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PubMed1996

Dynamics of cell migration from the lateral ganglionic eminence in the rat.

From previous developmental studies, it has been proposed that the neurons of the ventrolateral cortex, including the primary olfactory cortex, differentiate from progenitor cells in the lateral ganglionic eminence. The objective of the present study was to test this hypothesis. The cells first generated in the forebrain of the rat migrate to the surface of the telencephalic vesicle by embryonic day (E) 12. Using [3H]thymidine, we found that most of these cells contributed to the formation of the deep layer III of the primary olfactory cortex. To study the migratory routes of these cells, we made localized injections of the carbocyanine fluorescent tracers Dil and DiA into various parts of the lateral ganglionic eminence in living embryos at E12-E14 and subsequently maintained the embryos in a culture device for 17-48 hr. After fixation, most migrating cells were located at the surface of the telencephalic vesicle, whereas others were seen coursing tangentially into the preplate. Injections made at E13 and in fixed tissue at E15 showed that migrating cells follow radial glial fibers extending from the ventricular zone of the lateral ganglionic eminence to the ventrolateral surface of the telencephalic vesicle. The spatial distribution of radial glial fibers was studied in Golgi preparations, and these observations provided further evidence of the existence of long glial fibers extending from the ventricular zone of the lateral ganglionic eminence to the ventrolateral cortex. We conclude that cells of the primary olfactory cortex derive from the lateral ganglionic eminence and that some early generated cells migrating from the lateral ganglionic eminence transgress the cortico-striatal boundary entering the preplate of the neocortical primordium.

Animals↗
PubMed1997

Innervation of orbital and choroidal blood vessels by the pterygopalatine ganglion in pigeons.

Orbital and choroidal blood vessels in mammals are known to receive a parasympathetic innervation from the pterygopalatine ganglion, which appears to utilize vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) to increase choroidal blood flow. The present studies were undertaken to elucidate the anatomical and neurotransmitter organization of the pterygopalatine ganglion input to orbital and choroidal blood vessels in pigeons. Single- or double-label immunohistochemistry were employed on paraformaldehyde-fixed cryostat sections of the pigeon eye and surrounding orbital tissue to localize 1) VIP+ neurons and fibers; 2) choline acetyltransferase (CHAT)-containing cholinergic neurons and fibers; 3) axons containing the 3A10 neurofilament-associated antigen; and 4) neuronal NO synthase (nNOS)-containing neurons and fibers. NOS+ neurons and fibers were also identified by NADPH-diaphorase histochemistry in sections and whole-mount specimens. The pterygopalatine ganglion was found to consist of an interconnected series of three to four main microganglia of about 50-200 neurons each and numerous lesser microganglia. The major microganglia of the pterygopalatine network in pigeon lie along the superior aspect of the Harderian gland, with many additional fibers and microganglia of the network encircling the gland. Neurons of all microganglia were extremely rich in VIP, nNOS, and NADPH-diaphorase and moderate in CHAT. The majority of the pterygopalatine ganglion neurons were observed to co-contain VIP and nNOS. Axons labeled for VIP, nNOS, NADPH-diaphorase, or the 3A10 antigen could be traced from the pterygopalatine ganglion network to perivascular fiber plexi on orbital blood vessels. These orbital vessels, many of which enter the choroid posteriorly and nasally, appear to be a conduit by which pterygopalatine postganglionic fibers reach the choroid. The pterygopalatine postganglionic fibers were also seen to innervate the Harderian gland and contribute branches to the nearby ophthalmic nerve. Within the choroid, VIP+ fibers were widely scattered and sparse but were most abundant in nasal choroid. A few VIP+ and NADPH- diaphorase+ neurons were also observed in the choroid. These results suggest that pterygopalatine ganglion neurons of birds use VIP and NO to exert vasodilatory control over blood flow to and within the avian choroid.

Animals↗
PubMed1999

Nitric oxide synthase in trigeminal ganglion cells projecting to the cochlea of rat and guinea pig.

