Meristic characters in offspring from 27 pairs of medaka were investigated with respect to some factors known to alter metabolism. Temperature, light, thyroxine, thiourea, dinitrophenol, urethan and salinity were tested. Egg size, egg density, nature of rearing containers, quality of successive day's egg batches from the same parent, mechanical shock of developing eggs and pricking the chorion of eggs were also studied as possible factors producing meristic variations. Mean vertebral counts showed a V-shaped relation to temperature in 9 out of 15 replications, inverse relation in 2, and no consistent relation in 4. Pectoral fin ray counts were inversely related to temperature. Degree and direction of change of other fin rays with temperature varied between genotypes. Vertebral counts were not affected by variations in light intensities or duration; fin ray counts were altered but their reaction lacked uniformity. Mean total vertebral counts of 8 out of 11 replications were altered in thyroxine solution, but magnitude and direction of change differed between genotypes. When eggs were hatched in thyroxine solution, pectoral ray counts were lowered. Exposure of larvae to thyroxine produced significant decrease in pectoral, anal, dorsal, and caudal fin ray counts. Rearing eggs to hatching in thiourea produced significant increase in mean total vertebral counts in only 2 of 11 replications. Pectoral and anal fin ray counts increased, but total caudal rays decreased, in samples from treated eggs as well as from larvae treated in thiourea after hatching. Rearing of eggs to hatching in dinitrophenol, urethan, or sea water resulted in an increase in mean vertebral counts. Pectoral rays increased in lower concentrations of dinitrophenol, or in urethan, but were unaffected in sea water. Anal, dorsal, and total caudal rays were not altered in sea water, but variable effects resulted from dinitrophenol or urethan. No correlation was found between meristic counts and egg size. Vertebral and pectoral ray counts seemed to follow those of the father; paternal influence was very pronounced in inheritance of pectoral rays. Vertebral, pectoral and dorsal ray counts were not affected by other extraneous factors tested. Effect of egg density of anal and total caudal rays was variable. Final fixation of total vertebrae occurred at the embryonic stage when eye pigmentation commenced and pectoral buds had appeared. Other characters remained sensitive to environmental influence even after hatching The relation of metabolism to meristic characters, and evident parallels between effects of the several factors used are discussed. / Science, Faculty of / Zoology, Department of / Graduate

La règlementation européenne requiert l’évaluation de la reprotoxicité des ingrédients cosmétiques sans avoir recours aux tests sur les organismes définis par la directive européenne sur les animaux utilisés à des fins scientifiques. Pour cribler par exclusion des substances chimiques, l’industrie cosmétique a besoin de développer une méthode alternative à l’expérimentation animale prédictive et spécifique à l’identification d’agents tératogènes (substances entraînant au cours du développement embryonnaire et de manière définitive des malformations physiques et/ou fonctionnelles). Pour cela, le poisson zèbre, le poisson médaka et l’amphibien xénope aux stades embryonnaires ont été évalués sur une liste de 43 substances de référence. Le médaka a été sélectionné pour la fiabilité de son approvisionnement, la robustesse de ses stades embryonnaires lors des manipulations, ainsi que pour les performances du test l’utilisant. De plus, ce test permet de détecter les agents tératogènes les plus puissants, près de la moitié des 26 substances tératogènes de notre liste. Son taux de spécificité est fixé à 100% pour identifier correctement les 17 substances négatives dont l’absence d’effets tératogènes chez l’homme ou un organisme modèle mammifère, est avérée. Néanmoins, les performances de ce test pourraient être améliorées par son automatisation et par l’intégration de la quantification de nouveaux paramètres pour l’identification de malformations fonctionnelles. Enfin, pour prédire l’innocuité d’une substance chimique chez l’Homme, le test prédictif de tératogénicité utilisant les embryons de médaka doit être intégré dans une stratégie globale d’évaluation de la tératogénicité. / European legislation requires the assessment of reproductive toxicity of cosmetic ingredients without using tests on the organisms defined by the European directive on animals used for scientific purposes. To screen by excluding chemicals, cosmetics industry needs to develop an alternative method to animal testing, which needs to be predictive and specific in identifying teratogen agents (during embryonic development substances causing definitive physical and / or functional defects). For this, zebrafish, medaka fish and Xenopus amphibian at embryonic stages were assessed on a list of 43 reference substances. Medaka has been selected to the reliability of its supply, the robustness of its embryonic stages during handling, as well as for performance of its test. In addition, this test can detect the most potent teratogen agents, nearly half of the 26 teratogens of our list. Its specificity rate is set at 100% for correctly identifying 17 negative substances for which the absence of teratogenic effects is proved in humans or mammalian model organism. However, the performance of this test may be improved by its automation and integration of new quantification parameters for the identification of functional defects. Finally, to predict the safety of a chemical in humans, the predictive teratogenicity test using medaka embryos must be integrated into a comprehensive strategy for assessing the teratogenicity.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

