bluuebunny/crossref_metadata_2025_split huggingface dataset:
Afferent influences on brain stem auditory nuclei of the chicken: Cessation of amino acid incorporation as an antecedent to age‐dependent transneuronal degeneration
Authors: Steward Oswald , Rubel Edwin W 
Published: January 2005

AbstractPrevious studies of the avian auditory system have revealed that removal of the peripheral receptor (the cochlea) leads to a transneuronal degeneration of auditory relay neurons in nucleus magnocellularis (NM) of the brain stem. An early manifestation of the degeneration which can be observed within 12 hours is a decrease of histochemical staining for RNA (Nissl staining); such a decrease could relect an alteration in protein synthetic activity within the NM neurons. The present study evaluates this possibility by determining whether the cochlea removal led to an alteration incorporation of protein precursors in the target neurons which exhibit transneuronal degeneration and if so, how early the changes appeared. The cochlea was removed unilaterally in seventeen 10‐day‐old chicks and two 66‐week‐old mature chickens, and incorporation of protein precursors was evaluated in the neurons of NM at 0.5, 1.5, 3, 6, 12, and 24 hours following the cochlea removal. Each chick received an intravenous injection of 3H leucine, and was allowed to survive for 30 minutes after the injection of precursor. The brains were then prepared for autoradiography. The extent of incorporation by neurons in NM was determined by counting grains overlying each cell body and determining grain density/μm2 of neuron cross‐sectional area.We found that auditory relay neurons whose synaptic inputs have been silenced exhibit dramatic decreases in protein synthesis within 30 minutes after removal of the cochlea; leucine incorporation was reduced by about 50%. In chicks sacrificed 3 to 24 hours after removal of the cochlea, some neurons (about 1/3) were entirely unlabeled despite heavy labeling of their neighbors and heavy labeling of all NM neurons on the opposite side of the brain. The remaining neurons exhibited about a 15% reduction in incorporation in comparison with the cells in the contralateral (control) NM. While the decreases in incorporation were apparent at all survival intervals, there was no consistent decrease in Nissl staining until 6 hours after cochlea removal. There were no changes in protein precursor incorporation following removal of the cochlea in adult birds, a result which is in keeping with the relative absence of transneuronal degeneration following removal of the cochlea at maturity. The results suggest a very rapid transneuronal regulation of protein metabolism within target neurons in young animals, perhaps by activity‐related events.
Novel sources of descending input to the spinal cord of the hatchling chick
Authors: Gross Gayle H. , Oppenheim Ronald W. 
Published: January 2005

AbstractNuclear groups contributing supraspinal input to the spinal cord of the hatchling chick (Gallus domesticus) were determined by using the enzyme tracer horseradish peroxidase processed with tetramethylbenzidine histochemistry.Five sources of projections to the spinal cord were found which have not been previously described in any species. All are probably related to autonomic function. They include ipsilateral hypothalamic projections from the lateral mamillary n., suprachiasmatic n., and n. of the lateral tubercle. There is a bilateral projection from the large interstitial cells of the mesencephalic posterior commissure, and in the myelencephalon, a mainly contralateral projection from interstitial cells of the vagus‐glossopharyngeal nerve.Two other projections observed here have not been described in other avian species, one from the accessory vestibular n., the other, from the n. ambiguus. In the cerebellum, projections arise from the main and ventrolateral divisions of the fastigial n., and from “border cells” between the fastigial and interpositus n. The large‐celled submedial vestibular n. projects bilaterally.Several projections previously described only in the pigeon, were confirmed here: the hypothalamic nucleus over the supramammilary decussation, the n. intercollicularis, the tangential n., and the n. alatus, a cell group between the hypoglossal and vagal nuclei.Four sources of input projected only as far as mid‐cervical cord. These are n. intercollicularis, fastigial n., accessory vestibular n., and tangential n. All remaining projections reached to lower lumbosacral cord.Sources of descending input are remarkably similar in mammals and avians. Where homologous nuclei exist, virtually identical projections to the cord are present.
Mapping and ultrastructure of serotonin‐immunoreactive neurons in the optic lobes of three insect species
Authors: Nässel Dick R. , Meyer Eric P. , Klemm Nikolai 
Published: January 2005

