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Effects of a Methylcholanthrene-Induced Lymphosarcoma on the Blood of DBA/1J Mice

Description: This investigation was concerned with characterizing a tumor line induced and maintained in this laboratory. Various chemical assays, cell counts, and electron microscopy were the methods employed to characterize the blood of mice bearing the tumor at days 3, 6, 9, and 12 after injection of the 1.2 x 10^8 tumor cells.
Date: May 1972
Creator: Lindsey, Jerri Kay

Studies on the Morphology and Biology of Cotton Rats (Sigmodon hispidus) from Northern Mexico to Southern Nebraska

Description: This investigation was designed to evaluate the need for retaining both Sigmodon hispidus texianus and Sigmodon hispidus berlandieri as subspecific designations. An attempt was made to demonstrate bioclimatic variation and reproductive seasonality in cotton rats. The validity of applying the results of isolated studies of cotton rat populations to the species as a whole was examined.
Date: December 1971
Creator: Cleveland, Arthur Gordon

Some Acute Effects of X-Irradiation (LD100) on Plasma and Adrenal Tissue Histamine in Rats

Description: The effects of a lethal dose (1380 r) of X-irradiation on plasma and adrenal tissue histamine levels of rats were studied. The plasma histamine response was triphasic (increase at 1-3 hours, decrease at 5 and 9 hours and return to control at 24 hours post-irradiation). The adrenal tissue histamine response was found to be biphasic (decrease at 1 to 9 hours and a return to control level at 24 hours post-irradiation).
Date: May 1972
Creator: Ferguson, James L.

Obligately Thermophilic Nitrogen-Fixation in Some Soil Bacteria

Description: In the work presented here, it is claimed that bacteria have been isolated which are capable of growth at high temperatures utilizing molecular nitrogen as their sole nitrogen source. Soil bacteria were isolated which grew at 55 C in nitrogen-free media. They were found to be obligatory thermophiles in nitrogen-free media and facultative thermophiles in media containing organically bound nitrogen.
Date: August 1971
Creator: Milam, Mary

Some Effects of Electrostatic Fields on Brain Activity in Rats

Description: This study concerned the effects of short-term exposures to continuous (10 kv/meter) and pulsed 20 volts at 640 cps/100 msecs) electrostatic fields on the EEG recorded from external electrodes and hypothalamic activity recorded from implanted electrodes in rats. Each experiment lasted at least 90 minutes. The total energies of the waveforms recorded were integrated and printed out for plotting and analysis. Besides the brain activity, the ECG, respiration, and temperature of the animals were also monitored before, during,and after exposure to the electrostatic fields.
Date: December 1971
Creator: McCain, Harry B.

Nucleotide Sequence of a Bovine Arginine Transfer RNA Gene

Description: A single plaque-pure lambda clone designated λBA84 that hybridized to a ˆ32P-labeled bovine arginine tRNA was isolated from a bovine genomic library harbored in a lambda bacteriophage vector. A 2.3-kilobase segment of this clone was found to contain an arginine transfer RNAccg gene by Southern blot hybridization analysis and dideoxyribonucleotide DNA sequencing. This gene contains the characteristic RNA polymerase III split promoter sequence found in all eukaryotic tRNAs and a potential RNA polymerase III termination site, consisting of four consecutive thymine residues, in the 3'-flanking region. Several possible cis-acting promoter elements were found within the 5'-flanking region of the sequenced gene. The function of these elements, if any, is unknown.
Date: May 1996
Creator: Eubanks, Aleida C. (Aleida Christine)

Subcellular Localization of N-acylphosphatidyl-ethanolamine Synthase in Cotyledons of Cotton Seedlings

