bluuebunny/crossref_metadata_2025 huggingface dataset:
Light and electron microscopic immunocytochemical localization of parvalbumin in the dorsal lateral geniculate nucleus of the cat: Evidence for coexistence with GABA
Authors: Stichel C. C. , Singer W. , Heizmann C. W.
Published: January 2005

The coexistence in individual neurons of parvalbumin and γ‐aminobutyric acid (GABA) was studied in the dorsal lateral geniculate nucleus (dLGN) of the cat using pre‐ and postembedding immunocytochemical methods.

PV(+) cell bodies and processes were found in the perigeniculate nucleus (PGN) and throughout all laminae of the dLGN. PV(+) neurons were relatively small and had circular to fusiform shapes. Electron microscopy revealed PV(+) reaction product within the perikarya, axons, and dendrites of labeled cells. It was associated preferentially with microtubules, postsynaptic densities, and intracellular membranes. PV(+) presynaptic boutons were identified on the basis of their synaptic relations and ultrastructure as retinal terminals (RLP) and as profiles originating from inhibitory interneurons (F1 and F2). Immunopositive somata and dendrites received asymmetric synaptic contacts from labeled RLP and non‐identified, non‐immunoreactive synaptic boutons. Moreover, PV(+) dendrites were postsynaptic to labeled F profiles.

In the PGN all neurons were both PV(+) and GABA‐immunoreactive and in the dLGN the vast majority of PV(+) neurons showed GABA‐immunoreactivity.

It is suggested that the high incidence of PV in GABAergic neurons is related to the particular activation patterns of these neurons and the resulting demand for calcium buffer systems.
Sympathetic innervation of the rat cornea as demonstrated by the retrograde and anterograde transport of horseradish peroxidase–wheat germ agglutinin
Authors: Marfurt Carl F.
Published: January 2005

The sympathetic innervation of the rat cornea was studied by using the method of intraaxonal transport of horseradish peroxidase–wheat germ agglutinin conjugate (HRP‐WGA). In the first set of experiments, the relative number of superior cervical ganglion neurons that innervate the rat central cornea was estimated by the method of retrograde HRP‐WGA transport. Following tracer application to the scarified central corneal surface, 49–198 labeled neurons were observed in the ophthalmic region of the ipsilateral trigeminal ganglion and zero to four cells in the rostral pole of the ipsilateral superior cervical ganglion. In the second set of experiments, the three‐dimensional distribution and termination sites of the corneal sympathetic nerve fibers were investigated by the technique of HRP‐WGA anterograde transport from the superior cervical ganglion. HRP‐WGA‐labeled axons in corneal whole mounts were identified by the presence within their axoplasm of linear arrays of HRP‐TMB reaction product, and their distribution was plotted faithfully onto line drawings made with a drawing tube attachment. Large numbers of HRP‐labeled fibers were found in all animals within the corneoscleral limbus where the majority were associated with blood vessels. Fewer fibers (zero to 14 per animal) entered the cornea proper. The latter fibers entered the peripheral cornea in the deep to middle layers of the stroma and ascended into progressively more superficial layers as they coursed centrally. The majority of fibers branched infrequently in the peripheral cornea and increased in branching complexity near the central cornea. HRP‐labeled axonal varicosities suggestive of terminal and preterminal expansions were located preferentially in the subepithelial layer of the corneal stroma and in the basal epithelium. Approximately 75% of the axonal varicosities were located in the central half of the cornea.

The results of the current investigation reveal that the rat cornea is innervated sparsely by sympathetic nerve fibers derived from the superior cervical ganglion. These data provide additional support to current theories that corneal sympathetic nerve fibers may influence select aspects of corneal physiology, including ion transport and hydration, mitogenesis and wound healing, and sensitivity.
Organization of the spinocervicothalamic pathway in the rat
Authors: Giesler G. J. , Björkeland M. , Xu Q. , Grant G.
Published: January 2005

We used silver degeneration techniques to examine the termination of the spinocervical and cervicothalamic tracts in rats. Lesions of the dorsal portion of the lateral funiculus (DLF) of the spinal cord produced degeneration of a relatively small number of ascending fibers that were seen within the most lateral portion of the DLF rostral to the lesion. Within the lateral cervical nucleus, the degeneration was more extensive mediolaterally and of a finer caliber. Such labeling is attributable to the degeneration of fine fibers and terminals. Degenerating processes could be seen in apposition to neurons in the lateral cervical nucleus. At all levels of the cord, the lateral spinal nucleus was devoid of terminal labeling following lesions of the DLF. No terminal degeneration could be seen within the DLF at levels rostral to the lateral cervical nucleus. Lesions of the DLF at either midcervical or lower thoracic levels produced degeneration throughout the lateral cervical nucleus. This finding suggests that the lateral cervical nucleus of the rat is not somatotopically organized.

