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Biomedical subjects

S Parodi

Publications and source records attributed to S Parodi.

At least 91 records · Page 5Linked to original sources
PubMed1993

Lack of alachlor induced DNA damage as assayed in rodent liver by the alkaline elution test.

Alachlor was studied in vivo for its capability to induce DNA damage, as evaluated by the alkaline elution test. The experiments were performed in mouse and rat liver after acute or subacute intraperitoneal or per os administrations of the chemical at sublethal dosages. Rat liver was also studied for DNA damage after administration of 2,6-diethylaniline, one of alachlor's major metabolites. Eluted DNA from treated animals was indistinguishable from control DNA. The results show that neither alachlor nor its metabolite cause DNA damage as determined by the number of single strand breaks.

Acetamides↗
PubMed1993

Potentiation of TNF-mediated cell killing by mitoxantrone. Relationship to DNA single-strand break formation.

Tumor necrosis factor (TNF) is a pleiotropic cytokine that mediates different cellular responses including cytotoxicity, cytostasis, proliferation, differentiation and expression of specific genes. Recent studies have demonstrated that chemotherapeutic drugs that inhibit the nuclear enzyme DNA topoisomerase II synergize with TNF in tumor cell killing in vitro and in vivo. We now report that a combination of TNF and the topoisomerase II inhibitor Mitoxantrone produced dose-dependent synergistic cytotoxicity against the human ovarian cancer cell line A2774 in a clonogenic assay (1 hr treatment). This result was obtained with simultaneous administration of the drug and the cytokine under test, and is independent of modification of Mitoxantrone uptake. This combination is responsible for an evident augmentation of "cleavable complex" formation. From isolated nuclei, we have isolated also the topoisomerase II activity; we observed an increment when the cells were previously treated with TNF, 2.5 min before nuclear extraction. After 10-30 min of treatment with TNF, the topoisomerase II activity returned to normal values. If TNF is not given with but 30 min before Mitoxantrone, no potentiation of cytotoxicity or break induction is observed. These results suggest that specific timing of the association may be needed also when attempting to translate it to animals and humans.

Cell Death↗
PubMed1993

Cancer research in the European Community and other non-EC countries.

AIMS: We assessed the scientific productivity in the field of cancer research of countries in the European Community (EC) and the most important non-EC countries by counting the number of papers published during the period 1988-1990 in 15 of the top scientific journals (as defined by the Journal Citation Reports, Oncology). The global and per capita data are presented for each country. METHODS: Qualitative parameters like the impact factor and the half-life were also considered in the analysis. The selection of cancer journals with a high average quotation rate gave significant results. Introducing the average impact factor and half-life of each journal modified the results only slightly. The per capita data for each country were not corrected for the number of investigators working in oncology (a datum difficult to obtain). The parameters thus do not define the performance of the average investigator but are more "economic" parameters specifically related to the field of cancer research. RESULTS AND CONCLUSIONS: Small, wealthy Western countries tended to have an advantage over large, less developed countries, as expected. However, additional individual differences that could be of interest were present in the group of developed countries.

Canada↗
PubMed1993

Chromatin changes in cell transformation: progressive unfolding of the higher-order structure during the evolution of rat hepatocyte nodules. A differential scanning calorimetry study.

Using differential scanning calorimetry and complementary ultrastructural observations, we have characterized the status of chromatin during the transformation of rat hepatocytes in the resistant hepatocyte model of Solt and Farber (1976. Nature (Lond.). 263:701-703). Differential scanning calorimetry affords a measure of the degree of condensation of chromatin in situ and has therefore been used in this work for the purpose of establishing the nature of the structural changes associated with the emergence of successive cellular populations. Since the resistant hepatocyte model generates a series of synchronous phenotypic changes, it was possible to determine unambiguously the content of heterochromatin at each step of the process. The higher-order structure undergoes a partial relaxation in early developing nodules, isolated 16 weeks after initiation; the thermal transition at 90 degrees C, which is characteristic of noninteracting core particles, increases with respect to control hepatocytes. Dramatic changes occur in persistent (46-week) nodules. The 90 degrees C endotherm dominates the thermogram, while the transition at 107 degrees C, corresponding to the denaturation of the core particle packaged within the heterochromatic domains, disappears. The complete loss of the higher-order structure at this stage of transformation has been further verified by ultrastructural observations on thin nuclear sections. Ten-nm filaments, having a beaded appearance, are scattered throughout the nucleoplasm and clearly result from the decondensation of 30-nm-thick fibers. This catastrophic relaxation process cannot be related to an effective increase in gene activity. Rather, our observations suggest that during transformation chromatin is in a state of high transcriptional competence associated with the alert of general cellular programs. This view is consistent with the finding that in persistent nodules the DNA is extensively hypomethylated with respect to normal liver.

