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Zenk myopia

Ayse Idil Cakmak, Hikmet Basmak, Huseyin Gursoy, Mete Ozkurt, Nilgun Yildirim, Nilufer Erkasap, Mustafa Deger Bilgec, Nese Tuncel, Ertugrul Colak
AIM: To investigate the role of vasoactive intestinal peptide (VIP) in form-deprivation myopia (FDM). METHODS: FDM was created in three groups of eight chicks by placing a translucent diffuser on their right eyes. Intravitreal injections of saline and VIP were applied once a day into the occluded eyes of groups 2 and 3, respectively. Retinoscopy and axial length (AL) measurements were performed on the first and 8(th) days of diffuser wear. The retina mRNA levels of the VIP receptors and the ZENK protein in right eyes of the three groups and left eyes of the first group on day 8 were determined using real time polymerase chain reaction (PCR)...
2017: International Journal of Ophthalmology
Weizhong Lan, Zhikuan Yang, Marita Feldkaemper, Frank Schaeffel
High ambient illuminances have been found to slow the development of deprivation myopia in several animal models. Almost complete inhibition of myopia was observed in chickens when intermittent episodes of high illuminance were alternated with standard office illuminance (50% duty cycle, alternate periods of 1 min 15,000 lux and 1 min 500 lux, continued for 10 h per day), or when illuminances were increased to 40,000 lux. Since the mechanisms by which bright light suppresses myopia are poorly understood, we have studied the roles of two well-established signaling molecules in myopia, dopamine and ZENK, in the chicken...
April 2016: Experimental Eye Research
Marita Feldkaemper, Frank Schaeffel
A large body of data is available to support the hypothesis that dopamine (DA) is one of the retinal neurotransmitters involved in the signaling cascade that controls eye growth by vision. Initially, reduced retinal DA levels were observed in eyes deprived of sharp vision by either diffusers ("deprivation myopia", DM) or negative lenses ("lens induced myopia", LIM). Simulating high retinal DA levels by intravitreal application of a DA agonist can suppress the development of both DM and LIM. Also more recent studies using knock-out mouse models of DA receptors support the idea of an association between decreased DA levels and DM...
September 2013: Experimental Eye Research
Regan Ashby, Peter Kozulin, Pam L Megaw, Ian G Morgan
PURPOSE: To examine in detail the time-course of changes in Zif268, Egr-1, NGFI-A, and Krox-24 (ZENK) and pre-proglucagon (PPG) RNA transcript levels in the chick retina during periods of increased ocular growth induced by form-deprivation and negative-lens wear. To further elucidate the role of ZENK in the modulation of ocular growth, we investigated the effect of intravitreal injections of the muscarinic antagonist atropine and the dopamine agonist 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide (ADTN), both of which block the development of experimental myopia, on the expression of ZENK in eyes fitted with negative-lenses...
2010: Molecular Vision
Wolfgang A Pfaeffl, Miriam Kunze, Ulrich Zenk, Matthias B Pfaeffl, Tibor Schuster, Chris Lohmann
PURPOSE: To evaluate possible factors responsible for the difference between predicted and measured parameters during 100 microm flap creation with a femtosecond laser (IntraLase FS30) using online optical coherence pachymetry (OCP). SETTING: AugenVersorgungsZentrum, Weilheim, and the Technical University of Munich, Munich, Germany. METHODS: In this nonrandomized prospective interventional case study, 287 eyes of 146 consecutive patients were monitored by online OCP before and after flap creation with the femtosecond laser...
November 2008: Journal of Cataract and Refractive Surgery
Marita P Feldkaemper, Irina Neacsu, Frank Schaeffel
PURPOSE: In animal models, it has been shown that the retina can use the defocus of the projected image to control emmetropization. Glucagon may be involved in the sign of defocus detection, at least in chickens. Since glucagon and insulin often have opposite effects in metabolic pathways, the effect of insulin on eye growth was investigated. METHODS: Chicks were treated with either positive or negative spectacle lenses and intravitreally injected with saline or different amounts of insulin...
January 2009: Investigative Ophthalmology & Visual Science
Regan Ashby, C Siobhan McCarthy, Ryszard Maleszka, Pam Megaw, Ian G Morgan
Increases in the expression of the immediate early gene ZENK in the retina, measured by changes in the levels of mRNA and protein immunoreactivity, are amongst the most rapid responses so far measured to conditions that decrease the rate of eye growth in chickens. Our aim was to determine whether atropine, a muscarinic cholinergic antagonist, and 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide, a dopamine agonist, which are known to block excessive eye growth, produce similar changes in ZENK expression...
