bluuebunny/crossref_metadata_2025_split huggingface dataset:
The retinal origins of the optic nerve conduction latency groups in the brush‐tailed possum, Trichosurus vulpecula
Authors: Freeman Brian 
Published: January 2005

AbstractThe antidromic compound action potential recorded near the centre of the possum optic disc, following stimulation of the optic chiasm, has four negative peaks corresponding to the optic nerve conduction latency groups t1, t2, t3 and t4. The t2 peak is reduced in the compound action potential recorded from the nasal margin of the optic disc but is prominent on the opposite side at the superior temporal margin. The t4 peak may be absent in this vicinity.The frequency distributions of the diameters of intraretinal ganglion cell axons at the nasal margin and at the superior temporal margin of the optic disc are bimodal. Neither of these size distributions can be directly correlated with the multipeaked antidromic compound action potentials recorded at these same sites. However, by considering the frequency distribution difference between these sites, it is possible to infer (i) that the optic nerve t2 group may be represented intraretinally on the temporal side by a population of medium sized axons with a modal diameter of 0.8 μm and (ii) that the t4 group may be represented intraretinally on the nasal side by a population of small axons with modal diameter 0.3 μm.In addition, a correlation of axon sizes with previously reported regional variations in the sizes of ganglion cell somas suggests that the optic nerve t4 conduction latency group may arise from small ganglion cells in the nasal streak and nasal peripheral retina and that the t2 group may arise from medium sized cells in the temporal area centralis.
Growth pattern of axons in the optic nerve of chick during myelogenesis
Authors: Arees Edward A. 
Published: January 2005

AbstractThe purpose of this experiment was to study the diameter of axons at the time of the initiation of myelin and the pattern of growth of axons in the optic nerve of the chick. Embryos between 15 and 20 days and chicks 3, 5, 22 and 60 days of age were studied on the electron microscopic level.Based on axon diameter a unimodal distribution of unmyelinated axons is present through day 20 of incubation with a mean of approximately 0.35 μ. This population is represented through 22 days of age but from day 3 on, a second distinct population of unmyelinated axons is present which has a mean diameter that is approximately twice that of the smaller unmyelinated axons. All axons do not increase simultaneously in diameter but once growth starts, the unmyelinated axons apparently double in diameter at a relatively rapid rate prior to myelination.On incubation day 17 less than 1% of the axons in the optic nerve is myelinated. The number of axons in this group and their diameter (mean approximately 1.2 μ) remain relatively constant through day 3 but from days 5 through 22, two distinct populations of myelinated axons are present with mean diameters of 0.51 μ, 1.76 μ, and 3.90 μ. These populations represent approximately 20%, 67%, and 13% respectively of the total fiber population.As age increases the diameter of some myelinated axons is as small as or smaller than the unmyelinated axons at an earlier period in development. This suggests that factors other than axon diameter might be involved in the start of myelination. It appears that the increase in axon diameter does not occur in a continuous manner but in a saltatory manner from one size to another.
Synaptic organization of the dopaminergic neurons in the rabbit retina
Authors: Dowling John E. , Ehinger Berndt 
Published: January 2005

