Styelid ascidians are diverse in developmental modes, varying from strictly sexual solitary species to highly integrated colonies. Circulatory stem cells (CSCs) accomplish fundamental roles in developmental processes of styelid ascidians. In the colonial styelids, CSCs enable budding and are capable of giving origin to the germline in certain species. The function of these cells have been tested experimentally in models within Styelidae. However, the understanding of coloniality as an evolutionary novelty requires reconstructing the possible ancestral CSCs characteristics in Styelidae. To address this issue, this work analyzes the possible developmental origin and the identity of putative CSCs among blood cell populations. The first chapter of this dissertation aimed to characterize and compare the hemocyte populations in two solitary styelids: Styela plicata and Styela canopus. In addition, the early development, the metamorphosis and the early maturation were compared in both species. After metamorphosis, S. canopus briefly develops a network of extracorporeal vessels with numerous terminal ampullae. These characters are usually associated to colonial ascidians, and were not found in S. plicata. With respect to the hemocyte populations, similar morphotypes were present in both species. However, S. canopus shows a lower frequency of vacuolated cells, which may be due to a reduced level of cytotoxicity in the tunic relative to S. plicata. These differences observed between S. canopus and S. plicata may be related to differences in the degrees of gregariousness or body size among the two species. In order to investigate possible approaches to distinguish and isolate CSC populations in a solitary styelid model, I used imaging flow cytometry. Putative CSCs were identified through measurement of morphological parameters and aldehyde dehydrogenase (ALDH) activity. The correlation between these parameters allowed to determine 2 gates enriched with particular cell types. A significant difference was found on the ALDH+ population within a gate of cells with low granularity, suggesting the presence of cells among circulatory hemocytes. To scrutinize the biogenesis of CSCs in S. plicata, I present a description of a candidate hematopoietic niche in this species. An exhaustive histological survey for hemoblast-like cells was performed, and complemented with immunohistochemistry with stem cell (piwi) and proliferation (pHH3) markers. The morphological and expression profiles of the intestine support the intestinal submucosa (IS) as a hematopoietic niche. At this region there are aggregations of cells with and undifferentiated morphological profile, corroborated by ultrastructural analysis. Furthermore, the IS holds high cellular proliferation and frequency of piwi+ cells. Ascidians are considered interesting models to investigate asexual reproduction and modular development. This study represents an advancement towards understanding the processes, cell populations and structures that may be related to facilitating the appearance of this evolutionary novelty / As ascídias da família Styelidae são diversas em modos de desenvolvimento, variando de espécies estritamente sexuais solitárias até colônias altamente integradas. As células-tronco circulatórias (CTCs) desempenham papéis fundamentais nos processos do desenvolvimento de ascídias styelídeas. Nas especies coloniais deste grupo, as CTCs permitem a brotação e são capazes de originar a linha germinativa em certas espécies. A função dessas células tem sido testada experimentalmente em modelos dentro de Styelidae. No entanto, a compreensão da colonialidade como uma novidade evolutiva requer reconstruir as características das possíveis CTCs ancestrais para Styelidae. Com o fim de abordar essa questão, este trabalho analisa a possível origem do desenvolvimento e a identidade de CSCs putativas entre populações de células sanguíneas de styelídeas solitárias. O primeiro capítulo desta dissertação teve como objetivo caracterizar e comparar as populações de hemócitos em dois espécies solitárias: Styela plicata e Styela canopos. Além disso, o desenvolvimento inicial, a metamorfose e a maturação do juvenil foram comparados em ambas as espécies. Após a metamorfose, S. canopus desenvolve brevemente uma rede de vasos extracorpóreos com numerosas ampolas terminais. Esses caracteres são geralmente associados a ascídias coloniais e não foram encontrados em S. plicata. Com relação às populações de hemócitos, morfotipos semelhantes estavam presentes em ambas as espécies. No entanto, o S. canopos apresenta menor frequência de células vacuoladas, o que pode ser devido a um nível reduzido de citotoxicidade na túnica em relação a S. plicata. Essas diferenças observadas entre S. canopos e S. plicata podem estar relacionadas a diferenças nos graus de gregariedade ou tamanho corporal entre as duas espécies. A fim de investigar possíveis abordagens para distinguir e isolar populações de CTCs em um modelo de styelídeo solitário, usei citometria de fluxo com adquisição de imagem. As CTCs putativas foram identificadas através da medição de parâmetros morfológicos e da atividade da aldeído desidrogenase (ALDH). A correlação entre estes parâmetros permitiu determinar 2 gates enriquecidos com tipos celuláres particulares. Uma diferença significativa foi encontrada na população ALDH+ dentro de um gate de células com baixa granularidade, sugerindo a presença de células-tronco circulatórias. Para examinar a biogênese das CTCs em S. plicata, foi realizada uma descrição de um nicho hematopoiético candidato nesta espécie. Um exame histológico exaustivo para células semelhantes a hemoblastos foi realizado e complementado com imunohistoquímica com marcadores de células-tronco (piwi) e proliferação (pHH3). Os perfis morfológicos e de expressão do intestino sustentam a submucosa intestinal (SI) como nicho hematopoiético. Nesta região há agregações de células com morfolia indiferenciada, corroborada pela análise ultraestrutural. Além disso, a SI mantém alta proliferação celular e freqüência de células piwi+. As ascídias são consideradas modelos interessantes para investigar a reprodução assexuada e o desenvolvimento modular. Este estudo representa um avanço na compreensão dos processos, populações celulares e estruturas que podem estar relacionadas a facilitar o surgimento desta novidade evolutiva

