Search PubMed⌕ Search

Biomedical subjects

B Malfoy

Publications and source records attributed to B Malfoy.

At least 73 records · Page 4Linked to original sources
PubMed1988

Studies on the human chromosome 3 centromere with a newly cloned alphoid DNA probe.

Starting from a chromosome-specific DNA library, we have isolated a human chromosome-specific satellite DNA sequence. This sequence of 635 base pairs (bp) consists of 3.7 alpha DNA monomers of 170-171 bp. Under high stringency it hybridizes to the centromere of chromosome 3 in a region composed of 2,750 bp tandem repeats characterized by the regular spacing of Hind III and TaqI restriction enzyme recognition sites. It has diverged and undergone amplification after the human speciation. The amplification allows an easy monitoring of the chromosome 3 centromere by in situ hybridization with a nonradioactive probe.

Animals↗
PubMed1987

Different reactivity of Z-DNA antibodies with human chromosomes modified by actinomycin D and 5-bromodeoxyuridine.

Antibodies against Z-DNA react with fixed metaphase chromosomes of man and other mammals. Indirect immunofluorescence staining shows that chromosomal segments corresponding to R- and T-bands preferentially fix Z-DNA antibodies. In this work Z-DNA antibodies were used as a probe for DNA conformation in euchromatin of fixed human chromosomes whose condensation or staining were modified by actinomycin D (AMD) and by 5-bromodeoxyuridine (BrdU). Treatments with AMD and BrdU were performed to induce a G-banding by modification of chromosomal segments corresponding to R- and T-bands. Long BrdU treatments were used to induce asymmetrical and partially undercondensed chromosomes by substitution of thymidine in one or both DNA strand. Our results show a clear difference of Z-DNA antibodies reactivity after AMD or BrdU treatment. The G-banding obtained after AMD treatment is not reversed by Z-DNA antibodies staining since these antibodies bind very weakly to the undercondensed R-bands. On the other hand, the G-banding obtained by BrdU is completely reversed giving typical R-banding, as on untreated chromosomes. For asymmetrical chromosomes an R-, T-banding pattern is always observed but there is a decrease of the fluorescence intensity proportional to the degree of BrdU incorporation. We conclude that AMD treatment greatly disturbs Z-DNA antibodies binding suggesting a change in DNA conformation, whereas BrdU treatments do not suppress but only weaken the specific binding of Z-DNA antibodies on R- and T-bands. The direct involvement of thymidine substitution in DNA sequences recognized by Z-DNA antibodies is discussed.

Antibodies↗
PubMed1986

Nucleotide sequence of an heterochromatic segment recognized by the antibodies to Z-DNA in fixed metaphase chromosomes.

The purpose of this work was to analyse at the molecular level the DNA recognized by the antibodies to Z-DNA in in situ experiments. Antibodies to Z-DNA interact strongly with R-band positive heterochromatic segments of fixed metaphase chromosomes of Cebus (Viegas-Pequignot et al., 1983). These segments are constituted of a satellite DNA the repeat unit of which is about 1520 base pairs long. The base sequence of the repeat unit has been determined. It contains a (AC)n rich region which, in vitro, adopts the Z conformation under topological constraints. Experiments with nuclei suggest that this sequence is not predominantly in the Z conformation in vivo. The polymorphic structure of the (AC)n rich region argues for an active recombination sequence.

Animals↗
PubMed1986

In situ hybridization of an acetylaminofluorene-modified probe recognized by Z-DNA antibodies in vitro.

An in situ hybridization procedure, based on the chemical modification of DNA by acetylaminofluorene (AAF), followed by a specific immunoreaction was used to localize a Z-DNA sequence isolated from the satellite DNA of Cebus appella. The AAF probe is localized on the R-band-positive heterochromatic segments of Cebus chromosomes, which strongly react with Z-DNA antibodies. The use of a nonradioactive single-stranded labeled probe confirms the reliability and the rapidity of immunochemical methods for the detection of DNA sequences on chromosomes.

2-Acetylaminofluorene↗
PubMed1984

Inner and outer complexes of Pt-coordination compounds with DNA probed by SERS spectroscopy.

