SEARCH · PubMed Health

Results for “OPTIC PATHWAY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources

PubMed1991

Microglia in tadpoles of Xenopus laevis: normal distribution and the response to optic nerve injury.

We have studied the distribution of microglia in normal Xenopus tadpoles and after an optic nerve lesion, using a monoclonal antibody (5F4) raised against Xenopus retinas of which the optic nerves had been cut 10 days previously. The antibody 5F4 selectively recognizes macrophages and microglia in Xenopus. In normal animals microglia are sparsely but widely distributed throughout the retina, optic nerve, diencephalon and mesencephalon (other regions were not examined). After crush or cut of an optic nerve, or eye removal, there occurs an extensive microglial response along the affected optic pathway. Within 18 h an increase in the number of microglial cells in the optic tract and tectum can be detected. This response increases to peak at around 5 days after the lesion. At this time the nerve distal to the lesion contains many microglial cells; the entire optic tract is outlined by microglia, extended along the degenerating fibres; and the affected tectum shows a heavy concentration of microglia. This microglial response thereafter decreases and has mostly gone by 34 days. We conclude that the microglial response to optic nerve injury in Xenopus tadpoles starts early, peaks just before the regenerating optic nerve axons enter the brain, and is much diminished by the time the retinotectal projection is re-established. The timing is such that the microglial response could play a major role in facilitating regeneration.

Animals↗

PubMed1995

FGF signaling and target recognition in the developing Xenopus visual system.

We report that the growth cones of Xenopus retinal ganglion cells express fibroblast growth factor receptors (FGFRs) and that bFGF stimulates neurite extension from cultured retinal neurons. Furthermore, bFGF is abundant in the developing optic tract but is reduced in the optic tectum. To test whether FGF signaling plays a role in axonal guidance in vivo, bFGF was exogenously applied to the developing optic pathway in "exposed brain" preparations. FGF-treated retinal axons navigate normally through the optic tract, but the majority veer aberrantly at the tectal border and bypass the target. Our results implicate FGF signaling in target recognition and suggest that diminished levels of bFGF in the tectum cause arriving axons to slow their growth.

Animals↗

PubMed2002

Optic nerve arteriovenous malformation causing optic apoplexy: case report.

OBJECTIVE AND IMPORTANCE: Vascular malformations in the optic pathway are rare. Only one case of pathologically confirmed arteriovenous malformation (AVM) of the optic nerve has been reported previously. We document the case of a patient with an optic nerve AVM who presented with optic apoplexy that was diagnosed with the use of magnetic resonance imaging. CLINICAL PRESENTATION: A 15-year-old girl developed left visual disturbance of sudden onset while playing badminton. A magnetic resonance imaging scan disclosed left optic nerve swelling and intraoptical hemorrhage, although an angiogram did not reveal abnormal vessels. INTERVENTION: The patient underwent total removal of the hematoma and tangles of the abnormal vessels in the left optic nerve, which was diagnosed pathologically as an AVM. The patient recovered visual acuity, but the left visual field defect remained unchanged. CONCLUSION: Along with cavernous malformations and optic gliomas, AVMs can be a rare cause of optic nerve apoplexy. T2-weighted magnetic resonance imaging is useful in rendering the diagnosis of an optic nerve AVM, observed as a mass lesion consisting of serpiginous, tangled, low-intensity bands. Early surgical treatment is recommended to obtain a rapid recovery.

Adolescent↗

PubMed2005

Inactivation of NF1 in CNS causes increased glial progenitor proliferation and optic glioma formation.

The gene responsible for neurofibromatosis type 1 (NF1) encodes a tumor suppressor that functions as a negative regulator of the Ras proto-oncogene. Individuals with germline mutations in NF1 are predisposed to the development of benign and malignant tumors of the peripheral and central nervous system (CNS). Children with this disease suffer a high incidence of optic gliomas, a benign but potentially debilitating tumor of the optic nerve; and an increased incidence of malignant astrocytoma, reactive astrogliosis and intellectual deficits. In the present study, we have sought insight into the molecular and cellular basis of NF1-associated CNS pathologies. We show that mice genetically engineered to lack NF1 in CNS exhibit a variety of defects in glial cells. Primary among these is a developmental defect resulting in global reactive astrogliosis in the adult brain and increased proliferation of glial progenitor cells leading to enlarged optic nerves. As a consequence, all of the mutant optic nerves develop hyperplastic lesions, some of which progress to optic pathway gliomas. These data point to hyperproliferative glial progenitors as the source of the optic tumors and provide a genetic model for NF1-associated astrogliosis and optic glioma.

