Reggie-1 and reggie-2, two cell surface proteins expressed by retinal ganglion cells during axon regeneration

Fish--in contrast to mammals--regenerate retinal ganglion cell axons when the optic nerve is severed. Optic nerve injury leads to reexpression of proteins, which typically are first expressed in newly differentiated retinal ganglion cells and axons. Here we identified two new proteins of fish retinal ganglion cells, reggie-1 and reggie-2, with monoclonal antibody M802 and molecular cloning techniques. In normal fish, M802 stained the few retinal axons derived from newborn ganglion cells which in fish are added lifelong to the retinal margin. After optic nerve injury, however, M802 labeled all retinal ganglion cells and retinal axons throughout their path into tectum. Consistent with M802 staining, reggie-1 and reggie-2 mRNAs were present in lesioned retinal ganglion cells, as demonstrated by in situ hybridization, but were not detectable in their normal mature counterparts. In western blots with membrane proteins of the adult goldfish brain, M802 recognizes a 48x10(3) Mr protein band. At the amino acid level, 48x10(3) Mr reggie-1 and reggie-2 are 44% identical, lack transmembrane and membrane anchor domains, but appear membrane associated by ionic interactions. Reggie-1 and reggie-2 are homologous to 35x10(3) Mr ESA (human epidermal surface antigen) but are here identified as neuronal surface proteins, present on newly differentiated ganglion cells at the retinal margin and which are reexpressed in mature ganglion cells upon injury and during axonal regeneration.     

Neurotrophins and their receptors in the tench retina during optic nerve regeneration

To understand the role of neurotrophins in the visual system, we investigated the distribution of both neurotrophins and their receptors within the retina of a fish that has the capacity to spontaneously regenerate its optic nerve axons after lesion. Intact retinas and retinas from tench, whose optic nerve had been crushed, were analyzed by immunohistochemistry and in situ hybridization. Trk receptors were mainly immunolocalized in cells of the inner nuclear and ganglion cell layers, a distribution coincident with that of their mRNAs. Nerve growth factor (NGF) immunoreactivity was detected exclusively in Müller cell processes, and brain-derived neurotrophic factor (BDNF) was found in both neuronal bodies and Müller cell processes. Neurotrophin-3 (NT-3) was detected in most of the cell nuclei, and neurotrophin-4/5 (NT-4/5) was localized in fibers and in a few cells in the inner retina. An increase in both TrkA protein and mRNA was detected during axonal regeneration within the retinal ganglion cell layer, reaching a maximum 30 days postcrush and returning to normal levels by day 90, when optic nerve regeneration is almost completed in this fish. None of the other neurotrophins and receptors showed appreciable changes. The heterogeneous distribution patterns of neurotrophins and their receptors in fish retina, their differences from the distribution observed in other species, and the TrkA changes after optic nerve crush suggest an important role for these molecules in the normal physiology of the fish retina and during the regeneration process.     

Transient neovascularisation of the frog retina during optic nerve regeneration

In conditions such as diabetic retinopathy, degenerative events in the retina are associated with neovascularisation. It is well established that a proportion of retinal ganglion cells die during optic nerve regeneration in the frog. The present study has determined whether neovascularisation takes place during this regenerative process. To do so, the pattern of blood vessels overlying the retinal ganglion cell layer was analysed in the frog Litoria (Hyla) moorei. We examined normal animals and those undergoing optic nerve regeneration following nerve crush. Blood vessels were visualised by perfusion with Indian ink and retinae were prepared as wholeamounts. In normal animals, the vascular tree was found to lie superficial to the nerve fibre layer and was more complex in regions overlying the area centralis and visual streak. After nerve crush, abnormal blood vessels transiently formed between the existing branches of the vascular tree. The new vessels were concentrated as an annulus centred on the optic nerve head and over the area centralis in midtemporal retina. The neovascularisation became most extensive between 6 and 10 weeks postcrush and disappeared by 12 weeks. The spatiotemporal sequence of neovascularisation suggests that it is triggered by accumulations of degenerating material formed as a proportion of the ganglion cells die during optic nerve regeneration.     

