Apoptosis durante el desarrollo embrionario de la retina de tortuga (Trachemys scripta elegans) / Apoptosis in turtle embryonic retina (Trachemys scripta elegans)

La apoptosis o muerte celular programada es un proceso que ocurre durante el desarrollo del sistema nervioso. El objetivo de este estudio fue observar los patrones de apoptosis que se producen durante el desarrollo embrionario de la retina, desde el estadio S16 al momento del nacimiento, mediante miscoscopía óptica y electrónica. Se utilizaron retinas de embriones de tortuga. Nuestros datos muestran que los primeros signos de apoptosis comienzan en el estadio S16, en la capa nuclear interna y alcanzan su máxima densidad tanto en la capa nuclear interna como en la capa de células ganglionares en S20, para extinguirse, prácticamente, en el momento del nacimiento. Por otra parte, la apoptosis sigue un gradiente centro-periferia.

Apoptosis or programmed cell death is a process that occurs during development of the nervous system. The aim of this study was to observe the patterns of apoptosis that occur during embryonic development of the retina from the stage S16 at birth, by light and electron miscoscopia. Turtle embryonic retinas were used for the study. Our data show that the first signs of apoptosis begins at stage S16 in the inner nuclear layer and reaches maximum density both in the inner nuclear layer and the ganglion cell layer in S20 until they practically disappear at the time of birth. Furthermore, apoptosis follows a gradient center-periphery.

Características morfológicas de la retina del calderón común (Globicephala melas; traill, 1809) y su relación con el hábitat / Morphological characteristics of pilot whales retina (Globicephala melas; traill, 1809) and their relationship to habitat

Existe una estrecha relación entre las características morfológicas de los sistemas sensoriales, su funcionamiento y el hábitat al que están adaptados los organismos. En este sentido, de todos los mamíferos marinos estudiados, los cetáceos son los que más profundamente han modificado su estructura y fisiología ocular por su estrecha adaptación a una vida exclusivamente acuática. Para aportar más datos a la literatura, el objetivo de este trabajo es describir morfológicamente la retina de la ballena piloto a través de técnicas de microscopia óptica, con el fin de relacionarla con su adaptación al medio acuático. Nuestros datos muestran que la retina de Globicephala melas se organiza de acuerdo al mismo plan básico de los vertebrados. Tiene un grosor medio alrededor de 330±23 µm en las zonas de alta densidad de células ganglionares y 175±2 µm en la zona periférica. La capa de los fotorreceptores se corresponde con el 45% del grosor de la retina total. Presenta largos segmentos externos. La capa más característica de cetáceos en general y de Globicephala melas en particular, es la capa de células ganglionares. Su grosor, de 77,76±37,26 siendo la más variable de toda la retina. Esta capa presenta baja densidad celular pero tamaños excepcionalmente grandes, de 10 a 75 µm (promedio de 33,5 µm), denominadas células ganglionares gigantes.

There is a close relationship between morphological features of sensory systems, their function and habitat to which these organisms are adapting. In this sense, of all marine mammals that have been studied, cetaceans are the ones that have profoundly changed structure and ocular physiology in their adaptation to an exclusively aquatic life. To add further data to the literature, the aim of this paper is to describe morphologically the retina of the pilot whale through optical microscopy and relate their adaptation to the aquatic environment. Our data show that the retina of the long-finned pilot whale is organized according to the same basic plan of vertebrates. It has an average thickness of about 330±23 microns in areas of high ganglion cell density of 175±2 microns in the peripheral zone. Photoreceptor layer corresponds to 45% of total thickness of the retina and has long outer segments. The most significant characteristic of cetaceans in general and long-finned pilot whale in particular, is the ganglion cell layer. Thickness of 77.76±37.26 being the most variable of the entire retina. This layer has a low density but exceptionally large cell size of 10 to 75 microns (average of 33.5 microns), known as giant ganglion cells.

