, 2012). Long-term bone marrow cultures (LTBMC) appear to embody many of the features of hematopoietic cell regulation in vivo, and they closely resemble

the environment of hematopoietic tissues ( Dexter, 1979 and Daniel et al., 1989). Ex vivo studies have shown that cells of the adherent layer, either spontaneously or after activation, produce a number of positive soluble factors capable of promoting the maintenance, survival, proliferation, Compound Library cell assay differentiation and extensive cell renewal of hematopoietic cells ( Eaves et al., 1991, Fibbe et al., 1988 and Herman et al., 1998). Some endogenous positive regulators, such as stem cell factor, IL-6, IL-11, IL-12, and colony-stimulating factors (CSF), among others, are involved in regulating the proliferative activity of primitive ERK inhibitor hematopoietic cells in LTBMC ( Eaves et al., 1991). The fact that

hematopoiesis can be maintained for several weeks ( Gartner and Kaplan, 1980) makes LTBMC an ideal model for investigating the modulating effects of new compounds on disorders of the hematopoietic tissues. Chlorella vulgaris (CV) is a microscopic single-celled freshwater green algae that is considered to be a biological response modifier, as demonstrated by its protective activities against viral and bacterial infections in normal and immunosuppressed mice ( Dantas and Queiroz, 1999, Hasegawa et al., 1994, Hasegawa et al., 1995, Queiroz et al., 2003 and Tanaka et al., 1986) and against tumors ( Justo et al., 2001, Konishi et al., 1985, Tanaka et al., 1984 and Tanaka et al., 1998).

Inositol oxygenase It is reported to be a rich source of antioxidants, such as lutein, α- and β- carotene, ascorbic acid and tocopherol, and it supplies large quantities of vitamins, minerals and dietary fiber ( Gurer and Ercal, 2000, Rodriguez-Garcia and Guil-Guerrero, 2008 and Vijayavel et al., 2007). Notably, CV stimulates the pool of hematopoietic stem cells and activates leukocytes, important aspects of CV-mediated modulation of the immune system of immunosuppressed hosts ( Hasegawa et al., 1990, Konishi et al., 1990 and Konishi et al., 1996). Studies from our laboratory have demonstrated that CV significantly prevents the reduced capacity of HP to form granulocyte–macrophage colonies (CFU-GM) observed in tumor-bearing, stressed and infected mice ( Dantas and Queiroz, 1999, Justo et al., 2001, Queiroz et al., 2003, Souza-Queiroz et al., 2004 and Souza-Queiroz et al., 2008). To further understand the influence of CV on hematopoiesis, we quantified hematopoietic populations in the bone marrow of mice subjected to a single or repeated stressor using flow cytometry and assessed the clonogenic capacity of myeloid cells to form CFU-GM in vivo (bone marrow) and ex vivo (LTBMC). LTBMC provided information about the impact of both stressors on functional activity from the medullar stroma and its ability to interact with hematopoietic cells.