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PubMed1991

Age-dependent extrasynaptic modulation of axonal conduction by exogenous and endogenous GABA in the rat optic nerve.

To ascertain whether endogenous gamma-aminobutyric acid (GABA) exists and exerts physiological effects in the optic nerve, we compared the effects of GABA and related drugs on the neonatal (1 to 22 days of age) and adult (greater than 6 months) rat optic nerve in vitro. GABA (10(-4)-10(-3) M) reversibly depressed the amplitude and increased the latency of compound action potentials in the neonatal optic nerve. In the adult optic nerve, GABA (10(-4)-10(-3) M) had no significant effect on the compound action potential. The GABA-A receptor agonist, isoguvacine (10(-4)-10(-3) M), mimicked these GABA effects on the neonate and adult optic nerve. Lower concentrations (10(-5) M) of GABA increased excitability of the neonatal optic nerve but produced no discernible effects on the adult optic nerve. The GABA-uptake inhibitor, nipecotic acid (10(-3) M), mimicked the effects of GABA (10(-5) M) on the neonatal optic nerve. The GABA-A receptor blockers, picrotoxin and bicuculline (10(-6)-10(-3) M), decreased the latency of compound action potentials in the neonatal optic nerve. Membrane potential recordings indicate that while GABA (10(-5)-10(-3) M) depolarized the neonatal optic nerve dose-dependently, picrotoxin hyperpolarized the axons. In the adult optic nerve, neither GABA-uptake inhibitors nor GABA-A receptor blockers had significant effects on the compound action potential. These results suggest that functional GABA-A receptors and GABA are present in the neonatal rat optic nerve and depolarize axons under physiological conditions. However, this does not appear to be the case in the adult optic nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed2006

Neuroprotective effects of brimonidine treatment in a rodent model of ischemic optic neuropathy.

Ischemic optic neuropathy (ION) is a common disorder caused by disruption of the arterial blood supply to the optic nerve. It can result in significant loss of visual acuity and/or visual field. An ischemic optic nerve injury was produced in rats by intravenous injection of Rose Bengal dye followed by argon green laser application to the retinal arteries overlying the optic nerve, causing a coagulopathy within the blood vessels and disruption of optic nerve and retinal perfusion. The effect of brimonidine tartrate eye drops on survival of retinal ganglion cell axons in this experimental paradigm was studied. One eye was treated and the contralateral eye served as a control. Four groups of animals were used for this study. Group 1 received 7 days of treatment with 0.15% brimonidine tartrate eye drops twice a day prior to the ischemic injury. Group 2 animals received 0.15% brimonidine tartrate eye drops twice a day for 14 days after photocoagulation injury. Animal groups 3 and 4 received eye drops of 0.9% NaCl twice a day either daily for 7 days before injury or daily for 14 days, respectively. All rats were sacrificed 5 months after the injury to ascertain long-term optic axon survival. Coagulopathy-induced optic nerve ischemia resulted in a 71% loss of optic axons. Treatment with brimonidine daily for the 7 days prior to the injury resulted in a greater survival of optic axons, with only a 56.1% loss compared to control. Brimonidine treatment every day for 14 days after the ischemic injury did not result in a significant rescue of optic axons compared to injury alone. In summary, the application of brimonidine eye drops for one week prior to an ischemic injury resulted in a statistically significant increase in survival of optic axons within the injured optic nerves. Brimonidine treatment of the eye after the ischemic injury did not result in axon rescue, and axon loss was similar to the injured optic nerves treated with saline only. These results suggest that brimonidine may have potential use for prevention of ION in at-risk patients.

Adrenergic alpha-Agonists↗
PubMed2006

Retinal ganglion cell damage induced by spontaneous autoimmune optic neuritis in MOG-specific TCR transgenic mice.

Multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) are marked by inflammatory demyelinating lesions throughout the central nervous system, including optic nerve. Neuronal loss also occurs in EAE, including retinal ganglion cell (RGC) loss in eyes with optic neuritis, but the finding of RGC loss in relation to optic nerve inflammation differs in different EAE settings. Recently, Myelin oligodendrocyte glycoprotein (MOG)-specific TCR transgenic mice were found to develop spontaneous isolated optic neuritis in the absence of EAE. In the current study, the relationship of inflammation to retinal ganglion cell (RGC) loss during isolated optic neuritis is examined. RGCs of MOG-specific TCR transgenic mice were labeled with Flourogold and then treated with pertussis toxin (PT) or observed untreated. At various time points, RGCs were counted, retinas were TUNEL labeled, and optic nerves were examined for inflammatory cell infiltrates. 29% of untreated MOG-specific TCR transgenic mice developed periocular inflammation by 4 months of age, and 32% of optic nerves of TCR transgenic mice had histological lesions in the optic nerve. Incidence of histological optic neuritis was 20% at day 8 following injection of PT and increased to 48% by day 12, and 68% by day 16. In contrast, no RGC loss or TUNEL staining was detected in eyes with optic neuritis until day 12 in the mice injected with PT. A 28% reduction in RGC numbers at day 12 increased to 39% by day 16, and RGC loss of eyes with severe or massive inflammation was significantly higher than that of eyes with mild or moderate inflammation. No RGC loss occurred in TCR transgenic mouse eyes without optic neuritis. The fact that inflammation precedes RGC loss suggests that neuronal loss during optic neuritis occurs secondary to the inflammatory process in isolated optic neuritis.

Animals↗
PubMed2007

Optic nerve invasion of uveal melanoma.

The aim of the study was to identify the histopathological characteristics associated with the invasion of the optic nerve of uveal melanoma and to evaluate the association between invasion of the optic nerve and survival. In order to achieve this, all uveal melanomas with optic nerve invasion in Denmark between 1942 and 2001 were reviewed (n=157). Histopathological characteristics and depth of optic nerve invasion were recorded. The material was compared with a control material from the same period consisting of 85 cases randomly drawn from all choroidal/ciliary body melanomas without optic nerve invasion. Prelaminar/laminar optic nerve invasion was in multivariate analysis associated with focal retinal invasion, neovascularization of the chamber angle, and scleral invasion. Postlaminar invasion was further associated with non-spindle cell type and rupture of the inner limiting membrane of the retina. The optic nerve was invaded in four different ways: 1) by tumor extension from the neuroretina through the lamina cribrosa; 2) by direct extension into the optic nerve head between Bruch's membrane and the border tissue of Elschnig; 3) by direct invasion through the border tissue of Elschnig; and 4) in one case a tumor spread along the inner limiting membrane to the optic nerve through the lamina cribrosa. Invasion of the optic nerve had no impact on all-cause mortality or melanoma-related mortality in multivariate analyses. The majority of melanomas invading the optic nerve are large juxtapapillary tumors invading the optic nerve because of simple proximity to the nerve. A neurotropic subtype invades the optic nerve and retina in a diffuse fashion unrelated to tumor size or location.

Adult↗
PubMed2006

Optic disc size in a population based study in northern China: the Beijing Eye Study.

AIM: To determine the optic disc size in the adult Chinese population in an urban and a rural region of Beijing. METHODS: The population based, cross sectional cohort study included 4439 subjects out of 5324 subjects invited to participate (response rate 83.4%). It was divided into a rural part (1973 (44.4%) subjects) and an urban part (2466 (55.6%) subjects). Mean age was 56.2 (SD 10.6) years (range 40-101 years). Colour optic disc photographs were morphometrically examined. Main outcome measure was optic disc area. RESULTS: Optic disc photographs were available for 4027 (90.7%) subjects. Mean optic disc area measured 2.65 (0.57) mm2 (range 1.03 mm2-7.75 mm2). Optic disc area was significantly (p<0.001) correlated with myopic refractive error, with a steep decrease in optic disc area from high myopia to the mid-range of refractive error, a slightly horizontal course in the refractive error range between -8 dioptres and +4 dioptres, and a further decrease in optic disc area towards higher hyperopia. Optic disc area was not related to age (p = 0.14) or sex (p = 0.93) (optic disc area, males: 2.65 (0.56) mm2 versus females: 2.65 (0.57) mm2). "Microdiscs" may be defined as smaller than 1.51 mm2, and "macrodiscs" as larger than 3.79 mm2. CONCLUSIONS: Compared with data of preceding studies, mean optic disc size is larger in Chinese people than in white people. In Chinese people highly hyperopic eyes have significantly smaller optic discs, and highly myopic eyes have significantly larger optic discs than emmetropic eyes.

Adult↗
PubMed2004

White matter fiber dissection of the optic radiations of the temporal lobe and implications for surgical approaches to the temporal horn.

