Biomedical subjects

S Parodi

Publications and source records attributed to S Parodi.

At least 109 records · Page 6Linked to original sources

PubMed1991

Examples of uses of databases for quantitative and qualitative correlation studies between genotoxicity and carcinogenicity.

In this paper we give some examples of using databases of genotoxicity and carcinogenicity for quantitative and qualitative correlation studies between short-term tests and carcinogenicity. The quality of the databases is obviously important, but one of the major deficiencies of present databases is that they are too small. Using relatively small, different databases, different results can be obtained. With small databases it is difficult to disaggregate data for homogeneous chemical classes or other types of subsets. Using the databases of Gold (carcinogenicity) and Würgler (genotoxicity), we have investigated the carcinogenic potency of genotoxic and nongenotoxic carcinogens for different chemical classes.

Animals↗

PubMed1991

Lack of correlation between alkaline DNA fragmentation and DNA covalent binding induced by polychloroethanes after in vivo administration. Problems related to the assessment of a carcinogenic hazard.

The DNA-damaging activity of polychloroethanes was tested in mouse liver by the fluorometric assay of DNA unwinding. With the exception of 1,2-dichloroethane, all components of this chemical class had negative results. The failure of the parameter alkaline "DNA fragmentation" to detect the DNA-damaging activity of polychloroethanes is in sharp contrast with the measurement of DNA covalent binding, another short-term parameter of genotoxicity. Since covalent DNA adducts appear to be quantitatively well correlated with the oncogenic potencies of chloroethanes in liver, the negative results obtained with the present method can perhaps be explained in terms of quality of DNA adducts; these may be incapable of producing DNA breaks or alkali-labile sites detectable as alkaline DNA fragmentation. It is however worth noting that carcinogenicity of chloroethanes appears to depend not only on DNA damaging capability, but also on promoting activity during the carcinogenic process.

Alkalies↗

PubMed1991

Increased invasive, chemotactic and locomotive abilities of c-Ha-ras-transformed human breast epithelial cells.

Transfection of the immortalized human breast epithelial cells MCF-10A with the mutated ras oncogene resulted in cell transformation (MCF-10A-neoT). Since the transformed state is usually associated with enhanced migratory activity, increased capability to invade basement membranes and to grow in a three-dimensional basement membrane gel (growth in matrigel), we compared these properties in MCF-10A-neoT cells with those of MCF-10A cells transfected with either the neomycin resistance gene alone (MCF-10A-neo cells) or with the normal ras proto-oncogene (MCF-10A-neoN cells). MCF-10A-neoT cells exhibited enhanced migratory activity, as assessed by chemotaxis and chemokinesis assays. and increased capability to invade the basement membrane. These cells also formed large colonies in matrigel. MCF-10A-neo and MCF-10A-neoN cells, on the other hand, showed only marginal migratory, invasive and semisolid medium growth properties. These results indicate that the mutated ras oncogene induces in human breast epithelial cells phenotypic characteristics of malignant transformation.

Adenocarcinoma↗

PubMed1990

Mutagenic and carcinogenic potency indices and their correlation.

We have analyzed a significant number of studies existing in the literature, in which the ability of different short-term tests for predicting carcinogenicity in rodents was investigated. We have separated these studies into two groups. In the better known group of studies, qualitative predictivity was investigated (sensitivity and specificity). In the second group of studies (analyzed in greater detail), positive results were examined for the correlation between carcinogenic potency and potency of response in a given short-term test. There is substantial agreement between qualitative and quantitative predictivity; both appear to be situated between a low and moderate level. We have analyzed the interesting possibility of using the quantitative approach not only for positive data but for combined positive and negative data as well. We have stressed that short-term tests of genotoxicity should be asked to predict only initiation and irreversible alterations in the genome and not to predict a combination of these events, including promotion and modulation of differentiation. Even with regard to only initiation, genotoxicity data should be related to comparative metabolism, as well as to considerations of the significance of different end points and structure-activity relationship data. In conclusion, the information coming from short-term tests of genotoxicity is probably useful but should be used in conjunction with other types of information and only for predicting one particular class of events in the entire process of carcinogenesis.

Carcinogenicity Tests↗

PubMed1990

Intraperitoneal cytosine arabinoside administered in sequence with systemic cisplatin, doxorubicin, and cyclophosphamide in advanced ovarian cancer.