Animals↗
PubMed1993

Potentiation of tumour necrosis factor-mediated cell killing by VP16 on human ovarian cancer cell lines. In vitro results and clinical implications.

Synergism between recombinant human tumour necrosis factor (rHuTNF) and DNA topoisomerase II inhibitor VP16 during the killing of cells has been studied in six human ovarian cancer cell lines (A2774, A2780, SW626, IGROV-1, SKOV3, Pa1) and a cervical carcinoma cell line (Me180). Studies were performed using an assay of colony formation inhibition (drug treatment for 1 h) and a growth inhibition assay (continuous exposure for 20 h). Concomitant treatment of cells with VP16+rHuTNF enhanced cell killing in all the cell lines tested--an effect observed in both short- and long-term cytotoxicity assays. This study suggests that the activity of VP16 in ovarian cancer cell lines might be enhanced by rHuTNF in in vitro models.

Cell Survival↗
PubMed1993

Relationship between molecular connectivity and carcinogenic activity: a confirmation with a new software program based on graph theory.

For a database of 826 chemicals tested for carcinogenicity, we fragmented the structural formula of the chemicals into all possible contiguous-atom fragments with size between two and eight (nonhydrogen) atoms. The fragmentation was obtained using a new software program based on graph theory. We used 80% of the chemicals as a training set and 20% as a test set. The two sets were obtained by random sorting. From the training sets, an average (8 computer runs with independently sorted chemicals) of 315 different fragments were significantly (p < 0.125) associated with carcinogenicity or lack thereof. Even using this relatively low level of statistical significance, 23% of the molecules of the test sets lacked significant fragments. For 77% of the molecules of the test sets, we used the presence of significant fragments to predict carcinogenicity. The average level of accuracy of the predictions in the test sets was 67.5%. Chemicals containing only positive fragments were predicted with an accuracy of 78.7%. The level of accuracy was around 60% for chemicals characterized by contradictory fragments or only negative fragments. In a parallel manner, we performed eight paired runs in which carcinogenicity was attributed randomly to the molecules of the training sets. The fragments generated by these pseudo-training sets were devoid of any predictivity in the corresponding test sets. Using an independent software program, we confirmed (for the complex biological endpoint of carcinogenicity) the validity of a structure-activity relationship approach of the type proposed by Klopman and Rosenkranz with their CASE program.

Carcinogens↗
PubMed1993

Induction of chemotactic and invasive phenotype in BALB/c 3T3 cells by 1,2-dibromoethane transformation.

1,2-Dibromoethane (DBE), which can act as initiating agent, is capable of inducing a malignant phenotype in BALB/c 3T3 cells. Cells transformed with a single noncytotoxic dose formed more progressive tumors in vivo. Almost all animals (95%) receiving the inoculum of two different transformed clones developed tumors within 1 month. In the control group only 55% of the animals developed tumors after 4 months. Treatment with DBE also increased the chemotactic properties of target cells, which also acquired ability to penetrate and colonize a reconstituted basal membrane (matrigel). These data suggest that DBE could play a key role in tumor progression.

3T3 Cells↗
PubMed1993

Reversal of "atypical"-multidrug resistance by recombinant human tumor necrosis factor in the human ovarian cancer cell line A2780-DX3.