AbstractA number of substances were tested for their ability to label amine‐accumulating neurons in the rabbit retina after fixation with OsO4 or glutaraldehyde and OsO4. Useful results were obtained with 5,6‐dihydroxytryptamine (5,6‐DHT) and 6‐hydroxydopamine (6‐HDA). Labelled processes were characterized by small (40–50 mm) pleomorphic synaptic vesicles containing electron‐dense cores, and at times by swelling of mitochondria and by increased electron density of membranes and cytoplasm. Fluorescence microscopy showed that 5,6‐DHT labelled both dopaminergic and indoleamine‐accumulating neurons. In most experiments, therefore, the indoleamine‐accumulating neurons were removed with 5,7‐dihydroxytryptamine. In such retinas the dopaminergic processes labelled by 5,6‐DHT were found to make synapses of the conventional type, characterized by an accumulation of synaptic vesicles on the presumed presynaptic side and some aggregation of material on the cytoplasmic side of the synaptic membranes and within the synaptic cleft. The dopaminergic processes were found to contact each other and also non‐dopaminergic amacrine cells and their processes. Conventional synapses onto dopaminergic processes were observed from both labelled and unlabelled amacrine processes. The input from labelled neurons was observed on varicose dopaminergic processes whereas input from non‐labelled elements was found on the intervaricose parts of the dopaminergic processes. No Contacts of dopaminergic processes with bipolar or ganglion cells were observed. Injections of 6‐HDA gave the same results, although this drug gave less distinct labelling which made the observations less decisive than with 5,6‐DHT. In retinas treated with 5,6‐DHT alone (i.e., in which the indoleamine‐accumulating neurons remained) numerous processes were observed which were both pre‐ and postsynaptic to bipolar terminals. These observations suggest that the indoleamine‐accumulating processes synapse with bipolar cells.The results show that the dopaminergic neurons form a network involving only amacrine cells, suggesting a regulatory function for them. By analogy with the dopaminergic interplexiform cells of the goldfish retina, it is suggested that the dopaminergic neurons in the rabbit may regulate lateral inhibitory effects mediated by amacrine cells. Furthermore, the finding that the dopaminergic and indoleamine‐accumulating cells apparently have a different synaptic organization suggests that it is appropriate to categorize amacrine cells according to their transmitter content as well as their morphology.
Histochemical, pharmacological and microspectrofluorometric analysis of new sites of serotonin localization in the rat hypothalamus
Authors: Kent Daniel L. , Sladek John R. 
Published: January 2005

AbstractHistopharmacological and microspectrofluorometric analysis was applied to the rat hypothalamus for the identification of serotonin. Neuronal perikarya, especially certain of those of the endocrinologically important arcuate nucleus, were seen to contain a yellow histofluorescence which possessed spectral characteristics consistent with the serotonin fluorophor. Serotonin was localized also within vericosities of various hypothalamic nuclei, as well as within an ependymally associated network of fibers. Pharmacological administration of the serotoninprecursor, tryptophan, resulted in the identification of serotonin histofluorescence and spectra within hypothalamic neurons, yielding evidence that these neurons possess the capacity to synthesize serotonin. These newly described cells may be of importance to the regulation of hypothalamically mediated endocrine function due to their neuroanatomical placement in the medial basal hypothalamus.
Projections to the inferior olive of the cat I. Comparisons of input from the dorsal column nuclei, the lateral cervical nucleus, the spino‐olivary pathways, the cerebral cortex and the cerebellum
Authors: Berkley K. J. , Worden I. G. 
Published: January 2005

AbstractThe present experiments compare the projections from the dorsal column nuclei (DCN), the lateral cervical nucleus (LCN), the spino‐olivary pathways (SO), the motor cortex (Ms1) and the cerebellum (CB) to the inferior olive of the cat. A differential labeling strategy was used for these comparisons.It was found that projections from the contralateral DCN and LCN and the ipsilateral SO overlap extensively with each other in the dorsal accessory division of the inferior olive and the caudal half of the medial accessory olive. Projections from the contralateral motor cortex partially overlap these somato‐sen‐sory projections but they also extend into the principal division and into the rostral half of the medial accessory olive where other authors have found input from other “motor” sources such as the red n., the globus pallidus and the caudate n. The contralateral cerebellum projects heavily to most of the inferior olive except for a few regions in the caudal portions of the two accessory nuclei.These results show that there is a partial segregation between somatosensory and motor inputs within the inferior olive and that the cerebellar feedback fibers appear to avoid at least parts of those regions where the somatosensory input is heavy. Some of this segregation, particularly within the medial accessory olive and the principal n., correlates with differences in both the olivo‐cerebellar connectivity and the cytoarchitecture of these regions.Although the somatosensory and motor inputs are partially segregated, there are also several regions where these inputs overlap. These regions are: (1) an area in the medial half of the rostral portions of the dorsal accessory olive, and (2) a small oval zone in the middle of the caudal half of the medial accessory olive. This overlap provides an anatomical basis for electrophysiological evidence which demonstrates the existence of cells in some of these regions that respond to activation of both the cerebral cortex and the spinal cord (e.g., Crill and Kennedy, 1967).
The DNA content of Purkinje cells in mammals
Authors: Mann D. M. A. , Yates P. O. , Barton C. M. 
Published: January 2005

