View clinical trials related to Healthy.
Filter by:The purpose of this study is to investigate whether topically applied constituents of green tea [caffeine or (-)-epigallocatechin gallate; EGCG] have a protective effect on skin exposed to ultraviolet light (UV).
This is a pilot study to first measure the cross-sectional relationship between variations in physicians� vignette scores and aggregated scores of individual physicians� patient health outcomes; and second to (longitudinally) determine whether feedback of vignette scores improves physicians� clinical performance as measured by vignettes
This study will examine how nitrite infusions affect exercise tolerance (how much a person can exercise before having to stop). Exercise ability is limited by how fast oxygen can be delivered to the body and how fast the body can produce energy. Both of these processes are affected by nitric oxide (NO), a gas produced by cells that line blood vessels. NO is important in regulating blood vessel dilation, and consequently, blood flow. Nitrite may act as a storehouse for nitric oxide and be able to improve exercise tolerance. Healthy normal volunteers between 21 and 45 years of age who can use an exercise bicycle may be eligible for this study. Candidates are screened with a medical history, physical examination, electrocardiogram, breathing tests, blood tests, and a pregnancy test for women who are able to bear children. Pregnant women are excluded from the study. The screening session includes practice exercise on the bicycle. Participants exercise on a stationery exercise bicycle for about 30 minutes on each of two study days. During the test, they breathe in and out of a mouthpiece that allows inhaled and exhaled respiratory gases to be measured. Before subjects begin to exercise, a small tube is placed in the artery of their forearm inside the elbow. A longer tube called a central line is placed in a deeper vein in the neck after the area has been numbed. A thinner tube, called a pulmonary artery catheter, is placed through the central line and advanced into the chambers of the heart, through the heart valve, and into the lung artery. This catheter measures various pressures directly in the heart and lungs. Blood samples are drawn through the catheter also, to avoid the need for multiple needle sticks. Another tube is placed in the vein of the other arm to deliver medications. Thirty minutes after all the tubes are placed, a blood sample is drawn for baseline measurements. Then, either saline (sterile salt water) or nitrite is injected into the tube in the arm vein. Thirty minutes after the injection, the subject starts exercising on the bicycle. The work setting on the bicycle is increased every minute, and the subject pedals until he or she is too tired to continue. During the test, a small blood sample is collected every 2 minutes. Heart rate, blood pressure, and heart rhythms are continuously monitored. After the test on the first day, participants are admitted to the hospital to rest for the remainder of the afternoon and evening. The tubes are kept in place for the following morning, when the procedure is repeated exactly as before, except that subjects who received saline the first day are given nitrite the second day, and vice versa.
The purpose of this study is to determine whether levodopa, pergolid, rivastigmine, or modafinil are effective in boosting semantic language acquisition in healthy subjects.
This study looks at the role of a specific brain chemical system in the mood and attention symptoms seen in major depression and bipolar disorders using functional brain imaging.
This study will try to learn more about complex regional pain syndrome, or CRPS (previously known as reflex sympathetic dystrophy, spreading neuralgia, and sympathalgia), by examining the release of small proteins in the blood of patients with this condition. Patients with CRPS usually have three types of symptoms: - Sensory abnormalities increased sensitivity to pain or a painful reaction to a harmless stimulus - Perfusion abnormalities alterations in blood flow, temperature abnormality, swelling, decrease or increased nail growth, and hair and skin changes - Motor abnormalities weakness, guarding (Holding the limb in such a fashion that it minimizes accidental or intentional contact from possible sources of pain), and atrophy (wasting) The cause of CRPS is unknown, and there are no definitive diagnostic tests for the condition. Because early treatment improves the prognosis of CRPS, a test that enables early diagnosis would be important for optimal medical management. The findings of this study may contribute to the development of such a test and possibly new drug treatments. Normal healthy volunteers and patients of any age with complex regional pain syndrome who are in otherwise good general health may be eligible for this study. Participants will have a medical history, physical examination and collection of a blood sample. They will fill out several questionnaires, providing information on their health, personality, mood, pain levels, and symptoms. Participation in the study requires one outpatient clinic visit.
This study will use high-resolution magnetic resonance imaging (MRI) to look for subtle differences in brain anatomy between patients with focal hand dystonia (also called writer s cramp) and healthy normal volunteers. Patients with hand dystonia have prolonged muscle contractions that cause sustained twisting movements and abnormal postures. These abnormal movements often occur with activities such as writing, typing, playing certain musical instruments such as guitar or piano, or playing golf or darts. Patients with focal hand dystonia and healthy volunteers will be enrolled in this study. Patients will be recruited from NINDS s database of patients with focal hand dystonia. Volunteers will be selected to match the patients in age, sex and handedness. This study involves two visits to the NIH Clinical Center. The first visit is a screening visit, in which patients and volunteers will have a medical history, physical examination, neurological examination, and assessment of handedness. Women of childbearing age will be screened with a pregnancy test. Pregnant women are exclude from this study. Those who join the study will return for a second visit for magnetic resonance imaging. MRI uses a magnetic field and radio waves to produce images of the brain. For the procedure, the participant lies still on a stretcher that is moved into the scanner (a narrow cylinder containing the magnet). Earplugs are worn to muffle loud noises caused by electrical switching of radio frequency circuits used in the scanning process. The scan will last about 45 to 60 minutes, at most. Some volunteers may be asked to return for a third visit to obtain a second MRI on a different scanner.
This study will evaluate new magnetic resonance imaging (MRI ) methods using a MRI machine more powerful than those in most hospitals. MRI is a diagnostic tool that uses a large magnet and radio waves to produce images of the human body. It can also provide information about brain chemistry and physiology. This study will use the new MRI hardware and methods to measure blood flow and metabolism in regions of the brain during simple tasks, such as listening to tones or watching flashing checkerboards. Healthy normal volunteers will undergo MRI scanning. For this procedure, the person lies on a stretcher that is moved into a MRI machine, which produces a strong magnetic field. A special lightweight coil is placed on the person's head to obtain better pictures. The scan time ranges from 20 minutes to 2 hours, with the average scan lasting between 45 and 90 minutes. During the MRI, the person may be asked to perform simple tasks, such as listening to tones or watching a screen, tapping fingers or moving a hand. More complex tasks may require thinking about tones or pictures and responding to them by pressing buttons. The images produced in this study will be compared with those produced using standard MRI. The results will be used to develop improved imaging methods for better patient care and research.
Positron Emission Tomography (PET) is a technique used to investigate the functional activity of the brain. The PET technique allows doctors to study the normal biochemical and metabolic processes of the central nervous system of normal individuals and patients with neurologic illnesses without physical / structural damage to the brain. Radioactive water H215O in PET scans permits good visualization of areas of the brain related to speech. Most of the PET scan studies conducted have concentrated on learning about how language is formed and decoded. Few studies have been conducted on speech production. This study aims to use radioactive water (H215O) and Positron Emission Tomography (PET scan) to measure blood flow to different areas of the brain in order to better understand the mechanisms involved in speech motor control. When a region of the brain is active, it uses more fuel in the form of oxygen and sugar (glucose). As the brain uses more fuel it produces more waste products, carbon dioxide and water. Blood carries fuel to the brain and waste products away from the brain. As brain activity increases blood flow to and from the area of activity increases also. Knowing these facts, researchers can use radioactive chemicals (H215O) and PET scans to observe what areas of the brain are receiving more blood flow. Researchers will ask patients to perform tasks that will affect speech, voice, and language. At the same time patients will undergo a PET scan. The tasks are designed to help researchers observe the blood flow to brain areas associated with voicebox (laryngeal) functions, movement of muscles in the jaw, tongue, and mouth, and other aspects of motor speech. Special studies will be conducted to evaluate how certain therapies and tasks can draw out symptoms in illnesses in which speech and language are affected. Results of these tests will be used in other studies to evaluate the neurologic mechanisms of diseases like Tourette's syndrome and parkinson's disease.<TAB>