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At least 505 records · Page 28Linked to original sources
PubMed1998

Neurotrophins in the developing and regenerating visual system.

The neurotrophins NGF, BDNF, NT-3 and NT-4 have a wide range of effects in the development and regeneration of neural circuits in the visual system of vertebrates. This review focuses on the localization and functions of neurotrophins in the retina, lateral geniculate nucleus, suprachiasmatic nucleus, superior colliculus/optic tectum, and isthmic nuclei. Research of the past 20 years has shown that neurotrophins and their receptors are localized in numerous visual centers from the retina to the visual cortex, and that neurotrophins influence proliferation, neurite outgrowth and survival of cells in the visual system in vitro and in vivo. A relationship between electrical activity and neurotrophic functions has been established in several visual centers in the CNS, and neurotrophins have been implicated in synaptic plasticity in the visual cortex. Besides functions of neurotrophins as retrograde, target-derived trophic factors, recent data indicate that neurotrophins may have anterograde, afferent as well as local, paracrine actions in the retina, optic nerve and the visual cortex. Some neurotrophins appear to regulate proliferation and survival of glial cells in the optic pathways. Neurotrophins increase the survival of retinal ganglion cells after axotomy or ischemia and they promote the regeneration of retinal ganglion cell axons in some vertebration. Neurotrophins also rescue photoreceptors from degeneration. These findings implicate the neurotrophins not only as important regulators during development, but also as potential therapeutic agents in degenerative retinal diseases and after optic nerve injury.

Animals↗
PubMed1994

Cell adhesion molecules in the early developing mouse retina: retinal neurons show preferential outgrowth in vitro on L1 but not N-CAM.

Both L1 and N-CAM are present on optic axons early in the developing mouse retina and optic nerve. In in vitro assays on substrates of purified cell adhesion molecules cells derived from E13 mouse retinae showed vigorous neurite extension on L1 but not on N-CAM. Although retinal neurons on N-CAM showed only limited attachment to the substrate, they were able to form lamellipodia immediately around the cell perimeter. In contrast, similarly derived cortical cells showed extensive neurite outgrowth on both substrates. Under these culture conditions, nearly all of the L1 and N-CAM present in the cell membrane appeared to be sequestered on the lower surface of the growth cones and neurites, indicating that most of these cell adhesion molecules were involved in homophilic interactions. Our results suggest differential roles for L1 and N-CAM in initiation and establishment of the optic pathway.

Animals↗
PubMed2004

[Neurofibromatosis type 1 in children--with special consideration of ophthalmologic symptoms].

PURPOSE: Analysis of neurofibromatosis type I in children with special respect to ophthalmological symptoms. METHODS: It was performed a retrospective review of 18 children in period 1986-2002. The authors analysed the clinical, especially ophthalmological data, and the treatment of ophthalmological signs. RESULTS: The most frequent were the skin symptoms. All of the 18 patients had cafe au lait spots; 4 children had cutane neurofibroma; In 3 patients plexiform neurofibroma were observed. Ocular symptoms were: cutane neurofibroma in the left upper eye lid: 1 case; Lisch nodules in the iris: 5 cases; bilateral optic pathway glioma: 3 cases. One child's bilateral gliomas were inoperable, because of the intracranial progression. One child underwent surgical treatment because of the extreme exophthalmus in the right eye. Her left eye's glioma and the third case bilateral glioma needed only observation because of the loss of clinical signs, and slow progression. Family examinations were also performed: 12 children had signs in the II., III. and IV. generations, there were no symptoms in 6 family, they were new mutations. CONCLUSIONS: The most serious cases had ophthalmological symptoms, namely bilateral visual pathway gliomas that could lead to blindness. The treatment needed individually medical decision.

Child↗
PubMed1996

Weak electromagnetic fields increase the amplitude of the pattern reversal VEP response in patients with multiple sclerosis.

