Of blood cells

Each type of blood cell has its own distribution of mass densities (Fig. 2). Most blood cell separators are based on the formation of blood components into layers by density gradient only. Some cell separators, ie, Haemonetics MGS, apply methods based on a combination of mass density and cell size. 

A small (25-kg), portable apheresis system, available in 1993, is designed to meet a wide variety of blood cell separation needs. The role of the apheresis system is to control the behavior, separation, and collection of blood components from the bowl while maintaining maximum donor safety. The system controls the flow rates of blood and components through variable pump speeds. It directs the flow of components out of the bowl, by fully automatic opening and closing of valves based on the output of the system sensors. The system monitors the separation of blood components in the bowl by an optics system that aims at the shoulder of the bowl. A sensor on the effluent line monitors the flow of components out of the bowl. 

Surface Tension. Interfacial surface tension between fluid and filter media is considered to play a role in the adhesion of blood cells to synthetic fibers. Interfacial tension is a result of the interaction between the surface tension of the fluid and the filter media. Direct experimental evidence has shown that varying this interfacial tension influences the adhesion of blood cells to biomaterials. The viscosity of the blood product is important in the shear forces of the fluid to the attached cells viscosity of a red cell concentrate is at least 500 times that of a platelet concentrate. This has a considerable effect on the shear and flow rates through the filter. The surface stickiness plays a role in the critical shear force for detachment of adhered blood cells. 

Clinical chemistry analy2ets ate automated instmments used for measuring concentrations of the various chemical constituents of blood or other body fluids. For a discussion of the related category of instmments used for the measurement of blood cell parameters, see Automated instruments, HEMATOLOGY. 

The aperture impedance principle of blood cell counting and sizing, also called the Coulter principle (5), exploits the high electrical resistivity of blood cell membranes. Red blood cells, white blood cells, and blood platelets can all be counted. In the aperture impedance method, blood cells are first diluted and suspended ia an electrolytic medium, then drawn through a narrow orifice (aperture) separating two electrodes (Fig. 1). In the simplest form of the method, a d-c current flows between the electrodes, which are held at different electrical potentials. The resistive cells reduce the current as the cells pass through the aperture, and the current drop is sensed as a change in the aperture resistance. 

Hematopoietic Growth Factors. Figure 1 Schema of hematopoiesis, including some of the growth factors that influence the production of blood cells. 

The use of recombinant hematopoietic growth factors (i.e., the commercially available forms of the native products) has been evaluated in many disorders affecting all types of blood cells. Recombinant human hematopoietic growth factors are identified as rHu. Not all uses discussed have received regulatory approval in all countries. 

Myelosuppression is suppression of the production of blood cells by the bone marrow. 

MANAGING HONE MARROW SUPPRESSION. Bone marrow suppression is a potentially dangerous adverse reaction resulting in decreased production of blood cells. Bone marrow suppression is manifested by abnormal laboratory test results and clinical evidence of leukopenia, thrombocytopenia, or anemia For example, there is a decrease in the white blood cells or leukocytes (leukopenia), a decrease in the thrombocytes (thrombocytopenia), and a decrease in the red blood cells, resulting in anemia Fhtients with leukopenia have a decreased resistance to infection, and the nurse must monitor them closely for any signs of infection. 

Hematopoiesis is defined as the development and maturation of blood cells and their precursors. In utero, hematopoiesis may occur in the liver, spleen, and bone marrow. However, after birth, it occurs exclusively in the bone marrow. All blood cells are generated from a common hematopoietic precursor, or stem cell. These stem cells are self-renewing and pluripotent and thus are able to commit to any one of the different lines of maturation that give rise to platelet-producing megakaryocytes, lymphoid, erythroid, and myeloid cells. The myeloid cell line produces monocytes, basophils, neutrophils, and eosinophils, whereas the lymphoid stem cell differentiates to form circulating B and T lymphocytes. In contrast to the ordered development of normal cells, the development of leukemia seems to represent an arrest in differentiation at an early phase in the continuum of stem cell to mature cell.1... 

Engstad C. S., Guteberg T. J., Osterud B. Modulation of blood cell activation by four commonly used anticoagulants. Thromb Haemost 1997 77,690-6. 

