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At least 757 records · Page 42Linked to original sources
PubMed1996

Usefulness of screening investigations in neurofibromatosis type 1. A study of 152 patients.

OBJECTIVE: To evaluate the usefulness of screening investigations in patients with neurofibromatosis type 1 (NF1). DESIGN: Clinical and screening data were retrospectively collected from a case series of patients with NF1. Screening investigations included an opthalmologic consultation, chest x-ray film, abdominal ultrasonography, cerebral imaging, and analysis of urinary catecholamine levels. Clinical features and complications of patients with NF1 were compared with those of the Neurofibromatoses Institute Clinical Research Program and of the Southeast Wales study patients. SETTING: Ambulatory care in a referral center. PATIENTS: Between 1988 and 1992, 152 patients classified as having NF1 according to the criteria of the National Institutes of Health Consensus Development Conference Statement were studied. MAIN OUTCOME MEASURE: Complications requiring therapeutic action detected using screening investigations vs clinical examination. RESULTS: Systemic chest x-ray films were taken of 134 patients, and intrathoracic nodules thought to be neurofibromas were discovered in 2 patients. Ninety-three asymptomatic patients had cerebral imaging performed, which showed optic pathway glioma in 12 patients. Abdominal ultrasonography was performed on 62 asymptomatic patients, results of which showed internal neurofibromas in 4 patients. In 2 of these patients, abdominal surgery was performed. Eighty-three patients without hypertension had 24-hour urinary specific catecholamine levels analyzed, which were within the normal range. Clinical features and complications were not different from other large clinical studies. Nearly 400 systematic investigations were performed without clinical orientation, detecting 21 abnormalities. In only 2 cases, these discoveries led to therapeutic action. On the other hand, 22 complications requiring treatment were detected by clinical examination. CONCLUSION: Clinical follow-up seems to be more beneficial than systematic investigations in patients with NF1.

Adolescent↗
PubMed1996

[Visual and central oculomotor disorders in patients with acquired immunodeficiency syndrome].

A clinical evaluation of visual and central oculomotor defects are presented in a series of 56 patients who were HIV carriers, of whom 47 fulfilled criteria for AIDS. Changes were detected in 22% of the asymptomatic patients (2/9), in 36% of the AIDS patients with no neurological complications and in 93% (15/16) of the AIDS patients with neurological involvement. Some changes were seen in 55% of the patients with AIDS. The commonest defects were alterations of saccadic movements and visual pursuit (35% respectively) and of opticokinetic nystagmus (28%). Only one homonymous visual defect was found. No brain stem syndromes were seen, except for one case of bilateral internuclear ophthalmoplegia. The commonest neurological complications were toxoplasmosis, the AIDS dementia complex (ADC) and multifocal leukoencephalopathy (MLP). Neuro-ophthalmological changes are described, in the literature, in 2-12%. Central oculomotor disorders, including supranuclear, nuclear and internuclear ophthalmoplegias are frequent and probably underestimated. Nystagmus is a common sign and there are isolated descriptions of flutter, opsoclonus and ocular dipping. The causes of visual and oculomotor changes reflect the incidence of parenchymatous neurological complications of AIDS. MLP is the commonest cause of change in the retrogeniculate optic pathways. Oculographic studies show changes in saccadic movements and ocular pursuit and signs of unstable visual fixation. These changes are seen in all ADC patients, in a large proportion of those without dementia and also in asymptomatic carriers, suggesting that oculography may be useful for prognosis.

AIDS Dementia Complex↗
PubMed1996

Signal transduction in vertebrate growth cones navigating in vivo.