Surface enhanced Raman scattering (SERS) spectroscopy has been used to study the interfacial behaviour of DNA modified by cis-Pt(NH3)2Cl2, (cis-DDP) and [Pt-(dien)Cl]Cl bidentate and monodentate platinum coordination compounds, respectively. Two stereochemical configurations of Pt-DNA complexes can be deduced from the adsorption behaviour of the Pt adducts. The antitumoral inactive [Pt-(dien)Cl] Cl forms an outer complex whereas the antitumoral active cis-DDP favours an inner complex.

Cisplatin↗
PubMed1984

Presence of Z-DNA specific antibodies in Crohn's disease, polyradiculoneuritis and amyotrophic lateral sclerosis.

Two modified polynucleotides having the Z-DNA conformation (poly [dG-dC] dien Pt and poly [dG-br5dC] . poly [dG-br5dC]) have been used for determination of antibodies to Z-DNA. Such antibodies were found in sera of patients with systemic lupus erythematosus and with Crohn's disease. They were scarcely observed in polyradiculoneuritis and in amyotrophic lateral sclerosis. In Crohn's disease sera, no antibodies to B-DNA were ever found but presence of two different families of antibodies to Z-DNA was demonstrated.

Adult↗
PubMed1983

Z-DNA immunoreactivity in fixed metaphase chromosomes of primates.

Antibodies against Z-DNA bind to fixed metaphase chromosomes of man and Cebus albifrons (Platyrrhini, Primate). By indirect immunofluorescence and indirect immunoperoxidase techniques, a heavy staining is detected in some segments of chromosomes of C. albifrons. These segments correspond to R-band-positive heterochromatin, which has a high G + C-base content. Euchromatin of human and Cebus chromosomes show a weak and heterogeneous staining that consistently reproduces an R- and T-banding pattern in both species. Because chromosome homologies previously were demonstrated between these distantly related species by chromosome banding, our results suggest that Z-DNA has been conserved during the course of primate evolution.

Animals↗
PubMed1983

Conformation of oligonucleotides and nucleic acids modified with 2-aminofluorene or 2-acetylaminofluorene.

The first part of this work deals with the thermal stability of oligonucleotides modified with acetylaminofluorene and aminofluorene, respectively. The complementary oligonucleotides d(CGCG), d(CGTACG) and d(AATTGCAATT) have been studied by ultraviolet absorption and circular dichroism. In high salt concentration and at low temperature, the three oligonucleotides form double-stranded helices which have the B-form Substitution of guanine residues in these oligonucleotides by acetylated or deacetylated aminofluorene residues destablizes the B-form and does not induce the transition to the Z-form. The second part of the work deals with the antibodies to Z-DNA. The specificity of these antibodies has been determined by radioimmunoassay. The antibodies react with the Z-form but not with the B-form. Poly(dG-dC).poly(dG-dC) modified by acetylaminofluorene residues is recognized by the antibodies. The antibodies can detect the Z-form in natural DNA as visualized by fluorescent staining of polytene chromosomes from Drosophila melanogaster.

2-Acetylaminofluorene↗
PubMed1982

Interaction between antibodies to Z-form deoxyribonucleic acid and double-stranded polynucleotides.

Antibodies to Z-DNA have been elicited in rabbits immunized with chloro(diethylenetriamine)platinum(II)chloride (Cl2dienPt) modified poly(dG-dC).poly(dG-dC). Under physiological conditions this polynucleotide in which 12% of the bases were substituted is in the Z form. The antibodies are mainly immunoglobulins G as shown by gel filtration of the antiserum and by ultracentrifugation of the antibodies purified on a Sepharose--poly(dG-dC).poly(dG-dC) column. From the quantitative precipitin curve, it is concluded that each binding site of the antibody covers four nucleotide residues. The Z-form DNA-antibody complex is stabilized by electrostatic interactions. There was no interaction between poly(dI-br5dC).poly(dI-br5dC) in the Z form and the antibodies, which strongly suggests that the exocyclic amino group of guanine residues in Z-poly(dG-dC).poly(dG-dC) interacts with the antibody binding site. The modification of poly(dG-dC).poly(dG-dC) by 2-(acetylamino)fluorene residues decreases but does not prevent the binding to the antibodies. It is also shown that the polynucleotide poly(dG-br5dC).poly(dG-br5dC) adopts the Z form over a large range of salt concentration [5 mM tris(hydroxymethyl)aminomethane hydrochloride, pH 7.5, to 3 M NaCl].