After standard management of stage III-IV ovarian cancer patients by surgical reduction of tumor mass and subsequent cisplatin-based combination chemotherapy, eradication of residual intraabdominal disease remains a major clinical problem. In an effort to increase response to therapy without adding marrow toxicity, after laparotomy, 21 stage III-IV ovarian cancer patients were treated with systemic chemotherapy comprising cisplatin, doxorubicin, and cyclophosphamide (PAC) on Day 1 followed by intraperitoneal (ip) cytosine arabinoside (Ara-C) on either Day 8 or 14, every 28 days. Ara-C, an S-phase-specific drug, was administered ip to exploit the pharmacologic advantage of an ip regimen at a time when a possible PAC-induced recruitment of cells into the proliferative pool could further maximize cell kill. Kinetic features of ovarian neoplastic cells recovered from peritoneal washings were monitored during treatment by measurement of the thymidine labeling index (TLI): data from four patients indicate that there is an increase in proliferating cells on Days 8 and 14 after PAC treatment. Toxicity of treatment was acceptable. Although 95% of evaluable patients had more than 2 cm of residual disease, response was observed in 47% of patients. The therapeutic potential of this regimen should be tested in patients with small-volume disease after debulking surgery.

Aged↗

PubMed1990

Mutagenicity in V79 cells does not correlate with carcinogenity in small rodents for 12 aromatic amines.

The aim of this investigation was to study the correlation between carcinogenicity in small rodents and mutagenic potency of aromatic amines, as measured by the induction of 6-thioguanine resistance in V79 Chinese hamster cells. It has been previously shown that the carcinogenic potency of these compounds is not correlated to their ability to induce DNA breakage, SCEs, or point mutations in bacteria, but a correlation exists with autoradiographic DNA repair test (in primary hepatocyte cultures). Twelve aromatic amines were tested and the rat liver S9 fraction was routinely incorporated in the mutation assay; mouse liver and hamster liver S9 fractions were also used as metabolizing systems. The comparison of the ranks of mutagenic and oncogenic potencies by means of the Spearman test shows no correlation between carcinogenicity and V79 cell mutagenicity of the tested aromatic amines. There was a generally low mutagenicity seen for aromatic amines in V79 cells. In some cases this could be attributed to an insufficient metabolic activation by rat S9. For example, benzidine, which was inactive when assayed in the presence of rat S9, became mutagenic when in the presence of mouse S9. On the other hand, hamster S9, which has been shown to be the best activating system for 2-acetylaminofluorene in the Ames test, did not activate this compound in V79 cells. Inadequate metabolic activation of the standard system (rat S9) used in this work could explain the low mutagenicity and the lack of correlation observed between mutagenicity and carcinogenicity. A second possibility is that point mutation is not the essential end point for the initiating activity of aromatic amines during the carcinogenic process. A third possibility is that the activity of some aromatic amines is not restricted to the initiation step in carcinogenesis. Chronic treatments with the sublethal doses often result in significant promoting activities, which could mask efficiently the initiating potential of the same chemicals.

Amines↗

PubMed1990

Negative results of short-term genotoxicity tests with 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene.

The phenobarbital-like enzyme inducer and tumor promoter of murine hepatocarcinogenesis, 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene has been assayed in short-term genotoxicity tests, i.e. the Salmonella mutagenicity test, micronucleus and chromosomal aberrations analysis in mouse bone marrow cells in vivo, DNA alkaline elution and DNA unwinding assays in mouse liver in vivo. All the assays performed proved negative.

Animals↗

PubMed1990

In vitro transformation of BALB/c 3T3 cells by 1,1,2,2-tetrachloroethane.

1,1,2,2-Tetrachloroethane (1,1,2,2-TTCE) was shown to be capable of inducing in vitro transformation of BALB/c 3T3 cells (clone A-31) either in the presence or in the absence of S9 activating system using an amplification-transformation (level-II) assay by reseeding confluent cells from each treatment and allowing additional rounds of cell replication. In the absence of metabolic activation, the highest assayed dose (1000 micrograms/ml), exerting the highest toxicity, was the only transforming dose. Lower doses of 1,1,2,2-TTCE were capable of transforming BALB/c cells in the presence of S9 activating system, the dose of 500 micrograms/ml exerting the highest transforming activity. The number and size of transformed foci recognized in the level-II plates were a function of the number of cells reseeded in the amplification assay. Foci obtained in the presence of S9 activating systems were larger in size, more deeply basophilic, and exhibited denser multilayering of constituent cells than foci recognized in the absence of exogenous metabolic activation.

Animals↗

PubMed1990

Quantitative predictability of carcinogenicity of the covalent binding index of chemicals to DNA: comparison of the in vivo and in vitro assays.

