Evidence of membrane transformation during melanogenesis. Electron microscopic study on the retinal pigment epithelium of chick embryos

Stanka, P; Rathjen, Peter D.; Sahlmann, Bernd

doi:10.1007/bf00249216

Cited by 17 publications

(12 citation statements)

References 20 publications

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“…This and further reports showed that besides the classical premelanosomes schematically presented by Stanka et al (1981) and also shown in Figure 1, other premelanosomes are existing. Jimbow et al (1979) found spherical premelanosomes in which vesiculo-globular bodies were involved in both euand pheomelanogenesis in the RPE of chick embryos.…”

Section: Morphological Stages Of Melanogenesissupporting

confidence: 75%

“…At present it is generally believed that melanogenesis in RPE and choroid follows a common pathway (Feeney et al, 1965;Hearing et al, 1973; Hu and Mah, 1983; Sarna 1992). Premelanosomes should be derived either from the rough (Stanka, 1971; Stanka et al, 1981) or, smooth (Mishima et al, 1978) endoplasmic reticulum or from polysomes (Moyer, 1961). Other workers were not able to determine the origin of mekinoflaments in the eyes of black and beige mice (Lutzner and Lowrie, 1972).…”

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confidence: 99%

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Does Melanin Turnover Occur in the Eyes of Adult Vertebrates?

Schraermeyer

1993

Pigment Cell Research

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This paper is a review of what is known about the turnover of melanin in iris, choroid, and retinal pigment epithelium (RPE) of the adult vertebrate eye. Differences in size and structure of choroideal and retinal pigment epithelial melanin granules are shown by electron micrographs. The classical stages of melanin synthesis, including the premelanosome, are shown in the RPE of adult hamsters that had been exposed to intense light. Degradation or synthesis of melanin also seem to occur in the melanocytes of the choroid in these animals.It is postulated that all three pigmented eye tissues (iris, RPE, and choroid) of adult vertebrates form melanin granules in vivo. However, nothing is known about the amount of this turnover.Key words: Melanosome, Imosome, Phagosome, rnsinase, Peroxidase, Radical INTRODUCTIONIn the eyes of vertebrates two types of pigment cells belonging to different cell lines are present. The retinal pigment epithelium (RPE) originates from the outer neuroectodermal sheath of the eyecup, whereas the melanocytes of the uvea (choroid and iris) immigrate from the neural crest (Heiman, 1972; Ozanics et al., 1978; reviewed by 'Ibrczynski 1982).While it is generally accepted that the key enzyme for mammalian meh-nesis is tymsinase (Lerner et al., 1950; K6rner and F'awelek, 1982), the origin of the matrix component of melanogenesis in the RPE, the premelanosome, has been subject to controversial views. At present it is generally believed that melanogenesis in RPE and choroid follows a common pathway (Feeney et al., 1965;Hearing et al., 1973; Hu and Mah, 1983; Sarna 1992). Premelanosomes should be derived either from the rough (Stanka, 1971; Stanka et al., 1981) or, smooth (Mishima et al., 1978) endoplasmic reticulum or from polysomes (Moyer, 1961). Other workers were not able to determine the origin of mekinoflaments in the eyes of black and beige mice (Lutzner and Lowrie, 1972). Alternatively, autophagic vacuoles (Novikoff et al., 1979) or phagosomes (Schraermeyer, 1992b) were taken into consideration as matrix components for melanin granule formation in the RPE. While the turnOver of melanin is high in the skin (Ortonne, 19901, the amount of melanin turnover in the eyes of adult vertebrates is completely unknown, although the melanin in the eyes is exposed to an environment that generates H202 (see Bennan, 1979) and radicals (Noell, 1980), which can inteF act with melanin.As far as data were available, the attempt is made in the present study to focus on five points indicating turnover of melanin in the three pigmented eye tissues. bover of melanin may be indicated by: (1) the demonstration of the classical morphological stages of melanogenesis like premelanosomes or early stage melanosomes, (2) the demonstration of active tyrosinase or other melanogenic enzymes, (3) the degradation of melanin granules by macrophages or lysosomes, (4) the repigmentation after injury or age related loss of melanin, or (5) incorporation of Dopa into melanin granules. MELANIN TURNOVER IN THE RETINAL PIGMENT EPITH...

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Section: Morphological Stages Of Melanogenesissupporting

confidence: 75%

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confidence: 99%

Does Melanin Turnover Occur in the Eyes of Adult Vertebrates?

Schraermeyer

1993

Pigment Cell Research

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“…The melanosomal outer layer or membrane was clearly resolved (Figs. 2, 9) in 3-D, confirming earlier reports (Lea et al, 1976;Stanka et al, 1981) of membrane bound melanosomes.…”

Section: Day 9 Rpe (Stage 35)supporting

confidence: 93%

The structure of the developing chick retinal pigment epithelium revealed by high resolution scanning electron microscopy

Weiser

Hollenberg

Mandelcorn

et al. 1991

J. Elec. Microsc. Tech.

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The retinal pigment epithelium (RPE) in the developing eye of chick embryos has been studied during the early stages of development by high resolution scanning electron microscopy (HRSEM). Specimen preparation techniques which involve removal of the cytoplasmic matrix permitted visualization of organelles and other subcellular structures within RPE cells in detail and in three dimensional (3-D) stereo HRSEM. Using this technique, we were able to examine changes in melanosome structures during development and demonstrate that pigmentation in the RPE was present by day 4 of development. RPE plasma cell membranes showed extensive folding of the apical portion of the membrane closest to the developing neural retina by day 9. Examination of RPE photoreceptor junction revealed photoreceptor inner segments by day 6 and an outer segment by day 9. Mitochondria in the RPE were found to contain tubular cristae only. The ultra-structure in 3-D of the Golgi apparatus, smooth and rough endoplasmic reticulum, lysosomes and nuclear chromatin of the RPE, and Bruch's layer was revealed by the HRSEM method.

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“…The classical premelanosome consists of a protein matrix in which melanin is deposited after incorporation of the melanogenetic enzyme tyrosinase into the melanosome [13]. But it has also been shown that melanin can be synthesized from multilamellar bodies [2], from autophagosomes [14] and from heterophagosomes [6].…”

Section: Discussionmentioning

confidence: 99%

Subretinal Injection of Rod Outer Segments Leads to an Increase in the Number of Early-Stage Melanosomes in Retinal Pigment Epithelial Cells

et al. 2000

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Our study was performed to test the hypothesis that subretinally injected protein can induce melanogenesis in the retinal pigment epithelium (RPE). Rod outer segments (ROS) were isolated from cattle eyes and injected into the subretinal space of Long Evans rats. Five days after surgery, the injected eyes were investigated by electron microscopy. The number of early-stage melanosomes and small melanin granules was compared in injected and noninjected eyes. It was found that the injected ROS were phagocytized by the RPE cells, and the number of early-stage melanosomes in the RPE was significantly increased in injected eyes compared to eyes without injection. The ROS-containing endosomes fused with melanolysosomes in which melanogenesis took place. The increased number of early-stage melanosomes indicates new formation of melanin.

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Evidence of membrane transformation during melanogenesis. Electron microscopic study on the retinal pigment epithelium of chick embryos

Cited by 17 publications

References 20 publications

Does Melanin Turnover Occur in the Eyes of Adult Vertebrates?

Does Melanin Turnover Occur in the Eyes of Adult Vertebrates?

The structure of the developing chick retinal pigment epithelium revealed by high resolution scanning electron microscopy

Subretinal Injection of Rod Outer Segments Leads to an Increase in the Number of Early-Stage Melanosomes in Retinal Pigment Epithelial Cells

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