Lesions of the lateral cervical nucleus produced degeneration of a small number of fibers within the contralateral midbrain and thalamus. Within the mesencephalon, degenerating fibers and terminals were seen primarily in the intercollicular region and the deep layers of the superior colliculus. Less degeneration was found in the lateral portion of the central gray. Within the diencephalon, a small area of termination was located in the ventromedial part of the rostral portion of the medial geniculate nucleus. A prominent termination was present in a restricted area within the caudal fourth of the ventrobasal complex.
Mesodiencephalic projections to the vestibular complex in the cat
Authors: Spence Sandra J. , Saint‐Cyr Jean A.
Published: January 2005

The distribution of cells in the rostral medial mesencephalon and caudal diencephalon which project to the vestibular complex was mapped in the cat by using retrograde axonal transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP). Subsequent experiments using anterograde transport of WGA‐HRP clarified the position of the terminations of the mesodiencephalic‐derived afferents in the vestibular complex.

After large injections which involved the entire vestibular complex, retrogradely labeled cells were seen in both the ipsilateral and contralateral interstitial nucleus of Cajal (INC) and were more numerous in its rostral pole. Labeled cells also occurred in the perifascicular region, both immediately adjacent to the fasciculus retroflexus and rostroventral to it. Fusiform midline cells of the Edinger‐Westphal nucleus were also labeled, as well as a number of cells in the adjacent somatic portion of the oculomotor complex (OMC). Another group of labeled cells was observed within the contralateral medial terminal nucleus of the accessory optic tract (MTN) and in the posterior hypothalamic nucleus. Injections limited to subregions of the vestibular complex resulted in similar but slightly varying distributions and numbers of retrogradely labeled cells. After injections covering the caudal half of the medial vestibular nucleus (MVN) and descending vestibular nucleus (DVN), labeled cells in the INC and tegmentum dorsal to it were especially prominent, but none was seen in the MTN or OMC. Injections placed in the rostral MVN, lateral vestibular nucleus, y group, and superior vestibular nucleus resulted in a distribution of labeled cells similar to that seen following global vestibular injections, but these cells were fewer in number. After an injection confined to the y group, a small number of retrogradely labeled cells were seen in the rostral pole of the INC and immediately ventral to the fasciculus retroflexus.

Projections from the rostral medial mesencephalon and caudal diencephalon to the MVN, DVN, and y group were confirmed by using anterograde transport of WGA‐HRP.

Direct projections from the INC‐perifascicular regions and somatic neurons of the OMC to the caudal vestibular complex could play a role in eye‐head coordination. Those projections from the rostral INC and MTN to the rostral vestibular complex may play a role in vertical eye movements and responses to visual stimuli which move in the vertical plane.
Retinal projections to the pretectum in the pigeon (columba livia)
Authors: Gamlin Paul D. R. , Cohen David H.
Published: January 2005

The retinal projection to the pretectum in the pigeon has previously been described in detail only by means of anterograde degeneration techniques (Repérant, '73). The present study reinvestigated these retinal projections by using the more sensitive anterograde autoradiographic technique. In general, our results confirm and extend those of Repérant ('73). We have found that three pretectal nuclei–the nucleus lentiformis mesencephali, tectal gray, and the area pretectalis– receive heavy retinal input. A fourth pretectal nucleus, pretectalis diffusus, receives a slight retinal input. The nucleus lentiformis mesencephali can be divided into two closely apposed subnuclei that are cytoarchitecturally similar. We have termed them “lentiformis mesencephali, pars medialis” and “lentiformis mesencephali, pars lateralis.” The tectal gray can be divided into a rostral, retinorecipient region and a narrow, caudal, nonretinorecipient region. The cytoarchitecture and retinal terminal field in area pretectalis have been described previously by us (Gamlin et al., '84). Pretectalis diffusus is located caudal to the retinorecipient dorsal thalamus and rostral to area pretectalis.

Localized retinal injections of 3H proline delineated the number and extent of the retinal representations in the pretectum. Separate retinal representations were present in lentiformis mesencephali, pars medialis, lentiformis mesencephali, pars lateralis, the tectal gray, area pretectalis, and pretectalis diffusus. Only in the lentiformis mesencephali, pars medialis, lentiformis mesencephali, pars lateralis, and the tectal gray could the retinal representations be analyzed. Whereas the retinal representations in the lentiformis mesencephali, pars medialis and the tectal gray are comparable, the retinal representation in the lentiformis mesencephali, pars lateralis is different, being a mirror‐image mediolaterally.

In this study we introduce a conservative nomenclature for the retinorecipient pretectal nuclei that is consistent with earlier studies, in particular, those of Kuhlenbeck ('39), but has been modified in the light of our findings. We believe that this nomenclature, combined with the detailed cytoarchitectural descriptions provided, should facilitate future studies of the avian pretectum.
Catecholaminergic subpopulation of retinal displaced ganglion cells projects to the accessory optic nucleus in the pigeon (Columba livia)
Authors: Britto Luiz R. G. , Keyser Kent T. , Hamassaki Dania E. , Karten Harvey J.
Published: January 2005