Animals↗

PubMed1985

The morphology of growth cones of regenerating optic nerve axons.

The morphology of growth cones of regenerating optic nerve axons was examined by light and electron microscopy in adult frogs (Rana pipiens), using a horseradish peroxidase (HRP) fiber-filling method, during early and later phases of regeneration. Optic nerve regeneration was initiated unilaterally by crushing the optic nerve in mid-orbit. Fiber filling was accomplished by severing the affected nerve closer to the eye 24-48 hrs. prior to sacrifice and applying HRP to the central stump. Regenerating axons and their growth cones were observed in the optic nerves, chiasma, tract, pretectal neuropil, and optic tectum. Growth cones of normal-appearing axons varied in shape and size. Flattened, foliate growth cones similar to those commonly described in vitro were observed in the pretectal neuropil and optic tectum. Other growth cones having vermiform, lanceolate, spatulate, and bulbous forms were observed throughout the optic pathway at all stages examined, although the longer (up to 70 micrograms) wormlike structures appeared only in the optic tract during the early period of outgrowth. Nearly complete serial-section reconstructions were obtained for two growth cones in the contralateral optic tectum at 8 wks. regeneration time. One was thinly flattened (to 30-50 nm in places) and extended broadly (8 micrograms in diameter) in contact with a neuronal perikaryon. The other formed a hood over the blind end of a severed, nonregenerating myelinated axon, which was normal-appearing except at its end within the confines of the growth cone. Morphological variation among the growth cones is discussed in relation to other descriptive in vivo studies and views concerning growth cone motility.

Animals↗

PubMed1999

Sarcoidosis of the eye, orbit, and central nervous system. Role of MR imaging.

Sarcoidosis, a systemic disease of unknown cause, frequently involves the eye, orbit, and central nervous system. The MR imaging findings of orbital and optic pathway sarcoidosis may closely resemble several other orbital and intracranial diseases. This article reviews MR imaging findings of sarcoidosis when it involves the eye, orbit, and visual pathways. Careful review of MR findings and other neuroimaging findings and clinical characteristics will reduce the incidence of mistaking optic nerve and chiasmal sarcoidosis for meningioma or glioma.

Adolescent↗

PubMed2002

Age-related changes underlie switch in netrin-1 responsiveness as growth cones advance along visual pathway.

Retinal axons are led out of the eye by netrin-1, an attractive guidance cue which is secreted at the optic nerve head. In the optic pathway, however, netrin-1 is expressed in areas that exclude retinal axon growth. This suggests that axons may change in their responsiveness to netrin-1 as they advance along the pathway. Indeed, in our 'whole-pathway' preparation in Xenopus, a gradual change from attraction to repulsion occurred as retinal axons emerged from progressively distal points along the pathway. We also found that axons that were aged in culture without pathway experience underwent a similar change, which correlated with a decline in cyclic AMP (cAMP) and netrin-1 receptor expression. Cyclic AMP elevators and adenosine A2b receptor agonists rejuvenated the behavior of old growth cones, causing them to regain attraction to netrin-1, whereas antagonists caused young growth cones to be repelled. These findings show that netrin-1 responsiveness is developmentally regulated and suggest that intrinsic changes that lower cAMP levels underlie this regulation.

Aging↗

PubMed1999

Assessing ocular drug delivery with lachrimal scintigraphy.

In order to transmit well focused images to the retina, the eye must have constant dimensions and an unclouded optical pathway. These requirements dictate that the eye has a well developed system to ensure consistent optics and that any material applied to the eye is rapidly cleared. Unfortunately, this can severely limit the effectiveness of topically applied medication. This review outlines a key method by which ocular drug delivery can be assessed - lachrimal scintigraphy - in a non-invasive, physiologically relevant setting.

