Browsing by Subject "Chickens -- Embryos"
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Item Chorioallantoic membrane use as a non-lethal, non-invasive indicator of oviparous organism exposure to organochlorine contaminants(Texas Tech University, 2000-05) Bargar, Timothy AndrewThe goals of this dissertation were to (1) describe the relationship between chemical levels in the chorioallantoic membrane (CAM), chick, and adult, and (2) show that data from residue analyses of CAMs can be used as a correlate of effect within neonates and adult oviparous organisms. Three different studies were done to address these goals. First, the effect of both chemical structure and chemical interaction on maternal excretion of organochlorines (OCs) into eggs was investigated. Actively laying adult white leghorn chickens (Callus domesticus) were injected with structurally different chemicals. Laid eggs were collected and analyzed for the dosed chemicals. Chemical structure significantly affected chemical excretion into the eggs while chemical interactions were less influential on excretion. Second, chemical distribution among three different egg compartments (embryo, CAM, yolk+albumin) during embryonic development was investigated. Fertile eggs from hens dosed with a chemical mixture were sacrificed at 9, 14, and 19 days of incubation corresponding to 43%, 67%, and 90% of embryonic development. Greater than 70% of the OC mass within the whole egg remained in the yolk-i-albumin, i.e., external to the embryo, through 90% of development. In addition, predominance of certain OCs in the CAM early in development decreased as development proceeded indicating chemical structure influenced distribution among the compartments. Third, the relationship of OC levels in the CAM to hepatic ethoxyresomfin-o-dealkylase (EROD) activity and plasma estradiol levels in both hens and chicks was investigated. Fertile eggs collected from hens were incubated until hatch. CAMs were removed from discarded eggshells for residue analyses. Blood and livers were removed from 1-week-old chicks, and from hens for biochemical assays. Hepatic EROD activity in both hens and chicks was significantly related with OC mass in CAMs while estradiol levels were not. This dissertation demonstrated that data from residue analyses of CAMs can be used to infer biological effect in both neonatal and adult oviparous organisms. It also shows that OC concentrations in eggs and adults may be predicted based on OC levels in eggs. Therefore, residue analyses of CAMs can be used for non-lethal, non-invasive assessment of oviparous organism exposure to organochlorines.Item Examination of tissue interaction in the developing heart(Texas Tech University, 1983-08) Runyan, Raymond BruceNot availableItem Localization and functional interactions of fibronectin and associated basement membrane proteins during embryonic heart development(Texas Tech University, 1984-08) Kitten, Gregory TThe early embryonic heart is composed of two, cylindrical epithelial layers, an inner endothelium and an outer myocardium. The cardiac jelly (CJ), an a cellular accumulation of extra cellular matrix (ECM), fills the space between the two layers. All cardiac endothelial cells (EC) do not follow an identical course of differentiation. Some of the EC of the atrio ventricular (AV) and outflow tract (OT) regions undergo an epithelial-mesenchymal transition to form mobile cardiac mesenchymal (CM) cells while in other regions (e.g., ventricle), EC differentiate along the lines of a typical vascular endothelium. The mechanisms controlling the biphasic differentiation of EC and the subsequent migration of CM cells are poorly understood. Although the CJ lies between two epithelia and is spatially equivalent to a basement membrane (BM), it has not traditionally been considered to be organized into a BM-like structure. The potential significance of this observation lies in the possibility that BM, or their individual components (i.e., fibronectin (FN), laminin (LH), type IV collagen, and heparan sulfate proteoglycan (HSPG)), may function as the regulatory site o f " epithelial differentiation and morphogenesis. The temporal changes in the localization and the functional involvement of the BM components FN, LM, type IV collagen, and HSPG were investigated with respect to (1) EC attachment and differentiation and (2) CM cell attachment and migration. A cryofixation technique was developed in order to determine the in situ immunohistochemical distribution of the BM components in the CJ. Results indicated that the CJ exists IJS the fusion between a larger, myocardially derived BM and an attenuated, endothelial associated BM. Except for FN, the individual BM components were not all present during early stages. Instead, they appeared in a sequential manner, suggesting that all components of an adult-type B'A are not required to initiate the assembly of a structural and functional BM during development. In the AV and OT, FN lippeared as a progressively expanding gradient of material with the greatest density nearer the myocardium. An in vitro collagen gel bioassay was employed to directly test whether FN or other BM components play a role in EC and CM cell attachment, differentiation, and migration. Biochemical analysis and results from experiments using probes directed against the BH components indicated that mora than one mechanism of attachment, involving FN and/or HSPG, exist during EC development and CM cell migration.Item Regional and temporal analysis of sulfate labelled glycosaminoglycans during chick cardiac mesenchyme formation and migration(Texas Tech University, 1983-05) Funderberg, Fiona MargaretNot availableItem The effect of neuraminidase on cell surface and beat rate of aggregated myocardial cells(Texas Tech University, 1981-05) Barron, Emily AnnMorphological as well as physiological changes occur in aggregated embryonic chick myocardial cells after treatment with the sialic acid removing enzyme, neuraminidase (NMDase). Aggregates of seven day embryonic chick ventricular cells were prepared according to a procedure developed by DeHaan, including a plating sequence to remove most of the contaminating cell types. While muscle cells made up the majority (90%) of the core of the aggregate, there was an incomplete layer of fibroblasts (10%) covering the periphery. These beating spherical clumps of cells were then treated with two highly purified preparations of Clostridium perfringens neuraminidase. Roth preparations of enzyme were contaminated with variable amounts of a protein which electrophoretically comigrated with a known standard of C^. perfringens phospholipase C. Therefore, phospholipase C was used as a control in both the beat rate and cell surface studies. The morphological effect of NMDase on the available myocardial cells present at the aggregate's periphery was visualized using polycationic ferritin controlled by pH and acid methylation procedures. NMDase treatment (1.2 Units/ml for 2 hrs. at 37° C) on both prefixed and postfixed aggregates showed a reduction in stain at the cell surface. Although lower concentrations or shorter treatment times with NMDase showed little morphological change from controls, physiological differences in aggregate beat rate could be detected with only 0.03 U/ml after ten minutes. NMDase concentrations, 0.03, 0.5, and 1.2 U/ml, showed net decreases in beat rates over a sixty minute incubation. Within this period, the first thirty minutes displayed definitive decreases in aggregate beat rate while the rest of the hour was typified by arrhythmic contractions. This study demonstrates that NMDase reduces the number of anionic sites at the cell surface of embryonic myocardial cells and also reduces the aggregate beat rate.