Axonal regeneration of retinal ganglion cells

We have developed retinal culture system of adult mammals to investigate neural regeneration from adult retinal ganglion cells (RGC). In this culture system, neurites were regenerated from RGCs of adult retinal explants. Investigation of neurotrophic effects on the neural regeneration showed that some interleukins and neurotrophins enhanced neurite regeneration from adult rat RGCs. We also found that the adult human retina had the ability of neural regeneration and that neurotrophins enhanced this ability. A novel neurotrophic factor secreted by adult rat hepatocytes also enhanced neurite regeneration not only in adult mice but also in aged RGCs. This result indicated the novel hepatocyte secreted factor is an activator which enhances neural regeneration of the aged retina. We concluded that even adult aged RGCs had the ability of axonal regeneration after injury and that neurotrophic factors might enhanced these abilities. Therefore neurotrophic factors might have practicable applications in drug treatments for intractable disease of the neural retina and optic nerve. Future progress of neuroscience is expected to rescue the retina from various diseases, and to render possible the transplantation of the retina and optic nerve.     

Tenascin-R inhibits the growth of optic fibers in vitro but is rapidly eliminated during nerve regeneration in the salamander Pleurodeles waltl

Tenascin-R is a multidomain molecule of the extracellular matrix in the CNS with neurite outgrowth inhibitory functions. Despite the fact that in amphibians spontaneous axonal regeneration of the optic nerve occurs, we show here that the molecule appears concomitantly with myelination during metamorphosis and is present in the adult optic nerve of the salamander Pleurodeles waltl by immunoblots and immunohistochemistry. In vitro, adult retinal ganglion cell axons were not able to grow from retinal explants on a tenascin-R substrate or to cross a sharp substrate border of tenascin-R in the presence of laminin, indicating that tenascin-R inhibits regrowth of retinal ganglion cell axons. After an optic nerve crush, immunoreactivity for tenascin-R was reduced to undetectable levels within 8 d. Immunoreactivity for the myelin-associated glycoprotein (MAG) was also diminished by that time. Myelin was removed by phagocytosing cells at 8-14 d after the lesion, as demonstrated by electron microscopy. Tenascin-R immunoreactivity was again detectable at 6 months after the lesion, correlated with remyelination as indicated by MAG immunohistochemistry. Regenerating axons began to repopulate the distal lesioned nerve at 9 d after a crush and grew in close contact with putative astrocytic processes in the periphery of the nerve, close to the pia, as demonstrated by anterograde tracing. Thus, the onset of axonal regrowth over the lesion site was correlated with the removal of inhibitory molecules in the optic nerve, which may be necessary for successful axonal regeneration in the CNS of amphibians.     

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.     

Xefiltin, a Xenopus laevis neuronal intermediate filament protein, is expressed in actively growing optic axons during development and regeneration

Neurofilaments are an important structural component of the axonal cytoskeleton and are made of neuronal intermediate filament (nIF) proteins. During axonal development, neurofilaments undergo progressive changes in molecular composition. In mammals, for example, highly phosphorylated forms of the middle- and high-molecular-weight neurofilament proteins (NF-M and NF-H, respectively) are characteristic of mature axons, whereas nIF proteins such as alpha-internexin are typical of young axons. Such changes have been proposed to help growing axons accommodate varying demands for plasticity and stability by modulating the structure of the axonal cytoskeleton. Xefiltin is a recently discovered nIF protein of the frog Xenopus laevis, whose nervous system has a large capacity for regeneration and plasticity. By amino acid identity, xefiltin is closely related to two other nIF proteins, alpha-internexin and gefiltin. alpha-Internexin is found principally in embryonic axons of the mammalian brain, and gefiltin is expressed primarily in goldfish retinal ganglion cells and has been associated with the ability of the goldfish optic nerve to regenerate. Like gefiltin in goldfish, xefiltin in Xenopus is the most abundantly expressed nIF protein of mature retinal ganglion cells. In the present study, we used immunocytochemistry to study the distribution of xefiltin during optic nerve development and regeneration. During development, xefiltin was found in optic axons at stage 35/36, before they reach the tectum at stage 37/38. Similarly, after an orbital crush injury, xefiltin first reemerged in optic axons after the front of regeneration reached the optic chiasm, but before it reached the tectum. Thus, during both development and regeneration, xefiltin was present within actively growing optic axons. In addition, aberrantly projecting retinoretinal axons expressed less xefiltin than those entering the optic tract, suggesting that xefiltin expression is influenced by interactions between regenerating axons and cells encountered along the visual pathway. These results support the idea that changes in xefiltin expression, along with those of other nIF proteins, modulate the structure and stability of actively growing optic axons and that this stability is under the control of the pathway which growing axons follow.     