In birds, displaced ganglion cells (DGCs) constitute the exclusive source of retinal input to the nucleus of the basal optic root (nBOR) of the accessory optic system. Tyrosine‐hydroxylase (TH) immunoreactivity was examined in the pigeon retina after injections of rhodamine‐labeled microspheres into the nBOR. A population of about 400 DGCs was observed in each case to exhibit both TH immunoreactivity and rhodamine bead fluorescence. This corresponded to about 10–15% of the total number of identified DGCs in each retina. Double‐labeled cells were medium‐ to large‐size (12 to 20 μm in the largest axis) and were always located at the border between the inner nuclear and the inner plexiform layers. Their dendrites could be followed horizontally in lamina 1 of the inner plexiform layer for up to 300 μm from the cell body. The distribution of double‐labeled DGCs appeared to be mostly peripheral, matching the overall distribution of identified DGCs. Larger DGCs (21–28 μm) were never seen to contain TH immunoreactivity. Examination of brain sections revealed plexuses of thin varicose TH‐positive axons in all subdivisions of the nBOR. Unilateral enucleation produced an almost complete elimination of TH immunoreactivity in the contralateral nucleus. Such results suggest the existence of a population of catecholaminergic DGCs projecting into the accessory optic system of the pigeon. They also support the emerging hypothesis concerning the neurotransmitter heterogeneity of ganglion cells in the vertebrate retina.
Postembryonic development of the dorsal ocellus of the american cockroach
Authors: Toh Yoshihiro , Yokohari Fumio
Published: January 2005

Postembryonic development of the dorsal ocellus of the cockroach Periplaneta americana was examined. Small ocelli (20 μm in diameter) with less than 100 cells in the newly hatched nymph become adult ocelli (more than 500 μm in diameter) with more than 10,000 retinular cells, through ten to 11 nymphal stages. Thus, sequential steps of morphogenesis of rhabdomeres from loose interdigitations of apposed cell membranes to regularly arranged microvilli can be seen in the nymphal ocelli. Some retinular axons appear to extend into the brain as a bundle in the first‐instar nymph. Retinular axons differentiated later also extend toward the brain, but there is no evidence that they enter it. The ultrastructure of the ocellus and component analysis of the ocellar electroretinogram suggest that functional connections between retinular axons and ocellar interneurons do not occur in the ocellar capsule until mid (the fifth or sixth)‐instar nymphs. The ocellar diameter increases linearly with increase in body length during the nymphal stages, but it increases by a factor of 1.5–2.0 during the final molting: the body length of the adult is almost the same as that of the last‐instar nymph. These data suggest that the function of the dorsal ocelli may be closely related to specific adult behavior such as flight.
Patchy intrinsic projections in visual cortex, area 18, of the cat: Morphological and immunocytochemical evidence for an excitatory function
Authors: LeVay Simon
Published: January 2005

Small injections of peroxidase‐labeled wheat germ agglutinin into cat area 18 gave rise to patches of labeled cells and axon terminals around the injection site. In EM sections it was found that the labeled cells had a pattern of synaptic inputs characteristic of spiny‐dendrite neurons (pyramidal or spiny stellate cells). The labeled axon terminals formed type 1 (asymmetric) synapses, most of which were made onto dendritic spines. In other experiments injections of fluorescent beads were made into area 18, giving rise to a similar patchy distribution of labeled cells. The sections were then processed for immunocytochemical demonstration of γ‐aminobutyric acid (GABA). The bead‐labeled cells in the patches were GABA negative. The findings suggest that the patchy projections mediate mutual excitation between groups of spiny‐dendrite neurons.
Distribution of cholecystokinin‐immunoreactive cell bodies in the male and female rat: II. Bed nucleus of the stria terminalis and amygdala
Authors: Micevych Paul , Akesson Thomas , Elde Robert
Published: January 2005

The distribution of cholecystokinin‐immunoreactive (CCK‐I) cell bodies was studied in the bed nucleus of the stria terminalis (BST) and amygdaloid complex of colchicine‐treated male and female rats. Immunoreactive cells were visualized in the BST medial amygdaloid (MeA), central lateral, basolateral, basolateral ventral, medial, intercalated, anterior cortical, and posterior cortical nuclei and the amygdalohippocampal zone. Several significant sex differences were observed. In the male, a dense aggregation of CCK‐I cell bodies was visualized in the MeA, especially in the dorsocaudal part and in the encapsulated part of the BST. In comparison, female rats had relatively fewer immunoreactive cells in both of these regions. In the lateral and basolateral amygdaloid nuclei, however, more CCK‐I cells were visualized in the female than in the male, but the difference was not statistically significant. These data provide characterization of a sexually differentiated CCK system. In addition, we observed that the number of CCK‐I cells in the BST and posterodorsal part of the MeA was substantially reduced after castration. The number of CCK‐I cells in female rats, however, was not significantly reduced after ovariectomy in any of the regions studied. These findings imply that the steroid regulation of CCK is sexually differentiated. The sexually dimorphic distribution of CCK‐I cells in areas that are targets of steroid hormones and regulate reproductive processes is consistent with the possibility that CCK participates in central integration of sensory and steroidal input that modulates reproductive behavior.
Ultrastructure of mouse vallate taste buds: III. Patterns of synaptic connectivity
Authors: Kinnamon John C. , Sherman Terri A. , Roper Stephen D.
Published: January 2005

We have used serial high voltage electron micrographs and computergenerated, three‐dimensional reconstructions to study morphological relationships and patterns of synaptic connectivity in taste buds from the circumvallate papillae of the mouse.

The intragemmal arborizations of 40 sensory nerve fibers were examined from 7 taste buds that were sectioned serially. We identified the synaptic connections from taste cells onto the reconstructed nerve fibers and classified the presynaptic taste cells based on previously established ultrastructural criteria. From these data we were able to extract the following information for the reconstructed nerve fibers: (1) the morphology of intragemmal nerve fibers and their arborizations within the taste bud, (2) the total number of synaptic connections from taste bud cells onto the nerve fibers, and (3) the taste cell types associated with each of the synapses.