The relationship between egg size and larval viability, as inferred from size at hatching, resistance to starvation, and growth, was studied in the Medaka, Oryzias latipes (Temminck and Schlegel) , and the Surf Smelt, Hypomesus pretious pretiosus (Girard). Medaka larvae which hatched from heavier eggs were larger at hatching, but did not survive longer during starvation. When the larvae were fed a small and varied food, neither relative growth rate nor relative body depth was correlated with original egg weight. However, when larvae were fed a large mobile prey, Paramecia multimicronucleatum, the larger the egg they came from the faster they grew. Thus, the advantage of large size at hatching is partially a function of the feeding conditions at hatching. In Surf Smelt, egg weight was correlated with maternal age. Two-year-old females produced eggs that were 50% heavier than those of one-year-old females, and hatchlings that were heavier and almost 1 mm longer. Smelt larvae with the most yolk reserve (yolk vol/length) at hatching survived longer, and the amount of reserve was correlated with egg dry weight. The larvae failed to feed in the laboratory. The effect of egg size on larval growth suggests that uncontrolled variation in egg size would affect experimental results, and may be important in commercial fishery management. / Science, Faculty of / Zoology, Department of / Graduate

Memoria para optar al título de Bioquímica / Las asimetrías cerebrales en el eje izquierda-derecha de vertebrados poseen componentes altamente conservados y son un punto importante de estudio para la biología del desarrollo. Entre estas asimetrías, las más estudiadas se encuentran en el epitálamo, una región ubicada en el diencéfalo dorsal de vertebrados cuyas conspicuas asimetrías poseen un importante factor hereditario y de lateralidad. En esta región, se encuentra la presencia de un par de núcleos habenulares (Hb, órgano par), además se encuentra el complejo pineal formado por el órgano pineal (órgano impar) en la línea media y por el órgano parapineal (Opp) que se encuentra a la izquierda y proyecta axones eferentes hacia la habénula ipsilateral. En este trabajo se realizó un estudio comparado entre dos especies de teleósteos, pez cebra (D. rerio) y pez medaka (O. latipes), para intentar dilucidar como se generan las características conservadas y especie-específicas durante la ontogenia del epitálamo. Estudios realizados en nuestro laboratorio demostraron que estos teleósteos poseen variaciones morfotopológicas especie-específicas en la región del epitálamo (heterotopías) y, luego de normalizar los tiempos de desarrollo en ambas especies, se comprobó que también existen variaciones en la temporalidad del desarrollo (heterocronías). La heterocronía más significativa es que las proyecciones Opp de pez medaka se desarrollan antes que en pez cebra. Debido a lo anterior, se puede hipotetizar que las diferencias topológicas observadas entre ambas especies podrían tener relación con la temporalidad de desarrollo de los componentes que forman el circuito Opp-Hb. En este contexto, el momento en que ocurre la interacción entre el Opp y la Hb podría ser un factor importante para definir la citoarquitectura final del circuito. Lo anterior se respalda en el hecho de que en pez cebra las células habenulares tienen distinta temporalidad de proliferación en cada núcleo, lo que genera subnúcleos habenulares lateral y medial, de distintos tamaños. Este rasgo asimétrico sería dependiente de la presencia del órgano parapineal, ya que a cada subnúcleo se han asociado marcadores moleculares cuya expresión suele ser asimétrica, pero ésta se pierde cuando el Opp es ablacionado. Por otra parte, la neurogénesis habenular, posee asimetría izquierda en su inicio, la cual se conserva incluso luego de ablacionar el Opp, lo que la define como un rasgo asimétrico independiente de la presencia del Opp. Luego, si suponemos que estas interacciones son conservadas también en el modelo de pez medaka, las eventuales variaciones heterocrónicas pueden estudiarse para comprender como podrían generarse las diferencias topológicas entre ambos teleósteos. Por lo tanto, el objetivo de este trabajo fue dilucidar si estas características se encuentran conservadas y observar de qué manera podría influir el adelantamiento de las proyecciones del Opp. Se esperaba que la neurogénesis habenular de pez medaka inicie de manera asimétrica en el mismo momento de desarrollo que pez cebra. Por otro lado, se esperaba que la proliferación celular, al ser un evento dependiente del Opp, se inicie antes debido al adelantamiento de la ontogenia del Opp. Para estudiar lo anterior se utilizó el marcador pan neuronal HuC, para identificar neuronas diferenciadas y se usaron marcadores moleculares que en pez cebra se asocian al dominio de los subnúcleos habenulares. Los resultados de nuestro estudio demostraron nueva evidencia de heterotopía y heterocronía entre pez cebra y medaka, se descartó la hipótesis planteada, pues la neurogénesis habenular en pez medaka está adelantada pero continúa siendo asimétrica en su inicio, lo que podría indicar que en esta especie sí existe