<p>Forty barrows were used in a 35d experiment to evaluate the effects of supplemental soluble fiber (dextrin) pre- and post-weaning on growth performance, intestinal microbiome, volatile fatty acid (VFA) production, intestinal morphology, and gene expression. Pigs were blocked by litter and BW, and randomly allotted to treatments in a 2x2 factorial design with or without fiber pre-weaning and with or without fiber post-weaning. Dextrin was administered orally through a syringe, after being suspended in chocolate milk from 14d prior to weaning through 3d post-weaning, after which it was included in the diet at 1%. At weaning, pigs were group housed by treatment and allowed ad libitum access to a common starter diet. On d4 post-weaning, pigs were moved to individual pens and fed diets with or without 1% fiber. Weights and feed intake were recorded 14 and 3d prior to weaning, and on d0, 4, 11, and 21 post-weaning. On d0 and d21 post-weaning, pigs were euthanized for collection of tissues and intestinal contents. Ileal, cecal, and colon contents were taken for microbiome analysis, distal large intestine contents were collected for VFA analysis, ileal cross sections were collected for histology, and ileal and cecal mucosal scrapings were collected for intestinal gene expression. Data were analyzed using the GLM procedure of SAS with pig as the experimental unit for growth performance, VFA production, intestinal morphology, and gene expression. Microbiome data were analyzed using Metastats, to find statistical significance between treatments, and then run through R, using the false discovery rate method, to find a multiple test corrections q-value. Growth performance in general was not affected (<i>P</i>> 0.10) by treatment with the exception of d11-21 feed efficiency was improved (<i>P</i>= 0.018) for pigs receiving supplemental fiber prior to weaning. Pigs that received fiber at any point had increased short chain fatty acid (SCFA) producing bacteria (<i>q </i>< 0.05) compared to pigs never receiving fiber. Pigs never receiving fiber had increased bacteria associated with intestinal inflammation (<i>q </i>< 0.05) compared to all other treatment groups. A trend for an interaction (<i>P </i>= 0.054) of pre- and post-weaning fiber supplementation<b></b>was observed for total volatile fatty acid concentration in large intestine contents. An interaction (<i>P </i>= 0.007) of pre- and post-weaning treatments was observed on butyrate, with pigs fed fiber only during pre-weaning having the greatest butyrate concentrations. Pigs fed fiber pre-weaning had decreased isobutyrate concentrations (<i>P </i>= 0.050) and percentages (<i>P</i>=0.040) and a trend for decreased isovalerate as a concentration (<i>P</i>= 0.058) and percent of total VFAs (<i>P </i>= 0.051). Pigs fed fiber post-weaning had increased acetate (<i>P </i>= 0.047). An interaction for butyrate percentages was observed with pigs receiving supplemental fiber only prior to weaning having the highest percent of butyrate (<i>P</i>= 0.029). An interaction for valerate concentrations (<i>P </i>= 0.045) occurred with pigs receiving fiber only prior to weaning having the highest amount of valerate. Valerate as a proportion of total VFAs (<i>P </i>= 0.038) was decreased in pigs receiving supplemental fiber post-weaning. Pigs fed fiber prior to weaning tended to have decreased crypt depths (<i>P </i>= 0.097) compared to pigs that did not receive fiber prior to weaning. In the ileum there was an interaction (<i>P </i>= 0.002) for GLP-2 expression, with pigs receiving supplemental fiber solely before or after weaning having the greatest expression. Occludin expression in the ileum tended to increase with fiber supplementation prior to weaning (<i>P</i>= 0.086) but then tended to decrease with fiber supplementation post-weaning (<i>P</i>= 0.053) In the cecum, there was an interaction (<i>P </i>= 0.049) of pre- and post-weaning fiber supplementation<b></b>on GLP-2 expression. Pigs fed supplemental fiber at any point had increased GLP-2 expression, but pigs that had fiber only after weaning had the greatest GLP-2 expression. Cecal HSP-70 expression also increased with fiber supplementation in pigs fed fiber post-weaning (<i>P </i>= 0.012). Soluble fiber supplementation caused alterations in the intestinal microbiome, VFA concentrations, the intestinal morphology, and in the expression of different intestinal genes.</p>