Visual evoked potential (VEP) studies are widely used for the diagnosis of multiple sclerosis (MS) and are also useful in monitoring the effects of various therapeutic modalities in the disease. Brief, extracerebral applications of picotesla (pT) range flux intensity electromagnetic fields (EMFs) of low frequency have been shown efficacious in the treatment of motor and cognitive symptoms in MS implying that this treatment modality improves action potential transmission in demyelinating pathways. This report documents three MS patients with a remitting-progressive course in whom two successive brief extracerebral applications of pT range EMFs caused an immediate increase (and normalization) of the amplitudes of the visual evoked response in the eye previously affected by optic neuritis. However, the pretreatment prolonged latencies of the evoked responses remained essentially unchanged after the administration of EMFs. Since the latency of the VEP reflects the degree of conduction velocity and the amplitude the degree of conduction block in demyelinating optic pathways, the report demonstrates that extracerebral applications of these EMFs may rapidly reverse conduction block in demyelinating fibers. Reversal of the conduction block, which is though to be related to changes in axonal Na+ and K+ channels and synaptic neurotransmitter release, accounts for the immediate improvement of vision and other neurological deficits observed in MS patients following exposure to these EMFs.

Electromagnetic Fields↗
PubMed1975

[The pathways and primary visual centers of Discoglossus pictus (Amphibia, Anura)].

The retinal projections of Discoglossus were examined on sixteen adult specimens uniterally deprived of retina. After a post-operative period of nine to one hundred and fifteen days, the degenerating fibers were stained with the Fink-Heimer and Ebbesson-Heimer techniques. The general scheme of primary optic pathways and centres is similar in Discoglossus and Rana. However, after a thorough study, some differences in distribution and density of degeneration suggest the idea that Ranid's visual system is not entirely representative among the Anura. Particularly, degenerative axonic terminals are abundant in ipsilateral Bellonci's neuropil, Corpus geniculatum and pretectal neuropils.

Amphibians↗
PubMed2002

Neurofibromatosis 1.

Neurofibromatosis 1 is one of the most common genetic conditions affecting the nervous system. Individuals with NF1 are predisposed to the development of peripheral nerve sheath tumors (neurofibromas and MPNSTs), astrocytomas (optic pathway gliomas), learning disabilities, seizures, strokes, macrocephaly, and vascular abnormalities. The NF1 tumor suppressor gene encodes a large protein (neurofibromin) that functions primarily as a RAS negative regulator, suggesting that targeted therapy for NF1 might derive from inhibition of the RAS signaling pathway.

Adult↗
PubMedDate not supplied

Large hypothalamic and optic chiasm gliomas in infants: difficulties in distinction.

Hypothalamic and optic chiasm gliomas may be indistinguishable clinically, radiographically, and pathologically. Ten children with giant gliomas of the hypothalamus and optic pathway, all under age 2 years, had masses greater than 3 cm in diameter. Pathologically all proven cases (seven) were cytologically benign fibrillary astrocytomas. Previous authors have recognized the difficulty in distinguishing these lesions; in this series, using previously suggested criteria, masses of optic chiasm could not be differentiated from hypothalamic origins. Likewise, at surgery and autopsy, the origin of these large masses was indeterminate. These tumors were more aggressive, invasive, and less responsive to therapy than the relatively benign orbital and optic nerve gliomas of older children and adults.

Astrocytoma↗
PubMed2005

SOX2 mutation causes anophthalmia, hearing loss, and brain anomalies.

The SOX2 transcription factor is expressed early in the embryonic stem cells of the blastocyst and later in the neural stem cells. It is a member of the SOX family of proteins that carry a DNA-binding high-mobility group domain and additional domains that regulate embryonic development and cell fate determinations. We surveyed 93 patients with severe eye malformations for mutations in SOX2. Here, we report a novel nonsense mutation in one female patient with bilateral clinical anophthalmia, absence of all optic pathways, and other neurological abnormalities. The mutation, Q155X, creates a premature termination codon early in the transcriptional activation domain and is likely to be a null allele. Our data show that mutations in SOX2 can cause not only anophthalmia, but also aplasia of the optic nerve, chiasm and optic tract, as well as modest bilateral sensorineural hearing loss, and global developmental delay, underscoring the importance of SOX2 in early human eye and brain development.