Nitric oxide (NO) influences electrophysiological and morphological parameters of the mammalian cochlea. Recently, the isoform of the NO-producing enzyme neuronal NO synthase (nNOS) has been demonstrated in spiral ganglion cells and olivocochlear neurons. The cochlea is also innervated by fibers stemming from the trigeminal ganglion (TG) and superior cervical ganglion (SCG). Whether these ganglion cells contain nNOS is not known yet. We therefore identified TG and SCG cells upon injection of Fluoro-Gold (FG) into the cochlea and retrograde neuronal transport of FG in rat and guinea pig. These ganglion cells were investigated for neuronal NOS immunohistochemically. Perikarya labeled by FG were found in the ipsilateral TG and SCG. In both species investigated, a considerable number of FG-labeled TG cells were also nNOS-immunoreactive whereas SCG cells were not. These data, demonstrating the existence of nNOS-containing TG cells that project to the cochlea, provide evidence that these neurons are further sources of nitric oxide in the cochlea.

Animals↗
PubMed1989

Effect of ganglionic stimulating and blocking agents on the fast components of colonic myoelectrical activity in the rat.

The presence of two types of fast myoelectrical activities, medium fast activity and fast activity, has been demonstrated previously in the electromyogram of colon in normal children and in the rat by the authors. An absence of medium fast activity in Hirschsprung's disease and in experimental aganglionosis of colon in the rat has also been described. In the present study the fast components of colonic myoelectrical activity were analysed during the procedures affecting ganglionic transmission. It was observed that ganglionic stimulants, such as balloon inflation, and intra-arterial injections of acetylcholine and small amounts of nicotine, increased the spike activity and the frequency of medium fast activity without affecting fast activity. The intra-arterial injections of ganglionic blocking agents, such as nicotine in large amounts and pentolinium tartrate, completely abolished the medium fast activity. These observations suggest that the ganglionic activity is responsible for the genesis of medium fast activity and that the absence of cholinergic ganglionic transmission is the most important single factor for the reported altered electromyogram pattern in aganglionosis.

Acetylcholine↗
PubMed1988

Spontaneous release of acetylcholine affects the physiological nicotinic responses of rat retinal ganglion cells in culture.

Nictonic cholinergic responses have been previously documented in mammalian retinal ganglion cells. In the present study, dissociated retinal cells were densely plated and grown in a specific batch of rat serum. When held at negative potentials during whole-cell recording with a patch electrode, the retinal ganglion cells located close to presumptive cholinergic amacrine cells in these cultures were found to respond to acetylcholine (ACh; 20-200 microM) with an apparent outward current in the presence of physiological salines on both sides of the membrane. Other nicotinic agonists (nicotine, carbachol) produced the same effect. Conductance measurements revealed that this apparent outward current was actually a decrease in a tonic inward current. Nicotinic antagonists such as d-turbocurarine (10 microM) and dihydro-beta-erythroidine (20 microM), when applied in dishes that had never been exposed to exogenous ACh, produced a similar decrease in a tonic inward current. The reversal potential of the tonic current suppressed by ACh was similar to the nicotinic current previously studied in these central neurons. Furthermore, purified acetylcholinesterase was capable of modulating the tonic inward current of the retinal ganglion cells. Lowering an excised patch of muscle into dense areas of the retinal cultures activated nicotinic channels in the muscle membrane, indicating the presence of endogenous ACh in the culture fluid. Divalent cations such as Co2+ blocked the tonic inward current of retinal ganglion cells in these cultures. Finally, direct biochemical measurements indicated that low levels of endogenous ACh (on the order of 0.5 microM near putative cholinergic amacrine cells) were present in the retinal cultures. Taken together, these results show that ACh was being spontaneously released into these cultures, resembling at least to some degree the tonic leakage of ACh found in the intact retina. This concentration of ACh was capable of tonically depolarizing the membrane potential of retinal ganglion cells exposed to this dosage. This culture system allows the study of trophic effects of ACh on a central mammalian neuron in a precisely controlled extracellular environment.

Acetylcholine↗
PubMed1996

Glutamate metabolic pathways in displaced ganglion cells of the chicken retina.

