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Biomedical subjects

P Colson

Publications and source records attributed to P Colson.

At least 91 records · Page 5Linked to original sources
PubMed1995

Use of electric linear dichroism and competition experiments with intercalating drugs to investigate the mode of binding of Hoechst 33258, berenil and DAPI to GC sequences.

The drugs Hoechst 33258, berenil and DAPI bind preferentially to the minor groove of AT sequences in DNA. Despite a strong selectivity for AT sites, they can interact with GC sequences by a mechanism which remains so far controversial. The 2-amino group of guanosine represents a steric hindrance to the entry of the drugs in the minor groove of GC sequences. Intercalation and major groove binding to GC sites of GC-rich DNA and polynucleotides have been proposed for these drugs. To investigate further the mode of binding of Hoechst 33258, berenil and DAPI to GC sequences, we studied by electric linear dichroism the mutual interference in the DNA binding reaction between these compounds and a classical intercalator, proflavine, or a DNA-threading intercalating drug, the amsacrine-4-carboxamide derivative SN16713. The results of the competition experiments show that the two acridine intercalators markedly affect the binding of Hoechst 33258, berenil and DAPI to GC polynucleotides but not to DNA containing AT/GC mixed sequences such as calf thymus DNA. Proflavine and SN16713 exert dissimilar effects on the binding of Hoechst 33258, berenil and DAPI to GC sites. The structural changes in DNA induced upon intercalation of the acridine drugs into GC sites are not identically perceived by the test compounds. The electric linear dichroism data support the hypothesis that Hoechst 33258, berenil and DAPI interact with GC sites via a non-classical intercalation process.

Base Sequence↗
PubMed1995

Epidemiology and laboratory diagnosis of hantavirus (HTV) infections.

Hantavirus (HTV) is recently discovered "hemorrhagic fever virus" belonging to the Bunyaviridae family, which is spread throughout the world by wild rodents and/or laboratory rats. During an epidemic in the Belgian-French Ardennes in 1993, more than 200 acute cases were recorded of the milder European form of HTV-illness, otherwise known as Nephropathia epidemica (NE). This variant may be recognized by the sudden onset of fever, acute renal failure, thrombocytopenia and sometimes by ophthalmologic complications. The symptomatology is rather aspecific and diagnosis can only be confirmed by serologic tests, of which the best option nowadays seems to be: screening by IgG EIA, followed by IgM confirmation with a mu-capture EIA test. Some of the tests described allow an evaluation of the causative serotype or even the moment of infection. Next to the "classic" serologic assays for detection of specific viral antibodies, we describe briefly our own experience with newer tests such as "high density particle agglutination" and "line immuno assay". Polymerase chain reaction for viral RNA genome typing and immunohistochemical colouring of the viral antigen in tissues seem to offer promising alternatives for the immediate future.

Belgium↗
PubMed1995

[Epidemic of hantavirus disease in Entre-Sambre-et-Meuse: year 1992-1993. Clinical and biological aspects].

A multihospital study allowed us to follow a total of 62 serologically proven cases of Nephropathia epidemica (NE) in the Belgian region between Sambre and Meuse during the 1992-1993 period. The clinical picture consisted of sudden high fever (100% of the cases), headache (71%), abdominal or lumbar pains (80%) and, as a less frequent but very specific sign, acute myopia (24%). Non-specific respiratory symptoms such as a non-productive cough and an abnormal lung auscultation were found in 1 case out of 4. Frequent laboratory anomalies were thrombocytopenia (69%), left-shift leucocytosis (77%), abnormal LDH (69%) and an inflammatory syndrome (86%) with levels of C-reactive protein (CRP) elevated up to a mean of 102 mg/L, often accompanied by a marked fall of total serum cholesterol and a rise of triglycerides. Impaired kidney function is the rule (84%), nevertheless serum creatinine levels remain inferior to 150 mumol/L (1.7 mg%) in 25% of the patients. As for neurological signs, 1 case of encephalitis and 1 syndrome of Guillain-Barré were observed. Relative bradycardia (< 90 bpm) was noted in 50% of the cases with fever, whereas Doppler-echocardiography detected pericarditis in 1 case, and transient impairment of the left ventricle function in 3 cases. Frequent elevation of liver enzymes (46%) confirms the observation that from now on, Hantavirus infections should be considered in the differential diagnosis of viral hepatitis. One severe case was observed with shock, diffuse intravascular coagulation and adult respiratory distress syndrome (ARDS), followed by 5 other patients presenting with marked degrees of hypoxemia and hypocapnia. We conclude that not only the causative Hantaviral serotype, but also the degree of "systemic inflammatory response syndrome" (SIRS) seems to determine the clinical picture in Hantavirus infections.

