bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic organization of globular bushy cells in the ventral cochlear nucleus of the cat: A quantitative study
Authors: Ostapoff E.‐Michael , Morest D. Kent 
Published: January 2005

AbstractThe synaptic organization of globular bushy cells of the anteroventral cochlear nucleus was quantitatively analyzed in order to understand better their functional attributes. A method was devised to estimate the concentrations and relative proportions of synapses on the entire postsynaptic surface of Golgi‐impregnated neurons, by sampling with limited series of sections for electron microscopy. This provided a characteristic synaptic profile which was homogeneous for the population measured.The total concentration of synaptic endings decreases with distance from the soma. The cochlear, presumably glutamatergic and excitatory, endings with large spherical vesicles (LS) account for most of this decrease. Of the noncochlear inputs, the putative glycinergic endings with flattened vesicles (FL) decrease slightly, and the presumed GABAergic terminals with pleomorphic vesicles (PL) maintain a relatively constant concentration, while endings with small spherical vesicles (SS) increase on the distal dendrites. LS endings have the largest proportion of synapses near the soma, while FL synapses maintain a constant proportion in all cell regions, and PL and SS proportions increase on higher‐order dendrites. Excitatory and inhibitory synapses have significant inputs to the axon hillock and initial segment, as well as to the distal dendrites, where dual synapses may provide a way to sample the activity of surrounding neurons.These features must be considered in explanations of physiological properties, such as the synaptic security, level of spontaneous activity, and well‐timed, rapid onset responses, as well as their potential for normalizing and synchronizing an important inhibitory pathway involved in binaural signal processing. Synaptic profile analysis should be useful for experimental studies and for developing realistic computational models.
Hair cell differentiation in the developing chick cochlea and in embryonic Cochlear organ culture
Authors: Stone Jennifer S. , Cotanche Douglas A. 
Published: January 2005

AbstractWe have defined a method for growing chick embryonic cochleae in organ culture that preserves many aspects of hair cell differentiation. Cochlear ducts were isolated from embryonic day 8 chicks, placed in organ culture, and incubated for 48 hours (to a point equivalent to embryonic day 10). The cultured ducts were then fixed and processed for scanning electron microscopy. As controls, cochlear ducts at embryonic days 8 and 10 were dissected and immediately fixed and processed for scanning electron microscopy. We chose this period to culture cochleae because at the corresponding time in vivo hair cells undergo a dynamic phase of differentation. During this time, the number of stereocilia in the stereociliary bundle increases, and two to three rows of stereocilia nearest the kinocilium elongate, initiating the staircase pattern of the bundle. Also, the orientation of many hair cells shifts from nonpolarized at embryonic day 8 to polarized toward the inferior edge cf the basilar papilla at embryonic day 10. Many of these aspects of hair cell differentiation proceed normally in organ culture. The appropriate distal‐to‐proximal gradients of hair cell density, apical surface area, and stereociliary number are preserved. Elongation of the 1–2 stereociliary rows next to the kinocilium continues, and more stereociliary bundles are oriented toward the inferior edge in cultured cochleae than in embryonic day 8 chicks. It appears that cochlear organ culture can serve as an effective method with which to study how hair cell differentation is regulated.
Classification of the principal cells of the medial nucleus of the trapezoid body
Authors: Kuwabara N. , Zook J. M. 
Published: January 2005

