We report the complete 5025-base sequence of the human 28S rRNA gene. Variability within the species has been demonstrated by sequencing a variable region from six separately cloned genes. This region is one of three large subunit rRNA regions that show extreme sequence and size variation among species. The interspecies differences suggest species-specific functions for these sections, while the intraspecies heterogeneity indicates differences among ribosomes.Comparison of the human gene with a partial sequence from the chimpanzee 28S gene yields divergence rates for the two species: 0.8% for conserved regions of the gene and 3.7% for a variable region. The rapid divergence rates of variable regions in the ribosomal gene may permit answers to the question of time of separation of closely related species.

A series of clones of human natural killer (NK) cells was characterized with respect to expression of the Ti alpha and Ti beta genes of the T-cell receptor. T11+T3+ NK clones contained Ti alpha and Ti beta RNA transcripts and expressed disulfide-linked heterodimers, demonstrating the presence of a functional T-cell receptor. In contrast, T11+T3- NK clones expressed only 1.0-kilobase truncated Ti beta transcripts, without a Ti alpha transcript and no detectable surface Ti protein. Since previous studies demonstrated that Ti beta gene activation precedes Ti alpha gene activation in thymic ontogeny, the T11+T3- NK cells appear to be derived from T-lineage precursors.

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The acute effects of mineralo- and glucocorticoids on urinary electrolyte excretion were studied in the conscious, acutely potassium deprived, adrenalectomized rat. Sodium, potassium, and creatinine were measured in the urine excreted from 2.5 to 5.5 h after injection of one or more of the following steroids: aldosterone (Aldo), 9-alpha fluorocortisol (FC), deoxycorticosterone (DOC), dexamethasone (Dex), and spironolactone (Spiro). The hierarchy (a) for increasing creatinine excretion was Dex greater than FC greater than Aldo greater than DOC greater than Spiro greater than none, a hierarchy consistent with glucocorticoid potency; and (b) for producing anti-natriuresis was Aldo greater than DOC greater than or equal to FC greater than or equal to none = Spiro greater than Dex, a hierarchy consistent with mineralocorticoid potency. In contrast, the kaliuresis produced by mineralo- and glucocorticoids appears different. A "mineralocorticoid" kaliuresis is 1) elicited by anti-natriuretic doses of Aldo and FC, 2) approximately twice control UKV, 3) unrelated to changes in glomerular filtration rate (GFR), and 4) inhibited by Spiro. A "glucocorticoid" kaliuresis is 1) elicited by Dex and high doses of Aldo and FC, 2) about seven to twenty-fold greater than control UKV, 3) possibly dependent, in part, on changes in GFR, and, 4) not inhibited by Spiro. DOC was not kaliuretic at anti-natriuretic doses. The urinary Na/K ratio was an unreliable index of mineralocorticoid action.