Abnormalities, Multiple↗
PubMed1999

[Neurofibromatosis type 1 in childhood].

Neurofibromatosis 1 is one of the most common genetic disorders in man. Although almost every body system can be involved, it most frequently affects the skin, the nervous system and the skeleton. Major disease features are café-au-lait spots, axillary/inguinal freckling, neurofibromas and Lisch' nodules. The complications are quite variable, making it impossible to predict the clinical course in an individual patient. To summarize the problems associated with this disease we have quantified manifestations and complications in a group of 38 children with neurofibromatosis 1 who were seen at the University Hospital in Trondheim, Norway between 1987 and 1997. The results are based upon the medical records as well as clinical examination. A wide variety of initial symptoms was recorded, but the majority of the children had café-au-lait spots and axillary/inguinal freckling, two of the seven disease features included in the diagnostic criteria given by the National Institutes of Health. The most frequent complications were tumours, with highest incidence of optic pathway gliomas, disturbances of growth and puberty, delayed psychomotor development and learning disabilities. The risk of complications necessitates regular follow-up in a paediatric department. An annual assessment by an ophthalmologist is also recommended, as well as Visual Evoked Potentials/MRI as screening for optic glioma in children under ten years of age.

Adolescent↗
PubMed1997

Optic atrophy and cerebral infarcts caused by methanol intoxication: MRI.

We present the MRI findings of cerebral and optic pathway damage in the acute and subacute stages of methanol intoxication. In the acute stage, CT and MRI showed bilateral haemorrhagic necrosis of the corpus striatum and infarcts in the anterior and middle cerebral arterial territories. MRI in the subacute stage demonstrated atrophy of the optic chiasm and prechiasmatic optic nerves in addition to the cerebral infarcts. The patient survived, with total blindness.

Adult↗
PubMed1980

Pattern of myelination and distribution of neuroglial cells along the developing optic system of the rat and rabbit.

In order to gather information about the factors influencing myelination and neuroglial cell formation in the central nervous system, the development of myelin and neuroglia was investigated along the length of the optic nerve and tract of rats and rabbits. The results of this study revealed complex developmental patterns for both of these processes. Furthermore, the pattern of myelination for the rat is different from that of the rabbit. Myelination of the rat optic pathway exhibits a general rostro-caudal gradient extending from the eye to the lateral geniculate nucleus, whereas a more homogeneous pattern is present in the rabbit. Myelination along the nerves of both species shows many sharp peaks and troughs, especially in the region of the optic canal. Formation of myelin begins at several different sites along the nerve, with the first fibers appearing on both sides of the optic canal. Another small site of myelination develops just in front of the optic chiasm. Myelination of the entire length of an individual axon is not homogeneous but instead it begins at several discrete sites. The number of glial cells along the nerve and tract also fluctuates sharply but their pattern does not precisely parallel that of myelination. A better correlation is obtained by comparing the distribution of axons being myelinated with that of oligodendroglial cells. The complex patterns and the species differences observed in this study indicate that myelination and neuroglial cell development must be regulated by both neuronal and local factors. The data presented here together with other available information suggest that the vascularization of the nerve and the direct effects of hormones upon glial cells are possible factors that contribute to the local variability.

Aging↗
PubMed1977

[Chiasmatic syndrome--clinical value of the visual evoked responses (VER) to the diagnosis (author's transl)].