OBJECT: The aim of this anatomical study was to define more fully the three-dimensional (3D) relationships between the optic radiations and the temporal horn and superficial anatomy of the temporal lobe by using the Klingler white matter fiber dissection technique. These findings were correlated with established surgical trajectories to the temporal horn. Such surgical trajectories have implications for amygdalohippocampectomy and other procedures that involve entering the temporal horn for the resection of tumors or vascular lesions. METHODS: Ten human cadaveric hemispheres were prepared with several cycles of freezing and thawing by using a modification of the method described by Klingler. Wooden spatulas were used to strip away the deeper layers of white matter progressively in a lateromedial direction, and various association, projection, and commissural fibers were demonstrated. As the dissection progressed, photographs of each progressive layer were obtained. Special attention was given to the optic radiation and to the sagittal stratum of which the optic radiation is a part. The trajectories of fibers in the optic radiation were specifically studied in relation to the lateral, medial, superior, and inferior walls of the temporal horn as well as to the superficial anatomy of the temporal lobe. In three of the hemispheres coronal sections were made so that the relationship between the optic radiation and the temporal horn could be studied more fully. In all 10 hemispheres that were dissected the following observations were made. 1) The optic radiation covered the entire lateral aspect of the temporal horn as it extends to the occipital horn. 2) The anterior tip of the temporal horn was covered by the anterior optic radiation along its lateral half. 3) The entire medial wall of the temporal horn was free from optic radiation fibers, except at the level at which these fibers arise from the lateral geniculate body to ascend over the roof of the temporal horn. 4) The superior wall of the temporal horn was covered by optic radiation fibers. 5) The entire inferior wall of the temporal horn was free from optic radiation fibers anterior to the level of the lateral geniculate body. CONCLUSIONS: Fiber dissections of the temporal lobe and horn demonstrated the complex 3D relationships between the optic radiations and the temporal horn and superficial anatomy of the temporal lobe. Based on the results of this study, the authors define two anatomical surgical trajectories to the temporal horn that would avoid the optic radiations. The first of these involves a transsylvian anterior medial approach and the second a pure inferior trajectory through a fusiform gyrus. Lateral approaches to the temporal horn through the superior and middle gyri, based on the authors' findings, would traverse the optic radiations.

Amygdala↗
PubMed2000

[CT anatomic measurement of the optic canal and its clinical significance].

OBJECTIVE: To probe into the normal anatomy of the optic canal and its clinical significance. METHODS: The optic canals of 200 normal subjects were examined by thin layer CT scan in axial nd coronal positions. The distance and anatomic relationship with circumferentral structure were measured. RESULTS: In average: (1) The transverse diameter of the optic canal was (3.57 +/- 0.61) mm, the longitudinal diameter was (4.82 +/- 0.38) mm, the length of the inner wall was (12.62 +/- 2.59) mm, the length of the outer wall was (10.18 +/- 2.19) mm, and the length of the optic canal was (11.46 +/- 2.35) mm. The angle between optic canal and the middle line of the skull was 34.34 degrees +/- 6.48 degrees, the angle between optic canal and the intraorbital optic was 10.69 degrees +/- 6.48 degrees. The thickness of the inner wall was (0.68 +/- 0.46) mm. It showed no significant difference between the two sides of the optic canal in diameters(P > 0.05). (2) The optic canal, the superior orbital fissure and the inferior orbital fissure were respectively shown as track, crack and gorge type in CT axial pictures, while in the coronal pictures, they were respectively shown as butterfly eyes, horizontal fissure and vertical fissure type. (3) The relationship of the posterior ethmoid sinus and the optic canal was: anterocanal(42.00%), semicanal(27.5%), whole-canal(18.75%), sella turcica(9.75%) and circumcanal(2.00%). (4) The relationship of the position of the sphenoidal sinus and the optic canal was: I degree sphenoidal sinus(20%), II degree (63%) and III degree (17%). (5) The incidence of the bony defect of the inner optic canal wall was 25.5%. The range of the defect was (5.07 +/- 2.52) mm. CONCLUSION: It's a reliable way to show the relation of the optic canal and circumcanal by CT, and it is of important value in operation.

Adolescent↗
PubMed2006

[A binding study of the gross and endoscopic anatomy of optic canal].