Like the walls of other capillaries, the glomerular capillary wall consists of a single layer of endothelial cells. However, these cells are specialized in that they are fenestrated. The presence of large pores in these capillaries makes them 100 times more permeable than the typical capillary. These pores are too small, however, to permit the passage of blood cells through them. 

Most cytokines act upon, or are produced by, leukocytes (white blood cells), which constitute the immune and inflammatory systems (Box 8.1). They thus play a central role in regulating both immune and inflammatory function and in related processes such as haematopoiesis (the production of blood cells from haematopoietic stem cells in the adult bone marrow), as well as in wound healing. Indeed, several immunosuppressive and anti-inflammatory drugs are now known to induce their biological effects by regulating production of several cytokines. 

Table 10.4 The range of blood cells that are ultimately produced upon the differentiation of pluripotential stem cells (see text for details).

However, a few caveats to these positive studies should be noted. There is considerable evidence that a variety of circulatory factors may influence the activity of blood cells and elements, and bipolar disorder patients are known to have numerous neurohormonal abnormalities... 

Figure 2.1. Development of blood cells. The development of blood cells occurs in the bone marrow. All cells arise from the differentiation of pluripotent or multipotent stem cells, which have the capacity for self-renewal, or else can divide into more mature cells types. The morphological features of the mature blood cell types is shown.

Schwerte, T., Uberbacher, D., and Pelster, B., Non-invasive imaging of blood cell concentration and blood distribution in zebrafish Danio rerio incubated in hypoxic condition in vivo, /. Exp. Biol, 206, 1299-1307, 2003. 

Cytokines are produced mainly by the leukocytes (white blood cells). They are potent polypeptide molecules that regulate the immune and inflammation functions, as well as hematopoiesis (production of blood cells) and wound healing. There are two major classes of cytokines (1) lymphokines and monokines and (2) growth factors. 

Clinically, GM-CSF is used to stimulate production of blood cells, in particular, in patients who have received chemotherapy. M-CSF is a glycoprotein... 

Bone marrow is the spongy tissue inside the cavities of our bones. Bone marrow stem cells grow and divide into the various types of blood cells white blood cells (leukocytes) that fight infection, red blood cells (erythrocytes) that transport oxygen, and platelets that are the agents for clotting. 

Although the concept of flow cytometry originated in studies of blood cells and tumor cells (for review, see Darzynkiewicz et ak, 2004), flow cytometric procedures are now used routinely in disciplines as diverse as immunology, the neurosciences, nutritional sciences, pharmacology, parasitology, and marine biology. This chapter offers an introduction to the theory and practice of analytical flow cytometry, with emphasis on applications in the neurosciences. 

Blood plasma is the liquid, mostly water, that carries several types of blood cells as well as nutrients, and other chemicals, such as hormones, that need to be transported around the body. 

In addition to erythrocytes, blood contains white blood cells, called leukocytes, of several types, and platelets, also called thrombocytes, which control blood clotting. Hematopoiesis (from the Greek, haimo, for blood, and poiein for to make ) is the process by which the elements of the blood are formed. The marrow of bone contains so-called stem cells which are immature predecessors of these three types of blood cells. Chemicals that are toxic to bone marrow can lead to anemia (decreased levels of erythrocytes), leukopenia (decreased numbers of leukocytes), or thrombocytopenia. Pancytopenia, a severe form of poisoning, refers to the reduction in circulatory levels of all three elements of the blood. One or more of these conditions can result from sufficiently intense exposure to chemicals such as benzene, arsenic, the explosive trinitrotoluene (TNT), gold, certain drugs, and ionizing radiation. Health consequences can range... 

Fig. 13.2 Thiopurine methyl transferase (TPMT) methylator genotypes in Crohn s disease during azathioprine/6-mercaptopurine (AZA/6-MP) treatment influences the time in months to development of severe myelosuppression. However, only 27% of patients with Crohn s disease and myelo-suppression during AZA therapy had mutant alleles of the TPMT gene associated with enzyme deficiency. Myelosuppression is more often caused by other factors. Continued monitoring of blood cell counts remains mandatory in patients treated with AZA. (Reproduced from ref 35.)...

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