Fifty‐six synapses were studied. Synapses were often found to be located at either the branch points or terminations of nerve fiber processes. The maximum number of taste cells observed to synapse onto a single nerve fiber was 5. Several nerve fibers had no apparent synapses. Dark cells (type I), intermediate cells, and light cells (type II) all formed synaptic connections with sensory nerve fibers. In no cases did dark cells and light cells synapse onto the same sensory nerve fiber. Our observation that any given nerve fiber receives its synaptic input from morphologically similar taste cells provides evidence for specificity in taste bud synaptic connections. We speculate that the observed pattern of synaptic connections is related to taste bud function. Since all of the synapses onto a given nerve fiber are from morphologically similar taste cells, we postulate that there is a correlation between taste cell morphology and sensory responsiveness. Intracellular electrophysiological studies on taste cells, in which responses to focally applied chemical stimuli are followed by characterization of the ultrastructural features of the same taste cells, will prove or disprove this hypothesis.
Axonal domains within shared touch domes in the rat: A comparison of their fate during conditions favoring collateral sprouting and following axonal regeneration
Authors: Yasargil G. M. , Macintyre L. , Doucette R. , Visheau B. , Holmes M. , Diamond J.
Published: January 2005

Low‐threshold mechanosensory nerves in the adult rat differ both from their counterparts in lower vertebrates and from high‐threshold nociceptive nerves in mammals in that they appear not to undergo collateral sprouting into adjacent denervated skin, although they will clearly regenerate into it after they are damaged. We have now studied the growth capabilities of the low‐threshold nerves supplying touch domes, the visible mechanosensory structures scattered throughout the hairy skin. Touch domes in the rat are often multiply innervated. A serendipitous observation on such domes allowed us to investigate the possibility that a functional collateral sprouting of their nerves can indeed occur, but only to a spatially very restricted extent, e.g., within the confines of a partially denervated dome. We used a “prodder” with a tip diameter of 16 μm to examine the mechanosensory profile across single domes that were preselected as being supplied by only two axons, one running in each of two adjacent dorsal cutaneous nerves (DCNs). Simultaneous recordings were made of the afferent discharges evoked in these nerves when the prodder was applied at about 17 or more locations on a selected dome; the spatial resolution was better than 55 μm. We found that within such a shared dome, one axon can supply a discrete territory (its “domain”), which may or may not overlap with the corresponding domain of the other axon. In a preliminary electron microscopic study, we found no evidence for a sharing of single Merkel cells, which are the specialized sensory cells in touch domes, even in the regions of a shared dome where two domains overlapped; each innervated Merkel cell appeared to be contacted by a single nerve ending, implying that in a shared dome each axon probably supplies an exclusive subpopulation of the Merkel cells. We tested for functional collateral sprouting by eliminating one nerve to a shared dome, and at a selected time thereafter mapping the domain of the remaining axon to see whether it had enlarged. The result was the same whether the two domains initially had a region of overlap or not; no expansion of the surviving domain occurred over postoperative periods up to 4 months (an expansion of the domain by 55 μm would have been detected). Thus functional collateral sprouting had failed to occur. In contrast, when the entire DCN containing one of the axons was surgically eliminated, and that containing the other axon crushed and allowed to regenerate, invariably the axon that grew into the now totally denervated dome invaded it extensively, restoring mechanosensitivity to both former domains.

The likelihood that these and related results imply that collateral sprouting and regeneration are evoked by different mechanisms is discussed.
Localization of angiotensin II receptor binding in rabbit brain by in vitro autoradiography
Authors: Mendelsohn F. A. O. , Allen A. M. , Clevers J. , Denton D. A. , Tarjan E. , McKinley M. J.
Published: January 2005

Binding of 125I‐[Sar1, Ile8] angiotensin II (AII) to sections of brains from both wild and laboratory rabbits was determined by in vitro autoradiography. In the forebrain, specific high density binding was observed in the olfactory bulb, organum vasculosum of the lamina terminalis (OVLT), subfornical organ, median eminence, lateral septum, median preoptic nucleus and hypothalamic paraventricular, supraoptic and arcuate nuclei. In the midbrain, binding of the radioligand was observed in the interpeduncular and parabrachial nuclei, in the locus coeruleus, and ventrolateral pons. In the hind brain, there was dense binding of 125I‐[Sar1,Ile8] All to the nucleus of the solitary tract (NTS) and to both rostral and caudal parts of the reticular formation of the ventrolateral medulla oblongata. Weaker specific binding of the radioligand to the molecular layer of the cerebellum, to the nucleus of the spinal trigeminal tract, dorsal motor nucleus of the vagus, area postema, and to a band of tissue connecting the NTS to the ventrolateral medulla was also observed. Binding of the ligand to circumventricular organs such as the OVLT, subfornical organ, and median eminence suggests that these are sites in the brain of the rabbit at which blood‐borne All may exert influences on the central regulation of fluid balance and pituitary hormone secretion, although All of neuronal origin could also act at these sites. Binding of the radioligand in several other brain regions suggests that angiotensin II of cerebral origin may be involved in a number of different aspects of brain function in the rabbit. The finding of dense binding in the NTS and ventrolateral medulla, which are involved in autonomic activity and are also sites of catecholamine‐containing neurons, raises the possibility of angiotensin interaction with these neurons and involvement in autonomic function.
Corticotropin releasing factor‐containing afferents to the lateral septum of the rat brain
Authors: Sakanaka Masahiro , Magari Sumiko , Shibasaki Tamotsu , Lederis Karl
Published: January 2005

Corticotropin releasing factor (CRF)‐containing afferents to the rat lateral septum (LS) have been determined by means of cobalt‐enhanced immunohistochemistry, tracing of retrograde transport of horseradish peroxidase (HRP), and by lesioning experiments.