OBJECTIVE: To provide transnasal endoscopic optic nerve decompression with the anatomic reference. METHOD: Ten (20 sides) damp cadaveric heads of Chinese adults were cut sagittally along the midlines. The distance and angle between optic canal and anterior nasal spine were measured by ruler and protractor. Five (10 sides) damp cadaveric heads (including 2 children's) were undergone endoscopic dissection, and the optic canal and its related structure were observed. RESULT: From the study of gross anatomy, the specific structure of optic canal and internal carotid artery were found. The mean length of the medial wall of optic canal was (9.12 +/- 1.89) mm. The mean diameter of the optic canal orbital aperture was (4.12 +/- 0.53) mm. The distances from the midpoint of the medial wall of optic canal orbital aperture to anterior nasal spine was (61.22 +/- 6.23) mm, and the angle from the midpoint of the medial wall of optic canal orbital aperture to anterior nasal spine was (45.3 +/- 4.5) degrees. From the study of endoscopic anatomy, optic canal, looking like a light-reflective band, was alone optic canal orbital aperture posteriorly. Obvious prominence could be found in 7 sides (70%), while not been seen clearly in 3 sides (30%). CONCLUSION: The binding study of the gross and endoscopic anatomy of optic canal help us to recognize optic canal accurately under nasal endoscope, which can improve the veracity of transnasal endoscopic optic nerve decompression.

Adult↗
PubMed1984

Target selection by surgically misdirected optic fibers in the tectum of goldfish.

This study tested the capacity of regenerating optic fibers to read tectal markers and thereby grow to their appropriate tectal loci when initial position, optic pathway, and interfiber interactions are eliminated as useful cues. The stability of these markers with long-term optic denervation of the tectum was also examined. In adult goldfish optic fibers innervating lateroposterior optic tectum were dissected free of tectum and inserted into the medial anterior region of the opposite "host" tectum. Normally, fibers at this position either innervate medial anterior tectum or follow the medial division of the optic pathway into medioposterior tectum. Host tectum was denervated of all other optic fibers by enucleating its contralateral eye either at the time of the deflection or at various times up to 18 months prior to deflection. The regeneration of these deflected fibers into host tectum was examined by autoradiography and electrophysiology at 1 to 11 months later. At the insertion site deflected fibers split into two groups of roughly equal size. One group directly entered the optic layers of medial tectum and grew posterolaterally across the medial half of tectum into the lateral half. The second group followed an almost direct path to the lateral tectum, sometimes traversing through the deep cell layers of tectum in which optic fibers are not usually found. These fibers subsequently entered the optic layers at the lateral edge of tectum and grew posteriorly. This second path was not seen in controls in which optic fibers from medioposterior tectum were similarly deflected. Instead growth was almost entirely posteriorly directed. On the average by 1.5 months deflected lateroposterior fibers were preferentially distributed in the lateral half of the tectum. Densitometric measurements indicated nearly a 4-fold difference in lateroposterior compared with medial posterior labeling. By contrast, controls in which medial posterior fibers were deflected had 4 times more grains medially than laterally. There was also a posterior over anterior preference, but this was weak. There was no suggestion that long periods of optic denervation prior to deflection or long postoperative periods after deflection of lateroposterior fibers diminished the lateral over medial preference. These findings support the idea that stable tectal markers exist which are differentially read by medial and lateral optic fibers. However, in no case was the innervation by deflected fibers as selective as in the normal projection.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2006

Pathological optic-disc cupping.

PURPOSE OF REVIEW: Pathological optic-disc cupping is most often caused by glaucoma, but may be seen in many less-common neuro-ophthalmic conditions. The goal of this article is to examine a host of entities causing optic-disc cupping, present key differentiating characteristics and pathophysiologies, and outline diagnostic approaches. RECENT FINDINGS: Multiple entities not associated with elevated intraocular pressure or glaucomatous optic-nerve disease may result in pathologic optic-nerve excavation. Even with the photography and imaging of today, it is still difficult for the clinician to accurately diagnose other causes of optic-disc cupping. Up to 20% of patients may be misdiagnosed and treated for glaucoma due to misinterpretation of the optic-disc cupping. Newer forms of imaging including optical coherence tomography may assist the clinician in decision making. A scrutinizing history, close observation of disc appearance, and the vasculature will aid in the diagnosis of glaucoma or other entity of optic-disc cupping. SUMMARY: Optic-disc cupping is a consequence of myriad disorders. Knowledge of the anatomy and vasculature of the disc is quintessential to the understanding of how, why, when, and what type of optic-disc cupping occurs in various conditions. Cupping can be seen with neurological processes, including benign tumors, which are treatable. Patient history, visual fields assessment, and funduscopic findings are the key to unlocking the diagnosis of glaucomatous versus nonglaucomatous optic-disc cupping. As clinicians, we must remain vigilant and receptive to the findings of potentially ominous forms of nonglaucomatous optic-disc cupping.