AbstractWith antibodies to serotonin (5‐HT) we have mapped immunoreactive neurons in the optic lobes of three insect species, the blowfly Calliphora, the desert ant Cataglyphis, and the worker bee Apis. The main emphasis in this investigation is on a system of 5‐HT‐positive neurons connecting the most peripheral neuropil of the optic lobes, the lamina, to more central neuropil regions. To aid in electron microscopical identification of these neurons we used immunocytochemistry at the EM‐level and Golgi‐EM for Calliphora and horseradish peroxidase (HRP) labelling for the other two insects.The immunoreactive terminals in Calliphora and the HRP‐labelled ones in the other insects contain large (c. 100 nm) granular vesicles and smaller (c.60 nm) clear vesicles. In Cataglyphis and Apis the profiles with granular vesicles are presynaptic to second order neurons of the lamina, whereas in Calliphora no synaptic contacts were found. In this animal the 5‐HT‐positive terminals are situated distal in the synaptic layer of the lamina, in a region of retinal photoreceptor axons and perikarya of the lamina monopolar neurons.In Catagylphis and Apis the interactions of the 5‐HT‐neurons with the laminar neurons might occur through chemical synapses, whereas in Calliphora neuroactive substance could be released non‐synaptically from varicosities distal to the synaptic layer. The possible involvement of 5‐HT in control of neuronal activity in the optic lobes is discussed.
Histological study of motor innervation of nuclear bag1 intrafusal muscle fibers in the cat
Authors: Kucera Jan 
Published: January 2005

AbstractThe nerve supply to spindles of the cat tenuissimus muscle was reconstructed with light and electron microscopy of serial transverse sections. Fifty‐two poles of the nuclear bag1 intrafusal muscle fiber were examined for motor innervation. The fiber poles were supplied by 71 myelinated motor axons that either terminated on bag1 fibers exclusively (93%) or coinnervated a chain fiber of the same intrafusal bundle (7%). No axons coinnervated both the bag1 and bag2 fibers. The unmyelinated preterminal segments of the axons were frequently short. Lengths and pre‐ and postsynaptic features of motor endings on bag1 fibers were variable. These features did not permit reliable classification of the endings into more than one morphological category. Moreover, the terminals of fusimotor (γ) and skeletofusimotor (β) axons on bag1 fibers appeared similar in cross‐section. The degree of indentation of axon terminals into the surface of bag1 fibers increased with increasing distance from the spindle equator. However, cross‐sectional areas of sole plates and axon terminals were relatively constant regardless of distance from the equator. The subjunctional membranes of both γ and β bag1 endings were typically smooth in contour. Bag1 endings differed from those on bag2 and typical chain fibers in having a thicker sole plate, frequently indented axon terminals, and unfolded subjunctional membranes. None of the bag1 endings resembled an extrafusal end plate. These observations indicated that (1) the dynamic (bag1) and static (bag2 and chain) intrafusal systems of the cat spindle are under separate motor control, and (2) the type of intrafusal fiber and the distance of the motor ending from the equator have a greater influence on the form and structure of bag1 endings than do supplying axons.
Ontogeny of the visual system in the cuttlefish, Sepiella japonica. I. Morphological differentiation of the visual cell
Authors: Yamamoto Masamichi 
Published: January 2005

