PubMed Health⌕ Search

Biomedical subjects

F A Bignone

Publications and source records attributed to F A Bignone.

13 recordsLinked to original sources
PubMed1993

Cells-gene interactions simulation on a coupled map lattice.

A discontinuous mapping, developed to model gene expression inside cells and cellular interactions on a lattice, is described. Gene dynamics (considered here only as genetic trans regulations) are formulated in a way similar to the Boolean-neural network (BN) approach through a step function, and gene products are supposed to diffuse on a regular discrete lattice of cells, giving rise to nearest neighbour--cellular automata (CA) type--interactions. The time evolution of the model is discrete and synchronous. Despite its simple form the system shows a variegate pattern of behaviour, and certain regions in parameter space show a rich series of bifurcations and multistability already in the case of networks with two genes. The patterns of distribution of the products on the lattice are similar to the ring dynamics observed in CA following Wolfram's formulation and two-dimensional (torus) dynamics described in the Greenberg-Hasting model for excitable media.

Animals↗
PubMed1990

Biotinylation of double stranded DNA after transamination.

The bisulfite catalyzed transamination of cytidine and cytosine has been reported to be single strand specific, but local thermal instabilities of the DNA double helix, coupled with the extreme sensitivity of the Biotin-Avidin revelation methods, allows the random labelling of cytosines in d.s. DNA to detectable levels for those purposes where the overall label can be very low. We have evaluated the use of this reaction to prepare double stranded DNA molecules containing N4-aminoethyl-cytosine (4-aeC). After this step 4-aeC residues can be conjugated to biotinyl-n-hydroxysuccinimide ester yielding biotinylated DNA. This reaction allows the massive production of biotinylated probes. Labelled DNA can serve as molecular weight marker and positive control in Southern-blots. Moreover it can be useful in the study of DNA-protein interaction and in the isolation of d.s. DNA-binding proteins through chromatographic procedures.

Amination↗
PubMed1989

Studies on the kinetics of expression of cell cycle dependent proto-oncogenes during mitogen-induced liver cell proliferation.

The present study was undertaken to determine the kinetics of DNA synthesis and expression of cell cycle dependent proto-oncogenes in response to two types of cell proliferative stimuli in male Wistar rat liver. The peak of DNA synthesis was approximately 24 h after a compensatory cell proliferative stimulus induced by 2/3 partial hepatectomy and approximately 36 h following a mitogenic stimulus obtained with a single dose of lead nitrate (10 micromol/100 g body wt, through femoral vein). Even though both proliferative stimuli induced the expression of c-fos, c-myc and c-Ha-ras, the extent of the increase in c-fos expression was 4- to 5-fold less in mitogen-induced cell proliferation. In addition, while the expression of c-myc, following partial hepatectomy returned to basal level by 4 h, the induced expression of c-myc persisted for up to 40 h during the lead nitrate-induced liver cell proliferation.

Animals↗
PubMed1983

G-bands without pretreatment of slides, in chemically defined conditions.

We investigated the capability of Giemsa dyes to produce G-bands without pretreatment of slides in chemically defined conditions. G-banding was produced between pH 7.0 and pH 11.0. Within this range, we observed that the achievement of G-bands was dependent on the ionic strength and time of staining. From these data and from those of other authors on other chemical variables and on the mechanisms of staining, we propose a working hypothesis of G-band formation, with a step involving shrinkage of the chromatids and rearrangement of the chromosome fiber during the staining process.

Azure Stains↗
PubMed1983

Viscometric analysis of DNA damage in kidney and lung following exposure of rats to small doses of chemical carcinogens.