When unilateral lesions included the rostral part of the hypothalamus, CRF‐like immunoreactive (CRFI) ipsilateral fibers in the LS decreased in number. Lesions in other brain regions did not cause alterations in the septal CRFI fibers. These findings suggest that the septal CRFI fibers originate in the rostral part of the hypothalamus. Furthermore, combined HRP and immunohistochemical staining cm the same sections demonstrated double‐labeled cells in two discrete areas within the rostral hypothalamus: one was the perifornical hypothalamic area (PeF) at the level of the paraventricular hypothalamic nucleus, and the other was the most caudal part of the anterior hypothalamic nucleus (AHc). These findings show that a large proportion of the CRFI projections to the LS have their origins in the PeF and AHc.
Neurons containing calcitonin gene‐related peptide in the parabrachial nucleus project to the central nucleus of the amygdala
Authors: Schwaber J. S. , Sternini C. , Brecha N. C. , Rogers W. T. , Card J. P.
Published: January 2005

The source, distribution, and morphology of axons displaying calcitonin gene‐related peptide (CGRP) immunoreactivity in the central amygdaloid nucleus of the adult rat were investigated with immunohistochemical techniques, both alone and in combination with retrograde transport of fluorescent tracers. An extremely dense plexus of CGRP‐immunoreactive axons is differentially concentrated within the lateral capsular and lateral central subdivisions of the central nucleus, and much lighter concentrations of labeled fibers are present in the rostral part of the medial subdivision. No immunoreactive neurons were observed in the central nucleus in any of the experimental animals. The immunoreactive axons characteristically form prominent pericellular terminal arborizations surrounding unlabeled neurons. The number of cells receiving this dense input increases at caudal levels of the central nucleus. Retrograde label of central nucleus neurons by dye transport from injections into the pontine parabrachial nucleus and the nucleus of the tractus solitarius combined with CGRP immunohistochemistry established that many neurons in the central nucleus which receive dense pericellular innervation from CGRP‐immunoreactive axons are projecting caudally to the parabrachial nucleus or, to a lesser extent, to the nucleus tractus solitarii. Central amygdaloid injections of rhodamine‐labeled microspheres or fluorogold followed by immunohistochemical localization of cellular CGRP immunoreactivity revealed that the central amygdaloid CGRP fiber plexus originates bilaterally from the parabrachial nucleus. These multipolar CGRP‐containing neurons are preferentially concentrated in the external medial and external lateral subnuclei, in the ventral aspect of the parabrachial nucleus. These results relating central amygdaloid CGRP to ascending and descending brainstem pathways, taken together with the extreme density of the fiber plexus, strongly suggest the relevance of the CGRP input to central nucleus function in cardiovascular and other autonomic regulation.
Retinal projections to the superior colliculus and dorsal lateral geniculate nucleus in the tammar wallaby (Macropus eugenii): I. Normal topography
Authors: Flett D. L. , Marotte L. R. , Mark R. F.
Published: January 2005

The topography of retinal projections to the superior colliculus and dorsal lateral geniculate nucleus of a wallaby, the tammar (Macropus eugenii), was investigated by an anatomical method. Small laser lesions were made in the retinas of experimental animals, and the remaining retinal projections were visualized by means of horseradish‐peroxidase histochemistry. The position of each lesion was correlated with the position of the filling defects in the terminal label.

The whole of the retina projects to the contralateral superior colliculus. The nasal retina is represented caudally, and the temporal retina rostrally. The ventral retina is represented medially, and the dorsal retina laterally. There is a projection to the ipsilateral superior colliculus, but it is patchy and its topography could not be determined by this method. The retinotopic map in the contralateral dorsal lateral geniculate nucleus has the nasal retina represented rostrally and the temporal retina caudally in the nucleus. The dorsal retina is represented ventrally, and the ventral retina is represented dorsally. It appears that the whole of the retina projects contralaterally, and in addition the temporal retina projects ipsilaterally. The maps of visual space through the two eyes were shown to be in topographic register in the binocular region by making a deposit of HRP in the visual cortex. This resulted in a column of retrogradely labeled cells in the nucleus. This column crossed the laminae, which are innervated by the ipsilateral and contralateral eye at right angles.
Retinal projections to the superior colliculus and dorsal lateral geniculate nucleus in the tammar wallaby (Macropus eugenii): II. Topography after rotation of an eye prior to retinal innervation of the brain
Authors: Marotte L. R. , Mark R. F.
Published: January 2005

Retinal projections to visual centers in a marsupial mammal, the tammar wallaby (Macropus eugenii), have been investigated after an eye rotation prior to retinal innervation of the brain. Retinal topography to the superior colliculus and dorsal lateral geniculate nucleus was mapped by using laser lesions of the retina and horseradish peroxidase histochemistry. Despite the change in orientation of optic axon outgrowth from the developing eye after rotation, retinal ganglion cells made orderly connections in the colliculus and geniculate according to their original retinal position within the eye and not their rotated position. Axons must have corrected their pathways at some point between the back of the eye and their targets. The optic chiasm was one such site. Optic axons from the rotated eye took an abnormal course at the caudal end of the chiasm.

