Loading clinical trials...
Loading clinical trials...
Discover 23,284 clinical trials near Maryland. Find research studies in your area.
Showing 14261-14280 of 23,284 trials
NCT00677885
This study will measure the function of a protein called P-glycoprotein (P-gp), which is found at the blood-brain barrier, a membrane that normally prevents toxic material from entering the brain. Impaired P-gp function may allow toxins to enter the brain and cause some people to develop certain brain diseases. Healthy subjects and people with Alzheimer s disease, Parkinson s disease or frontotemporal dementia who are 35 years of age or older and in overall good health may be eligible for this study. Participants undergo the following procedures during three outpatient visits to the NIH Clinical Center: * Medical history, psychological evaluation, physical examination and blood and urine tests, including tests for illegal and addictive drugs. * PET scan: This test uses small amounts of a radioactive chemical called a tracer that labels active areas of the brain so the activity can be seen with a special camera. Before starting the scan, a catheter (plastic tube) is placed in a vein in the arm to inject the tracer. The subject lies on the scanner bed, with a special mask fitted to the head and attached to the bed to help keep the head still during the scan so the images obtained are clear. A brief initial scan is done to calibrate the scanner. Then, a radioactive tracer called \[(15)O\]H(2)O is injected into the catheter and the PET camera takes pictures of blood flow to the brain for about 60 seconds. Next, another tracer, \[(11)C\]dLop, is injected into the catheter and pictures are taken for about 2 hours to determine how much of this tracer is allowed to enter the brain. * Magnetic resonance imaging (MRI): This procedure is done within 1 year (before or after) the PET scan. MRI uses a magnetic field and radio waves to produce images of the brain. For this procedure, the patient lies on a table that can slide in and out of the scanner (a tube-like device), wearing earplugs to muffle loud knocking and thumping sounds that occur during the scan.
NCT00056433
Patients with sickle cell disease have abnormal hemoglobin (the protein in red blood cells that carries oxygen to the body). This abnormality causes red blood cells to take on a sickle shape, producing disease symptoms. Fetal hemoglobin, a type of hemoglobin present in fetuses and babies, can prevent red cells from sickling. The drug hydroxyurea increases fetal hemoglobin production in patients with sickle cell disease by making a molecule called nitric oxide. The drugs L-arginine and Sildenafil (Viagra) increase the amount or the effect of nitric oxide. This study will evaluate: * The safety of giving L-arginine or Sildenafil together with hydroxyurea in patients with sickle cell disease; * The effectiveness of L-arginine plus hydroxyurea or Sildenafil plus hydroxyurea in increasing fetal hemoglobin in patients with sickle cell disease; and * The effectiveness of L-arginine plus hydroxyurea or Sildenafil and hydroxyurea in lowering blood pressure in the lungs of patients with sickle cell disease. (Pulmonary blood pressure is elevated in about one-third of patients with sickle cell disease, and this condition increases the risk of dying from the disease.) Patients with hemoglobin S-only, S-beta-thalassemia, or other sickle cell disease genotype may be eligible for this study. Before starting treatment, patients will have a complete medical history and physical examination. All patients will take hydroxyurea once a day every day by mouth for at least 2 months. They will be admitted to the NIH Clinical Center to take their first dose of hydroxyurea, and will have blood drawn through a catheter (plastic tube placed in a vein) every hour for 6 hours for tests to determine nitric oxide levels. After discharge, they will return to the clinic once every 2 weeks to check for treatment side effects and for blood tests to monitor hemoglobin and fetal hemoglobin levels. After fetal hemoglobin levels have been stable for 2 months, patients will be admitted to the Clinical Center for their first dose of L-arginine (for men) or Sildenafil (for women). Again, blood samples will be collected through a catheter once an hour for 6 hours. If there are no complications, patients will be discharged and will continue taking hydroxyurea once a day and L-arginine or Sildenafil three times a day for at least 3 months until fetal hemoglobin levels have been stable for at least 2 months. Patients will return to the clinic for blood tests every week for 2 weeks and then every 2 weeks to monitor hemoglobin and fetal hemoglobin levels and to check for treatment side effects. Patients will have eye examinations before and during treatment. Some patients with sickle cell disease develop abnormalities in the blood vessels of the eye. Also, Sildenafil can cause temporary changes in color vision. Rarely, more serious eye problems can occur, such as bleeding from the eye blood vessels or damage to the retina a layer of tissue that lines the back of the eye. Patients will also have an echocardiogram (ultrasound of the heart) before beginning treatment, after hydroxyurea treatment, and after 1 and 3 months of combined treatment with hydroxyurea and L-arginine or Sildenafil to help measure blood pressure in the lungs. Patients who develop complications from L-arginine or Sildenafil may continue in the study on hydroxyurea alone. Patients whose fetal hemoglobin levels increase with the combination therapy of hydroxyurea and L-arginine or Sildenafil may continue to take them.