The extraction by micrococcal nuclease of glucocorticoid receptors and mouse mammary tumor virus DNA sequences is dissociated

Glucocorticoid receptors (RG) and mammary tumor virus (MM-TV) DNA sequences were extracted by micrococcal nuclease digestion from the nuclei of C3H mouse mammary tumor cells in order to specify their relative distribution in chromatin. RG was labelled and translocated into the nuclei by incubating cells with 3H Dexamethasone (3H Dex). The purified nuclei were then treated at 2 degrees C with micrococcal nuclease. Three chromatin fractions were successively obtained: an isotonic extract (ne3H1), ahypotonic extract (ne2) and the residual pellet (P). The Dex-RG complexes were measured by the hydroxyapatite technique. The MMTV DNA sequences were titrated by molecular hybridization with an excess of MMTV radioactive cDNA probe. Up to 75% of the nuclear 3H Dex and the MMTV radioactive cDNA probe. Up to 75% of the nuclear 3H Dex and MMTV DNA sequences were extracted in a concentration dependent manner while only 10-15% of nucleic acids became soluble in 10% perchloric acid. The extracted 3H Dex-RG complex was found to be partly bound to soluble chromatin and partly free. The free complex displayed similar sedimentation constants (4S, 7S) and DNA binding ability to the cytosol receptor. The 3H Dex-RG complexes were 2 to 8 fold more concentrated in ne1, which is known to be enriched in active chromatin, than in ne2. Conversely, the concentration of MMTV DNA sequences per microgram DNA was the same in the three nuclear fractions. These results suggest that the Dex-RG complexes are concentrated in an active fraction of chromatin. We propose that, among the 20-30 copies of MMTV genes per haploid genome, only a small proportion are transcribed or regulated.

Interindividual and interspecies variation in the metabolism of the hallucinogen 4-methoxyamphetamine

1. The qualitative and quantitative aspects of the urinary elimination of orally administered 4-methoxy[14C]amphetamine have been examined in the rat and guinea-pig and in three volunteer human subjects, to determine interspecies and interindividual variations in disposition of the drug. 2. Both rat and guinea-pig excreted 70--80% of the administered dose(6 mg/kg) in the urine within 24 h, mainly as metabolites. 3. In the guinea-pig, the drug was metabolized by O-demethylation to give 4-hydroxyamphetamine, which was excreted free (4% dose) and conjugated (73%). No other metabolite was detected. 4. The rat metabolizes the drug both by O-dealkylation and by side-chain oxidation, the products being 4-hydroxyamphetamine (5% of dose free and 60% conjugated) and 1-(4'-methoxyphenyl)propan-2-one oxime (5% dose, free and conjugated). 5. In man the drug (dose 5 mg) is metabolized by O-demethylation and by side-chain oxidation. Marked intersubject variations were observed both in the array and quantitative aspects of metabolite excretion. Two subjects excreted mainly 4-hydroxyamphetamine (free and conjugated) together with smaller amounts of 1-(4'-methoxyphenyl)propan-2-one oxime and 4-hydroxynorephedrine. The third subject, however, who was previously known to exhibit a genetically determined defect in drug oxidation, was defective in O-dealkylation of 4-methoxyamphetamine, and the main excretion products were the unchanged drug together with products of side-chain oxidation, namely, 1-(4'-methoxyphenyl)propan-2-one oxime, 1-(4'-methoxyphenyl)propan-2-one and 4-methoxybenzoic acid. 6. Inter-individual differences in oxidative O-demethylation of the drug are discussed in relation to current theories on the aetiology of schizophrenia and reported fatalities arising from abuse of the drug.

[Study of a series of 158 parotidectomies and histological problems in mixed tumors of salivary glands (author's transl)]

About a homogeneous statististic of 158 parotidectomies, authors study repartition parameters of parotid gland tumors. They insist on particular surgical and evolutive problems in relation to histology sometimes very difficult.

