methionine in the caudal half of the medial accessory olive, labeled climbing fibers were found contralateral to the injection site in the sagittal A‐zone of the cerebellar vermis and in the fastigial nucleus. Labeling in the fastigial nucleus was analyzed with ultrastructural autoradiography. Labeled boutons of climbing fibers were found in the neuropil but never on somata. They contain spherical vesicles and occasionally some dense core vesicles in an electron‐lucent matrix. The terminals of climbing fiber collaterals in the fastigial nucleus resemble climbing fiber terminals in the molecular layer with respect to their internal ultrastructural characteristics.
Localization of aromatase in the brain of the male African catfish, Clarias gariepinus (Burchell), by microdissection and biochemical identification
Authors: Timmers R. J. M. , Lambert J. G. D. , Peute J. , Van Oordt P. G. W. J. , Vullings H. G. B.
Published: January 2005

Aromatase activity was determined in small discrete areas of the brain of the African catfish, Clarias gariepinus, by a radiometric assay. The fore‐and midbrain were divided into eighteen 500‐μm transverse sections. From these sections several punches (0.3 mg of tissue) were taken and incubated with [19‐3H]‐androstenedione. The aromatase activity, calculated from the release of tritium label during aromatization, is expressed in pmol mg−1 tissue hour−1.

The highest activity (3.7 pmol) was detected in the preoptic region. The more caudally located area tuberalis, including the nucleus lateralis tuberis and the nucleus recessus lateralis, also showed a relatively high activity (2.5 pmol).

A similar activity was found in the most rostral part of the telencephalon and the dorsal parts of the mesencephalon, i.e., the tectum opticum and torus semicircularis (2.3 pmol). A moderate aromatase activity was observed in remaining parts of the brain, except the cerebellum and hindbrain, in which aromatase activity was hardly detectable (0.1–0.3 pmol).

It is concluded that a high aromatase activity is present in regions known to be involved in the regulation of reproduction. Since both the torus semicircularis and the tectum opticum display a high aromatase activity, it is suggested that also these structures are involved in reproductive processes.
Double‐labeling study of axonal branching within the lateral reticulocerebellar projection in the rat
Authors: Ghazi H. , Hrycyshyn A. W. , Flumerfelt B. A.
Published: January 2005

Collateral axonal branching to the cerebellum from the lateral reticular nucleus (LRN) was studied in the rat by using the fluorescent double‐labeling technique. Following injection of Fast Blue (FB) into the cerebellar cortex, followed 3 days later by injection of Nuclear Yellow (NY) into a different region of the cortex, single‐ and double‐labeled cells were found within the LRN. Most LRN‐cerebellar projections were bilateral with ipsi‐lateral preponderance, except for the projection to the paramedian lobule, which was completely ipsilateral.

The dorsolateral area of the magnocellular division of the LRN contained cells whose axons branch to terminate in the rostral anterior lobe and the caudal part of the ipsilateral paramedian lobule (hindlimb areas of the cerebellar cortex), while the medial area of the LRN contained cells that supply, via collateral axonal branching, the caudal area of the contralateral anterior lobe and the rostral part of the ipsilateral paramedian lobule (forelimb areas of the cerebellum). Branched LRN‐cerebellar axons projected to both hemispheres and to both sides of the caudal anterior lobe. No axonal branching was evident in the LRN‐cerebellar projection to the rostral anterior lobe. The projection to the anterior and posterior lobe vermis also contained collateral axonal branching.
Electron microscopic study of the rubrocerebellar projection in the cat
Authors: Nakamura Yasuhisa , Kitao Yasuko , Moriizumi Tetsuji , Kudo Motoi
Published: January 2005

Rubral neurons sending axons to the cerebellar anterior interpositus nucleus (AIN) in the cat were identified light microscopically by labeling them with horseradish peroxidase (HRP). The synaptic organization of these rubral neurons and of their afferents from the cerebral motor cortex and the AIN was also analyzed electron microscopically by combined anterograde degeneration and retrograde HRP‐labeling techniques.

