This project will explore the biochemical mechanisms associated with acute pain produced by bone marrow aspiration in 36 healthy subjects by : 1) Evaluation of any strong relationships of NO metabolism (as measured by plasma nitrite, nitrosated proteins, cyclic GMP, plasma hemoglobin, reticulocytes, as well as markers of inflammation) with the levels of acute pain in healthy subjects and; 2) Identification of differentially expressed genes and proteins as markers for the nature and severity of pain from bone marrow aspiration. Elucidation of these relationships may identify novel targets for intervention leading to attenuation of pain, improved treatment and less impact on quality of life (QOL) and may identify potential mechanisms for the role of NO in other inflammatory or pain syndromes.