Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 191-225). Available also in a digital version from Dissertation Abstracts.

During early development of Xenopus laevis, gastrulation is a key morphogenetic event which transforms the embryo into three of primary germ layers: ectoderm, mesoderm, and endoderm. In order for the physical separation of these layers to occur, cells have to acquire specific properties that distinguish one layer from another. These properties, which include cell adhesion and migration, should be reflected in the tissue-specific proteome. While genetic analysis has led to the determination of a number of proteins involved in germ layer formation, this method would not have identified those proteins regulated on a translational or post-translational level. In this study, we have developed a two-dimensional gel based comparative proteomic approach employing difference gel electrophoresis (DiGE) to identify proteins involved in germ layer morphogenesis during Xenopus gastrulation. Differences between the physical properties of the ectoderm and mesoderm are likely based on differences in the proteomes of the cell surface and/or cortex. We therefore analyzed plasma membrane enriched fractions, obtained using discontinuous sucrose density gradient centrifugation. The Decyder program was used to quantify expression changes with statistical confidence across multiple DiGE gels, provide independent confirmation of distinct expression patterns from the individual experiments, and demonstrate high reproducibility between replicate samples. The identity of 23 proteins, which were obtained from 33 analyzed spots, was determined using mass spectrometry. Our proteomic analysis of Xenopus ectoderm and mesoderm identified alterations in proteins involved in cytoskeletal organization, signal transduction, protein folding, vesicle trafficking, and in glycolysis. We have also demonstrated the feasibility of proteomics in Xenopus, and have therefore shown that proteomics may be a valuable tool for analysis of early development in this system.

No description available.

In 1897 Davenport measured the wet and dry weights of amphibian embryos from the stage of hatching onwards. He observed that there was a continuous increase in the wet weight but that the dry weight remained constant until the embryo began feeding. From this he concluded that "growth is due chiefly to imbibed water". Schaper (1902) noted a similar constancy of dry weight from the early tail bud stages until the time of feeding in embryos of Rana fusca. These early observations have been confirmed by Dempster (1933) who, working with Amblystoma punctatwn, extended his experiments to include the earliest developmental stages. The increase in volume, and hence the growth, of amphibian embryos is therefore due to the uptake of water from the environment. Many embryologists have attempted to correlate this water uptake with the osmotic pressure of the embryos. The early work in this field has been extensively reviewed by Needham (1931).

No description available.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2002. / Includes bibliographical references.

The vertebrate planar cell polarity (PCP) pathway has been previously found to control polarized cell behaviors rather than cell fate. We report here that disruption of Xenopus laevis orthologs of the Drosophila melanogaster PCP genes Xint or Xfy affected not only PCP-dependent convergent extension but also caused embryonic phenotypes consistent with defective Hedgehog signaling. These defects in Hedgehog signaling resulted from a broad requirement for Inturned and Fuzzy in ciliogenesis. We show that these proteins are necessary for the formation of both primary cilium in the neural tube and multi-cilia in the epidermis. Also, using Xenopus muco-ciliary epidermis, we demonstrated that one of the core PCP genes Dishevelled performs dual functions in ciliogenesis, basal body docking and planar polarization of ciliary beating. To this end, we showed that Dishevelled works in concert with the PCP effector protein Inturned and Rho GTPase to mediate the docking of basal bodies to the apical cell surface. We suggest that this docking involves a Dvl-dependent association of basal bodies with vesicles, and with the vesicle-trafficking protein Sec8. Finally, we showed that independent of their roles in apical docking, Dvl/PCP signaling is required again for directional ciliary beating. For the first time, this study uncovered the mechanism for controlling the apical docking of basal bodies. Moreover, the results suggest that the same Dvl/PCP signaling is also important for the planar polarization of ciliary beating in a vertebrate muco-ciliary epithelium. / text