Description: N-acylation of phosphatidylethanolamine (PE) with free fatty acids catalyzed by N-acyl phosphatidylethanolamine (NAPE) synthase was reported in cotyledons of 24-h-old cotton seedlings. Here I report subcellular localization of this enzyme. Differential centrifugation, sucrose density gradient fractionation,aqueous two-phase partitioning and electron microscopy techniques were utilized to elucidate subcellular site(s) of NAPE synthase. Marker enzymes were used to locate organelles in subcellular fractions. Differential centrifugation indicated that NAPE synthase is present in more than one organelle and it is a membrane bound enzyme. Sucrose density gradient fractionations indicated that NAPE synthase is present in membranes derived from endoplasmic reticulum (ER),Golgi and possibly plasma membrane (PM) but not mitochondria, glyoxysomes or plastids. Aqueous two-phase partitioning experiments with cotton and spinach tissues supported these results but Goigi appeared to be the major site of NAPE synthesis. Electron microscopy of subcellular fractions was used to examine isolated fractions to provide visual confirmation of our biochemical results. Collectively, these results indicate that NAPE is synthesized in plant ER, Golgi and possibly PM.
Date: December 1995
Creator: Sriparameswaran, Anuja

Comparative Bioavailability of Dietary and Dissolved Cadmium to Freshwater Aquatic Snails

Description: Heavy metal bioaccumulation in aquatic organisms may occur through direct or indirect uptake routes. Research indicates that the significance of uptake route varies with contaminant and organism exposed. The relative importance of different metal sources in aquatic systems was investigated by exposing freshwater snails to dietary or dissolved sources of cadmium. Snails were exposed to control, contaminated food only, contaminated water only, and contaminated food and water treatments. During the 15-day exposure, samples were taken to determine Cd concentration in snail soft tissue, snail shell, algal food, and overlying water. Analyses of snail soft tissue and shells indicate that exposure route significantly affects Cd concentrations in the tissues. In both cases, dissolved Cd is the primary contributor to metal body burden.
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Date: December 2003
Creator: White, Jessica C.

Pyrimidine Genes in Pseudomonas Species

Description: This thesis is a comparative study of gene arrangements in Pseudomonas species, and is organized into three major sections. The first section compares gene arrangements for different pathways in Pseudomonas aeruginosa PAO1 to determine if the gene arrangements are similar to previous studies. It also serves as a reference for pyrimidine gene arrangements in P. aeruginosa. The second part compares the physical, and genetic maps of P. aeruginosa PAO1 with the genome sequence. The final section compares pyrimidine gene arrangements in three species of Pseudomonas. Pyrimidine biosynthesis and salvage genes will be aligned for P. aeruginosa PAO1, P. putida KT2440, and P. syringae DC3000. The whole study will gives insight into gene patterns in Pseudomonas, with a focus on pyrimidine genes.
Date: December 2003
Creator: Roush, Wendy A.

The Ecology and Paleobiogeography of Freshwater Mussels (Family: Unionidae) from Selected River Basins in Texas

Description: This dissertation has two overall objectives: first, to demonstrate the utility of paleozoological data for ongoing and future mussel-conservation efforts in Texas and second, to evaluate whether simple measures of habitat (e.g., water depth, velocity and particle size) are important for demonstrating the within-habitat spatial separation of mussels. Although these topics may seem disparate, both are important for increasing our understanding of unionid ecology and biogeography. Chapters 1 through 3 examine the use of paleozoological data for mussel conservation. Although these types of data are not new they have rarely been used in mussel conservation efforts within Texas. This is unfortunate because paleozoological data can provide an excellent record of the mussel fauna prior to wide-scale modern impacts and in areas where historical survey data are lacking. Chapter 4 examines whether assessments of microhabitat for mussels using simple measures of habitat (e.g., water velocity, depth and particle size) are useful. Recent studies have suggested that these measures do not explain the mussel distribution in flowing streams. If this is correct, instream flow studies using this approach need to be revised. Results of Chapter 4 indicate that mussels in the lower Brazos River basin are constrained in distribution by the availability of heterogenous substrate. Appendix A, details the first account of a living population of Truncilla macrodon, which is a candidate species for the Endangered Species Act (ESA). The population was found while conducting mussel instream flow studies in the lower Brazos River basin.
Date: May 2011
Creator: Randklev, Charles R.

