Anatomy, Physiology & Genetics (APG)
Uniformed Services University of the Health Sciences
4301 Jones Bridge Road
Bethesda, Maryland 20814
J. Timothy O'Neill, Ph.D.
Research Assistant Professor of Anatomy, Physiology and Genetics
Research Assistant Professor, Departments of Pediatrics
Johns Hopkins University, 1980
As an important organ system of the body, the brain has evolved processes that ensure it receives an adequate supply of oxygen and nutrients. Under stressful conditions (shock, anoxia, asphyxia), as well as changes in blood pressure, the brain blood supply remains stable, and blood flow is altered to accommodate changing needs for oxygen and glucose. Dr. O'Neill is investigating these adaptive processes by determining how some molecules (nitric oxide, adenosine, hemoglobin and neurotransmitters) act to control blood flow in the brain and the eye. Several approaches to measure blood flow are employed including, radioactive and colored microspheres, electromagnetic flow probes, and laser-Doppler techniques.
He is particularly interested in developmental aspects of blood flow control. Newborns can sustain severe brain damage when the blood, oxygen or nutrient supply to the brain is inappropriate. It appears that some of the control mechanisms operative in the adult are not present or are not fully developed in the newborn. Alternatively, some distinct mechanisms are operative during the newborn period, but are not present in adults.
Dr. O'Neill is currently exploring the interrelationship of prostaglandins and nitric oxide in the control of brain blood flow during hypotension and hypertension. He is also examining the expression of an early immediate gene (Egr-1) and its protein product during cerebral hypoxia and resuscitation. This gene is suspected to initiate many of injurious responses to ischemia and reperfusion.