			Home About us Contact

Stem Cell Pool (stem + cell_pool)

Distribution by Scientific Domains

Life Sciences	60%
Medical Sciences	40%

Selected Abstracts

New model for the formation and function of sagittocysts: Symsagittifera corsicae n. sp. (Acoela)

INVERTEBRATE BIOLOGY, Issue 2 2002
Robert Gschwentner
Abstract. This study is focused on the formation and function of sagittocysts, which are secretions typical of members of the acoel family Sagittiferidae. The needle-shaped sagittocysts are produced in specialized gland cells (sagittocytes) whose distal necks are often surrounded by muscle mantles. Contraction of the muscle mantle ejects the sagittocyst. We establish a model for the development of sagittocytes and muscle mantles out of the stem cell pool of the new acoel species Symsagittifera corsicae. We used various techniques, especially interference and phase-contrast microscopy of living specimens as well as labeling of the body-wall musculature, for species characterization. In addition to the morphological features, we provide the third complete sequence of the 18S rDNA gene in the family Sagittiferidae. [source]

Dietary restriction enhances germline stem cell maintenance

AGING CELL, Issue 5 2010
William Mair
Summary Dietary restriction (DR) increases lifespan in species ranging from yeast to primates, maintaining tissues in a youthful state and delaying reproductive senescence. However, little is known about the mechanisms by which this occurs. Here we demonstrate that, concurrent with extending lifespan, DR attenuates the age-related decline in male germline stem cell (GSC) number in Drosophila. These data support a model whereby DR enhances maintenance of GSCs to extend the reproductive period of animals subjected to adverse nutritional conditions. This represents the first example of DR maintaining an adult stem cell pool and suggests a potential mechanism by which DR might delay aging in the tissues of higher organisms. [source]

Continuous occurrence of both insufficient neovascularization and elevated vascular permeability in rabbit proximal femur during inadequate repair of steroid-associated osteonecrotic lesions

ARTHRITIS & RHEUMATISM, Issue 10 2009
Ge Zhang
Objective To examine the features of the intraosseous vasculature, the size of the marrow stem cell pool (MSCP), and expression of vascular endothelial growth factor A (VEGF) during inadequate repair of steroid-associated osteonecrotic lesions in rabbits. Methods Steroid-associated osteonecrosis was induced in male rabbits. At 0, 1, 2, 4, and 6 weeks postinduction, vascularization and permeability indices were quantified by dynamic magnetic resonance imaging (MRI). In addition, the size of the MSCP in the hematopoietic and mesenchymal compartments was determined, and marrow mononuclear cells expressing specific surface markers for endothelial progenitor cells or periendothelial mural precursor cells were counted. At various time points after the rabbits were killed, the proximal femora were dissected to examine the intraosseous vasculature by angiography, histomorphometry, and ultramorphology. In addition, osteonecrotic lesion repair and marrow VEGF expression were evaluated. Results Lesion formation without repair was observed at 2 weeks after induction of steroid-associated osteonecrosis. Rabbits displaying destructive repair (DR+) and those displaying reparative osteogenesis (DR,) from 4 weeks to 6 weeks postinduction were identified. From week 2 to week 6, the vascularization index was significantly lower in DR+ rabbits compared with DR, rabbits, whereas the permeability index was significantly higher in DR+ rabbits compared with DR, rabbits. The features of the intraosseous vasculature determined by angiography, histomorphometry, and ultramorphology were consistent with those determined by dynamic MRI. The MSCP size and number of marrow mononuclear cells expressing specific surface markers were all significantly lower in DR+ rabbits than in DR, rabbits from week 1 to week 6. The increased VEGF expression at 2 weeks was maintained through week 6 in DR+ rabbits, whereas VEGF expression decreased in DR, rabbits from week 2 to week 6. Conclusion Continuous occurrence of both insufficient neovascularization and elevated vascular permeability is accompanied by a continuously low- level MSCP and uncontrolled VEGF expression during inadequate repair of steroid-associated osteonecrotic lesions. [source]

Controlling the stem cell niche: right time, right place, right strength

BIOESSAYS, Issue 1 2006
Catherin Niemann
Wnt signalling through ,-catenin plays a pivotal role during embryonic pattern formation, cell fate determination and tissue homeostasis in the adult organism. In the skin, as in many other tissues, Wnt/,-catenin signalling can control lineage determination and differentiation. However, it was not known whether Wnt/,-catenin signalling is an immediate regulator of the stem cell niche in skin tissue. A recent publication now provides evidence that Wnt/,-catenin signalling exerts a direct effect on the stem cell compartment by inducing quiescent stem cells to enter the cell cycle during early stages of hair follicle regeneration. In addition, the authors demonstrate that ,-catenin is required for maintenance of the stem cell pool in the tissue.1 The data suggest that a gradient in Wnt/,-catenin activity levels can induce different responses within distinct cell populations reflected by activation of distinct transcriptional profiles. BioEssays 28:1,5, 2006. © 2005 Wiley Periodicals, Inc. [source]

B-cell chronic lymphocytic leukaemia cells show specific changes in membrane protein expression during different stages of cell cycle

BRITISH JOURNAL OF HAEMATOLOGY, Issue 4 2007
Fiona Bennett
Summary The proliferating component in chronic lymphocytic leukaemia (CLL) is usually small (<1%) and restricted to a specific micro-environmental niche. To characterize the proliferating component, CLL cells from bone marrow or lymph nodes of 23 patients were assessed for expression of up to 66 surface antigens in combination with nuclear Ki-67/MCM6. Ki-67 expression was associated with step-wise increases in CD23/CD95/CD86/CD39/CD27 and decreases in CD24/CD69/CXCR4/CXCR5. Ki-67+ cells showed increased CD38 expression, but with considerable inter-patient variability: in some cases Ki-67 expression was only detectable in CD38, CLL cells. The results suggest continuous re-entry into the cell cycle as no distinct stem cell pool was detectable. [source]