Distribution of beta-amyloid precursor and B-cell lymphoma protooncogene proteins in the rat retina after optic nerve transection or vascular lesion

The expression of beta-amyloid precursor protein (APP) and B-cell lymphoma protooncogene protein (Bcl-2) in retinal cells in the rat was studied using immunocytochemistry at different times after intraorbital optic nerve transection or vascular lesion. Three hours to one month after transection of the optic nerve, a significant increase in APP and Bcl-2 immunostaining was observed in retinal Müller glia but not in retinal neurons. In contrast, injury to blood vessels that supply the eye without cutting the optic nerve resulted in a complete loss of APP and Bcl-2 immunostaining in Müller cells and an increase in immunoreactivity in distinct populations of retinal neurons. The overall pattern of APP immunostaining in Müller cells and neurons was essentially the same as that of Bcl-2 under identical experimental conditions. These results suggest that the expression of APP and Bcl-2 in retinal cells is dependent on the nature and severity of injury, and that rapid and common mechanisms are involved in regulating the expression of these molecules.     

Differential expression and distribution of focal adhesion and cell adhesion molecules in rat hepatocyte differentiation

The present study has examined the distribution of axons of differing sizes in the optic pathway of the ground squirrel. Axon diameters were measured from electron micrographs at various locations across sections of the optic nerve and tract, and total distributions and numbers were estimated. In both the nerve and tract, roughly 1.2 million optic axons were present. The population of optic axons had a unimodal size distribution, peaking at 0.9 microm in diameter and having an extended tail toward larger diameters. Local axon diameter distributions in the optic tract indicated distinct (though partially overlapping) axon diameter classes, including one of fine sizes peaking at 0.8-0.9 microm, a second of medium sizes peaking around 1.7-1.8 microm, and a third composed of the larger fibers with diameters up to 4.8 microm. The fine-caliber axons were found at all locations in the tract, and were the only axons present immediately adjacent to the pia, while the medium- and coarse-caliber axons were found at deeper locations. Curiously, the larger axons were found primarily in the medial parts of the tract, where axons from the dorsal retina normally course. A similarly restricted distribution of the larger axons was observed in the dorsotemporal parts of the optic nerve, suggesting that this difference in the tract may relate to an asymmetric distribution of ganglion cells on the retina giving rise to these axons. Measurements of axonal size taken within the optic fiber layer in dorsal and ventral parts of the retina confirmed this asymmetry, consistent with previous demonstrations of soma size differences in the dorsal versus ventral retina. The partial segregation of axons by size in the optic tract of the ground squirrel then reflects both the asymmetric distribution of retinal ganglion cell classes and the chronotopic reordering of optic axons that occurs within the chiasmatic region.     

Seven retinal specializations in the tubular eye of the deep-sea pearleye, Scopelarchus michaelsarsi: a case study in visual optimization

