bluuebunny/crossref_metadata_2025_split huggingface dataset:
Postnatal development of GABA‐ergic neurons in the rabbit retina
Authors: Man‐Kit Lam Dominic , Fung Sek‐Chung , Kong Yun‐Cheung 
Published: January 2005

AbstractUptake, synthesis, storage, and release of γ‐aminobutyric acid (GABA) are some of the characteristic properties of GABA‐ergic neurons. In the present study, we have used these properties as physiological probes to follow the emergence and maturation of GABA‐ergic neurons during postnatal development of the rabbit retina. There is autoradiographic, immunocytochemical, and pharmacological evidence that some amacrine cells and certain neurons in the ganglion cell layer probably use GABA as the neurotransmitter. These neurons take up GABA, contain the GABA‐synthesizing enzyme L‐glutamic acid decarboxylase (GAD, EC 4.1.1.15), and release the accumulated GABA by a Ca++‐dependent mechanism when depolorized with high extracellular K+ concentration. In this study, we show that certain neurons in the newborn retina already possess a specific mechanism for GABA uptake. The positions and numbers of these cells in the developing retina suggest that they will become GABA‐ergic neurons in the adultretina. These putative GABA‐ergic neurons are, however, probably immature an birth because newborn retinas contain only low levels of GABA and GAD. Additionally, there is relatively little K+‐stimulated, Ca++‐dependent release of (3H)‐GABA from the newborn retinas. GABA concentrations and GAD activities in developing retinas increase steadily postnatally, reaching about 80% of the adult levels by day 9. The activities of the GABA‐degrading enzyme, GABA‐glutamate transaminase (GABA‐T, EC 2.6.1.19), follow a similar pattern of maturation during retinal development. K+stimulated GABA release, however, remains low until about day 6, and then increases dramatically from 20% to 85% of the adult level over the next 3 days. Taken together, our results indicate that in the rabbit retina, the commitment by certain neurons to use GABA as the transmitter is made prenatally. These neurons are immature at birth but are biochemically, physiologically, and probably functionally mature by about 9 days after birth.
Retinotopic organization of areas 20 and 21 in the cat
Authors: Tusa R. J. , Palmer L. A. 
Published: January 2005

AbstractThe retinotopic organization of cat cortex, in the vicinity of areas 20 and 21 as defined by Heath and Jones ('71), was determined using electrophysiological mapping techniques. Although the topography of the visual field representations in this region of cortex is more complex than that found in areas 17, 18, and 19, this region appears to contain four representations of the visual hemifield. The four cortical areas these visual field representations occupy have been labeled 20a, 20b, 21a, and 21b. These representations are not as precise as those found in areas 17, 18, and 19; the receptive fields in areas 20a, 20b, 21a, and 21b are larger and there is more scatter in receptive field location among adjacent cells. The upper visual hemifield is emphasized in all four of these areas, but the extent of the representation ranges from just the central 20° found in area 21a to nearly the entire upper visual quadrant found in area 20b. The peak areal magnification factors found in these areas are all at least one order of magnitude less than those found in area 17. The visual field transformations from retina onto cortex in areas 20a, 20b, 21a, and 21b are similar to the types we found in other cortical visual areas, and the significance of these transformations for visual processing is discussed.
Peripheral myelin in the mouse mutant Shiverer
Authors: Rosenbluth J. 
Published: January 2005

AbstractThe mouse mutant Shiverer has been shown previously to lack myelin basic protein and other myelin proteins in both the peripheral and central nervous systems. Examination by electron microscopy shows that the peripheral nervous system, in contrast to the markedly abnormal central nervous system, is grossly normal. Myelin sheaths are of the usual thickness and exhibit normal periodic structure consisting of alternating major dense and intermediate lines. Subtle abnormalities do occur, however, consisting of increased numbers of cytoplasm‐containing lamellae, aberrant terminations of myelin lamellae in internodal regions, invagination of the axon by the inner tongue of the myelin sheath, myelin debrin in both axon and Schwann cells, and disruption of outer myelin lamellae. Such changes have been seen previously in various types of neuropathy and are not pathognomonic of the Shiverer mutation. Despite the absence of myelin basic protein, the peripheral manifestations of this gene are relatively minor and probably not severe enough to compromise peripheral nerve function significantly.
Immunocytochemical localization of enkephalin and substance P in the dorsal tegmental nuclei in human fetal brain
Authors: Pickel Virginia M. , Sumal Khushdev K. , Reis Donald J. , Miller Richard J. , Hervonen Anti 
Published: January 2005