Journal Article↗

PubMed1994

Optic nerve glioma presenting as a huge intrasellar mass. Case report.

We report the case of a twelve-year-old boy who presented with visual impairment and headache and was found to harbour a purely intrasellar cystic pilocytic astrocytoma originating from proximal left optic nerve. The mass was explored transcranially and decompression of the optic apparatus and subtotal resection of the cyst wall was accomplished. The patient received post-operative radiotherapy and stays symptom-free after two years. A review of the literature revealed six cases of optic pathway astrocytomas associated with cyst formation. Our case appears as the first case of an optic glioma to present as an intrasellar mass.

Adult↗

PubMed1997

Visual connections of the atypical diencephalic nucleus rostrolateralis in Pantodon buchholzi (Teleostei, Osteoglossomorpha).

Among the many thousands of teleost fish species, a diencephalic nucleus rostrolateralis (RL) has been identified in only six widely divergent species. In one of these, Pantodon buchholzi, its retina projects to both RL and the optic tectum, the latter in a visuotopic manner. The ventral part of the retina beneath a horizontal black-pigmented septum connects to the dorsomedial optic tectum and nucleus RL. The dorsal part of the retina connects to the lateroventral optic tectum and little, if at all, to RL. Using DiI tracing, the position of RL in the optic pathway of this fish has been directly demonstrated. Cells in the stratum periventriculare of the dorsomedial optic tectum contribute to the afferent input of RL (bilaterally); cells in the ventrolateral tectum do not. RL is also reciprocally connected with the torus longitudinalis and may project to three nuclei of the preglomerular complex. Ganglion cells in the retina that project to RL are sparsely distributed throughout the ventral hemiretina compared with ganglion cells that project to the optic tectum. Since this fish is an obligatory surface feeder, the neuroanatomical connectivity of nucleus RL in P. buchholzi suggests a role in the fish's visual identification of targets for feeding behavior.

Animals↗

PubMed2006

Differential modulation of thalamic neurons by optokinetic nuclei in the pigeon.

The visual system in the pigeon is composed of the tectofugal, thalamofugal and accessory optic pathways. Though their anatomy and physiology have been extensively studied, the functional interactions between these pathways are largely unknown. The present study shows by using multiple electrophysiological techniques that firing activity in the nucleus opticus principalis thalami (OPT) of the thalamofugal pathway is differentially modulated by the pretectal nucleus lentiformis mesencephali (nLM) and the nucleus of the basal optic root (nBOR) of the accessory optic system, two optokinetic nuclei responsible for generating eye movements to stabilize the image on the retina. Reversible inactivation, electrical stimulation, microiontophoresis and receptive field mapping experiments all consistently indicate that the nBOR-OPT pathway is inhibitory and mediated by GABA as a transmitter and its GABAA receptors, whereas the nLM-OPT pathway is excitatory and mediated by glutamate as a transmitter and its NMDA receptors. They also differentially modulate the size and/or responsiveness of receptive fields in OPT cells as well. Numerous electrode tip sites were histologically confirmed in the neural structures under study. The results suggest that these optokinetic nuclei may dually modulate the transfer of visual information from the retina to the telencephalon at the thalamic level during eye movements.

Acetylcholine↗

PubMed1978

Visual receptive-field properties of single cells in the rat superior colliculus.

Receptive-field properties were studied in single cells in the visual layer of the albino rat's superior colliculus. All the samples (N = 195) were identified as one of the four classes (I-, II-, III- and IV-cells) which were established previously on the bases of the response properties to single shocks to the optic pathway and of the recording sites. The four classes were located more deeply in the superior colliculus roughly in the order of from I to IV. Response latencies to single shocks to the optic chiasm were shortest in the III-cells, intermediate in the II-cells and longest in the I- and IV-cells. These cell classes turned out to be different from each other in a number of visual properties. 1) Receptive-field centers in the I- and II-cells (N = 26 and 27, respectively) were of either the ON-OFF or the ON type. Of class III (N = 47), one subgroup (IIIa) consisted mostly of the OFF type whereas the other (IIb) was made up mostly of the ON-OFF type. About two-thirds of the IV-cells (71/95) were of either the ON, the OFF or the ON-OFF type; except for two cells, the rest were all of the moving-sensitive type. 2) The average size of the receptive-field center was small (5.4 degrees +/- 2.3 degrees) in the class I, intermediate in the classes II and III (8.1 degrees +/- 2.1 degrees and 7.1 degrees +/- 2.7 degrees, respectively) and large in the class IV (18.1 degrees +/- 15.9). 3) Responsiveness to moving light stimuli (speeds, 40 degrees--90 degrees/sec) decreased in the order of IIIa, II and IIIb, and I and IV. 4) Maintained activity was lower in the superficially located cells (I, II and IIIa) than in the deeply located ones (IIIb and IV).