Structure-Function Studies on Aspartate Transcarbamoylase and Regulation of Pyrimidine Biosynthesis by a Positive Activator Protein, PyrR in Pseudomonas putida

Description: The regulation of pyrimidine biosynthesis was studied in Pseudomonas putida. The biosynthetic and salvage pathways provide pyrimidine nucleotides for RNA, DNA, cell membrane and cell wall biosynthesis. Pyrimidine metabolism is intensely studied because many of its enzymes are targets for chemotheraphy. Four aspects of pyrimidine regulation are described in this dissertation. Chapter I compares the salvage pathways of Escherichia coli and P. putida. Surprisingly, P. putida lacks several salvage enzymes including nucleoside kinases, uridine phosphorylase and cytidine deaminase. Without a functional nucleoside kinase, it was impossible to feed exogenous uridine to P. putida. To obviate this problem, uridine kinase was transferred to P. putida from E. coli and shown to function in this heterologous host. Chapter II details the enzymology of Pseudomonas aspartate transcarbamoylase (ATCase), its allosteric regulation and how it is assembled. The E. coli ATCase is a dodecamer of two different polypeptides, encoded by pyrBI. Six regulatory (PyrI) and six catalytic (PyrB) polypeptides assemble from two preformed trimers (B3) and three preformed regulatory dimers (I2) in the conserved 2B3:3I2 molecular structure. The Pseudomonas ATCase also assembles from two different polypeptides encoded by pyrBC'. However, a PyrB polypeptide combines with a PyrC. polypeptide to form a PyrB:PyrC. protomer; six of these assemble into a dodecamer of structure 2B3:3C'2. pyrC' encodes an inactive dihydroorotase with pyrB and pyrC' overlapping by 4 bp. Chapter III explores how catabolite repression affects pyrimidine metabolism. The global catabolite repression control protein, Crc, has been shown to affect pyrimidine metabolism in a number of ways. This includes orotate transport for use as pyrimidine, carbon and nitrogen sources. Orotate is important because it interacts with PyrR in repressing the pyr genes. Chapter IV describes PyrR, the positive activator of the pyrimidine pathway. As with other positive activator proteins, when pyrimidine nucleotides are depleted, PyrR binds to ...
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Date: December 2003
Creator: Kumar, Alan P.

Analysis of a Cotton Gene Cluster for the Antifungal Protein Osmotin

Description: Three overlapping genomic clones covering 29.0 kilobases of cotton DNA were found to encompass a cluster of two presumptive osmotin genes (OSMI and OSMII) and two osmotin pseudogenes (OSMIII and OSMIV). A segment of 16,007 basepairs of genomic DNA was sequenced from the overlapping genomic clones (GenBank Accessions AY303690 and AF304007). The two cotton osmotin genes were found to have open reading frames of 729 basepairs without any introns, and would encode presumptive osmotin preproteins of 242 amino acids. The open reading frames of the genes are identical in sequence to two corresponding cDNA clones (GenBank Accessions AF192271 and AY301283). The two cDNA inserts are almost full-length, since one lacks codons for the four N-terminal amino acids, and the other cDNA insert lacks the coding region for the 34 N-terminal amino acids. The cotton osmotin preproteins can be identified as PR5 proteins from their similarities to the deduced amino acid sequences of other plant osmotin PR5 preproteins. The preproteins would have N-terminal signal sequences of 24 amino acids, and the mature 24 kilodalton isoforms would likely be targeted for extracellular secretion. Prospective promoter elements, including two ethylene response elements, implicated as being positive regulatory elements in the expression of a number of PR-proteins, occur in the 5'-flanking regions. The mature osmotin proteins accumulate in cotton plants treated with the inducers ethephon and hydrogen peroxide. Thus, the two cotton osmotin genes encode osmotin proteins. The coding regions of the two genes have been expressed and isolated as fusion polypeptides in a bacterial expression system. Binary constructs containing the open reading frames of the two osmotin genes under the control of the 35S CaMV promoter have been generated for eventual production of transgenic Arabidopsis and cotton plants for potential constitutive expression of the osmotin proteins for increased resistance against fungal pathogens.
Date: December 2003
Creator: Wilkinson, Jeffery Roland

Microsatellite-based genetic profiling for the management of wild and captive flamingo populations.