AbstractCells in the medial nucleus of the trapezoid body were intracellularly labeled in brainstem tissue slices of two bat and two rodent species. The main cell type found in this nucleus, the principal cell, is an important link in the relay of ascending projections from the contralateral cochlear nucleus to the lateral superior olive, completing an essential pathway for sound localization. Principal cells are often viewed as a highly homogeneous group with a consistent morphology as well as a common function.Intracellular labeling has revealed a number of new axonal and dendritic features of principal cells. Some of these features vary widely from cell to cell, suggesting that the population of principal cells contains several morphologically distinct subgroups. Similar subsets of principal cells were recognized in all species examined.Five subgroups were distinguished on the basis of the position of dendritic fields. Although the dendrites of most labeled cells were confined to the medial nucleus of the trapezoid body, some principal cells had dendrites that spread outside the nucleus to one of several adjacent periolivary cell groups. Cells were also found that had dendrites that spread medially across the midline and into the contralateral medial nucleus of the trapezoid body.Axonal projections were used to distinguish two additional subgroups of principal cells. All principal cells project to the lateral superior olive and virtually all have one or more secondary projections. There are two subgroups with unusual collateral projections: one with collaterals that extended to the lateral lemniscus and one with recurrent collateral axons.
Glial cells of the parietal eye: Structural and biochemical similarities to retinal Müller cells
Authors: Engbretson Gustav A. , Linser Paul J. 
Published: January 2005

AbstractThe parietal eye of lizards is a relatively simple yet highly structured visual organ. Cone‐like photoreceptors synapse directly onto ganglion cells that project to the brain. Golgi staining confirmed the existence of glial cells spanning the sensory epithelium in a manner analogous to the Müller cells of the vertebrate lateral eye retina. These parietal eye glial cells bear expanded end feet at the basal border of the eye. Electron microscopic examination revealed some ultrastructural similarity to Müller cells. Mitochondria, osmiophilic and transparent vesicles, and the Golgi apparatus are found in the apical end of the parietal eye glial cell. Junctional complexes join adjacent parietal eye glial cells and their neighboring photoreceptor cells. Bundles of filaments are found in the basal end of the cell and the plasma membranes of adjacent cells often intertwine tightly in this region. The parietal eye glial cells are immunoreactive to antibodies against glutamine synthetase, also characteristic of Müller cells. Some differences between parietal eye glial cells and Müller cells also are evident. The parietal eye glial cells are not immunoreactive to antibodies against another Müller cell marker, carbonic anhydrase II, and many of them contain melanin granules, while Müller cells are not pigmented. In addition, we have found that the lens cells of the parietal eye and the Müller cells of the lateral eye retina of lizards are immunoreactive to antibodies against both glutamine synthetase and carbonic anhydrase II.
Organization of medullary adrenergic and noradrenergic projections to the periaqueductal gray matter in the rat
Authors: Herbert Horst , Saper Clifford B. 
Published: January 2005

AbstractThe periaqueductal or midbrain central gray matter (CG) in the rat contains a dense network of adrenergic and noradrenergic fibers. We examined the origin of this innervation by using retrograde and anterograde axonal tracers combined with immunohistochemistry for the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine β‐hydroxylase (DBH), and phenylethanolamine N‐methyltransferase (PNMT). Following injections of the fluorescent tracers Fast Blue or Fluorogold into the CG, double‐labeled neurons in the medulla were identified mainly in the noradrenergic A1 group in the caudal ventrolateral medulla (VLM) and A2 group in the medial part of the nucleus of the solitary tract (NTS); and in the adrenergic C1 group in the rostral ventrolateral medulla and C3 group in the rostral dorsomedial medulla. Injections of Phaseolus vulgaris‐leucoagglutinin (PHA‐L) into these cell groups resulted in a distinct pattern of axonal labeling in various subdivisions of the CG. Anterogradely labeled fibers originating in the medial NTS were predominantly found in the lateral portion of the dorsal raphe nucleus and in the adjacent part of the lateroventral CG (CGlv). Following PHA‐L injections into the C3 region the anterogradely labeled fibers were diffusely distributed in the CGlv and the dorsal raphe nucleus at caudal levels, but rostrally tended to be located laterally in the CGlv. In contrast, ascending fibers from the caudal and rostral VLM terminated in the rostral dorsal part of the CGlv and in the dorsal nucleus of the CG, whereas ventral parts of the CG, including the dorsal raphe nucleus, contained few afferent fibers. Double‐label studies with antisera against DBH and PNMT confirmed that noradrenergic neurons in the A1 and A2 groups and adrenergic neurons in the C1 and C3 groups contributed to these innervation patterns in the CGlv. Noradrenergic and adrenergic projections from the medulla to the CG may play an important role in a variety of autonomic, sensory and behavioral processes.
Development of glutamic acid decarboxylase‐immunoreactive elements in the cerebellar cortex of normal and lurcher mutant mice
Authors: Heckroth John A. 
Published: January 2005