The deep-sea pearleye, Scopelarchus michaelsarsi (Scopelarchidae) is a mesopelagic teleost with asymmetric or tubular eyes. The main retina subtends a large dorsal binocular field, while the accessory retina subtends a restricted monocular field of lateral visual space. Ocular specializations to increase the lateral visual field include an oblique pupil and a corneal lens pad. A detailed morphological and topographic study of the photoreceptors and retinal ganglion cells reveals seven specializations: a centronasal region of the main retina with ungrouped rod-like photoreceptors overlying a retinal tapetum; a region of high ganglion cell density (area centralis of 56.1 x 10(3) cells per mm2) in the centrolateral region of the main retina; a centrotemporal region of the main retina with grouped rod-like photoreceptors; a region (area giganto cellularis) of large (32.2+/-5.6 microm2), alpha-like ganglion cells arranged in a regular array (nearest neighbour distance 53.5+/-9.3 microm with a conformity ratio of 5.8) in the temporal main retina; an accessory retina with grouped rod-like photoreceptors; a nasotemporal band of a mixture of rod- and cone-like photoreceptors restricted to the ventral accessory retina; and a retinal diverticulum comprised of a ventral region of differentiated accessory retina located medial to the optic nerve head. Retrograde labelling from the optic nerve with DiI shows that approximately 14% of the cells in the ganglion cell layer of the main retina are displaced amacrine cells at 1.5 mm eccentricity. Cryosectioning of the tubular eye confirms Matthiessen's ratio (2.59), and calculations of the spatial resolving power suggests that the function of the area centralis (7.4 cycles per degree/8.1 minutes of arc) and the cohort of temporal alpha-like ganglion cells (0.85 cycles per degree/70.6 minutes of arc) in the main retina may be different. Low summation ratios in these various retinal zones suggests that each zone may mediate distinct visual tasks in a certain region of the visual field by optimizing sensitivity and/or resolving power.     

Inhibition by protein kinase C of the 86Rb+ efflux and vasorelaxation induced by P1075, a K(ATP) channel opener, in rat isolated aorta

The expression of GABA in the human fetal (12-25 weeks of gestation), postnatal (five-month-old), and adult (35-year-old) retinas was investigated by immunohistochemistry. GABA expression was seen as early as 12 weeks in the undifferentiated cells of the inner neuroblast zone; a few optic nerve fiber layer axons were clearly labeled, suggesting that some of the stained cell bodies were prospective ganglion cells, others could be displaced amacrine cells. From 16-17 to 24-25 weeks, intense labeling was found in the amacrine, displaced amacrine, and some ganglion cells. During this time period, horizontal cells (identified by calbindin immunohistochemistry), undergoing migration (periphery) and differentiation (center), expressed GABA prominently. In the postnatal retina, some horizontal cells were moderately labeled, but very weakly in a few cells, in the adult. The Müller cells developed immunoreactivity first weakly at 12 weeks and then moderately from 16-17 weeks onward. The staining was also evident in the postnatal and adult retinas, showing labeled processes of these glial cells. Virtually no axons in the adult optic nerve and nerve fiber layer were stained; the staining was restricted to a few, large ganglion cells and displaced amacrine cells: Some amacrines were also labeled. The possibility that GABA might play a role in horizontal cell differentiation and maturation is highlighted. Other evidences suggest that GABA might play a role in metabolism during retinal development.     

Up-regulation of Bax protein in degenerating retinal ganglion cells precedes apoptotic cell death after optic nerve lesion in the rat

Retrograde degeneration of retinal ganglion cells as a consequence of optic nerve lesion has been shown to fulfil the criteria of apoptosis. In the present study, we investigated the time course of ganglion cell apoptosis following intraorbital crushing of the optic nerve in adult rats using morphological criteria and applying a terminal transferase technique (TUNEL) for in situ detection of DNA strand breaks. In addition, we examined expression patterns of the anti-apoptotic proteins Bcl-2 and Bcl-X and the cell death-promoting protein Bax in retinae after crushing the optic nerve. Apoptotic nuclei were detected in the ganglion cell layer in the first 3 weeks after optic nerve crush, with a peak after 6 days. Bcl-2 and Bcl-X proteins were expressed in ganglion cells at low levels. Expression of Bcl-2 decreased further during the days following crush. Bcl-X expression was initially increased, followed by a decline over the following days. In contrast, Bax protein, which was expressed in most ganglion cells at moderate baseline levels, was sharply increased as early as 30 min after crush, reached peak levels after 3 days, and remained up-regulated for at least 1 week thereafter. Double labelling for Bax and TUNEL in retinal sections, however, did not reveal colocalization of the two signals in individual retinal ganglion cells, consistent with the idea that increases in Bax precede apoptosis after optic nerve lesion. Thus, retinal ganglion cell death might be prevented by ablation of Bax protein in these cells, or by up-regulation of Bax-antagonists such as Bcl-2 or Bcl-X.     