Description: Flamingo species generate tremendous interest whether they are small captive groups or wild populations numbering in the thousands. Genetic pedigrees are invaluable for maintaining maximum genetic diversity in captive, as well as wild, populations. However, presently there is a general lack of genetic data for flamingo populations. Microsatellites are loci composed of 2-6 base pair tandem repeats, scattered throughout higher eukaryotic genomes, often exhibiting high levels of polymorphism and heterozygosity. These loci are thus important genetic markers for identity, parentage and population studies. Here, six microsatellite loci were isolated from a microsatellite-enriched Caribbean flamingo partial genomic library. Two are compound complex repeats and four are perfect trinucleotide repeats. Each locus was amplified from Caribbean, African greater, Chilean and lesser flamingo genomic DNAs. Heterozygosity frequencies were calculated for Caribbean (range 0.12-0.90) and African greater flamingos (range 0.23-0.94) loci. All six microsatellite loci were found to be in Hardy-Weinberg equilibrium and linkage disequilibrium analyses did not suggest linkage for any pair of two greater flamingo subspecies (African and Caribbean) loci. At least five of the loci also exhibit polymorphism in Chilean and lesser flamingos, but due to small sample numbers, relevant allele/heterozygosity frequency calculations could not be estimated. Nucleotide sequence comparisons of the amplicons derived from the four flamingo groups reveal a high level of sequence conservation at all loci. Although small sample numbers again limit the data for lesser flamingos and to some degree for the Chilean birds, the sequences of the two greater flamingo subspecies were identical and the number of nonconserved nucleotides appears to be higher for lesser/greater comparisons than for Chilean/greater comparisons. This is consistent with Chilean flamingos being a different species within the same genus as the greater flamingos, while lesser flamingos belong to a separate genus. Parentage analyses on suggested African greater flamingo family groups from ...
Date: December 2005
Creator: Kapil, Richa

Simulation of physical and chemical processes in reservoirs: Two case studies.

Description: Managing water quality aspects requires the use of integrative tools that allow a holistic approach to this problem. Water quality models coupled to hydrodynamic models are these tools. This study presents the application of the water quality model WASP coupled to the hydrodynamic model DYNHYD for two distinct reservoirs: Lake Texoma and Tocoma Reservoir. Modeling the former included simulations of water velocities, water level, and four chemical and physical compounds: chlorides, dissolved oxygen (DO), biochemical oxygen demand (BOD), and total suspended solids (TSS); and validation of the results by comparing with observed values during March - May, 1997. The latter is still under project status and the simulation was performed in a prospective way. The analysis included simulations of water velocities under current and for expected conditions, DO and BOD. Both models, DYNHYD and WASP, fitted pretty well to observed conditions for Lake Texoma and for where Tocoma Reservoir has been planned. Considering management and decision support purposes, the role of boundary and loading conditions also was tested. For Lake Texoma, controlling boundary conditions for chlorides is a determinant factor for water quality of the system. However, DO and TSS in the reservoir are governed by additional process besides the condition of the boundary. Estimated loadings for this system did not provided significant effects, even though the allocation of a load for chlorides resulted in significant changes in the trend for expected chloride concentrations at the Washita River Arm of Lake Texoma. For Tocoma Reservoir, the expected concentration of DO all over the reservoir is going to driven by boundary conditions, as well as by the management of autochthonous BOD loadings provided by vegetation decomposition. These two factors will be determinant for the resulting water quality of the future reservoir.
Date: December 2005
Creator: García Iturbe, Selma L.