Adolescent↗
PubMed1995

Increased production of nitric oxide in patients infected with the European variant of hantavirus.

Serum nitrate levels, a measure of nitric oxide (NO) production in vivo, were very high (95 +/- 14 microM) in 13 patients infected with Puumala virus, the European variant of Hantavirus (HTV), as compared to those in healthy subjects (33 +/- 3 microM). Serum nitrate levels showed a high and significant correlation with scores on the Acute Physiological And Chronic Health Evaluation (APACHE II) scale and with serum creatinine, and an inverse correlation with platelet counts. Serial serum measurements of nitrate in 2 severe cases showed very high levels at the onset of arterial hypotension and acute renal failure. We conclude that excessive amounts of NO are produced in patients infected with Puumala virus and that this reactive nitrogen intermediate could play an important role in the pathogenesis of the disease.

Acute Disease↗
PubMed1995

Design of composite drug molecules: mutual effects on binding to DNA of an intercalator, amsacrine, and a minor groove binder, netropsin.

A variety of spectroscopic and biochemical techniques have been employed to investigate the extent to which binding to DNA of an intercalator (amsacrine or its 4-carboxamide derivative SN16713) affects the binding of netropsin, a minor groove-targeted ligand, and vice versa. In general, rather little mutual interference has been found and the binding of one drug is compatible with binding of the other. The anilinoacridines exert little or no effect on the positioning of netropsin in the minor groove, judged by circular dichroism spectroscopy and electric linear dichroism, whereas netropsin has a perceptible effect on the intercalative binding of amsacrine, but not that of SN16713. Neither acridine drug prevents the netropsin-induced Z-->B structure reversion observed with poly(dG-dC).poly(dG-dC) in buffer containing 60% ethanol. The kinetics of dissociation of any one drug from its DNA complex are affected little, if at all, by the simultaneous presence of the other. Footprinting experiments with the several drugs singly or in combination reveal a certain amount of mutual interference, but the selective recognition of AT-rich sequences by netropsin tends to dominate the recognition pattern and is largely maintained in the presence of a considerable excess of amsacrine or its 4-carboxamide derivative.

Amsacrine↗
PubMed1995

Influence of the methyl substituents of a thiazole-containing lexitropsin on the mode of binding to DNA.

We have studied the DNA-binding properties of two thiazole-containing analogues of netropsin which differ by the absence (Thia-Nt) or presence (Methia-Nt) of methyl groups on the thiazole rings. The mode of binding to DNA of the two lexitropsins was investigated by circular dichroism, electric linear dichroism and viscosity measurements. The spectroscopic and hydrodynamic results indicate that the non-methylated lexitropsin binds to the minor groove of DNA, whereas the methylated analogue behaves as an intercalator. Our findings led to the notion that the methyl substituents on the thiazole rings might play a significant part in the intercalation process.

Animals↗
PubMed1995

Binding to DNA and cytotoxic evaluation of ascididemin, the major alkaloid from the Mediterranean ascidian Cystodytes dellechiajei.

