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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Proteins in the ovular secretions of conifers

O'Leary, Stephen James Bernard 10 April 2008 (has links)
Most conifers employ a liquid secretion originating fiom within the ovule at some point during reproduction. Although widely known, these ovular secretions have been poorly characterized. Biochemical analyses of these liquids have been limited to reports of sugars, amino acids, organic acids, and calcium. The purpose of this study was to investigate the physiological regulation of conifer ovular secretions and to further elucidate their contents. Postpollination droplet production was measured in three hybrid larch trees (Larix x marschlinsii Coaz) in relation to xylem water tension in the stem. Secretion production was not correlated to the predictable diurnal fluctuation of tree water status. The ovular secretions of this species were found to be independent of the physiological condition of the stem and are likely under the control of local structures such as the cones or ovules. The concentrations of glucose, fi-uctose, and sucrose were measured in the secretions of larch and hybrid yew (Taxus x media Rehder). In agreement with results &om other conifers, the concentrations of glucose (156 mM) and fructose (145 mM) in the larch secretion were found to be higher than sucrose (1 08 mM). The pollination droplet of yew displayed a novel pattern. The sucrose concentration in this species (23 mM) was found to be an order of magnitude higher than either glucose (2.7 mM) or hctose (2.1 mM). The ovular secretions of larch, yew, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and western red cedar (Thuja plicata Donn. ex D. Donn) were found to contain complex mixtures of proteins when examined by polyacrylamide gel electrophoresis or reversed phase high performance liquid chromatography. The proteins of larch and yew were produced consistently from tree to tree and throughout the period of secretion production. N-terminal amino acid sequencing and antibody recognition identified proteins in larch and yew samples believed to be involved in pollen germination and the promotion of pollen tube elongation. The cell wall modifLing enzyme xyloglucan endotransglycosylase (XET) was identified in the larch secretion. Immunolocalization identified cells in the apical region of the larch micropyle as the site of XET production. Arabinogalactan proteins (AGPs), known to promote pollen tube growth in angiosperms, were found in the secretions of both conifer species. AGP production in the yew ovule was localized to the nucellus. Four pathogenesis-related (PR) proteins were identified in the larch and yew ovular secretions. A lipid transfer protein (LTP) belonging to the PR-14 group was identified in the larch secretion by N-terminal amino acid sequencing. A thaumatin-like protein (TLP, PR-5) was tentatively identified in the larch sample by antibody recognition. One acidic and one basic TLP were identified in the yew secretion by tandem mass spectrometry (MSMS) sequencing of internal peptide fragments. These proteins were named TmTLPa and TxmTLPb respectively. MSMS sequencing also identified a P-1,3-glucanase of the PR-2 group in the yew secretion (TmpGlu). The cDNA coding for TxmTLPa was sequenced and assessed for heterologous protein expression. The nucleic acid sequence predicts a preprotein of 233 amino acid residues with a 28 residue export signal. The putative mature protein has a predicted molecular weight of 21.40 kDa and pI of 4.4. The deduced protein sequence contains 16 cysteine residues conserved across TLPs, and five residues that contribute to the acidic cleft of antifbngal TLPs. In order to produce Z'xmTLPa in sufficient quantities to perform bioassays, the mature sequence of this protein has been inserted into a plasmid vector for the expression of a TxmTLPa fusion protein. This report contains the first simultaneous study of ovular secretion production and tree water status, the first measurements of the sugar concentrations in the ovular liquids of L. x marschlinsii and T. x media, and the first identification of proteins in the ovular secretion of any seed plant.
12

Aspects of the reproductive biology of Breviceps

Minter, Leslie Rory 18 September 2014 (has links)
Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Science, 1999.
13

A child at any cost : A study on how the issue about assisted reproduction for single people is being interpreted by the Swedish media

Nyame, Hallex Berry January 2012 (has links)
March 13th 2012 the Swedish social Committee brings up a proposal that assisted reproduction should be legalize for single women in Sweden. The suggestion was quickly forwarded to the parliament for a decision making. Although majority of the Swedish parties (the alliances) are positive about this proposal, there are also a few who are strongly against the proposal, for example the Christian Democratic Party. The purpose of this study has been to investigate how the two Swedish newspapers Dagens Nyheter and Svenska Dagbladet has written about the issue on legalizing assisted reproduction for single women in Sweden. To help me come to my results and conclusion on this study I decided to use the quantitative content analysis and the qualitative text analysis method. I have specifically chosen to concentrate on how these two newspapers have chosen to present this issue and what angles do Dagens Nyheter and Svenska Dagbladet uses to present this issue to their readers. After my qualitative text analysis, I came to the conclusion that this issue didn’t get the attention that it deserves from both of the newspapers. Since the issue is about babies, women and their bodies, I expected the newspapers to write about this issue as a gender issue, but that was not the case. Instead it was twisted around by the press and made into a political fight between the Christian Democrat party that is against the proposal and the alliances that is positive to the proposal. In all the articles I had chosen to analyze, I as a reader was met by the voices of different politicians that had strong opinions about legalizing assisted reproduction for single women. The opinion of ordinary people didn’t seem to matter to any of the journalist and neither was the opinion of women, because I realized that neither of these groups were found in the articles. Even more interesting was the fact that the voices of the politicians were all dominated by men. In conclusion looking at the issue on legalizing assisted reproduction for single women, one would supposed that the issue is going to be based on subjects about babies, hospitals, women and their bodies. Instead the issue was made into a political fight and dominated by male voices and opinions.
14