Navigating growth cones need signal transduction machinery to amplify and transmit the effects of extracellular signals throughout the growth cone. In culture, many drugs that affect second messengers are known to modulate neurite extension (with different effects on different neurons), and gradients of calcium influx and cyclic nucleotide analogs can cause growth cones to turn. However, it is not clear which of these responses are physiologically relevant, as axons grow through much more complex environments in vivo. The "exposed brain" preparation in Xenopus embryos provides an experimentally tractable system in which it is possible to study growth, pathfinding, and target recognition of retinal growth cones in vivo, while pharmacologically manipulating their signal transduction systems. These growth cones can also be easily studied in explant culture. We describe preliminary results of parallel in vivo and in vitro experiments using an array of drugs that perturb transduction molecules. Surprisingly, calcium ionophores and cyclic nucleotide analogs have no significant effect on retinal axon growth or pathfinding. Several agents including herbimycin A, ML-7, mastoparan, and RHC80267 inhibit retinal axon growth, both in vivo and in vitro, suggesting that tyrosine kinases, myosin, heterotrimeric G-proteins, and diacylglycerol lipase are important for retinal growth cones navigating in the optic pathway.

Animals↗
PubMed1997

Triton-soluble phosphovariants of the heavy neurofilament subunit in developing and mature mouse central nervous system.

The low abundance of soluble neurofilament (NF) subunits in mature axons has suggested that newly synthesized NF proteins rapidly assemble into highly stable polymers and associate with the Triton X-100-insoluble cytoskeleton. The dynamic nature of these subunit associations in vivo remains unresolved, and the applicability of this assembly model to NFs in other neuronal compartments or to developing neurons is unknown. Here, we report that a unique pool of Triton X-100-soluble, extensively phosphorylated, high molecular weight NF subunits (NF-H, or H-200) are abundantly expressed in the mouse CNS during early postnatal development and persist in the perikaryal compartment of some mature neurons. Triton-soluble H-200 subunits appeared at postnatal day 14 (P14) and remained high through P60, beyond which the percentage declined to marginal levels by P120. Medium and low molecular weight NF (NF-M and NF-L, respectively) were at all times only detectable within the cytoskeleton. Comparison of soluble and cytoskeleton-associated H-200 immunoreactivity indicated that certain phosphorylation-dependent epitopes were confined to the cytoskeleton. Pulse-chase radiolabeling analyses in optic pathway demonstrated that some Triton-soluble NF-H subunits are extensively phosphorylated within retinal perikarya before they are incorporated into Triton-insoluble structures. These findings indicate that the assembly behaviors of NF-H differ substantially from those of NF-M and NF-L, and that the interaction of NF-H with NFs may be more dynamic than is generally recognized, especially during brain development and within specific compartments of mature neurons.

Animals↗
PubMed1997

Excimer laser correction of astigmatism using erodible masks.

PURPOSE: The latest development in the erodible mask technology is an excimer laser containing the mask in the laser optical pathway. This paper reports the results of the first human series of consecutive treatments performed for the correction of compound myopic astigmatism. METHODS: We have treated 83 eyes. Spherical equivalent attempted correction ranged between -1.75 and -11.75 D (mean -7.07 +/- 2.45 D), astigmatic attempted correction ranged between -1.00 and -5.00 D (mean -2.42 +/- 1.02 D). The sphere correction was made by diaphragm using a multi-zone software with three ablation zones: 100% of the total attempted correction for the central 5.0 mm zone, 70% for the second 6.0 mm zone, 30% for the outer 6.5 mm zone. Cylinder correction was made sequentially after myopic correction using the appropriate mask. RESULTS: One month after treatment, mean refractive error was +1.07 +/- 1.24 D (range +4.50/-1.75 D) for spherical equivalent, and -0.49 +/- 0.57 D (range +0.75/-2.00 D) for astigmatism. Forty-eight eyes (57.8%) had uncorrected visual acuity of 20/40 or better. At six months, mean refractive error was +0.42 +/- 0.97 D (range +3.75/-1.00 D) for spherical equivalent, and -0.44 +/- 0.51 D (range +0.25/-3.00 D) for astigmatism. Vector analysis showed that 57 eyes (68.7%) had 5 or less degrees rotation. Seventy-two (86.7%) and 54 eyes (65.1%) had uncorrected visual acuity equal or better than 20.40 and 20/25 respectively. One eye (1.2%) showed a best corrected visual acuity loss of more than one line, but 8 eyes (9.6%) had a gain of more than one line. One-year results on a smaller series (33 eyes) overlap the six-month results. CONCLUSIONS: The mask in-the-rail excimer laser delivery system appears to be effective and predictable in the correction of compound myopic astigmatism. We observed no significant regression of the astigmatic correction over time. Longer follow-up on larger series is necessary to draw final conclusions.