Impaired virulence factor production in a dihydroorotate dehydrogenase mutant (pyrD) of Pseudomonas aeruginosa.

Description: Previous research in our laboratory showed that when knockout mutations were created in the pyrB and pyrC genes of the pyrimidine pathway in Pseudomonas aeruginosa, not only were the resultant mutants auxotrophic for pyrimidines but they were also impaired in virulence factor production. Such a correlation had not been previously reported for P. aeruginosa, a ubiquitous opportunistic pathogen in humans. In an earlier study it was reported that mutants blocked in one of the first three enzymes of the pyrimidine pathway in the non-pathogenic strain P. putida M produced no pyoverdin pigment while mutants blocked in the later steps produced copious amounts of pigment, just like the wild type. This study probed for the same connection between pyrimidine auxotrophy and pigment production applied in P. aeruginosa. To that end a knockout mutation was created in pyrD, the fourth step in the pyrimidine pathway which encodes dihydroorotate dehydrogenase. The resulting mutant required pyrimidines for growth but produced wild type pigment levels. Since the pigment pyoverdin is a siderophore it may also be considered a virulence factor, other virulence factors were quantified in the mutant. These included casein protease, hemolysin, elastase, swimming, swarming and twitching motility, and iron binding capacity. In all cases these virulence factors were significantly decreased in the mutant. Even supplementing with uracil did not attain wild type levels. Starvation of the pyrimidine mutant for uracil caused increased specific activity of the pyrimidine enzymes, suggesting that regulation of the pyrimidine pathway occurred at the level of transcription. This effect has also been reported for P. oleovorans. The present research consolidates the idea that pyrimidine auxotrophs cause decreased pathogenicity in P. aeruginosa. Such a finding may open the search for chemotherapy targets in cystic fibrosis and burn victims where P. aeruginosa is an infecting agent.
Date: December 2005
Creator: Ralli, Pooja

Genetic and Cellular Analysis of Anoxia-Induced Cell Cycle Arrest in Caenorhabditis elegans

Description: The soil-nematode Caenorhabditis elegans survives oxygen deprivation (anoxia < 0.001 kPa of O2, 0% O2) by entering into a state of suspended animation during which cell cycle progression at interphase, prophase and metaphase stage of mitosis is arrested. I conducted cell biological characterization of embryos exposed to various anoxia exposure times, to demonstrate the requirement and functional role of spindle checkpoint gene san-1 during brief anoxia exposure. I conducted a synthetic lethal screen, which has identified genetic interactions between san-1, other spindle checkpoint genes, and the kinetochore gene hcp-1. Furthermore, I investigated the genetic and cellular mechanisms involved in anoxia-induced prophase arrest, a hallmark of which includes chromosomes docked at the nuclear membrane. First, I conducted in vivo analysis of embryos carried inside the uterus of an adult and exposed to anoxic conditions. These studies demonstrated that anoxia exposure prevents nuclear envelope breakdown (NEBD) in prophase blastomeres. Second, I exposed C. elegans embryos to other conditions of mitotic stress such as microtubule depolymerizing agent nocodazole and mitochondrial inhibitor sodium azide. Results demonstrate that NEBD and chromosome docking are independent of microtubule function. Additionally, unlike anoxia, exposure to sodium azide causes chromosome docking in prophase blastomeres but severely affects embryonic viability. Finally, to identify the genetic mechanism(s) of anoxia-induced prophase arrest, I conducted extensive RNA interference (RNAi) screen of a subset of kinetochore and inner nuclear membrane genes. RNAi analysis has identified the novel role of 2 nucleoporins in anoxia-induced prophase arrest.
Date: December 2008
Creator: Hajeri, Vinita A.