Contains errata sheet in back pocket. / Bibliography: leaves 167-211. / xviii, 211, [8] leaves, [4] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Explores the hypothesis that growth of the small intestine at weaning is promoted by an activated mucosal immune system in the gut. Tests by observing rats, guinea pigs and human infants. / Thesis (Ph.D.)--University of Adelaide, Dept. of Medicine, 1995?

The products of the Cdx genes, Cdx1, Cdx2 and Cdx4, are known to play essential roles in many developmental processes including neural tube closure, axial elongation and patterning the anterior-posterior axis of the developing embryo. Cdx1 and Cdx2 are both expressed in the endoderm of the embryo and persist throughout adulthood in the intestinal epithelium, but their functions and mechanisms of action in this lineage are poorly understood, in part due to the peri-implantation lethality of Cdx2-/- mice. To circumvent this limitation, a conditional loss of function strategy was used to inactivate Cdx2 in the intestinal epithelium. These conditional mutants were also crossed to Cdx1-/- mice, which are viable and fertile, to examine potential functional compensation between these family members. The major findings of this study are that Cdx2 regulates patterning and differentiation of the small intestinal epithelium, while Cdx1 does not appear to make a contribution to either process. Furthermore, Cdx operates upstream of Notch ligand Delta-like 1 (Dll1) in endoderm and mesoderm derivatives, demonstrating that Cdx function is similar in different lineages. Finally, Cdx2 cannot fulfill the requirement for Cdx1 in regulation of its own promoter in the intestine. This is the first in vivo evidence that these two family members have context-dependent functional specificity. Altogether, this study underscores critical roles and mechanisms of action for Cdx members in the developing intestine and mesoderm.

