No description available.

Although parasitoid wasps have shown promise as model systems for studying life history evolution, empirical studies of certain traits in these small insects have proven difficult. In this dissertation, two "black boxes" in the life histories of female parasitoids are examined: (1) oosorption, and (2) dispersal by flight.I first demonstrate that a short-lived species with high early reproductive investment (Eretmocerus eremicus) resorbs eggs, which runs counter to the notion that the time costs of oosorption are prohibitive to such wasps. Instead, it appears that the resorption mechanism in E. eremicus is capable of both decreasing costs and increasing nutritional benefits of oosorption relative to that of other parasitoid species. In addition, a literature review reveals four functional hypotheses for parasitoid oosorption: (1) age-related egg apoptosis, (2) conservation of ovarian capacity, and (3) nutrient allocation to either longevity or future oogenesis. As none of these can be rejected, I propose several avenues of future research: 1) refinement of physiological techniques to measure nutrient traffic into and out of eggs, 2) morphological phylogenetic studies of oosorption mechanisms, 3) development of lifetime nutrient budgets for parasitoids with different reproductive life histories, 4) examination of decay rates of oocytes with different yolk types, and 5) increased study of ovarian dynamics in pro-ovigenic parasitoids.Next, I describe results from a vertical flight chamber study designed to test hypotheses regarding the correlation between pre-oviposition dispersal and reproductive effort in parasitoid wasps. This experiment was conducted on 1-d-old female whitefly parasitoids from five species in two genera. The two Eretmocerus spp. showed a higher flight propensity than the three Encarsia spp. This may be, in part, due to a more time limited life history in the former. Within species, egg load did not correlate well with flight propensity for all species examined. Finally, among individuals of Er. eremicus, the relationship between effective flight distance and egg load appears to be context dependent, as data consistent with both positive and negative correlations were collected. Correlational changes between flight distance and egg load may be due to variation in biotic (female longevity) or abiotic (temperature, relative humidity) factors.

Messenger RNA localization is a widespread mechanism of posttranscriptional regulation of gene expression in multicellular organisms ranging from yeast to mammals. In Drosophila oocytes, gurken (grk) mRNA is transported by Dynein to produce a local secreted signal to the overlying follicle cells. This signal is responsible for setting up the primary axes in the oocyte. grk mRNA is transcribed in nurse cells and transported into the oocyte where it localizes at two distinct stages of oogenesis, thus targeting the translation of Grk/TGFalpha protein, first to the posterior and later to the dorso-anterior (DA) corner where it is translated. Gurken protein signals to the overlying follicle cells to establish the dorsal fate of the oocyte. grk transcripts are transported by Dynein in EM-dense particles on microtubules. These particles are not associated with vesicles nor membrane-bound and contain many copies of grk mRNA, Dynein and hnRNP Squid. At the DA corner transport particles assemble into large EM-dense cytoplasmic anchoring complexes called Sponge Bodies. In this thesis I present evidence that at their dorso-anterior destination, grk transcripts are statically anchored by Dynein, independently of functional Egalitarian and Bicaudal D, which are required for Dynein transport. I show by the disrupting the protein’s function after it has fulfilled its role in transport that hnRNP Squid is involved in the formation and maintenance of these Sponge Bodies. I provide evidence by EM and fluorescent microscopy that Sponge Bodies share many of components of translational regulation pathways found in Processing Bodies. I show by small RNA interference experiments and by genetic analysis that the structural role of Dynein heavy chain is a unique feature of the Sponge Bodies and that such a function does not occur in Processing Bodies in Drosophila. I show that the localization and anchoring of RNA in Sponge Bodies is not a unique feature of grk mRNA but that I factor RNA is also localized to Sponge bodies. The work presented tries to elucidate the function of Sponge Bodies in translational control of grk mRNA and illustrates by EM the dynamic nature of the Sponge Body structure during oogenesis. My results suggest that Sponge Bodies are RNA granules that are similar to Processing Bodies in a way that they are involved in translational regulation but unlike Processing Bodies depend on Dynein for their structural integrity. I propose that Sponge Bodies are RNA dependent granules that form by the recruitment of proteins involved in the anchoring and translational regulation.

No description available.

