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Biomedical subjects

B Strauss

Publications and source records attributed to B Strauss.

At least 127 records · Page 7Linked to original sources
PubMed1978

Production of DNA bifilarly substituted with bromodeoxyuridine in the first round of synthesis: branch migration during isolation of cellular DNA.

Incubation of human lymphoid cells with bromodeoxyuridine (BrdUrd) for short periods produces three classes of DNA containing analog: DNAHL (hybrid DNA, density approximately equal to 1.75 g/cm3), DNAint (intermediate density DNA, density approximately equal to 1.71 g/cm3), and DNAHH (DNA with both strands containing analog, density approximately equal to 1.80 g/cm3). Preparations of DNAint yield DNAHH after extensive shearing and/or treatment with single strand specific endonuclease. Cross-linking of pulse-labeled (BrdUrd + 3HdT) DNA in cells by treatment with trioxsalen and near UV light before lysis prevents the appearance of DNAHH.Cross-linking after lysis has little effect. A large fraction of DNAHH is obtained after incubation of cells with caffeine. Extraction of DNA at high salt concentration or cross-linking with trioxsalen and near UV light drastically reduced the amount of DNAHH obtained from caffeine-treated cells. We conclude that most DNAHH arises from in vitro branch migration in isolated DNA growing points.

Bromodeoxyuridine↗
PubMed1977

Intermediates in excision repair by human cells: use of S1 nuclease and benzoylated naphthoylated cellulose to reveal single-strand breaks.

Treatment of human lymphoid cells with methyl methanesulfonate (MMS) results in discontinuities in cellular DNA. Discontinuities can be detected by sedimentation through neutral sucrose gradients after digestion with S1 nuclease on top of the gradient and by benzoylated naphthoylated diethylaminoethylcellulose (BND-cellulose) chromatography. DNA with discontinuities is sensitive to shear which produces single-stranded regions and causes the DNA to adhere to BND-cellulose. The shear-sensitive and S1-sensitive sites produced by MMS treatment are probably identical. Treatment of cells with acetoxyacetylaminofluorene (AAAF) does not result in detectable discontinuities either at doses which produce the same number of adducts as observed after MMS treatment or at doses which inhibit DNA excision repair. Addition of aromatic adducts to DNA can also result in adherence to BND-cellulose but such DNA is not S1 sensitive. We conclude that MMS- and AAAF-induced damage are repaired by different pathways in human cells and that DNA with discontinuities is a readily detectable intermediate only in the repair of MMS damage by the apurinic pathway.

Acetoxyacetylaminofluorene↗
PubMed1977

Developmental decline in DNA repair in neural retina cells of chick embryos. Persistent deficiency of repair competence in a cell line derived from late embryos.

Neural retinas of 6-day-old chick embryos synthesize DNA and are able to carry out DNA excision repair. However, in contrast to the situation in human cells, the maximum rate of repair induced by N-acetoxy acetylaminofluorene (AAAF) is no greater than that induced by methyl methanesulfonate (MMS). With advancing differentiation of the retina in the embryo, cell multiplication and DNA synthesis decline and cease, and concurrently the cells lose the ability to carry out DNA excision repair. Thus, in 15-16-day embryos, in which the level of DNA synthesis is very low, DNA repair is barely detectable. If retinas from 14-day embryos are dissociated with trypsin and the cell suspension is plated in growth- promoting medium, DNA synthesis is reinitiated; however, in these cultures there is no detectable repair of MMS-induced damage, and only low levels of repair are observed after treatment with AAAF. A cell line was produced, by repeated passaging of these cultures, in which the cell population reached a steady state of DNA replication. However, the cell population remained deficient in the ability to repair MMS-induced damage. This cell line most likely predominantly comprises cells of retino-glial origin. Possible correlations between deficiency in DNA repair mechanisms in replicating cells and carcinogenesis in neural tissues are discussed.

Acetoxyacetylaminofluorene↗
PubMed1976

Increased repair in DNA growing point regions after treatment of human lymphoma cells with N-methyl-N'-nitro-N-nitrosoguanidine.