Graduation date: 1994

¡iAbstract¡j Lipopolysaccharide (LPS) is the toxic chemical component of the cell wall in all gram-negative bacteria which can stimulate immune cells, including macrophages and white blood cell, to release cytokines such as interleukin-1£], interleukin-6 and tumor necrosis factor-£\. These pro-inflammatory mediators induce systemic acute inflammation and multiple organs dysfuction syndrome in sepsis. Plasma leakage from microvasculature is a hallmark of inflammation. Previous studies have demonstrated that other inflammatory agents, such as capsaicin, substance P and histamine could cause the acute formation of numerous endothelial gaps in the venules that result in extensive plasma leakage in the inflammatory tissues of the whole respiratory tract and a part of digestive tract in a few minutes. Mammalian intestines have many goblet cells that synthesize mucus and discharge it into the intestinal lumen. The mucus film that covers the surface epithelium facing the lumen of digestive system, is an immune defense that can prevent gastrointestinal epithelium from chemical and physical damage and act as a lubricant. Changes in goblet cell function and number are involved in microbial infection, inflammatory syndromes and immune factors. This study was aimed to investigate: (1) The degree of Plasma leakage and goblet cell hypersecretion in the small intestine of rats after an intravenous injection of a high dose of LPS (15 mg/kg), and (2) The involvement of vagus nerve and cholinergic receptors in plasma leakage and goblet cell secretion. For the study of plasma extravasation in small intestine during endotoxema, India ink was used as the tracer to mark the inflamed leaky microvessels. Rats were perfusion-fixed through the aorta, and endothelial gaps between endothelial cells of blood vessels were made visible with silver staining. The methacrylate sections of the ileum 3 £gm in thickness were stained with Alcian blue and periodic acid-schiff reagent to detect glycoproteins of goblet cells. Our results showed that LPS not only caused an increase in plasma leakage but also triggered degranulation of many goblet cells in villi and crypts. Numerous gaps were found in postcapillary venules and collecting venules, and plasma extravasation was observed in the serosa and tunica muscularis rat small intestine after LPS. Extensive plasma extravasation occurred in earier phases (5-30 min). However, numerous goblet cells started to discharge mucus granules 30 min after LPS treatment. A large amount of extracellular mucus was accumulated between intestinal villi 1 hour after LPS stimulation. Pretreatment with atropine, the muscarinic receptor antagonist, significantly inhibited goblet cell secretion. The inhibitory effect of pretreatment with atropine or bilateral cervical vagotomy on LPS-induced plasma leakage was not consistent. It is concluded that the plasma leakage and goblet cell hypersecretion induced by endotoxin shock was time-dependent and was associated with activation of muscarinic cholinergic receptors.

Thesis (M. Sc.)--York University, 2000. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 111-119). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ59179.

Rat exon microarrays were utilized to detect changes in mRNA expression and alternative splicing in the liver, duodenum, jejunum, and ileum of the lactating rat when compared to age-matched virgin controls. Analysis of data at the level of gene expression revealed differential expression of genes involved in cholesterol biosynthesis in each tissue examined, suggesting increased Sterol Response Element Binding Protein activity. We also detected decreased mRNA from components of the T-cell signaling pathway in the jejunum and ileum. We characterized expression of solute carrier and adenosine triphosphate binding cassette proteins. In addition to characterizing genes by pathway, we have also grouped genes based on their pattern of expression to identify important genes. Amongst genes upregulated in all tissues was Slc39a4, which is a critical transporter in the absorption of zinc in enterocytes. Alternative splicing analysis detected a substantial amount of alternative splicing in the ileum compared to other tissues. In addition, in the liver Abcg8, a protein that functions as a heterodimer to export cholesterol in the bile, shows differential splicing in the liver, but not in other tissues. We also detected differential expression of Ugt1a6 in the liver based on usage of an alternative first exon, which is consistent with altered protein levels observed previously. Differential splicing also appears to occur in Ace2 in the ileum, which could have consequences on the renin-angiotensin pathway.