Glutamate (E) is the putative amino acid neurotransmitter used by ganglion cells, photoreceptors, and bipolar cells. Aspartate (D) and glutamine (Q) are potential precursors of glutamate, and glutamate-utilizing neurons may use one or more of these amino acids to sustain production of glutamate. We used post-embedding immunocytochemistry for several amino acid neurotransmitters to characterize the amino acid signatures for displaced ganglion cells of the avian retina. We found two neurochemical signatures for displaced ganglion cells, EQ and EDQ, in mid-peripheral and far-peripheral retina, respectively. Differences in neurochemical signatures cannot be explained by the existence of two ganglion cell populations, and we propose that the two signature categories for the large-diameter displaced ganglion cells reflect variations in the aspartate precursor pool. The transamination reaction involved in glutamate production, aspartate/oxaloacetate and alpha-ketoglutarate/glutamate, requires an active TCA cycle, since the carbon skeleton of glutamate is derived from alpha-ketoglutarate, a TCA intermediary. We hypothesized that aspartate levels vary in the normal chicken retina because eccentricity-dependent differences in oxygen availability result in changes of alpha-ketoglutarate levels, and hence, alterations in the equilibrium of the transamination reaction. We tested this hypothesis by incubating isolated chicken retinas in anaerobic conditions and found elevated aspartate immunoreactivity in subpopulations of glutamate-utilizing neurons in the central retina. Under aerobic conditions, or in retinas placed directly into fixative, retinal samples from the central edge of the pecten did not show differential cellular staining for aspartate. We have, therefore, identified differences in neurochemical signatures for retinal neurons involving changes in active maintenance of precursor pools.

Aerobiosis↗
PubMed2000

Diffuse bipolar cells provide input to OFF parasol ganglion cells in the macaque retina.

Parasol retinal ganglion cells are more sensitive to luminance contrast and respond more transiently at all levels of adaptation than midget ganglion cells. This may be due, in part, to differences between bipolar cells that provide their input, and the goal of these experiments was to study these differences. Midget bipolar cells are known to be presynaptic to midget ganglion cells. To identify the bipolar cells presynaptic to parasol cells, these ganglion cells were intracellularly injected with Neurobiotin, cone bipolar cells were immunolabeled, and the double-labeled material was analyzed. In the electron microscope, we found that DB3 diffuse bipolar cells labeled by using antiserum to calbindin D-28k were presynaptic to OFF parasol cells. In the confocal microscope, DB3 bipolars costratified with OFF parasol cell dendrites and made significantly more appositions with them than expected due to chance. Flat midget bipolar cells were labeled with antiserum to recoverin. Although they made a few appositions with parasol cells, the number was no greater than would be expected when two sets of processes have overlapping distributions in the inner plexiform layer. DB2 diffuse bipolar cells were labeled with antibodies to excitatory amino acid transporter 2, and they also made appositions with OFF parasol cells. These results suggest that DB2 bipolar cells are also presynaptic to OFF parasol ganglion cells, but midget bipolar cells are not. We estimate that midperipheral OFF parasol cells receive approximately 500 synapses from 50 DB3 bipolar cells that, in turn, receive input from 250 cones.

Amino Acid Sequence↗
PubMed1996

Transplantation of oligodendrocyte progenitor cells into the rat retina: extensive myelination of retinal ganglion cell axons.

In most mammals, retinal ganglion cell axons are unmyelinated in the retina. The same axons become myelinated in the optic nerve. Various studies suggest that retinal ganglion cell axons are also in principle, myelination competent intraretinally and that non-neuronal factors at the retinal end of the optic nerve prevent the migration of oligodendrocyte progenitor cells into the retina. To test this hypothesis directly, we injected oligodendrocyte progenitor cells into the retina of young postnatal rats. We observed massive myelination of ganglion cell axons in the retina 1 month after cell transplantation. Electron microscopic analysis revealed that intraretinal segments of ganglion cell axons were surrounded by central nervous system myelin sheaths with a normal morphology. Our results thus provide direct evidence for the myelination competence of the intraretinal part of rat retinal ganglion cell axons.

Animals↗
PubMed1999

Cross-species collapse activity of polarized radial glia on retinal ganglion cell axons.