A new viscometric technique has been used to detect DNA damage in kidney and lung of rats treated with six chemical carcinogens. In alkaline conditions (pH 12.5) the reduced viscosity (eta red) of kidney and lung DNA from control rats increased slowly with time reaching a maximum, (eta red)max, after 9-12 h. Carcinogens, by inducing DNA strand breaks either chemically or indirectly by excision repair or during incubation in alkali, cause a reduction of DNA supercoiling which can be sensitively measured by monitoring changes in viscosity. Computerized analysis of time-viscosity curves showed that a statistically significant reduction of the time required for eta red to reach 95% of its maximum value (t-95) was induced by the following single i.p. doses: N-nitrosodimethylamine (DMN), kidney 0.07 mg/kg, lung 0.28 mg/kg; N-nitrosodiethylamine (DEN), kidney 3.2 mg/kg, lung 12.8 mg/kg; N-nitroso-N-methylurea, kidney and lung 0.5 mg/kg; 1,2-dimethylhydrazine (DMH), kidney 1 mg/kg, lung 16 mg/kg; 4-nitroquinoline-1-oxide (NQO), kidney 2.5 mg/kg, lung 0.63 mg/kg; 2-acetylaminofluorene, kidney and lung 12.5 mg/kg. The decrease of t-95 was constantly dose-related. The comparison with data previously obtained from liver demonstrates that DMN, DEN, DMH and NQO caused the greatest amount of DNA damage in the organ most susceptible to tumor induction. Viscosity changes elicited by DMN, DEN and DMH are quantitatively well correlated with the extent of DNA alkylation.

Animals↗
PubMed1983

Viscometric detection of liver DNA fragmentation in rats treated with minimal doses of chemical carcinogens.

A new technique, using an oscillating viscometer capable of measuring changes of DNA reduced viscosity (eta red), has been used to detect DNA damage in liver of rats treated with various chemical carcinogens. In denaturing conditions (pH 12.5), the eta red of liver DNA from control rats increased slowly with time, reaching a maximum, (eta red)max, after 10 to 13 hr. Single i.p. doses of N-nitrosodimethylamine (0.07 mg/kg), N-nitrosodiethylamine (0.2 mg/kg), N-nitroso-N-methylurea (0.5 mg/kg), 1,2-dimethylhydrazine (0.06 mg/kg), procarbazine (1 mg/kg), methyl methanesulfonate (8 mg/kg), and N-diazoacetylglycine amide (3.7 mg/kg) induced a statistically significant reduction of the time (t95) required for eta red to reach its maximal value. A dose-dependent decrease of t95 was observed for dosages markedly lower than those found to be effective in eliciting DNA fragmentation by the use of alkaline elution or alkaline sucrose gradient sedimentation. 2-Acetylaminofluorene (12.5 mg/kg) and 4-nitroquinoline 1-oxide (10 mg/kg) caused a clear-cut increase of (eta red)max. 7,12-Dimethylbenz(a)anthracene (10 mg/kg) markedly prolonged t95. This viscometric assay of in vivo DNA damage allows a reliable assessment of DNA lesions induced by doses of chemical carcinogens sufficiently small not to produce significant alterations in the pharmacokinetic behavior of these compounds.

Animals↗
PubMed1982

Cytogenetic findings in 4952 prenatal diagnoses. An Italian collaborative study.

The development of prenatal diagnosis in Italy was made difficult by the restrictions of the old abortion law and only in recent years has a consistent number of cases been investigated. We report the experience on prenatal chromosome diagnosis of ten Italian centers participating in a collaborative study on 4952 diagnoses performed from 1972 to 1980. The main indication groups were: advanced maternal age (2882 cases), previous child with chromosome anomaly from parents with normal karyotype (847 cases), and chromosome anomaly in one parent (97 cases). The other indications for amniocentesis, including cases without a cytogenetic risk, have been assembled into a "miscellaneous" group (1126 cases). We found 125 abnormal fetal karyotypes (2.5%) of which 89 were unbalanced (1.8%). The frequencies and types of chromosome anomalies are reported in detail for each indication group and are compared with the corresponding one from the European Munich Conference. The great majority of these Italian data were not included in the Munich report.