Effect of high salt loading on the retina of adult male rats with special reference to aquaporin 1: a histological and immunohistochemical study

In the retina, glial cells control ionic concentrations by mediation of transmembrane water fluxes through aquaporin [AQP] water channels. The risk factor of a high-salt diet on renal and cardiovascular systems is pretty well known. However, it is not yet known whether a high-salt diet alone can affect the retina. The aim of this study was to determine whether a high-salt diet alone can induce changes in the retina and whether it may be accompanied by changes in the expression and immunolocalization of water channel aquaporin1 [AQP1]. Forty-two adult male albino rats were used. They were divided into three equal groups. Group I served as the control group. Rats in group II were administered 2 ml of a high-salt solution [8% NaCl concentration] once daily by means of a gastric tube. Group III was the recovery group. Retinal tissues were collected and examined by means of light and electron microscopy. Immunohistochemical analysis using AQP1 and glial fibrillary acidic protein [GFAP] antibodies was performed and the results were statistically analyzed. The retina of rats given a high-salt diet [group II] displayed obvious disorganization of the outer segment of photoreceptors, together with cytoplasmic vacuolations in the cells of the inner nuclear and ganglionic layers. Furthermore, significant increase in AQP1 and GFAP immunoexpression was detected. In the recovery group [group III] the retinae of some rats regained their normal histological appearance, whereas others failed to do so. High salt loading might alter glial cell-mediated water transport through AQP1 channels in the retina

Effect of experimentally induced hypothyroidism during pregnancy and lactation on the retina of juvenile and adult albino rats and the possible role of thyroid hormone supplementation

Nervous system growth and differentiation are closely correlated with the presence of thyroid hormones in initial development stages. Hypothyroidism during the fetal and postnatal life results in an irreversible mental retardation syndrome. At the cellular level, T3 is known to act on neuronal, neuroretinogenesis, and glial lineages. In this study, we aimed to study the influence of hypothyroidism on retinal development in juvenile and adult rats and the effects of thyroid hormone supplementation on both periods of development. This study was conducted using 56 male albino rats. They were divided into three groups: group 1 [control group] included 24 animals, group 2 [juvenile group] included 16 animals whose mother received carbimazole [NeoMercazol] antithyroid drug at a dose of 0.02 mg/day/pregnant female during gestation and lactation, this group was further subdivided into subgroup 2a [hypothyroid juvenile animals] and subgroup 2b [thyroid hormone-supplemented juvenile animals], and group 3 [adult group] included 16 animals, this group was also further subdivided into subgroup 3a [hypothyroid adult animals] and subgroup 3b [thyroid hormone-supplemented adult animals]. At the end of the experiment, the animals were killed. Retinal specimens from all groups were processed for light and electron microscopic studies. Biochemical analysis was carried out to measure the serum levels of triiodothyronine, T4, growth hormone, and insulin growth factor-1. In addition, estimations of lipid peroxidation, catalase activity, and antioxidant enzymes were made. Statistical analysis was carried out to measure the retinal thickness. Light and electron microscopic studies showed that thyroid hormone deprivation altered the organization of the retina in juvenile and adult rats. These changes were apparent in the form of significant reduction in the retinal layer thickness. In addition, degenerative changes in some layers were observed. The group with thyroid hormone supplementation showed recovery of both structural changes and retinal thickness, this recovery was apparent in the juvenile group. Adult animals showed minimal recovery. Biochemical analysis of the serum of hypothyroid animals showed a significant increase in lipid peroxidation products and decease in the serum levels of antioxidants, growth hormone, and insulin growth factor-1, comparable with the controls. Administration of thyroid hormone significantly restored their levels especially in the juvenile group. Gestational and lactational hypothyroidism induced marked changes in the developing retina in juvenile and adult rats. These changes were mostly normalized by thyroid hormone administration especially in the juvenile group

Ultrastructure alterations of retinal photoreceptors of the black rat, Rattus rattus exposed to certain heavy metals

