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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.
1

Reproductive ecology of the Antarctic brachiopod Liothyrella uva

Meidlinger, Karen January 1997 (has links)
No description available.
2

CYTOGENETICS OF GAMETOGENESIS IN HAPLO 9 OF GOSSYPIUM HIRSUTUM L. (MEGASPOROGENESIS, MEIOSIS).

MYLES, ELBERT LEWIS, JR. January 1985 (has links)
Plants monosomic for chromosome 9 of Gossypium hirsutum, in addition to Haplo 9 plants, produce many kinds of aneuploid progenies consisting of monosomics, trisomics, multiple monosomics, and different monosomic-trisomic combinations. Cytological analysis of megasporagenesis was conducted to determine the stage and the mechanism that would account for the production of the different kinds of aneuploid progeny. Two new cytotypes involving chromosome 9 were isolated and identified as monotelodisome 9S (Telo 9S) and monoisodisome 9S (Iso 9S), both of which produce different kinds of aneuploids very similar to Haplo 9. Monotelodisomic 9L plants do not produce various kinds of aneuploid progeny like Haplo 9, Telo 9S and Iso 9S. These observations indicate that control of chromosome segregation is on the long arm of chromosome 9. There was no significant difference between Telo 9S and Iso 9S in the kinds and frequencies of aneuploids, but there was a significant difference between these two and Haplo 9. Haplo 9, Telo 9S and Iso 9S showed no significant difference in the chromosomes subtracted or added to the chromosome complement of their respective aneuploid progenies. Analysis of female gametogenesis in TM1 or control plants showed that premeiotic division occurred when bud size is 6.0 - 6.6mm; meiosis occurred when bud size is 6.3 - 7.2mm; the first mitotic division of the megaspore occurred when bud size is 6.9 - 7.8mm, and the second and third mitotic divisions of the megaspore occurred when bud size is 7.8 - 8.5mm. The premeiotic, meiotic, and post meiotic divisions were normal. Female gametogenesis was cytologically analyzed in Haplo 9 plants and it was observed that there was a higher frequency of gametophytes with fewer post meiotic divisions and that there was nonsynchrony of the post-meiotic divisions in a number of the developing female gametophytes. It is assumed that these irregularities are due to the absence of chromosome 9. It is concluded that the long arm of chromosome 9 has control over chromosome segregation, and that most likely nondisjunction occurs throughout female gametogenesis, but confined primarily to the three mitotic divisions following meiosis. Genetic tests showed that eight mutant genes were not located on chromosome 9. The aneuploids had lower seeds per boll than normal disomic plants.
3

The effect of gonadotropin-releasing hormones (GnRH) I & II on sperm motility and acrosome status of the Vervet monkey (Chlorocebus aethiops) in vitro.

De Villiers, Charon. January 2006 (has links)
<p>Gonadotropin Releasing Hormone (GnRH) is a hypothalmic decapeptide, which regulates mammalian gonadotropin secretions by binding to specific, high affinity receptors in the pituitary. Two forms of GnRH (GnRH I and GnRH II) are expressed in the brain of human and some primates. Even though primates have been used extensively in a variety of investigations in relation to the role of GnRH in reproduction, there is no evidence of any research to investigate the direct effect of GnRH on primate sperm.</p>
4

The effect of gonadotropin-releasing hormones (GnRH) I & II on sperm motility and acrosome status of the Vervet monkey (Chlorocebus aethiops) in vitro.

De Villiers, Charon. January 2006 (has links)
<p>Gonadotropin Releasing Hormone (GnRH) is a hypothalmic decapeptide, which regulates mammalian gonadotropin secretions by binding to specific, high affinity receptors in the pituitary. Two forms of GnRH (GnRH I and GnRH II) are expressed in the brain of human and some primates. Even though primates have been used extensively in a variety of investigations in relation to the role of GnRH in reproduction, there is no evidence of any research to investigate the direct effect of GnRH on primate sperm.</p>
5

The effect of gonadotropin-releasing hormones (GnRH) I & II on sperm motility and acrosome status of the Vervet monkey (Chlorocebus aethiops) in vitro

De Villiers, Charon January 2006 (has links)
Masters of Science / Gonadotropin Releasing Hormone (GnRH) is a hypothalmic decapeptide, which regulates mammalian gonadotropin secretions by binding to specific, high affinity receptors in the pituitary. Two forms of GnRH (GnRH I and GnRH II) are expressed in the brain of human and some primates. Even though primates have been used extensively in a variety of investigations in relation to the role of GnRH in reproduction, there is no evidence of any research to investigate the direct effect of GnRH on primate sperm. / South Africa
6

