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Results for “retinal development”

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At least 1,351 records · Page 75Linked to original sources
PubMed1992

[De novo retinal break associated with excessive cryotherapy].

Three patients who had been treated with transscleral cryotherapy for retinal breaks and associated retinal detachment developed de novo retinal breaks and/or retinal thinning at the site of cryotherapy in the early postoperative period. Additional surgical interventions were required because retinal detachment had extended or remained unchanged postoperatively. We think that this may be due to excessive cryotherapy and is an early postoperative complication transscleral cryotherapy that to our knowledge has not previously been reported. This would suggest that when performing cryotherapy for retinal breaks and associated retinal detachment, care should be taken not to treat excessively.

Adult↗
PubMed1990

The development of the retinal projection to the olivary pretectal nucleus in normal and monocularly enucleated hamsters.

The projection to the olivary pretectal nucleus (OPN) from the contralateral eye is observed on the first day after birth and appears adult-like on postnatal day 5. The ipsilateral projection is present at postnatal day 4, and expands to fill the nucleus overlapping the contralateral projection, though never as dense, between days 6 and 8. Then, in normal hamsters, ipsilaterally projecting fibers retract to the ventral side of the OPN by day 10. However, the dense expanded projection in the dorsal OPN ipsilateral to the remaining eye in monocularly enucleated hamsters persists into adulthood.

Animals↗
PubMedDate not supplied

[A hormone-sensitive stage in the development of the retinal pigment epithelium in Hunter rats with hereditary retinal dystrophy].

The sensitivity of the retinal pigment epithelium (RPE) to the melanotropic effects of alpha-MSH and dbcAMP was assayed in an organ culture of the eye scleral part in the Hunter rats with inherited retinal dystrophy. The melanin synthesis was estimated by liquid scintillation on the RPE isolated enzymatically after 48-h cultivation. One eye from every animal was cultivated in a medium without natural components and with the hormone or dbcAMP (experiment), while the other in a hormone-free medium (control). The melanin synthesis was estimated by 14C-thiouracil incorporation. The result was expressed as a cpm/microgram DNA (experiment) to cpm/microgram DNA (control) ratio. In addition, the index of labelled nuclei was determined using 3H-thymidine autoradiography in the central RPE zone of the eyes from young rats of the same litter. The experiments with alpha-MSH confirmed the earlier data according to which the RPE of the 3 day old Hunter rats were insensitive to melanotropic hormones. This was not due to defects in the cytoplasmic melanin-synthesizing system, since under the influence of dbcAMP the melanin synthesis in the RPE increases more than four-fold as compared with the control; dbcAMP stimulates also the total protein synthesis, as estimated by 3H-leucine incorporation. The RPE of the 4 day old rats proved to be sensitive to alpha-MSH: the melanin synthesis increases more than twice suggesting the healthy state of the RPE membrane melanotropic receptors. alpha-MSH also stimulates the total protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Changes in the electroretinogram of Campbell rats with the development of hereditary retinal degeneration].

We studied the dependence of amplitudes of a- and b-waves of electroretinogram on intensity of light stimulus in Campbell rats with inherited retinal degeneration. On 20-th-29-th day after birth the amplitude of these waves in Campbell rats is smaller than in Wistar rats. On 30-th-40-th day response significantly decreases, down to complete disappearance of reaction. Weak response appears only to stimulus with the maximal luminance. According to decrease of amplitude of the a- and b-waves of the ERG, Campbell rats are practically blind at 40th day of postnatal life. The analysis of the form of whole ERG curve using the Fourier transformation allowed us to establish, that in Campbell rats on 20-th day after birth the amplitude of the first and second harmonics grows with increasing of stimulus luminance. At 30-th day the amplitude of the second harmonic in Campbell rats is much smaller than in Wistar rats and does not vary with increasing of stimulus luminance.

Aging↗
PubMed1977

[Changes in the electroretinogram and concentration or rhodopsin in the Hunter strain of rats during development of hereditary retinal degeneration].

Electroretinographic changes as well as rhodopsin content in the isolated retina and the eye cup in Hunter rats were studied during inherited retinal degeneration. The concentration of rhodopsin in the eye cup increases for the first 45 days after birth and then decreases slowly; the visual pigment concentration in the retina reaches its maximum by the 25th day and drops abruptly after the 35th day. The amplitude of the electroretinographic b-wave evoked by near-threshold and saturating stimuli decreases evenly till 35th day. After this day the threshold drastically increases and a-wave disappears. Thus, the 35th day is crucial in the degeneration process. The possible role played by abnormal rhodopsin metabolism in the changes observed is discussed.

Animals↗
PubMed1993

Argon laser scatter photocoagulation in treatment of branch retinal vein occlusion. A prospective clinical trial.

The objective of this prospective study was to ascertain whether scatter argon laser photocoagulation to the involved sector in major branch retinal vein occlusion and ischemic hemicentral retinal vein occlusion (a) prevents development of retinal and/or optic disk neovascularization and vitreous hemorrhage, and (b) affects visual acuity, visual fields and macular retinal lesions. The study was done in 271 eyes allocated to either treated (n = 61 eyes) or untreated (n = 210) groups. In this study, on an average follow-up of 3.6 years, the laser treatment (1) significantly reduced the risk of development of retinal neovascularization and vitreous hemorrhage, (2) did not affect the visual acuity and macular retinal lesions, and (3) produced a significant worsening in the peripheral visual fields compared to the untreated eyes. In view of our findings, we recommend that argon laser photocoagulation treatment should be given only when neovascularization is seen and not otherwise, because in the latter case, its detrimental effects may outweigh its beneficial ones.