AbstractThe development of glutamic acid decarboxylase‐immunoreactivity (GAD‐IR) in cells, fibers, and varicosities of the cerebellar cortex has been examined by light microscopy in normal and lurcher mutant mice between postnatal day 3 and 30 (P3–P30). Purkinje cell morphology was demonstrated in adjacent sections by using an antiserum to the 28Kd vitamin D‐dependent calcium binding protein (CaBP). In early postnatal lurcher mice, but not in normal littermates, GAD‐IR fibers, presumably Purkinje cell pseudopodia, invade the external granular layer. The plexus of CaBP‐IR axons in the internal granular layer is much less complex in lurcher mice than in normal littermates, even before the onset of lurcher Purkinje cell degeneration at P8. In normal mice, GAD‐IR fibers encapsulate Purkinje cell somata by P15. Lurcher Purkinje cells, in contrast, receive scattered contacts by GAD‐IR puncta and possess a “cap” of such elements surrounding the primary dendrite and apical soma. Pinceau formations, visible as a knot of GAD‐IR puncta hanging from the base of Purkinje cells in normal P15 mice, are not present in lurcher littermates. “Empty baskets” or collapsed pinceau formations in regions devoid of Purkinje cells are not revealed by anti‐GAD immunohistochemistry in the P17–P30 lurcher cerebellar cortex.
Intrinsic circuitry in the cat superior colliculus: Projections from the superficial layers
Authors: Behan M. , Appell P. P. 
Published: January 2005

AbstractThe neuroanatomical tracer Phaseolus vulgaris leucoagglutinin (PHA‐L) was used to label the local projections of neurons whose cell bodies are located in the superficial layers of the cat superior colliculus. Small, localized groups of neurons in the superficial layers project to all regions of the ipsilateral colliculus, including the deep layers. Comparable distributions of labeled terminals are seen throughout the colliculus when the PHA‐L injection site is located in the rostral, middle, or caudal one‐third of the colliculus. In addition, there is some evidence of a topographic projection from superficial to deep layers. These results suggest that a complex anatomical substrate exists for communication between the superficial and deep layers of the colliculus. Connections such as these may underlie the transfer of visual information from neurons in the superficial layers to populations of neurons in the deep layers that respond prior to saccadic eye movements.
Development of the olfactory nerve in the clawed frog, Xenopus laevis: II. Effects of hypothyroidism
Authors: Burd Gail D. 
Published: January 2005

AbstractQuantitative and morphological data were obtained on developing olfactory axons in normal and hypothyroid larvae of the African clawed frog Xenopus laevis. Hypothyroid larvae were produced by rearing the animals, beginning at stage 48, in a 0.01% solution of propylthiouracil (PTU), a treatment that blocks synthesis of thyroid hormone. These PTU‐treated larvae were compared to their age‐matched siblings when these siblings reached stage 52 (premetamorphic larvae; prior to synthesis of thyroid hormone), stage 57 (late prometamorphic larvae; after the onset of thyroid hormone synthesis), or stage 58 (larvae at the onset of metamorphic climax; thyroid hormone levels continue to rise). The number of olfactory axons did not differ between stage 52 control animals and the age‐matched, PTU‐treated animals, but there were only about half the number of axons in the PTU‐treated animals that were age‐matched to the stage 57 or 58 controls. Thus, PTU had no effect on olfactory axon number prior to the normal rise in thyroid hormone levels. But PTU significantly reduced the normal increase in olfactory axon number compared to stage 58 control larvae, whose thyroid hormone levels are high. While PTU also produced some changes in several other body measurements, the effect on the olfactory axons was the most consistent and prominent. The results presented here support our previous findings that thyroid hormone plays a significant role in the development of the olfactory system in Xenopus.
Functional and anatomical organization of cardiovascular pressor and depressor sites in the lateral hypothalamic area: I. descending projections
Authors: Allen Gary V. , Cechetto David F. 
Published: January 2005