Afferent Pathways↗

PubMed1980

Progressive somatofugal activation of cerebroside sulfotransferase in the developing chick optic fibers.

A myelination parameter of the chick optic pathway has been investigated: the activity of cerebroside sulfotransferase. Evidence is presented for a somatofugal progression of the enzyme activity peak along the optic nerve, chiasm, optic tract, tectum anterior, and tectum posterior. The enzyme activity appears on the fifteenth embryonic day and reaches a maximum in the nerve two days before hatching. One day after hatching, the peak is found in the chiasm, and three days after that in the optic tract. The peak is found in the tectum anterior on the tenth day. The results suggest a somatofugal progression of myelination.

Animals↗

PubMed1998

Functional architecture in monkey inferotemporal cortex revealed by in vivo optical imaging.

To investigate the functional organization in the monkey inferotemporal cortex, which is the last exclusively visual area along the ventral visual cortical pathway, optical imaging based on intrinsic signals was carried out. We first conducted single-cell recordings with microelectrodes and determined the features critical for the activation of single cells. For the subsequent optical imaging, each critical feature was presented, which evoked multiple dark spots. Individual spots were approximately 0.5 mm in diameter and one of them covered the site of the electrode penetration at which the particular critical feature had been determined. The degree of stimulus selectivity varied from spot to spot, and from region to region even within a spot. Some regions were activated only by one of 12- 16 stimuli, while others by more than three stimuli. There were spots specifically activated by faces, and the position of activation spot changed gradually along the cortical surface as the stimulus face was rotated in depth. The length of the overall region along the direction of shift of these spots was approximately 1 mm. These results confirm the regional clustering of cells with similar stimulus selectivity and suggest larger units in which some parameters of object features are continuously mapped.

Animals↗

PubMed2004

Expression of a catalytically inactive transmembrane protein tyrosine phosphatase epsilon (tm-PTP epsilon) delays optic nerve myelination.

Reversible tyrosine phosphorylation is integral to the process of oligodendrocyte differentiation. To interfere with the subset of the phosphorylation cycle overseen by protein tyrosine phosphatase epsilon (PTP epsilon) in oligodendrocytes, we applied a substrate-trapping approach in the development of transgenic mice overexpressing a catalytically inactive, transmembrane PTP epsilon-hemaglutinin (tm-PTP epsilon-HA) from the dual promoter element of the gene encoding the myelin protein 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP). Transgene expression peaked during the active myelinating period, at 2-3 weeks postnatal. Two tyrosine phosphoproteins, alpha-enolase and beta-actin, were phosphorylated to a greater degree in transgenic mice. Despite a high degree of tm-PTP epsilon-HA expression, myelin was grossly normal in nearly all axonal tracts. Phenotypic abnormalities were limited to optic nerve, where a decrease in the degree of myelination was reflected by reduced levels of myelin proteins on postnatal day 21 (PND21), as well as a decrease in the density of differentiated oligodendrocytes. The optic chiasm was reduced in thickness in transgenic mice; optic nerves similarly exhibited a reduction in transverse width. Further analyses of the optic pathway demonstrated that transgenic protein was unexpectedly present in retinal ganglion cells, whose axons are the targets of myelination by optic nerve oligodendrocytes. On PND28, transgenic protein declined dramatically in both oligodendrocytes and retinal ganglion cells contributing to the recovery of optic nerve myelination. Thus, delayed myelination arises only when tm-PTP epsilon-HA is simultaneously expressed in myelin-forming glia and their neuronal targets. While tm-PTP epsilon related signaling pathways may figure in axon-glial interactions, interfering with tm-PTP epsilon activity does not perceptibly affect the development or myelinating capacity of most oligodendrocytes.

