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S Parodi

Publications and source records attributed to S Parodi.

At least 181 records · Page 10Linked to original sources
PubMed1979

Morphometric analysis of B2cAMP induced reverse transformation in synchronized CHO cells.

Synchronized tranformed and reverse-transformed (by 10(-3) M B2cAMP) CHO-K1 cells, growing adherent to plastic, are characterized by means of geometric and densitometric parameters at the level of both the entire cell and of the nuclei at various time intervals after selective miotic detachment. Transformed and reverse-transformed cells triple-stained with Feulgen, Napthol Yellow S, and periodic acid-Schiff appeared very similar in terms of integrated optical density (IOD), related to either polysaccharides, protein, or DNA amount. On the other hand, a shift from a polygonal to a spindle-shaped morphology is a accompanied by a significant decrease in both form factor and average optical density (AOD) of intact cell and nuclei, which are the most conspicuous measured changes caused by B2cAMP, in addition to a lengthening of the cell cycle duration. In both control and treated cells, important and parallel cell-cycle-dependent modulations of geometric and densitometric parameters are also observed, for both the cytoplasmic (i.e., cell morphometry) and DNA space (i e., nuclear morphometry). Specifically, the modulation in nulear morphometry during G1, S, G2, and M phases confirms previous findings on synchronized HeLa cells. The optical density threshold-dependence of geometric parameters shows that, while becoming fusiform, the cytoplasm of reverse-transformed cells had a particularly low optical density precisely in the polar area. Utilization of such an approach in the development of an objective morphological classification of all cell lines grown as monolayers "in vitro" is also discussed.

Animals↗
PubMed1979

Relationship between cytotoxicity and induction of sister-chromatid exchanges in mouse foetal cells exposed to several doses of carcinogenic and non-carcinogenic chemicals.

The increase in sister-chromatid exchanges induced by 5 chemicals, with different DNA damaging and carcinogenic activities, was studied in short-term foetal-mouse cultures. A significant increase in SCE was induced by N-methyl-N'-nitro-N-nitrosoguanidine, N-diazoacetylglycine-amide, azaserine and methotrexate. k-Strophantin, on the contrary, was totally inactive. On a molar basis, MNNG was the most active chemical followed by MTX, AZS and DGA, in that order. At equitoxic concentrations (D37), the order of SCE-inducing abilities was MNNG, DGA, AZS and MTX. Compared with previous data, at equitoxic concentrations, the most DNA-damaging agents were also the most effective in inducing SCE. The SCE increase seems to correlate not with unspecific cytotoxicity but more with DNA damage or other damage at the genome level. MTX, a non-mutagen, which induced SCE only at toxic levels, could be considered a false positive because this positivity may reflect an enhancement of incorporation of 5-BrdUrd into DNA. The positive results obtained with AZS suggest a sufficient sensitivity of the method for detecting relatively weak carcinogens.

Animals↗
PubMed1979

DNA fragmentation in some organs of rats and mice treated with cycasin.

Cycasin (methylazoxymethanol-beta-D-glucoside) is carcinogenic in several animal species. It produces a variety of malignant tumours, mainly in the liver of mice, and in the liver, kidney and large intestine in rats. It does not appear to be mutagenic in the Ames test, even in the presence of liver microsome fraction, and it is among those carcinogens (less than 10%) ranked as "false negatives" in this test. The ability of cycasin to damage in vivo liver, kidney, lung and colonic DNA of Wistar rats and C57BL/L mice was investigated by means of alkaline elution technique. Oral single-dose administration of cycasin, in the range of 50-400 mg/kg body weight, produced in the rat a clearly evident dose-dependent DNA fragmentation in the liver, and less marked damage to DNA from kidney and colon mucosa. In mice, the same treatment produced dose-dependent DNA damage only in the liver. DNA repair up to 18 h appeared to be incomplete both in mice and rats. Methylazoxymethanol acetate is considered to be an active form of cycasin. While in vivo methylazoxymethanol acetate caused DNA damage, in vitro it appeared inactive and required metabolic activation, possibly consisting in its hydrolysis by esterase activity, to be able to cause DNA fragmentation.

