Our understanding of the causes of disability in the older population has improved significantly over the last decade. There has also been noteworthy progress in our knowledge about the effects of selected rehabilitation interventions, especially exercise-related interventions. However, the cost-effectiveness of many rehabilitative interventions remains unclear, particularly for differing patient groups across the continuum of care. More research will be needed to evaluate the effects of managed care on rehabilitation outcomes in older persons.

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Zidovudine (AZT) is widely used in the treatment of human immunodeficiency virus (HIV) infection because of its ability to act as a false substrate for the viral reverse transcriptase. AZT in the clinical setting has also been shown to produce significant hematologic and other toxicity, even though prior reports in the literature indicate that AZT is not readily incorporated into mammalian nuclear DNA. The human myeloid leukemia cell line HL-60 was grown in the presence of radiolabeled AZT or radiolabeled deoxythymidine as an in vitro model to study AZT toxicity for human myeloid cells. Radioactivity was reversibly incorporated into the mitochondria, suggesting that AZT toxicity may result in part from its toxic effects on human mitochondria rather than on human nuclear DNA.