This study was designed to investigate the impact of lead and cadmium on the retinal photoreceptors of rats. Adult black rats, Rattus rattus, were selected and divided into control and exposed groups. The exposed group was housed in industrial car batteries room containing fumes of lead and cadmium. The retina prepared for scanning and transmission electron microscopy. The scanning electron microscopy revealed different lead-cadmium changes represented by gradual increasing in spaces between segments of the photoreceptors, associated with swelling of their inner segments and accompanied with rupture, degeneration and decreased numbers of some rods and cones in the outer segments. Disorganization, shortening, a decrease in number of the photoreceptors and a great deformity were the characteristic changes after prolonged exposure to the heavy metals. The aforementioned damages of the photoreceptors were confirmed at the ultrastructural level using transmission electron microscope in the form of progressive disorganization, shortening, swelling, widening of the intradiscal spaces, vacuolization and degeneration of the lamellae of the outer segments [OS], followed by the damage of mitochondria of the inner segments[IS]. Excessive penetration of the processes of the pigmented epithelium [PE] filled with pigments of different shapes and sizes between the damaged segments were noted. These pathological changes were considered the first symptoms in the retinal toxicity. The present results are alarming and call for further investigations to elucidate the impact of exposure to these heavy metals for longer periods on the rat vision and eye structure

[ key role of type IV collagen in developing retinal basement membrane in mouse]

Basement membranes are specialized extracellular matrices serve as development, proliferation and substrates for migration. Collagen fibers specially type IV, are the most important part of this area. As retina is one of the target organs in diabetes mellitus and diabetic retinopathy and diabetic nephropathy are major cause of end stage - renal and retinal diseases and resulting in increased in morbidity and mortality of effected individuals, therefore early diagnosis leads to better treatment. Investigation the appearance and distribution of collagen IV during gestational days and early postnatal period. 24 intact female Balb/c mice were kept under normal nutrition and environment condition. After mating, vaginal plug was assumed as zero day of pregnancy. From [13[th]-18[th]] days, gestation pregnant mice were sacrified and their embryos as well as pups from 1st to 5th days were collected. For histochemichal studies, the head of specimens were fixed, histological preparation was done and by using monocolonal antibody against for tracing of collagen type IV were carried out. Our finding revealed that amount of collagen IV in internal limiting membrane [ILM] and extra cellular matrix [ECM] of the retina appearance on embryonic 16[th] day and increase continuously until end stage of embryonic life. In addition, strong labeling was observed until 3rd day of postnatal period but these reactions did not increase significantly after these periods. These findings indicate that retinal development is dependent on different proteins by special regards specially collagen IV

A six-rhabdomere, open rhabdom arrangement in the eye of the chrysanthemum beetle Phytoecia rufiventris: some ecophysiological predictions based on eye anatomy

We are describing a rhabdom organization of the eye of the chrysanthemum beetle Phytoecia rufiventris that to date has not been described from any other insect. In cerambycid beetles free rhabdomeres, forming a circular, open rhabdom, surround a central rhabdom made up of the rhabdomeres of one or two cells. In Phytoecia rufiventris the central rhabdomeres are missing throughout the eye and the microvilli of the outer 6 rhabdomeres are regularly oriented in three directions. Following the classification of rhabdom types suggested by Wachmann (1979), we suggest to name the rhabdom arrangement seen in the retina of Phytoecia rufiventris [quot ]Grundmuster 3[quot ]. This pattern ought to facilitate polarization sensitivity and movement perception, features that agree with the behavioural repertoire of Phytoecia rufiventris.

effect of chloroquine on the retina of adult male albino rat and the possible protective role of Ginkgo biloba extract. A histological and immunohistochemical study