Functional analysis of DAZL-mediated translation activation during mammalian gametogenesis

Sousa Martins, Joao Pedro January 2012 (has links)
Gametogenesis is a highly complex process that requires stringent control of gene expression, in which translational regulation plays an essential role. Deleted in Azoospermia-like (DAZL) belongs to the DAZ family of RNA-binding proteins, which are restricted to germ cells, and regulate mRNA translation. Importantly, loss of function of these proteins results in infertility in both males and females in a wide variety of organisms. A model for the mechanism by which DAZL stimulates translation has been proposed based on work in Xenopus laevis (X. laevis) oocytes. In this model, DAZL functions by recruiting the translation initiation factor poly(A)-binding protein (PABP) to the 3’ untranslated region (UTR) of messenger RNAs. Simultaneous binding of PABP to Dazl and factors at the 5’ end confers a “closed-loop” mRNA conformation, which promotes translation initiation. To examine whether DAZL plays a similar role in mammals, co-expression of Dazl and PABP family members was investigated in fetal and adult mouse gonads. In contrast to X. laevis, mammals encode four cytoplasmic PABPs which share a similar domain organisation: PABP1, tPABP, ePABP and PABP4, of which PABP1 and PABP4 appear to be expressed in a wide range of tissues. Immunohistochemistry revealed that Dazl, Pabp1 and Pabp4 are all expressed in primordial germ cells (PGCs) but these show different expression patterns following germ cell sex differentiation. In adult testes Dazl is expressed in spermatogonia and spermatocytes, coinciding with the peak of Pabp4 expression. In contrast, the peak of Pabp1 expression occurs later than that of Dazl, with these proteins only being co-expressed in late pachytene and secondary spermatocyte phases. In adult ovaries, Pabp1, Pabp4 and Dazl are all expressed in the oocytes of primordial and primary follicles. Since both PABP family members are co-expressed with Dazl, the ability of DAZL to interact with PABP1 and PABP4 was investigated in vitro and in vivo. Surprisingly, these studies showed that DAZL discriminates between different PABP family members, only interacting with PABP1, providing the first report of a PABP-specific protein partner. Several putative DAZL mutations have been identified in patients with impaired fertility. Two of these mutations, I37A and R115G, are located in the RNA recognition motif (RRM), a domain which is found in many RNA-binding proteins and mediates both RNA and protein interactions. Thus, the role of these mutations in the ability of DAZL to stimulate translation was investigated. To this end, a translational target of human DAZL (hDAZL) was sought. The 3’UTR of growth differentiation factor 9 (hGDF9) mRNA was found to confer regulation by hDAZL and thus the ability of mutant DAZLs to stimulate reporter mRNAs containing this 3’UTR was examined. This revealed that both mutations compromised the ability of hDAZL to stimulate hGDF9 translation, suggesting a causative effect. These results were further confirmed in assays in which hDAZL is artificially tethered to mRNAs. The ability of mutant hDAZLs to stimulate translation in this assay was compromised suggesting that loss of function is, at least in part, due to impaired protein-protein interactions rather than altered RNA-binding. This work provides insights into the molecular mechanism by which DAZL stimulates the translation of specific mRNAs during mammalian gametogenesis and provides evidence that this function may play an important physiological role in human reproduction.
7

Evaluation of Diet, Gametogenesis, and Hermaphroditism in Freshwater Mussels (Bivalvia: Unionidae)

Henley, William F. 06 June 2002 (has links)
To determine the effects of different algal diets on freshwater mussels, tissues of Elliptio complanata were sampled for physiological, somatic, and gametogenic condition from August 1999 to May 2000. Treatments included mussels fed Scenedesmus quadricauda (S), Neochloris oleoabundans (N), a no feed treatment (NF), and a reference group of mussels from the Nottoway River (NR), Virginia. The levels of protein and glucose differed among treatments (p<0.0001), but glycogen and percentage tissue moisture did not (p>0.17). Production of ripe and developing gametes differed significantly among treatments (p=0.001), but stage of gamete development did not (p=0.70). Lipid levels and muscle fiber areas of treatment groups differed significantly (p<0.0001). Results of the feeding trial indicate that S. quadricauda is a suitable feed for E. complanata, but future experiments should identify algal species higher in carbohydrates for a mixed algal diet. To determine sex and stage of gametogenesis, tissue histological sections from gonads of Villosa iris and Utterbackia imbecillis were evaluated. Occurrences of oogenic, spermatogenic, and hermaphroditic tissues were summarized in frequency tables. Visceral sites from which similar tissues were collected from conspecific specimens were evaluated for gametogenic stage. Sex was accurately determined in the central, visceral portion V. iris and female regions of U. imbecillis; and spermatogenic tissue was consistent in the dorsal-anterior areas of U. imbecillis. These areas also provided accurate determination of gamete stage in specimens. Reproductive asynchrony was observed among males and females (p<0.02). Male regions of U. imbecillis showed gamete stage characterized by mature and developing spermatogenic tissue, while 2 groups of mussels were showed oogenic development characterized by mature oocytes and resorption of gametes. Male V. iris showed early gamete development without mature spermatozoa, and 2 groups of female V. iris showed mature and developing gametes and resorption of gametes. Protocols for biopsy tissue collection from selected visceral areas were developed for U. imbecillis and V. iris for sex determination and staging of gametogenesis. The application of this biopsy protocol should be considered population specific, and protocols appropriate for other populations and species should be developed with methods of this study. / Ph. D.
8