AbstractThe peroxidase‐antiperoxidase (PAP) technique is used to examine the localization of methionine [Met5]‐enkephalin and substance P in the dorsal tegmental nuclei of the human fetal brain. Specific antiserum to both peptides is immunocytochemically detectable in neuronal perikarya and varicose processes in the human dorsal tegmental nuclei at 17–21 weeks of gestation. However the two peptides show a differential distribution in the central versus peripheral portion of the nucleus. Enkephalin‐like immunoreactivity is primarily localized in perikarya along the peripheral borders of the tegmental nuclei, whereas substance P is present primarily in varicose terminals and a few perikarya in the more central portions. These findings suggest that substance P‐containing terminals in dorsal tegmental nuclei are probably derived from afferent axons and that enkephalin is present in intrinsic neurons.
Immunoperoxidase localization of glial fibrillary acidic protein in radial glial cells and astrocytes of the developing rhesus monkey brain
Authors: Levitt Pat , Rakic Pasko 
Published: January 2005

AbstractPeroxidase‐antiperoxidase (PAP) immunohistochemical staining, utilizing a specific antibody to the glial fibrillary acidic protein (GFA), was employed to analyze gliogenesis in the central nervous system of rhesus monkeys ranging in age from embryonic day 38(E38) to birth (E165) and through the second postnatal month. All major subdivisions of the brain contain glial cells, recognized by the presence of dark brown horseradish peroxidase (HRP) reaction product. Neuronal elements are not stained with this immunocytochemical technique.The first class of glial cell to appear during development are the radial glial cells; the radial glial fibers fan out from the ventricular and subventricular zones, where their cell bodies reside, to the pial surface where they terminate with conical endfeet. These glial cells appear within the first third of gestation, being present in the spinal cord and brainstem by E41; in the diencephalon by E45; and in the telencephalon and cerebellum by E47. The next class of glia to appear is the Bergmann glial cell of the cerebellar cortex, which can be stained by E54. Bergmann glial cells located below the Purkinje cell layer issue parallel processes which extend up to the pial surface. Within each major subdivision of the brain, massive numbers of elongated glial fibers continually alter their distinctive patterns to maintain constant ventricular‐pial surface relationships during the major tectogenetic changes which occur throughout embryonic development. In Nissl‐counterstained sections columns of migrating neurons are observed juxtaposed to GFA‐positive radial and Bergmann glial fibers.Radial glial cells assume a variety of transitional forms during the process of their transformation into mature astrocytes. This transformation occurs in each structure at specific embryonic ages and is initiated after neuronal migration has begun to subside. The number of astroglial cells increases at an accelerated pace after neurogenesis is complete.The immunohistochemical localization of radial glial fibers at relatively early stages of embryonic development indicates that glial cells are present concomitantly with neurons, raising the possibility that at least two distinct populations of cell precursors compose the proliferative zones. Furthermore, the demonstration of large numbers of radial glial cells in all brain regions during the peak of neuronal migration and a close structural relationship between elongated glial fibers and migrating neurons support the concept that glia play a significant role in the guidance and compartmentalization of neuronal elements during development.
Simultaneous monoamine histofluorescence and neuropeptide immunocytochemistry: II. Correlative distribution of catecholamine varicosities and magnocellular neurosecretory neurons in the rat supraoptic and paraventricular nuclei
Authors: Mc Neill Thomas H. , Sladek John R. 
Published: January 2005

AbstractThe comparative morphology of catecholamine (CA) varicosities and neurophysin (NP)‐containing perikarya of the supraoptic (SON) and paraventricular nuclei (PVN) was examined. The major CA innervation to the SON and PVN did not coexist with the major distribution of magnocellular perikarya, but was located peripheral to the nuclei. A dense distribution of CA varicosities was found ventral to the neurosecretory perikarya of the SON and overlapped numerous immunoreactive oxytocin‐ and vasopressin‐containing neuritic profiles. Examination of Golgi‐stained sections revealed that dendrites from SON perikarya projected to the CA zone and were likely candidates for the processes identified immunocytochemically. In addition, a heterogenous distribution of axosomatic contacts was found within the SON which suggested a preferential innervation of VP‐containing neurons. The densest concentration of CA varicosities in the PVN occurred in the periventricular region adjacent to the third ventricle and in the contiguous parvocellular portion of the PVN. These CA varicosities overlapped scattered oxytocinerigic perikarya in both areas. In addition the ventromedial as well as the dorsolateral subnuclei of the PVN were contacted by CA varicosities; this heterogeneous distribution suggests that the each subnucleus of the PVN with its individual hypothalamic, neurohypophyseal, brainstem, or cortical projections may possibly receive a catecholaminergic innervation by a select group of CA cells or nuclear groups from the brain stem.
Accelerated rates of synaptogenesis by “sprouting” afferents in the immature hippocampal formation
Authors: Gall Christine , McWilliams Randall , Lynch Gary 
Published: January 2005