Effects of phorbol myristate acetate (PMA), dibutyryl cyclic AMP (dbcAMP), 6-dimethylaminopurine (6-DMAP), okadaic acid (OA), cycloheximide (CHX), actinomycin D (AcD) and tunicamycin (TuM) on plasminogen activator (PA) activity and maturation rate in bovine and porcine oocyte-cumulus cell complexes (BOCC and POCC, respectively) in vitro were determined. Plasminogen activator activity was measured by SDS-PAGE, casein-agar zymography and densitometry. Three plasmingen-dependent lytic zones (92-95, 71-73 and 49-51 kD) and one PA inhibitor (52 kD) were observed in BOCC. Immunoprecipitation and amiloride sensitivity suggested that the 49-51 kD protease is a urokinase type PA (uPA), the 71-73 and 92-95 kD proteases are a tissue type PA (tPA) and tPA-PAI complex, respectively, and the PAI is PAI-1. In POCC, two plasminogen activators (71-78 and 93-96 KD) were observed. Lack of amiloride sensitivity suggested that the 71 -78 kD band is a tPA and the 93-96 kD band is possibly a tPA-PAI complex. Increasing dbcAMP in the culture medium increased activity in both BOCC and POCC in dose-dependent fashion (P<0.05). In BOCC cultured with PMA, total PA activity increased, however high concentrations of PMA (10 and 100 ng/ml) decreased tPA activity in matured POCC. Plasminogen activator activity decreased in 6-DMAP, actinomycin D and cycloheximide and oocyte maturation was also inhibited in these treatments. When POCC were treated with 25 nM OA, uPA activity was observed. Plasminogen activator activity increased in either BOCC or POCC treated with up to 25 nM OA, however PA activity decreased at concentrations greater than 75 nM (P<0.05). Incubation of BOCC with tunicamycin reduced the molecular mass of tPA and tPA-PAI complex and PAI-1 by 5-10%, however PA activity was not inhibited. These data suggest that BOCC matured in vitro produce uPA, tPA and PAI-1 however POCC produce only tPA and PAI. The production of PA and PAI by either BOCC or POCC is associated with oocyte maturation and influenced by stimulators of the protein kinase A and C, modulators of intracellular phosphorylation and metabolic inhibitors. / Graduation date: 1993

Microvilli are actin-based protrusions at the apical surface of epithelial cells and have diverse functions. My bioinformatic analysis suggests that human Cadherin 23, which is critical for normal microvillus development, has three paralogous homologues in Drosophila, Cad74A, Cad87A, and Cad88C. All three fly cadherins are present in follicle cell microvilli in late stages of oogenesis. The combined loss of Cad74A, Cad87A, and Cad88C did not produce any obvious defects in follicle cell microvilli or egg morphology. However, in a Cad74A Cad88C double mutant, Cad87A is strongly reduced at the apical surface of follicle cells. Furthermore, females overexpressing Cad74A produced abnormal eggs. This phenotype was rescued by increasing or reducing Cad87A expression. Together, my data suggest genetic interactions between the three cadherins, and that Cad74A and Cad87A may be involved in eggshell formation.

Microvilli are actin-based protrusions at the apical surface of epithelial cells and have diverse functions. My bioinformatic analysis suggests that human Cadherin 23, which is critical for normal microvillus development, has three paralogous homologues in Drosophila, Cad74A, Cad87A, and Cad88C. All three fly cadherins are present in follicle cell microvilli in late stages of oogenesis. The combined loss of Cad74A, Cad87A, and Cad88C did not produce any obvious defects in follicle cell microvilli or egg morphology. However, in a Cad74A Cad88C double mutant, Cad87A is strongly reduced at the apical surface of follicle cells. Furthermore, females overexpressing Cad74A produced abnormal eggs. This phenotype was rescued by increasing or reducing Cad87A expression. Together, my data suggest genetic interactions between the three cadherins, and that Cad74A and Cad87A may be involved in eggshell formation.

No description available.

Currently more than 300 million adults are obese and 1 billion are overweight throughout the world. Obesity is frequently accompanied by an array of health conditions such as hyperglycemia, hyperlipidemia, hypertension, cardiovascular diseases, and diabetes which are all considered to be part of what is now known as the metabolic syndrome. The role of adipose tissue as an endocrine organ has been emphasized by the characterization of its hormones: leptin, adiponectin and resistin. All three proteins regulate energy utilization. Over the past decade, leptin and resistin have also been shown to affect the reproductive system. This suggests that other adipocytokines, such as adiponectin, may also affect reproduction. This relationship was investigated using a porcine in vitro maturation system. When porcine cumulus oocyte complexes were matured in the presence of 30mug/mL of recombinant adiponectin an improvement in the meiotic maturation was observed. Moreover, maturation of denuded oocytes revealed that adiponectin acts through the cumulus cells to improve meiotic maturation of porcine oocytes. Finally, maturation of cumulus-oocyte complexes in the presence of MAPK pathway inhibitors suggested that adiponectin acts at or downstream of MEK1/2 and 38MAPK. This study shows, for the first time, an effect of adiponectin on porcine oogenesis. Further investigation will determine whether adiponectin also affects embryo development.

Bicaudal-C is a dominant maternal effect mutation which shows incomplete penetrance. Females are fertile and not all their progeny are affected. Those embryos which do not hatch show defects in their antero-posterior polarity, and give rise to bicaudal embryos which are duplicated for posterior structures. Twelve alleles of the genes have been phenotypically analysed. The penetrance of each allele has been determined and the phenotypes of embryonic defects such as mouth/head defect, bicaudal and uncellularized embryos classified and scored, in order to use this information to analyse these alleles at the cellular and molecular level. The bicaudal phenotype results from the mislocalization of the oskar and nanos RNA at the anterior end of the embryos. The gene also has a recessive phenotype which makes the females sterile. The phenotype is the result of specific defects in follicle cell migration. The alleles have been subdivided into two classes according to their phenotype: weak and strong. The gene encoding Bicaudal-C has been cloned and sequenced. It is expressed in the germline and appears to encode a member of the KH domain family of putative RNA-binding proteins.