A2780 human ovarian cancer cell line and its multidrug resistant counterpart A2780-DX3 were utilized for this in vitro study. A2780-DX3 is resistant in various degrees to several topoisomerase II inhibitors but sensitive to vinca alkaloids. Simultaneous treatment of the A2780-DX3 line with 1000 U/mL rHuTNF largely reverses resistance to most topoisomerase II inhibitors. By itself, 1000 U/mL rHuTNF is not toxic to the resistant line. Uptake and retention of [3H]-Mitoxantrone are not modified by rHuTNF, whereas rHuTNF is very active in potentiating the effects of Mitoxantrone. After treatment with topoisomerase II inhibitors, Doxorubicin, Mitoxantrone, or VP16, rHuTNF restores DNA-SSB and DNA-protein cross-links in the resistant line to the level of the wild type. The cleavage activity of topoisomerase II in the resistant line is about 40% of the level present in the parental line. Five minutes after the addition of 1000 U/mL of rHuTNF, the cleavage activity in the resistant line is about 85% of the level present in the parental line. The catalytic activity of topoisomerase II is only 15% lower in the resistant line, but it is increased by about 50% 5 min after the addition of rHuTNF to the resistant line. These effects are transient and cannot be observed after 30 min. These transient direct effects of rHuTNF on topoisomerase II could be associated with its ability to restore sensitivity to inhibitors of topoisomerase II in the A2780-DX3 line.

Antineoplastic Agents↗
PubMed1992

Non-genotoxic factors in the carcinogenetic process: problems of detection and hazard evaluation.

In the classical two-stage models of carcinogenesis, initiation has been usually related to a DNA-damage/gene-mutation event, while promotion has been related to the non-genotoxic effects of clonal expansion of preneoplastic cells and/or modulation of cell differentiation. It is now clear that the process of carcinogenesis is linked to more than one irreversible alteration in the genome. Likewise, we can envisage that non-genotoxic events can take place after perhaps 0, 1, 2 or more irreversible alterations in the genome. Initiating and promoting activities of a chemical can be considered clearly separated in theory, but in practice, the chemicals we work with only rarely will be purely of the genotoxic or non-genotoxic type. We will discuss an empirical approach to classify genotoxic or prevalently non-genotoxic chemical carcinogens. For prevalently non-genotoxic carcinogens we will analyze what fraction of them can be detected as promoters of in vivo rat liver carcinogenesis. We will analyze carcinogenic potency of genotoxic and non-genotoxic carcinogens.

Animals↗
PubMed1992

Potentiation by tumor necrosis factor of mitoxantrone cytotoxicity to human ovarian cancer cell lines.

The cytotoxic activity of human recombinant tumor necrosis factor (rHuTNF) (from 0.01 to 10000 U/ml) was assayed on six human ovarian cancer cell lines and one human cervical carcinoma cell line using a crystal violet assay. rHuTNF was cytotoxic to four cell lines (A2780, A2774, SW626, PA1), while 3 cell lines (IGROV1, SKOV3, Me180) were marginally sensitive to its activity. However, under the same experimental conditions rHuTNF markedly enhanced the cytotoxicity of mitoxantrone, a chemotherapeutic drug targeted at DNA topoisomerase II, in six cell lines. The potentiation of mitoxantrone cytotoxicity was not caused by increased drug accumulation after rHuTNF treatment. No significant increase in cytotoxicity to Me180 cell line was seen when rHuTNF was added to mitoxantrone.

Drug Screening Assays, Antitumor↗
PubMed1992

Potentiation of topoisomerase I and II inhibitors cell killing by tumor necrosis factor: relationship to DNA strand breakage formation.

Recombinant human tumor necrosis factor (rHuTNF) synergistically potentiates the cytotoxicity of the topoisomerase I inhibitor camptothecin, and the topoisomerase II inhibitors epidoxorubicin, etoposide, mitoxantrone, ellipticine, actinomycin D and 4'-(9-acridinylamino)methanesulfon-m-anisidide on A2780 human ovarian cancer cell line. Similar synergy was not observed with a combination of rHuTNF and cis-platinum or mitomycin C. When A2780 cells were incubated with rHuTNF simultaneously with camptothecin or mitoxantrone or VP16, increased numbers of DNA single-strand breaks were produced. rHuTNF alone did not induce DNA strand breakage. These data provide evidence that the enhancing effect of rHuTNF is closely related to the DNA damage mediated by topoisomerase-targeted drugs. These observations may have relevance for ovarian cancer treatment.