Influence of copper on resistance of Lumbricus terrestris to bacterial challenge

Description: Earthworms, Lumbricus terrestris, were challenged orally and intracoelomically with two bacterial species, Aeromonas hydrophila and Pseudomonas aeruginosa, and mortality rates were observed. Neither were found to be particularly pathogenic at injected doses of up to 108 bacteria per earthworm. The influence of Cu++ (as CuSO4) on the earthworm's response to bacterial challenge was investigated by exposing earthworms to sublethal levels of Cu++ prior to bacterial challenge. Exposure at sublethal concentrations up to 3 m g/cm2 did not have a pronounced influence on host resistance to challenge as measured by earthworm mortality. Cu++ increased the earthworm's ability to agglutinate rabbit erythrocytes, indicating that Cu++ exposure caused coelomocyte death, autolysis and release of agglutinins into the coelom, possibly explaining resistance to bacterial challenge.
Date: August 2000
Creator: Simmons, Carla Stull

Endocannabinoid System in a Planarian Model

Description: In this study, the presence and possible function of endocannabinoid ligands in the planarian is investigated. The endocannabinoids ananadamide (AEA) and 2-arachidonoylglycerol (2-AG) and entourage NAE compounds palmitoylethanolamide (PEA), stearoylethanolamide (SEA) and oleoylethanolamide (OEA) were found in Dugesia dorotocephala. Changes in SEA, PEA, and AEA levels were observed over the initial twelve hours of active regeneration. Exogenously applied AEA, 2-AG and their catabolic inhibition effected biphasic changes in locomotor velocity, analogous to those observed in murines. The genome of a close relative, Schmidtea mediterranea, courtesy of the University of Utah S. med genome database, was explored for cannabinoid receptors, none were found. A putative fatty acid amide hydrolase (FAAH) homolog was found in Schmidtea mediterranea.
Date: December 2010
Creator: Mustonen, Katie Lynn

Induced Bradycardia Effects on Angiogenesis, Growth and Development in Early Development in Chicken Embryos, Gallus Domesticus

Description: Cardiac performance, angiogenesis and growth was investigated during early chicken development. Heart rate, and thus arterial pulse pressure and cardiac output, were altered with the bradycardic drug ZD7288. Heart rates at 72 h of development of control embryos and those dosed with chicken Ringer were not different at 171 bpm. Acute and chronic application of ZD7288 caused significant bradycardia. Chronic dosing of Ringer and ZD7288 changed neither eye diameter nor development rate. Chronic dosing of ZD7288 did not significantly alter CAM vessel density close to the embryo (2, 3 and 4 mm) but at farther distances (5 and 6 mm) chronic dosing with both Ringer and ZD7288 decreased vessel density by 13 - 16%. Chronic dosing with ZD7288 also reduced body mass by 20%. Thus, lowered heart rate and cardiac output had little effect on vessel density or developmental stage, but did reduce embryo growth.
Date: December 2010
Creator: Ruck, Sylvia A.

Photoactivatable Quantum Dots in Super-Resolution Microscopy of Muscle

Description: Super-resolution 3D imaging was achieved using newly synthesized photoactivatable quantum dot (PAQ dot) probes. Quantum dots were modified with a novel quencher system to make them photoactivatable. The unique properties of these PAQ dots enable single-fluorophore localization in three dimensions using a confocal microscopy optical sectioning method. Myosin and tropomyosin of rabbit myofibrilar bundles were specifically labeled with the newly synthesized PAQ dot. A sufficient number of single quantum dots were photoactivated, localized and reduced to their centroid and then reconstructed to a super-resolution image. The acquired super-resolution image shows a lateral and an axial sub-diffraction resolution and demonstrates ultrafine striations with widths less than 70 nm that are not evident by conventional confocal microscopy. The striations appear to be related to nebulin thin filament binding protein. This newly developed imaging system is cutting edge for its high resolution and localization as well its simplicity and convenience.
Date: December 2010
Creator: Akel, Amal

Expression analysis of the fatty acid desaturase 2-4 and 2-3 genes from Gossypium hirsutum in transformed yeast cells and transgenic Arabidopsis plants.

