View clinical trials related to Normal Physiology.
Filter by:Background: - The way that the body burns calories is known as energy expenditure. Some studies show that when we are cold, we burn more calories to keep our bodies warm. Brown fat is a special kind of fat that can use energy to keep the body warm. Small animals and infants have been known to have brown fat for many years. Recently, it has been suggested that adult humans also have brown fat. If brown fat becomes active (burns calories) in adult humans when exposed to cold, then these people would tend to burn off more calories and might not gain weight easily. Learning more about the relationship between energy expenditure, brown fat, environmental temperature, and body temperature may help explain why some people become obese and other people do not. Objectives: - To better understand how the body burns calories when exposed to different temperatures. - To study brown fat and how it burns calories in cold temperatures. Eligibility: - Healthy men between 18 and 35 or 55 and 75 years of age. - Healthy women between 18 and 35 years of age. - To control for ethnicity, participants must be non-Hispanic whites or African Americans. Design: - Participants will be screened with a physical exam and medical history. Blood and urine samples will be collected. - Participants will stay in the Metabolic Unit of the National Institutes of Health Clinical Center as inpatients for no more than 14 days. The length of the hospital stay will depend on how participants respond to the different study temperatures. - Every afternoon, participants will walk for 30 minutes on a treadmill. All meals will be provided. - Participants will stay up to 5 hours per day in a specialized room with different temperature settings. Temperatures will range from about 61 degrees to 88 degrees Fahrenheit. Body temperature, activity, calorie burning, and cold/hot sensations will be monitored. On the study day of the coldest temperature, participants will have an imaging study to look for brown fat activity. - Participants will be compensated for their time and participation at the end of the study.
Background: - Magnetic resonance imaging (MRI) studies provide important information on the structure and function of various body systems, including the brain, muscles, joints, heart, and blood vessels. Scientific applications of MRI scans often use techniques that need to be modified or refined before they are used in clinical studies. To develop and modify these techniques for the new Philips 3T Achieva whole-body MRI scanner, researchers are interested in conducting trial MRI scans on healthy individuals and individuals with conditions that require imaging studies. Objectives: - To conduct preliminary trials of the 3T MRI facility to develop and refine MRI scanning procedures. Eligibility: - Individuals at least 18 years of age who are able to have magnetic resonance imaging. Design: - Participants will be screened with a full medical history and physical examination, as well as blood and urine tests. - Participants will have an MRI scan using the 3T scanner. Some scans may require the use of a contrast agent or radiotracer, which is a small amount of radioactive substance that will be injected before the start of the scan. Some participants may be asked to perform tasks of thinking and movement while in the scanner, in order to test the procedures required for a functional MRI scan. - No treatment will be provided as part of this protocol.
This study will use magnetic resonance spectroscopy (MRS) to measure in the brain the transfer of [13]C as it is naturally metabolized from glucose to specific chemical transmitters. From this method, we can measure the rate of production of an important excitatory neurotransmitter (glutamate) as well as an inhibitory neurotransmitter (GABA).
The purpose of this study is to use brain imaging technology to compare differences in brain structure, chemistry, and functioning in individuals with brain and mental disorders compared to healthy volunteers. Schizophrenia is a brain disorder that results from subtle changes and abnormalities in neurons. These deficits likely occur in localized regions of the brain and may result in widespread, devastating consequences. The neuronal abnormalities are inherited through a complex combination of genetic and environmental factors. Brain imaging technologies can be used to better characterize brain changes in individuals with schizophrenia. This study will use magnetic resonance imaging (MRI) scans to identify predictable, quantifiable abnormalities in neurophysiology, neurochemistry and neuroanatomy that characterize schizophrenia and other neurological and neuropsychiatric disorders.