Benzoylated naphthoylated DEAE-cellulose columns can be used to separate DNA growing point regions from the bulk of the DNA. We used the columns to estimate DNA excision repair in both fractions. Repair induced by acetoxy acetyl aminofluorene (AAAF), bromomethyl benz(alpha) anthracene (BMBA), and methyl methanesulfonate (MMS) occurs to an equal extent in growing point and non-replicating regions of the DNA. Excision repair induced by methyl nitrosourea (MNNU) and methyl nitronitrosoguanidine (MNNG) occurs to a greater extent in growing point regions of the DNA. The overall amount of methyl nitronitrosoguanidine-induced alkylation is the same for replicating and non-replicating regions of the DNA treated in vitro. We conclude that there is some special interaction between methyl-nitronitrosoguanidine and the growing point region in vivo. We suppose that strand displacement and branch migration return DNA lesions at the growing point to a double stranded configuration at which repair is possible.

Cell Division↗
PubMed1976

Analysis of herpes simplex virus DNA synthesized in infected nuclei by chromatography on benzoylated naphthoylated DEAE cellulose columns.

The nature of the DNA molecules synthesized in nuclei of herpes simplex virus (HSV)-infected cells in vivo and in vitro was studied by chromatography on BND-cellulose columns after shearing to DNA fragments of 10 to 20 X 10(6) daltons. The incorporation of labelled precursors occurs in the DNA fragments containing single-stranded regions, presumably the replication forks. Prolongation of DNA synthesis leads to the accumulation of labelled DNA fragments that lack single-stranded sequences. Analysis of the isolated DNA fragments by density centrifugation in CSCl gradients revealed that most of the labelled DNA molecules are of virus specificity and the minority are cellular DNA fragments. Double-stranded virus DNA fragments and virus DNA fragments containing single-stranded sequences band in CSCl gradients at a density of 1-718 g/ml, the density of virion DNA. This suggests that the replicating HSV DNA molecules have the same density as the virion DNA and contain relatively little single-stranded DNA. The synthesis of HSV DNA molecules under in vitro conditions in isolated nuclei occurs by incorporation of the precursors into DNA fragments with single-stranded regions. The synthesis of cellular DNA in nuclei from hydroxyurea and cytosine arabinoside treated cells also occurs by elongation of nascent DNA chains.

Arginine↗
PubMed1976

DNA excision-repair deficiency of human peripheral blood lymphocytes treated with chemical carcinogens.

Human peripheral blood lymphocytes stimulated with concanavalin A for 72 hr have a 10-fold greater capacity to repair DNA damage induced by N-acetoxy-2-acetylaminofluorene than do unstimulated cells. The increased capacity of concanavalin A-activated cells to repair DNA is not observed after 24 hr in culture, a time at which stimulated cells have not begun to synthesize DNA. The maximum rate of repair synthesis obtained after treatment of stimulated cells with the "large patch"-inducing agent, N-acetoxy-2-acetylaminofluorene, is twice that obtained with methyl methanesulfonate, an agent inducing "small patch" repair. The difference between the maximum rates obtained with N-acetoxy-2-acetylaminofluorene and methyl methanesulfonate is 6-fold in a human lymphoblastoid line. Unstimulated lymphocytes show almost identical rates of repair after treatment with either N-acetoxy-2-acetylaminofluorene or methyl methanesulfonate. There is close correlation between the rate of N-acetoxy-2-acetylaminofluorene-induced repair synthesis and the loss of acetylaminofluorene adducts from DNA. Treatment of lymphocytes with methyl methanesulfonate leads to degradation of cellular DNA with the production of single-stranded regions. Such degradation is not observed with N-acetoxy-2-acetylaminofluroene. We conclude that the rate of excision repair is a function of the capacity of cells for DNA synthesis and that lymphocytes that do not synthesize DNA have a limited repair capacity and cannot be used to distinguish between large and small patch repair.

Acetoxyacetylaminofluorene↗
PubMed1975

The nature of the alkylation lesion in mammalian cells.

Methylating agents may produce as many as nine alkylated purine and pyrimidine adducts in DNA, as well as forming phosphotriesters and inducing apurinic sites and strand breaks. Although some of these products are formed in proportionately small amounts, there are sufficient sites affected in the DNA of a mammalian cell to make even the most minor product of potential biological significance. It is not possible to specify the exact reaction sites resulting in biological damage, but it is possible to quantitate the excisiion-repair of such damage both in the bulk of the DNA and at DNA growing points. Excision-repair can be measured in the bulk of the DNA by determining the specific activity of the NaCl eluate of a benzoylated naphthoylated DEAE-cellulose column of extracts of cells after treatment and incubation in the presence of hydroxyurea and labeled thymidine. The average number of nucleotides inserted per methyl methanesulfonate-induced methyl group is 0.1, per apurinic site is 9. Repair in growing-point regions after methyl methanesulfonate treatment occurs to approximately the same extent as in the bulk of the DNA.