Chloroquine is an antimalarial drug and is widely used for the treatment of various rheumatic diseases. Unfortunately, its use has been associated with the development of toxic retinopathy. Because treatment with chloroquine is sometimes inevitable, interventions that abolish or at least attenuate retinal affection are of great importance. Several studies indicated that antioxidants may be beneficial for those at risk of developing retinal diseases. Of these, Ginkgo biloba extract [EGb 761] is a recently used agent for its known oxygenated radical scavenging properties. For demonstration of the effect of chloroquine on retinal structure and the possible protective role of EGb 761, forty adult male albino rats were used. They were divided into four equal groups; control group, EGb 761-treated group [100 mg/Kg body weight], chloroquine-treated group [28 mg/Kg body weight] and the fourth group was concomitantly treated with both EGb 761 and chloroquine. The animals were treated orally daily for 4 weeks and retinal specimens were examined by light and electron microscopy. Moreover, immunohistochemical study was performed to explore immunoreactivity for caspase-3 as an apoptotic marker. Light microscopic examination revealed structural changes in the retina of chloroquine-treated animals such as vacuolation of retinal pigment epithelial cells and photoreceptors, displacement of some cells of the outer and inner nuclear layers, pyknotic and fragmented nuclei in the inner nuclear layer as well as vascular congestion. Many caspase-3 positive cells were also observed in the inner nuclear and ganglion cell layers. Electron microscopy showed marked disorganization of photoreceptors and accumulation of lysosomes in retinal pigment epithelial cells. Condensation of nuclear chromatin was also observed in many nerve cells in inner nuclear and ganglion cell layers. Many Muller cells and microglia were detected inbetween the nerve cells. On the contrary, retinal structure was more preserved in EGb 761-treated rats. These findings suggested that EGb 761 could reduce the severity of chloroquine-induced retinopathy

Retinal histopathological changes following intravitreal injection of different doses of bevacizumab: an electron microscopic study

To determine the retinal toxicity of intravitreal bevacizumab in rabbits by electron microscopy. Six albino rabbits received one injection of intravitreal bevacizumab in one eye, and no injection [control] in the fellow eye. Two rabbits received 1.25 mg in 0.05 ml, two received 2.5 mg in 0.1 ml, and two received 5mg in 0.2 ml. for each dose of bevacizumab, one rabbit was sacrificed one day after injection, and the other one week later. The retina was then examined by transmission electron microscopy. The control eyes showed no abnormality. At 1.25 mg there was no change compared with controls. At 2.5 mg, there was mild transient cytoplasmic degeneration in the inner segments of the photoreceptors and the horizontal cells of the outer nuclear layer. At 5mg, there was, in addition to the changes above, marked cytoplasmic degeneration of the retinal pigment epithelial [RPE] cells with shrinkage of the nucleus, and numerous vacuoles in the nerve fiber layer. At one week, there was significant resolution of these changes. There was no evidence of bevacizumab toxicity to the rabbit retina after a single intravitreal injection of 1.25 mg. At 2.5mg, there were mild transient changes, whereas definite toxicity to the RPE cells and nerve fiber layer were seen at 5mg. The maximum recommended dose of intravitreal bevacizumab is therefore 2.5 mg

Retinal toxicity to triamcinolone acetonide's vehicle: an electrophysiology and electron microscopy study

To assess rabbit retinal toxicity to triamcinolone acetonide vehicle, benzyl alcohol, when injected intravitreally. This prospective comparative experimental study included 24 pigmented rabbits assigned into 2 groups; group 1 [experiment, n=12] received intravitreal 0.1ml of benzyl alcohol [BA], and group 2 [control, n=12] received intravitreal 0.1ml of balanced salt solution [BSS]; all injections were done in the right eyes. Clinical examinations were done on both eyes of all available rabbits before injection, at 1 and 3 hours post injection, and together with electroretinograms [ERGs] at 3, 7, 14, 28 and 42 days following injections. Three rabbits from each group were killed at 7, 14, 28 and 42 days and both eyes were sent for either light or electron microscopic examination for quantitative morphometric measurements. Mean amplitudes of ERG a and b waves of the BA-injected eyes were 6.42 +/- 9.02 micro v and 11.18 +/- 15.18 micro v at 3 days respectively, which was significantly reduced compared to the BSS-injected eyes [30.87 +/- 8.22 micro v and 57.90 +/- 13.38 micro v, respectively; p<0.01 t-test] and the non-injected contralateral eyes [36.20 +/- 7.85 micro v and 64.10 +/- 9.36 micro v, respectively; p<0.01 t-test]. These ERG responses continued to be significantly reduced in the BA-injected eyes [p<0.01 t-test] of the unkilled rabbits up to 6 weeks. The mean ganglion cell count [at a magnification of X200 in a standard frame of 4740.32 micro m[2]] were significantly reduced [p<0.005 t-test] in the BA-injected eyes [8.42 +/- 2.4] compared to the BSS- and non-injected eyes [16.42 +/- 3.9 and 16.5 +/- 4.2, respectively]. The mean inner nuclear layer [INL] and outer nuclear layer [ONL] thickness were significantly reduced [p<0.005 t-test] in the BA-injected eyes [3.78 +/- 0.96 micro m and 11.77 +/- 1.29 micro m, respectively] compared to the BSS- [6.1 +/- 0.92 micro m and 21.82 +/- 0.95 micro m, respectively] and non-injected eyes [7.05 +/- 1.9 micro m and 22.49 +/- 1.0/micro m, respectively]. Electron microscopy showed intracellular irreversible changes in the GCL, INL, ONL, and PRL at 6 weeks in group 1, with no significant changes in group 2. There was no significant rise in the intraocular pressure or clinical evidence of increased lens density during the study period. Triamcinolone Acetonide's Vehicle, benzyl alcohol, produced severe irreversible ERG and structural damage to rabbit neurosensory retinal following intravitreal injection