In the light microscopic study, either HRP or a mixture of HRP and kainic acid was injected into the AIN. Both of the injections resulted in retrograde labeling of rubrocerebellar projection neurons in the red nucleus on the contralateral side. The labeled neurons were distributed throughout the rostrocaudal extent of the red nucleus: some lay in clusters. Most labeled neurons were small to medium‐sized, although some were large. The injection of HRP into the AIN also resulted in anterograde labeling of cerebellorubral projection fibers terminating in a wider area of the red nucleus on the contralateral side of the injection, whereas the injection of a mixture of HRP and kainic acid showed no anterograde labeling of fibers or terminals.

In one set of electron microscopic observations, HRP injections into the AIN were combined with ablation of the motor cortex. Degenerating axon terminals were occasionally found to synapse with both dendrites and neuronal somata labeled with HRP retrogradely.

In another set of electron microscopic observations, a mixture of HRP and kainic acid was injected into the AIN in order to label rubrocerebellar projection neurons retrogradely and to bring about degeneration in the cerebellorubral projection fibers anterogradely. Abundant degenerating axon terminals were observed to make axosomatic synaptic contacts with rubral neurons labeled with HRP retrogradely and also with unlabeled rubral neurons.

These results indicate that cerebrorubrocerebellar and rubrocerebellorubral monosynaptic circuitries exist which constitute one of the cerebrocerebellar linkages, as well as those linkages via the inferior olivary complex and the pontine nuclei.
Gamma‐aminobutyric acid‐ and glutamic acid decarboxylase‐immunoreactive neurons in the retina of different vertebrates
Authors: Agardh E. , Bruun A. , Ehinger B. , Ekström P. , van Veen T. , Wu J.‐Y.
Published: January 2005

The localization of gamma‐aminobutyric acid (GABA)‐ and L‐glutamate 1 carboxy‐lyase (GAD)‐immunoreactive neurons was compared in the skate, frog, pigeon, chicken, rabbit, and man. Horizontal cells show both GABA and GAD immunoreactivity in the skate, frog, and bird. Certain amacrine cells show GABA and GAD immunoreactivity in all species. The distribution of GABA‐ and GAD‐immunoreactive cell bodies and cell processes was very similar, if not identical, in the skate and man. In the other species, cell populations with GAD immunoreactivity also showed GABA immunoreactivity. However, in the bird, frog, and rabbit, the GABA‐immunoreactive amacrine cells were at least twice as numerous as the GAD‐immunoreactive cells. In birds, the distributions of the GAD and GABA immunoreactivities were different in the sublayers of the inner plexiform layer. The reason for the difference is currently unknown. GABA‐immunoreactive bipolar‐like cells were seen in the frog.
The brainstem projection to the lateral geniculate nucleus in the cat: Identification of cholinergic and monoaminergic elements
Authors: De Lima Ana Dolabeia , Singer Wolf
Published: January 2005

The pontomesencephalic projection to the dorsal lateral geniculate nucleus (dLGN) of the cat was analyzed by combining retrograde transport of rhodamine‐labeled latex spheres and immunohistochemistry. After injections of latex beads into the dLGN, sections of the brainstem were treated immunohistochemically for choline acetyltransferase (ChAT), serotonin (Ser), tyrosine hydroxylase (TH), and dopamine‐beta‐hydroxylase (DBH).