Animals↗

PubMed1998

Organization of retinal axons within the optic nerve, optic chiasm, and the innervation of multiple central nervous system targets Rana pipiens.

Light microscopic analysis of the optic nerve, chiasm, and optic tracts of Rana pipiens after the anterograde and retrograde transport of horseradish peroxidase has shown that retinal ganglion-cell axons reach the optic nerve head in chronotopically organized fascicles that form bands across the intraocular optic nerve. These bands of fascicles are divided along the midline in a "zone of reorganization" to create two full maps of the retinal surface; however, this map is discontinuous in that nasal and temporal quadrants are adjacent to one another. In the intracranial portion of the optic nerve, axons undergo another reorganization such that peripheral retinal axons shift position and become localized laterally and ventrally, whereas centrally placed axons become localized dorsally. Within this reorganization, the nerve is reconfigured into laminae of axons, and each lamina consists of age-related axons organized into two retinal maps. In the ipsilateral chiasm, axons diverge to form three central, optic tracts: the medial optic tract, the projection to the corpus geniculatum, and the basal optic root. Ipsilateral axons leave the chiasm at the same level of the chiasm as do their contralateral counterparts. The remaining axons converge in the lateral diencephalon to form a fourth fascicle, the marginal optic tract. Thus, within the optic chiasm, a sequence of positional transformations occur that result in the formation of multiple optic pathways. The various changes in axonal trajectory always coincide with changes in the orientation of cell groups that lie within the nerve and optic chiasm.

Animals↗

PubMed1987

The distribution of axons according to diameter in the optic nerve and optic tract of the rat.

The distribution of axons according to diameter was examined in the optic nerve and optic tract of adult hooded rats. Observations were made on semithin sections, and measurements of axonal diameters were made on electron micrographs taken from various locations across thin sections through the optic nerve and tract. The distribution of axons by size differs markedly in the optic nerve and tract. Coarse (greater than 2 microns) and fine (less than or equal to 2 microns) axons are distributed throughout all regions of the optic nerve. In the optic tract, in contrast, coarse axons are especially dense dorsally, at the deep border of the tract, while they are absent ventrally, subjacent to the pial surface. No regions of the optic nerve contain densities of coarse axons as high as the deep nor as low as the superficial extremes of the optic tract. Nevertheless, even at the deep (dorsal) border of the optic tract, the coarse axons make up only a small minority (roughly 15%) of the total number of axons in that region. The axons 2 microns or smaller may be divisible into two overlapping, fine and intermediate, diameter classes, that are partially segregated within the optic tract, but not in the optic nerve: the distributions of axon diameters smaller than 2 microns are skewed to distinctly smaller diameters at the dorsal and ventral extremes of the optic tract, while in between, at mid-positions along the deep-to-superficial axis of the optic tract, the axon size distributions contain many more axons greater than 1 micron in diameter. These different axon diameter groups may arise from the morphologically distinct retinal ganglion cell types, and may underlie the components of the trimodal compound axon potential seen in the rat's primary optic pathway. Their partial segregation within the tract anticipates the partial segregation of their terminal arborizations within the laminae of the dorsal lateral geniculate nucleus. The rearrangement of axons into a partial segregation by size within the optic tract may indicate a chronology of axonal arrival during early development, proximity to the pial surface being an index of recency of arrival. As axonal outgrowth and neurogenesis appear to be directly related within the retinal ganglion cell population in mammals, the relative birthdates of the retinal ganglion cell types giving rise to the axon diameter classes in the rat may be inferred from the present results.

Animals↗

PubMed1979

Optic neuropathy in a horse.

A 10-month-old thoroughbred colt developed sudden complete blindness; no other neurological abnormality was detected. At necropsy 3.5 months later lesions were confined to both optic pathways in which there was extensive degeneration of axons and myelin and gliosis. The cause of the optic lesion was not determined but the lesion may be a toxic neuropathy.

Animals↗