Adolescent↗
PubMed1983

Pathways of Xenopus optic fibres regenerating from normal and compound eyes under various conditions.

We have used Horseradish peroxidase to investigate the pathways taken by Xenopus optic fibres regenerating from normal and electrophysiologically-confirmed compound eyes to the optic tectum. Optic fibres, when sectioned near the chiasma, regenerate up both sides of the diencephalon to both tecta. We have therefore been able, by using animals in which one eye had or had not been removed at early embryonic stages, to look at the behaviour of regenerating axons in three different situations: (1) regeneration to the contralateral tectum, previously innervated by the sectioned fibres; (2) regeneration to a "virgin' ipsilateral tectum, never before innervated by optic fibres; and (3) regeneration to an ipsilateral tectum already innervated by fibres from a normal eye. From the chiasma to the tectodiencephalic junction regenerating fibres behave similarly in all three situations, following roughly the course of the normal optic tract, but running in a rather disorganised way, with frequent crossing over of fibres. However fibres of nasal retinal origin (from an NN eye) spread to occupy a much larger area of the side of the diencephalon than those of temporal origin (from a TT eye). From the tectodiencephalic junction to the tectal termination of the fibres there are differences between the three situations investigated; fibres regenerating to a 'virgin' ipsilateral, or to a denervated contralateral tectum, tend to grow straight onto the tectum, instead of being channelled into lateral or medial brachium as uncut fibres tend to be. There is however, the remains of a brachial organisation, and of differential selection of these brachia by fibres from the different types of compound eye, this being well seen on "virgin' tecta. Fibres regenerating to an ipsilateral innervated tectum behave very differently. As they reach the tectodiencephalic junction they suddenly start to grow in a less disorganised way, and are channelled into well defined brachia. If from a compound eye, these fibres terminate on only that part of the tectum innervated by fibres from the corresponding part of the normal eye. Thus fibres from a VV eye and those from the ventral half of the normal eye all terminate on medial tectum; fibres from an NN eye, and those from the nasal half of the normal eye all terminate in caudal tectum; and temporal fibres from both normal and TT eyes terminate in rostral tectum.

Animals↗
PubMed1986

A second ascending visual pathway from the optic tectum to the telencephalon in the pigeon (Columba livia).

Previous studies in the pigeon (Karten and Revzin: Brain Res. 2:368-377, '66; Karten and Hodos: J. Comp. Neurol. 140:35-52, '70) have described an ascending tectofugal visual pathway from the optic tectum to the ectostriatum by way of the nucleus rotundus of the thalamus. This present study used anterograde autoradiographic and retrograde horseradish peroxidase pathway-tracing techniques to investigate another ascending tectofugal pathway in the pigeon. Injections of 3H-proline/leucine confirmed a previous report that the optic tectum projects to the nucleus dorsolateralis posterior of the thalamus (DLP). This projection is predominantly ipsilateral and is confined to a large-celled caudal region of the nucleus (DLPc); the rostral region of the nucleus (DLPr) is not tectorecipient. Injections of horseradish peroxidase in DLPc labeled cells predominantly ipsilaterally in layers 8-15 of the optic tectum. Injections of 3H-proline/leucine placed in the DLPc labeled a discrete region of the ipsilateral telencephalon. Similar injections of DLPr labeled a contiguous, but more rostral, region of the neostriatum intermedium. Nissl- and silver-stained material indicated that the region in which DLP terminates is cytoarchitecturally distinct from ventromedial ectostriatal core and belt. Injections of horseradish peroxidase at various locations in the neostriatal DLP terminal field demonstrated a rostrocaudal ordering of the DLP projection upon the neostriatum intermedium. Single-unit recording demonstrated that cells in DLPc respond to whole-field illumination at the same latency as cells in the nucleus rotundus, indicating that the tecto-DLPc-neostriatal pathway transmits visual information to the telencephalon. We suggest that comparable pathways may exist in both reptiles and mammals.