Essentially, six regions in the brainstem contained retrogradely labeled cells: the superior colliculus, the parabigeminal nucleus, the dorsal raphe nuclei, the parabrachial area of the central tegmental field, the marginal nucleus of the brachium conjunctivum, and the nucleus coeruleus. Furthermore, isolated retrogradely labeled cells were present in the central nucleus of the raphe, in the cuneiform nucleus, and in the periaqueductal gray. Most serotoninergic double‐labeled cells were found in the medial and lateral divisions of the dorsal raphe nuclei, but a few were also present in the central nucleus of the raphe. In the sections immunostained for ChAT, double‐labeled cells were located in the central tegmental field, in the marginal nucleus of the brachium conjunctivum, and in the nucleus coeruleus. In the sections treated for TH and DBH, double‐labeled cells showed a similar distribution, and like the ChAT(+) cells, they were located mainly in the central tegmental field, in the marginal nucleus of the brachium conjunctivum, and in the nucleus coeruleus. In these regions the cholinergic and noradrenergic cells that projected to the lateral geniculate nucleus were intermingled, the former predominating rostrally and the latter caudally.

The majority of retrogradely labeled cells were located in the region of the central tegmental field in the vicinity of the brachium conjunctivum, and most of these cells were also ChAT‐immunoreactive. We, therefore, conclude that the cholinergic projection is the most important of the central core projections ascending to the dLGN.
Fine structure of the ganglion of Cephalodiscus gracilis (pterobranchia, hemichordata)
Authors: Rehkämper G. , Welsch U. , Dilly P. N.
Published: January 2005

The ganglion of Cephalodiscus gracilis M'Intosh 1882 is entirely intra‐epithelial and located in the dorsal epidermis immediately behind the tentacular apparatus that is formed by the mesosome (collar). A characteristic feature of the ganglion is a well‐developed neuropile in which different types of nerve fibres can be discerned, many of which contain small granules with electron‐dense contents. There are no glia‐like cells in association with these fibres. Only slender basal processes of epidermal epithelial cells traverse the neuropile. In the depth of the epithelium the neuropile borders the epidermal basal lamina; apically it is covered by a layer of cell bodies, the majority of which belong to what appear to be ordinary ciliated epidermal cells. Besides these epidermal cells the perikarya of two additional types of cells, which are considered to be neurons, can be discerned. One type is characterised by many rough endoplasmic reticulum cisterns and mitochondria, the other by abundant small, electron‐dense granules. The nuclei of these cells are comparatively pale and contain a prominent nucleolus. The neuron cell bodies do not form a distinct layer; but they are loosely distributed somewhat deeper than those of the ordinary epidermal cells. They probably send off an apical process to the epidermal surface and a basally directed one into the neuropile. The ganglion has been compared to the nervous systems in cnidarians, some spiralians, and especially other hemichordates, echinoderms, and chordates; it is found to be of primitive rather than degenerate nature. Furthermore, the possible functional significance of its close connection to the food‐capturing tentacular apparatus is discussed.
Sexual differentiation of androgen accumulation within the zebra finch brain through selective cell loss and addition
Authors: Nordeen Ernest J. , Nordeen Kathy W. , Arnold Arthur P.
Published: January 2005

In zebra finches males, but not females, respond to gonadal androgens with the production of a stereotyped courtship song. Corresponding to this dimorphism in hormone sensitivity, two song‐related neural regions, magnocellular nucleus of the anterior neostriatum (MAN) and hyperstriatum ventralis pars caudalis (HVc), have more cells that accumulate androgens in males than in females. The early hormonal environment establishes these sex differences in the brain and behavior such that females treated with estradiol (E2) shortly after hatching have male‐typical levels of androgen accumulation in MAN and HVc, and respond to adult androgen stimulation with male‐typical song. Using autoradiographic procedures employing the androgen 3[H]‐dihydrotestosterone (DHT), the present study focused on whether E2 masculinizes androgen target cell numbers in MAN and HVc by inducing, or rather preserving, a male‐typical number of androgen target cells. First, it was demonstrated that E2 treatment of females as late as 20 days after hatching increases the number of MAN and HVc cells accumulating 3[H]‐DHT or its metabolites in adulthood to levels typical of males. Then the number of androgen target cells present within these nuclei in 20‐day‐old females was compared with the number present in adult females previously masculinized with E2 treatment on day 20. In MAN, E2 masculinizes androgen accumulation by preserving androgen target cell numbers in the face of massive overall cell loss, a result that suggests that E2 promotes the survival of androgen target cells during sexual differentiation. In HVc, however, E2 treatment on day 20 promotes an addition of androgen target cells, suggesting that during adolescence, E2 regulates the proliferation, migration, and/or survival of these cells.
In vivo ANTI‐NGF induces sprouting of sensory axons in dorsal roots
Authors: Hulsebosch C. E. , Perez‐Polo J. R. , Coggeshall R. E.
Published: January 2005