Diagnosis, Differential↗
PubMed1993

Role of hydrogen peroxide in experimental optic neuritis. A serial quantitative ultrastructural study.

In order to determine the role of H2O2 in demyelination of the optic nerve, serial quantitative analysis of H2O2-derived cerium perhydroxide reaction product particles was obtained by computerized digitization of electron micrographs of the myelinated retrobulbar optic nerve, unmyelinated optic nerve head, and the optic nerve sheath of guinea pigs sensitized for experimental allergic encephalomyelitis (EAE) and euthanized 3-14 days later. We found that cerium perhydroxide reaction product particles were greatest in the myelinated optic nerve 3 days after antigenic sensitization, but at this focus decreased 7-14 days after antigenic sensitization. Reaction product accumulated in the unmyelinated optic nerve head and optic nerve sheath 3-14 days after sensitization. These results in the myelinated optic nerve suggest H2O2 consumption results in peroxidation of myelin lipid as demyelination proceeds 7-14 days after antigenic sensitization. Hydrogen peroxide accumulation in the optic nerve head and the optic nerve sheath appears to provide a reservoir for diffusion of H2O2 into the retrobulbar optic nerve and adjacent perineural nerve, contributing to the frequent predilection for optic nerve involvement in EAE and perhaps in multiple sclerosis.

Animals↗
PubMed1977

Specificity of fluorescein angiographic defects of the optic disc in glaucoma.

Fluorescein angiography of the optic disc was performed on normal subjects, patients with nonmyopic open-angle glaucoma dna myopic open-angle glaucoma, normal myopes, patients with optic atrophy due to chiasmal pituitary tumors, and patients with sectorial ischemic optic neuropathy due to vascular hypotension. The normal myopes, those with optic atrophy secondary to pituitary tumor, and the ischemic optic neuropathy group had optic discs similar in appearance to those with open-angle glaucoma. Absolute fluorescein filling defects occurred only in patients with open-angle glaucoma and sectorial ischemic optic neuropathy. The filling defects in open-angle glaucoma appear to be specific, indicating that the blood supply to the anterior portion of the optic nerve is involved, as in ischemic optic neuropathy. Fluorescein angiography of the optic disc may be useful to differentiate open-angle glaucoma from other entities that have similar optic discs.

Adult↗
PubMed2005

Tilt and decentration of three-piece foldable high-refractive silicone and hydrophobic acrylic intraocular lenses with 6-mm optics in an intraindividual comparison.

PURPOSE: Intraindividual comparison of tilt and decentration of three-piece foldable intraocular lenses (IOLs) with 6-mm optics and different edge design and material. DESIGN: Prospective randomized study. METHODS: Twenty-five patients with senile cataract (group I) received a foldable silicone, sharp optic edge IOL in one eye and a silicone, rounded optic edge IOL in the other eye. Group II (n = 28) received the foldable silicone, sharp optic edge IOL in one eye and an acrylate, sharp optic edge IOL in the other eye. Scheimpflug photography was performed after the procedure with an anterior eye segment analysis system. Tilt and decentration of the IOL optic were measured 1 week, 6 months, and 12 months after the procedure. RESULTS: In group I, the foldable silicone, sharp optic edge IOL showed a mean optic tilt of 3.03 +/- 1.79 degrees and an optic decentration of 0.24 +/- 0.13 mm; the silicone, rounded optic edge IOL showed a tilt of 3.26 +/- 1.69 degrees and a decentration of 0.23 +/- 0.13 mm. In group II, the foldable silicone, sharp optic edge IOL showed an average tilt of 2.34 +/- 1.81 degrees and a decentration of 0.29 +/- 0.21 mm after 12 months; the acrylate, sharp optic edge IOL had a tilt of 2.32 +/- 1.41 degrees and a decentration of 0.24 +/- 0.10 mm. There were no significant differences in either group. CONCLUSION: The examined IOLs showed a stable position regarding tilt and decentration in the first 12 postoperative months, independent of material and edge design. Slight deviations from the optical axis might affect the outcome in aspheric or multifocal IOLs.