AbstractTo provide morphological bases for functional studies, the differentiation of photoreceptors in the retina of a cuttlefish, Sepiella japonica, was examined by electron microscopy. Development of the retina occurs in four phases. In phase 1 (stages 21–23), the retinal epithelium consists of uniform columnar cells. In phase 2 (stages 24–29), the epithelial cells are classified into light and dark cells on the basis of the electron‐density of their cytoplasm. The perikarya of the light cells are located in the distal half of the epithelium, each extending proximally (i.e., sclerad) a thin foot, which protruded out of the epithelium through a narrow break in the basal lamina. The nuclei of the dark cells are distributed in the proximal half of the epithelium. Both cell types have a short cilium in the distal end. In phase 3 (stages 30–35), the light and the dark cells morphologically differentiate into receptor and supporting cells, respectively. The distal end of the light (receptor) cell begins to form an apical process, which gives off short irregular microvilli from its lateral surface. Beneath the basal lamina the feet of the receptor cells swell and the nuclei migrate into them through narrow breaks in the basal lamina. Thus, at the end of phase 3, each receptor cell becomes divided into an outer and inner segment. In phase 4 (stages 36–40), the receptor cells complete the specific structure as photoreceptive cells. The microvilli arising from the apical processes increase in length, density, and regularity to be organized into rhabdomes. The lamellated membranes of the myeloid bodies appear first in the outer segment and later increase in number in the inner segment. Morphometric data on the rhabdomeric microvilli in the adult and embryonic retinas are presented.
Selective retinal reinnervation of a surgically created tectal island in goldfish. II. Electron microscopic analysis
Authors: Edwards M. A. , Murray M. 
Published: January 2005

AbstractIn the preceding study (Edwards et al., 1985), we showed that regenerating optic axons reestablish a topographically restricted projection to a caudal tectal island created by surgical removal of a 1‐mm‐wide strip of caudal tectum in goldfish. In the present ultrastructural study, we evaluated the dependence of this axonal outgrowth on the presence of tectal target tissue caudal to the gap. Axon counts in the lesion zone were compared between cases with complete caudal tectal ablation and cases with ablation sparing a caudal tectal island (with and without optic nerve crush). During the postoperative interval of 20–50 days (early period), up to about 1,000 unmyelinated axons with features characteristic of optic axons were present in numerous small subpial bundles in both preparations. In the subsequent interval of 50–110 days (middle period), less than 200 axons were counted caudal to simple half‐tecta, whereas 4,000–14,000 myelinated and unmyelinated axons were present in a few large bundles which crossed the lesion zone of tectal island cases. In this period, optic terminals could be demonstrated in the tectal island using the anterograde horseradish peroxidase method. At 170–300 days after surgery (Late period), bridging bundles contained between 2,000 and 6,000 largely myelinated axons. We conclude that caudal tectal tissue is not necessary for the initial outgrowth of a small number of axons beyond a rostral half‐tectum. The target is essential, however, for the maintenance of these axon fascicles and for the subsequent massive outgrowth of axons to the island. The contributions of glial guidance, diffuse exploratory outgrowth, and target‐produced trophic factors to the formation of an initially exuberant projection to the island are discussed. A process of selective axon collateral withdrawal is proposed to account for the decrease in axon numbers within bridging bundles in the late period and for the late restriction in the retinal origin of the island projection indicated by results in the preceding study (Edwards et al., '85).
Ultrastructural characterization of gonadotropin‐releasing hormone (GnRH)‐producing neurons
Authors: Jennes Lothar , Stumpf Walter E. , Sheedy Mary E. 
Published: January 2005

AbstractBy means of preembedding immunohistochemistry, two types of gonadotropin‐releasing hormone (GnRH) positive neurons in the rat could be identified and characterized in the preoptic region and in the diagonal band: (1) a “smooth” GnRH neuron with relatively even cytoplasmic contours, and (2) a “spiny” GnRH neuron with thorn‐like protrusions of the perikaryon and cell processes. Both cell types contain the same organelles in similar number and distribution, but they differ in the number of synaptic contacts. In general, GnRH cell bodies have a large round or ovoid nucleus, well‐developed rough endoplasmic reticulum arranged in multilayered stacks or as individual cisternae, and several Golgi complexes. Lysosomes are not numerous under the conditions studied. Specializations include kinocilia, nematosomes, and lamellar whorls. Throughout the cytoplasm, scattered dense core vesicles with a diameter of 100 nm and clear vesicles with a diameter of 30–40 nm can be seen with a preferential localization close to the cell membrane. The cell processes of smooth GnRH cells close to the perikaryon appear as extensions of the perikaryal cytoplasm with all organelles except the nucleus. The two neurites originate from the perikaryon as tapering cones over a distance of 200–300 μm, until they reach a diameter of 0.5–3 μm. Cell processes of spiny GnRH cells show bifurcations, protrusions, or invaginations and contain clear and dense core vesicles in their spines. In areas distant from the perikaryon, immunoreactive fibers with a large number of dense core and clear vesicles can occasionally be seen to terminate synaptically or asynaptically on other neurons. The GnRH neurons show postsynaptic specializations at the level of the perikaryon and at cell processes, when apposed by a presynaptic terminal. Such synaptic contacts are seen less frequently on smooth cells than on spiny cells. Large areas of the GnRH cell may be covered by a thin glial lamella, which separates the cell body from the surrounding neuropil. The results indicate the existence of two populations of GnRH cell bodies with different patterns of innervation, which suggest different integrative capacities.
Cobalt injected into the right and left fasciculi retroflexes clarifies the organization of this pathway
Authors: Kemali M. , Làzàr G. 
Published: January 2005