Camptothecin↗
PubMed1992

Induction of invasive and experimental metastasis potential in BALB/c 3T3 cells by benzo(a)pyrene transformation.

A clone of BALB/c 3T3 cells (A-31), which is highly resistant to spontaneous in vitro transformation, was treated with the carcinogen benzo(a)pyrene [B(a)P]. This agent was capable of inducing in vitro transformation in the presence of S9 activating system and 6 weeks after treatment large foci were detected. Transformation frequency in solvent control groups was very low. Three foci from a single plate of two different experiments were pooled and the cells tested for their in vitro invasive properties and in vivo tumorigenic and metastatic potential. B(a)P-transformed 3T3 cells grew in soft agar and were highly tumorigenic when injected s.c. in nude mice (75% incidence within 7 weeks). Untreated cells were poorly tumorigenic (0/4 mice had tumors within 7 weeks), though they also gave rise to neoplasms after a longer latency. Spontaneous metastasis incidence was low for both controls and treated cells; however, almost all animals (15/16) injected i.v. with B(a)P-transformed cells had pulmonary nodules in the experimental metastasis assay. A few nodules in some of the animals in the control group were detected (4/16). B(a)P-transformed cells were able to invade a thin coating of matrigel in the chemoinvasion assay and also grew in matrigel showing an invasive, branching morphology. Untreated cells did not grow or invade. Our data suggest that a single treatment with a chemical carcinogen can increase tumorigenicity as well as confer invasive and experimental metastasis potential in BALB/c 3T3 cells. This work provides evidence for a role of chemical carcinogens in tumor progression.

3T3 Cells↗
PubMed1991

Thermodynamics of condensation of nuclear chromatin. A differential scanning calorimetry study of the salt-dependent structural transitions.

We present a detailed thermodynamic investigation of the conformational transitions of chromatin in calf thymus nuclei. Differential scanning calorimetry was used as the leading method, in combination with infrared spectroscopy, electron microscopy, and techniques for the molecular characterization of chromatin components. The conformational transitions were induced by changes in the counterion concentration. In this way, it was possible to discriminate between the interactions responsible for the folding of the higher order structure and for the coiling of nucleosomal DNA. Our experiments confirm that the denaturation of nuclear chromatin at physiological ionic strength occurs at the level of discrete structural domains, the linker and the core particle, and we were able to rule out that the actual denaturation pattern might be determined by dissociation of the nucleohistone complex and successive migration of free histones toward native regions, as recently suggested. The sequence of the denaturation events is (1) the conformational change of the histone complement at 66 degrees C, (2) the unstacking of the linker DNA at 74 degrees C, and (3) the unstacking of the core particle DNA, that can be observed either at 90 or at 107 degrees C, depending on the degree of condensation of chromatin. Nuclear chromatin unfolds in low-salt buffers, and can be refolded by increasing the ionic strength, in accordance with the well-known behavior of short fragments. The process is athermal, therefore showing that the stability of the higher order structure depends on electrostatic interactions. The transition between the folded conformation and the unfolded one proceeds through an intermediate condensation state, revealed by an endotherm at 101 degrees C. The analysis of the thermodynamic parameters of denaturation of the polynucleosomal chain demonstrates that the wrapping of the DNA around the histone octamer involves a large energy change. The most striking observation concerns the linker segment, which melts a few degrees below the peak temperature of naked DNA. This finding is in line with previous thermal denaturation investigations on isolated chromatin at low ionic strength, and suggests that a progressive destabilization of the linker occurs in the course of the salt-induced coiling of DNA in the nucleosome.

Animals↗
PubMed1991

Effect of recombinant human tumor necrosis factor on A2774 human ovarian cancer cell line: potentiation of mitoxantrone cytotoxicity.

Recombinant human tumor necrosis factor (rHuTNF) is a macrophage-secretory protein with antitumor activity. In vivo and in vitro cytotoxicity studies have been carried out to test the effectiveness of rHuTNF alone or in combination with chemotherapeutic agents. We have evaluated the direct cytotoxic effect of rHuTNF on a human epithelial ovarian cancer cell line in vitro (A2774), alone, or in combination with mitoxantrone (Mit), a topoisomerase II (Topo II) targeted drug. Our results not only suggest that rHuTNF is directly cytotoxic, but also that it is able to induce a very strong potentiation of Mit cytotoxicity.

