Hypothetical ribbon structure of human γD crystallin showing the location of the four intrinsic tryptophans at positions 43, 69, 131, and 157. The structure was determined by homology modeling threading the HγD-Crys with the known bovine γ crystallin structures (Peitsch 1995, 1996; Guex and Peitsch 1997). The structure is shown from the side (A) and the top (B).
"This is an elegant and immensely satisfying book on the anatomy and functioning of the human eye. Its breadth and depth make it appropriate for both vision practitioners and upper undergraduates and graduate students interested in vision research. This is a landmark book on the eye which belongs in every biological, optometric and ophthalmological library." --Howard C. Howland, The Quarterly Review of Biology
The Human Eye Structure And Function Oyster Pdf 12
Nevertheless, eye's design is not as simple as one may think. The lens can be modelled as a cemented triplet; i.e. the biconvex nucleus sandwiched by two cortical meniscus. In addition, the lens surfaces are highly aspherical (hyperbolas) and the lens cortex has a GRIN structure. Therefore the complexity of the human lens could be comparable to the second group of lenses of the examples. We can apply a similar reasoning to the corneal meniscus. It would be equivalent to a group of lenses in an artificial design because of its aspheric surfaces (and absence of correction of CA.)
As an ecosystem engineer, oysters provide supporting ecosystem services, along with provisioning, regulating and cultural services. Oysters influence nutrient cycling, water filtration, habitat structure, biodiversity, and food web dynamics.[27] Assimilation of nitrogen and phosphorus into shellfish tissues provides an opportunity to remove these nutrients from the water column.[28][29][30] In California's Tomales Bay, native oyster presence is associated with higher species diversity of benthic invertebrates.[31][32] The ecological and economic importance of oyster reefs has become more acknowledged, restoration efforts have increased.[15]
The "oyster-tecture" movement promotes the use of oyster reefs for water purification and wave attenuation. An oyster-tecture project has been implemented at Withers Estuary, Withers Swash, South Carolina, by Neil Chambers-led volunteers, at a site where pollution was affecting beach tourism.[45] Currently, for the installation cost of $3000, roughly 4.8 million liters of water are being filtered daily. In New Jersey, however, the Department of Environmental Protection refused to allow oysters as a filtering system in Sandy Hook Bay and the Raritan Bay, citing worries that commercial shellfish growers would be at risk and that members of the public might disregard warnings and consume tainted oysters. New Jersey Baykeepers responded by changing their strategy for utilizing oysters to clean up the waterway, by collaborating with Naval Weapons Station Earle. The Navy station is under 24/7 security and therefore eliminates any poaching and associated human health risk.[46] Oyster-tecture projects have been proposed to protect coastal cities, such as New York, from the threat of rising sea levels due to climate change.[47] Additionally Oyster reef restoration has shown to increase the population of oyster beds within the oceans while also conservating the biolife within the oyster reefs.
The accidental or intentional introduction of species by humans has the potential to negatively impact native oyster populations. For example, non-native species in Tomales Bay have resulted in the loss of half of California's Olympia oysters.[48]
Oyster depuration begins after the harvest of oysters from farmed locations. The oysters are transported and placed into tanks pumped with clean water for periods of 48 to 72 hours. The holding temperatures and salinity vary according to species. The seawater that the oysters were originally farmed in does not remain in the oyster, since the water used for depuration must be fully sterilized, plus the depuration facility would not necessarily be located near the farming location.[69] Depuration of oysters can remove moderate levels of contamination of most bacterial indicators and pathogens. Well-known contaminants include Vibrio parahaemolyticus, a temperature-sensitive bacterium found in seawater animals, and Escherichia coli, a bacterium found in coastal waters near highly populated cities having sewage systems discharging waste nearby, or in the presence of agricultural discharges.[citation needed] Depuration expands beyond oysters into many shellfish and other related products, especially in seafood that is known to come from potentially polluted areas; depurated seafood is effectively a product cleansed from inside-out to make it safe for human consumption.
Some oysters also harbor bacterial species which can cause human disease; of importance is Vibrio vulnificus, which causes gastroenteritis, which is usually self-limiting, and cellulitis. Cellulitis can be severe and rapidly spreading, requiring antibiotics, medical care, and in some severe cases amputation. It is usually acquired when the contents of the oyster come in contact with a cut skin lesion, as when shucking an oyster.
