Stem Cells in the Gastrointestinal Tract

Direkze, Nicholas A. Wright, and Mairi Brittan Turnover of the epithelial cell lineages within the gastrointestinal tract is a constant process, occurring every two to seven days under normal homeostasis and increasing after damage. This process is regulated by multipotent stem cells, which generate all gastrointestinal epithelial cell lineages and can regenerate whole intestinal crypts and gastric glands. The stem cells of the gastrointestinal tract are as yet...

Pancreatic Stem Cells

From a clinical perspective, the pancreas is an important focus of stem cell research because it is an attractive target for cell replacement therapy. In type I diabetes, the insulin-producing b-cells that reside in the pancreatic islets of Langerhans are destroyed by autoimmune attack, and it is thought that self-renewing stem cells could provide an unlimited source of b-cells for transplantation. Such therapeutic efforts require the prospective isolation of stem cells, with the potential to...

Polycomb And Trithorax Groups

Polycomb Group (Pc-G) Silencing Genetic screens in Drosophila have identified many Poly-comb group (Pc-G) genes required for the proper expression of homeotic genes (Simon and Tamkun, 2002). Whereas gap and pair-rule gene products are required to establish homeotic gene expression, Pc-G factors are required for maintenance. Not unexpectedly, these distinct classes of regulatory factors act in concert. Gap and pair-rule genes encode DNA binding factors that bind to enhancers and promoters of...

Barretts Metaplasia

Barrett's metaplasia (or Barrett's esophagus, as it is sometimes called) is the clinical situation in which intestinal cells are found in the tissue of the lower end of the esophagus. In the strictest terms, it is the conversion of stratified squamous epithelium to columnar epithelium and is characterized by the presence in biopsy material of acid mucin-containing goblet cells. The importance of Barrett's metaplasia stems from the rise in apparent incidence of the disease and its risk associ...

Evolving Concepts of Regeneration

The limited restorative capacity of the adult mammalian heart has been attributed to the loss of cardiomyocyte versatility soon after birth. Emerging concepts of regeneration as an evolutionary variable are dramatically illustrated by the relatively robust proliferative capacity of the injured heart in other vertebrate species. The dramatic regeneration of urodele amphibian limb and lens extends to their robust repair of injured myocardium. Unlike their mammalian counterparts, adult newt...

Fgf2 And Knockout Serum Replacer

Amit et al. 2000 examined the use of different media to increase the cloning efficiency of HESC. This study describes conditions allowing the use of a serum-free medium for the propagation of HESC. Basal medium 80 DMEM no pyruvate, high glucose formulation , 1 mM glutamine, 0.1 mM b-mercaptoethanol, and 1 nonessential amino acids was supplemented with either 20 fetal calf serum or 20 Knockout Serum Replacer, with or without 4ng ml FGF-2. Knockout Serum Replacer is a proprietary serum...

B

Differentiating keratinocytes basal kpratinorytes Figure 5-3. A Schematic of the components of a hair follicle modifiec from Watt, 2001 . The follicular bulge asterisk has been proposed to act as a stem cell niche, which houses cells that can contribute to all the differentiated cell types involved in the formation of the hair follicle, including the outer root sheath, inner root sheath, and hair shaft. Stem cells within the bulge can also generate sebocytes and the cells that maintain the...

The Human Embryo

Trophoblast Stem Cells Pseudostratified

Human development during implantation and gastrulation is significantly different from that of the mouse. Briefly, the Figure 12-6. Tissue formation and movements during the gastrulation of the mouse embryo E6.5-E7.5 . Gastrulation begins with the formation of the primitive streak ps in the posterior side of the E6.5 embryo at the junction of the extraembryonic ectoderm ex and epiblast e A . As more cells ingress through the streak, it elongates toward the distal tip of the embryo, between...

Germline Stem Cell Niche In The Drosophila Ovary

Drosophila Germarium

The adult Drosophila ovary consists of approximately 15 ovarioles, each with a specialized structure, the germarium, at the most anterior tip Figure 5-1A . Two to three GSCs lie at the anterior tip of the germarium, close to several groups of differentiated somatic cell types, including the terminal filament, cap cells, and inner germarial sheath cells Figure 5-1A, Figure 5-1B . When a female GSC divides, the daughter cell that lies closer to the terminal filament and cap cells retains stem...