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Biomedical subjects

M Stroun

Publications and source records attributed to M Stroun.

At least 37 records · Page 2Linked to original sources
PubMed1994

Point mutations of the N-ras gene in the blood plasma DNA of patients with myelodysplastic syndrome or acute myelogenous leukaemia.

Oncogene mutations are frequently found in several tumour types and, among these, point mutations of the ras gene are particularly significant. A predominance of N-ras mutations has been found in the bone marrow DNA of patients with myelodysplastic syndrome (MDS) or acute myelogenous leukaemia (AML). On the other hand, increased levels of plasma DNA have previously been observed in patients suffering from various malignant diseases. In the present work we have investigated, by polymerase chain reaction (PCR), point mutations of the N-ras gene in the DNA of plasma, blood cells and bone marrow of 10 patients suffering from AML or MDS. The different ras mutations detected in five cases were always present in the plasma DNA while sometimes absent in the DNA of peripheral blood cells or bone marrow. This indicates that a bone marrow biopsy or aspiration does not necessarily contain all the malignant clones involved in the disease. Plasma could thus prove to be an easily accessible and useful material for detection and monitoring of myeloid disorders.

Base Sequence↗
PubMed1994

[Transformation of NIH/3T3 cells and SW 480 cells displaying K-ras mutation].

The spontaneous release of a glyconucleoprotein complex in the supernatant of eukaryote cell cultures is a general phenomenon independent of cell lysis. The DNA recovered from this glyconucleoprotein material contains most part of the genome. The SW 480 cell line, originating from a human colon carcinoma, presents a point mutation of the K-ras gene on both alleles. These cells in culture release the mutated K-ras gene. When crude SW 480 cell supernatant is given, without any other adjonction, to NIH/3T3 mouse cells, transformed foci appear as numerous as those occurring after a transfection provoked by a cloned E.J. ras gene administered as a calcium precipitate. The presence of a mutated ras gene in the transfected foci of the 3T3 cells has been checked by hybridization, after PCR, with an oligonucleotide probe specific to the mutation. This result was confirmed by sequencing the PCR product.

Animals↗
PubMed1989

Neoplastic characteristics of the DNA found in the plasma of cancer patients.

About one third of patients with various malignant diseases were found to have extractable amounts of DNA in their plasma whereas no DNA could be detected in normal controls. Using the test established by one of us (M.B.), which is based on decreased strand stability of cancer cell DNA, we have found that several plasma DNA originate from cancer cells.

Carcinogens↗
PubMed1987

Isolation and characterization of DNA from the plasma of cancer patients.

UNLABELLED: Ten out of 37 patients with advanced malignant diseases were found to have extractable amounts of DNA in their plasma whereas no DNA could be detected in 50 normal controls. After its purification from the original nucleoprotein complex, DNA plasma levels ranging from 0.15 to 12 micrograms/ml were measured, the lowest concentration detectable with our method being 0.1 microgram/ml. Knowing from recovery experiments performed with 32P-DNA that the loss of DNA during the extraction procedure is about 65%, the real concentration of DNA in the plasma corresponds to about 3 times the given figures. The purified DNA was shown to be double-stranded and composed of fractions ranging from 21 kb to less than 0.5 kb, as determined by agarose gel electrophoresis. All these fractions hybridized with a 32P-labelled human DNA probe indicating the human origin of the bulk of the circulating DNA. IN CONCLUSION: the finding of extractable amounts of DNA in the plasma of 27% of the investigated cancer patients, and its absence from the controls, suggests some correlation with malignancy.

DNA, Neoplasm↗
PubMed1984

Nude mice injected with DNA released by antigen stimulated human T lymphocytes produce specific antibodies expressing human characteristics.

Nude mice were injected with DNA purified from the nucleoprotein complex released by T lymphocytes previously exposed in vitro to inactivated herpes or poliovirus. After five days the serum of these mice was tested for its virus neutralizing activity. Results show that injected nude mice synthesize antiherpetic or antipolio antibodies depending on the antigen used to sensitize the T lymphocytes in vitro. These antibodies were not found in the serum of uninjected control mice or mice injected with inactivated herpes or polio viruses. Mice injected with DNA released by human T cells produced antibodies carrying human allotypes since they could be neutralized by anti-allotype sera. Moreover their antiviral activity was inhibited by anti-human IgM or IgG. However, the mice which were injected with DNA released by antigen stimulated murine T lymphocytes produced antiviral antibodies which were not neutralized by anti-human allotype sera.