The VER is compared with that of other neuroophthalmological examinations in 25 patients presenting lesions of the anterior optic pathways (of which 18 were of an expansive nature). The authors believe that visual field plotting and VER are indispensable complementary examinations, giving results which orientate subsequent investigations towards a chiasmatic or prechiasmatic syndrome. In 15 cases of chiasmatic syndrome of tumoral origin (thus in 30 optic nerves), visual fields and VER showed early pathological changes. In originally unilateral forms, VER changes are usually bilateral even when visual field changes are still unilateral. This draws attention to the fact that some process may be injuring either both optic nerves, or the optic chiasma. In cases where the patients are too young, or collaboration is insufficient, to enable visual fields to be plotted, evolution may be studied by VER. In post-surgical follow-up, or during therapy (eg. irradiation), VER recuperation carries a good prognosis. If no VER improvement occurs the expansive process has caused irreparable optic nerve atrophy. Nevertheless, frequent visual field study remains the best diagnostic method of chiasmatic syndromes and their evolution. An earlier diagnosis may be made in the majority of cases by the dual study of visual fields and VER.

Adenoma↗
PubMed1978

Indirect, across-the-midline retinotectal projections and representation of ipsilateral visual field in superior colliculus of the cat.

1. In agreement with previous work, we have found that the ipsilateral visual field is represented in an extensive rostral portion--from one-third to one-half--of the superior colliculus (SC) of the cat. This representation is binocular. The SC representation of the ipsilateral visual field can be mediated both directly, by crossed retinotectal connections originating from temporal hemiretina, and indirectly, by across-the-midline connections relaying visual information from one-half of the brain to contralateral SC. 2. In order to study the indirect, across-the-midline visual input to the SC, we have recorded responses of SC neurons to visual stimuli presented to either the ipsilateral or the contralateral eye of cats with a midsagittal splitting of the optic chiasm. Units driven by the ipsilateral eye, presumably through the direct retinotectal input and/or corticotectal connections from ipsilateral visual cortex, were found throughout the SC, except at its caudal pole, which normally receives fibers from the extreme periphery of the contralateral nasal hemiretina. Units driven by the contralateral eye, undoubtedly through an indirect across-the-midline connection, were found only in the anterior portion of the SC, in which is normally represented the ipsilateral visual field. Receptive fields in both ipsilateral and contralateral eye had properties typical of SC receptive fields in cats with intact optic pathways. 3. All units having a receptive field in the contralateral eye had also a receptive field in the ipsilateral eye; for each of these units, the receptive fields in both eyes invariably abutted the vertical meridian of the visual field. The receptive field in one eye had about the same elevation relative to the horizontal meridian and the same vertical extension as the receptive field in the other eye; the two receptive fields of each binocular unit matched each other at the vertical meridian and formed a combined receptive field straddling the vertical midline of the horopter...

Animals↗
PubMed1990

Quantitative study of the tectally projecting retinal ganglion cells in the adult frog: I. The size of the contralateral and ipsilateral projections.

The proportion of ganglion cells connected to the several central targets of the retinal projection varies in different species. In the frog, the retinotectal projection is clearly the largest branch of the optic pathway and the relative size of the tectally projecting population can be expected to be correspondingly great. However, there have been no studies aimed at quantifying the size of this population and at partitioning its contralateral and ipsilateral components. We injected the tectum with horseradish peroxidase (HRP) dried onto fine needles to count the numbers of retinal ganglion cells labeled by retrograde transport. The retinas were prepared as flat-mounts to facilitate the cell counting. The tecta were injected either unilaterally or bilaterally in mirror-symmetric loci. Specimens included completely normal frogs and frogs which had undergone unilateral optic nerve regeneration, although only normal retinas are presented in the current study. The retrograde transport interval was varied progressively (from 3 to 5 days), and single or multiple injections of HRP were placed singly or as clusters, in order to increment the cell counts toward a level of saturation. Approximately 70.9% of the neurons in the ganglion cell layer could be labeled by this method. Correcting for the presence of displaced amacrine cells, estimated to comprise approximately 16% of the neurons in the ganglion cell layer (Scalia et al., '85, Brain Res. 344:267-280), we calculate that approximately 84.4% of the retinal ganglion cells project contralaterally to the optic tectum. Flat-mounted retinas ipsilateral to unilaterally injected tecta of completely normal frogs were also examined for labeled cells. The results of injections in the rostrolateral, caudomedial, and caudolateral tectum were studied. We found that ipsilaterally labeled cells comprised no more than 2.3% of the overall population of ganglion cells in the ganglion cell layer. The ipsilaterally projecting cells were found in loci which were approximately mirror-symmetric to the regions of maximal cell labeling in the contralateral retinas from the same animals. The ipsilateral population was always displaced toward the periphery of the retina with respect to the contralateral population, regardless of whether the contralateral locus was centered in the temporal, ventronasal, or dorsonasal sector of the retina. Because the ipsilaterally projecting ganglion cells form such a minor population, and because they exist in the monocular as well as the binocular parts of the retina, it seems likely that they may not play a significant role in visual function in the frog.

