Terrell H. Hamilton

Regulation by estrogen of organ-specific synthesis of a nuclear acidic protein

Abstract Estradiol-17β acting in vivo in the uterus of the ovariectomized adult rat stimulates about 75% the incorporation of 3H-tryptophan into the fraction of nuclear acidic protein extracted in 0. 05 N NaOH. The electrophoretic distribution of this nuclear protein fraction in gels containing 10% acrylamide, 5 M urea, and 0. 1% sodium dodecyl sulfate indicates that this stimulation of incorporation is restricted almost entirely to a single band. No appreciable stimulation of incorporation of 3 H-tryptophan by the hormone was observed in the acidic protein of hepatic nuclei. It is concluded that induction of organ-specific synthesis of a nuclear acidic protein is an important aspect of the regulation of gene activation by estrogen in the uterus.

ON PREDICTING INSULAR VARIATION IN ENDEMISM AND SYMPATRY FOR THE DARWIN FINCHES IN THE GALAPAGOS ARCHIPELAGO

For interisland variation in number of Darwin Finches in the Galapagos Archipelago, endemism is predicted by nearest-neighbor isolation; and species abundance or sympatry is predicted by average isolation. Nearest-neighbor isolation is measured by distance from the nearest island, and average isolation is the average distance to all other islands in the archipelago. The two measures of isolation are of little predictive value when tested for the avifaunas of six other archipelagos or oceanic island groupings. In these situations, area is a better predictor of species abundance or endemism; and the role of isolation appears only when measured as distance from the major avifaunal source region (e.g., New Guinea for islands of the East-central Pacific; African mainland for islands in the Gulf of Guinea). Insular isolation in these instances is, however, a relatively small contributor to variance of species number when contrasted with the greater contributions made by insular area. That numbers of insular species and endemics are respectively predicted by average and nearest-neighbor isolation, and not by area, only in the Darwin Finches demonstrates emphatically the importance of isolation in regulating endemism and species abundance (= sympatry) in the adaptive radiation of monophyletic bird groups within archipelagos. This generalization appears valid only when the intra-archipelagic speciations are mostly between islands, and not intraisland in site of origin from parental forms. It would appear to be less valid during the postspeciation, phyletic- specialization phase of radiation. It is presumed that the natural regulations of endemism and species abundance for insular avifaunas are stochastic in process. By this hypothesis, chance elements associated with isolation are of major importance early in the adaptive radiation of monophyletic bird groups, and less important later in this radiation when deterministic and chance elements associated with ecology (area, habitat, niche) predominate.

Early estrogen action. Stimulation of the synthesis of methylated ribosomal and transfer RNAs.

The effects of estrogen on the rates of incorporation in vivo of radioactive uridine and Me-methionine, administered together, into RNA in the uterus of the ovariectomized adult rat have been measured. The ratio of incorporation of methionine to uridine during a 45-min labeling period was increased several-fold by hormone treatment. The increased rate of methylation was apparent in the uterus taken from the rat administered estrogen for 1 h, and the effect was more striking following 2 and 3 h of hormone treatment. This stimulation of methylation of RNA occurred in association with an increase in the whole-organ concentration of RNA. Analysis of the doubly-labeled uterine RNA on sucrose gradients revealed that the methylated species were mainly ribosomal and transfer RNA. These results show that very little methylation of RNA occurs in the atrophied uterus of the ovariectomized rat. During the first 3 h following estrogen administration to the ovariectomized animal, an increasing percentage of the newly synthesized RNA formed by the uterus is methylated ribosomal and transfer RNA. This result is discussed in light of recent studies of the efficiency of processing of ribosomal precursor RNA, as well as the synthesis of high-molecular-weight heterogeneous RNA in the early action of estrogen.

Comparative effects of estradiol-17β and estriol on uterine RNA polymerases I, II, and III in vivo

Abstract The early and later effects of estradiol-17β and estriol on the RNA polymerase activities of uterine nuclei obtained from ovariectomized rats were compared. At 4 hr of hormone action both estradiol-17β and estriol stimulated the activity of polymerase I, but not the activities of polymerases II and III. At 24 hr, however, the effect of estriol had disappeared, whereas estradiol-17β stimulated all three polymerase activities. These results indicate that estrogen-induced growth of the uterus occurs in two phases, initiation and maintenance. Estriol initiates uterine growth, but does not maintain the process. Estradiol-17β, in contrast, does both. The differences in the effects of the two estrogens may reside in their different binding affinities.

Sequential stimulation of synthesis of two specific cytoplasmic proteins in early estrogen action

Abstract The early effect of administration of estrogen on the synthesis of cytosol proteins in the uterus of the ovariectomized rat was analyzed. A sequential stimulation of two cytoplasmic proteins, having molecular weights of 44,200 and 70,500, was observed. The former protein is probably the IP protein described by Gorski and his colleagues. The latter and larger protein has a molecular weight equivalent to that of a nonhistone chromosomal protein recently described by our laboratory, and may be the cytoplasmic forerunner of that chromosomal protein.

Identification of two forms of progesterone receptor from chick oviduct cytosol using non-denaturing gel electrophoresis☆

Non-denaturing polyacrylamide gel electrophoresis and non-denaturing agarose gel electrophoresis have been used to resolve [3H]R5020-binding components from chick oviduct cytosol. From both gel systems 2 peaks of bound radioactivity are resolved which display these properties of authentic progesterone receptor: binding of R5020: steroid specificity, saturability, and restriction to target tissues. The two peaks are approximately equal in magnitude, and there is no evidence for interconversion of the 2 peaks. The presence or absence of 10-20 mM sodium molybdate during cytosol preparation had no effect on the magnitude or mobility of either peak. Neither peak contains salt-dissociable components which affect its electrophoretic properties, suggesting a possible alteration of native receptor forms during electrophoresis.