Dose-Response Relationship, Drug↗
PubMed1991

Production of protein-associated DNA breaks by 8-methoxycaffeine, caffeine and 8-chlorocaffeine in isolated nuclei from L1210 cells: comparison with those produced by topoisomerase II inhibitors.

8-Methoxycaffeine (8-MOC) is a caffeine derivative, more potent than the parent compound, but very similar to caffeine in terms of induction of DNA single-strand breaks (SSBs), DNA double-strand breaks (DSBs) and DNA-protein crosslinks (DPCs). We have studied the capability of 8-MOC, caffeine and 8-chlorocaffeine (8-CC) of inducing SSBs, DSBs and DPCs, and we have compared 8-MOC with ellipticine, a typical inhibitor of DNA topoisomerase II. The DNA effects of 8-MOC appeared similar to those of ellipticine. In both cases SSBs, DSBs and DPCs were present in a similar ratio, and they were rapidly reversible after removal of the drug. The dose-response curve was bell-shaped for both compounds. In addition, 8-MOC, caffeine and 8-CC were capable of inhibiting DSBs induced by ellipticine. These results were obtained at the level of L1210 cell nuclei. In spite of these functional similarities, 8-MOC, caffeine and 8-CC were unable to stimulate the formation of a cleavable complex by purified L1210 topoisomerase II (p170 form) when SV40 DNA and human c-myc DNA were used as substrate. These methylated oxypurines could be active on a different form of topoisomerase II, or, alternatively, they could be active only in the natural chromatin 'milieu' within the nucleus.

Animals↗
PubMed1991

Are genotoxic carcinogens more potent than nongenotoxic carcinogens?

In this report we have raised the question whether genotoxic carcinogens are more potent than nongenotoxic carcinogens when studied in long-term carcinogenicity assays in rodents. To build a large database of compounds for which both carcinogenicity and genotoxicity had been investigated, we have used a database produced by Gold and co-workers for carcinogenic potency data (975 chemicals) and a database produced by Würgler for genotoxicity data (2834 chemicals). Considering compounds positive or negative in at least three short-term tests and in at least 75% of available tests, we could define 67 genotoxic carcinogens and 46 nongenotoxic carcinogens. Carcinogenic potency of genotoxic carcinogens was about 50 times higher than carcinogenic potency of nongenotoxic carcinogens. Our results are different from the results of Tennant et al.; their database (24 genotoxic carcinogens and 12 nongenotoxic carcinogens compatible with our definition) seems to suggest that there is practically no difference in potency between genotoxic and nongenotoxic carcinogens. The two databases have only four compounds in common and are also different in terms of number of elements for different chemical classes. Nitrosocompounds, nitrogen mustards, hydrazine derivatives, and polycyclic aromatic hydrocarbons are not represented in the database of Tennant. The overall impression from our analysis is that the usefulness of short-term tests of genotoxicity could be significantly better than what has been suggested by the previous work of Tennant et al. because these tests tend to detect, at least for many important chemical classes, the most potent carcinogens. This consideration may not be valid for certain classes of chemicals.

Animals↗
PubMed1991

Analysis and comparison of information and data recorded in carcinogenicity and genotoxicity databases.

The Interlab Project is a university-industry joint project recently funded by the Italian government as part of the improvement of the Italian research infrastructure; among its short-term goals are the implementation of data banks of biomedical interest and the spread of informatic tools for biomedical research. Results of both long-term assays of carcinogenicity in rodents and short-term in vitro and in vivo tests of genotoxicity are relevant for a wide body of users, ranging from carcinogenesis research laboratories to industries and governmental agencies. To evaluate the most appropriate ways of spreading information on these experiments, a detailed analysis on information recorded in available databases has been carried out. Furthermore, the contents of the most known databases have been compared, with respect to a specific compound, to evaluate both the overall reliability of these systems, compared to longer and more complex assessments carried out manually starting from bibliographic searches, and the level of concordance among them.

Academies and Institutes↗