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Biomedical subjects

U Nudel

Publications and source records attributed to U Nudel.

15 recordsLinked to original sources
PubMed1979

Defects in DNA and globin messenger RNA in homozygotes for hemoglobin Lepore.

Globin messenger RNA (mRNA) isolated from three patients homozygous for hemoglobin Lepore is shown to have a marked reduction of the amount of beta-like globin mRNA (Lepore-globin mRNA sequences) compared with alpha-globin mRNA by molecular hybridization. The relative amounts of alpha- and Lepore mRNA are similar to the amounts of alpha- and Lepore globin synthesized in intact cells and by isolated mRNA in a cell-free system. It is also demonstrated that Lepore-globin mRNA can completely hybridize to full-length or nearly full-length beta-globin specific complementary DNA and protect it from nuclease digestion, indicating close homology between the delta-mRNA sequences present in Lepore mRNA and the beta-complementary-DNA probe. We have also quantitated the numbers of beta-like globin gene sequences in genomic Lepore DNA by molecular hybridization and demonstrated a reduction in their number consistent with the Lepore gene being a delta beta-gene fusion product.

Adolescent↗
PubMed1978

Regulation of differentiation in normal and transformed erythroid cells.

Studies are described employing two erythropoietic systems to elucidate regulatory mechanisms that control both normal erythropoiesis and erythroid differentiation of transformed hemopoietic precursors. Evidence is provided suggesting that normal erythroid cell precursors require erythropoietin as a growth factor that regulates the number of precursors capable of differentiating. Murine erythroleukemia cells proliferate without need of erythropoietin; they show a variable, generally low, rate of spontaneous differentiation and a brisk rate of erythropoiesis in response to a variety of chemical agents. Present studies suggest that these chemical inducers initiate a series of events including cell surface related changes, alterations in cell cycle kinetics, and modifications of chromatin and DNA structure which result in the irreversible commitment of these leukemia cells to erythroid differentiation and the synthesis of red-cell-specific products.

Cell Cycle↗
PubMed1978

Induction of murine erythroleukemia differentiation by actinomycin D.

Murine erythroleukemia cells are induced to differentiate by 0.5-5 ng of actinomycin D per ml. Murine erythroleukemia cells cultured with actinomycin D prolong cell doubling time but achieve the same density after 5 days as cells without inducer. Actinomycin D causes over 95% of the cells to become benzidine-reactive. [(3)H]Actinomycin D uptake into DNA can be detected within 2 hr and reaches a maximum (approximately 0.1 pmol/10(6) cells) by 10-12 hr. It is estimated that about one out of 10(5) dG.dC pairs is bound to actinomycin D. Commitment to differentiation, assayed by transfer of cells to culture without inducer, was detected as early as 5 hr. Unlike Me(2)SO, which causes a transient prolongation in G(1) at about 15-20 hr, cells cultured with actinomycin D show a more sustained increase in the proportion of the cells in G(1). Globin mRNA accumulation was detectable by 19 hr in culture. Alteration in DNA stability in alkaline sucrose gradients was detected by 19 hr. Actinomycin D induces synthesis of Hb(maj) and Hb(min) in approximately equal amounts. A decrease in rates of synthesis of RNA, DNA, and total protein occurs in cells cultured with actinomycin D, as well as in cells cultured with Me(2)SO. No evidence for an early action of actinomycin D at the plasma membrane was obtained by measurement of changes in cell volume or (86)RbCl uptake. Taken together, the present results indicate that actinomycin D is a potent inducer of differentiation of murine erythroleukemia cells and suggest that the target of its effect may be at the level of DNA.

Animals↗
PubMed1978

Changes in DNA associated with induction of erythroid differentiation by dimethyl sulfoxide in murine erythroleukemia cells.

The Friend virus-infected murine erythroleukemia cell can be induced to differentiate along erythroid cells in culture with various compounds, including dimethyl sulfoxide. DNA from murine erythroleukemia cells cultured with dimethyl sulfoxide shows a decrease in sedimentation rate in alkaline sucrose gradients after alkali lysis of the cells. These changes can be detected as early as 27 hr after the beginning of culture. Similar results are observed with DNA of the cells cultured with other inducers, butyric acid and dimethylacetamide, but not with DNA from a variant cell line resistant to induction with dimethyl sulfoxide. Ultraviolet irradiation, which is known to cause similar changes in the sedimentation rate of DNA in alkaline sucrose gradients, induces differentiation of the murine erythroleukemia cells. These studies suggest that alterations in DNA may be related to events involved in the induction of differentiation of murine erythroleukemia cells by dimethyl sulfoxide.

Alkalies↗
PubMed1977

Transient inhibition of initiation of S-phase associated with dimethyl sulfoxide induction of murine erythroleukemia cells to erythroid differentiation.

