Growth Hormone Localization in the Neural Retina and Retinal Pigmented Epithelium of Embryonic Chicks

Harvey, S.; Kakebeeke, Mia; Sanders, Esmond J.

doi:10.1385/jmn:22:1-2:139

Cited by 23 publications

(7 citation statements)

References 18 publications

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“…Our study is the first to present temporal and spatial regulation of the growth of an organelle. Recent studies have demonstrated that growth hormone (GH), the molecule in mammals mainly responsible for postnatal bone and muscle growth, is synthesized in chick retina and in retinal pigmented epithelial cells (RPE) from early stages of development (Harvey et al,2001,2004; Baudet et al,2003). GH receptor immunoreactivity was also detected in chick retina from E3 (Harvey et al,2001).…”

Section: Discussionmentioning

confidence: 99%

Spatial and temporal patterns of growth and differentiation of cone oil droplets in the chick retina

López

López‐Gallardo

Busturia

et al. 2004

J of Neuroscience Research

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Avian cone photoreceptors have an oil droplet in the outer portion of their inner segment that acts as a long-pass cut-off filter between incident light and visual pigment. Chick cone droplets are mainly red, orange, yellow, green, and colorless, and the colors are due to three carotenoid pigments with characteristic absorption spectra. Little is known of the differentiation of this organelle, the natural marker of cones, and the little that is known is largely controversial. We used flat whole-mounts of fresh retinas to study the time and place of the appearance of droplets, their growth rates, the sequence of droplet color differentiation, and the spatial distribution of these colors. We show that droplet differentiation starts on embryonic Day 10 (E10) in a relatively small area above the optic nerve head. The differentiation spreads to the rest of the retina in a manner similar to that of photoreceptor neurogenesis, with three decreasing gradients of droplet size and color between E13-E20: from central to peripheral, dorsal to ventral, and temporal to nasal. The rate of growth of the droplets was not constant, but showed a maximum between E17 and postnatal Day 1 (P1) in most of the retinal zones. Color differentiation started at E16-E17, 5-6 days after their appearance, when the droplets were already of considerable size. Initially, all droplets were colorless, and then turned pale green or yellow to acquire progressively the mature colors. Differentiation ended in the whole retina by P15, with ventral droplets of larger diameter than dorsal ones, the peripheral ones generally larger than the central ones, and with the color distribution varying with the retinal area. Our results show that growth and color differentiation of the droplets is regulated temporally and spatially, and the cones complete differentiation at P15 rather than at prenatal stages, as is thought generally.

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Section: Discussionmentioning

confidence: 99%

Spatial and temporal patterns of growth and differentiation of cone oil droplets in the chick retina

López

López‐Gallardo

Busturia

et al. 2004

J of Neuroscience Research

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“…Moreover, after secretion from the retina, this GH moiety is bound to a 45-kDa proteoglycan, opticin, in vitreous fluid [37]. GH immunoreactivity within the eye is also found in the choroid layer and in the retinal pigmented epithelium [38,39].…”

Section: Neural Retinamentioning

confidence: 99%

Extrapituitary growth hormone

Harvey

2010

Endocr

109

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Pituitary somatotrophs secrete growth hormone (GH) into the bloodstream, to act as a hormone at receptor sites in most, if not all, tissues. These endocrine actions of circulating GH are abolished after pituitary ablation or hypophysectomy, indicating its pituitary source. GH gene expression is, however, not confined to the pituitary gland, as it occurs in neural, immune, reproductive, alimentary, and respiratory tissues and in the integumentary, muscular, skeletal, and cardiovascular systems, in which GH may act locally rather than as an endocrine. These actions are likely to be involved in the proliferation and differentiation of cells and tissues prior to the ontogeny of the pituitary gland. They are also likely to complement the endocrine actions of GH and are likely to maintain them after pituitary senescence and the somatopause. Autocrine or paracrine actions of GH are, however, sometimes mediated through different signaling mechanisms to those mediating its endocrine actions and these may promote oncogenesis. Extrapituitary GH may thus be of physiological and pathophysiological significance.

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“…Studies in the developing chicken retina have localised GH to the cytoplasm of retinal ganglion cells and membranes of melanin granules [127]. IGF-I and GH have been reported to stimulate the proliferation of retinal progenitors in goldfish [121] and teleost [128,129] retina and IGF-I is neurogenic at the margin of the post-natal chicken retina [130].…”

Section: Gh and Igf-i And Neuro-genesis And Neuro-protectionmentioning

confidence: 99%

The Role of Growth Hormone, Insulin-Like Growth Factor and Somatostatin in Diabetic Retinopathy

Wilkinson-Berka¹,

Wraight²,

Werther³

2006

CMC

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Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are implicated in the aberrant cell growth and pathological neovascularization that characterises proliferative diabetic retinopathy. While serum levels of IGF-I are reported to be either high or low in diabetic patients, there is evidence that local tissue levels of IGF-I may be more relevant to diabetic retinal pathology. IGF-I and IGF binding proteins (IGFBP) are expressed throughout the retina in vascular, neuronal and glial cells, and are altered in response to hyperglycaemia and hypoxia. Further support for a pathological role for local IGF-I comes from studies showing IGF-I to be increased in the vitreal fluids of patients with proliferative diabetic retinopathy. IGF-I may exert its cell growth promoting properties by stimulating a number of pathways including protein-kinase B (Akt), nuclear factor kB (NF-kappaB)/AP-1 and hypoxic-inducible factor-1alpha (HIF-1alpha). In addition, other growth factors may participate in IGF-I induced cell growth including vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF) and fibroblast growth factor (FGF). The importance of the GH/IGF system in diabetic retinopathy and retinal neovascularization has been highlighted by the use of agents that inhibit the system. GH receptor antagonists, GH receptor antisense oligonucleotides, somatostatin analogues and receptor neutralising antibodies to IGF-I reduce hypoxic-induced retinal neovascularization. These approaches may also prove to have benefits for improving vascular patency and vision in patients with diabetic retinopathy.

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Growth Hormone Localization in the Neural Retina and Retinal Pigmented Epithelium of Embryonic Chicks

Cited by 23 publications

References 18 publications

Spatial and temporal patterns of growth and differentiation of cone oil droplets in the chick retina

Spatial and temporal patterns of growth and differentiation of cone oil droplets in the chick retina

Extrapituitary growth hormone

The Role of Growth Hormone, Insulin-Like Growth Factor and Somatostatin in Diabetic Retinopathy

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