AbstractThe present study describes the anatomical organization of projections from functionally defined cell groups of the lateral hypothalamic area. Cardiovascular pressor and depressor sites were identified following microinjection (5–50 nl) of 0.01–1.0 M L‐glutamate or D, L‐homocysteate into the anesthetized rat. Subsequent injections of Phaseolus vulgaris‐leucoagglutinin (PHA‐L) or wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) were made into pressor or depressor sites and their connections with the brainstem and spinal cord were traced.Decreases in blood pressure (10–45 mmHg) and heart rate (20–70 bpm) were elicited from tuberal (LHAt) and posterior (LHAp) regions of the lateral hypothalamic area (LHA). Depressor neurons in the LHAt have descending projections to the central gray, dorsal and median raphe nuclei, pedunculopontine tegmental nucleus, pontine reticular formation, medial and lateral parabrachial nuclei, laterodorsal tegmental region, and medullary reticular formation including the region of the lateral tegmental field, nucleus ambiguus, and rostrocaudal ventral lateral medulla. In contrast, descending projections from depressor neurons in the LHAp have dense terminal fields in the rostral, middle, and commissural portions of the nucleus of the solitary tract and the lateral tegmental field as well as the ventrolateral central gray, pedunculopontine tegmental nucleus, and medial and lateral parabrachial nuclei. Both the LHAt and LHAp have light projections to the intermediate region of the cervical and thoracic spinal cord.Increases in blood pressure (10–40 mmHg) and heart rate (20–70 bpm) were elicited almost exclusively from neurons located medial to the LHAt and LHAp in a region surrounding the fornix, termed the perifornical area (PFA). Pressor cells in the PFA have descending projections to the central gray, dorsal and median raphe nuclei, laterodorsal tegmental nucleus, and Barrington's nucleus as well as a light projection to the commissural portion of the nucleus of the solitary tract and the intermediate region of the cervical and thoracic spinal cord. The retrograde labeling observed in the WGA‐HRP studies indicates that cells in most terminal fields have reciprocal projections to the pressor and depressor regions of the LHA. The results demonstrate that groups of neurons in the lateral hypothalamus with specific cardiovascular function have differential projections to the brain stem.
Converging GABA‐ and glutamate‐immunoreactive axons make synaptic contact with identified hypothalamic neurosecretory neurons
Authors: Decavel Chantal , van den Pol Anthony N. 
Published: January 2005

AbstractTo study the neurochemical identity of axons in synaptic contact with identified hypothalamic neurosecretory neurons in rats, we combined retrograde axonal transport of a marker molecule with postembedding immunogold staining for ammo acid neurotransmitters. After intravenous injections of horseradish peroxidase, neurosecretory neurons with axons in the median eminence or neurohypophysis transported the peroxidase retrogradely back to the cell body of origin. Serial ultrathin sections from the paraventricular and arcuate nuclei were immunostained with glutamate or GABA antisera. Peroxidase‐labeled neurons and their dendrites received synaptic contact from colloidal gold‐labeled axons immunoreactive for GABA or for glutamate. Axons which were highly immunoreactive for GABA and other axons immunoreactive for glutamate but not for GABA consistently made converging synaptic contact with the same peroxidase‐labeled cell. Some of the peroxidase‐labeled neurons from the arcuate nucleus which were postsynaptic to both GABA and glutamate axons were themselves identified as being GABA immunoreactive. Serial ultrathin sections revealed that multiple presynaptic axons immunoreactive for glutamate or GABA made repeated contacts with single neurons. These results suggest a widespread convergence of the major inhibitory and excitatory amino acid transmitter on the neurons which control both the anterior and posterior pituitary hormones.
Localization of corticotropin‐releasing factor‐like immunoreactivity in monkey olfactory bulb and secondary olfactory areas
Authors: Bassett J. L. , Shipley M. T. , Foote S. L. 
Published: January 2005