AbstractLight and electron microscopic methods were used to study the rate with which undamaged afferents sprout into and form synapses within denervated dendritic zones in the immature rat brain. The middle and outer molecular layers of the dentate gyrus were deafferented by ablation of the ipsilateral entorhinal cortex in 14‐day‐old rats, and the extension of the commissural projections, which are normally restricted to the inner molecular layer, into the denervated territory was studied by light microscopic autoradiographic tracing methods. Collateral growth was noted as early as 13 hours after the lesion and was found to reach throughout the middle and outer molecular layers by 48 hours postlesion. Quantitative analyses (grain counts) revealed that the addition of commissural fibers and terminals to the denervated zones proceeded extremely rapidly up to 72 hours after the removal of the entorhinal cortex, but slowed markedly thereafter. Electron microscopic procedures were used to assess the rate at which synapses formed during this period and yielded the following information: 1) The density of intact synapses fell to below 20% of normal values within 20 hours of the lesion, 2) reinnervation began before 30 hours postlesion, and 3) the rate at which synapses were added to deafferented middle molecular layer was much more rapid from 20–96 hours postlesion than is observed in this zone during normal development. Furthermore, the sprouting of the inner molecular layer afferents into the middle molecular layer did not retard the pace of synaptogenesis in their normal target region. These results suggest that intrinsic limitations in the capacity of axons and dendrites are not responsible for determining the rate of synaptogenesis in the developing hippocampus. It is proposed instead that existing synapses (or terminals and spines) tend to suppress the formation of new contacts such that the local density of connections regulates the speed with which further innervation occurs.
2‐deoxyglucose uptake in the cat spinal cord during sustained and habituated activity in the plantar cushion reflex pathway
Authors: Proshansky Eric , Kauer John S. , Stewart William B. , David Egger M. 
Published: January 2005

Abstract[14C]2‐deoxy‐D‐glucose (2‐DG) was administered intravenously to anesthetized cats during electrical stimulation of the plantar cushion (central foot pad). Afferent volleys and the efferent reflex were monitored by recording from the tibial nerve at the ankle. Plantar cushion stimulation at 3 HZ, 5 × threshold for 45 minutes led to a discrete region of increased 2‐DG uptake dorsomedially in the dorsal horn, predominantly in Rexed's laminae III and IV, ipsilateral to the stimulation. A less marked increase in labeling was also sometimes observed in the medial portion of lamina V. No labeling specific to stimulation was observed in the ventral horns. A control preparation, to determine the effects of surgical manipulations alone, confirmed that the labeling was indeed specific to the plantar cushion stimulation.A pattern of labeling identical to that seen during 3 Hz, 5 × threshold stimulation occurred when 2‐DG was administered during 10 Hz, 5 × threshold stimulation, after the reflex elicited by plantar cushion stimulation had completely habituated.The most straightforward interpretation of our results suggests that the increases in 2‐DG labeling produced by stimulation of the plantar cushion probably occurred in regions with heavy concentrations of axon collaterals of the primary afferent Aαβ fibers from the plantar cushion, at or near their sites of termination in the dorsal horn.
Early development of the inferior olivary complex in pouch young opossums. II. An electron microscopic study
Authors: Maley Bruce E. , King James S. 
Published: January 2005

AbstractAt birth the inferior olivary complex (IOC) is not present in the caudal ventro‐medial brainstem of the opossum. In the 3‐‐7‐day‐old animal (15–19 days post‐conception), this same region does contain neurons of the developing IOC. The immature neurons are characterized by large, centrally numerous small‐diameter profiles which contain bundles of filaments and scattered microtubules. Occasional synaptic endings, containing round clear vesicles, contact large, flocculent profiles which contain bundles of filaments and scattered microtubules. Occasional synaptic endings, containing round clear vesicles, contact large, flocculent profiles. By 10–14 days of age, the olivary cell bodies and the surrounding neuropil exhibit many of the same features as in the 3–7 day‐old opossums. In opossums 21–25 days old, there is an increase in varicosities and irregular contours along many of the dendritic shafts. Furthermore, synaptic terminals, possessing round clear vesicles, now contact the soma, dendritic shafts, dendritic varicosities, spines, and large, flocculent profiles. Terminals containing pleomorphic vesicles or a mixture of clear and large granular vesicles are presynaptic only to dendritic spines or large, flocculent profiles. Neuroglial cell bodies have been identified at all ages examined.It is not until days 65–68 that pre‐ and postsynaptic elements are organized into synaptic clusters (glomeruli), which are typical of the adult. Spiny appendages and small‐diameter dendrites comprise the central core of the clusters which are surrounded by synaptic endings containing a variety of vesicle types. Thus it would appear that subsequent to their initial arrival (day 16–17), the synaptic relationships of cerebellar and midbrain afferents are modified to reflect their adult configuration by days 65–68. This extended period of development (postnatal days 3–68) for the olivary complex provides a good model for assessing the effects of experimental manipulations.
The ontogeny of the distribution of callosal projection neurons in the rat parietal cortex
Authors: Ivy Gwen O. , Killackey Herbert P. 
Published: January 2005