All-trans retinoic acid (atRA) is an important morphogen in many developmental processes, including apoptosis, growth, organogenesis and differentiation. During the early embryonic development, atRA is synthesized in an irreversible reaction from all-trans retinal (atRAL), catalyzed mainly by retinal dehydrogenase 2 (RALDH2). The upstream metabolic pathway, including the redox reaction between all-trans retinol (atROL) and atRAL, mediated by short-chain dehydrogenase/reductase, however, is less understood during embryonic development. / Previously a Xenopus laevis short-chain dehydrogenase/reductase 3 (dhrs3) was identified as a gene differentially expressed in the Spemann-Mangold Organizer. In this study, dhrs3 was found to be expressed in the circumblastoporal ring, neuroectoderm and pronephros region, and was up-regulated by atRA signalling. By using loss-of-function and gain-of-function approaches, it was found that the phenotype induced by knockdown of dhrs3 mimicked those with an elevated level of atRA signalling, and overexpression of dhrs3 enhanced the phenotype of cyp26a1, which functions in degradation of atRA. In dhrs3 knock-down embryos (morphants), expression domain of the mesoderm markers brachyury was disrupted, and that of organizer marker lim1 were significantly expanded, suggesting altered mesoderm induction. Overexpression of dhrs3, on the other hand, exerted an opposite effect on lim1 by reducing its expression. dhrs3 also rescued the phenotype following raldh2 overexpression induced by exogenous atRAL, suggesting that dhrs3 competed with raldh2 for the same substrate, atRAL. In line with these findings, expression of the mid-brain, hindbrain and neural crest markers was posteriorized in dhrs3-overexpressing embryos, similar to the phenotype of atRA-deficient embryos induced by cyp26a1. These findings indicate that dhrs3 participates in the retinoid metabolism by reducing atRAL to atROL. / Xenopus dhrs3 morphants displayed a shortened anteroposterior axis, similar to that of atRA toxicity. Examination of convergent extension (CE) markers papc indicated a defect in the CE movement, which was also evidenced by the disrupted bra and not expression. Overall, the results of the present study suggest that dhrs3 regulates proper mesoderm patterning through regulating the CE movement. / Kam, Kin Ting. / Advisers: Yu Pang Eric Cho; Wood Yee Chan; Hui Zhao. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves [158]-184). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