Comparison between different forms of estrogen cytosol receptor and the nuclear receptor extracted by micrococcal nuclease

As an approach to the mechanism of the nuclear translocation of estrogen receptor, the estradiol nuclear receptor (RN) of lamb endometrium was extracted with micrococcal nuclease at 2--4 degrees and compared to the "native" 8S and to the Ca2+-transformed cytosol receptors. After extensive digestion of chromatin, giving up to 10% perchloric acid-soluble DNA and a majority of nucleosome monomers, up to 80% of the RN was extracted and under low ionic strength. This RN was found to be completely different from the partially proteolyzed Ca2+-transformed cytosol receptor. It migrated with a sedimentation constant of 4 and 6 S. The Stokes radius of the predominant form as determined by ACA 34 chromatography was 5.3 nm. The calculated apparent molecular weights were 130,000 and 90,000, respectively. The RN was able to bind DNA and was eluted from a diethylaminoethyl cellulose column at 0.23 and 0.30 M KCl. We conclude that the mechanism proposed by Puca et al., according to which the Ca2+-transformed cytosol receptor is split by a Ca2+ receptor-transforming factor into a smaller form able to cross the nuclear membrane, is very unlikely.

[Early effect of estradiol on ultrastructure of chromatin in the endometrium and hormone-dependent mammary tumors]

After in vivo and in vitro administration of aestradiol, the chromatin of lamb endometrium and of hormone-dependent 7,12-dimethylbenzanthracene Rat mammary tumors is rapidly transformed from a condensed into a diffuse chromatin. A stimulation of 3H leucine incorporation into protein was also observed. These modifications were specific for estrogen receptor ligands and for estrogen responsive tissues. In vitro tamoxifen induced pycnosis. These changes could be used to improve the prediction of hormone dependency of human breast and uterine cancers.

Nuclear translocation of the estradiol receptor: partial inhibition by ethidium bromide

Ethidium bromide (EB), an intercalating drug, has been shown to prevent the in vitro interaction of the estrogen receptor (R) with DNA (André et al., 1976). We have now studied the effect of this drug on the nuclear translocation of R in order to determine whether DNA integrity is needed for this translocation. In a cell-free reconstituted system made of purified nuclei and cytosol, the pretreatment of nuclei by EB prevented approximately half of the R nuclear translocation, but was unable to extract more than 17% of the E2-R previously translocated. A series of indirect evidences suggests that EB inhibits the nuclear translocation of R by interacting with nuclear DNA. The degree of the inhibition was related to the amount of drug bound to nuclei and was in agreement with the degree of ultrastructural modifications of chromatin. R was not irreversibly altered by the drug. The EB inhibition was only observed with DNA-containing particles and with estrogen receptor able to bind to DNA. In surviving uteri the drug also inhibited the R nuclear translocation. These resuts indicate two types of nuclear translocation of R, one sensitive and the other resistant to EB, and suggest that DNA is required for the EB-sensitive translocation.

An unusual Rh phenotype indicating heterogeneity of the Cw antigen

A family is reported in which a new Cw antigen occurred in two generations. This was recognized by 17 anti-Cw sera, but by none of the 21 anti-C sera which were, however, shown to react strongly with common Cw+ cells. This unusual finding provides evidence that the Cw antigen is in fact heterogeneous. On the basis of data obtained from absorption-elution and coagglutination studies a tentative explanation is attempted: common Cw+ phenotypes are assumed to be Cw (+1+2) and the present phenotype Cw (+1-2). Anti-Cw sera should accordingly be anti-Cw1, whereas anti-C sera should only react with Cw2.

Inhibition of estrogen-receptor-DNA interaction by intercalating drugs

Ethidium bromide, an intercalating drug, was shown to inhibit the in vitro DNA binding of the uterine estradiol-receptor complex. The inhibition was reversible, dose dependent, complete for total saturation of DNA intercalating sites by the dye, and proportional to the extent of intercalated drug. The binding of the receptor to phosphocellulose and poly(adenylic acid)-cellulose was not decreased by this drug. Similar inhibition was also obtained with 9-hydroxyellipticine. Denatured DNA was more efficient at binding the estrogen receptor than phosphocellulose or poly(adenylic acid)-cellulose but less efficient than native DNA. We conclude that the DNA binding of the estrogen receptor cannot be simply interpreted in terms of electrostatic interactions but requires a particular double-helical structure of DNA.