Newborn rats were given subcutaneous injections of antibodies to mouse β ‐NGF (ANTI‐NGF) daily for 1 month. The number of neurons in T4‐T6 dorsal root ganglia (DRG) and the numbers of myelinated and unmyelinated axons in the dorsal roots of the same segments were counted in the ANTI‐NGF animals and in normal littermates. The ANTI‐NGF rats had 38% fewer neurons in thoracic ganglia but 17% more myelinated and 40% more unmyelinated fibers than their untreated littermates. Dorsal root ganglion cells also have a larger average size in the ANTI‐NGF animals, which we interpret as a disproportionate loss of small cells. These data are interpreted as showing that some dorsal root ganglion cells, principally small ones, die when endogenous NGF is inactivated, and that the remaining cells emit more processes than normal. Thus, removal of NGF has what appears to be a paradoxical effect, a reduction in dorsal root ganglion cell numbers but an increase in dorsal root axon numbers. The relation of myelin thickness to fiber diameter is also altered, with small fibers being more thinly myelinated in the ANTI‐NGF group. Thus, Schwann cell‐neuronal interactions are also affected by inactivation of NGF.
Cerebellocerebral projection from the fastigial nucleus onto the frontal eye field and anterior ectosylvian visual area in the cat
Authors: Kyuhou Shin‐Ichi , Kawaguchi Saburo
Published: January 2005

The fastigiocerebral projection in the cat was investigated electrophysiologically by recording field potentials and unit activities and also morphologically by anterograde and retrograde HRP methods. Three cortical areas mostly hidden in sulci, two in the frontal cortex and one in the insular cortex, were responsive to fastigial stimulation under pentobarbital anesthesia. The responsive areas in the frontal cortex were the ventral bank of the cruciate sulcus and the area surrounding the fundus of the presylvian sulcus; the latter area corresponds to a subregion of the frontal eye field. The responsive area in the insular cortex Was the ventral bank of the anterior ectosylvian sulcus, which overlaps largely with the “anterior ectosylvian visual area.” The response in the frontal cortex was a surface‐positive, depth‐negative wave, whereas the response in the insular cortex was a surface negative, depth‐positive wave. Anterogradely labeled terminals of the fastigiothalamic projection were most dense in the ventromedial (VM) nucleus in which retrogradely labeled neurons were numerous when WGA‐HRP was injected into any one of the three cortical areas. In agreement with the results of the HRP studies, units that responded orthodromically to fastigial stimulation and antidromically to cortical stimulation were located in the thalamic VM nucleus. There was a marked difference between the frontal and insular cortices in laminar distribution of terminals of the thalamocortical projection fibers. Anterogradely labeled terminals after injection of WGA‐HRP into the VM nucleus were distributed mainly in layers I and III in the frontal cortex, whereas they were distributed mainly in layer I in the insular cortex.
Topography and morphometry of capillaries in the rat subfornical organ
Authors: Sposito Nadine M. , Gross Paul M.
Published: January 2005

A comprehensive stereological analysis was performed to define capillary dimensions in individual subregions of the subfornical organ in Long‐Evans, homozygous Brattleboro, and Sprague‐Dawley rats. Capillary density, volume fraction, length, surface area, and diameter were assessed in four regions in the sagittal plane (rostral, “transitional,” central, and caudal) and two zones in the coronal plane (dorsal and ventromedial). The ventromedial zones in the central and caudal regions correspond to areas of dense perikarya and neuropil containing neural afferent inputs to the subfornical organ (e.g., putative fiber terminals for angiotensin II), whereas the dorsal zones of these regions are apparently the predominant sites of perikarya having efferent projections directed outside of the organ

