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What can eye muscle studies tell us about strabismus?
Published in Jan-Tjeerd de Faber, 28th European Strabismological Association Meeting, 2020
The altered visual processing in monocular deprivation would be expected to change the firing patterns of oculomotor motoneurons for the slow and sustained types of eye movements, and this would effect EOM fiber development. Cats with defects of binocular vision, due to surgically induced strabismus and monocular occlusion with lid suture from age 2–3 weeks in domestic cats, or to a genetic defect in Siamese (albino) cats, showed slower contractions and lower fatigue resistance of their eye muscles than normal domestic cats (Lennerstrand 1982). No variations in fiber types or in the relative proportions between types were observed. However, fibers of all types were smaller and the capillary density per fibers was lower in cats with binocular defects than in normal cats. The developmental visual insult of monocular deprivation has been shown to interfere with EOM maturation sufficiently to change expression of the typical myosin heavy chain isoforms of the singly innervated orbital fibers (Brueckner & Porter 1998).
The Effects of Resveratrol on the Brain Mitochondria
Published in Shamim I. Ahmad, Handbook of Mitochondrial Dysfunction, 2019
Similarly, Valenti et al. (2016) have found that RES (10 µM for 24 h) rescued neural progenitor cells (NPC) isolated from the dentate gyrus of adult Ts65Dn mice (an animal model of Down syndrome because carry a partial triplication of mouse chromosome 16, which is analogous to the human portion 21q21–21q22.3) [66]. The authors have reported that RES restored mitochondrial function (enzyme activity of the complexes I and V; ATP synthesis) by a mechanism dependent on AMPK, since Compound C suppressed the effects induced by RES. RES also upregulated sirtuin 1 (SIRT1) activity (without altering SIRT1 levels) and the immunocontents of AMPK, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear respiratory factor-1 (NRF-1), mitochondrial transcription factor A (TFAM). The activation of such proteins leads to mitochondrial biogenesis, i.e., the synthesis of new mitochondria [41]. Accordingly, the authors observed that RES treatment enhanced the levels of mitochondrial DNA, as well as the amounts of the complexes I and V in Ts65Dn NPC cells. Thus, RES would be an interesting alternative regarding the treatment of mitochondrial impairment in Down syndrome by modulating mitochondrial biogenesis. In a similar fashion, it was published by another research group that RES (20 µM for 1 h) promoted AMPK activation and upregulation of PGC-1α and NRF-1, causing an increase in the levels of ATP in rat primary visual cortical neurons [67]. In the same work, the authors have found evidence of mitochondrial biogenesis in the visual cortex of rats treated with RES (20 mg/kg.day-1 for 1 week) and subjected to monocular deprivation. RES also activated the AMPK/PGC-1α/NRF-1 axis in vivo, leading to an increase in the number of mitochondria and in the levels of ATP in neurons of the visual cortex. In accordance with this, Peng et al. (2016) have reported that a pretreatment (for 24 h) with RES (60 µM) prevented the rotenone-induced decrease in the levels of ATP in PC12 cells by a mechanism associated with the triggering of mitochondrial biogenesis [68]. RES upregulated PGC-1α and the levels of dynamin-related protein 1 (Drp1), mitochondrial fission 1 (Fis1), optic atrophy 1 (OPA1), and MFN2, consequently enhancing the amount of mitochondrial DNA and mitochondrial mass. An effect of the inhibition of mitochondrial biogenesis on cell survival and mitochondrial function was not tested by the authors. However, data obtained by those research groups confirm that RES can promote mitochondrial biogenesis in brain cells. Moreover, strong evidence points to a role for RES in the maintenance of mitochondrial dynamics, i.e., mitochondrial fusion and fission, in the mechanism of mitochondrial function protection, since the proteins Drp1, Fis1, OPA1, and MFN2 modulate mitochondrial fusion and fission in mammalian cells. OPA1 and MFN2 coordinate mitochondrial fusion, whereas and Drp1 and Fis1 control mitochondrial fission [69–72].
Quantitative Assessment of the Choroidal Vessel Diameter during the Recovery of Form-Deprivation Myopia in Guinea Pigs
Published in Current Eye Research, 2022
Wei Chen, Li Li, Qiang Feng, Chen Xi Li, Yue Zhang, Zhi Wei Li
This study was approved by the Animal Care and Ethics Committee of Tian Jin Eye Hospital, Tianjin, China. The treatment and care of the animals complied with the Association for Research in Vision and Ophthalmology statement for the Use of Animals in Ophthalmic and Vision Research. Forty-eight guinea pigs (3 weeks old) were obtained from the Beijing Keyu Animal Center (Beijing, China). The animals were reared in 12-h light-dark cycles (on at 8:00 am, off at 8:00 pm), with food and water freely available. Form-deprivation (FD) myopia was induced by monocular deprivation using a facemask made of latex (Suzhou, China), which was opaque and soft, with a 60% light transmission. The procedure for preparing and wearing the facemask for 3 weeks over the right eye has been detailed previously.17 Room temperature was maintained at 24 − 26 °C, and animals were monitored three times during the 12-h-light period to ensure that the facemask remained clean and in place. The facemask did not contact the cornea, allowing the right eye to blink freely.
Impact of Amblyopia on the Central Nervous System
Published in Journal of Binocular Vision and Ocular Motility, 2020
Nathaniel P. Miller, Breanna Aldred, Melanie A. Schmitt, Bas Rokers
The visual system is highly sensitive during this critical period, and just a few days of monocular deprivation are sufficient to significantly disrupt neural development. In the LGN, cells responsive to the sutured eye were noticeably smaller than those of the open eye. In striate cortex, direct electrophysiological recordings showed that the number of binocularly responsive cells (and cells showing any responsiveness to the sutured eye) were significantly reduced. Moreover, even if normal binocular visual input was restored after a period of extended deprivation (3 months), these physiological changes were largely irreversible. Thus, while the visual system is highly plastic early in development, in the absence of timely intervention, these early structural changes become permanent.
Imaging Amblyopia: Insights from Optical Coherence Tomography (OCT)
Published in Seminars in Ophthalmology, 2019
Eric D. Gaier, Ryan Gise, Gena Heidary
A handful of recent OCT studies have specifically examined patients with deprivation amblyopia, which often results from a structural anomaly of the anterior segment of the eye such as congenital cataract. Deprivation amblyopia is less common than anisometropic or strabismic amblyopia but tends to be more severe. Anisometropia and strabismus are difficult to model in animals, so monocular deprivation (typically by reversible tarsorrhaphy) has become the most widely studied animal model of amblyopia. As such, comparisons between OCT studies of deprivation amblyopia are most directly comparable to findings in histologic animal studies of amblyopia.