Animals↗
PubMed1980

[Transfer of information from T and B lymphocytes during immune response: role of extracellular DNA].

Human lymphocytes obtained from donors exhibiting different allotypes were separated into B and T subpopulations and cultured in presence or in absence of UV-inactivated Herpes simplex virus. Isolated B or T cells did not produce antiherpetic activity. The B lymphocytes, cultured in presence of the supernatant collected from virus exposed T cells or in the presence of DNA extracted from this supernatant, synthesized an antiherpetic antibody carrying allotypic markers of the T cell donor.

Antibody Specificity↗
PubMed1980

The role of extracellular DNA in the transfer of information from T to B human lymphocytes in the course of an immune response.

Human lymphocytes obtained from donors exhibiting different allotypes were separated into B- and T-enriched subpopulations and cultured in the presence or absence of Herpes simplex virus inactivated by U.V. Isolated B or T cell suspensions did not produce any antiherpetic activity. The B lymphocytes cultured in the presence of the supernatant collected from virus-exposed T cells or in the presence of DNA extracted from this supernatant, synthesized an antiherpetic antibody carrying allotypic markers of the T cell donor.

Antibody Formation↗
PubMed1979

[Transfer of genetic information from T to B human lymphocytes during an immune response to herpes simplex virus].

Human blood lymphocytes carrying different allotypes were divided into B and T subpopulations and cultured in presence or in absence of ultraviolet inactivated Herpes Simplex Virus. Isolated B or T cells did not produce any antiherpetic activity. The B lymphocytes cultured in presence of 1 or 50% of the supernatant collected from virus exposed T cells synthesized on antiherpetic antibody with some allotypic markers of the T cell donor.

Antibodies, Viral↗
PubMed1979

Information carried by the DNA released by antigen-stimulated lymphocytes.

Both antigen-stimulated and non-stimulated human blood lymphocytes release in vitro a DNA-containing complex which is not the product of dying or disintegrating cells. Lymphocytes obtained from different PPD or HBs positive or negative donors were incubated with one of these antigens and the DNA released in the culture medium was tested for its information content using, successively, two cell-free systems. The ability of the resulting protein product to bind specifically to the stimulating antigen was examined by immunoadsorption chromatography. Results show that DNA excreted by stimulated lymphocytes was transcribed into an RNA which coded for an antigen-binding protein, whereas DNA released by unstimulated lymphocytes did not. The protein produced in this system, using as template the DNA released after cell stimulation, bound specifically to PPD or HBs Sepharose 4B coated columns, depending on the stimulating antigen and on the cell response to this antigen. After elution from the column the protein sedimented at 19S in a linear sucrose gradient.

Antibody Formation↗
PubMed1978

Presence of RNA in the nucleoprotein complex spontaneously released by human lymphocytes and frog auricles in culture.

Cell systems as different as normal human blood lymphocytes and frog auricles release spontaneously a nucleoprotein complex in their culture medium. This release seems to be an active mechanism that is unrelated to cell death. The presence of RNA in this complex is demonstrated. The amount of extracellular RNA is regulated by the same homeostatic mechanism that has previously been shown to govern DNA release in the same cell systems. This extracellular RNA is linked by hydrogen bonds to the extracellular DNA and cannot be extracted by a usual phenol procedure, due perhaps to the presence of a glycoprotein. Further purifications by chloroform, sodium perchlorate, and hydroxyapatite are necessary to obtain an RNA molecule that is acid precipitable, RNase and KOH sensitive, and orcinol positive. The extracellular RNA sediments between 2.5 and 4S and is not a transfer RNA. It is more highly methylated than the 28S, 18S, and 4 to 5S cellular RNA. It activates DNA synthesis in vitro.

Animals↗
PubMed1977

[Characteristics of nucleic acids excreted by non-stimulated normal human lymphocytes].