Growth of optic axons through aberrant pathways in the brain did not preclude specific innervation of targets. When by chance optic axons entered through the oculomotor nerve root they specifically innervated their correct visual centers, albeit in reduced density, and did not innervate inappropriate targets. These results support the idea of specific interactions between growing axons, the pathways they grow along, and their targets.
Morphological identification of an interneuron in the hypoglossal nucleus of the rat: A combined Golgi‐electron microscopic study
Authors: Takasu Nobuo , Hashimoto Paulo H.
Published: January 2005

Hypoglossal small neurons of adult and juvenile (10–15‐day‐old) rats were examined by a combined Golgi–electron microscopic technique. In adult rats, Golgi‐impregnated neurons were fusiform or ovoid (17 × 12 μm) and emitted a few primary dendrites with few branches and few spines and an axon mainly from the proximal portion of the primary dendrite. At the ultrastructural level, the soma displayed an invaginated nucleus with a conspicuous nucleolus and a relatively scanty cytoplasm in which cisternae of rough endoplasmic reticulum were not organized into extensive lamellar arrays. A moderate number of axon terminals, which contained spherical clear or pleomorphic vesicles ∼ 25–40 nm in diameter, formed symmetric or asymmetric synapses on the soma, the dendrites, the axon hillock, and the initial segment. In a preparation from the juvenile rat, we could trace a full axon trajectory of the small neuron. In this sample, in which a small neuron and a motoneuron were simultaneously impregnated, the axon of the small neuron was found to receive an axoaxonic symmetric synapse with pleomorphic vesicles on a varicosity and to contact the motoneuron dendrites by means of another varicosity of the main axon and of two boutons from an axon collateral. The varicosity and the boutons contained pleomorphic synaptic vesicles and synapsed symmetrically with the motoneuron dendrites. We identified the small neuron in the rat hypoglossal nucleus morphologicaly as a Golgi type II interneuron. We discuss its function in relation to the GABAergic nature of small neurons (Takasu et al.: J. Comp. Neurol. 263:42–53, ′87).
Ultrastructure of synaptic remodeling in piriform cortex of adult rats after neonatal olfactory bulb removal: An immunocytochemical study
Authors: Westenbroek R. E. , Westrum L. E. , Hendrickson A. E. , Wu J.‐Y.
Published: January 2005

The purpose of this investigation was to study possible remodeling in synaptic structures of the piriform cortex (PC) of adult rats following neonatal deafferentation by removal of the olfactory bulb (OB) at birth. Emphasis was placed on possible qualitative changes in the ultrastructure and immunocytochemical localization of cholecystokinin (CCK, a possible excitatory neurotransmitter or modulator) and glutamic acid decarboxylase (GAD, precursor enzyme to the inhibitory transmitter GABA in axons, terminals, and synaptic complexes. Light microscopic results in normal adult material show that GAD‐positive terminals form a dense band subjacent to the lateral olfactory tract (LOT), become less dense in deeper Ib, and are rare in layer II. Following deafferentation, GAD‐positive terminals appear denser and more homogeneously distributed throughout layer I and are also more prevalent in layer II. Ultrastructural results of normals and controls indicate GAD‐positive terminals normally contain pleomorphic or flattened vesicles and form symmetric contacts onto dendritic shafts and branches throughout layer I. In deafferented layer I not only do there appear to be greater numbers of symmetric GAD‐positive contacts, but in contrast to normals, asymmetric contacts mainly onto spines are now present. Light microscopic results from deafferented material also show an apparent proliferation with spread or sprouting of CCK‐positive fibers or axonlike structures mainly into layer Ia, whereas these fibers are normally observed only in the LOT and are generally few in number. Also in normals the few CCK‐positive terminals in the area subjacent to the LOT contain flattened or pleomorphic vesicles and form symmetric contacts. Deafferentation results in CCK‐positive terminals throughout layer I with a greater frequency of synaptic contacts which now also include a few asymmetric contacts onto spines. The findings clearly show modifications in synaptic patterns of immunocyto‐chemical‐labeled terminals that might be compatible with the process of atypical reinnervation of deafferented postsynaptic sites and possible ingrowth of new axons.
Development of the rat thalamus: I. Mosaic organization of the thalamic neuroepithelium
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

Short‐survival, sequential, and long‐survival thymidine radiograms of rat embryos, fetuses and young pups were analyzed in order to delineate the boundaries of the proliferative thalamic neuroepithelium, describe its early transformations, identify its regional divisions, and, finally, attempt to relate its distinct neuroepithelial components to specific thalamic nuclei that they supply with neurons. On day E13 the thalamic neuroepithelium consists of two divisions, the rostral lobe and the caudal lobe, and interposed between the two is a small transient structure, the reticular protuberance. By day E14 the rostral lobe has become partitioned into the anterior lobule and the reticular lobule, and the caudal lobe into the intermediate lobule and the posterior lobule. By day E15 these four lobules have become further partitioned into sublobules, characterized as regional eversions and inversions (concavities and convexities) of the thalamic neuroepithelium. Several of these sublobules are still recognizable on day E16 but progressively disappear thereafter.