The murine erythroleukemia cell (MELC) line in suspension culture can be induced to differentiate to erythroid cells by various compounds, including dimethyl sulfoxide (Me2SO). Analysis of the cell cycle, during differentiation induced by Me2SO, using thymidine incorporation, thymidine labeling index, and relative DNA content per cell as measured by flow microfluorometry, demonstrates a transient inhibition of entry of cells into S-phase of the cell cycle which is detected as early as 5 hr and is maximal about 20 hr after beginning of nonsynchronous cultures. Furthermore, in the presence of Me2SO there is restricted binding of the intercalating dye propidium iodide to chromatin from MELC in G1 phase of the cell cycle, as early as 10 hr of culture. This restricted binding of propidium iodide to chromatin is observed in MELC cultured with other inducing agents, such as butyric acid and dimethyl-acetamide, but is not detected with an Me2SO-resistant cell line cultured with Me2SO.

Cell Differentiation↗
PubMed1977

Differential effects of chemical inducers on expression of beta globin genes in murine erythroleukemia cells.

Murine erythroleukemia cells are induced to erythrodifferentiate by polar compounds such as dimethyl sulfoxide and hexamethylene bisacetamide as well as by fatty acids such as butyric acid and propionic acid. The effect of these inducers on the expression of two beta globin genes, betamaj and betamin, during the course of differentiation of the cells has been examined. After 4 days of culture with hexamethylene bisacetamide or dimethyl sulfoxide, the betamaj-containing hemoglobin (Hbmaj) predominates. By contrast, in the presence of butyric acid or propionic acid, after 4 days of culture, relatively equal amounts of Hbmaj and Hbmin are found. When cultured with dimethyl sulfoxide or hexamethylene bisacetamide, murine erythroleukemia cells synthesize more betamaj than betamin, while about equal amounts of the two globins are synthesized in the presence of butyric acid. When poly(A)-containing RNA from the cells exposed to different inducers is translated in a wheat germ cell-free system, the ratio of betamaj to betamin synthesized reflects that in whole cells. In a strain of murine erythroleukemia cells resistant to dimethyl sulfoxide (DR-10), the preferential stimulation of betamaj synthesis by hexamethylene bisacetamide of the betamin synthesis by butyric acid is more pronounced than with the dimethyl sulfoxide-sensitive cells (DS-19). These data suggest that polar compounds and fatty acids cause different expression of the betamaj and betamin genes in murine erythroleukemia cells.

Acetamides↗
PubMed1977

Tumor promoters inhibit spontaneous and induced differentiation of murine erythroleukemia cells in culture.

Addition of the potent tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), to murine erythroleukemia cell lines in suspension cultures inhibited both spontaneous differentiation and differentiation induced by hexamethylene bisacetamide (HMBA), dimethyl sulfoxide, or butyric acid. Inhibition was unrelated to cytotoxicity and was reversible. When several plant diterpenes were tested, there was a positive correlation between tumor-promoting activity and inhibition of differentiation. TPA inhibited HMBA-induced differentiation only if added prior to the time of commitment to differentiation, as assayed by scoring for differentiation after transfer of cells from HMBA to fresh medium without HMBA. TPA-mediated inhibition of differentiation was associated with a decrease in globin mRNA accumulation.

Acetamides↗
PubMed1976

Globin mRNA species containing poly(A) segments of different lengths. Their functional stability in Xenopus oocytes.

Rabbit globin mRNA species containing poly(A) segments of different lengths were prepared by partial phosphorolysis of mRNA with Escherichia coli polynucleotide phosphorylase. By varying the salt concentration and the time of incubation of the phosphorolysis mixture, as well as performing oligo(dT)-cellulose chromatography at 22 degrees C and at 4 degrees C, globin mRNA preparations containing poly(A) segments of approximately 122, 95, 68, 39, 32, 21, and 16 adenylate residues were obtained. It was found that the functional stability of the mRNA species containing 32 or more adenylate residues after injection into Xenopus laevis oocytes equaled that of the native globin mRNA. On the other hand, the functional stability of mRNA containing an average number of 21 adenylate residues was about 30% of the native mRNA, while that of mRNA containing 16 adenylate residues was as low as poly(A)-free globin MRNA.

Animals↗
PubMed1975

Blocks in elongation and initiation of protein synthesis induced by interferon treatment in mouse L cells.

Synthesis of polypeptide chains coded by exogenous messenger RNAs is inhibited in cell-free extracts from interferon-treated mouse L cells, due to a "deficiency" in some specific tRNA species. A detailed analysis shows that polypeptide chain elongation is blocked and incomplete chains are formed. After a few minutes, however, initiation of new polypeptide chains is also blocked. Messenger RNA still binds to ribosomes but initiator Met-tRNA(FMET) binding is inhibited. The block in initiation appears to be secondary to the block in elongation.

Animals↗