The capability of covalent binding to DNA to predict the initiating potential of chemical carcinogens was compared for the assays performed in vivo (rodent liver DNA) and in vitro (purified DNA incubated in the presence of mouse and rat liver microsomes). A quantitative correlation between DNA adducts and carcinogenic potency was investigated. The in vivo assay appeared slightly, but not significantly, more predictive than the in vitro assay. Also predictivity was slightly higher both in vivo and in vitro when we referred to liver carcinogenicity instead of overall carcinogenicity. The predictive ability found for DNA covalent binding (both in vivo and in vitro) was similar to that of many short-term tests (such as mutagenicity, DNA damage/repair, SCEs, and cell transformation tests). The covalent DNA binding, measured after incubation with DNA in vitro in the presence of liver microsomes, could therefore be a reasonable short-term test offering greater rapidity of execution and requiring the sacrifice of fewer animals than the corresponding in vivo test.

Animals↗

PubMed1990

Lack of DNA alterations induced by orotic acid in rat liver as evaluated with two DNA unwinding methods.

One percent orotic acid supplemented diet is a promoting treatment in the rat model of liver carcinogenesis. After treatment with this type of diet, DNA alterations were observed using alkaline sucrose gradients and alkaline elution methods. In this work we have utilized two unwinding methods for the detection of DNA fragmentation. One method is a viscosimetric method in which the rate of increase in DNA viscosity with time is related to the rate of alkaline DNA unwinding. The second method measures fluorimetrically the amount of renatured and denatured DNA after different times allowed for alkaline DNA unwinding. These two methods are very sensitive in detecting DNA breaks induced by typical alkylating agents, X-rays and H2O2. The two unwinding methods were clearly negative for the orotic acid supplemented diet. We suggest that the DNA alterations detected with alkaline sucrose gradients and alkaline elution methods, after promoting treatment with orotic acid, are probably different from the DNA breaks induced by typical alkylating agents, X-rays and H2O2.

Animals↗

PubMed1990

8-methoxycaffeine-induced protein-associated DNA breaks in isolated L1210 cell nuclei.

8-methoxycaffeine (8-MOC) is a caffeine derivative more potent than its parental compound in inducing chromosomal aberrations. 8-MOC has been postulated to produce chromosomal aberrations by DNA topoisomerase II inhibition. The effect of 8-MOC on nuclear DNA were studied by alkaline elution experiments and compared with those of Ellipticine and Adriamycin (ADR). Like Ellipticine and ADR, 8-MOC induced single strand breaks (SSBs), double strand breaks (DSBs), and DNA-protein cross-links (DPCs) in a bell-shaped manner with respect to drug concentration. As in the case of ADR and Ellipticine, 8-MOC induced equal SSB and DPC frequencies. These results could suggest that 8-MOC induces DNA breaks by interacting with DNA topoisomerase II or with a similar DNA metabolism enzyme.

Animals↗

PubMed1990

Effect of recombinant human TNF on human ovarian cancer cell lines.

Ovarian cancer is the second most common gynecologic malignancy. Standard therapeutic approaches to this disease, surgery followed by chemotherapy, have produced response rates of up to 80%. However, the five-year survival rate remains around 30%. Recently, Tumor Necrosis Factor (TNF) has received attention as either an alternative or an associated agent for chemotherapy of ovarian cancer. TNF is known to have direct cytotoxic and cytostatic effects on a variety of transformed cell lines "in vitro". Furthermore, TNF is known to enhance significantly the "in vitro" effects of a class of chemotherapeutic agents, specifically those targeted at DNA topoisomerase II. In this work we have investigated TNF-induced cytotoxicity in four established human epithelial ovarian cancer cell lines: A-2774; SV-626; SKOV-3 and Pa-1. TNF mediated cytotoxic activity was observed in a range of concentrations between 1 U/ml and 10-3 U/ml. A-2774 and SV-626 were the two most sensitive lines, especially when exposed to high concentrations of TNF.

Cell Survival↗

PubMed1990

Effect of vitamin A on chemotactic and chemoinvasive behaviour of an osteosarcoma cell line.

Vitamin A is known to be able to modulate cell growth and differentiation and to act as an inhibitor of the process of carcinogenesis in some experimental models. Here we have studied the effect of different concentrations of vitamin A on chemotactic and chemoinvasive behaviour of a metastatic osteosarcoma cell line. The cell proliferation was partially inhibited in the presence of 10(-5) M retinol after 4 days of incubation. Retinol effect on chemotactic and chemoinvasive activity of osteosarcoma cells seemed to be dose-dependent. The highest retinol concentration used (10(-5) M) had an inhibitory effect on migratory and invasive cell response. Lower retinol concentrations seemed to be able to enhance (10(-8) M) both chemotactic and chemoinvasive activity of osteosarcoma cells. Chemotaxis and chemoinvasion assays provide rapid and quantitative tools to study the "in vitro" behaviour of metastatic cells. Furthermore, they represent a mean to screen for drugs, hormones and other substances able to alter the metastatic phenotype.

