Metamorphoses

Thorium isotope concentrations and ratios, as well as parent and daughter isotope concentrations, are used to date and study the formation and metamorphosis of rocks and sediments. For example, has been used to date coral reef terraces (4). / Th disequiUbria and Th/ Th... 

The amphibian metamorphosis test is based on the abiUty of thyroid hormones to induce precocious transformation of a tadpole into a frog or of the axolod into a salamander. It is rarely used because of solubiUty problems and the difficulty of applying the results to humans. 

Vitamin A [79-80-1] (6) is stmcturaHy similar to vitamin A [68-26-8] and is also found in fish oils. This compound is important biologically for fish and other lower animals. Interestingly, tadpoles require vitamin A but after metamorphosis require vitamin A (8). 

The idea of red cell substitutes is not new. In Ovid s Metamorphosis the witch Medea restored Jason s aged father, Aeson, by slitting his throat to let out old blood, replacing it with a magic brew she had concocted (1). Sir Christopher Wren was one of the first to apply the new knowledge about circulation to blood substitutes. In 1656 he infused ale, wine, scammony, and opium into dogs and from these efforts conceived the ideal of transfusing blood from one animal to another. Lower actually carried out the first transfusion experiments (2). 

Thrombin, the two-chain derivative of the prothrombin molecule, has a molecular weight of approximately 37,000 daltons. Its proteolytic properties induce the conversion of fibrinogen to fibrin to produce the initial visible manifestation of coagulation, the soluble fibrin clot. In addition, thrombin influences the activity of Factors V, VIII, and XIII and plasmin. Thrombin affects platelet function by inducing viscous metamorphosis and the release reaction with subsequent aggregation. 

Rats exposed to 1000 ppm of vapors for 4—7 h/d for eight days showed ataxia, decreased body weight and growth rate, and minimal central fatty metamorphosis of the Hver (119). Trichloroethanol and trichloroacetic acid were urinary metaboHtes. Tetrachloroethylene did not show any of these effects. 

Frog metamorphosis assay rate of tail resorption in Xenopus laevis. 

Cyprid major protein is a larval storage protein necessary for successful metamorphosis. " Production of cyprid major protein was increased in the barnacle Balanus amphitrite following exposure to both nonylphenol and estradiol, suggesting that it may be a potential biomarker of estrogen exposure in invertebrates such as barnacles. " "... 

Disruption of thyroid functions in vertebrates has been suggested to constitute a potential threat to many vital functions. For example, there is a possibility that disruption to the thyroid hormone levels during embryogenesis could result in disturbed behaviour patterns in the adult form, possibly interfering with migration in certain species and sonar functions in cetaceans. In anurans, thyroid hormones are essential for initiating metamorphosis. ... 

Amphibians. Amphibians are highly susceptible to endocrine disruption during development of the larval form and during metamorphosis. The action of metamorphosis is triggered and controlled by the thyroid gland via an increase in triiodothyronine and a decrease in thyroxine, and differs greatly between oviparous and viviparous species. Experimentally, it has been shown that disruption during this sensitive period can lead to malformations and adverse impacts on immune and reproductive functions. 

Amphibians. Immunosuppression has been shown to occur during metamorphosis in several amphibians, and appears to be hormonally regulated. The disappearance of 11 populations of toad from Colorado was associated with immune suppression, and frog mortalities have been associated with infection by a commonly occurring bacteria, Aeromonas hydrophila the cause of the immunosuppression in these animals has not been elucidated. " ... 

Anise swallowtail butterfly (Papilio zelicans) with its pupal ease. Metamorphosis of butterflies is a dramatie example of metabolie ehange. ( Q 1986 Peter Bryant/Bioto cat Photo Service)... 

Pteridine, pyrimidine, pyrrole, and imidazole derivatives as natural compounds of marine origin influencing larval settlements and metamorphosis of marine sessile organisms 99YZ457. 

Umwandltmg, /. conversion, transformation, change transmutation metamorphosis (GrammaT) inflection. 

Wandler, m. transformer converter. Wandlung,/. transformation, change, metamorphosis. 

Freeman, G., and Ridgway, E. B. (1987). Endogenous photoproteins, calcium channels and calcium transients during metamorphosis in hydrozoans. Roux s Arch. Dev. Biol. 196 30-50. 

Carlsson, G., Kulkami, P, and Larsson, P. et al. (2007). Distribution of BDE-99 and effects on metamorphosis of BDE-99 and-47 after oral exposure in Xenopus tropicalis. Aquatic Toxicology 84, 71-79. 

Coady, K.K., Murphy, M.B., and Villeneuve, D.L. et al. (2004). Effects of atrazine on metamorphosis, growth, and gonadal development in the green frog (Rana clamitans). Journal of Toxicology and Environmental Health, Part A Current Issues 67, 941-957. 

Gutleb, A.C., Appehnan, J., and Bronkhorst, M. et al. (2000). Effects of oral exposure to polychlorinated biphenyls (PCBs) on the development and metamorphosis of two amphibian species (Xenopus laevis and Rana temporaria). Science of the Total Environment 262, 147-157. 

Gutleb, A.C., Schriks, M., and Mossink, L. et al. (2007). A synchronized amphibian metamorphosis assay as an improved tool to detect thyroid hormone disturbance by endocrine disrupters and apolar sediment extracts. Chemosphere 70, 93-100. 

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