Afferent Pathways↗
PubMed1991

Neural spread of herpes simplex virus after anterior chamber inoculation.

A genetically engineered herpes simplex virus type 1 (HSV-1, strain RH116) that expresses beta-galactosidase (beta-gal) was used as a marker to trace the route of interocular spread of HSV-1 after anterior chamber (AC) inoculation into BALB/c mice. Because RH116 is thymidine kinase deficient (TK-), the wild-type TK+ KOS strain of HSV-1 was used as a helper virus to complement RH116 during in vivo infection. After coinfection of BALB/c mice with RH116 and KOS in the AC of one eye, beta-gal expression by RH116 was detected in both the eyes and in the central nervous system (CNS). Our results suggest that after AC inoculation into BALB/c mice: (1) virus spreads from the injected eye to the CNS through parasympathetic fibers of the oculomotor nerve that supply the iris and ciliary body; (2) virus spread in the CNS is limited primarily to nuclei of the visual system and the suprachiasmatic area of the hypothalamus; and (3) virus is transmitted from the CNS to the retina of the contralateral eye by retrograde axonal transport through the optic nerve along the endocrine-optic pathway between the retina and the suprachiasmatic nucleus of the hypothalamus.

Animals↗
PubMed1998

Bony orbital morphology in neurofibromatosis type 1 (NF1).

We retrospectively compared patients with NF1 with and without optic pathway gliomas (OPG) to determine the incidence and range of orbital developmental abnormalities and compared the incidence of OPG in African-Americans and whites. From cranial MR scans, we manually measured 14 orbital dimensions, compared them to published standards of Waitzman et al, calculated orbital volumes, and determined the presence or absence of volumetric symmetry (delta v) (delta v < or = 3 cm3 was considered to be symmetrical). We compared the results of orbital configurational assessment between patients with (group I) and those without OPG (group II). The study population comprised 58 patients, 24 boys, 18 African-American, and one Hispanic. Median age at imaging was 7 years (range 0.5-25.5 years). Fifty-eight percent had conformational abnormalities, 16 of whom had more than one abnormality (28%), the most frequent being increased intertemporal distance (n=10), increased lateral orbital distance (n=8), increased medial wall length (n=6), and decreased medial wall length (n=6). The increased intertemporal and lateral orbital distances may contribute to the appearance of hypertelorism. Only two patients had sphenoid wing hypoplasia. We found a high incidence of orbital dimensional abnormalities in the total population but more often saw multiple abnormalities in patients with OPG. However, no pattern of configurational abnormality emerged. OPG is less frequent in African-Americans. Orbital volumetric disparity seems to be independent of the presence of OPG.

Adolescent↗
PubMed1999

Optic gliomas.

Primary tumors of the optic nerve are uncommon. The most common are optic nerve gliomas (ONGs), which account for 66% of all primary optic nerve tumors. Seventy-five percent of gliomas are diagnosed in the first decade of life, and 90% are diagnosed in the first two decades. This article discusses the anatomy and imaging of the optic pathway and the clinical manifestations of ONGs.

Adult↗