Many cells employ cadherin complexes (c-sites) on the cell membrane to attach to neighboring cells, as well as integrin complexes (i-sites) to attach to a substrate in order to accomplish cell migration. This paper analyzes a model for the motion of a group of cells connected by c-sites. We begin with two cells connected by a single c-site and analyze the resultant motion of the system. We find that the system is irrotational. We present a result for reducing the number of c-sites in a system with c-sites between pairs of cells. This greatly simplifies the general system, and provides an exact solution for the motion of a system of two cells and several c-sites.Then a method for analyzing the general cell system is presented. This method involves 0-row-sum, symmetric matrices. A few results are presented as well as conjectures made that we feel will greatly simplify such analyses. The thesis concludes with the proposal of a framework for analyzing a dynamic cell system in which stochastic processes govern the attachment and detachment of c-sites.

Diss. (sammanfattning) Linköping : Univ., 2001. / Härtill 4 uppsatser.

Ao longo do processo de progressão tumoral, se observa alteração na expressão de glicoconjugados contendo oligossacarídeos N-ligados. Uma das formas mais comuns de glicosilação aberrante observada em células transformadas e em tumores humanos é representada por (poli)lactosaminas presentes em oligossacarídeos N-ligados. Estes glicanos são ligantes de galectina-3. Com o objetivo de identificar a expressão e distribuição dos ligantes de galectina-3 associados a processos fisiopatológicos, como a transformação maligna, desenvolvemos uma proteína quimérica, a galectina-3 conjugada a fosfatase alcalina (Gal-3/FA). Observamos que a Gal-3/FA possui a mesma especificidade de galectina-3 e que pode ser usada como sonda em ensaios de overlay e ensaios de imunoistoquímica. Entre os ligantes de galectina-3 identificamos a ?1 integrina, mediador de processos biológicos dependentes da interação célula-matriz como a migração celular. Linhagens de células de origem mesenquimal derivadas de tumores induzidos com metilcolantreno de animais selvagens (linhagens S11 e S12) e nulizigoto (linhagem ?12) para o gene da galectina-3 foram estabelecidas. Avaliamos a capacidade migratória dessas células e os nossos resultados mostraram que células que expressam galectina-3 são mais migratórias em superfícies de laminina-1. Este dado sugere que a galectina-3 seja um modulador positivo do processo de migração celular em superfícies de laminina-1. No entanto, o mecanismo pelo qual a galectina-3 medeia esse processo não é conhecido. Células que possuem fenótipo mais migratório apresentam um estado intermediário de adesão. Nós observamos que a galectina-3 se encontra nos complexos focais. Na presença de galectina-3 observamos diminuição de FAK fosforilado e recrutamento da fosfatase SHP-2 para os complexos focais. A diminuição de FAK fosforilado no lamelipódio leva ao turnover dos complexos focais e ao aumento da migração celular. Analisamos também a via de sinalização e observamos que a galectina-3 não ativa PAK. Contudo, o inibidor de PI3quinase, wortmanina, inibiu o efeito pró-migratório de galectina-3. Esses dados reforçam a noção do papel de galectina-3 na modulação do processo de migração de fibroblastos transformados, funcionando como uma molécula / Altered expression of cell surface N-linked oligosaccharides are often associated with malignant transformation of cells. One of the most common forms of aberrant glycosylation in transformed cells and human tumors is the highly elevated ?1,6 branching of N-linked oligosaccharides caused by increased expression of N-acetylglucosaminytransferase V (Mgat5). Galectin-3, a ?