Glucagon Receptor Agonists and Antagonists Affect the Growth of the Chick Eye: A Role for Glucagonergic Regulation of Emmetropization?

Vessey, Kirstan A.; Lencses, Kathy A.; Rushforth, David; Hruby, Victor J.; Stell, William K.

doi:10.1167/iovs.04-1026

Cited by 55 publications

(46 citation statements)

References 36 publications

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“…The same retina-derived cues that regulate the growth of the posterior chamber of the eye have been shown to regulate the proliferation of CMZ progenitors (Fischer, 2005). Glucagon-expressing retinal amacrine cells are known to regulate ocular growth in post-hatch chicks (Fischer et al, 1999;Vessey et al, 2005) (Bitzer and Schaeffel, 2002;Feldkaemper and Schaeffel, 2002). Interestingly, glucagon-containing neurites are heavily clustered within the CMZ and many of these neurites originate from distinct types of retinal neurons (Fischer, 2005).…”

Section: Vision-guided Retinal Growthmentioning

confidence: 99%

The ciliary marginal zone (CMZ) in development and regeneration of the vertebrate eye

Fischer

Bosse

El‐Hodiri

2013

Experimental Eye Research

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Section: Vision-guided Retinal Growthmentioning

confidence: 99%

The ciliary marginal zone (CMZ) in development and regeneration of the vertebrate eye

Fischer

Bosse

El‐Hodiri

2013

Experimental Eye Research

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“…[12][13][14] The expression of Egr1 by glucagonergic retinal neurons is believed to influence glucagon synthesis and release. [11][12][13]15,16 However, definitive evidence of the direct transcriptional regulation of glucagon by Egr1 is lacking. Further-more, the downstream targets of retinal glucagon that regulate ocular growth remain uncertain, in part because the expression of glucagon receptors appears to be nearly ubiquitous across ocular tissues.…”

Section: Myopia and Vision-guided Ocular Growthmentioning

confidence: 99%

Müller Glia, Vision-Guided Ocular Growth, Retinal Stem Cells, and a Little Serendipity

Fischer

2011

Invest. Ophthalmol. Vis. Sci.

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Hypothesis-driven science is expected to result in a continuum of studies and findings along a discrete path. By comparison, serendipity can lead to new directions that branch into different paths. Herein, I describe a diverse series of findings that were motivated by hypotheses, but driven by serendipity. I summarize how investigations into vision-guided ocular growth in the chick eye led to the identification of glucagonergic amacrine cells as key regulators of ocular elongation. Studies designed to assess the impact of the ablation of different types of neurons on vision-guided ocular growth led to the finding of numerous proliferating cells within damaged retinas. These proliferating cells were Müller glia-derived retinal progenitors with a capacity to produce new neurons. Studies designed to investigate Müller glia-derived progenitors led to the identification of a domain of neural stem cells that form a circumferential marginal zone (CMZ) that lines the periphery of the retina. Accelerated ocular growth, caused by visual deprivation, stimulated the proliferation of CMZ progenitors. We formulated a hypothesis that growth-regulating glucagonergic cells may regulate both overall eye size (scleral growth) and the growth of the retina (proliferation of CMZ cells). Subsequent studies identified unusual types of glucagonergic neurons with terminals that ramify within the CMZ; these cells use visual cues to control equatorial ocular growth and the proliferation of CMZ cells. Finally, while studying the signaling pathways that stimulate CMZ and Müller glia-derived progenitors, serendipity led to the discovery of a novel type of glial cell that is scattered across the inner retinal layers. (Invest Ophthalmol Vis Sci. 2011;52:7705-7710)

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“…Thereafter, chicks were sacrificed using highdose pentobarbital anesthesia. Extraneous orbital tissues were removed from the eyes and ocular lengths were measured manually using digital calipers [30,31] .…”

Section: Measurement Of Globe Component Dimensionsmentioning

confidence: 99%

Effect of Black-Currant Extract on Negative Lens-Induced Ocular Growth in Chicks

Iida¹,

Nakamura²,

Matsumoto³

et al. 2010

Ophthalmic Res

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Aim: To evaluate the effects of orally administered black-currant (BC) extract on the enlargement of globe component dimensions induced in chicks by wearing negative lenses. Methods: Negative lenses (–8 D) were worn on the right eyes by 8-day-old chicks, and their fellow eyes acted as controls. BC extract and distilled water (vehicle control) were orally administered once a day for 3 days. To confirm the effect of BC anthocyanins (BCAs), they were intravenously administered once a day for 3 days. Dimensions of globe components of right eyes and fellow eyes were measured with an A-scan ultrasound instrument on the third day (day 4) after placement of the negative lenses. Results: Orally administered BC extract significantly inhibited enlargement of vitreous-chamber depth, axial and ocular lengths in a dose-dependent manner when compared to controls. Intravenously administered BCAs also inhibited elongation of vitreous-chamber depth and axial length when compared to controls. Conclusions: This is the first evidence that BC extract and BCAs could inhibit enlargement of globe component dimensions in a negative lens-induced chick myopia model.

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Glucagon Receptor Agonists and Antagonists Affect the Growth of the Chick Eye: A Role for Glucagonergic Regulation of Emmetropization?

Cited by 55 publications

References 36 publications

The ciliary marginal zone (CMZ) in development and regeneration of the vertebrate eye

The ciliary marginal zone (CMZ) in development and regeneration of the vertebrate eye

Müller Glia, Vision-Guided Ocular Growth, Retinal Stem Cells, and a Little Serendipity

Effect of Black-Currant Extract on Negative Lens-Induced Ocular Growth in Chicks

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