Clinical Research Directory

* INCLUSION CRITERIA: * Age 20 - 39 years or age 70 years and older. * Healthy (see exclusion criteria below). * Are able to understand the study risks and procedures, and consent to participate in the study. * Are able to read and speak English. * Caucasian or African American * Previous enrolled participants. EXCLUSION CRITERIA (SCREENING VISIT): * A medical condition that requires the use of chronic anticoagulant medication use such as warfarin, clopidogrel, heparin or antiplatelet agents other than low dose aspirin (81mg). * History of increased bleeding due to either a known medical condition or an undiagnosed cause. * A medical condition that causes impaired wound healing such as diabetes. * Current androgenic/anabolic and/or corticosteroid use or use within 90 days of the procedure (ocular corticosteroid use okay). * Current antibiotic or anti-viral use or use within 60 days of the procedure. * Active infections or chronic skin conditions that would prevent access to the biopsy area. * Taking non-steroidal anti-inflammatory agents (NSAIDs) such as Motrin (Ibuprofen), Advil (Ibuprofen) or Naprosyn (Naproxen) and the participant is unable to stop taking them 3 days before the biopsy and 1 day after the biopsy procedure. * Taking more than 81 mg of aspirin a day and the participant is unable to stop taking it for 3 days before the biopsy and 1 day after the biopsy procedure. * Allergic to Lidocaine (Xylocaine) or any other local anesthetic or the participant has had in the past a severe allergic reaction to similar drugs. * Allergic to topical betadine solution. * Severe allergy to adhesives found in tape. * HIV virus infection. * Hepatitis B or C or exposure within 6 months of visit. * History of diabetes (requiring any medical treatment other than diet and exercise) or fasting plasma glucose is \>=126 mg/dL or HbA1c \>= 6.5%. * Clinically significant hormonal dysfunction (self-reported or laboratory values out of range. Mild hypothyroidism (TSH \< 10 microIU/mL) in participants over 60 is not considered exclusion). * Kidney disease (Creatinine \>1.5 mg/dl or calculated creatinine clearance \< 50 cc/min) * Liver disease (Bilirubin \> 1.5 mg/dl (unless higher levels can be ascribed to Gilbert s disease); ALT, AST or alkaline phosphatase twice the normal serum concentration). * Severe gastrointestinal diseases such as Crohn s disease or ulcerative colitis requiring continuous treatment. * History of severe pulmonary disease such as chronic obstructive pulmonary disease (COPD) or asthma requiring continuous medication use. * History of severe psychiatric conditions associated with behavioral problems or requiring chronic medical treatment. * Currently pregnant or breastfeeding. * Participants with history of skin keloid formation during wound healing * Current illness that as judged by the study physician substantially increases the risks associated the skin biopsy(s) (active infections, allergies, etc.).