Description: Fatty acid desaturase 2 (FAD2) enzymes are phosphatidylcholine desaturases occurring as integral membrane proteins in the endoplasmic reticulum membrane and convert monounsaturated oleic acid into polyunsaturated linoleic acid. The major objective of this research was to study the expression and function of two cotton FAD2 genes (the FAD2-3 and FAD2-4 genes) and their possible role in plant sensitivity to environmental stress, since plants may increase the polyunsaturated phospholipids in membranes under environmental stress events, such as low temperature and osmotic stress. Two FAD2 cDNA clones corresponding to the two FAD2 genes have been isolated from a cotton cDNA library, indicating both genes are truly expressed in cotton. Model yeast cells transformed with two cotton FAD2 genes were used to study the chilling sensitivity, ethanol tolerance, and growth rate of yeast cells. The expression patterns of the two FAD2 genes were analyzed by reverse transcription polymerase chain reactions (RT-PCR) and Western blot analyses in cotton plants under different treatment conditions. The coding regions of both FAD2 genes were inserted downstream from the CaMV 35S promoter in the pMDC gateway binary vector system. Five different FAD2/pMDC constructs were transformed into the Arabidopsis fad2 knockout mutant background, and multiple potential transgenic Arabidopsis plant lines harboring the cotton FAD2 genes were generated. The cotton FAD2 genes were amplified by the polymerase chain reaction (PCR) from the genomic DNAs isolated from the transgenic Arabidopsis T1 plant lines. Complementation of the putative transgenic Arabidopsis plants with the two cotton FAD2 genes was demonstrated by gas chromatography analyses of the fatty acid profiles of leaf tissues. The cellular localization of cotton FAD2-4 polypeptides with N-terminal green fluorescence protein (GFP) was visualized by confocal fluorescence microscopy. The phenotype of transgenic Arabidopsis plants transformed with the cotton FAD2-4 gene was compared to Arabidopsis knockout fad2 mutant plants and wild ...
Date: August 2008
Creator: Zhang, Daiyuan

Morphological and physiological developmental consequences of parental effects in the chicken embryo (Gallus gallus domesticus) and the zebrafish larva (Danio rerio).

Description: Cardiac, metabolic and growth response of early-stage chicken embryos to perturbations in yolk environment was investigated. Also, effects of parental hypoxia exposure on hypoxia resistance, thermal tolerance and body length of zebrafish larvae were investigated. In the first study, thyroxine, triiodothyronine and testosterone produced differential effects on heart rate and development rate of chicken embryos during the first 4 days of development. Triiodothyronine caused a dose-dependent increase in heart rate when applied at 40 or 70 hours of age, while thyroxine caused a dose-dependent increase in heart rate when applied at 40 hours only. Testosterone and propyl-thiouracil (deiodinase antagonist) did not have an effect on heart rate. Development rate was not changed by thyroxine, triiodothyronine, testosterone or propyl-thiouracil, which suggested that heart rate changes did not result from changes in embryo maturity. In the second study, chicken embryos exposed to yolks of different bird species during early-stage embryonic development showed changes in heart rate, mass-specific oxygen consumption and body mass that scaled with the egg mass, incubation period length, and yolk triiodothyronine and testosterone levels of the species from which yolk was derived. In the third study, this phenomenon was investigated between layer and broiler chickens. Heart rate, oxygen consumption and body mass of broiler and layer embryos were significantly changed by a breed-specific change in yolk environment. Yolk triiodothyronine and testosterone concentrations of broiler and layer eggs did not suggest that these hormones were responsible for physiological and morphological changes observed. The final study demonstrated that hypoxia resistance and body lengths, but not thermal tolerance of zebrafish larvae was increased by parental hypoxia exposure.
Date: August 2008
Creator: Ho, Dao H.