AbstractThe ontogeny of callosal projection neurons in the rat parietal cortex was examined using the retrograde and anterograde transport of horseradish peroxidase (HRP), as well as Golgi and Nissl stains. From postnatal day 0 (PND 0) to early PND 4, the callosal projection neurons are distributed as two continuous horizontal bands of cells which extend throughout the subplate in layers Va and Vc‐upper VIa. Neurons within the cortical plate (CP), however, do not transport HRP from a contralateral injection site until PND 3 to early PND 4, when a few cells at the lower CP border are generally labeled. However, by late on PND 4, and more consistently by PND 5, several changes in the distribution of callosal projection neurons take place. First, cells at all levels of the CP become labeled in a sequential fashion, from the lower border upward. Second, gaps, or areas devoid of HRP, become apparent in layer IV of the barrel field area. Third, in the cortical areas containing the gaps, as well as in other areas which are destined not to be callosally connected in the adult, there is a noticeable decrease in the number of cells labeled with HRP. This decrease continues through PND 15 and possibly into adulthood. The foregoing developmental events are compared to cortical maturation as seen in both Golgi‐ and Nissl‐stained material. By PND 15, the basic adult pattern of callosal projection neurons is established. The neurons reside mainly in layers III and Va, with fewer in layers II and Vc‐upper VIa, and fewer still in the other cortical layers. They are aligned in vertical arrays in discrete areas of the cortex.
The emergence, localization, and maturation of neurotransmitter systems during development of the retina in xenopus laevis: II. Glycine
Authors: Rayborn Mary E. , Sarthy P. Vijay , Lam Dominic M. K. , Hollyfield Joe G. 
Published: January 2005

AbstractThe high‐affinity uptake and release of glycine was studied in retinas of Xenopus laevis. In the toad and tadpole retina, 3H‐glycine was accumulated by a population of cells located predominantly in the inner nuclear layer. When retinas preloaded with 3H‐glycine were subjected to high K+‐concentrations, these retinas released large amounts of 3H‐glycine by a Ca++‐dependent mechanism. The appearance and maturation of these putative glycinergic properties was followed during retinal development. Our results indicate that the high‐affinity uptake of glycine first appears around stage 33/34 whereas K+‐stimulated glycine release cannot be detected until stage 42.
Efferent vestibular neurons: A study employing retrograde tracer methods in the pigeon (Columba livia)
Authors: Schwarz Irmgard E. , Schwarz Dietrich W. F. , Fredrickson John M. , Landolt Jack P. 
Published: January 2005

AbstractEfferent neurons innervating the vestibular labyrinth and cochlea of the pigeon have been identified by means of a variety of retrograde tracers: [3H]‐adenosine (Ad), horseradish peroxidase (HRP), Evan's Blue (EB) and Bisbenzimide (Bb). Discrete injections into individual cristae ampullares of the semicircular canals, into the macula utriculi, or into several of these end organs resulted in similar patterns of neuronal labelling. Efferent vestibular neurons were always found within a small portion of the nucleus reticularis pontis caudalis (RP), ventrolateral to the abducens nucleus on both sides. No systemic difference in the locations of labelled cells was found following injection into different sensory epithelia. Cell counts following injections into individual cristae did not differ significantly from those following injections into all three cristae. The injections into all cristae in both labyrinths yielded cell counts that were much lower than twice the number of cells labelled by injections into the three cristae on one side only. When HRP was injected into the right lateral canal crista and Ad into the right posterior canal crista, a high proportion of neurons was labelled with both compounds (61% of the HRP‐labelled cells and 67% of the Ad‐labelled cells). Injection of EB into all three cristae on the right side and Bb into all three cristae on the left side produced a smaller percentage of doubly labelled cells (10% of the EB‐labelled cells and 6% of the Bb‐labelled cells). It is concluded, therefore, that there is a considerable degree of collateralization within one labyrinth. Fewer collaterals of efferent neurons are directed to both labyrinths. Since each semicircular canal represents head rotation in one direction and one plane, it is unlikely that efferents which contact several different movement sensors can provide sensory motor control that is specific for directions and planes of head movements.Control injections of these tracers into the cochlea yielded labelled cells in a different reticular structure, the nucleus reticularis paragigantocellularis lateralis (Pgc), on both sides, as well as in the RP. It is proposed that the Pgc cells represent cochlear efferents, while the RP neurons are related to the macula lagenae, an otolithic organ of balance in the pigeon.