Gametogenic Cycles of Marine Mussels, Mytilus edulis and Mytilus trossulus, in Cobscook Bay, Maine

Maloy, Aaron P. January 2001 (has links) (PDF)
No description available.
9

Manipulation of development by nuclear transfer

Palermo, Gianpiero D. January 2004 (has links)
Abstract not available
10

Etude des événements moléculaires de la gamétogenèse de Plasmodium berghei par des approches protéomiques / Estudo dos eventos moleculares da gametogênese de Plasmodium berghei por abordagens proteômicas / Investigation of the molecular events in Plasmodium berghei gametogenesis through proteomic approaches

Saraiva Garcia, Carlos Henrique 27 October 2016 (has links)
Le paludisme est causé par des parasites du genre Plasmodium et la gamétogenèse est une étape essentielle à sa transmission. Afin d'améliorer les connaissances sur la genèse des gamètes, nous avons mené des études protéomiques sur des gamétocytes de P. berghei sauvages ou mutants avec le gène moteur de la kinésine 8 interrompu. Le mutant est morphologiquement semblable au type sauvage mais incapable de compléter la gamétogenèse et les gamètes mâles d'exflageller. A partir d'échantillons enrichis en gamétocytes, la gamétogenèse a été suivie sur 15 min après induction par l'acide xanthurénique. Les peptides marqués par iTRAQ à partir de triplicatas biologiques ont été analysés par nanoLC/MS-MS et interprétés par les logiciels Patternlab et Blast2GO. Les phosphopeptides ont été enrichis au TiO2. Chez le parasite sauvage, 443 protéines et 206 phosphoprotéines ont été identifiées à partir de 2617 peptides et chez le mutant, 530 protéines et 218 phosphoprotéines à partir de 3198 peptides. L'induction de la gamétogenèse est marquée par une transcription, une biosynthèse de protéines et de l'ADN importantes. Chez le mutant, la formation des fuseaux mitotiques et des axonèmes des flagelles des gamètes mâles est fortement affectée. Des protéines du complexe du protéasome dépendant de l'ubiquitine, de la réponse au stress, du métabolisme énergétique sont également affectées. Cette étude apporte de nouveaux éléments de compréhension sur le rôle joué par la kinésine 8 dans la gamétogenèse de Plasmodium. / Malaria is caused by parasites from Plasmodium genus and its gametogenesis is an essential step to ensure the malaria transmission. In efforts to improve the knowledge on gamete biology we did quantitative proteomic and phosphoproteomic comparative experiments with P. berghei WT and gametocytes disrupted for the motor gene kinesin 8. The mutant is morphologically similar to wild-type parasite but impaired gametogenesis and unable to exflagellate. The Gametocytes-enriched sample from mice at time T0 were xanthurenic acid-induced to exflagellate and harvested at time T7 and T15. The iTRAQ labelled peptides from independent biological triplicate sample were analyzed overtime through nanoLC/MS-MS Orbitrap after TiO2 enrichment, and interpreted by Patternlab and Blast2GO softwares. The wild type had 443 proteins and 206 phosphoproteins identified from 2,617 peptides. The mutant had 530 proteins and 218 phosphoproteins identified from 3,198 peptides. GO biological processes related to RNA translation, DNA and protein biosynthesis were most prominent and phosphorylated proteins are mainly RNA, ATP or protein binding proteins. Within the mutant, the axoneme and mitotic spindle microtubules disorganization were strongly affected. The nucleosome components are key to nuclear division disorganization. The ubiquitin-dependent proteasome complex and stress/folding response, energy metabolism and egress proteins were affected. The Plasmodium proteomic approach brings that insight into kinesin 8 critical importance for male gametogenesis in Plasmodium with effect on protein expression, phosphorylation modulation, flagellar organization and biology.

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