Development of the New Zealand White Rabbit Eye: I. Pre- and Postnatal Development of Eye Tunics.

The New Zealand white (NZW) rabbit has been and is right now regularly utilized in ophthalmic surgery evaluation. Inside NZW rabbit eye, the visibility of ocular structures throughout surgical procedure is fantastic. Younger rabbits are used in different ages for the evaluation of ophthalmic surgery. Complete studies of ocular development in the NZW rabbits have not been reported previously. The aim of the present investigation was to describe the major landmarks and the time course of the pre- and post-natal development of the complete eye tunics of the NZW rabbit to give a superb model as well as a fruitful area for further ophthalmological investigations. Serial histological sections of NZW rabbit prenatal (E13-E28) and post-natal (P1-P14) stages were examined, respectively. The eye of the NZW rabbit developed in a similar manner to that of the human and domestic animals eyes; the principal differences were at the time of occurrence of certain developmental events, absence of pigmentation which represent an exploited benefit for ophthalmic surgery, remarkable Bowman's membrane at E25, poor developed ciliary stroma and juvenile retinal layer until P9. In human, the basic morphogenetic processes of the development of eye tunics are completed towards the end of the first half of gestation period. However, the latter represents the beginning stage of the development of eye tunics in the rabbit. Thus, allowing various extensive ophthalmic researches to be performed.

The differing embryonic origins of retinal and uveal (iris/ciliary body and choroid) melanosomes are mirrored by their phospholipid composition.

The phospholipids present in uveal (iris/ciliary body and choroid) and retinal bovine ocular melanosomes were identified using mass spectrometry. Similar phospholipid content is found for the two types of uveal melanosome, with sphingomyelin being the major species. Significant differences are found between the uveal and retinal melanosome. Glycerophosphoethanolamine (GPEtn) is the major species in the retinal pigment epithelium (RPE); 93% of the GPEtn contain polyunsaturated fatty acids, notably docosahexanoic acid and arachidonic acid, in the sn-2 position. RPE melanosomes also contain detectable quantities of glycerophosphoserine and glycerophosphate; these species were not detected in the uveal samples. While the structural and functional roles of melanosomal lipids largely remain to be determined, these different lipid compositions reported herein offer new insights into the roles of melanosomes in the different ocular tissues.

Choroidal melanocytes and associated pathology.

The embryologic origins of choroidal and cutanoeus melanocytes, also of the genes involved in cutaneous and choroidal melanoma, are identical, even the two kinds of tumors are different entities. This is a general scientific report, which stretches the molecular mechanisms, as basement of choroidal melanocytes proliferation.

[The development of the pigment epithelium and its interrelation with uveal pigment cells]. / Dezvoltarea epiteliului pigmentar si interrelatia cu celulele pigmentare din uvee.

Authors propose one study of retinal cells population in different stages of ontogenesis and one study of the pigmentogenesis process at the level of uveal tract and external retinal stratum. The study was achieved with embryonic and fetal technique of paraffin inclusion. Concomitantly with loading with pigment of the external retinal stratum and so pigmentary uveal tract is present. Dynamics of the retinol cells population varies with stages and chronological age, the number of pigmented uveal cells increasing proportionally but at different parameters with the pigmented retinal stratum one simultaneous with age under influence specially of humoral factors.

[The interrelations between the pigment cells of the uveal tract and the cell population of the retina in ontogeny]. / Aspecte ale interrelatiilor dintre celulele pigmentare din tractul uveal si populatia celulara din retina în ontogeneza.

The authors suggest themselves to follow in dynamic the cellular retinal population in different ontogenetic phases and also the progress of pigmentagenesis in the uveal tract and in the enteral stratum of the retina. For this purpose there have been used eyes from embryos and fetuses from the interrupted pregnancies. The obtained material was processed in the classical hystological technique and for the objectiveness of the phenomena there have been used methods of biometry. The authors, reached the conclusion that the pigmenting of the uveal stratum is made simultaneously with the loading with pigment of the enteral stratum of the retina, under the influence of different factors, especially the humoral ones and the evolution of the cellular retinal population varies, depending on ontogenetic phases and ages till birth.

Normal uveal melanocytes in culture.

Normal uveal melanocytes of rhesus and cynomolgus macaques can be grown in culture for 3-9 months and subcultured a few times. Postnatal and adult choroidal melanocytes are terminally differentiated cells. They are melanin-containing but not actively melanin-synthesizing cells. They do not undergo cell division, nor do they incorporate tritiated thymidine, but otherwise they are metabolically active. Postnatal and young adult iridial melanocytes are metabolically more active than choroidal cells. They require a feeder cell layer for attachment and to be maintained in a healthy condition. An endothelial cell line established from a rhesus fetal choroid-retina proves to be an effective feeder layer for adult iridial cells. Fetal uveal melanocytes divide slowly and usually require some stimulus and a special culture environment supplemented with 12-O-tetradecanolphorbol-13-acetate and cholera toxin. They can grow and differentiate in vitro. Iridial melanocytes grow and change into cells resembling postnatal choroidal melanocytes. Similar changes occur during development in utero. These findings further suggest that, in vivo, iridial melanocytes migrate and mature to become choroidal melanocytes.

Incipient histopathological lesions in citral-induced microphthalmos in chick embryos.

Microphthalmos was indeed experimentally in 3-day-old chick embryos by intraamniotic injection of citral. Various degrees of this particular microphthalmic syndrome were observed. Severe cases were always accompanied by destructive changes in the ipsilateral part of the head. The corneal epithelium lost its continuity and the lens showed, even in the early stages, severe degenerative changes with spherophakia. The neural retina seemed to be affected later and showed hyperplasia and fold formation, while the retinal pigment epithelium was only mildly affected. The mesenchyme behaved differently according to its location: the superficial corneal and ciliary mesenchyme underwent hyperplasia, while the deeper choroidal mesoderm showed edematous changes only. This temporal and spatial distribution of pathological changes in the eye structures favors the assumption that citral acts locally. The experimental microphthalmic syndrome is not only due to the direct effect of the exogenous teratogenic factor on the ocular anlagen but is also the result of subsequent adaptive changes of these structures to the new environmental condition.