Inhibition of incorrect axonal outgrowth has been shown to be a crucial guidance mechanism during the development of the nervous system. Within the visual system of chick and rat, extension of retinal ganglion cell axons is essentially restricted to distinct layers of the retina and distinct brain regions such as the tectum opticum. In addition, populations of ganglion cells from defined retina locations project topographically to defined tectal areas, their growth possibly being inhibited by radial glia in incorrect tectal regions. In the current study, we aimed to analyse potential inhibitory activity of retinal glia during outgrowth of ganglion cell axons of embryonic chick and rat. The response of ganglion cell axons originating from different retina locations when exposed to purified retinal radial glia cell membranes were monitored in collapse assays by time lapse video recording. The interaction of axons growing on purified glial somata or glial endfeet was analysed in outgrowth assays. Our results indicate that (1) nasal and temporal chick growth cones are equally induced to collapse by cell membranes from retinal radial glia: 75% nasal and 72% temporal. (2) The collapse inducing component of radial glia can be inactivated by defined heat treatment, reducing collapsing activity to 6% nasal and 5% temporal. (3) Rat growth cones respond in a similar way to chick radial glia. (4) Rat axons grow perfectly on endfeet but not on somata of radial glia of the chick. In summary, the data suggest that radial glia are functionally polarized with permissive endfeet and inhibitory somata based on heat-labile proteins. Glia polarization is likely to inhibit aberrant growth of ganglion cell axons into outer retina layers. However, retinal radial glia are unlikely to participate in preordering axons within the retina and therefore do not affect the topographic projection. Finally, the inhibitory function of radial glia is conserved between birds and mammals and represents possibly a fundamental mechanism for structuring the central nervous system.

Animals↗
PubMed2000

Fibroblast growth factors (FGF-1, FGF-2) promote migration and neurite growth of mouse cochlear ganglion cells in vitro: immunohistochemistry and antibody perturbation.

To study the effect of FGF in the early development of the sensory neurons of the auditory system, we established a culture preparation of ganglionic neuroblasts engaged in migration and process outgrowth. The presumed anlage of the cochlear ganglion was dissected from E11 otocysts, just as the neuronal precursors were migrating. The cultures were divided into 4 groups and supplemented for 7-9 days with either hrFGF-1 or hrFGF-2 or both or with defined medium only (control group). Measurements of the increase in explant growth, neuroblast migration, and neurite outgrowth were made by time-lapse imaging techniques in living cultures. Either FGF-1 or FGF-2 alone stimulated early migration and outgrowth of the ganglion cells by 5-10x. The effect of combining FGF-1 and FGF-2 was greater than either alone, but less than additive, consistent with a shared receptor. BrdU labeling confirmed that the effect was on migration, not on proliferation. Adding a neutralizing antibody for FGF-2 to the cultures inhibited migration and neurite outgrowth, suggesting an endogenous FGF-2 activity in these functions. Immunocytochemical observations in vitro and in situ with antibodies to FGF-1, FGF-2, or FGF receptor (R1) demonstrated immunopositive staining of the migrating ganglionic neuroblasts, their processes, and growth cones at corresponding stages (E13). Also non-neuronal cells, hair cells, and Schwann cells (in situ) expressed FGF-1 and FGF-2. Evidently both FGF-1 and FGF-2 play important roles in the migration and initial differentiation of cochlear ganglion neurons in the mouse.

Animals↗
PubMed1994

Physiology, morphology and spatial densities of identified ganglion cell types in primate retina.

The use of in vitro preparations of primate retina provides new perspectives on the mosaic organization and physiological properties of three ganglion cell types that project to the lateral geniculate nucleus: the parasol, midget and small bistratified cells. Dendritic field sizes and coverage for the three types suggest that their relative densities vary with eccentricity. Of the total ganglion cells in the human fovea, midget cells constitute about 90%, parasol cells about 5%, and small bistratified cells about 1%. In the periphery, midget cells make up about 40-45%, parasol cells about 20% and small bistratified cells about 10% of the total. Thus from peripheral to central retina the number of midget ganglion cells progressively increases relative to the parasol and small bistratified types. Physiological properties of these cells have recently been studied in macaque (Macaca nemestrina) retina by combining intracellular recording and dye injection. As expected, parasol cells, projecting to geniculate magnocellular layers, give phasic, non-opponent light responses. Midget cells, which project to geniculate parvocellular layers, show opponent responses sensitive to only mid and long wavelengths; no evidence of short-wavelength-sensitive cone (S-cone) input to any midget ganglion cell has been found. However, the small bistratified cells, which also project to the parvocellular geniculate layers, give a strong blue-ON response to stimuli designed to modulate S-cones. Thus, S-cone and medium- or long-wavelength-sensitive cone opponent signals arise from morphologically distinct ganglion cell types that project in parallel to the lateral geniculate nucleus.

