Stem cell

Totipotent stem cells are obtained from embryos that are less than five days old. These cells have the full potential to develop into another individual and every cell type. 

Stem cells removed and grown in Petri dish 

Cell differentiation (e. g. muscle, nerve, islet cells) 

After about five days and several cycles of cell division, the totipotent cells form a hollow sphere of cells called a blastocyst. The blastocyst has an outer layer of cells surrounding clusters of cells. Those cells on the outside continue to divide and grow into the placenta and supporting tissues. The clusters of cells on the inside divide and form virtually all the cell types, except the placenta and supporting tissues, which give rise to a human being. These are the pluripotent stem cells, and they give rise to many different types of cells, but not a new individual. 

The hmnan body s entire system of a billion or more cells develops from a single cell—the egg fertilized by the sperm. As this cell divides to form all the different tissues and structures of the growing fetus, the daughter cells become specialized in the kinds of proteins they produce. Think of the entire set of genes as inherited instructions to form more than 100,000 proteins when and where they are needed. Going from the single-cell embryo to the enormous collection of specialized cells that make up our body is an 

Hui Peng, Nicholas Whitney, Kang Tang, Myron Toews, and Jialin Zheng 

Keywords Neurogenesis Stem cell Self-renewal Proliferation Differentiation Microglia Chemokines Growth factors N euro transmi tters 

Developments in both instrumentation and cell labeling have enabled a great expansion of their use in both clinical practice and research. 

New approaches, such as the use of peptides, proteins, antibodies, and molecular recognition unit technologies, may result in substantial improvements in the labeling methodology and could yield labeled cells with the least damage and high in vivo stability in the future. 

The authors gratefully acknowledge the collaboration and assistance by Judith Bednar, Susanne Granegger, Ulli Horvarth, Brigitte Jankovic, J. Kaliman, G. Karanikas, H. 

Linkesch, H. Ludwig, Ch. Muller, Irmgard Neumann, J. O Grady, Adelaide Osei-Bonsu, H. Pesl, Cornelia Pones, Sonja Reiter, Eva Strobl-Jager, H. Vinaz-zer, K. Widhalm, and Ch. Zielinski. 

Angelberger P, Sinzinger H, Kolbe H, Leithner C (1981) Labelling of human platelets with in-oxine and hCc-oxine. Comparison of in vitro and clinical use for monitoring of kidney transplants. Progr Radiopharmacol 2 211-220 

The tissue engineering approach could be divided into the following steps  

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Stellite tools Stelometer tester Stem cell factor... 

Primary blood components iaclude plasma, red blood cells (erythrocytes), white blood cells (leukocytes), platelets (thrombocytes), and stem cells. Plasma consists of water dissolved proteias, ie, fibrinogen, albumins, and globulins coagulation factors and nutrients. The principal plasma-derived blood products are siagle-donor plasma (SDP), produced by sedimentation from whole blood donations fresh frozen plasma (FFP), collected both by apheresis and from whole blood collections cryoprecipitate, produced by cryoprecipitation of FFP albumin, collected through apheresis and coagulation factors, produced by fractionation from FFP and by apheresis (see Fractionation, blood-plasma fractionation). 

E. Robertson, in E. Robertson, ed., Teratocarcinomas and Embryonic Stem Cells A Practical Approach, IRL Press, Oxford, 1987, p. 71. 

The potential for improved radioprotection by combining Tempol with growth factors such as stem cell factor (SGP), which protects by quite different mechanisms, has been examined in mice (82). Both SGP alone, given 20 and 4 h before and 4 h after TBI, and Tempol alone, given 10 min before TBI, increased 30-day survival, but protection was greater than additive when the two agents were combined. 

Interleukin-1 OC and (3. IL-1 has radioprotective activity toward BM and other tissues (151,164). IL-1 is produced in response to endotoxin, other cytokines, and microbial and viral agents, primarily by monocytes and macrophages. Other nucleated cells can also produce it. IL-1 appears to play an important role in the regulation of normal hemopoiesis directly by stimulating the most primitive stem cells and indirectly by stimulating other hemopoietic factors, including G-CSF, GM-CSF, M-CSF, and IL-6. 