The morphometric analysis revealed heterogeneous capillary density across subregions of the subfornical organ (range of 132 to 931 capillaries/mm2 in the three rat groups). Capillaries in the ventromedial zones of the central and caudal regions had significantly greater density, volume fraction, and surface area, but smaller diameters, than those in the adjacent dorsal zones and more rostral regions. Across all subregions within the dorsal zone, there was generally a consistent morphometric pattern in the three rat groups. No differences in capillary dimensions in any part of the subfornical organ were found between the Long‐Evans and Brattleboro rats.

A qualitative electron microscopic investigation of endothelial cells in each subregion of the subfornical organ in Long‐Evans rats revealed at least three types of capillary oriented according to region: (1) in the rostral region were capillaries having no endothelial fenestrations or pericapillary spaces, and few vesicles, (2) in the “transitional” region between the rostral and central regions, capillaries having no endothelial fenestrations, substantial numbers of vesicles, and narrow but perceptible pericapillary spaces were found, and (3) in the central and caudal regions, capillaries having abundant endothelial fenestrations and vesicles, expansive pericapillary labyrinths, and relatively thin walls were present.

These findings from light microscopic morphometry and electron microscopy in rats indicate a heterogeneity of capillary organization that shows topographical correspondence to the cytology and putative functions of the subfornical organ.
Somatostatin immunoreactive neurons in the human hippocampus and cortex shown by immunogold/silver intensification on vibratome sections: Coexistence with neuropeptide Y neurons, and effects alzheimer‐type dementia
Authors: Chan‐Palay V.
Published: January 2005

The distribution of somatostatinlike immunoreactivity was studied in the hippocampal formation, retrohippocampal region, and temporal cortex in the human brain. Tissues from surgical biopsy and postmortem cases were used, and the immunogold/silver method on vibratome sections was introduced for routine applications in conjunction with primary antisera that recognise somatostatin‐14 or somatostatin‐28. Somatostatin‐28 antisera readily stained numerous neurons, dendrites, and extensive axonal networks throughout the hippocampus and neighbouring cortex. Liquid phase absorption provided controls for specificity. The most prominent accumulations of Somatostatin immunoreactive neurons and axons occurred in the hilus of the area dentata, in CA1, and in the entorhinal and perirhinal cortices. Axonal plexuses occurred throughout the hippocampal subfields but were particularly dense in those regions rich in Somatostatin neurons. The distribution of Somatostatin immunoreactive neurons and fibers parallels the distribution of neuropeptide Y (NPY) neurons and fibers in the hippocampus and cerebral cortex to a remarkable extent. Double labelling experiments with antisera against neuropeptide Y and Somatostatin indicate a considerable frequency of coexistence of the two peptides in single neurons, particularly in large multipolar cortical neurons and also in the small bipolar white matter neurons. Regional variations exist in the amounts of coexistence found in the hippocampal subfields; somatostatin‐NPY coexistence is particularly high in the hilus of the area dentata, the subicular complex, and the deep layers of the entorhinal and perirhinal cortices.