Animals↗
PubMed1983

Postnatal development of spiral ganglion cells in the rat.

The postnatal development of the spiral ganglion in the albino rat was studied using light and electron microscopy. The morphological characteristics distinguishing type 1 from type 2 spiral ganglion cells were defined, and the critical period for distinguishing the two types of neurons was identified. At birth, the spiral ganglion consists of a homogeneous population of small, densely packed, spherical cells that have large cytoplasmic-to-nuclear ratios. During the first postnatal week, the cells mature slowly. At this period the myelin sheath around the cell bodies generally consists of only a few layers of loose myelin. Long glial fingers extend around the cell processes and soma, particularly the filopodial extensions of the somatic membrane. Type 2 spiral ganglion cells can be distinguished at postnatal day 8. Viewed with the phase-contrast microscope these cells are smaller and have more darkly staining nuclei and more lightly staining cytoplasm than the type 1 cells. The most characteristic ultrastructural features of the type 2 neurons are the densely packed neurofilaments in the cytoplasm and lack of compact myelin around the cell soma. By day 14, spiral ganglion cells are morphologically mature, although the myelin sheath continues to thicken. The results are discussed in relation to the electrophysiological development of the auditory system and the morphological maturation of the organ of Corti.

Animals↗
PubMed1991

Topography and morphology of retinal ganglion cells in Falconiforms: a study on predatory and carrion-eating birds.

The topographic distribution of retinal ganglion cells and their cell body size have been studied in five Falconiform species, including predatory (chilean eagle Buteo fuscenses australis, and sparrow hawk Falco sparverius) and carrion-eating (chimango caracara Milvago chimango; condor Vultur gryphus, and black vulture Coragyps atratus) birds. All these species had a well defined nasal fovea and a horizontal streak. Instead of a temporal fovea as in eagles and hawks, an afoveate temporal area is present in chimango, condor, and vulture. The highest ganglion cell density was found in the nasal fovea of Falco and Buteo with 65,000 and 62,000 cells/mm2, respectively. A negative correlation between ganglion cell density and cell body size was found in all the species studied. The specializations of the temporal retina showed a rather homogenous population of medium sized neurons, while the nasal foveas showed a homogeneous population of smaller ganglion cells. Finally, the peripheral retina showed a heterogeneous population of large, medium, and small ganglion cells. Predatory behavior appears to be closely related to foveal specializations, and is best exemplified in the eagle and hawk and to a lesser extent in the chimango.

Animals↗
PubMed2005

Cell birth and death in the mouse retinal ganglion cell layer.

Here we describe quantitatively the birth and death of the two separate populations of neurons, ganglion cells and displaced amacrine cells, in the mouse retinal ganglion cell layer (GCL). The two cell types, which are roughly equally numerous, were distinguished pre- and postnatally by labeling the ganglion cells retrogradely with fluorescent dye. Embryos were labeled cumulatively with bromodeoxyuridine (BrdU) delivered by an osmotic minipump implanted in the mother; cell birth dates were established as having occurred before or after pump implantation. Early cohorts (GCL cells born before embryonic day [E] 11.8 and E12.8) were 98+/-1.1% and 99+/-0.2% ganglion cells (mean+/-SEM), respectively, and a late cohort (born after E15.8) was 97+/-1.2% displaced amacrines. Thus birth date was a strong predictor of a GCL cell's ultimate identity. Cell death in each cohort was estimated by counting cells at different time points (soon after the cohort was produced and later) and subtracting the later from the earlier number. This method avoids the problem of simultaneous birth and death that has plagued many of the earlier attempts to assess cell death. Negligible numbers died during the first week after a cell's birthday. The amount of cell death differed in the two cohorts; 48.5+/-15% and 29.0+/-12.4% in early and late, respectively, and most of it was postnatal. These findings disagree sharply with an earlier conclusion that ganglion cells die within 5 days of their birthdays or not at all.

Animals↗
PubMed1979

Spiral ganglion cell counts in an age-graded series of rat cochleas.