In this introductory paper, some evidence is presented in support of the hypothesis that the identified thalamic sublobules represent putative cell lines committed to produce neurons for specific, early‐generated thalamic nuclei. Detailed documentation of the evidence on which the identifications are based is provided in subsequent papers of this series which deal with the early development of specific thalamic regions and nuclei. In our attempt to identify these putative cell lines, we sought to meet the following criteria: (1) a good match between the time course of mitotic activity in a neuroepithelial sublobule and the birth days of neurons in the nucleus that it is postulated to supply with neurons, (2) relative proximity between the putative neuroepithelial source and the thalamic target structure, and, where possible, (3) the tracing of migrating cells from the germinal source to its destination. Using these criteria we have made the following tentative identifications. The early derivatives of the anterior thalamic lobules are the sublobules (committed cell lines) of the anterior thalamic nuclei, and of the central lateral and mediodorsal nuclei. The early derivatives of the reticular lobule and reticular protuberance are the sublobules of the reticular nuclear complex. The early derivatives of the intermediate lobule are the sublobules of the ventrolateral and ventrobasal nuclei. Finally, the early derivatives of the posterior lobule are the sublobules of the dorsal geniculate, ventral geniculate, and medial geniculate nuclei. The proposed partitioning and mosaic organization of the thalamic neuroepithelium are discussed with reference to traditional descriptions.
Evidence of intracerebellar collateralization of nucleocortical cell processes in a prosimian primate (Galago): A fluorescence retrograde study
Authors: Haines D. E.
Published: January 2005

The distribution of single and/or double‐labeled neurons in the cerebellar nuclei was investigated in a prosimian primate (Galago) by means of fast blue (FB) and nuclear yellow (NY) as retrograde tracers. Injections were made into spatially separate regions of cerebellar cortex on one side (zones C1−C3 in lobules IV and V and in the paramedian lobule) and into the same zones of lobules IV and V on both sides. Following unilateral injections single‐ and double‐labeled somata were seen in the anterior (NIA) and posterior (NIP) interposed cerebellar nuclei on the same side. Single‐labeled cells were, in general, more concentrated in NIA from the lobule IV‐V injection and in NIP from the PML placement; double‐labeled somata were about evenly distributed between NIA and NIP. Cell labeling was sparse in the contralateral NIP. Large and small somata were filled with FB, NY, or FB+NY ipsilateral to the injection sites while the majority of labeled neurons on the contralateral side had small oval‐ or fusiform‐shaped somata. Subsequent to bilateral injections cells labeled with each tracer were concentrated in the NIA, moderate in number in the NIP, both on the ipsilateral side, and sparse in the contralateral NIP.

The double labeling of cells in the present study indicates that these neurons project to spatially separated, yet possibly functionally related, areas of ipsilateral cortex. Since larger and small somata were double labeled it is possible that those cells with cerebellofugal processes to extracerebellar targets may simultaneously relay information to divergent cortical sites. In contrast, the few labeled cells seen in the contralateral NIP have small oval and fusiform somata. These neurons may be specifically involved in cerebelloolivary and olivocerebellar feedback loops.
Development of substance P‐containing neurons in the central nervous system in mice: An immunocytochemical study
Authors: Ni Li , Miller Jonakait G.
Published: January 2005

The embryonic development of substance P (SP) in the central nervous system (CNS) of mice has been studied with the use of peroxidase antiperoxidase (PAP) immunocytochemistry. Immature SP‐positive cells initially appear at embryonic day 12 (E12) in the epithalamus and in a column of cells extending from the myelencephalon throughout the length of the neural tube. By E13, SP‐positive cells appear in the amygdaloid nuclear complex, the bed nucleus of the stria terminalis, and in the caudal medulla. Fibers are first detected in the stria terminalis at this age. Over the next 48 hours, a plethora of SP‐positive cells appears throughout the CNS, notably in the septal area, diagonal band nucleus, piriform cortex, accumbens nucleus, hypothalamus, rostral striatum, superior and inferior colliculi, intercollicular nucleus, substantia nigra, interpeduncular nucleus, vestibular nuclei, spinal nucleus of the trigeminal, and the nucleus of the tractus solitarii. Subsequently, SP‐positive neurons and fibers increase in number and staining intensity except in the medullary raphe where the apparent number of SP‐positive neurons decreases after E16.