July 2007: Experimental Eye Research
Ruth Schippert, Eva Burkhardt, Marita Feldkaemper, Frank Schaeffel
PURPOSE: Experiments in chickens have implicated the transcription factor ZENK (also known as Egr-1, NGFI-A, zif268, tis8, cef5, and Krox24) in the feedback mechanisms for visual control of axial eye growth and myopia development. ZENK is upregulated in retinal glucagon amacrine cells when axial eye growth is inhibited by positive spectacle lens wear and is downregulated when it is enhanced by negative spectacle lens wear, suggesting that ZENK may be linked to an inhibitory signal for axial eye growth...
January 2007: Investigative Ophthalmology & Visual Science
Ute Mathis, Frank Schaeffel
BACKGROUND: In chickens, retinal glucagon amacrine cells play an important role in emmetropization, since they express the transcription factor ZENK (also known as NGFI-A, zif268, tis8, cef5, Krox24) in correlation with the sign of imposed image defocus. Pharmacological studies have shown that glucagon can act as a stop signal for axial eye growth, making it a promising target for pharmacological intervention of myopia. Unfortunately, in mammalian retina, glucagon itself has not yet been detected by immunohistochemical staining...
February 2007: Graefe's Archive for Clinical and Experimental Ophthalmology
Michaela Bitzer, Beatrix Kovacs, Marita Feldkaemper, Frank Schaeffel
Muscarinic antagonists, particularly atropine, can inhibit myopia development in several animal models and also in children. However, the biochemical basis of the inhibition of axial eye growth remains obscure, and there are doubts whether muscarinic receptors are involved at all. Experiments in chickens and monkeys have shown that the synthesis of the transcription factor ZENK, also named Egr-1, in retinal glucagon amacrine cells is strongly associated with inhibition of axial eye growth (assumed to create a STOP signal)...
March 2006: Experimental Eye Research
Michaela Bitzer, Frank Schaeffel
PURPOSE: Expression of the transcription factor ZENK in glucagon amacrine cells of the chicken retina is enhanced after treatment with positive spectacle lenses and reduced after treatment with negative lenses. ZENK may, therefore, have an important role in emmetropization. To learn more about its regulation, we have studied its expression after retinal intoxication with quisqualic acid (QA, a glutamatergic excitotoxin). METHODS: Lenses of either +7 or -7 D power were placed in front of the eyes of young chickens 6 days after intravitreal QA injections...
February 2004: Optometry and Vision Science: Official Publication of the American Academy of Optometry
Ian G Morgan
Myopia is among the most common refractive errors and is associated with the greatest risk of pathological outcomes. Most animals, including humans, are born with hyperopic errors. During development, axial elongation of the eye occurs and is regulated through a vision-dependent process, known as emmetropisation The extremely rapid changes in the prevalence of myopia and the dependence of myopia on the level of education indicate that there are very strong environmental impacts on the development of myopia...
September 2003: Clinical & Experimental Optometry: Journal of the Australian Optometrical Association
Marita P Feldkaemper, Frank Schaeffel
Eye growth and refraction are regulated by visual processing in the retina. Until now, the messengers released by the retina to induce these changes are largely unknown. Previously, it was found that glucagon amacrine cells respond to defocus in the retinal image and even to its sign. The expression of the immediate-early gene product ZENK increased in this cell population in eyes wearing plus lenses and decreased in minus lens-treated chicks. Moreover, it was shown that the amount of retinal glucagon mRNA increased during treatment with positive lenses...
November 2002: Visual Neuroscience
M Bitzer, M Feldkaemper, F Schaeffel
Eye growth is visually regulated via messengers that are released from the retina. The retina involves a yet unknown algorithm to analyse the projected image so that the appropriate growth rates for the back of the eye are ensured. One biochemical candidate that could act as a growth controller, is retinoic acid (RA). Previous work (Seko, Shimokawa and Tokoro, 1996; Mertz et al., 1999) has shown that retinal and choroidal RA levels are indeed predictably changed by visual conditions that cause myopia or hyperopia, respectively...
January 2000: Experimental Eye Research
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