Thesis (Ph. D.)--University of Nebraska, 1931. / "Contribution from the Zoological laboratories, University of Nebraska, no. 179." Includes bibliographical references (p. 70-72).

The precise location of pre-messenger RNA (pre-mRNA) was determined within the cell nucleus of the amphibian N. maculosus (mudpuppy) oocyte. Pre-messenger RNA or heterogeneous nuclear RNA (hnRNA) is directly transcribed from the gene in the cell nucleus (Jelinek et al., 1983). This highly unstable, high molecular weight complex is then processed into messenger RNA (mRNA). Again this transformation is thought to take place in the nucleus.By employing the techniques of in situ hybridization along with light and high resolution autoradiography an effort was made to localize, via a radioactive probe, ( 3H) poly (U), pre-mRNA within the nucleus. Additionally, various inhibitors were employed in this study to analyze changes in the amount and distribution of radioactive material within the cell.Light microscopy observations of autoradiographs reveal a consistent pattern of probe localization over the nucleoli with a broader dispersal across the nuclei. Ultrastructural studies reveal the presence of granules (perichromatin granules) localized over both the nucleolar-associated chromatin and at the border of condensed chromatin. These structures are contained in the cell nucleus and are presumed to function in the transport and storage of mRNA. / Department of Physiology and Health Science

Cytochemical localization of nuclear-envelope nucleos-side triphosphatase was exhibited in the nuclear membrane and nuclear pores of the Necturus, maculosus oocyte. This enzyme is thought to promote nucleocytoplasmic transport of mRNA through the nuclear pores. Various tissue preparations were performed to assure optimum results of reaction product formation and preservation of tissue ultrastructure.Incubation of frozen oocyte sections in a modified Wachstein-Meisel medium resulted in positive staining of the nuclear membrane and the nucleoli as evidenced in light and electron micrographs. Whole oocytes were incubated in the Wachstein-Meisel medium and then embedded in Epon for electron microscopy. The whole oocytes contained reaction product associated with microvilli and plasma membranes. Exposure of manually isolated nuclei to the same experimental medium resulted in lead deposits in the nuclear envelope, the nuclear pores, and randomly dispersed among chromatin granules. Thus, these nuclear structures may play a role in transport of mRNA to the cytoplasm. / Department of Physiology and Health Science

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

No description available.

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

Population structure is influenced by extrinsic factors, such as landscape architecture and dispersal barriers. Lotic network architecture is known to constrain ecological, demographic and evolutionary processes, including population genetic structure. I assessed the population structure of a widespread aquatic salamander, Necturus maculosus, across three river basins in central and eastern Kentucky. I examined the role of network architecture, anthropogenic barriers, and spatial scale on patterns of population structure. I also provided a review of N. maculosus capture methods and offer an improved trap design. I identified significant structuring between the combined Licking/Kinniconick basin and the Kentucky River basin, with further structure within each basin. I found evidence for both hierarchically organized populations structure (e.g. Stream Hierarchy Model), as well as population structure unaffected by network hierarchy (e.g. Death Valley Model). These results highlight the importance of scale when examining population structure. Whereas one model may suffice to explain population structure at a local scale, a second model may be necessary to accurately describe the population structure across larger spatial scales. These results suggest that local factors affect population structure uniquely across a species’ range, and support a multi-model approach for assessing population structure.