Aged↗
PubMed2003

Role of arteries in oxygen induced vaso-obliteration.

In mice the retinal vasculature develops in the first postnatal week by spreading from the optic nerve head towards the retinal periphery. During this growth period, exposure to hyperoxia causes vaso-obliteration of capillaries in the retinal center but not in peripheral regions. High oxygen levels lead to downregulation of vascular endothelial growth factor (VEGF), an important survival factor for vascular endothelial cells, which could explain the vaso-obliteration caused by hyperoxia. However, it is not clear why only capillaries in the center of the retina are affected. We therefore investigated how capillary obliteration correlates with VEGF mRNA distribution by in situ hybridization in retinal whole mount preparations. In mouse pups reared under normoxic conditions VEGF mRNA was detectable across the entire vascular network but was virtually absent in the immediate vicinity of arteries. This was true along developing retinal arteries but also around the optic nerve head through which the entire arterial blood supply for the retinal and hyaloid vasculature passes. In these areas capillaries were absent, resulting in so-called capillary free zones. Exposure to hyperoxia caused an expansion of areas with low VEGF mRNA which correlated with capillary obliteration in these regions. Combined capillary obliteration around the optic nerve head and along retinal arteries lead to a large capillary free zone in the center of the retina. Thus, our observations suggest that hyperoxia affects the retinal vasculature by reducing VEGF mRNA levels near arteries and causing a widening of capillary free zones.

Animals↗
PubMed1992

Somatostatin is altered in developing retina from ethanol-exposed rats.

Optic nerve hypoplasia is seen in 50% of patients diagnosed with fetal alcohol syndrome and is due to a defect in the development of retinal ganglion cells. Somatostatin may influence the development of retinal ganglion cells, so we studied the effect of in vivo ethanol exposure on somatostatin expression in the developing retina. Somatostatin concentration is increased in retina from ethanol-exposed fetuses and pups and this increase in peptide is associated with excessive neurite formation and improper migration of the somatostatin-containing neurons at early postnatal ages. These disturbances may account for the eventual failure in retinal ganglion cell development that results in optic nerve hypoplasia.

Animals↗
PubMed1999

A developmental time line in a retinal slice from rainbow trout.

The retina in teleost fish continues to grow throughout much of the life of the animal, in part by the continuing differentiation of new tissue at the retinal margin, an area termed the peripheral growth zone (PGZ) (Lyall, Q J Micros Sci, 1957:98:101-110). We have developed a retinal slice preparation--including the PGZ--from juvenile rainbow trout (Onchorynchus mykiss), a species in which retinal growth is rapid and the PGZ is correspondingly pronounced. The PGZ slice preparation contains a time line of retinal development, with cells at different stages of maturation present side by side. We present evidence that the birth sequence of the various retinal cell types in the PGZ recapitulates the sequence during embryonic development. We also report data on the rate of growth of the PGZ in juvenile trout in vivo. Finally, we have used the PGZ slice preparation to make whole-cell voltage clamp recordings from individual retinal GCs at both early and late stages of maturation. We report that the amplitude of delayed rectifier and A-type potassium currents increases during GC maturation.

Animals↗
PubMed1988

Differential expression of acetylcholinesterase molecular forms in neural retina and retinal pigmented epithelium during chick development.

Neural retina (NR) and retinal pigmented epithelium (RPE) were used as a model for studying acetylcholinesterase (AChE) expression in neuronal and non-neuronal tissues during development. In chick embryo retina, increasing AChE activity appeared from day 7 to hatching, first in NR and then in RPE. NR contained 3 main AChE forms, 11.3S, 6.5S and 4.5S, resolved by sucrose density gradient centrifugation. An additional 19S form was exclusively detected in RPE whatever the extraction procedure followed. During differentiation, the proportions of AChE molecular form changed until they reached a steady state characteristic of mature neural retina, whereas in RPE, patterns of AChE molecular forms did not change significantly during development. Thus, 19S AChE appeared to be characteristic of non-neuronal retinal tissue. The expression of the AChE molecular forms in NR and RPE, and particularly the 19S form, was independent of the presence of the lens during retinal differentiation.

Acetylcholinesterase↗
PubMed1996

Retinal Thy-1 expression during development.

PURPOSE: To evaluate the developmental expression of Thy-1 in the retina. Thy-1, the most abundant mammalian neuronal surface glycoprotein, is likely to play a significant role in retinal development. In the mammalian retina, it is found predominantly, if not exclusively, on retinal ganglion cells. METHODS: Rat retinae of various ages were stained immunohistochemically for Thy-1 with 2G12, a monoclonal Thy-1 antibody. Sections were analyzed digitally to quantify bound antibody. Using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), the expression of Thy-1 protein was compared with the levels of mRNA detected. RESULTS: Thy-1-dependent fluorescence was detected in rat retinae from birth, albeit at low levels. Thy-1 labeling was localized predominantly to the ganglion cell layer. Minimal, fine patterns of linear and reticular fluorescence were noted in the inner nuclear layer. Thy-1 levels reached a maximal level at approximately postnatal day 14. RT-PCR measurements showed a similar time course for the increase in Thy-1 expression. CONCLUSIONS: The Thy-1 antigen is present in the inner retina at birth. Its level increases steadily after birth and peaks during the second week of life. Thy-1 expression is approximately coterminous with synaptogenesis of the inner plexiform layer and may play a role in synaptogenesis of the inner retina or in other developmental milestones in the formation of the visual system.

Animals↗