Animals↗
PubMed1986

Optic fibers follow aberrant pathways from rotated eyes in Xenopus laevis.

The rotated eye paradigm has been a major experimental test of the neuronal specificity model for the development of ordered retinotectal connections in amphibians. In most studies, however, no optic fiber pathways were traced from rotated eyes and correlated with visuotectal projections. As an initial approach to this question, optic fibers from eyes rotated at different embryonic stages were traced with 3H-proline autoradiography. Three experimental series were prepared: in situ eye rotations, isochronic transplants of eyes rotated between embryos at the same stage, and heterochronic transplants of eyes rotated between embryos at different stages. Single or multiple optic fiber pathways developing from rotated eyes are identified by their sites of entry and trajectory in the brain. These include a normal chiasmatic (CH) pathway, and three aberrant pathways, identified as trigeminal (TR), diencephalic (DI), and oculomotor (OC). The latter three enter the brain ipsilaterally, some crossing contralaterally via commissural pathways. Depending on stage and type of operation, TR pathways develop in 50-100% of the animals, while CH pathways are more common after rotation at stage 21/22. The surgical procedure affects the initial trajectory of fibers from the retina, perturbs guidance cues in the surrounding orbit, and determines the patterns of optic pathways that develop. In most cases, optic fibers follow motor (oculomotor) or sensory (trigeminal) nerves, usually the first fibers encountered near the orbit by axonal pioneers exiting the retina. Evidently, optic fibers exhibit no pathway selectivity; any axon serves as a guidance cue. Tecta are innervated in about 50% of the cases, usually by fibers following abnormal trajectories from CH and OC pathways. The results suggest that the development of ordered visuotectal projections from rotated eyes is a complex process that may be independent of the trajectory of fiber arrival. Unless pathways and visuotectal maps are directly compared in each animal, however, the question remains open because we still do not know which anomalous pathways, if any, correlate with ordered projections.

Animals↗
PubMedDate not supplied

[Architecture of the pathways and primary optical centers in trout (Salmo irideus Gibb.)].

The retinal projections of the Trout were examined on fifteen adult specimens (eighteen months) unilaterally enucleated. After a post-operative survival period of six to 31 days, the degenerating fibers were stained with Fink-Heimer technique. The optic tract is entirely crossed. At the rostral end of the thalamus a first fascicle diverges which runs to aventral thalamic center and to a dorsal thalamic center. The latter extends caudally as a pretectal center. The second fascicle is a retinogeniculo-tectal pathway which borders the geniculate body and enters the external tectal layer. The corpus geniculatum is large, well laminated and contains terminal degeneration. The main part of the optic tract includes three fascicles. Each of them sends fibers to all three tectal layers.

Animals↗
PubMed2003

Anatomical organization of retinotopic motion-sensitive pathways in the optic lobes of flies.

Anatomical methods have identified conserved neuronal morphologies and synaptic relationships among small-field retinotopic neurons in insect optic lobes. These conserved cell shapes occur across many species of dipteran insects and are also shared by Lepidoptera and Hymenoptera. The suggestion that such conserved neurons should participate in motion computing circuits finds support from intracellular recordings as well as older studies that used radioactive deoxyglucose labeling to reveal strata with motion-specific activity in an achromatic neuropil called the lobula plate. While intracellular recordings provide detailed information about the motion-sensitive or motion-selective responses of identified neurons, a full understanding of how arrangements of identified neurons compute and integrate information about visual motion will come from a multidisciplinary approach that includes morphological circuit analysis, the use of genetic mutants that exhibit specific deficits in motion processing, and biomimetic models. The latter must be based on the organization and connections of real neurons, yet provide output properties similar to those of more traditional theoretical models based on behavioral observations that date from the 1950s. Microsc. Res. Tech. 62:132-150, 2003.

Animals↗
PubMed1981

Anatomical evidence for the influence of degenerating pathways on regenerating optic fibers following surgical manipulations in the visual system of the goldfish.