-galactoside binding protein, binds preferentially to poly-N-acetyllactosamines, which are the products of Mgat5. In order to exploit this hallmark of cancer cells, we have developed a tool for in situ identification of these tumors associated glycoconjugates. Human galectin-3 was fused to bacterial alkaline phosphatase, generating a hybrid molecule displaying both the carbohydrate binding properties of galectin-3 and enzymatic activity of alkaline phosphatase (Gal-3/FA). Gal-3/FA has the same fine of galectin-3 which was confirmed in direct binding assays. The tool presented herein was therefore useful for several immunoenzymatic assays, and will allow to establish whether the expression pattern of galectin-3 ligands have any physiological or clinical significance. We have identified ?1 integrin as a galectin-3 ligand. ?1 integrins are the actual effector of cell adhesion and migration. We have established cell lines from methylcholantrene-induced sarcomas from both wild type and galectin-3 null mice. In this system, galectin-3 null cells were less migratory than control cells in laminin-1. When galectin-3 was transiently expressed in galectin-3 null sarcoma cells, it inhibited cell adhesion to laminin-1 and stimulate the migratory response to laminin-1. The addition of exogenous galectin-3 also enhanced the migratory capacity of ?12 cells in a carbohydrate dependent way. Galectin-3 was found in focal contacts of ?12 cells where it may interact with many glycoproteins containing polyllactosamines on the cell surface. Here we showed that ?1 integrins are among them. Exogenously added galectin-3 led to a decrease in phosphorylated-FAK in lamellipodia and increased the recruitment of Shp-2 phosphatase of migrating cells. The effect of galectin-3 in migration was not dependent on the activation of the p21-activated kinase (PAK). Wortmannin inhibited the increased migration elicited by galectin-3, suggesting the involvement of the PI3-kinase signaling in the galectin-3 pathway. We propose that extracellular galectin-3 bound ?1integrins and disrupted the focal adhesion plaque, thus favoring cell migration.

Next, the influences on the migration of neural crest cell from the microenvironment of the hindgut through which the neural crest cells migrate were studied. An organ culture system was established to recombine different gut segments together at E11.5 for gut culture in order to trace the migration of neural crest cells from the midgut of the +/+ or Dom/+ embryo to the hindgut of the same or different genotypes. At E11.5, the midgut of both +/+ and Dom/+ embryos had already been fully colonized by neural crest cells, thus an explanted midgut segment (donor midgut) could serve as the source of the neural crest cells, while the caudal half of the hindgut (recipient hindgut) acted as the recipient of the neural crest cells from the donor midgut segment because at this stage, the caudal half of the hindgut was completely devoid of neural crest cells. After three days of culture, when a segment of midgut from the +/+ embryo was used as the donor of migratory vagal neural crest-derived cells and combined with an aneural segment of the hindgut (segment without neural crest-derived cells) from Dom/+ or Dom/Dom embryos, neural crest-derived cells from the midgut segment successfully crossed the combination junction and migrated normally along the hindgut segment to reach its caudal end within a normal developmental time frame. However, the migration of neural crest-derived donor cells from the Dom/+ midgut segment was abnormal in the recipient hindgut with a genotype of +/+, Dom/+ or Dom/Dom as evidenced by the retarded rostrocaudal progression of the vagal neural crest-derived cells and the reduced number of migratory cells in the recipient hindgut segment. These results thus indicate that the migration of the vagal neural crest-derived cells is minimally influenced by the migratory environment of the hindgut of the Dom embryo, and that the neural crest cells themselves may be defective in migration leading to the retarded migration in the hindgut of Dom mouse embryos. / The vagal neural crest cells originating from the region of the neural tube adjacent to somites 1 to 7 migrate along defined pathways to the gastrointestinal tract and then colonize the gut to give rise to the majority of neurons and glia of the enteric nervous system. Mutation of Sox10 in the Dominant megacolon (Dom) mouse, which is an animal model of Hirschsprung's disease, leads to aganglionosis (absence of ganglia) in varying lengths of the hindgut. To investigate the underlying cellular mechanism of aganglionosis, the migration of vagal neural crest cells from the neural tube to the gut (pre-enteric migration) in Dom mouse embryos at E8.5 was firstly traced with