Native Glycoprotein II (Phaseolin, G-II), the major 7S storage protein from <i>Phaseolus vulgaris</i> seeds, var. 'Processor' is known to be resistant to <i>in vitro</i> proteolysis by most endopeptidases. On sequential treatments with pepsin and a mixture of trypsin and chymotrypsin, the sub-unit polypeptides of G-II were split midchain. The fragments produced however, retained reactivity with the antibody raised against native G-II quantitatively. When measured by rocket immunoelectrophoresis, the extent of <i>in vitro</i> degradation of G-II by these endopeptidases was negligible. This procedure was used for monitoring the <i>in vivo</i> or <i>in vitro</i> degradation of G-II by gut enzymes other than trypsin or chymotrypsin. Diets containing 10% of a highly purified G-II preparation, did not support growth of rats adequately. Faecal N outputs were elevated and the true N digestibility based on Kjeldhal estimation was only 37%. In contrast, the true GII-N digestibility, based on immunological estimations, was high. It is suggested that G-II and/or its limited breakdown fragments (by trypsin or chymotrypsin) are stimulants of endogenous N secretion in the small intestine. The higher extent of the degradation of G-II in the small intestine of rats <i>in vivo</i> than that obtained by pure endopeptidases <i>in vitro</i> suggested the presence in this tissue of other enzymes capable to act upon and modify the structure of G-II, prior to the action of trypsin and chymotrypsin. These other modifying proteolytic enzymes render the G-II molecule more negatively charged and more susceptible to the subsequent action of trypsin and chymotrypsin. It is suggested that protease content and the ratio of the concentration of the GII-modifying protease(s) to that of trypsin and chymotrypsin may vary appreciably along the small intestine. Accordingly, the dependence of the degradation of G-II <i>in vivo</i> on the competition between all the enzymes capable of attacking it during its passage through the gut may explain the variability of GII breakdown <i>in vivo</i>.

No description available.

A liquid artificial diet system, which was suitable for bioassay of added compounds, was developed for the glasshouse potato aphid, Aulacorthum solani. The diet supported normal growth and reproduction of this insect. Once established, the artificial diet bioassay system was used to test potential insecticidal activities of a variety of proteins found naturally occurring in plants. Effects on survival, development and fecundity were measured. The lectin found in snowdrop, Galanthus nivalis agglutinin (GNA) was found to significantly reduce the fecundity of A. solani, in terms of parthenogenetic nymph production, when administered in artificial diets at the 0.1% w/v level. No significant reductions in survival were found, although GNA administered in vitro did appear to slow the development of A. solani. Transgenic potato plants expressing GNA were used in a growth room trial to show that the reduction in fecundity with the in vitro trials could be reproduced in planta. Aphids feeding on the GNA-expressing potatoes had a significantly lower cumulative nymph production than those feeding on non- transformed plants. The transgenic plants had no effect on the survival of A. solani. The GNA-expressing plants were tested in a larger scale glasshouse trial and resulted in a significantly slower buildup of aphids when compared to control potatoes, thus confirming the results of the artificial diet bioassays and in planta growth room trials. Immunohistochemical studies were performed to detect the presence of GNA in the gut lumen of A. solani fed on artificial diet containing 0.1% w/v GNA; the lectin was observed to be selectively concentrated in the region of the epithelial membrane in the stomach, suggesting that binding to surface carbohydrates or glycoproteins was taking place. Binding to the gut surface has been suggested to mediate lectin toxicity in higher animals, and other insects. A synergistic effect was observed with transgenic potatoes expressing a double construct encoding GNA and bean chitinase (BCH); A. solani cumulative nymph production on these plants was significantly reduced compared to aphids feeding on control and GNA-only expressing plants. However, interestingly, BCH-only expressing plants did not significantly affect the fecundity of A. solani, although a slight reduction in nymph production was observed. On the basis of reports in the literature that suggested that chitin-binding lectins were toxic to insects, an attempt to isolate the gene encoding the chitin-binding stinging nettle lectin was made. RNA was extracted from nettle rhizomes and used to prepare a cDNA library. Successful library construction was verified. PGR methods and a primary screen of the library were used in an attempt to locate the gene.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1977. / Bibliography: leaves [62]-67. / Microfiche. / viii, 67 leaves ill

Incldes bibliographical references / 1 v. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy, Waite Agricultural Research Institute, 1989

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 16, 2008). Includes bibliographical references (p. 36-44).

Thesis (Ph. D.)--University of Hong Kong, 1997. / Includes bibliographical references (leaves 145-155).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. Includes reprinted article: William P. Wergin, Peter J. Gruber, and Eldon H. Newcomb, "Fine structural investigation of nuclear inclusion in plants", Journal of ultrastructure research, v. 30 (1970), pp. 533-557. Description based on print version record. Includes bibliographical references (leaves 76-89).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.