Alkylating Agents↗
PubMed1975

The measurement of chemically-induced DNA repair synthesis in human cells by BND-cellulose chromatography.

Repair synthesis in human cells in tissue culture can be readily separated from semi-conservative DNA synthesis with the aid of a benzoylated naphthoylated DEAE cellulose (BND-cellulose) column. Cells are incubated with a radioactive DNA precursor during treatment with a repair-inducing agent. An inhibitor of semi-conservative DNA synthesis (hydroxyurea) is added to slow the progression of the DNA growing point. The cells are lysed and after treatment with ribonuclease and pronase the lysates are sheared and passed through a BND-cellulose column. Native DNA is eluted with I M NaCl. Any increase in radioactivity in the native DNA is due to repair synthesis and the specific repair activity (nucleotides inserted per mug of DNA) can be determined from radioactivity and absorbancy measurements. Repair can also be measured in the region of the DNA growing point by fractionation of the material eluted from BND-cellulose with 50% formamide. Repair was not detected in N-acetoxy-2-acetylaminofluorene (AAAF)-treated lymphoblasts derived from an individual with xeroderma pigmentosum although methyl methanesulfonate (MMS)-induced repair was observed in these cells.

Benz(a)Anthracenes↗
PubMed1975

Differences in the incorporation of bromodeoxyuridine by human lymphoblastoid cell lines.

Long term human lymphoblastoid lines differ in their ability to grow in medium containing bromodeoxyuridine (BrdU) and to incorporate analog into their DNA. Eight Burkitt's lymphoma cell lines divided at least twice in BrdU-containing medium and made DNA in which over 90% of the thymidine residues were substituted with analog in both strands. Three infectious mononucleosis-derived lines and 24 lines transformed in vitro were inhibited by BrdU after one cell division and made only hybrid DNA in which one strand was substituted with analog. One out of eight normal individuals from whom long term lines were prepared gave cell lines which divided at least twice in BrdU and gave DNA in which both strands were substituted with analog. It would appear that intrinsic cellular factors regulate the response to BrdU and that Burkitt's tumor lines are characterized by their ability to make stable doubly substituted DNA containing a high proportion of halogenated analog.

Bromodeoxyuridine↗
PubMed1974

Accumulation of an intermediate in DNA synthesis by HEp.2 cells treated with methyl methanesulfonate.

A portion of the DNA synthesized by HEp.2 cells after short incubation in the presence of BrdU bands in a CsCl gradient at a distinct peak of density 1.715-1.718 g/cm(3). Inhibition of DNA synthesis by methyl methanesulfonate results in an increased proportion of this "intermediate density" DNA. Cells labeled and subsequently chased in nonradioactive BrdU yield only hybrid DNA. Treatment with single-strand-specific deoxyribonuclease converts a portion of the intermediate density material to molecules of hybrid density (1.755 g/cm(3)). The data suggest an intermediate in DNA replication that contains a single-stranded region in the parental strand and that accumulates when DNA synthesis is blocked by an alkylation-induced lesion.

Adsorption↗
PubMed1972

Mutagen stability of alkylation-sensitive mutants of Bacillus subtilis.

A series of mutations of Bacillus subtilis, conferring sensitivity to methyl methanesulfonate (MMS), were transferred by transformation to a suppressible his(-) stock. The introduction of certain sensitivity mutations prevented the ultraviolet- or MMS-induced, but not the spontaneous, reversion of his(-) to his(+). Not all sensitivity mutations led to this resistance to mutagenesis; a strain with altered deoxyribonucleic acid (DNA) polymerase activity behaved almost normally with respect to its mutagen response, as did an excision-defective, ultraviolet-sensitive strain used as a control. One of the mutagen-stable strains responded to mutagenesis with nitrosomethylguanidine; another appeared stable even to this mutagen. All mutagen-stable strains had DNA polymerase and DNA ligase activity.

Alkanes↗