The retinohypothalamic tract originates from a distinct subset of retinal ganglion cells

The retinal ganglion cells giving rise to retinohypothalamic projections in the rat were identified using retrograde transport of horseradish peroxidase (HRP) or FluoroGold injected into the suprachiasmatic nucleus (SCN), and using transneuronal transport of the Bartha strain of the swine herpesvirus (PRV-Bartha). When PRV-Bartha is injected into one eye, it is taken up by retinal ganglion cells, replicated, transported to axon terminals in the SCN, and released. There the virus may take one, or both, of two paths to retinal ganglion cells in the contralateral eye: 1) uptake by SCN neurons, replication, and release from the neurons with uptake and retrograde transport in retinal afferents originating in the contralateral retina; 2) transneuronal passage through axo-axonic appositions between retinal afferents in the SCN with subsequent retrograde transport of virus to the contralateral retina. The ganglion cells thus labeled are a homogeneous population of small neurons (mean diameter, 12.8 +/- 2.2 microns and mean area, 81.8 +/- 21.8 microns 2) with sparsely branching dendrites that are widely distributed over the retina. This population is best identified when virus labeling of retinal projections in areas beyond the hypothalamus is eliminated by lateral geniculate lesions that transect the optic tract at its entry into the geniculate complex. The same population is labeled with retrograde tracers but, with both HRP and FluoroGold, other ganglion cells are labeled, presumably from uptake by fibers of passage, indicating that the virus is a more reliable marker for ganglion cells giving rise to retinohypothalamic projections. The ganglion cells identified correspond to a subset of type III, or W, cells.     

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.     

Perfusion of the juxtapapillary retina and optic nerve head in acute ocular hypertension

Chronically elevated intraocular pressure (IOP) is often associated with glaucomatous optic nerve atrophy. Impaired blood flow may play a role in the pathogenesis of this disease. We present data concerning juxtapapillary retinal and optic nerve-head blood flow during acute increases in IOP. With the combination of a laser Doppler flowmeter and a scanning-laser system (Scanning Laser Doppler Flowmeter, SLDF; Heidelberg Engineering) the perfusion of the retina and the optic nerve head was quantified and visualized. Juxtapapillary retinal and optic nerve-head blood flow was measured simultaneously by SLDF during variations in IOP induced by a suction cup in nine healthy volunteers. The ocular pressure was increased for 2 min to IOP +15 mmHg, then to IOP +30 mmHg, and finally, to IOP +45 mmHg. Ocular perfusion pressure (PP) was calculated as the mean arterial blood pressure minus the IOP. The declines in juxtapapillary retinal flow as expressed in present per 10-mmHg IOP elevation ranged from 3.6% to 14.1% (median 7.4%). Over all measurements we found a significant linear relationship between juxtapapillary retinal blood flow and PP (r = 0.55, P < 0.0001). The observed decrease in optic nerve-head blood flow with increasing IOP was significantly greater as compared with the retinal blood flow decrease (8.4%/10 mmHg versus 7.4%/10 mmHg, P < 0.05). SLDF enables the quantification and visualization of perfused capillaries of the retina and the optic nerve head in high resolution. Acute elevations of IOP led to a decreases in juxtapapillary retinal and optic nerve-head blood flow of 7.4% and 8.4%/ 10-mmHg IOP increase, respectively.     