Chromosome Aberrations↗
PubMed1981

[Effect of treatment with Triton X-100 on DNA integrity and DNA:RNA: protein ratio of rat liver nuclei].

A procedure is described that gives clean nuclei with intact DNA from a rat liver cell suspension. Cytoplasmic contamination is removed by successive treatments with a non ionic detergent, Triton X-100 (0.75%, v/v). We found that with ratios DNA:RNA: protein of 1:0.09:3.29 (2 Triton X-100 steps) the integrity of DNA is preserved: further decrease in RNA and protein content (3 Triton X-100 steps) causes DNA breakage, probably because of extraction of nuclear proteins. In order to estimate DNA integrity, its viscosity was determined by the use of a new oscillating crucible viscometer; this method makes possible the evaluation of extremely small levels of DNA damage as that induced by 0.067 mg/kg of DMNA injected i.p.

Animals↗
PubMed1981

[Staining with naphthol yellow S. 1. Evaluation of the Keq of the protein-dye binding reaction].

A histochemical technique, using acid dye NY-S, for quantitative determination of proteins was tested using cultured cells fixed in a fixative mixture of methanol, acetic acid, formalin (85:5:10, v/v) and stained with increasing ratios of [Dye-]/[R-HN+3] for times up to 30 min. We attempted to evaluate the Keq of the binding reaction of NY-S to proteins. Using a Microphotometer Leitz M PV 2; we have not found the saturation level. We think that this is due either to the presence of secondary binding sites between dye and proteins and stacking phenomena of the dye, or to factors affecting measurements.

Animals↗
PubMed1981

[Staining with naphthol yellow S. 2. Study of the reversibility of the protein-dye binding reaction].

In the present work we studied the reversibility of the binding reaction of Naphthol Yellow S to proteins using a Testing Automatic System Leitz. We presently think that the NY-S staining procedure, can be used as a reliable quantitative method for the determination of nuclear and cytoplasmic proteins only under standardized conditions: the ratio R = [Dye-] / [R-NH+3] must be more greater than 10; for staining periods shorter than 45 min, the slides, at equilibrium, must be mounted in dyeing solution; for quantitative determinations using irreversible bound dye, the staining period must be significantly longer than 45 min (see above) and differentiated in running water for several hours.

Animals↗
PubMed1981

[Viscosimetric evaluation of DNA fragmentation induced in vivo by alkylating agents].

A sensitive viscosimetric approach for measuring DNA single-strand breaks induced by low doses of alkylating agents is presented. The assay is based on the breaks-induced increasing rate of strand separation of rat liver DNA in alkaline solution (pH 12,5; 22 C). Because of the strong dependence of viscosity on DNA unwinding, measurement of time-course of viscosity increase can be used to detect small breakage of DNA. The kinetics of DNA denaturation has been also studied under two different alkaline conditions.

Alkylating Agents↗
PubMedDate not supplied

Biotinylation of denatured double-stranded DNA after transamination of cytidines: molecular biology applications.

Transamination at 100 degrees C of cytosines in denatured double-strand DNA is a rapid and reliable method to obtain DNA molecules containing N4-aminoethylcytosine (4aeC), which can be quantitatively conjugated to biotinyl-N-hydroxysuccinimide ester (BHS) at 37 degrees C, yielding chemically labelled probes for molecular hybridization. The adopted transamination reaction temperature allows for a ten-fold reduction of the time required for labelling at 42 degrees C, and probes obtained by this procedure are equally effective for general use in molecular biology. Dot-blots with 1-5 pg of target lambda DNA were detected by streptavidin-acid phosphatase complex after hybridization with its homologous sequences. Chemically biotinylated mouse satellite DNA has been used in combination with avidin-horseradish peroxidase to detect metaphase and interphase centromeres via in situ hybridization. Moreover probes labelled with differentially spaced linker arms were prepared by this method.

Amination↗