Ultraestructura de la retinopatía causada por la hiperoxia en ratas en desarrollo / Ultra structure of retinopathy induced by hyperoxia in developing rats

In order to evaluate the effect of postnatal hyperoxia on retinal structure, newborn rats were exposed to different oxygenation intervals (80 ± 1%) with three interruptions of 21% (30 min each). Four groups of rats were exposed from birth to the 6th, 9th, 12th and 14th postnatal day, respectively and another group was placed under normoxia. After this period all oxygenated groups and the controls remained under normoxia until they were 30 days old for the structural analysis of retina. Retinal histology was carried out using conventional techniques for transmission electron microscopy (TEM). In the ganglion cell layer of the retina from rats exposed for 9 days to hyperoxia, capillaries with large projections toward the lumen, were observed as a possible consequence of cellular edema of endothelium. The most severe damage was observed in rats exposed to hyperoxia during 12 and 14 days, showing mitochondrias swollen up and without crests in the areas surrounding the capillaries, necrosis and apoptosis processes, dense bodies, cells with swollen cytoplasms and rupture of the plasmatic membrane. The results suggest that postnatal hyperoxia causes severe damages to the retina in developing rats with a direct relationship between the time exposed to oxygen and ultra structural damages.

Con el propósito de evaluar el efecto de la hiperoxia posnatal sobre la estructura retiniana se analizaron retinas de ratas recién nacidas expuestas a diferentes periodos de oxigenación (80 ±1%), con tres interrupciones de 21% (30 min c/u). Cuatro grupos de ratas fueron expuestas desde su nacimiento hasta el 6to, 9no, 12mo y 14to días de vida y otro grupo fue mantenido en normoxia. Después de este periodo tanto los grupos expuestos a la hiperoxia como los controles permanecieron en normoxia hasta una edad de 30 días para el análisis estructural de la retina. La histología se hizo usando técnicas convencionales para microscopía electrónica de transmisión (MET). En la capa de células ganglionares de la retina de ratas expuestas a nueve días de hiperoxia, se observaron capilares con notables proyecciones hacia la luz, posiblemente como consecuencia de edema celular del endotelio. El daño más intenso fue observado en las ratas expuestas a hiperoxia durante 12 y 14 días, mostrando mitocondrias hinchadas y sin crestas en las áreas circundantes a los capilares, procesos de necrosis y apoptosis, cuerpos densos, células con citoplasmas hinchados y con ruptura de la membrana plasmática. Los resultados sugieren que la hiperoxia posnatal causa graves daños a la retina en las ratas en desarrollo, con una relación directa entre el tiempo de exposición al oxígeno y los daños ultraestructurales.

Retinal nerve fiber layer measurements in indian eyes using the scanning laser polarimeter, GDx.