The isolation of ascididemin from the Mediterranean ascidian Cystodytes dellechiajei is described. This alkaloid consists of a planar pentacyclic chromophore which was investigated for its DNA-binding and cytotoxic properties. Spectroscopic measurements provided evidence that the drug intercalates into DNA. DNase I footprinting assays indicated that the binding of ascididemin to GC-rich sequences is favoured over binding to AT-rich and mixed sequences. Chemical probes were used to detect ligand-induced structural changes in DNA. The alkaloid induces a hyper-reactivity of the DNA towards potassium permanganate, but not towards diethylpyrocarbonate, just as is the case with ethidium bromide; it has little effect on the catalytic activities of topoisomerases I and II. Ascididemin exhibits marked cytotoxicity towards human leukaemic cells in vitro and appears to be practically equally toxic for drug-sensitive and multidrug-resistant cell lines. The results suggest that DNA, but not topoisomerases, may represent the critical cellular target at which this marine alkaloid exhibits its potent cytotoxic properties in vitro.

Alkaloids↗
PubMed1994

Reaction of a biscationic distamycin-ellipticine hybrid ligand with DNA. Mode and sequence specificity of binding.

Molecular modeling of complexes between the octanucleotide d(CGATATCG)2 and either a monocationic or biscationic distamycin-ellipticine hybrid molecule predicted that the extra positive charge on the latter conjugate ligand should ensure tight fitting into the minor groove of the duplex without affecting intercalation of the ellipticine chromophore. To test this prediction, we have synthesized a biscationic compound Distel (2+) and investigated its interaction with DNA using various optical and gel electrophoresis techniques. Viscosity, fluorescence lifetime, and circular and linear dichroism measurements bear out the validity of the calculations and show that Distel (2+) does indeed come to lie with its distamycin moiety in the minor groove of DNA and its ellipticine ring intercalated nearby. Linear dichroism experiments with a range of polynucleotides indicate that, unlike its monocationic homologue, the biscationic ligand engages in bidentate binding to AT sequences but not to GC sequences. Footprinting studies employing DNase I and methidiumpropyl-EDTA.FeII as DNA cleaving agents reveal that the biscationic hybrid is notably selective for AT-rich sequences in DNA. The concentrations required to detect a clear footprint at AT sites with Distel (2+) are 4- to 10-fold lower than those required to produce comparable DNase I footprints with distamycin alone. Also, in accord with the energy-minimized model of the hybrid-oligonucleotide complex, chemical probing experiments using diethyl pyrocarbonate and osmium tetroxide reveal that the hybrid causes significant distortion of the DNA helix, explicable in terms of bending of the duplex toward the minor groove, which greatly enhances the reactivity toward probes in the major groove of the DNA. The experimental results help to identify the determinant factors, predominantly steric and electrostatic interactions, which shape the DNA-binding reaction. Thus, molecular modeling has correctly predicted the DNA-binding properties of a doubly charged ligand and shown that appending an auxiliary basic group onto the distamycin moiety was the right way to proceed in order to convert a nonspecific conjugate into a highly specific DNA reader.

Animals↗
PubMed1994

Stimulation of site-specific topoisomerase II-mediated DNA cleavage by an N-methylpyrrolecarboxamide-anilinoacridine conjugate: relation to DNA binding.

