Complex sentence: It is a glycoprotein, growth factor or cytokine produced by a number of different tissues to stimulate the bone marrow to produce granulocytes which it then stimulates to pulse them out of the bone marrow into the blood.
Split into simpler sentences: It is a glycoprotein, growth factor or cytokine produced by a number of different tissues to stimulate the bone marrow to produce granulocytes. G-CSF then stimulates the bone marrow to pulse them out of the marrow into the blood.