Acrylic Resins↗
PubMed1999

Ocular responses to radial optic flow and single accelerated targets in humans.

Self-movement in a structured environment induces retinal image motion called optic flow. Optic flow on one hand provides information about the direction of self-motion. On the other hand optic flow presents large field visual motion which will elicit eye movements for the purpose of image stabilization. We investigated oculomotor behavior in humans during the presentation of radial optic flow fields which simulated forward or backward self-motion. Different conditions and oculomotor tasks were compared. In one condition, subjects had to actively pursue single dots in a radial flow pattern. In a second condition, subjects had to pursue single dots over a dark background. These dots accelerated or decelerated similar to single dots in radial optic flow. In a third condition, subjects were asked to passively view the entire optic flow stimulus. Smooth pursuit eye movements with high gain were observed when dots were actively pursued. This was true for single dots moving over a homogeneous background and for single dots in the optic flow. Passive viewing of optic flow stimuli evoked eye movements that resembled an optokinetic nystagmus. Slow phase eye movements tracked the motion of elements in the optic flow. Gain was low for simulated forward self-motion (expanding optic flow) and high for simulated backward movement self-motion (contracting optic flow). Thus, voluntary pursuit and passive optokinetic responses yielded different gain for the tracking of elements of an expanding optic flow pattern. During passive viewing of the optic flow stimulus, gaze was usually at or near the focus of radial flow. Our results give insights into the oculomotor performances and needs for image stabilization during self-motion and in the role of gaze strategy for the detection of the direction of heading.

Eye Movements↗
PubMed2002

All-optical processing with molecular switches.

A gradual transition from electrical to optical networks is accompanying the rapid progress of telecommunication technology. The urge for enhanced transmission capacity and speed is dictating this trend. In fact, large volumes of data encoded on optical signals can be transported rapidly over long distances. Their propagation along specific routes across a communication network is ensured by a combination of optical fibers and optoelectronic switches. It is becoming apparent, however, that the interplay between the routing electrical stimulations and the traveling optical signals will not be able to support the terabit-per-second capacities that will be needed in the near future. Electrical inputs cannot handle the immense parallelism potentially possible with optical signals. Operating principles to control optical signals with optical signals must be developed. Molecular and supramolecular switches are promising candidates for the realization of innovative materials for information technology. Binary digits can be encoded in their chemical, electrical, or optical inputs and outputs to execute specific logic functions. We have developed a simple strategy to gate optical signals with optical signals by using a photoactive molecular switch. We have demonstrated that NAND, NOR, and NOT operations can be implemented exclusively with optical inputs and optical outputs coupling from one to three switching elements. Our remarkably simple approach to all-optical switching might lead to the development of a new generation of devices for digital processing and communication technology.

Journal Article↗
PubMed1992

Immunohistological Localization of Tenascin in the Developing and Lesioned Adult Mouse Optic Nerve.

To gain insight into the morphogenetic functions of the recognition molecule tenascin in the central nervous system, we have studied its localization in the developing and lesioned adult mouse optic nerve using light and electron microscopic immunocytochemistry. Since tenascin is a secreted molecule, we have analysed the tenascin-synthesizing cells in tissue sections of retinae and optic nerves by in situ hybridization. A weak and homogeneous tenascin immunoreactivity was detectable in the developing retinal nerve fibre layer and optic nerve of 14-day-old mouse embryos, the earliest developmental age investigated. In the optic nerve of neonatal and 1-week-old animals, a high number of tenascin messenger RNA (mRNA)-containing cells were present, and antibodies to tenascin labelled the surfaces of astrocytes and unmyelinated retinal ganglion cell axons. With increasing age, expression of tenascin in the optic nerve was down-regulated at the mRNA and protein levels. At the fourth postnatal week, blood vessels in the optic nerve and collagen fibrils in the vicinity of meningeal fibroblast-like cells still showed significant immunoreactivity, but the optic nerve tissue proper no longer did so. In adult animals, tenascin was no longer detectable in association with blood vessels located in the myelinated part of the optic nerve, and meninges were only weakly immunoreactive. Also, tenascin mRNA-containing cells were no longer detectable in the myelinated part of the adult mouse optic nerve and few labelled cells were found in the meninges. In the retina, ganglion cells contained no detectable levels of tenascin mRNA at any of the developmental ages analysed. No significant up-regulation of tenascin expression was seen in the nerve tissue proper of transected proximal (i.e. retinal) and distal (i.e. cranial) optic nerve stumps of adult mice during the first 4 weeks after lesioning, the time period studied. However, collagen fibrils associated with meningeal fibroblast-like cells and located near the lesion site became strongly tenascin-immunoreactive 2 days after lesioning. Also, some blood vessels at the lesion site became immunoreactive. We conclude that tenascin in the optic nerve is synthesized by glial cells and not by retinal ganglion cells. The detectability of tenascin at embryonic ages suggests that it may mediate neurite growth in vivo. The absence of a strong, lesion-induced up-regulation of tenascin expression in the regeneration-prohibitive mouse optic nerve contrasts with the lesion-induced pronounced up-regulation in the regeneration-permissive peripheral nervous system, and may indicate a functional involvement of tenascin in regenerative processes. The high tenascin positivity of collagen fibrils at early postnatal ages and after lesioning suggests that tenascin expression may be correlated with mitotic activity of the associated meningeal fibroblast-like cells. Finally, tenascin may be involved in the process of vascularization, since the molecule is associated with blood vessels in developing and adult lesioned, but not intact adult, optic nerves.