AbstractA cobaltic lysine complex was injected separately into the right and left fasciculi retroflexes of the frog. This tracing technique labeled, in a Golgi‐like manner, the neurons which initiate the fasciculi retroflexes and revealed details of their morphological pattern.The fasciculi retroflexes originate from various neurons distributed in the diencephalon and mesencephalon, but their main source is the habenular nuclei. In the frog there are dorsal and ventral habenulae which are homologous to the medial and lateral habenulae, respectively, of mammals. In the frog the dorsal habenulae are strikingly asymmetric.Our study shows that the fasciculus retroflexus is composed of several compact separated bundles of fibers and that the fibers originating from the dorsal habenular nuclei project to the interpeduncular nucleus, while those originating from the ventral habenular nuclei project beyond the interpeduncular nucleus, but so far we have not been able to show the exact site of their termination.The labeling of cells within the interpeduncular nucleus raises the possibility that the habenulo‐interpeduncular tract is reciprocal in function.The finds support our previously reported hypothesis on the theoretical interpretation of the functional circuitry of the frog habenulo‐interpeduncular system.
A morphological study of glial cells in the hypoglossal nucleus of the cat during nerve regeneration
Authors: Cova John L. , Aldskogius Håkan 
Published: January 2005

AbstractThe cat hypoglossal nerve and nucleus have been used as a model for the study of the occurrence and time course of modifications in the size and composition of the perineuronal glial cell population as they relate to cytological changes in the nerve cell body and the initiation and progress of axon regeneration. Animals were killed at 2, 5, 10, 20, 35, 65, and 115 days after crush injury to the hypoglossal nerve. At 5 days after surgery, growth cones and regenerating unmyelinated axons were present at the lesion site, but no conspicuous changes were apparent in the nerve cell bodies. At 10 days after surgery, the granular endoplasmic reticulum was disaggregated and depleted. The elongation phase appeared to be completed at 20 days, as judged by the bilateral retrograde labeling of the hypoglossal nuclei with horseradish peroxidase. By 35 days, the cytoarchitecture of the nerve cell bodies and maturation of axons, as determined by a comparison of the relative frequency distribution of cross sectional areas proximal and distal to the lesion, were completely restored. Comparative quantitative light microscopic examination of the hypoglossal nuclei of intact and experimental animals failed to reveal any statistically significant differences in the total number of glial cells, number of glial cells/unit area of neuropil, or relative proportions of glial cell types at any of the postoperative time intervals. Moreover, electron microscopic quantitation of the microglial cell population did not reveal any significant alterations in the number, density, location, or morphology of these cells. These results demonstrate that perineuronal glial cell proliferation or changes in the composition of the glial cell population are not attendant on retrograde changes in the cat hypoglossal nucleus or a necessary concomitant to successful axon regeneration.
The distribution of bovine pancreatic polypeptide/FMRFamide‐like immunoreactivity in the ventral nervous system of the locust
Authors: Myers Camilla M. , Evans Peter D. 
Published: January 2005