Animals↗
PubMed1982

Reactivity of B and Z-DNA towards N-acetoxy-2-acetylaminofluorene.

Poly d(G-C) d(G-C) in B-form, on one hand, and poly d(G-br5C). poly d(G-br5C) and poly d(G-m5C) . poly d(G-m5C) in Z-form, on another hand, were treated with N-AcO-[3H]AAF and the kinetics of these reactions were followed by radioactivity. Covalent binding of carcinogen to the polymers was evaluated after separation of the reacted polymers from non-reacted carcinogen by thin-layer chromatography. We found that B-form polymer reacts twice faster than the Z-form polymers. Proportions of main adducts in the three polymers are almost the same. Results are discussed in relation to the calculated electrostatic potential minima and steric accessibility at the reactive site (1, 2).

2-Acetylaminofluorene↗
PubMed1982

The B reversible Z transition of poly(dI-br5dC).poly(dI-br5dC). A quantitative description of the Z form dynamic structure.

The study of poly(dI-br5dC).poly(dI-br5dC) films by infrared spectroscopy shows that in low salt concentration, the conformation of this polynucleotide belongs to the B-family and in high salt concentration to the Z-family. 31P nuclear magnetic resonance and circular dichroism confirm the existence of these two forms. By circular dichroism and ultraviolet absorption, it is shown that the equilibrium constant of the B reversible Z transition depends upon temperature. The deuteration rates of exchangeable protons involved in hydrogen bonds between base pairs were deduced from the changes in absorbance near 1700 cm-1. In the B-form, one class of protons is measured with an exchange half-time of 20 minutes. In the Z-form, two classes of protons are measured with very different exchange half-times, the exchange half-time of the slow protons being of the order of 850 minutes. By comparison of these results with those previously obtained for poly(dG-dC).poly(dG-dC), these very slow protons of these two Z-polynucleotides are identified as the cytosine amino protons. A quantitative description of the dynamic structure of the Z-form is presented.

Circular Dichroism↗
PubMed1982

Visualization of Z sequences in form V of pBR322 by immuno-electron microscopy.

Form V DNA has been prepared from pBR322 DNA by annealing covalently closed complementary single strands. Specific rabbit antibodies to Z-DNA were shown by radioimmunoassay and electron microscopy to react with form V DNA of pBR322. The bound antibodies were visualized either directly (on synthetic polynucleotides in Z-form), or after reaction with goat anti-rabbit immunoglobulin labeled with ferritin (on form V DNA).

Antigen-Antibody Complex↗
PubMed1981

The B goes to Z transition of poly(dG-dC) . poly(dG-dC) modified by some platinum derivatives.

Poly(dG-dC) . poly(dG-dC) was modified by chlorodiethylenetriamino platinum (II) chloride, cis-dichlorodiammine platinum (II) and trans-dichlorodiammine platinum (II), respectively. The conformation of these modified poly(dG-dC) . poly(dG-dC) was studied by circular dichroism. In 4 M Na+, the circular dichroism spectra of poly(dG-dC)dien-Pt (0 less than or equal to rb less than or equal to 0.2) are similar (rb is the amount of bound platinum per base). It is concluded that the conformation of these polymers belongs to the Z-family. Dien-Pt complexes stabilize the Z-form. The midpoint of the Z goes to B transition of poly(dG-dC)dien-Pt(0.12) is at 0.2 M NaCl. Moreover another B goes to Z transition is observed at lower salt concentration (midpoint at 6 mM NaCl). In 1 mM phosphate buffer, the stability of Z-poly(dG-dC)dien-Pt(0.12) is greatly affected by the presence of small amounts of EDTA. Poly(dG-dC) . poly(dG-dC) modified by cis-Pt and trans-Pt complexes do not adopt the Z-form even in high salt concentration.

Circular Dichroism↗