Whereas the pattern of SP staining is quite similar in mice and rats, the time of initial detection of SP‐like immunoreactivity in specific nuclei is 1–4 days earlier in mice than that reported in rats with different antisera.
Neural control of leg movements in a metamorphic insect: Persistence of larval leg motor neurons to innervate the adult legs of Manduca sexta
Authors: Kent Karla S. , Levine Richard B.
Published: January 2005

During metamorphosis of the hawkmoth Manduca sexta, the larval thoracic legs along with their associated sensory organs and muscles degenerate and new adult legs develop. The larval legs are small and relatively simple structures capable of lateral extension and medial flexion allowing them to grasp the substrate as the caterpillar crawls along. By contrast, the adult legs are used for walking with an alternating gait. They are much larger than the larval legs and articulate such that they are capable of movement in several directions. This change in form and function is accompanied by a reorganization of the neural circuits controlling leg movements. In a previous report (Kent and Levine: J. Comp. Neurol. 271:559–576, 88) we described motor neurons innervating the larval prothoracic legs, and here we describe motor neurons innervating the prothoracic legs of the adult. Using a combination of cobalt staining methods and the persistent fluorescent dye Fluoro‐Gold, we have found that some, if not all, larval leg motor neurons are retained and innervate the new adult leg muscles. Moreover, we have been able to discover the fate of individual larval leg motor neurons by marking a single larval neuron with Fluoro‐Gold and using a second fluorescent dye to double label the same neuron in the adult. Our results suggest that specific larval leg motor neurons innervate corresponding muscles in the adult stage, although their apparent function is significantly different. In addition, the motor neurons undergo significant remodeling of their dendritic branching patterns during metamorphosis, alterations which doubtless contribute to their new roles in adult behavior.
Two types of tyrosine hydroxylase‐immunoreactive amacrine cell in the rhesus monkey retina
Authors: Mariani Andrew P. , Hokoc Jan N.
Published: January 2005

Two types of amacrine cell immunoreactive for tyrosine hydroxylase (TH), the rate‐limiting enzyme in the catecholamine (CA)‐synthetic pathway, are described in the rhesus monkey retina with the indirect‐immunofluorescent method. These 2 types of neuron differ in soma size, plane of arborization in the inner plexiform layer, levels of the enzyme TH as quantified by microspectrofluorometry, and population density. Type 1 CA cells have comparatively large cell bodies almost exclusively in the innermost row of the inner nuclear layer; their processes arborize in the outermost stratum of the inner plexiform layer; they give rise to fine predominantly radially oriented fibers in the inner nuclear layer; and there are about 26 type 1 CA cells/mm2. Type 2 CA amacrine cells have relatively small cell bodies located in the inner nuclear layer (44.4%), the inner plexiform layer (35.6%) and the ganglion cell layer (20 %), and their processes arborize in the center of the inner plexiform layer. Although type 2 CA amacrine cells are more numerous (35 cells/mm2) than type 1 CA cells, type 1 CA amacrine cells are 3.5 X brighter than type 2 CA cells and therefore likely to contain 3.5 X more TH. Thus the primate retina contains 2 distinct catecholaminergic neuronal pathways that could have different functional roles in vision.
Microsurgical analyses of avian neurulation: Separation of medial and lateral tissues
Authors: Schoenwolf Gary C.
Published: January 2005

Neurulation, formation of the neural tube, is a complex process involving shaping and bending of the neural plate and closure of the neural groove. We have used avian embryos as model systems to study this process. In the present investigation, blastoderms were cut parasagittally through their entire thickness, either unilaterally or bilaterally, at two mediolateral locations: (1) at the juncture between prospective neural plate and prospective surface epithelium, and (2) at the juncture between the midline strip of prospective neural plate and more lateral prospective neural plate. In the first experiment, shaping of the neural plate seemed normal, but elevation and convergence of the neural folds and closure of the neural groove were inhibited (except at the forebrain level). This result demonstrates that extrinsic forces generated by lateral tissues are required for neural plate bending and neural groove closure. In the second experiment, neuroepithelial cells within the isolated, midline strip became wedge shaped. This result indicates that neuroepithelial cell “wedging” is an active event occurring independently of forces generated by elevation of the neural folds. Additional studies are required to define the natures of neurulation forces and the mechanisms by which they are generated.
Neuronal architecture of the nucleus of the solitary tract in the hamster
Authors: Whitehead Mark C.
Published: January 2005

This study provides a scheme for subdividing the nucleus of the solitary tract of the hamster on the basis of cytoarchitectonic criteria, cell measurements, and neuronal cell types identified with the Golgi method. Reduced silver‐stained sections revealed the feltlike neuropil that characterizes the nucleus of the solitary tract and were used to define the boundaries of the nuclear complex. Adjacent sections stained for Nissl substance revealed ten subdivisions, each with a characteristic neuronal architecture based on cell sizes, shapes, and packing density. Some subdivisions, e.g., the ventral and medial subnuclei, were identified at all rostrocaudal levels of the nuclear complex, while other subdivisions, e.g., the caudally located dorsolateral and ventrolateral subnuclei, were restricted to particular levels. Golgi preparations were counterstained for Nissl substance, thus allowing dendro‐ and cytoarchitecture to be compared directly. This material permitted the identification of a number of functionally relevant features of the neuronal constituents of the subdivisions. This approach, employing three cytological methods, has permitted the assembly of a detailed atlas of the nucleus of the solitary tract. The subdivisions of the present atlas have been compared with their likely counterparts identified in previous investigations of the mammalian nucleus of the solitary tract. In order to relate cytoarchitecture with primary afferent termination sites and to define the gustatory‐recipient subdivisions, the differential relationships of the subdivisions with lingual afferent projections in the hamster are also described. The present parcellation scheme is intended to facilitate anatomical and physiological investigations of the types of circuits that compose the medullary gustatory and general visceral sensory systems.