AbstractThe distribution of bovine pancreatic polypeptide (BPP) FMRFamide‐like immunoreactivity is described in the ganglia of the ventral nerve cord and in the peripheral median nervous system of the locust, Schistocerca gregaria.Immunoreactive cell bodies occur in three regions of the thoracic ganglia: 1) two pairs of cells lie in the anterior of the ganglion ventral to the root of nerve 1 and the anterior ventral association centre; 2) a group of cells lies in the ventral midline at the level at which nerves 3 and 4 leave the ganglion; 3) and two bilaterally symmetrical, posterior lateral groups lie between nerves 5 and 6 at the edge of the ganglion. Immunoreactive cell bodies in the suboesophageal and abdominal ganglia are confined to the midline and are distributed along the anterior‐posterior axis both dorsally and ventrally. The processes of the posterior lateral groups have been traced into the neurohaemal organs of the median nerve and beyond. In the periphery such processes innervate the salivary glands and various muscles.The nature of the endogenous antigen contained in the immunoreactive cells has been investigated with the use of antisera against other peptides of the pancreatic polypeptide family, namely avian pancreatic polypeptide, neuropeptide Y, and peptide YY. In addition, BPP antisera not specific for the C terminal hexapeptide have been tested. Liquid preabsorption experiments with BPP and FMRFamide (the molluscan cardioacceleratory peptide) suggest that the endogenous peptide antigen contained in the stained neurones may belong to the pancreatic polypeptide family or to the FMRFamide family.
An EM‐autoradiographic and EM‐HRP study of the commissural projection of the superior colliculus in the cat
Authors: Behan Mary 
Published: January 2005

AbstractTerminals of the commissural projection in the cat were characterized ultrastructurally by autoradiograhic and horseradish peroxidase methods. The results of the two studies are complementary. Terminals of commissural cells are present in the intermediate and deep layers of the cat superior colliculus. Two distinct populations of terminals are present: one containing mostly round vesicles and forming asymmetric specializations, and a second containing mostly pleomorphic vesicles and forming symmetric specializations. Both populations contact small dendrites or dendritic appendages. The two populations, mostly round and mostly pleomorphic, are present in the ratio of 2:1. Terminals measure approximately 1.1 μm in mean diameter and contact profiles ranging in size from 0.2 to 4.6 μm. There is no significant difference between the two populations in either pre‐ or postsynaptic profile size. The colocalization of terminals of commissural neurons with other afferent and efferent projections of the intermediate layers of the superior colliculus is discussed.
The dendritic architecture of the visual pretectal nuclei of the rat: A study with the Golgi‐cox method
Authors: Gregory Kenneth M. 
Published: January 2005

AbstractThe dendritic architecture of the neurons of the visual pretectal nuclei in the rat was studied with the Golgi‐Cox method. The olivary pretectal nucleus (PO) is characterized by distinctive neurons with a gnarled, tufted, richly branched dendritic arbor forming a dense neuropil within the nucleus. The distinct dendritic morphology of the olivary pretectal neurons enables this nucleus to be identified at all levels of the pretectum in Golgi‐impregnated preparations. Rostromedially, the PO is surrounded by peripheral neurons whose dendrites wrap around the surface of the PO. The nucleus of the optic tract (NTO) contains three types of cells: (1) superficial horizontal cells whose dendrites extend out transversely; (2) large multipolar neurons whose dendrites spread out predominantly in a transverse plane, and (3) small to medium multipolar neurons with varying dendritic architecture. The posterior pretectal nucleus (PP) is composed predominantly of (1) multipolar cells with horizontally and vertically oriented dendrites extending out transverse to the optic axons; (2) piriform cells with dendrites extending dorsally toward the brachium; and (3) small multipolar neurons. The presence of superficial horizontal and large multipolar neurons in the NTO distinguishes the NTO from the PP in Golgi preparations. The horizontally oriented dendrites of many of the multipolar neurons in the PP give this nucleus an appearance distinct from that of the NTO. The differences in dendritic morphology between the visual pretectal nuclei in the rat permit identification of these nuclei at all levels within the pretectum. The boundaries of these nuclei, as determined in the Golgi‐Cox preparations, correlate quite well with the boundaries defined by studying retinal projections (Scalia and Arango, '79).