Spiral ganglion cells in the cochleas of Sprague-Dawley rats in various age groups were counted in order to assess the extent and location of cell degeneration with age. Cells in every tenth section of serially sectioned plastic embedded cochleas were counted in the light microscope. The median cell number for the 1- to 2-month-old animals was 15,800 cells. This number was first seen to be significantly reduced (-14%) in the 23-month-old animals. At 27 to 29 months the ganglion cell number was reduced by 20%, while at 33 to 34 months there was a 17% loss. Losses were found throughout the length of the ganglion with the greatest losses at the lower basal and apical ends. In the oldest group, these losses amounted to 28% and 33%, respectively. Type II ganglion cells first showed a significant decrease in number in the 27- to 29-month-old group, when a 32% loss was seen. The same loss was seen in the 33- to 34-month-old group. Unlike the type I cells which are lost throughout the length of the ganglion, type II cells were not significantly reduced in number at the basal end, but decreased by as much as 42% in the middle and apical regions.

Age Factors↗
PubMed1981

Neurogenesis in the trigeminal ganglion of the albino rat: a quantitative autoradiographic study.

The time of neuron origin in the trigeminal ganglion was examined in autoradiograms of 60-day-old rats that were exposed to a single pulse of 3H-thymidine on day 11, 12, 13, 14, or 15 of gestation. Heavily labeled neurons, representing cells in or near their last mitotic division at the time of the pulse label, were present in animals injected between embryonic days 11 and 13 with a peak on day 12. Within this time period, larger neurons were generated prior to smaller neurons with a peak for larger cells on day 12 and for smaller cells on day 13. Thus, the majority of trigeminal ganglion neurons are generated over a three-day period just after the midpoint of gestation. Neuron number, size, type, and cytoarchitectural organization were also examined in the ganglion. The mean neuron count per ganglion was 52,372. The size distribution of these cells ranged continuously from 7-61 microns (mean diameter) with no evidence for clearly defined subpopulations. The staining intensity and distribution patterns of the Nissl substance varied greatly from cell to cell precluding the classification of cells as light or dark. Little correspondence between these Nissl features and cell size was found. Among the clusters and rows of neurons in the ganglion, we did not see consistent cytoarchitectonic patterns which might reflect specific sensory receptive fields.

Animals↗
PubMed1983

Structural basis of orientation sensitivity of cat retinal ganglion cells.

We investigated the structural basis of the physiological orientation sensitivity of retinal ganglion cells (Levick and Thibos, '82). The dendritic fields of 840 retinal ganglion cells labeled by injections of horseradish peroxidase into the dorsal lateral geniculate nucleus (LGNd) or optic tracts of normal cats. Siamese cats, and cat deprived of patterned visual experience from birth by monocular lid-suture (MD) were studied. Mathematical techniques designed to analyze direction were used to find the dendritic field orientation of each cell. Statistical techniques designed for angular data were used to determine the relationship between dendritic field orientation and angular position on the retina (polar angle). Our results indicate that 88% of retinal ganglion cells have oriented dendritic fields and that dendritic field orientation is related systematically to retinal position. In all regions of retina more that 0.5 mm from the area centralis the dendritic fields of retinal ganglion cells are oriented radially, i.e., like the spokes of a wheel having the area centralis at its hub. This relationship was present in all animals and cell types studied and was strongest for cells located close to the horizontal meridian (visual streak) of the retina. Retinal ganglion cells appear to be sensitive to stimulus orientation because they have oriented dendritic fields.

Animals↗
PubMed1985

Ganglion cells in retinae transplanted to newborn rats.

Cells projecting out of retinal transplants placed over the tectum of newborn rats were studied by labelling with horseradish peroxidase 1 month or more after transplantation. Using this technique, it was found that only cells with the dendritic characteristics of ganglion cells were labelled and, furthermore, that the major classes of ganglion cells seen in normal retinae were also present in the transplants. The cell body size histograms of ganglion cells in normal and transplanted retinae compared closely with each other. Dendritic trees were closely confined by the limits of the inner plexiform layer, and if that layer was folded or distorted, they were themselves frequently abnormal. While axons usually coursed over the surface of the retinal transplants, they quite often followed an anomalous course crossing the individual layers. It appears, therefore, that this transplantation procedure has relatively little impact on the ability of ganglion cells to develop many of their characteristic morphological features. Whether the different functional responses of the various ganglion cell classes are also preserved after transplantation is a matter for further investigation.

Animals↗