una relación entre el Opp y la neurogénesis habenular. Por otro lado, con el gen nptx2a, ortólogo de narp de pez cebra, se encontró un arreglo topológico diferente a la asimetría izquierda esperada con narp, pues el marcador de pez medaka es más simétrico y se limita a una región más pequeña en ambas habénulas, asemejándose más a una topología propia a la descrita en la habénula derecha de pez cebra. Nuestros estudios respaldan la idea de que las interacciones entre el Opp y la HbI parecen ser más complejas de lo que los estudios en pez cebra revelan. Nuestros resultados sugieren interacciones más tempranas y probablemente bidireccional entre la habénula izquierda y el órgano parapineal / Brain asymmetries along the left-right axis show highly conserved components across vertebrates. Among these asymmetries the most studied is found in the epithalamus, a region located in the dorsal diencephalon. Epithalamic asymmetries are conspicuous and genetically controlled, and are characterised by the presence of left-right differences in morphology and gene expression of the bilaterally paired habenular nuclei and by the left-sided asymmetric position and connectivity to the left habenula (Hb) of the unpaired parapineal organ (PpO), an accesory component of the pineal complex. In this work we performed a comparative study between two species of teleosts, zebrafish (D. rerio) and medaka (O. latipes), to elucidate how the conserved and species-specific features of epithalamic asymmetries are generated during the ontogeny of the epithalamus. Previous studies of our laboratory showed that these teleosts show both topological and temporal variations in the development of epithalamic asymmetries, known as heterotopies and heterochronies, respectively. Among the latter, the most significant difference is observed in the timing of connectivity of the parapineal organ to the left Hb, which in medaka fish begins earlier than in zebrafish. Due to the above, we hypothesised that the topological differences observed between both species could be related to the temporality of development of the components that make up the parapineal-habenula circuit. In this context, the time in which the interaction between the parapineal organ and the habenula occurs could be an important factor in defining the final cytoarchitecture of the circuit. This idea is supported by the fact that in zebrafish the habenular cells have different temporality of proliferation in the left and right nuclei, which generates size differences in the lateral and medial habenular subnuclei on both sides. This asymmetric trait appears to depend on the presence of the parapineal organ, since the asymmetric expression of the molecular markers that have been associated to each habenular sub-nuclei is lost when the parapineal organ is physically removed during development. In contrast, the onset of habenular neurogenesis is asymmetric even after ablating the PpO, which defines a type of asymmetry that is independent of the parapineal organ. Based on the above and if we assume that these types of asymmetries are also conserved in medaka, the heterochronic variations can be studied as a possible factor that explains how the topological differences of epithalamic asymmetry between both teleosts are generated. Therefore, the aim of this work was to have a first mechanistic approach to this question and investigate the timing and organisation of habenular neurogenesis in medaka and relate this to the pattern observed in zebrafish and the advancement of parapineal projections in both species. Habenular neurogenesis of medaka was expected to start asymmetrically at the same time as in zebrafish while cell proliferation, being an event dependent of the parapineal organ, it was expected to start earlier due to overtaking of parapineal projections in this species. The pan-neuronal marker HuC was used to identify differentiated neurons and molecular subnuclei. The results of this study provided new evidence of heterotopic and heterochronic shifts between zebrafish and medaka that appear to rule out our hypothesis. The onset of habenular neurogenesis in medaka was asymmetric as in zebrafish but appeared at an earlier stage. This observation suggest that in contrast to zebrafish, the onset of asymmetric habenular neurogenesis in medaka has some type of dependency on the parapineal organ. This possibility can be assesed in the future by performing parapineal ablation in medaka. On the other hand, using the medaka nptx2a gene, an ortholog of zebrafish narp, we observed a different topological arrangement with a more restricted and fairly symmetric habenular expression, in contrast to the broad and pronounced left-sided asymmetric expression observed in zebrafish. This expression pattern resembles the topology described in the right habenula of zebrafish. In summary, our studies support the idea that interactions between the parapineal organ and the left Hb are more complex than the studies of zebrafish suggest. These interactions appear to have an earlier onset and show a bi-directional nature / FONDECYT; CONICYT; FONDAP; Iniciativa Científica Milenio, ICM P-09-015-F

