No description available.

Regulation of tubulin gene expression in embryos of the sea urchin Lytechinus pictus has been experimentally investigated by use of cloned recombinant tubulin DNA and anti-tubulin antiserum. Tubulin synthesis appears to be autogenously regulated at the level of tubulin mRNA stability by the level of unpolymerized tubulin; i.e., the more unpolymerized tubulin, the less stable the tubulin mRNA. Destabilization of tubulin mRNA requires continued protein synthesis. Most of tubulin stored in eggs is unpolymerized; during embryogenesis the mass of tubulin per embryo changes little, but unpolymerized tubulin is increasingly polymerized into microtubules. There is a transcriptional stimulation of tubulin genes at the time of ciliogenesis but thereafter autoregulation by the ontogenetic decrease of the level of unpolymerized tubulin plays a predominant role for an increasing accumulation of tubulin mRNA. Deciliation results in a transient enhancement of transcription of tubulin genes, which is independent of the level of unpolymerized tubulin and does not require protein synthesis.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 145-154). / Microfiche. / xiii, 159 leaves, bound ill., photos. 29 cm

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 93-117). / Microfiche. / x, 117 leaves, bound ill. (some col.) 29 cm

Thesis (M.S.) in Marine Biology--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 83-90).

No description available.

No description available.

No description available.

No description available.

Cd levels were measured in three different body compartments of the echinoid Stomopneustes variolaris after exposure to concentrations of 5 ug 1l, 20 ug 1l and 50 ug 1l Cd for a period of two weeks. The body compartments investigated included the intestine, gonads and skeleton. The gonads did not exhibit dose-dependent bioaccumulation. The levels of cadmium in the intestine and skeleton were significantly different between the treatments, suggesting that dose dependent bioaccumulation had occurred in these compartments (except in the skeleton where higher levels -were recorded for those exposed to 20 ug 1l than those exposed to 50 ug 1l) The levels recorded in the intestine were higher than those recorded in the gonads and skeleton at the higher Cd exposures of 20 and 50 ug 1i. The levels accumulated in the gonads and skeleton were not significantly different from each other. A separate group, exposed to 20 ug 1`1Cd over a period of two weeks, was placed in uncontaminated seawater to determine if the echinoids were capable of bioremediation. Bioremediation was found to lower the Cd levels in the gonads, but not in the intestine and skeleton. Cadmium levels for the three body compartments were also recorded from specimens collected from the field, indicating the presence of this element in the environment. In addition to using atomic absorption spectroscopy (AAS), energy dispersive X-ray analysis (EDX) was used as a comparative technique to detect the presence of Cd in the skeleton of the urchin. Cadmium was detected in the skeleton with AAS, but not with EDX. S. variolaris proved to be a capable biomonitor of Cd contamination. / Thesis (M.Sc.Eng.)-University of Durban-Westville, 2002.