The effect of erythropoietin on colonial growth of erythroid precursor cells in vitro.

A method is described for the colonial growth, in semi-solid medium, of erythropoietin-responsive erythroid cell precursors. The erythroid cell precursors were isolated by immune hemolysis from fetal mouse liver. Both the number of precursor cells triggered to proliferate and differentiate, and the size of the erythropoietic colonies formed, are directly dependent upon the concentration of erythropoietin included in the culture.

Multiple thoracotomy for metastatic pulmonary neoplasm.

, , 248-251. Surgical excision of solitary, metastatic, malignant lesions of the lung is reported as of benefit in certain cases in which the primary tumour apparently has been completely removed and in which there is no evidence of further metastatic spread. It has been shown that in a few instances survival for many years may be expected to follow such a procedure, while at other times the degree of palliation of pulmonary symptoms makes the operation worthwhile.

Early stimulation of RNA synthesis by erythropoietin in cultures of erythroid precursor cells.

The effect of erythropoietin on cultured erythroid precursor cells from 13-day mouse-fetal livers was examined. Within 1 hr, erythropoietin causes a 2- to 3-fold stimulation of uridine incorporation into RNA by these cells. The types of RNA preferentially stimulated by erythropoietin during the first hour of exposure of the cells to the hormone include ribosomal RNAs and their precursors, as well as 4-5S RNA.

Decreased globin messenger RNA in thalassemia detected by molecular hybridization.

In previous studies of patients with beta thalassemia, mRNA extracted from reticulocytes in peripheral blood when added to cell-free systems reproduces the deficient beta-chain synthesis characteristic of intact cells. The present studies with specific probes for alpha and beta mRNA were designed to decide whether the decreased beta mRNA activity is due to the presence of abnormal or reduced beta globin mRNA in these cells. Purified alpha and beta complementary DNAs (cDNAs) have been synthesized with RNA-instructed DNA polymerase; alpha and beta mRNAs isolated from heavy (beta-producing) and light (alpha-producing) polyribosomes of rabbit reticulocytes were used as templates.

Globin messenger RNA activity in erythroid precursor cells and the effect of erythropoietin.

Cell populations enriched for erythroid precursor cells were fractionated from 13-day fetal-mouse livers by a method of immune hemolysis. These preparations of precursors, contaminated by less than 7% hemoglobinized erythroblasts, synthesize globin at a rate less than 6% that of the unfractionated liver erythroid cell population. RNA was isolated from these precursor cells and assayed for globin mRNA activity in a cell-free system from Krebs ascites tumor.

Purification of erythropoietin-responsive cells by immune hemolysis.

Immature erythroid cell precursors from 12- and 13-day fetal mouse livers were concentrated by differential antibody-mediated hemolysis. The effect of erythropoietin on these purified erythroid cell precursors was studied in vitro. Addition of erythropoietin stimulates erythroid cells to proliferate, and to differentiate to cells that actively synthesize hemoglobin.

Revegetation following Forest Cutting: Mechanisms for Return to Steady-State Nutrient Cycling.

Dense stands of a woody, successional species, Prunus pensylvanica L., develop rapidly, with early closure of canopy and rapid attainment of high values of net annual production and nutrient accumulation. Such rapid growth following disturbance tends to minimize losses of nutrients from the ecosystem, thus promoting a return to steady-state cycling characteristic of a mature forest.

Increased efficiency of exogenous messenger RNA translation in a Krebs ascites cell lysate.

Addition of a 0.5 M KCl wash fraction from rabbit reticulocyte ribosomes causes a 3- to 10-fold increase in the extent of translation of natural mRNAs by Krebs-cell lysates. In the presence of the wash fraction, 1 pmol of rabbit or mouse 10S RNA directs the incorporation of 80 pmol of leucine into rabbit globin.

Protein synthesis: its control in erythropoiesis.

Erythropoiesis in the fetal mouse provides a model to study several important aspects of the regulation of cell differentiation and differentiated protein synthesis. Changes in the patterns of hemoglobins formed during fetal and postfetal development are shown to be associated with the substitution of the liver erythroid cell line. In the course of differentiation of yolk sac erythroid cells there are at least two classes of proteins distinguishable with respect to dependence on continued RNA formatoin.

Erythropoietin effects on fetal mouse erythroid cells. I. Cell population and hemoglobin synthesis.

The effect of the hormone, erythropoietin, on cultures of erythroblasts derived from the livers of fetal C57BL/6J mice was examined. An increase both in the content and in the rate of synthesis of normal adult mouse globin chains was detected in hormone-treated cultures. The rate of protein synthesis by individual erythroblasts does not increase in response to the hormone, whereas the absolute number of hemoglobin-synthesizing cells does increase and accounts for the observed stimulation of hemoglobin synthesis.