AbstractElectrophysiological and anatomical observations suggest that terminals of olfactory bulb mitral cells ending in rat primary olfactory cortex exert certain postsynaptic effects via an excitatory amino acid neurotransmitter. Recent anatomical studies have shown that several peptides, most notably corticotropin‐releasing factor (CRF) (Imaki et al., '89) (Brain Res., 496:35–44), are also localized within rat olfactory bulb projection neurons, thus raising the possibility that there is a peptide cotransmitter in this system. In contrast to the availability of data for rodents, very little is known about the distribution of peptides and other putative transmitters in the olfactory systems of primate species. In the present study, sections through the olfactory bulb and its target areas were obtained from two monkey species (Saimiri sciureus and Macaca fascicularis) and processed for immunohistochemistry with a well‐characterized polyclonal antiserum directed against the human form of CRF. Virtually identical results were obtained in the two species. Within the olfactory bulb, nearly all mitral and many tufted cells contained CRF‐like immunoreactivity. CRF‐positive fibers were seen within the olfactory tract and olfactory stria, which contain the axons of mitral and tufted cells. Within the anterior olfactory nucleus and layer Ia of the olfactory tubercle and piriform cortex, immunoreactivity was seen within fine processes, as well as in coarse, varicose fibers and isolated puncta. CRF‐positive cells were seen within layer III of the olfactory tubercle and piriform cortex. Immunoreactive fibers and varicosities were also seen within olfactory‐recipient regions of the amygdala and entorhinal cortex. These observations suggest that CRF may act as a transmitter and/or neuromodulator in primate olfactory system.
Age‐related changes in capsaicin‐induced degeneration in rat brain
Authors: Ritter Sue , Dinh Thu T. 
Published: January 2005

AbstractPrevious results indicate that the pattern of capsaicin‐induced degeneration in the rat central nervous system is age‐related. Experiments utilizing capsaicin's selective neurodegenerative effects to study the function of central neural circuits will therefore require a detailed understanding of capsaicin's central neurotoxicity in rats of different ages. The goal of this experiment was to characterize the degeneration induced in the rat brain by systemic treatment with capsaicin at different ages (10, 15, 20, 25, 30 or 75 days, or 11 months), using a cupric silver stain to label degenerating neurons. Results revealed degenerating cell bodies in the ventromedial brainstem in capsaicin‐treated rats of all age groups, though they were more numerous in adult rats than in pups. In addition, many areas contained capsaicin‐induced nerve terminal degeneration both in rat pups and in adult rats. These areas were the substantia gelatinosa of the spinal cord dorsal horn; the solitary tract; the nucleus of the solitary tract, visceral portion; the area postrema; the trigeminal nerve and spinal trigeminal nucleus; the medial nucleus of the inferior olive; the rostral, dorsomedial and dorsolateral interpeduncular subnuclei and overlying interfascicular nucleus; the supramammillary area; the lateral septal nucleus; the bed nucleus of the stria terminalis, anterior medial portion; the optic nerve and tract; the suprachiasmatic nucleus, ventroposterolateral portion; the magnocellular subnucleus of the ventrolateral geniculate nucleus; the intergeniculate leaf; the medial pretectal nucleus and the olivary pretectal nucleus. In several, but not all of these areas, the apparent density of degenerating terminals was significantly less in adult rats than in pups. In other brain sites, capsaicin‐induced degeneration was observed only in rats younger than 30 days of age. These areas were the lateral habenula, medial part; the sphenoid nucleus; and the stria medullaris. Still other brain sites lost their sensitivity to capsaicin sometime between 30 and 75 days of age. These areas were the bed nucleus of the stria terminalis, medial posteromedial part; the medial preoptic nucleus, central part; the septohypothalamic nucleus; the ventral reuniens area; and the ventromedial hypothalamic nucleus. Adult rats 75 days and 11 months of age did not differ detectably in their response to capsaicin. Thus, loss or attenuation of capsaicin sensitivity is not progressive; throughout life. It does not occur in all capsaicin‐sensitive sites. Where it does occur, loss of sensitivity occurs prior to adulthood and follows a distinct and reproducible time course that may differ for different sites.