Mitochondrial and cytoplasmic ribosomes from Tetrahymena pyriformis. Correlative analysis by gel electrophoresis and electron microscopy

Mitochondrial and cytoplasmic ribosomes from Tetrahymena pyriformis have been isolated and studied by the techniques of polyacrylamide gel electrophoresis and electron microscopy used in conjunction. Although the two ribosome types show the same coefficient of sedimentation (80S) in sucrose gradients, they can be distinguished by gel electrophoresis: mitoribosomes migrate in a single band, considerably slower than the cytoribosome band. Electron microscope observations of negatively stained cytoribosomes show typical rounded or triangular profiles, about 275 x 230 A; mitoribosome profiles are much larger and clearly elongate, about 370 x 240 A. An electron-opaque spot delimits two nearly equal size subunits. In mixtures of mito- and cytoribosomes, each type can be recognized by its characteristic electrophoretic mobility and by its distinctive fine structure. Cytoribosomal 60S and 40S subunits each produce a distinct electrophoretic band. On the contrary, neither electrophoretic analysis, using a variety of conditions, nor electron microscopy is able to discern two different subunit types in the single 55S mitoribosomal subunit peak. Electrophoretic analysis of RNA shows that both ribosomal RNA species are present in the mitoribosomal subunit fraction. These results establish that mitoribosomes from T. pyriformis dissociate into two subunits endowed with the same sedimentation coefficient, the same electrophoretic mobility, and a similar morphology.

Mitoribosomes from Candida utilis. Morphological, physical, and chemical characterization of the monomer form and of its subunits

Highly purified mitochondrial ribosomes (mitoribosomes) have been obtained from the yeast Candida utilis. Sedimentation analysis in sucrose gradients made in 5 mM MgCl(2), 1 mM Tris, pH 7.4 and 50 mM KCl clearly distinguishes mitoribosomes (72S) from cytoplasmic ribosomes (cytoribosomes) (78S). Mitoribosomes are completely dissociated into 50S and 36S subunits at 10(-4)M MgCl(2) whereas complete dissociation of cytoribosomes into 61S and 37S subunits occurs only at 10(-6)M MgCl(2) Electron microscopy of negatively stained mitoribosomes (72S peak) shows bipartite profiles, about 265 x 210 x 200 A Characteristic views are interpreted as frontal, dorsal, and lateral projections of the particles, the latter is observed in two enantiomorphic forms Mitoribosome 50S subunits display rounded profiles bearing a conspicuous knoblike projection, reminiscent of the large bacterial subunit. The 36S subunits show a variety of angular profiles. Mitoribosomal subunits are subject to artifactual dimerization at high Mg(2+) concentration Under these conditions, a supplementary 80S peak arises. Electron microscopic observation of the 80S peak reveals closely paired particles of the 50S type Buoyant density determinations after glutaraldehyde fixation show a single peak at rho = 1.48 for mitoribosomes and 1.53 for cytoribosomes In the presence of ethylenediaminetetraacetate (EDTA), two species of RNA, 21S and 16S, are obtained from mitoribosomes, while 25S and 17S RNA are obtained from cytoribosomes It is established that the small and large RNA species are derived from the 36S and 50S subunits, respectively, by extraction of the RNA from each subunit The G + C content of the RNA is lower for mitoribosomes (33%) than for cytoribosomes (50%). Incubation of C utilis mitochondria with leucine-(14)C results in the labeling of 72S mitoribosomes. The leucine-(14)C incorporation is inhibited by chloramphenicol and resistant to cycloheximide Puromycin strips the incorporated radioactivity from the 72S mitoribosomes, which is consistent with the view that leucine-(14)C is incorporated into nascent polypeptide chains at the level of mitoribosomes

The effects of erythromycin and chloramphenicol on the ultrastructure of mitochondria in sensitive and resistant strains of Paramecium

The effects on cell structure of 12 hr to 6 days of exposure to erythromycin or chloramphenicol, two antibiotics known to inhibit specifically the mitochondrial protein synthesizing system, have been studied in the ciliate Paramecium aurelia. A wild type strain (sensitive to both antibiotics) and three mutant strains carrying cytoplasmically inherited mutations conferring resistance to one or the other antibiotic have been used In sensitive cells both antibiotics lead to a progressive and profound alteration of mitochondrial structure evidenced by an elongation of the organelle, a considerable decrease in the number of cristae, and the appearance of some abnormal lamellar cristae and of rigid plates of periodic structure. The modifications of cell structure, then, are mainly restricted to mitochondrial cristae. The three resistant mutants studied, on the contrary, retain normal or nearly normal mitochondrial structure in the presence of the antibiotic to which they are resistant. This fact is in good agreement with the postulated location in the mitochondrial DNA of the resistance mutations studied. The results are discussed in the light of present knowledge concerning the function of the mitochondrial protein-synthesizing system.