AbstractNerve cells have generally been assumed to have a diploid DNA content, typical of non‐dividing somatic cells. However several reports have suggested that certain never cell types, notably Purkinje cells of the cerebellum, are polyploid. Other studies have contradicted these findings, stating Purkinje cells to be diploid. In this paper we reinvestigate the DNA status of Purkinje cells, in a variety of mammalian species. Cell DNA content is measured on tissue smears by Feulgen microspectrophotometry. Results show that for all species examined by us, Purkinje cells, have, without exception, a DNA content comparable to that of somatic cells. A critical appraisal of the techniques used in those studies claiming a tetraploid DNA content for Purkinje cells leads us to believe our findings to a correct.
Light microscopic analysis of the kitten retina: Postnatal development in the area centralis
Authors: Tucker Gail Susan 
Published: January 2005

AbstractA method was devised for morphological localization of the area centralis, and the timecourse of its formation as a structural entity was established. Postnatal differentiation of the retina proceeds as follows: the irregularly laminated ganglion cell layer of the newborn becomes unilaminar everywhere but in the presumptive area centralis, a difference which is first discernible at five to six days of age; the outer nuclear layer is always of the same thickness in the area centralis, while in the periphery the layer thins with time; the outer nuclear layer is always thinner in the area centralis than in the periphery; inner nuclear layer thickness is invariant early in postnatal life, but in the adult it is thicker in the area centralis than in the near temporal periphery; plexiform layers from by two weeks of age and reach adult thickness thereafter.Retinal ganglion cells were measured and the percent distributions of three ganglion cell size classes (6–10 μm; 11–20 μm; 21–35 μm) were determined for the area centralis and near temporal periphery. Mean ganglion cell size is constant in center and periphery through five weeks of age, is adultlike in the periphery soon thereafter and in the center sometime after eight weeks of age. The percent distribution of ganglion cells by size class in center and periphery is not adultlike even at eight weeks of age. The implications of these observations and others are discussed relative to postnatal growth of the eye and placement of the area centralis in the retinal field and optic axis. The involvement of retinal cell proliferation, cell growth, ganglion cell dendrite formation and cell shape changes in the expansion of the retina are also discussed.
Cerebellar cortical efferent fibers of the paraflocculus of tree shrew (Tupaia glis)
Authors: Haines D. E. , Whitworth R. H. 
Published: January 2005

AbstractEfferent projections from the paraflocculus of the tree shrew (Tupaia glis) were studied utilizing the Fink and Heimer ('67) method. Cerebellar corticonuclear fibers of both dorsal (Dpf) and ventral (Vpf) divisions of the paraflocculus terminate in the lateral cerebellar nucleus (NL) and in the posterior interposed nucleus (NIP). These fibers are ipsilateral, topographically organized and arranged into at least two dozens.Following injury to either the Dpf or Vpf. degenerated axons are found in lateral and caudal regions of the NIP respectively. Consequently, these two portions of the paraflocculus have relatively exclusive terminal fields with overlap only at the periphery. Preterminal debris is seen in basically similar areas of the NL (caudolateral, caudal, ventral) after damage to either the Dpf or Vpf. This observation leads to the conclusion that the terminal fields for these areas of paraflocculur cortex are largely coextensive in the NL.In addition to the topographical representation of the Dpf and Vpf in both the NL and NIP, there is evidence that these corticonuclear fibers are also organized into the general zonal pattern hypothesized by Voogd ('69). Persistent and numerous degenerated axons from both the Dpf and Vpf end in lateral and caudal NIP, respectively, corroborating the presence of a relatively wide zone C2 in both divisions of the paraflocculus. The Dpf and Vpf also project into the NL to a terminal field that appears to consist of two portions. One part located in caudal, ventral and/or caudoventral areas of the NL and a second at slightly more rostral and rostrolateral areas. The presence of a cortical region which is affiliated with two areas of the NL substantiates not only the existence of zone D in the paraflocculus, but gives experimental evidence that it may consist of two parts as previously suggested (Voogd, '69). From the Dpf many fibers enter the NL while few are seen in this nucleus after damage to the Vpf. This suggests that zone D is wider in the Dpf and narrower in the Vpf.The results of this study do not support previous suggestions that the paraflocculus projects to either only the NL or to most of, or all of, the ipsilateral cerebellar nuclei. No projections to any contralateral cerebellar nuclei are seen. There is also no conclusive proof that the parafloccular cortex of Tupaia projects into the vestibular complex or to any other brainstem relay nuclei.
The synaptic terminations of certain midrain‐olivary fibers in the opossum
Authors: King James S. , Hamos James E. , Maley Bruce E. 
Published: January 2005

