View clinical trials related to Healthy Volunteers.
Filter by:The purpose of this study is to use brain imaging technology to measure changes in blood flow to areas in the brain as individuals perform intellectual tasks. This study will use functional magnetic resonance imaging (fMRI) to examine blood flow to areas of the brain as participants engage in tasks associated with visual perception, visual recognition, and memory.
This study evaluates the effects of estrogen and progesterone on mood, the stress response, and brain function in healthy women. The purpose of this study is to evaluate how low levels of estrogen and progesterone (that occur during treatment with leuprolide acetate) compare to menstrual cycle levels of estrogen and progesterone (given during individual months of hormone add-back) on a variety of physiologic measures (brain imaging, stress testing, etc.) in healthy volunteer women without PMS. This study will investigate effects of reproductive hormones by temporarily stopping the menstrual cycle with leuprolide acetate and then giving, in sequence, the menstrual cycle hormones progesterone and estrogen. Tests (such as brain imaging or stress testing, etc.) will be performed during the different hormonal conditions (low estrogen and progesterone, progesterone add-back, estrogen add-back). The results of these studies will be compared between women without PMS and women with PMS (see also protocol 90-M-0088). At study entry, participants will undergo a physical examination. Blood, urine, and pregnancy tests will be performed. Cognitive functioning and stress response will be evaluated during the study along with brain imaging and genetic studies.
Pharmacokinetics is the term used for how the body affects a drug once it is taken. Vitamin C, also known as ascorbic acid, is an essential water soluble vitamin. Meaning, the body does not make Vitamin C it must be taken in through the diet. In this study researchers will attempt to determine how the amount of water consumed affects the level of vitamin C in the blood (specifically the plasma component of the blood). In this study researchers will take 13 subjects and place them on a Vitamin C restricted diet. Vitamin C levels will be measured twice a week on an outpatient basis until all subjects reach a desired low level of Vitamin C (12-15 micromolar plasma ascorbic acid concentration). Subjects will then be admitted and undergo 24 hour blood and urine collection. Following the collection of samples, subjects will then begin to receive Vitamin C orally (by mouth) and intravenously (injected into the vein). The dosage of Vitamin C will gradually increase from 30 mg-2500 mg divided into two daily doses. Blood and urine samples will be collected each time the dose is increased. The study will take approximately 18 weeks after which the subjects will be discharged in healthy condition.
This study will investigate the inflammatory response. People with abnormal regulation of inflammation and immune defects often have an exaggerated or depressed inflammatory response that results in poor healing of recurrent infections. This study will measure and compare amounts of inflammatory mediators (chemicals involved in the inflammatory response) in healthy normal volunteers and in patients with abnormal immune responses. Healthy normal volunteers and patients with host defense defects or excessive inflammation, as in vasculitis syndromes, may be eligible for this study. Patients must be between 6 and 65 years of age. Participants will have eight small blisters raised on the forearm using a gentle suction device. The top of the blisters will be removed with scissors and a plastic template will be placed over the blisters. The wells of the template will be filled with a salt solution or a mixture of the subject s serum (fluid part of the blood without cells) and a salt solution. Some blisters may be covered with coverslips a small round piece of very thin sterilized glass before adding the fluid. Blister fluid will be removed from the wells at 3, 5, 8, and 24 hours with a syringe and analyzed for inflammatory mediators. A scab will form over the blisters and fall off in about 2 weeks. Participants will have about 4 tablespoons of blood drawn in order to compare the inflammatory mediators in the blood with those in the blister fluid.