Unstimulated human blood lymphocytes have been shown to release in vitro a complex containing DNA and RNA. These nucleic acids are composed of newly synthesized material and appear to be released according to a homeostatic mechanism. Extracellular synthesis of the released DNA has been demonstrated by using a nearest neighbor analysis technique. The characteristics of the extracellular nucleic acids have been investigated biochemically and by electron microscopy.

DNA↗
PubMed1976

Spontaneous extracellular synthesis of DNA released by human blood lymphocytes.

Human lymphocytes were shown to release, in vitro and in the absence of any stimulation, a complex containing DNA. It has also been reported that the release process is unrelated to cell death and is regulated by a homeostatic mechanism. Some properties of the extracellular DNA were investigated. When a phosphorylated precursor was added to the cell-free supernatant, the DNA recovered from the medium was labeled. Evidence that DNA lebeling represented true precursor incorporation and not simple attachment was obtained from nearest neighbor analysis data. When [alpha-32P]thymidine triphosphate was added to the supernatant and the labeled DNA was completely hydrolyzed to 3'-deoxyribonucleotides, radioactivity was found in all four nucleotides. Although the exact kind of synthesis cannot be determined at this stage, the possibility of a terminal transferase system in which the enzyme would merely add a nucleotide at the end of the chain was eliminated since comparative digestion with DNase and venom phosphodiesterase showed that labeling was located along the whole length of the chain. Precursor incorporation into the DNA was inhibited by DNase, RNase, Pronase, and actinomycin D. This extracellular synthesis was not affected by cell death rate. The renaturation curve of the extracellular [3H]DNA synthesized in the cell-free medium showed a lack of gene reiteration suggesting a preferential synthesis of unique sequences.

Cell-Free System↗
PubMed1975

Spontaneous release of DNA by human blood lymphocytes as shown in an in vitro system.

Human blood lymphocytes released DNA in vitro in the absence of any stimulation. Once purified from the complex appearing in the supernatant, this DNA exhibited typical characteristics as shown by its UV absorption curve, its deoxyribose coloration, and its sensitivity to DNase. Elution patterns on hydroxyapatite columns indicated that the excreted DNA is double stranded. The released DNA was smaller than the cellular DNA; its molecular weight ranged from 3.5 x 10(5) to 3.7 x 10(6) daltons. The DNA appearing in the supernatant does not seem to be due to dead or dying cells since: (a) the same amount of DNA was found in the medium whether the incubation lasted 2 hr or as long as 16 hr; (b) cell death rate had no effect on the amount of extracellular DNA; (c) when the lymphocytes were centrifuged and placed in a new medium several times in a row, a similar amount of extracellular DNA was isolated from each of the successive supernatants, whereas if, after centrifugation, the lymphocytes were put back in their original medium, no increase in the amount of extracellular DNA was observed, suggesting an active regulatory mechanism independent of a mechanical effect; (d) it took more than 1 hr for extracellular DNA to reach its maximum concentration, a fact that also argues against a mechanical effect; (e) the specific activity of the released DNA was different from that of the cellular DNA, depending on the time of labeling; and (f) the cells that had excreted DNA kept their functional integrity, as shown by their fully maintained capacity to increase DNA synthesis after stimulation. The extracellular DNA hybridized specifically with cellular DNA. The hybridization curves indicate that the DNA excreted is highly complex, and they suggest that it is composed of part of the newly synthesized DNA. The higher specific activity of the released DNA, compared with that of the cellular DNA after a long labeling period, can be explained only by a preferential release of the newly synthesized DNA.

Cell Count↗
PubMed1973

Transcription of spontaneously released bacterial deoxyribonucleic acid in frog auricles.

After frog auricles have been in contact with a suspension of bacteria or bacteria-free supernatant fluid, newly synthesized bacterial ribonucleic acid (RNA) is recovered in animal cells. It appears that the presence of bacterial deoxyribonucleic acid (DNA)-dependent RNA polymerase is necessary for the transcription of bacterial DNA in the host cells. This phenomenon seems to be related to a transfer of DNA and DNA-dependent RNA polymerase from bacteria into animal cells.

Animals↗