AbstractThe nuclear origin and distribution of midbrain‐olivary fibers has been described in a previous study utilizing axonal transport techniques (Linauts and Martin, '78a). The present report extends their results to the electron microscopic level and details the postsynaptic distribution of such fibers. Lesions within the ventral periaqueductal grey and adjacent tegmentum, the red nucleus or the nucleus subparafascicularis result in electron dense axon terminals within the olive at survival times of 48, 72 and 96 hours. At 72 hours, many degenerating presynaptic profiles shrink, become irregular in shape and are totally or partially surrounded by glial processes. The principal olivary nucleus contains the majority of these profiles. However, the subparafascicular terminals are more abundant in the rostral and intermediate parts of the medial accessory nucleus and the rubral terminals are concentrated within the dorsal lamella of the principal nucleus. The nuclear location of the degenerating terminals was determined by examination of 1 μm plastic sections cut in the transverse plane from each block face prior to thin sectioning. Degenerating terminals were counted in three cases, one from each of the three lesion sites described above. When taken together these cases show that just over 50% of the degnerating terminals are presynaptic to spiny appendages and are located within the synaptic clusters (glomeruli) described previously (King, '76). The percentage of degenerating terminals in the glomeruli increases to 70% when the lesion is in the ventral periaqueductal grey and adjacent tegmentum. The remaining degenerating terminals contact dendritic shafts outside the astrocytic boundaries of the synaptic clusters.The synaptic vesicle populations within the degenerating terminals vary with the location of the lesion. Lesions in the ventral periaqueductal grey and the adjacent tegmentum result in the degeneration of terminals with either clear spherical vesicles or endings with both clear spherical vesicles and a variable number of large dense core vesicles. In contrast, the primary degenerative changes that occur after destruction of the red nucleus or the nucleus sub‐parafascicularis are in terminals with clear spherical vesicles. When the synaptic complex was present in the plane of section, regardless of the site of the lesion, the degenerating terminals could be classified as Gray's type I.Thus, we have demonstrated that afferents from the mesencephalon terminate within synaptic clusters located in the principal and medial accessory (Part A) subnuclei of the inferior olive. Although the mesencephalic afferents have multiple origins (Linauts and Martin, '78a), many of their synaptic terminals contact spiny appendages within the synaptic clusters. This postsynaptic site also receives cerebellar terminals (King et al., '76). The origin of presynaptic profiles within the synaptic clusters that contain clear pleomorphlic vesicles is yet to be determined.
Experimental studies on the ultrastructural localization of acetylcholinesterase in the mediobasal hypothalamus of the rat
Authors: Carson Keith A. , Nemeroff Charles B. , Rone Michael S. , Nicholson Gayle F. , Kizer John S. , Hanker Jacob S. 
Published: January 2005