A critical step in radioprotection involves the IL-1 receptors. Monoclonal antibodies to the type 1 IL-1 receptor block IL-l-induced radioprotection (167). Although this receptor is not present on BM cells, it is present on fibroblasts, which suggests that the effects of IL-1 on stem cells maybe largely indirect and mediated by stromal cell activation (168). Anti-IL-1 receptor (type 1) also sensitizes normal mice to the effects of TBI, which suggests that endogenous IL-1 has an intrinsic radioprotective role. IL-6 induction by IL-1, but not CSF levels, is inhibited, which supports the concept that G-CSF and GM-CSF are insufficient by themselves at radioprotecting stem cells and indicates a contributory role for IL-6. Anti-IL-6 antibody blocks IL-1 and TNF-induced radioprotection and also decreases the intrinsic radioresistance of mice, as does anti-TNF- a (169). 

SCE protects mice from G1 death after kradiation and increases the number of surviving mucosal crypt stem cells (186) in a manner similar to lL-1. 

Fig. 1. Hypothetical kinetics of depletion of bone marrow (BM) stem cells following exposure to a lethal total-body irradiation (TBI) of 10 Gy (1000 rad) of...

Deficiency. Macrocytic anemia, megaloblastic anemia, and neurological symptoms characterize vitamin B 2 deficiency. Alterations in hematopoiesis occur because of the high requirement for vitamin B 2 for normal DNA repHcation necessary to sustain the rapid turnover of the erythrocytes. Abnormal DNA repHcation secondary to vitamin B 2 deficiency produces a defect in the nuclear maturational process of committed hematopoietic stem cells. As a result, the erythrocytes are either morphologically abnormal or die during development. 

S. B. Karkare, S. T. Cole, R. Sachdev, V. Satyagal, and J. C. Eieschko, "Production of Rat Stem Cell Eactor from BRI Cells by Microcarrier Perfusion Cultuie," paper presented at the LngineeringFoundation Conference on Biochemical Lngineering FT/, Santa Baibaia, Calif., 199T,Mnnals of New YorkMcademj of Sciences, in press. 

This seems plausible, as the time at which gonocytes become invasive coincides with periods during postnatal life and puberty when Sertoli cells are producing high amounts of hormones. The malignant gonocytes overexpress c-kit so it is possible that they might proliferate in response to stimulation by stem cell factor secreted by the Sertoli cells. ... 

Basal cells Stem cells for other airway cell types that do not interface with... 

There are undifferentiated stem cells of the blood elements in the bone marrow that differentiate and mature into erythrocytes, (red blood cells), thrombocytes (platelets), and white blood cells (leukocytes and lymphocytes). The production of erythrocytes is regulated by a hormone, erythropoietin (see the section on kidney toxicity), that is synthetized and excreted by the kidney. An increase in the number of premature erythrocytes is an indication of stimulation of erythropoiesis, i.e., increased production of erythrocytes in anemia due to continuous bleeding. 

A B lymphocyte is a specific type of white blood cell (leucocyte) derived from bone marrow stem cells. Each B lymphocyte expresses an immunoglobulin (antibody) specific for a particular antigen. Following antigenic stimulation, a B lymphocyte may differentiate and multiply into plasma cells that secrete large quantities of monoclonal antibody. 

Cellular cytokines (interferons, G-CSF) and immune response modifiers originally produced from human cells, most often leukocytes, have now been replaced with recombinant products with well-defined structure/function. Futuristic advances in experimental hematology portend development of human blood cells produced from the hemopoetic stem cells. Yet for the foreseeable future, homologous blood donated by healthy, altruistic voluntary blood donors remains the principal source of safe and adequate supply of blood and blood products for transfusion therapy. 

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