Chemotaxis↗

PubMed1989

The problem of carcinogenic hazard evaluation for new chemicals: general considerations about the carcinogenic process.

We discuss the problem of oncogenic hazard evaluation for new chemicals. In the recent past, assessment of global carcinogenicity in rodents was considered the most significant type of information. It has recently emerged that this type of information is not adequate to distinguish initiation and genotoxicity from promotion-like effects. In this report we suggest that hazards from initiating agents and hazards from promoting agents should be treated separately. In this perspective, longterm experiments for carcinogenicity in rodents should still play an important role but a less central one. Initiation-promotion experiments in different target organs are recommended. We suggest a strategy of hazard evaluation related to the initiating potential as distinct from overall carcinogenicity. The problem of utilizing not only the qualitative component of the available information, but also the quantitative component, is considered. Finally, we discuss a possible hazard evaluation for promoting effects, but conclude that this area is very much in its infancy. Possible contributions of computer science technology to the problem of oncogenic hazard evaluation are briefly introduced.

Animals↗

PubMed1989

Structural domains and conformational changes in nuclear chromatin: a quantitative thermodynamic approach by differential scanning calorimetry.

A good deal of information on the thermodynamic properties of chromatin was derived in the last few years from optical melting experiments. The structural domains of the polynucleosomal chain, the linker, and the core particle denature as independent units. The differential scanning calorimetry profile of isolated chromatin is made up of three endotherms, at approximately 74, 90, and 107 degrees C, having an almost Gaussian shape. Previous work on this matter, however, was mainly concerned with the dependence of the transition enthalpy on external parameters, such as the ionic strength, or with the melting of nuclei from different sources. In this paper we report the structural assignment of the transitions of rat liver nuclei, observed at 58, 66, 75, 92, and 107 degrees C. They are representative of the quiescent state of the cell. The strategy adopted in this work builds on the method developed for the investigation of complex biological macromolecules. The heat absorption profile of the nucleus was related to the denaturation of isolated nuclear components; electron microscopy and electrophoretic techniques were used for their morphological and molecular characterization. The digestion of chromatin by endogenous nuclease mimics perfectly the decondensation of the higher order structure and represented the source of several misinterpretations. This point was carefully examined in order to define unambiguously the thermal profile of native nuclei. The low-temperature transitions, centered around 58 and 66 degrees C, arise from the melting of scaffolding structures and of the proteins associated with heterogeneous nuclear RNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Studies on DNA binding of caffeine and derivatives: evidence of intercalation by DNA-unwinding experiments.

Caffeine and derivatives are compounds with pleiotropic effects on the genetic material which are supposed to originate from drugs binding to DNA. Here we show, by using two different topological methods, that methylated oxypurines, at biologically relevant concentrations, unwind DNA in a fashion similar to known intercalators. Methylated oxypurines could be ranked by decreasing unwinding potency: 8-methoxycaffeine greater than 8-ethoxycaffeine greater than 8-chlorocaffeine greater than caffeine greater than theophylline. These findings confirm, with a different assay, interaction of caffeine with DNA and add additional support to an intercalative mode of binding of these drugs to DNA.

Caffeine↗

PubMed1989

DNA damage in mouse and rat liver by caprolactam and benzoin, evaluated with three different methods.

Benzoin and caprolactam were examined for their capability of inducing alkaline DNA fragmentation in mouse and rat liver DNA after treatment in vivo. Three different methods were used. With the alkaline elution technique we measured an effect presumably related to the conformation of the DNA coil. With a viscometric and a fluorometric unwinding method we measured an effect presumably related to the number of unwinding points in DNA. For both compounds only the alkaline elution technique was clearly positive. The results suggest that both caprolactam and benzoin can induce an important change in the conformation of the DNA coil without inducing true breaks in DNA.

Animals↗

PubMed1989

Results of animal studies suggest a nonlinear dose-response relationship for benzene effects.

Considering the very large industrial usage of benzene, studies in risk assessment aimed at the evaluation of carcinogenic risk at low levels of exposure are important. Animal data can offer indications about what could happen in humans and provide more diverse information than epidemiological data with respect to dose-response consideration. We have considered experiments investigating metabolism, short-term genotoxicity tests, DNA adduct formation, and carcinogenicity long-term tests. According to the different experiments, a saturation of benzene metabolism and benzene effects in terms of genotoxicity seems evident above 30 to 100 ppm. Below 30 to 60 ppm the initiating effect of benzene seems to be linear for a large interval of dosages, at least judging from DNA adduct formation. Potential lack of a promoting effect of benzene (below 10 ppm) could generate a sublinear response at nontoxic levels of exposure. This possibility was suggested by epidemiological data in humans and is not confirmed or excluded by our observations with animals.

Animals↗