A simplified screening test for the identification of individuals with diminished vision in developing countries

The mammalian visual system, particularly retinal ganglion cells, has been used for studying the functions of neurotrophic factors on neurons for many years. The major biological effects of neurotrophic factors on retinal ganglion cells observed so far are the promotion of viability and axonal regeneration. However, there are still some controversies regarding the effects of neurotrophic factors on retinal ganglion cells in the literature. This review is aimed to summarize the available information on the biological actions of these neurotrophic factors on survival and axonal regeneration of retinal ganglion cells and the expressions of neurotrophic factor receptors in the retina. Generally, brain-derived neurotrophic factor, neurotrophin-4/5, fibroblast growth factor and glial cell line-derived neurotrophic factor increase the survival of retinal ganglion cells while the effect of ciliary neurotrophic factor on the viability of adult retinal ganglion cells is controversial. The ciliary neurotrophic factor is the only effective factor in promoting long distance axonal regeneration of retinal ganglion cells whereas brain-derived neurotrophic factor and neurotrophin-4/5 only enhance neurite sprouting within the retina.     

beta-Amyloid precursor protein fragments and lysosomal dense bodies are found in rat brain neurons after ventricular infusion of leupeptin

Infusion of the serine and thiol protease inhibitor, leupeptin, is known to cause a reduction of fast axoplasmic transport, and accumulation of lysosomal dense bodies in neuronal perikarya. We have found these dense bodies in hippocampal and cerebellar neurons contain ubiquitin conjugated proteins. We now demonstrate that these accumulated neuronal lysosomes are labeled by antisera to the cytoplasmic, transmembrane and extracellular domains of beta-amyloid precursor protein (APP) and also that lysosomal APP is fragmented. This in vivo model confirms that neurons can process APP via a lysosomal pathway and that neuronal lysosomes in vivo contain both N-terminal and potentially amyloidogenic C-terminal fragments of APP. We also show that increased APP immunoreactivity after leupeptin treatment is seen first in neurons and later in astrocytes. On recovery from infusion, APP N-terminal immunoreactivity diminishes whilst C-terminal reactivity remains in neurons. These findings are consistent with production in whole brain of potentially amyloidogenic fragments of APP within neuronal lysosomes in perikarya and dendrites implying that neurons may play a role in forming the beta-amyloid of plaques.     

Leber hereditary optic neuropathy. Electron microscopy and molecular genetic analysis of a case

BACKGROUND: Leber hereditary optic neuropathy (LHON) is a mitochondrial genetic disorder characterized by bilateral central visual loss typically in early adulthood. Few histopathologic studies, including ultrastructural and molecular genetic analysis, have been reported. METHODS: Ocular tissue was obtained postmortem from an 81-year-old woman with LHON from the Queensland 1 pedigree characterized by mutations at nucleotide positions 4160 and 14484. Routine histopathologic studies, electron microscopy, electron-probe analysis, and molecular genetic analysis were performed. RESULTS: Marked atrophy of the nerve fiber and retinal ganglion cell layers and optic nerves was present. Results of electron microscopic examination demonstrated 1.2 microns electron-dense, double-membrane-bound inclusions, consisting of calcium by electron-probe analysis, in retinal ganglion cells. The optic nerve was homoplasmic for mutations 4160 and 14484. CONCLUSION: Optic nerve and inner retinal atrophy in LHON may be a result of metabolic mitochondrial dysfunction leading to intramitochondrial calcification. Homoplasmy for mitochondrial mutations 4160 and 14484 in the leukocyte/platelet fraction of whole blood may correlate with homoplasmy in the optic nerve.     

The surgical treatment of normotensive glaucoma

The efficacy of surgical treatment of low (normal)-pressure glaucoma is validated on the basis of analysis of the disease progress risk factors. The risk factors are inadequate intraocular pressure (IOP) and insufficient blood supply to the optic nerve and retina. For stabilizing the glaucomatous process, IOP is to be reduced below 14 mm Hg. After antiglaucoma surgery, IOP decreases by 35% on average (to 13.9 mm Hg), and visual field is retained in remote period in 81.2% patients. Antiglaucoma operation with simultaneous decompression of the optic nerve results in a greater increase of visual field due to improvement of blood supply to the optic nerve and retina; visual functions are stabilized for a long time in 77.8% cases at a higher IOP (16.14 mm Hg) in patients with worse initial status. Functional results of surgery for normotensive glaucoma depend on ophthalmic tone and optic nerve and retinal hemodynamics.