The effect of intestinal microbiota and dietary supplementation of mannan oligosaccharides (MOS) on mucosal architecture and digestive physiology in broiler chicks was examined. In experiment 1, pre-sterilized eggs (Ross x Ross 308) were placed in three HEPA (high efficiency particulate air)-filtered isolator units at day 19 of incubation. Germ-free chicks in one isolator were conventionalized by exposure to cecal contents from a laying hen. Bacterial contamination occurred in one germ-free isolator such that these birds were monoassociated by a bacterium within the Acinetobacter spp. resulting in 3 categories of microbial status including germ-free (GF, n=10), conventionalized (CV, n=19) and monoassociated (Mono, n=13) birds. Dietary treatments assigned to each isolator consisted of a negative control (NC, 0 g/kg of MOS in the basal diet) and MOS (2 g/kg of MOS in the diet) resulting in a 2X3 factorial treatment arrangement. At 7 d of age, body weight was recorded and birds were killed to permit collection of visceral organs, intestinal tissues and cecal contents. Body weight, relative length of small intestinal segments and relative bursa weight were significantly increased in CV birds. These birds also had increased crypt depth and lamina propria area. Dietary MOS increased villus height and villus surface area in CV birds compared with GF and Mono birds. Transcripts for all housekeeping genes tested in ileal tissue were increased by MOS such that transcripts were normalized to unit mass of total RNA. In comparison to birds fed the NC diet, MOS significantly increased the abundance of proliferative cell nuclear antigen (PCNA), toll-like receptor (TLR)-4, avian β-defensin (GAL)-6, interleukin (IL)-8, peptide transporter 1 (PepT1) and sodium-dependent glucose transporter (SGLT)-1 transcripts in ileum per unit total RNA. However, the effect of microbial status on selected gene expression profiles was surprisingly limited. A second experiment was conducted to confirm the conventionalization protocol produced a complex microbiota similar to conventionally reared birds. Twenty day-old broiler chicks (Ross x Ross 308) were assigned to one of two wire-floored battery cages provided the NC and MOS diets ad libitum and killed at 7 d of age. Terminal restriction fragment length polymorphism (TRFLP) analysis demonstrated that microbial diversity indices (Richness, Evenness, Shannon, and Simpson) were greater in conventionalized gnotobiotic birds compared to the conventionally reared birds confirming a successful conventionalization strategy in the gnotobiotic trial. These studies demonstrate that under good hygienic conditions, CV chicks thrive similar to GF animals. Based on responses to MOS observed in GF birds, evidence indicates that MOS, independent of changes in microbial composition, directly modifies host response parameters including innate immune activation, digestive and absorptive function.

The products of the Cdx genes, Cdx1, Cdx2 and Cdx4, are known to play essential roles in many developmental processes including neural tube closure, axial elongation and patterning the anterior-posterior axis of the developing embryo. Cdx1 and Cdx2 are both expressed in the endoderm of the embryo and persist throughout adulthood in the intestinal epithelium, but their functions and mechanisms of action in this lineage are poorly understood, in part due to the peri-implantation lethality of Cdx2-/- mice. To circumvent this limitation, a conditional loss of function strategy was used to inactivate Cdx2 in the intestinal epithelium. These conditional mutants were also crossed to Cdx1-/- mice, which are viable and fertile, to examine potential functional compensation between these family members. The major findings of this study are that Cdx2 regulates patterning and differentiation of the small intestinal epithelium, while Cdx1 does not appear to make a contribution to either process. Furthermore, Cdx operates upstream of Notch ligand Delta-like 1 (Dll1) in endoderm and mesoderm derivatives, demonstrating that Cdx function is similar in different lineages. Finally, Cdx2 cannot fulfill the requirement for Cdx1 in regulation of its own promoter in the intestine. This is the first in vivo evidence that these two family members have context-dependent functional specificity. Altogether, this study underscores critical roles and mechanisms of action for Cdx members in the developing intestine and mesoderm.