糖調節蛋白78 (Glucose-regulated protein 78),也稱之Bip,是70kDa熱休克蛋白家族成员之一。已有的研究表明，Bip 是一個具有多功能的蛋白，參與眾多的生物調控過程，包括蛋白折疊，調節鈣平衡，以及作為內質網緊張（ER stress) 的感應器。有研究表明，Bip可以在細胞膜上定位，作為Nodal信號通路的一個輔助受體發揮作用。大量的研究表明，Bip在疾病和代謝方面也發揮重要作用。它參與胰島素的生物合成，並可以提高長期高血糖下β細胞的功能。同時具有抗細胞凋亡的作用。然而Bip在胚胎髮育中的生物功能卻知之甚少。 / 高等脊椎動物腎臟發育中經歷形成3種腎臟形式：前腎，中腎和後腎。腎單位是這3種形式的基本結構和功能單位。在兩棲類，前腎在胚胎時期發揮作用，在胚胎的兩側各只有一個腎單位。這使得爪蟾成為前腎研究的一個非常好的模型。 / 在此項研究中，我們採用非洲爪蛙作為動物模型來研究Bip在胚胎髮育過程中，尤其是在前腎發育中的生物功能。Bip是一個母性因子，在尾芽期，Bip 表達在粘液腺，前腎，肝以及耳囊。 Bip在前腎清晰明確的表達，表明Bip可能在前腎的發育中發揮作用。我們利用BipMO來進行敲低功能實驗，免疫印記顯示BipMO能阻斷帶Flag標記Bip的翻譯。通過原位雜交技術檢測前腎的不同標記基因的表達發現，敲低Bip抑制前腎的形成，表明Bip的正常表達是前腎發育所必須的。 / 為了研究Bip調節前腎的發育的分子機制， 我們使用Affmetrix基因芯片分析在Bip敲低情況下的不同時期胚胎中基因的表達譜，發現在Bip敲低表達的胚胎中，視黃酸信號通路的一些重要的組分的表達受到抑制。爪蛙胚胎原腸胚的動物帽細胞具有多能性， 使用激活素和視黃酸一同處理動物帽細胞可以誘導其分化成為原腎組織。在此體外分化體系中敲低Bip表達，前腎標記基因表達降低，顯示在這一體外系統中前腎的分化受到抑制。該實驗結果與體內實驗結果一致。在體外培養的HEK293T細胞中敲低Bip，抑制視黃酸處理後視黃酸信號通路螢光素報告的活性。 lhx1是前腎發育早期表達標記之一，對於前腎原基的初始化具有重要的作用，同是它也是視黃酸信號通路的靶基因。共同註射BipMO和lhx1表明，前腎的異常可以明顯降低，顯示lhx1可以部份拯救由於Bip缺失所造成的腎臟發育缺陷。該實驗表明Bip通過調節視黃酸信號通路，來調控lhx1的表達前腎的形成。我們進一不發現，敲低Bip後，前腎異常形成的區域內，細胞凋亡增加，增殖減少。該結果在細胞水平上解釋了Bip敲低表達時前腎形成異常的一個原因。 / 综述所述，Bip正確表達对胚胎前肾的发育極為重要。它胚胎发育过程中通过視黃酸信号通路調控lhx1的表達，從而对前肾的形成发挥重要作用。 / Glucose-regulated protein 78 (Grp78), also known as Bip, belongs to heat shock protein 70kDa family. It has been implicated in various biological processes including protein folding, regulation of calcium homeostasis, and serving as a sensor of ER (Endoplasmic Reticulum) stress. Moreover, it can localize in cell membrane, acting as co-receptor of nodal signaling. It is essential for insulin biosynthesis. In addition, Bip plays important roles in a number of diseases. For example, BIP can improve β-cell function in the prolonged hyperglycemia. Knockdown of BIP in β-cell can induce apoptosis. However, little is known about its function during embryonic development. / In high vertebrate, three sets of nephric forms develop successively during embryonic kidney development. They are pronephros, mesonephros, and metanephros. Nephron is the basic structural and functional unit of all these three forms. In amphibian, the pronephros performs function at the embryonic stages, which has only one nephron on either side of the body. It makes Xenopus a very good model for pronephros study. / In this study, we took advantage of Xenopus leavis as an animal model to investigate Bip function during embryonic development, especially its role in pronephros development. We first examined the expression of Bip in developing embryos. Whole mount in situ hybridization showed that Bip was expressed in the cement gland, pronephros, liver and ear vesicle during tailbud stages. It was expressed in the pronephros strongly and clearly which suggested that Bip might play roles in pronephros development. We performed loss-of-function experiment by using morpholino oligonucleotide (MO) knock down translation of endogenous Bip expression. Depletion of Bip impaired formation of pronephros revealed by reduction expression of different pronephros maker genes. The pluripotent animal caps can differentiate into pronephros tissue when treated with activin and all-trans retinoic acid (atRA) in vitro kidney induction assay. In line with our in vivo observation, knockdown of Bip inhibited pronephros differentiation that can normally achieved by combined effects of activin and atRA in animal cap assay. / In order to investigate the molecular mechanisms as how Bip regulated pronephros development, we performed Affymetrix DNA microarray assay to generate gene expression profile in Bip morphants. We found that some components of RA signaling were inhibited when Bip was knockdown. Moreover, knockdown of Bip caused reduction of RA target genes expression after treatment with RA. Consistent with above observations, luciferase activities of RA signaling reporter was reduced in HEK293T cells when BIP expression was depleted by RNAi. lhx1 is one of RA target genes and has been implicated playing essential roles in pronephros development. The inhibition of pronephros formation induced by Bip depletion can be partially rescued by co-overpression, suggesting 1) lhx1 is downstream of Bip in the regulatory network of pronephros formation; and 2) Bip regulates pronephros formation through RA signaling via lhx1. We also found increased apoptosis and decreased cell proliferation at pronephros-forming region in Bip morphants. That could explain the reason of pronephros malformation when Bip is downregulated. / Taken together, Bip is essential for pronephros development. It functions through RA signaling during the complex developmental processes. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Shi, Weili. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 125-143). / Abstracts also in Chinese.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 130-141.