The DNA binding properties and effects on topoisomerase II of MePyGA, an anilinoacridine derivative bearing an N-methylpyrrolecarboxamide unit at position 1', have been compared with those of its precursor glycylanilinoacridine and the structurally related antileukaemic drug amsacrine. Electric linear dichroism spectroscopy reveals that MePyGA intercalates its acridine chromophore between DNA base pairs with a preference for GC-rich sequences, whereas both its structural analogue lacking the N-methylpyrrole unit and amsacrine intercalate into DNA without any strong sequence preference. The effects of the test drug on the catalytic activities of topoisomerase II were studied in vitro using purified calf thymus enzyme and 32P-labeled DNA. MePyGA stabilizes the topoisomerase II-DNA covalent complex and stimulates the cutting of DNA at a subset of preexisting topoisomerase II cleavage sites. The removal of the N-methylpyrrole unit abolishes both the GC-preferential binding to DNA and the topoisomerase II-mediated DNA cleavage. MePyGA and amsacrine stimulate the cleavage of DNA by topoisomerase II at different places: cleavage stimulated by amsacrine is consistent with the expected adenine requirement at position +1 whereas the predominant sites of DNA cleavage stimulated by MePyGA contain a cytosine at position +/- 1. This is the first instance where an anilinoacridine derivative differing only by the nature of the substituent at position 1' has been found to affect the catalytic activity of topoisomerase II differently. The spectroscopic and biochemical data lead to the conclusion that two functional domains can be identified in MePyGA: its anilino group can be regarded as a skeletal core to which are connected (i) the tricyclic acridine moiety which represents the DNA-binding domain and (ii) the N-methylpyrrole moiety which constitutes the topoisomerase II-targeted domain. The structure of the substituent at position 1' of the anilinoacridine chromophore evidently determines the location of the sites of DNA cleavage by topoisomerase II. These findings provide guidance for the synthesis and development of new topoisomerase II-targeted antitumor anilinoacridine derivatives.

Acridines↗
PubMed1994

A preliminary cost effectiveness analysis of an intervention to reduce homelessness among the mentally ill.

The Critical Time Intervention Project is a three-year clinical trial which tests a time-limited, supportive intervention to reduce recurrent homelessness among mentally ill men moving from a shelter to the community. Along with a comparison of nights spent homeless and other outcomes, the evaluation of the Critical Time Intervention includes a comparison of the relative costs of the intervention, compared to usual treatment. Such cost effectiveness analyses are difficult to perform and are rarely applied to mental health treatments. This paper presents the general scheme of this analysis and discusses critical issues in the construction and measurement of cost variables. Preliminary results which have implications for the cost analysis are presented.

Activities of Daily Living↗
PubMed1994

Interaction of two peptide-acridine conjugates containing the SPKK peptide motif with DNA and chromatin.

The interaction between DNA and two peptide-acridine conjugates containing one (1) or two (2) moieties of the Ser-Pro-Lys-Lys (SPKK) minor groove-binding peptide motif has been studied by a combination of hydrodynamic, biochemical and spectroscopic methods including diffusion-enhanced luminescence energy transfer (DELET) measurements with a Tb(III) lanthanide chelate as donor. Viscometric titrations do not reveal any significant difference between the two hybrid molecules which both unwind (by about 15 degrees) and extend the DNA similarly. DELET measurements show that the acridinyl chromophore of compounds 1 and 2 is much more accessible than that of a simple monointercalating drug such as acridine orange or ethidium. The accessibility factor increases proportionally with the peptide length, reflecting the extent of perturbation imposed upon the intercalating chromophore by the binding to DNA of the peptide moiety of the hybrids. Experiments with the osmium tetroxide-bispyridine reagent indicate that the two hybrid compounds both affect the local conformation of DNA rendering certain thymine residues conspicuously accessible to the probe. The drug-induced sites of hyperreactivity towards OsO4 in DNA are very similar with the exception of a short run of three T residues which is attacked more strongly in the presence of tetrapeptide-acridine conjugate 1 than with the octapeptide-acridine conjugate 2. These results are fully in agreement with previous footprinting studies and support the view that a minimum of two SPKK motifs is required to mimic the AT-specific minor groove binding antibiotic netropsin. On the basis of the DNA-binding properties of these two peptide-acridine hybrids, we present DNA-binding models in which the acridinyl moiety of compound 1 protrudes slightly outside the double helix but remains more or less parallel to the plane of the base-pairs. In contrast, with compound 2, where the octapeptide SPKKSPKK is bound to the minor groove, we postulate that the chromophore lies only partially overlapped with the base pairs in the intercalation site and, in addition, the heterocyclic chromophore is significantly tilted with respect to the double helix axis. Electric linear dichroism and DELET measurements with chromatin reveal that the presence of histone proteins affects the intercalative binding of compound 2 while it has practically no effect on the binding of compound 1.

Acridines↗
PubMed1994

Mode of DNA binding of bis-benzimidazoles and related structures studied by electric linear dichroism.