1. Oyster CW. The iris and pupil. In: Oyster CW. The human eye structure and function. Sunderland, Mass.: Sinauer Ass Inc.; 1999:411-46.2. Lehto KS, Sulander PO, Tervo TM. Do motor vehicle airbags increase risk of ocular injuries in adults? Ophthalmology. 2003 Jun;110(6):1082-8.3. García-Medina JJ, García-Medina M, Pinazo-Durán MD. Severe orbitopalpebral emphysema after nose blowing requiring emergency decompression. Eur J Ophthalmol. 2006 Mar-Apr;16(2):339-42.4. Morris DS. Ocular blunt trauma: loss of sight from an ice hockey injury. Br J Sports Med. 2006 Mar;40(3):e5.5. Vize CJ, Gauba V, Atkinson PL. Eye injury as a result of coat toggle trauma. Eye (Lond). 2007 Jan;21(1):94-5.6. Wong MH, Yang M, Yeo KT. Elastic cord-related ocular injury. Singapore Med J. 2008 Apr;49(4):e90-2.7. Oyster CW. The limbus and the anterior chamber. In: Oyster CW. The human eye structure and function. Sunderland, Mass.: Sinauer Ass Inc.; 1999:379-410.8. Ahmad F, Kirkpatrick NA, Lyne J, et al. Buckling and hydraulic mechanisms in orbital blowout fractures: fact or fiction? J Craniofac Surg. 2006 May;17(3):438-41.9. Ellong A, Ebana Mvogo C, Nyouma Moune E, et al. Post-traumatic glaucoma with irido-corneal angle injuries in Cameroon. Bull Soc Belge Ophtalmol. 2005;(298):21-8.10. Manners T, Salmon JF, Barron A, et al. Trabeculectomy with mitomycin C in the treatment of post-traumatic angle recession glaucoma. Br J Ophthalmol. 2001 Feb;85(2):159-63.11. Sihota R, Kumar S, Gupta V, et al. Early predictors of traumatic glaucoma after closed globe injury: trabecular pigmentation, widened angle recess, and higher baseline intraocular pressure. Arch Ophthalmol. 2008 Jul;126(7):921-6.12. Walker NJ, Foster A, Apel AJ. Traumatic expulsive iridodialysis after small-incision sutureless cataract surgery. J Cataract Refract Surg. 2004 Oct;30(10):2223-4.13. Bardak Y, Ozerturk Y, Durmus M, et al. Closed chamber iridodialysis repair using a needle with a distal hole. J Cataract Refract Surg. 2000 Feb;26(2):173-6.14. Richards JC, Kennedy CJ. Sutureless technique for repair of traumatic iridodialysis. Ophthalmic Surg Lasers Imaging. 2006 Nov-Dec;37(6):508-10.
Understanding the roles of genetic divergence and phenotypic plasticity in adaptation is central to evolutionary biology and important for assessing adaptive potential of species under climate change. Analysis of a chromosome-level assembly and resequencing of individuals across wide latitude distribution in the estuarine oyster (Crassostrea ariakensis) revealed unexpectedly low genomic diversity and population structures shaped by historical glaciation, geological events and oceanographic forces. Strong selection signals were detected in genes responding to temperature and salinity stress, especially of the expanded solute carrier families, highlighting the importance of gene expansion in environmental adaptation. Genes exhibiting high plasticity showed strong selection in upstream regulatory regions that modulate transcription, indicating selection favoring plasticity. Our findings suggest that genomic variation and population structure in marine bivalves are heavily influenced by climate history and physical forces, and gene expansion and selection may enhance phenotypic plasticity that is critical for the adaptation to rapidly changing environments.
While genetic changes can be inferred with genetic markers, whole-genome analysis is essential for exploring all genetic variation and identifying genes and selection events that are critical for adaption. Using multi-omic analyses, we previously showed that the Pacific oyster has a highly polymorphic genome with extensive expansion of environment-responsive genes, and plasticity is positively correlated with local adaptation12,23. In this study, we produced a chromosome-level assembly of the estuarine oyster genome, re-sequenced 264 wild oysters collected from 11 estuaries, and conducted transcriptomic studies of environmental response to understand its genetic variation, population structure, phenotypic plasticity and genomic signatures of selection or bottleneck that may be linked to environmental changes. Our results show that the estuarine oyster has significantly lower genetic diversity than its sister-species probably due to the impact of past glaciation on its unique estuarine lifestyle. Its population structure is heavily influenced by geological events and ocean currents. Expansion and selection in regulatory regions of environment-responsive genes may enhance phenotypic plasticity that is critical for the adaptation to rapidly changing environments. 2ff7e9595c
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