In the hippocampi and temporal cortices in cases of Alzheimer‐type dementia compared to those of age‐matched control brains, there is a significant to severe loss of Somatostatin immunoreactive neurons and axons. This loss is most severe in those regions with the highest indices of neurofibrillary tangles and neuritic plaques–the hilus of the area dentata, CA1, and the entorhinal and perirhinal cortices. Surviving Somatostatin neurons are distorted with short dendrites and truncated axons. Neuritic plaques identified on double label experiments with thioflavin include Somatostatin axons but not neurons.
Spinal cord projections from hindlimb muscle nerves in the rat studied by transganglionic transport of horseradish peroxidase, wheat germ agglutinin conjugated horseradish peroxidase, or horseradish peroxidase with dimethylsulfoxide
Authors: Molander C. , Grant G.
Published: January 2005

The spinal cord projections of four different groups of hindlimb muscle nerve branches–the medial and lateral gastrocnemius nerves, muscle branches of the deep peroneal nerve, muscle branches of the femoral nerve, and a nerve to the hamstring muscles–were studied with transganglionic transport of horseradish peroxidase (HRP), in the rat. The influence of varying the postoperative survival (3, 6, and 10 days) and of using wheat germ agglutinin‐HRP conjugate (WGA‐HRP), or HRP with dimethylsulfoxide (DMSO) instead of free HRP was studied for the gastrocnemius nerves. After 3 days' survival following application of HRP to the gastrocnemius nerves, fine granular labeling was found mainly in lamina V in L4–5, and coarse granular labeling was found in Clarke's column as far caudally as L2, and in laminae VI and VII predominantly in Th12–L2. After 6 or 10 days' survival, the fine labeling in lamina V was sparse or absent, whereas the coarse labeling appeared to remain or to be only slightly reduced in Clarke's column and in laminae VI and VII. No labeling suggestive of terminals was observed in laminae I‐III from the gastrocnemius nerves. Except for sparse labeling in lamina I in some of the cases and some minor differences rostro‐caudally, the spinal distribution of labeling was similar to that from the other nerves investigated. The distribution of labeling obtained after application of WGA‐KRP or HRP with DMSO to the gastrocnemius nerves was very similar to that obtained with free HRP after 3 days' survival.

The results indicate that the spinal cord projections of hindlimb muscle nerves in the rat distribute mainly in the deep part of the dorsal horn and in the intermediate zone. Furthermore, the lack of labeling suggestive of terminals in laminae I–III from the gastrocnemius nerves suggests, in conflict with earlier findings in the cat, that primary afferent fibers from muscles do not necessarily terminate in these laminae in the rat. The results suggest, furthermore, that fine granular labeling found in lamina V represents fine‐calibered afferent fibers. Finally, the similar spinal projection patterns of the different muscle nerves investigated suggest either a less developed or an essentially different somatotopic organization for muscle afferents compared to cutaneous afferents, as revealed in earlier studies.
[125I] triiodothyronine in the rat brain: Evidence for neural localization and axonal transport derived from thaw‐mount film autoradiography
Authors: Dratman Mary B. , Crutchfield Floy L. , Futaesaku Yutaka , Goldberger Michael E. , Murray Marian
Published: January 2005

Previous thaw‐mount light microscopic autoradiographic studies have shown that intravenously administered [125I] triiodothyronine is saturably concentrated and retained for at least 10 hours in discrete neural systems in the rat brain. To survey the brain more completely and to gain information about the time course of labeling, serial thaw‐mount film autoradiograms were prepared from rat brains obtained at intervals through 48 hours after intravenous injection of high specific activity [125I] triiodothyronine. Parallel biochemical studies of whole brain homogenate extracts revealed that, at all time intervals, the label in the brain was mainly due to triiodothyronine itself (80%), or other organic iodocompounds (15%), but probably not due to free [125I] iodide (3%), which is rapidly transported out of the brain. The highly reproducible, well‐defined labeling patterns seen on film indicated a widespread but selective localization of the hormone. At early times after intravenous injection of [125I] triiodothyronine, label was nonuniformly and prominently concentrated in selected regions of gray matter; evidence for saturability of hormone processing was obtained in competition studies with unlabeled triiodothyronine. Discrete labeling of fiber tracts (usually after 10 hours) left some regions of white matter conspicuously unlabeled. At 48 hours, many originally labeled gray regions showed markedly diminished or virtually complete loss of radioactivity, whereas others became newly or more prominently labeled. At that time, certain fiber tracts were also conspicuously labeled. The observed changing profiles of regional labeling over time are best explained by movement of the hormone from original sites of saturable incorporation in specific nuclei, to terminal fields, through the mechanism of axonal transport.
Efferent projections of the subthalamic nucleus in the rat: Light and electron microscopic analysis with the PHA‐L method
Authors: Kita H. , Kitai S. T.
Published: January 2005