We have used [3H]proline radioautography to trace regenerating optic fibers in the goldfish following: (1) the removal of the right tectal lobe and the right eye, and (2) the removal of both tectal lobes. Our results indicate that following the removal of the right tectal lobe and the right eye, both the denervated tectal efferent pathways, and the denervated visual pathways and terminal zones of the enucleated eye were penetrated by the regenerating optic fibers. In addition, following bilateral lobectomy, the denervated tectal efferent pathways were bilaterally penetrated by the regenerating fibers. Since, in both types of operations, these denervated pathways and terminal zones should undergo degeneration, our results support the suggestion that the presence of degenerating axonal debris and proliferating glia may play an important role in guiding regenerating optic fibers in the visual system of the goldfish.

Animals↗
PubMed1997

Calcitonin gene-related peptide immunoreactivity selectively labels accessory optic nuclei and pathways of the rat visual system.

The present study shows the distribution of calcitonin gene-related peptide (CGRP)-immunolabeled neuronal somata and fibers in the accessory optic system of adult rats. CGRP-immunoreactive cell bodies were small to medium-sized and mostly fusiform or oval-shaped. Both immunolabeled somata and fibers were found in the dorsal and lateral terminal nuclei as well as in the interstitial nucleus of the superior fasciculus (posterior fibers); whereas only immunoreactive fibers were found in the ventral division of the medial terminal nucleus, particularly its rostral portion. These results indicate that CGRP-containing neurons are present in all nuclear components of the accessory optic system and suggest that this neuropeptide may play a neuromodulative role in eye movements.

Animals↗
PubMed1991

[Disorders of the afferent visual pathway in HIV infection. 1. Optic nerve and 2. Visual pathways/visual cortex].

Up to now little involvement of the afferent visual pathway (optic nerve and optic radiation and visual cortex) in HIV infection has been apparent. These results are based on our prospective investigations of 538 HIV-infected individuals, among them 261 patients with full-blown AIDS carried out by the same examiner over a 6-year period (1984-1990). Diseases of the optic nerve were observed in 22/261 (8.4%) of Aids patients but in only 1/227 (0.4%) of patients with earlier stages of HIV infection. Optic neuritis was the most common disease (in 14/261 = 5.4% of Aids patients), for the most part occurring in the course of CMV (cytomegalovirus) retinitis. For this form the prognosis was primarily good under virustatic therapy with ganciclovir in contrast to primary CMC papillitis. Furthermore, a few cases of optic perineuritis, optic neuropathy in basal meningitis, ischemic optic neuropathy and papilloedema with increased intracranial pressure were observed, most of them caused by opportunistic infections of the central nervous system. In single cases the HIV might hypothetically have played a role in the etiology. Visual impairment of the patients varied from subtle disturbances to blindness. Often optic atrophy resulted. Homonymous hemianopsia was the principal sign in diseases of the visual pathway between the lateral geniculate body and the visual cortex (in 10/261 = 3.8% of Aids patients). This symptom resulted from cerebral toxoplasmosis in 7 cases, progressive multifocal leukoencepalopathy (PML) in 2 cases and primary intracerebral malignant lymphoma in 1 case. The visual fields and neuroradiological findings are demonstrated. In 3 cases the homonymous hemianopsia was the first clinical appearance of Aids. Involvement of the afferent visual pathway in HIV infection may be a cause of blindness or visual disturbances despite normal findings on examination of the eyes themselves.

Fluorescein Angiography↗
PubMed1992

Anatomical pathways from the optic tectum to the spinal cord subserving orienting movements in the barn owl.

Electrical stimulation of the optic tectum in many vertebrate species elicits eye, head or body orienting movements in the direction of the receptive field location recorded at the site of stimulation; in the barn owl, tectal stimulation produces short latency saccadic head movements (du Lac and Knudsen 1990). However, the barn owl, like other avians, lacks a direct projection from the tectum to the spinal cord, implying that less direct connections underlie tectally mediated head movements. In order to determine the pathways by which the tectum gains access to spinal cord circuitry, we searched for overlap regions between tectal efferent projections and the locations of cells afferent to the spinal cord. Tectal efferent pathways and terminal fields were revealed by anterograde labeling using horseradish peroxidase (HRP) or tritiated amino acids injected into the optic tectum. Cells afferent to the spinal cord were identified by means of retrograde labeling using HRP, rhodamine, or rhodamine-coupled latex beads injected into the cervical spinal cord. A comparison of results from the anterograde and retrograde labeling experiments demonstrated several areas of overlap. All of the cell groups that both received heavy tectal input and contained a high proportion of cells projecting to the spinal cord were located in the medial half of the midbrain and rhombencephalic tegmentum, and included the red nucleus, the interstitial nucleus of Cajal, the medial reticular formation, the nucleus reticularis pontis giganto-cellularis, and the nucleus reticularis pontis oralis. All of these cell groups receive their tectal input from the medial efferent pathway, one of three major output pathways from the tectum. The other two output pathways (the rostral and the caudal) project to regions containing no more than a few scattered cells that are afferent to the spinal cord. Based on these data and on the functions of homologous cell groups in other vertebrates, we hypothesize that the medial efferent pathway and its brainstem target nuclei are primarily responsible for tectally mediated orienting head movements in the barn owl.

Animals↗
PubMed2006

Optical recording of vagal pathway formation in the embryonic brainstem.

Multiple-site optical recording with a fast voltage-sensitive dye, absorption dye NK2761, was used to study the developmental organization of functional synaptic networks in the vagal pathway. Glutamatergic excitatory postsynaptic potentials (EPSPs) evoked by vagus nerve stimulation was first detected from the nucleus of the tractus solitarius (NTS) at embryonic day 7 (E7) in chick embryos and E15 in rat embryos, when morphological differentiation of pre- and postsynaptic neurons is incomplete. When extracellular Mg2+ was removed, small EPSPs were elicited at E6 in chick embryos and E14 in rat embryos. These results suggest that synaptic function mediated by N-methyl-D-aspartate (NMDA) receptors is latently generated 1 day before the expression of glutamatergic EPSP. Functional synapses related to the glossophyaryngeal nerve appear to be generated at the same time as the vagus nerve, but their spatial distribution was different from that of the vagus nerve. We further investigated the development of second synaptic pathways from the NTS to higher centers, and found that neuronal circuits from the NTS are already generated when the primary afferents form functional synapses with NTS neurons.

Animals↗
PubMed2004

Responses and signaling pathways in human optic nerve head astrocytes exposed to hydrostatic pressure in vitro.

In this study, we examined the effects of mechanical stress induced by elevated hydrostatic pressure (HP) on the migration of human optic nerve head (ONH) astrocytes, using an in vitro model that follows repopulation of a cell-free area (CFA) created on a monolayer of cultured astrocytes. alpha-Tubulin staining detected phenotypic changes in astrocytes exposed to HP. The influence of proliferation in closure of the CFA was determined by incorporation of BrdU under 1.5-cm H2O, control pressure (CP), and 10-cm H2O HP with or without 5-fluorouracil. Under control and experimental conditions, closure of the CFA occurred mostly by migration and less by proliferation. Exposure to 10-cm H2O HP induced faster closure of the CFA at 1, 3, and 5 days. The signaling pathways involved in responses to HP were determined using genistein, tyrphostin A25, AG1478, and AG1295, inhibitors of receptor tyrosine kinases; wortmannin and LY294002, inhibitors of phosphatidyl inositol 3-kinase (PI-3K); and SC58236, an inhibitor of inducible cyclooxygenase-2 (COX2). Genistein and tyrphostin A25 blocked HP-induced migration at 1, 3, and 5 days, but did not affect closure of the CFA under CP. AG1478 and AG1295 blocked HP-induced migration and partially inhibit closure of the CFA under CP. LY294002 blocked HP-induced migration. SC58236 markedly inhibited closure of the CFA under CP by inhibiting COX2 activity. Exposure to HP, a physical stress, induced faster closure of the CFA via activation of members of the epidermal growth factor receptor (EGFR) family and PI-3K pathways. Under CP, closure of the CFA in response to denudation, a form of injury, is due to activation of COX2 in ONH astrocytes.

Adolescent↗