Journal Article↗
PubMed1988

Reinvestigation of the role of the optic vesicle in embryonic lens induction.

The induction of the lens by the optic vesicle in amphibians is often cited as support for the view that a single inductive event can lead to determination in a multipotent tissue. This conclusion is based on transplantation experiments whose results indicate that many regions of embryonic ectoderm which would normally form epidermis can form a lens if brought into contact with the optic vesicle. Although additional evidence argues that during normal development other tissues, acting before the optic vesicle, also contribute to lens induction, it is still widely held, on the basis of these transplantation experiments, that the optic vesicle alone can elicit lens formation in ectoderm. While testing this conclusion by transplanting optic vesicles beneath ventral ectoderm in Xenopus laevis embryos, it became apparent that contamination of optic vesicles by presumptive lens ectoderm cells can generate lenses in these experiments, illustrating the need for adequate host and donor marking procedures. Since previous studies rarely used host and donor marking, it was not clear whether they actually demonstrated that the optic vesicle can induce lenses. Using careful host and donor marking procedures with horseradish peroxidase as a lineage tracer, we show that the optic vesicle cannot stimulate lens formation in neurula- or gastrula-stage ectoderm of Xenopus laevis. Since the general conclusion that the optic vesicle is sufficient for lens induction rests on studies in many organisms, we felt it was important to begin to test this conclusion in other amphibians as well. Similar experiments were therefore performed with Rana Palustris embryos, since it was in this organism that optic vesicle transplant studies had originally argued that this tissue alone can cause lens induction. Under conditions similar to those used in the original report, but with careful controls to assess the origin of lenses in transplants, we found that the optic vesicle alone cannot elicit lens formation. Our data lead us to propose that the optic vesicle in amphibians is not generally sufficient for lens induction. Instead, we argue that lens induction occurs by a multistep process in which an essential phase in lens determination occurs as a result of inductive interactions preceding contact of ectoderm with the optic vesicle.

Animals↗
PubMed2006

Description of the transfer function of an optical system with wavelet transforms.

According to the wavefront filtering idea of wavelet optics, the transfer function of an optical system is described with a wavelet scale function. In the transfer function described with a wavelet scale function, different scale parameters a,c and shift parameters b,d correspond to different subtransfer functions, which correspond to different situations of the optical system. According to the request of the optical system, by adjusting all these scale parameters, not only can we obtain the optical images under different conditions, but we can also obtain the singular points under this scale parameter; hence a more ideal output can be obtained by such processing. The transfer function described with a wavelet scale function can be adjusted according to the request of the optical system, which makes the described transfer function self-adjustable. According to all types of disturbing effects to the system, by adjusting the scale and shift parameters, the practical form of the transfer function of an optical system can be confirmed, which satisfies the request of the self-adjustability of the optical imaging system. The result of our analysis shows that describing the transfer function of an optical system with a wavelet scale function is not only feasible but also satisfies the request of the self-adjustability of the optical imaging system, and different optical systems can be described by different wavelet scale parameters. This work breaks from the formal additional describing mode of the transfer function of an optical system and makes description of the transfer function of an optical system convenient.

Journal Article↗