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains viii, 69 p. : ill., maps. Includes abstract. Includes bibliographical references.

Thesis (M.S.)--Ohio State University, 2005. / Includes bibliographical references (leaves 86-98). Available online via OhioLINK's ETD Center

Call number: LD2668 .T4 1984 S326 / Master of Science

Foodborne toxins include a variety of biologically produced toxins and process-induced toxicants. Among them, marine algal toxins in polluted seafood can induce serious harmful effects on human, while heat-induced toxicants remain in a wide range of food and chronically affect health. In this present study, several representative toxins from these two categories were selected and studied, they are, brevetoxins (PbTxs), saxitoxin (STX) and acrolein (ACR). During past decades, the molecular actions of these toxins have been well studied, however, their effects and mechanisms corresponding to their sublethal toxicity in vivo still need more investigation. Therefore, in our current study, we adopted medaka fish (Oryzias melastigma) and zebrafish (Danio rerio) as models to study the toxicological responses and pathways of these selected toxins at the molecular and cellular level. In the first part of study, the targeted organs of medaka fish, gills and brains, were studied in medaka fish after exposure to the sublethal level of PbTx-1, the most potent neurotic shellfish poisoning (NSP) toxin. Facilitated by the two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ ionization tandem time-of-flight mass spectrometry (MALDI TOF/TOF MS), proteins affected by PbTx-1 in these organs were identified, including myosin like proteins, aldose reductase, gelsolin and keratin. Collectively, the proteins altered after exposure suggested the altered calcium ion binding process, and dysfunction in cytoskeleton assembly and metabolism. After successfully applying the fish model and proteomic approaches in the NSP toxin study, we put emphasis on the developmental toxicity of foodborne toxins, as children are more sensitive and vulnerable to foodborne toxins. Among the marine algal toxins, paralytic shellfish poisoning (PSP) toxins are the commonest and most lethal ones with STX as the most potent PSP toxin. Therefore, we examined the developmental effects of STX using medaka model. By exposing medaka embryos from the early blastula stage onwards, which covered the main developmental stage of the central nervous system and somites, we found newly hatched medaka fish exhibit abnormal growth with longer body length and relatively smaller yolk sac size. High cell proliferation, neuron development, and metabolism were confirmed by whole-mount immunostaining and 2-DE. In summary, STX disturbs the normal growth of medaka embryos probably by affecting the metabolic rate in the exposed medaka embryos. Opposite to STX, after exposure to ACR, a pollutant that ubiquitously exists in food and environment, the zebrafish exhibited delayed development. ACR is a known glutathione (GSH) depleting factor and oxidative stress inducer. Apart from developmental retardance, increased reactive oxygen species (ROS) and inflammation were found in newly hatched zebrafish, suggesting the developmental delay may be partly related to the ACR-induced oxidative stress. In summary, findings from the present study highlighted the molecular responses and possible pathways of some selected foodborne toxins. Developmental effects and toxicity were also found after exposing to both the biologically produced toxin and the heat-produced toxicant. Our current study makes contributions to the knowledge on the hazardous effects of foodborne toxins in vivo, and provides useful information for the further study on the human health. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy