7 Clinical Trials for Various Conditions
This study uses magnetic resonance imaging to determine whether 3 weeks of repeated exposure to Acute Intermittent Hypoxia can improve brain blood flow or blood flow regulation in healthy adults.
This study will measure brain activity in individuals performing language tasks while in various states of alertness to learn more about how the central nervous system is affected by impairments such as sleepiness. Healthy normal volunteers between 20 and 40 years of age may be eligible for this study. Candidates must be non-smokers, right-handed, speak English fluently and have at least 12 years of education. They are screened with a medical history, physical examination, hearing and speech evaluation, computer task training, blood and urine tests and a late-night functional magnetic resonance imaging (fMRI) scan (see description below). Before screening and again before participating in the study, candidates wear an actigraph (a wristwatch-like device that records motion) for 7 days to provide a measure of their sleep-wake patterns. Participants undergo the following tests and procedures: * Extended wakefulness: Subjects are kept awake longer than is normal for them in their everyday life to be able to examine the brain under conditions of sleepiness. They are engaged in activities with the research staff during this waking time. * Functional magnetic resonance imaging: Subjects undergo five separate fMRI scans-one during screening and four others during the main part of the study. fMRI uses a magnetic field and radio waves to produce images of the brain. The subject lies on a table that is moved into the scanner (a narrow cylinder), wearing earplugs to muffle loud knocking and thumping sounds that occur during the scanning process. Brain scans are taken at rest and while the subject performs tasks, which include pressing a button upon seeing certain shapes and performing various language tasks, such as saying memorized or new words, listening to narratives, and describing everyday procedures. * Neurological, speech-language, and neuropsychological testing: Before the fMRI exams and during the period of extended wakefulness, subjects complete a series of tests that measure speech, language, memory and visual skills. Portions of the tests may be video- or autiotaped. * Interviews and questionnaires: Participants are interviewed about their handedness, sleep history, and presence of medical or neurological symptoms. * Electrophysiological studies: Subjects have an electroencephalograph (EEG) to measure the electrical activity of the brain and surface electromyography (EMG) to measure movements of muscles involved in moving and speaking. For the EEG, electrodes (small metal disks) are attached to the surface of the scalp or to a cap placed over the head. For the EMG, electrodes are attached to the skin of the face and neck by plastic or paper tape.
This study will determine whether sildenafil citrate, commonly known as Viagra, can cause increased blood flow to the brain in a wide range of multiple sclerosis (MS) patients, including women. Although people with MS can have reduced blood flow in the brain as part of the disease process, it has been observed that men with MS may have increased blood flow to the brain while taking sildenafil citrate. This study will measure brain blood flow or blood volume in men and women with MS before and after taking Viagra and compare the results to those in healthy volunteers in an effort to better understand the disease. Healthy volunteers 18 years of age and older and patients with MS between 18 and 55 years of age may be eligible for this study. Volunteers are screened with a medical history and physical examination, and patients with MS are evaluated with a complete neurological examination and screening for heart disease, including history of chest pain, heart attack, and use of nitrates. Participants undergo magnetic resonance imaging (MRI) before and after taking Viagra. During the scanning, subjects lie still on a table that can slide in and out of the cylindrical metal scanner. Scanning time varies from 20 minutes to 3 hours, with most scans lasting between 45 and 90 minutes. First, a scan is obtained of the carotid arteries (major arteries in the neck supplying blood to the brain) to determine if the arteries are narrowed, and then baseline MRI scans and measures of brain blood flow are obtained. The subject then comes out of the scanner and takes a Viagra pill. After 1 hour, the subject returns to the scanner and more scans are obtained to determine changes in brain blood flow and blood volume following Viagra. A catheter (thin plastic tube) is placed in the subject's arm before he or she enters the magnet for the second time for injection of a contrast agent called gadolinium DTPA, which allows brain structures to be distinguished more clearly.
This study will use magnetic resonance imaging (MRI) to examine and compare changes in blood flow and blood volume in the brains of normal volunteers and patients with multiple sclerosis (MS). Patients with MS-an inflammatory disease that attacks the brain and spine-may have new blood vessel formation (called angiogenesis) within the brain that may or may not contribute to the disease or help in repairing the brain. It is not known if these new vessels behave in the same way as the naturally occurring vessels. MRI uses a strong magnetic field and radio waves to generate brain images that provide information on brain chemistry, function, and blood flow. The results of this study may lead to a better understanding of MS. Healthy normal volunteers and patients with multiple sclerosis 18 years of age and older may be eligible for this study. Normal volunteers must have no history of signs or symptoms of central nervous system disease. Patients with MS will be recruited from the NIH Neuroimmunology MS clinic. All participants will undergo MRI. For this procedure, the subject lies still on a table that slides into a narrow metal cylinder (the MRI scanner). Scanning varies from 20 minutes to 3 hours, with most scans lasting between 45 and 90 minutes. During the scan, the subject wears earplugs to muffle loud knocking noises caused by electrical switching of the radio frequency circuits. The subject can communicate with the MRI staff at all times during the procedure. During the scan, the subject wears a mask and breathes in room air or air containing 6% carbon dioxide (CO2). (Room air contains approximately 0.04% CO2, which is about 150 times less than the 6% CO2. Air that is normally breathed out contains about 5% CO2.) Breathing 6% CO2 increases the amount of blood flow in the brain that can be measured using MRI. The total duration of a single 6 percent CO2 inhalation will not exceed 10 minutes. A catheter (thin plastic tube) is placed in a vein in the subject's arm before he or she enters the scanner. At some point during the scan, a contrast agent called gadolinium DTPA is injected into the vein through the catheter. This agent enables clearer images of the brain.
This study will use magnetic resonance imaging (MRI) to examine the role of prostaglandins-a type of fatty acid with hormone-like actions-in the regulation of brain blood flow. The results will provide information on how to better use this technique to study brain function, which, in turn, may lead to a better understanding of certain illnesses and more effective treatments. Healthy normal volunteers 18 years of age and older may be eligible for this study. Participants will fill out a health questionnaire and undergo a history, physical examination and MRI studies. MRI is a diagnostic tool that uses a strong magnetic field and radio waves instead of X-rays to show structural and chemical changes in tissues. During the scanning, the subject lies on a table in a narrow cylinder containing a magnetic field. An intercom system allows the subject to speak with the staff member performing the study at all times during the procedure. Four separate studies will be done-two carbon dioxide inhalation studies and two functional activation studies-as follows: Carbon dioxide inhalation (indomethacin): This study is done in two parts. In both parts, an MRI brain scan is done. During the scan, the subject inhales an air mixture containing 6% carbon dioxide through a facemask or mouthpiece. Blood pressure and heart rate are monitored during inhalation of the mixture. For the second part of the study, indomethacin-a non-steroidal anti-inflammatory drug-is injected through a catheter (thin flexible tube) in an arm vein. Indomethacin inhibits prostaglandin production. Total scan time averages between 45 and 90 minutes, with a maximum of 2 hours. Carbon dioxide inhalation (rofecoxib and celecoxib): This study is identical to the one above, except either rofecoxib or celecoxib is given instead of indomethacin. Both of these drugs are also non-steroidal anti-inflammatory drugs that inhibit prostaglandin production. Unlike indomethacin, rofecoxib and celecoxib are given orally instead of through a vein, so, to allow time for the drug to be absorbed, the second scan is delayed for 2 hours. Functional activation (indomethacin): This study is done in two parts. In both parts, a MRI brain scan is done. During the study, the subject performs a simple motor task, such as finger tapping. For the second part of the study, indomethacin is injected through a catheter in an arm vein. Functional activation (rofecoxib and celecoxib): This study is identical to the indomethacin functional activation study, except either rofecoxib or celecoxib is given instead of indomethacin. Because they are given orally instead of through a vein, the second scan is delayed 2 hours to allow time for the drug to be absorbed.
This study will evaluate magnetic resonance imaging (MRI ) methods for measuring changes in the brain's blood flow during hypercapnia (a condition of excess carbon dioxide in the blood). MRI is a diagnostic tool that uses a large magnet and radio waves to produce images of the body without X-rays. Healthy normal volunteers in this study may have as many as six MRI scans over a 2-year period. For this procedure, the person lies on a stretcher placed in a strong magnetic field produced by the MRI machine. During the scan, the person's blood carbon dioxide (CO2 ) levels will be increased either by: 1) breathing air mixtures containing up to 5% CO2; or 2) receiving an intravenous (I.V.) injection of a drug called acetazolamide. Persons who breathe CO2 will have their heart rate, blood pressure and oxygen levels monitored throughout the procedure. Those receiving acetazolamide will have the drug injected intravenously (I.V.) into an arm vein. If the volunteer experiences any unpleasant side effects from the CO2 or acetazolamide, the study will be stopped. The information gained from this study will be used to develop better ways to study brain function, possibly leading to better diagnostic and treatment methods.
The purpose of this study is to examine how a part of the brain called the hippocampus contributes to memory changes that occur with aging and Alzheimer's disease (AD). Memory problems are the most important early symptoms of AD. The hippocampal region of the brain may be responsible for many age- and AD-related memory disorders. This study will use magnetic resonance imaging (MRI) scans to examine the structure, chemical composition, and function of the hippocampus in participants with AD, participants with mild memory problems, participants who are healthy but are at risk for AD, and healthy volunteers. Participants in this study will undergo MRI scans of the brain. During the MRI, participants will perform memory tests to demonstrate hippocampal functioning.