Waiting for organ transplantation: results of an analysis by an Institute of Medicine Committee

One of the most visible and contentious issues regarding the fairness of the original system of organ procurement and allocation is the argument that it resulted in great disparities in the total amount of time a patient waited for an organ (i.e. the time from registration at a transplantation center to transplant), depending on where he or she lived. In an attempt to resolve this debate, Congress charged the National Academy of Sciences, Institute of Medicine to perform an independent study of the original system and proposed rule changes. In an analysis of approximately 68,000 transplant waiting list records, the committee developed several conclusions and recommendations largely specific to liver transplantation policies. The purpose of this paper is to describe both the results of the study and the statistical foundations of the mixed-effects multinomial logistic regression model that led to the committee's conclusions.     

Divergence of primate ribosomal RNA genes as assayed by restriction enzyme analysis

Primate ribosomal RNA (rRNA) genes have been compared by restriction endonuclease mapping. In all species examined, the restriction map of the reiterated ribosomal DNA is simple (within the limits of detection by hybridization with rRNA) and is consistent with a high degree of homogeneity among the repeats. Within a species, all members have similar rDNA restriction patterns. However, different species of primates have distinctly different rDNA restriction maps; even chimpanzee and man can be discerned by their rDNA restriction patterns. Possible mechanisms for maintenance of homogeneity of the rDNA repeats within a species, while allowing divergence among closely related species, are discussed.