AbstractAcetylcholinesterase (AChE) activity has been demonstrated ultra structurally in neurons of the arcuate nucleus and associated with fibers in the arcuate nucleus and the median eminence (ME) of the rat. In addition, the effects of neonatal monosodium glutamate (MSG) treatment and Halász deafferentation on the AChE staining and localization have been studied. Neonatal MSG‐treatment resulted in loss of the majority of AchE‐positive neurons in the arcuate nucleus while leaving neuropil staining intact. Haläsz deafferentation caused a loss of arcuate neuropil activity while leaving the neuronal staining unaltered. These observations are consistent with previous biochemical results suggesting the existence of a cholinergic tuberoinfundibular system with nerve cells in the arcuate nucleus and terminals in the median eminence. In addition, the deafferentation experiments indicated that extra‐hypothalamic cholinergic fibers may innervate the arcuate nucleus. Supporting evidence from other biochemical studies and the curious paucity of histochemical and biochemical AChE activity in the ME are also discussed.
GABA‐ergic pathways in the goldfish retina
Authors: Marc Robert E. , Stell William K. , Bok Dean , Lam Dominic M. K. 
Published: January 2005

AbstractA high‐affinity uptake mechanism for [3H]‐γ‐aminobutyric acid (GABA) has been localized to type H1 cone horizontal cells and type Ab pyriform amacrine cells in the retina of the goldfish by light and electron microscope autoradiography. By stimulating isololated retinas with colored lights during incubation we have been able to use [3H]‐GABA uptake as a probe of light‐evoked changes in membrane potential. All colors of lights increase and darkness decreases [3H]‐GABA uptake by H1 cone horizontal cells. Our model of voltage dependence of GABA uptake predicts that all colors of light should hyperpolarize H1 cone horizontal cells and other investigators have shown by intracellular recording and dye‐marking that type H1 cone horizontal cells hyperpolarize to all wavelengths of light. We have also obtained evidence that dark‐induced depolarizatiion of cone horizontal cells leads to release of GABA. Type Ab pyriform amacrine cells show maximal [3H]‐GABA uptake in darkness and when exposed to green or blue lights, but red lights dramatically suppress uptake. We predict these neurons to be red‐depolarizing and recent intracellular recordings and dye‐marking by Famiglietti et al. ('77) support our conclusions. Synaptic relations of apparently GABA‐ergic neurons were investigated in the electron microscope. We propose type H1 cone horizontal cells to be both pre‐ and post‐synaptic to red‐sensitive cones and type Ab pyriform amacrine cells to be both pre‐ and post‐synaptic to red‐sensitive center‐depolarizing bipolar cells.
Development of distinct cell types in the feline red nucleus: A golgi‐cox and electron microscopic study
Authors: Sadun Alfredo A. , Pappas George D. 
Published: January 2005

AbstractThe feline RN contains neurons which fall into three size categories: giant (40–80 μm), medium (25–35 μm) and small (6–20 μm). These three populations of rubral neurons are distinguishable on the basis of a number of ultrastructural criteria and form classes not dissimilar from the traditional three divisions of cell types. Each of the three populations of rubral neurons can be further divided into three subgroups on the basis of a large number of configurational criteria discernible by the Golgi‐Cox method. Each of these nine cell types are clearly separate, distinguishable by at least three criteria, and are found in different regions of the RN.It is shown that in 5‐day prenatal kitten, rubral neurons are already organized into the aforementioned three size categories. At this age most of the subpopulations are also distinguishable by the Golgi‐Cox method. However, the giant rubral neurons (about 30 μm) and the medium sized cells (about 20 μm) are much smaller than in the adult cat. The dendrites elaborate many fine processes which emerge from multiple varicosities. The neuropil differs strikingly from that of the adult in that the vast majority of axons are small and unmyelinated.A number of changes in the RN are apparent as the kitten matures. The larger rubral cells undergo configurational changes before the smaller neurons, yet the giant cells continue to grow for a longer period of time. In the perinatal period, the extent of arborization of the dendritic trees diminishes, the number of spines decreases, and the long dendritic spines shorten. Somatic spines first appear in the giant cells at about one week after birth. In prenatal kittens, large cells frequently elaborate a tuft of fine branching processes in one region of the soma. These tufts later diminish in size and disappear by one week post‐natal.Recent investigations (Pompeianao, '59; Condé, '66; King et al., '73; Sadun, '75) indicates that the RN of the cat is highly organized and very heterogenous. Afferent terminals are restricted to certain regions of certain cell types which are themselves specifically located within the RN. This specificity is apparent in perinatal kittens, despite the manifest immature appearance of the RN.