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The Effect Of Thyroid Hormone On The Expression Of A7 Myosin Heavy Chain Mrna In Xenopus Laevis, Bradley Thomas Butkovich

Master's Theses

It has long been known that thyroid hormone (TH) is responsible for metamorphosis in tadpoles. It is also known that A7 MHC, an adult muscle isoform, is expressed in adult Xenopus laevis frogs, but not in larvae. Furthermore, the appearance of A7 corresponds with the onset of metamorphosis. The present study investigated the relationship between TH and the expression of A7 MHC mRNA in Xenopus laevis. Isolated tails in culture and 6-n-propyl 2-thiouracil (PTU) treated tails were treated with TH and the presence of A7 mRNA analyzed with in-situ hybridization, and RT-PCR. It was found that TH caused substantial …

The Effects Of Thyroid Hormone On Myosin Heavy Chain A-7 Production In Xenopus Laevis Tail And Leg Muscles, Andrew R. Noble

Honors Theses

The present research examines the expression of myosin heavy chain genes in muscle fibers in Xenopus laevis. Characteristically different muscle fibers are expressed before and after metamorphosis. The embryonic myosin proteins that are synthesized during the tadpole stages are replaced with adult myosin heavy chains at metamorphosis. At least one of the adult myosin genes, called A-7, is expressed only in the adult animals, not in tadpoles. The controlling factor or trigger for the expression of this adult gene still remains unknown. There are a number of possible explanations for the A-7 regulation at metamorphosis, including changes in particular hormone …

The Toxicity Of Cadmium To The Aquatic Amphibian, Xenopus Laevis, Sharon S. Millirons

Master's Theses

Cadmium toxicity is poorly understood but is a potentially serious environmental pollutant. This study was initiated to determine the effect of significant concentrations of cadmium on a readily available aquatic laboratory organism.

The lethal concentration (LC50) for 50 percent of I week old Xenopus laevis tadpoles was determined to be 0.1 ppm CdCI 2. For 5 week old animals, the average LC50 was determined to be 0.98 ppm. Thus, cadmium poses greater toxic threats to the early developmental stages. Moreover, these concentrations of cadmium exceed those commonly found in the nation's water supply. Histological examination suggested that the main site …