PURPOSE: To obtain retinal nerve fiber layer (RNFL) measurements in normal Indian subjects of different age groups; and to determine the differences between the right and the left eye of a subject and variations between male and female gender using the scanning laser polarimeter GDx. MATERIALS AND METHODS: Prospective cross-sectional study of 180 eyes of 94 subjects. The RNFL values were obtained with the nerve fiber analyser GDx using default quadrant positions supplied by the manufacturer. Fourteen parameters were studied. Of these 6 were average-based parameters (average thickness, superior maximum, inferior maximum, ellipse average, superior average, inferior average), 4 ratio-based parameters (symmetry, superior ratio, inferior ratio, superior/nasal), 4 "other" parameters (maximum modulation, number, ellipse modulation, superior integral). The main outcome measures were effect of age on RNFL values, comparison of males and females and the right and the left eye of a subject. RESULTS: There was a negative linear correlation with age. Three ratio-based parameters showed a statistically significant negative correlation with age. "Number" increased with age. Superior maximum, superior average, superior integral, symmetry and superior ratio were higher for the left eye. 'Number' was higher for the right eye. Superior ratio and maximum modulation were more in females than males, no difference was noted with other parameters. CONCLUSION: There was a gradual decrease of RNFL values with increasing age - the superior quadrant values were higher for the left eye than the right eye, suggesting asymmetry. No significant differences were detected between males and females.

Fine-structural details of the photoreceptor membranes in the ocellus of the scale-insect parasite Centrodora sp. (Hymenoptora; Aphenelidae): a case of gene transfer between host and parasite?

Only one insect (the scale insect Eriococcus sp.) is known, in which photoreceptive lamellae appear to have replaced the usual arthropod rhabdom microvilli. We are now reporting the presence of photoreceptive membranes, which also appear to resemble lamellae rather than microvilli, but they are in the ocellus of the tiny wasp Centrodora sp., which parasitizes scale insect eggs. The apparently optically homogenous lens of the Centrodora ocellus measures approximately 10 µm in diameter and, thus, operates at the limits of diffraction. We calculated that the lens is capable of focusing a parallel bundle of rays on the retina of the ocellus.

Sildenafil citrate abuse [II]: an ultrastructural study of the long-term administration of sildenafil citrate in male albino rats

It has been reported that the most affected organs on abusing sildenafil citrate were the testis, retina, brain and heart; and that these changes were dose-and frequency-dependent. This study was set up to elucidate the ultra-structural alterations and hence the mechanism of toxicity in the retinal, cerebral, myocardial and testicular tissues which could result from administration of sildenafil citrate at a dose equivalent to the 100 mg tablet in humans administered at different frequencies. In addition, the study aimed at the assessment of the suitable dose and frequency of administration of the drug. Forty-eight male Wistar albino rats were used; and they were divided into: [n=12] negative control group. [n=36] rats received sildenafil citrate by gavage in a dose of 0.008 mg/g rat. This group was subdivided into 3 subgroups: [n=12] rats received the dose daily. [n= 12] rats received the dose day after day. [n= 12] rats received the dose once per week. The study extended for 18 weeks. Small portions from the brain, retina, heart and testes were excised and processed for electron microscopic examination. Sildenafil citrate causes histopathological alterations in the brain, retina, heart and testis in a dose-and time-dependent manner. It exerts its pathologic effects partly through persistent dilatation and thickening of t he blood vessel walls of the a forementioned tissues; and partly via direct action on the tissue cells and in particular on the mitochondria and rough endoplasmic reticulum

role of streptokinase in induction of posterior vitreous detachment: a scanning and transmission electron microscopic study of the retina in rabbits

The study was conducted to evaluate the possibility of inducing posterior vitreous detachment [PVD] by intravitreal injection of Streptokinase using scanning and transmission electron microscopic, and electrophysiological study. The present study was performed on thirty eyes of fifteen male white rabbits. The rabbits were divided into three equal groups. The right eye of the 3 groups received intravitreal injection of Streptokinase at three different concentrations [150,1500 and 15000 IV in 0.1 mL balanced salt solution [BSS]] in the- midvitreous cavity. The left eye in all animals received intravitreal injection of BSS and were considered as control group. Electroretinograph [ERG] was performed one hour, one day and one week following injection. The rabbits were killed after ten days and the enucleated eyes were processed for transmission and scanning electron microscopic examination. In group I, scanning electron microscopy showed the retinal surface covered with thin collagen fibers, while in group II, complete PVD with bare retinal surface was seen. Group III showed a bare retinal surface with hemorrhagic reaction and toxic effects on the retina by transmission electron microscopy. ERG findings are discussed. Intravitreal injection of 1500 IU of Streptokinase can lead to PVD without major toxic effects on the retina

