Note: Participants with conditions meeting exclusion criteria at a particular evaluation for eligibility may be re-evaluated at a later time to determine if the conditions have changed so that all entry criteria are met. In particular, if blood pressure > 140/95 or > 95th percentile for age/height while the participant is on less than three antihypertensive agents, the participant may be re-evaluated for eligibility after adding other antihypertensive agents so long as the total number of agents does not exceed three.