extrinsic cell markers, such as wheat germ agglutinin gold conjugates (WGA-Au) or fluorescent dye DiI. After the vagal neural crest cells entered the gut at E9.5, their migration was then followed by the examination of the expression of specific markers for undifferentiated neural crest cells with immunohistochemical staining. It was found that, although vagal neural crest cells in embryos of the three genotypes examined migrated along similar pre-enteric pathways at a similar migratory rate, the numbers of neural crest cells in embryos heterozygous (Dom/+) and homozygous (Dom/Dom) for the Sox10 mutation were significantly reduced when compared with the number of neural crest cells in wild-type (+/+) embryos. After vagal neural crest had entered the gut and from E10.5 onwards, no neural crest-derived cells were found in the gut of Dom/Dom embryos, and the migration of neural crest cells along the Dom/+ gut was significantly retarded from E12.5 onwards as compared with the migration in stage-matched +/+ embryos. / To further trace the cause of defective migration of neural crest cells in the Dom embryo, the proliferation and survival of neural crest cells were investigated with BrdU labeling and TUNEL assay. It was found that, although there was no obvious difference in the proliferating ability of vagal neural crest cells in embryos of all the three Dom genotypes studied during the pre-enteric migration and the migration in the gut, more apoptotic neural crest cells were found along the pre-enteric migratory pathway of Dom/Dom embryos than Dom/+ and +/+ embryos. Therefore, the decreased surviving ability, but possibly not the reduced proliferating ability, of neural crest cells during their pre-enteric migration may be partly responsible for aganglionosis in the hindgut of the Dom mouse. / Wang Liang. / "June 2006." / Adviser: W. Y. Chan. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1380. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 287-307). / 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, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Cheung Chui Shan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 96-107 (2nd gp.)). / Abstracts in English and Chinese. / ABSTRACT (ENGLISH) --- p.i / ABSTRACT (CHINESE) --- p.iii / ACKNOWLEDGEMENTS --- p.v / TABLE OF CONTENT --- p.vii / Chapter CHAPTER ONE --- GENERAL INTRODUCTION / Chapter 1.1 --- Early development of the central nervous system --- p.1 / Chapter 1.2 --- Neural crest cells and Cardiac neural crest cells --- p.1 / Chapter 1.3 --- Role of neural crest cells in cardiovascular development --- p.4 / Chapter 1.4 --- Methods in tracing neural crest cells --- p.7 / Chapter 1.5 --- Neural crest-related defects --- p.14 / Chapter 1.6 --- Animal models for studying neural crest defects --- p.16 / Chapter 1.7 --- Recent studies on the migration of cardiac neural crest cells in mammals --- p.19 / Chapter 1.8 --- Objectives of the present study --- p.22 / Chapter CHAPTER TWO --- MATERIALS AND METHODS / Chapter 2.1 --- Materials --- p.26 / Pregnant mice --- p.26 / Pregnant Splotch mice (Sp2H) --- p.26 / Preparation of the handling medium --- p.27 / Preparation of the culture medium --- p.27 / Gas mixtures for embryo culture --- p.30 / Preparation of wheat germ agglutinin-gold conjugates (WGA-Au) --- p.30 / Preparation of the fixative --- p.30 / DNA solution for genotyping of Splotch embryos --- p.31 / Primers used in PCR for genotyping of Splotch embryos --- p.31 / PCR reagent system --- p.32 / 10XTBE --- p.32 / Chapter 2.2 --- Methods --- p.33 / Isolation of embryos from pregnant mice --- p.33 / In situ labelling of exogenous dye --- p.34 / Orthotopical grafting of neural crest fragment --- p.36 / Whole embryo culture --- p.37 / Morphological examination of cultured embryos --- p.38 / Histological examination of cultured embryos --- p.38 / Examination of labelled cells in sectioned embryos --- p.39 / Genotyping of Splotch embryos by PCR --- p.40 / Gel electrophoresis --- p.41 / Chapter CHAPTER THREE --- RESULTS / Chapter 3. 