Ultrastructure of surgically excised subfoveal neovascular membranes

We studied the ultrastructural features of four consecutive subfoveal neovascularmembranes (SFNM) associated with age-related macular degeneration. Cellular components of the membranes included retinal pigment epithelial (RPE) cells, endothelium-lined vascular channels, macrophages, myofibroblasts, fibrocytes, glial cells, erythrocytes, and lymphocytes. Extracellular interstitial constituents included collagen fibrils, basal laminar deposits, fibrin and young elastic fibrils. These findings show that SFNMs consist of various cells originating from surrounding tissues and vessels. Among these RPE cells and macrophages are the main cellular components and in conjunction with various extracellular matrix, especially collagen, may play an important role in the formation and maintenance of the membranes.

Peripheral retinal changes: a survey of high school boys from Hail, Saudi Arabi

Purpose: A clinical study was carried out to document the prevalence of developmental degenerative changes in the peripheral retina which are sometimes precursors of retinal detachment. We examined the eyes of 330 normal, asymptomatic High School boys of Saudi Arabian origin at three schools in hail, Saudi Arabia. Peripheral cystoid degeneration was a very common finding. Lattice degeneration was found in 30[9.1%] subjects, 13 of whom had bilateral lattice degeneration. In seven eyes lattice degeneration was associated with atrophic holes. Retinal breaks were found in 21[6.4%] subjects; the majority [78.3%] were atrophic holes with 38.9% found within areas of lattice degeneration. Other retinal changes discovered were: white without pressure, retinal tufts, paving stone degeneration, meridional folds, and meridional complexes. Knowledge of these peripheral retinal changes is important in understanding the mechanism, management and, more importantly, the prevention of rhegmatogenous retinal detachment. Prophylactic treatment of the asymptomatic precursor tesions of retinal detachment is rarely indicated in the absence of high risk factors such as myopia, aphakia, retinal detachment in the other eye, or a family history of retinal detachment

Müller cells and diabetic retinopathy

Müller cells provide nutrition for neural cells. We studied the structure and ultrastructure of Müller cells in the retina of thirty 3-month old Wistar rats, divided equally into 3 groups: normal rats, alloxan diabetic rats and treated alloxan diabetic rats, 1 and 12 months after induction of diabetes. We observed that the Müller cell nuclei under light microscope examination had hexagonal shape and higher density than the other nuclei. Differences between groups could be observed only by electron microscopy. In the diabetic rats, Müller cells presented dispersion of nuclear chromatin and electrondense nuclear granulations, with the presence of increased glycogen, dense bodies and lysosomes in the cytoplasm. The alterations were more frequent in the perivascular region and at 12 months. The treated diabetic rats exhibited some alterations we observed in diabetic rats, but these alterations were less intense. We conclude that, despite the treatment, the diabetic retinopathy continues to evolve

Ultrastructural change of the Muller cell in the culture of sensory retina

This study was performed to investigate the sequential changes of the retinal tissue in tissue culture condition. The human sensory retinal tissues were cultured for up to 2 weeks and 4 weeks, respectively. The initial changes showed the separation of the intercellular space and the consequent widening of the intercellular space with prolapse of cytoplasmic processes into the widened intercellular space. The internal limiting membrane was also separated from the inner retina, which led to the prolapse of the cytoplasm of the Muller cell. The growth of the Muller cell was most prominent during the 4-weeks' tissue culture period. These findings suggest that the Muller cell might contribute to the formation of cellular membrane in case of the defect of the internal limiting membrane in several pathologic conditions.