Efferent projections of rat subthalamic nucleus were studied by use of the axonal transport of phaseolus vulgaris‐leucoagglutinin (PHA‐L), and the results were analyzed with light and electron microscopes. PHA‐L injections in the subthalamic nucleus (STH) resulted in heavy labeling of fiber plexus with en passant boutons and terminals in the pallidal complex, i.e., the entopeduncular nucleus (EP), the globus pallidus (GP) and the ventral pallidum (VP), and the substantia nigra pars reticulata (SNR). Labeling in GP was characterized by two distinct bands of labeled terminals oriented dorsoventrally, whereas labeling in SNR was patchy. STH efferents to the pallidum and SNR, displayed a mediolateral topographic organization. With regard to dorsoventral organization, projections to GP were inverted, but those to SNR were not. There were moderate projections to the neostriatum and sparse projections to the frontal cortex, substantia innominata, substantia nigra pars compacta (SNC), pedunculopontine tegmental nucleus, ventral part of the central gray matter including the dorsal raphe nucleus, and the mesencephalic and pontine reticular formation.

PHA‐L injections in the zona incerta and the lateral hypothalamic area resulted in fiber and terminal labelings in many structures, including the basal forebrain, EP, SNC, and other brainstem areas that overlap with some of the terminal sites of STH projections.

Ultrastructural observations of PHA‐L labeled processes in GP and SNR revealed that STH terminals in both structures contained small pleomorphic vesicles and formed asymmetrical contacts. These contacts were mainly on dendritic shafts, but some were on somata. It also was observed that the myelinated axons of STH neurons lost their myelin after reaching their target areas and the synaptic boutons arose from relatively thin unmyelinated axons.
Morphometric study of the anteroventral cochlear nucleus of two mouse models of presbycusis
Authors: Willott James F. , Jackson Leslie M. , Hunter Kelly Paris
Published: January 2005

The dimensions and volume of the anterior ventral cochlear nucleus (AVCN), the density and number of AVCN neurons, and the size of neuronal somata nuclei (in Nissl‐stained tissue) were determined in two mouse models of age‐related hearing loss: the C57BL/6J strain, which undergoes progressive chronic sensorineural hearing loss with onset during young adulthood, and the CBA/J, which demonstrates only moderate hearing loss with onset late in life. Frontal and horizontal AVCN sections, as well as cochleas, were analyzed in 4 C57 age‐groups (1, 7, 12, 19+ months) and in 3 CBA groups (1, 10, 22 months).

Within each strain no significant changes in AVCN dimensions or volume occur with aging. In C57 mice, packing density and cell number decrease between 1 and 7 months, but remain stable thereafter, despite chronic severe hearing impairment. CBA mice show a reduction in AVCN cell number and packing density only during the second year of life. In aging C57 mice, the size of spherical and perhaps globular cells increases, whereas the size of multipolar cells tends to decrease slightly. In CBA mice, all three AVCN cell types tend to decrease in size with aging. The early cell loss and cell size increases in C57 mice are most consistent in the dorsal (high frequency) region of the AVCN. Likewise, loss of cochlear spiral ganglion cells is most pronounced in the base of the cochlea, which provides input to this region. The data indicate that aging is associated with rather different central effects, depending on AVCN cell type, cochleotopic organization, genotype, and/or the type of peripheral hearing loss involved.

The C57 and CBA AVCNs also differ in several aspects irrespective of age. The volume of AVCN and number of AVCN neurons are significantly greater in C57 mice.