The binding mode of a series of bis-benzimidazole analogues of Hoechst 33258 to a variety of DNAs and polynucleotides has been investigated by electric linear dichroism. Two groups of compounds were examined: (i) benzoxazole and pyridoimidazole derivatives and (ii) pyridoimidazole analogs substituted with an N-alkoxyalkyl group either directed towards the minor groove or directed away from the minor groove. The ELD data indicate that the mode of binding of these drugs varies significantly with the sequence of the target DNA sequence. The DNA binding properties of these drugs are related to their topoisomerase inhibitory properties.

Base Sequence↗
PubMed1994

Psoralen--lexitropsin hybrids: DNA sequence selectivity of photoinduced cross-linking from MPE footprinting and exonuclease III stop assay, and mode of binding from electric linear dichroism.

The properties of certain hybrids 3 and 5 bearing a photoactivatable psoralen group attached to DNA sequence recognizing lexitropsin carriers have been examined. The hybrids bind to poly(dA-dT) with Kapp of 2.8 and 0.9 x 10(7) M-1, i.e. greater than or equal to that of netropsin (Kapp = 1.0 x 10(7) M-1), indicating that the psoralen moiety may contribute to binding in the case of 5. Photoinduced cross-linking of DNA by 3 and 5, while efficient, is less so than that of individual psoralens and reaches a maximum at a ligand to DNA base pair ratio (r) of 0.2. Complementary strand methidium-propyl-EDTA (MPE).Fe(II) footprinting demonstrated that, in the dark, the sequence preferential recognition of hybrids 3 and 5 is dominated by the lexitropsin moiety. Examination of 360 nm photoinduced DNA cross-linking by the hybrids 3 and 5 was carried out using an exonuclease III stop assay. This revealed that > 95% of the DNA remained double stranded, indicating that 3 and 5 generate primarily biadducts at AT-rich sequences. This assay also located individual monoadduct sites, some of which are remote from the dominant cross-linked sites. When the samples were exposed to 254 nm UV light before loading onto the gel to reverse the photoproducts, the pattern of the exonuclease III stop bands was not altered significantly compared with the experiment without 254 nm irradiation. It is concluded that these termination sites include both mono- and biadducts. Electric linear dichroism examination of the DNA complexes of hybrids 3 and 5 (without light activation) provides evidence that the lexitropsin portion binds in the minor groove, while the psoralen portion intercalates in a suitably located site for subsequent photoinduced cross-linking.

Antineoplastic Agents↗
PubMed1994

[B. Roquefeuil].

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Anesthesiology↗
PubMed1993

The different binding modes of Hoechst 33258 to DNA studied by electric linear dichroism.

The binding mode of the bisbenzimidazole derivative Hoechst 33258 to a series of DNAs and polynucleotides has been investigated by electric linear dichroism. Positive reduced dichroisms were measured for the poly(dA-dT).poly(dA-dT)- and poly(dA).poly(dT)-Hoechst complexes in agreement with a deep penetration of the drug into the minor groove. Similarly, the drug displays positive reduced dichroism in the presence of the DNAs from calf thymus, Clostridium perfringens and Coliphage T4. Conversely, negative reduced dichroisms were obtained when Hoechst 33258 was bound to poly(dG-dC).poly(dG-dC), poly(dA-dC).poly(dG-dT) and poly(dG).poly(dC) as well as with the GC-rich DNA from Micrococcus lysodeikticus indicating that in this case minor groove binding cannot occur. Substitution of guanosines for inosines induces a reversal of the reduced dichroism from negative to positive. Therefore, as anticipated it is the 2-amino group of guanines protruding in this groove which prevents Hoechst 33258 from getting access to the minor groove of GC sequences. The ELD data obtained with the GC-rich biopolymers are consistent with an intercalative binding. Competition experiments performed with the intercalating drug proflavine lend credence to the involvement of an intercalative binding rather than to an external or major groove binding of Hoechst 33258 at GC sequences.

Animals↗