Study on the reproduction of Paramyxine nelsoni (Myxinidae)from the southwestern coast of Taiwan

Hung, Li-Yueh 12 February 2003 (has links)
This study investigates the reproductive biology of Paramyxine nelsoni which distributes in some areas off the southwestern coast of Taiwan. Specimens were captured by shrimp traps. Body weight and body length were measured. Maturation stages of female, adult male and immature were recored. Egg length¡Bnumber of egg, gonad weight and GSI for mature females were measured. Results showed that P. nelsoni spawned all year round. However, a drastic increase of GSI in June and a drop in July, was noticed suggesting that reproduct in summer. Sex ratio was female¡Gmale¡Gimmature = 0.68¡G0.20¡G0.11; male/female = 0.30 . Number of females was fewer in July, suggersting a possibility that female foraging activity reduce after spawning. The minimum maturature sizes for both sexes were 16 cm. The maximum size of female was larger than that of male. Results showed that P. nelsoni is not proatndrous. Small female smaller than 20 cm did not contained eggs longer than 3 mm. Some of females longer than 20 cm might involve in spawning activity. According to the frequency distribution of egg length, it was confirmed that P. nelsoni were synchronous spawner and reproduct iteroparous. Eggs were in one to two discontinuous size classes. Mature females produced only 3-7 ripe eggs at a time. Anchor-like hooks appeared in both tipa of 20~27 mm eggs. Mechanism controlling the development of these hooks remains unclear.
15

On the perseverative tendency

Foster, William S. January 1900 (has links)
Thesis (Ph. D.)--Cornell University, 1913. / "Reprinted from the American journal of psychology July, 1914, vol. XXV." "From the Psychological laboratory, Cornell university."
16

Interrelationships of certain thermal and endocrine phenomena and reproductive function in the female bovine

Gwazdauskas, Francis Charles, January 1974 (has links)
Thesis (Ph. D.)--University of Florida, 1974. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 108-117).
17

Induction and maintenance of corpora lutea in prepuberal gilts.

Segal, Donald Howard. January 1970 (has links)
No description available.
18

Population dynamics of the hard clam, Mercenaria mercenaria (Linne'), and its relation to the Georgia Hard Clam Fishery

Walker, Randal Leonard 05 1900 (has links)
No description available.
19

Sex ratios in terrestrial isopods

Brunet, Johanne January 1986 (has links)
No description available.
20

Reproductive strategies of males in the egg parasitoid Trichogramma turkestanica Meyer (Hymenoptera:Trichogrammatidae)

Martel, Véronique. January 2007 (has links)
In most animals, males are assumed to have access to an unlimited supply of sperm, while females produce few eggs that are large and costly to produce. In parasitoids, there is a paradigm to the effect that males are polyandrous, inseminate as many females as possible and express no optimization in their behaviours. In reality, sperm production incurs non-trivial costs. Because sperm are transferred in ejaculates and that their cost is greater than that of individual sperm, males can gain by carefully allocating their ejaculates. In this thesis I have investigated different aspects of males' reproductive strategies, mainly sperm and time allocation, in the egg parasitoid Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae). / In T. turkestanica, mating mainly occur on the emergence patch. However, results show that mating opportunities are not distributed equally among males and 2.9% of successful males are sperm-depleted when they disperse from the emergence patch. Nevertheless, 97.1% of males disperse non sperm-depleted, suggesting off-patch mating potential. Male T. turkestanica have thus an insemination capacity higher than necessary to inseminate the females present on the emergence patch, a pattern that seems to be common among parasitic wasps. / On the emergence patch, both virgin and mated females can be encountered. Males are able to discriminate between those mates and prefer virgin ones. This preference is stronger for energy- and time-limited males. / Sperm competition risks and/or intensity are important for males that decrease their sperm investment when the number of rivals increases. Such response is optimal when the benefits from investing more sperm become lower than the costs of a low paternity assurance under intense sperm competition. / Finally, male T. turkestanica express behaviours enabling them to optimize their patch time exploitation. Depending on their evaluation of the patch quality, males modify their patch residence time. / This thesis shows that time- and sperm-limited male T. turkestanica are not simply maximizing the number of females inseminated, but rather maximize their lifetime fitness by optimizing sperm and patch time allocation.

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