Effect of dark and light adaptation on the retina and pecten of chicken.
ABSTRACT Retinae and pecten oculi of chickens were studied after 30 days of dark and light adaptation. Biochemically, glycogen and alkaline phosphatase activity increased 24 and 6%, respectively, in retina on dark adaptation, and decreased 15 and 17%, respectively, on light adaptation. Retinal RNA content increased 11% on light adaptation. DNA remained unaffected on dark and light adaptation of the retina. Alkaline phosphatase activity of pecten decreased 25% on dark adaptation.Histochemically, glycogen-rich paraboloids of accessory cones and hyperboloids of rods of the retina atrophied when subjected to light and hypertrophied on dark adaptation. On light adaptation, except for the outer plexiform layer, the alkaline phosphatase activity was negligible. Possible significance of these results in relation to sensory functions of the retina and retina-pecten interrelationship is discussed.
Full-textDOI: · Available from: Rakesh Yashroy, Jun 30, 2015
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ABSTRACT: Pigments serve many visually obvious animal functions (e.g. hair, skin, eyes, feathers, scales). One is 'melanin', unusual in an absorption across the UV-visual spectrum which is controversial. Any polymer or macro-structure of melanin monomers is 'melanin'. Its roles derive from complex structural and physical-chemical properties e.g. semiconductor, stable radical, conductor, free radical scavenger, charge-transfer. Clinicians and researchers are well acquainted with melanin in skin and ocular pathologies and now increasingly are with internal, melanized, pathology-associated sites not obviously subject to light radiation (e.g. brain, cochlea). At both types of sites some findings puzzle: positive and negative neuromelanin effects in Parkinsons; unexpected melanocyte action in the cochlea, in deafness; melanin reduces DNA damage, but can promote melanoma; in melanotic cells, mitochondrial number was 83% less, respiration down 30%, but development similar to normal amelanotic cells. A little known, avian anatomical conundrum may help resolve melanin paradoxes. One of many unique adaptations to flight, the pecten, strange intra-ocular organ with unresolved function(s), is much enlarged and heavily melanized in birds fighting gravity, hypoxia, thirst and hunger during long-distance, frequently sub-zero, non-stop migration. The pecten may help cope with energy and nutrient needs under extreme conditions, by a marginal but critical, melanin-initiated conversion of light to metabolic energy, coupled to local metabolite recycling. Similarly in Central Africa, reduction in body hair and melanin increase may also have lead to 'photomelanometabolism' which, though small scale/ unit body area, in total may have enabled a sharply increased development of the energy-hungry cortex and enhanced human survival generally. Animal inability to utilize light energy directly has been traditionally assumed. Melanin and the pecten may have unexpected lessons also for human physiology and medicine.Medical Hypotheses 02/2008; 71(2):190-202. DOI:10.1016/j.mehy.2008.03.038 · 1.15 Impact Factor
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ABSTRACT: The pecten oculi is a highly vascularized and pigmented organ that overlies the optic disc and projects into the vitreous body in the avian eye. First reported over 300 years ago, its function(s) remains a puzzle to ornithologists, ophthalmologists and anatomists. Morphometric study of this unique organ was undertaken in birds exhibiting apparently different visual acuities, namely two species of diurnal birds (the ground-dwelling domestic fowl Gallus gallus var. domesticus and a highly active predator bird, the black kite (Milvus migrans) and a nocturnal bird (the spotted-eagle owl Bubo bubo africanus). The volume of the owl's eye was 4.8 and 2.2 times larger than that of the fowl and the kite, respectively. However, the pecten of the fowl consisted of more pleats (16–18) compared to the kite (12–13) and the owl (5–6). The volume of the pecten of the kite was 1.4 and 2.7 times larger than that of the fowl and the owl, respectively (P < 0.05). Similarly, the surface area of the pecten of the kite was 2.6 and 4 times larger than that of the fowl and owl, respectively (P < 0.05). The volume density of blood vessels (lumen and wall) in the pecten of the kite, fowl and owl comprised 67.7%, 66.9% and 62.6%, respectively, the pigmented tissue constituting the rest. Both the volume density and the volume of the blood in the pecten were higher in the diurnal birds (kite, fowl) than the owl (P < 0.05). The surface area of the capillary luminal surface was 1.7 and 5.3 times higher in the kite than in the fowl and the owl, respectively (P < 0.05). These results suggest that the functional morphology of the pecten correlates with the life-style of the bird and with functional need, and lends further support to the nutritive role of the pecten.Journal of Zoology 01/2001; 254(4):521-528. DOI:10.1017/S0952836901001029 · 1.95 Impact Factor
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ABSTRACT: Chickens were adapted to dark and light for 30 days and their retinas were studied in comparison to the chickens kept in normal environments. Total phospholipid content and cholinesterase activity were determined biochemically in the retinas of each group of animals. An increase of approximately 22% was observed in the phospholipid content of the dark adapted retinas, whereas the light adapted retinas showed no significant change in comparison with the normal counterparts. Retinal cholinesterase activity decreases by about 64% on dark adaptation and increases by about 14% on light adaptation.Acta ophthalmologica 02/1972; 50(4):583-8. DOI:10.1111/j.1755-3768.1972.tb05988.x · 2.51 Impact Factor
Questions & Answers about this publication
- Are rods and cones in retina the most neatly compartmentalized cells of the animal/human body? Linear compartmentalization of rods and cones into light-absorptive outer segments with schematically organized inner segments containing portions of refractive oil-droplets, ellipsoids (mitochondria), energy deposits (glycogen paraboloids), Nissl body (endoplasmic ret), nucleolus and cell endings in synaptic body.Following