1 --- Initial migration of cardiac neural crest cells in normal ICR mouse embryos --- p.43 / Gross morphological examination of cultured embryos --- p.43 / Distribution of WGA-Au labelled cells in ICR normal mouse embryos --- p.45 / Chapter 3.2 --- Initial migration of cardiac neural crest cells in Splotch embryos --- p.50 / Genotyping --- p.50 / Morphological examination of Splotch mutant embryos --- p.50 / Morphological examination of in vivo Splotch embryos --- p.53 / Distribution of WGA-Au labelled cells in Splotch Embryos --- p.54 / Chapter 3.3 --- Transplantation of neural crest fragments in Splotch embryos --- p.60 / Morphological features of Splotch embryos after orthotopic grafting --- p.60 / Histological examination of Splotch embryos after grafting --- p.61 / Distribution of WGA-Au labelled cells in Splotch embryos after grafting --- p.62 / Chapter CHPATER FOUR --- DISCUSSION / Chapter 4.1 --- Development of embryos in vitro --- p.65 / Chapter 4.2 --- Methodology --- p.70 / In situ labelling of WGA-Au in embryos --- p.70 / Counting of labelled cells in Sploch embryos --- p.72 / Transplantation of neural crest fragments --- p.72 / Chapter 4.3 --- Initial migration of cardiac neural crest cells --- p.74 / Distribution of cardiac neural crest cellsin normal mouse embryos --- p.74 / Differences in the distribution of labelled neural crest cells In different genotypes of Splotch embryos --- p.78 / Distribution of cardiac neural crest cells in Splotch embryos After transplanting of neural crest fragments --- p.83 / Chapter 4.4 --- Factors in extracellular matrix affecting the migration of neural crest cells --- p.88 / Chapter CHAPTER FIVE --- CONCLUSION --- p.91 / REFERENCES --- p.96 / FIGURES AND LEGEND / TABLES / GRAPHS

Tomato bushy stunt virus (TBSV) provides a good model system to investigate molecular virus-host interactions in plants. P22 and P19 proteins encoded by TBSV contribute to multiple invasion-associated functions. Green fluorescence-mediated visualization of TBSV invasion in this study suggests that virus exit from inoculated epidermal cells is a crucial event. Close examination of one P22 mutant showed that it had lost the capacity to move between epidermis and mesophyll which was possibly due to an altered subcellular localization. P19 is a potent suppressor of RNA interference (RNAi) in various systems by forming dimers that bind 21-nucleotide (nt) duplex siRNAs (short interfering RNAs), to affect the programming of the RNA-induced silencing complex (RISC). P19 is attractive for biotechnological and research purposes to prevent RNAi of certain value-added genes in plants. To obtain a good plant-based expression platform, a suppression-active mutant P19 was expressed in transgenic N. benthamiana lines. This is the first example of P19 accumulating to detectable levels in a transgenic plant and initial results suggest it is actively suppressing RNAi. Furthermore, to investigate the correlation between siRNA binding of P19 and its various biological roles, predicted siRNA-interacting sites of TBSV P19 were modified, and the corresponding TBSV mutants were used to inoculate plants. Substitutions on siRNA-contact sites on the central domain of P19 resulted in more severe symptoms in N. benthamiana compared to those affecting peripheral regions. All tested combinations of siRNA-binding mutations were associated with reduced accumulation of total TBSV-derived siRNAs, and loss of siRNA sequestration by P19. Additionally, some modifications were found to cause RNAi-mediated disappearance of viral and host materials in N. benthamiana but not in spinach. In conclusion, exit out of epidermal cells is a key host range determinant for TBSV and particular amino acids on P22 may influence this by regulating the proper subcellular localization. Mutant P19 transgenic plants were successfully established with minor physiological effects to be applied as a platform to study RNAi and to over-express proteins. Finally, a compromised P19-siRNA binding impacts symptom development, systemic invasion, integrity of virus plus host RNA and proteins, and that all in a hostdependent manner.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 89-100).

Thesis--University of Oklahoma. / Includes bibliographical references (leaves 51-55).

Dissertation (Ph.D.)--University of South Florida, 2008. / Includes vita. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from first page of PDF file (viewed Oct. 31, 2007). Includes bibliographical references.