Animals↗
PubMed1979

Mass action and acridine orange staining: static and flow cytofluorometry.

We present results involving an approach to acridine orange staining of intact cells based on basic physicochemical considerations. We show by static microfluorometry of several in vitro and in vivo cell lines that the important parameters for such staining are the molar ratio (Formula: see text), and molar concentration of acridine orange. Differential nuclear DNA and cytoplasmic RNA staining are totally controlled by these two parameters. We show this by a physicochemical model of cell-dye interaction. Finally, we use the method to study the growth parameters of complex in vivo cell populations by automated multiparameter flow microfluorometry. We have explored also, both by static and flow systems, the effect on AO-cell staining of various cell pretreatments such as Triton X-100 and chelating agents.

Acridine Orange↗
PubMed1978

DNA damage in liver, colon, stomach, lung and kidney of BALB/c mice treated with 1,2-dimethylhydrazine.

DNA single-strand breaks induced in various organs of BALB/c mice by treatment with a single dose of 1,2-dimethylhydrazine (DMH) were studied by means of the alkaline elution method modified in order to allow the evaluation of DNA damage in vivo with no need of radioactive prelabelling. DNA damage was detected in liver, lung, kidney, stomach and colon mucosa, with the liver showing the greatest amount of damage. Its degree was dependent on the dose and route of administration. A differential effect was evident in colon mucosa from Swiss and C57BL/6 mice which are respectively susceptible and resistant to the induction of bowel tumors by DMH. The higher degree of DNA damage found in liver in comparison with colon mucosa is consistent with the previously reported higher degree of DNA methylation, but does not correlate with the specificity of this carcinogen in inducing tumors of the large intestine in mice given repeated subcutaneous injections.

Animals↗
PubMed1978

A practical procedure for testing DNA damage in vivo, proposed for a pre-screening of chemical carcinogens.

The alkaline elution method was adapted to the evaluation of DNA damage induced in vivo through a practical and reliable microfluorometric procedure, without any need for tissue pre-labeling. The DNA damage induced in vivo by treatment with a single dose of N-nitrosodimethylamine (DMNA), N-methyl-N-nitroso-urea (MNU), 1,2-dimethylhydrazine (DMH) or cycasin has been detected in different organs of mice or rats. The results obtained are rather consistent with the organotropism of these carcinogens, and show a satisfactory dose dependent of DNA damage. DMH and cycasin, both negative in the Ames' Salmonella/microsome mutagenicity test, are clearly positive with in vivo DNA damage/alkaline elution assay. This latter method, complemented with other short-term tests, may play a useful role in the pre-screening of chemical carcinogens.

Animals↗
PubMed1977

Relationships between mutation and transformation frequencies in mammalian cells treated "in vitro" with chemical carcinogens.

An analytical quantitative comparison of data from the literature about frequencies of mutations and transformations induced by mutagenic-carcinogenic compounds in mammalian cells was carried out without any selection of unfitting data. The analysis was performed for equitoxic doses and background level. Data on transformation frequency came from 105 experiments performed with 34 carcinogenic compounds: those on mutation frequency came from 66 experiments performed with 26 mutagenic compounds; 7 compounds were assayed for both these activities. The difference in frequency between structural mutations and transformations was about 10(2)-10(3) and it appears statistically extremely significant. These results seem to indicate an absolute difference between structural mutations and transformations. In the framework of other observations it is suggested that structural alterations in a single gene are perhaps only a component of the steps present in the oncogenetic process. We may regard as "epigenetic" type phenomena the other steps involved in this process.

Animals↗
PubMed1977

Damage and repair of DNA in cultured mammalian cells with N-diazoacetylglycine amide.

N-Diazoacetylglycine amide, a diazochetoalkane, has been studied in vitro for DNA damage and repair in cells of a cloned subline from a BALB/c mouse. To our present knowledge, none of these compounds have been investigated for such activities. At nontoxic levels, a prolonged dose-dependent unscheduled DNA synthesis was observed by autoradiography. DNA damage was studied by sedimentation through alkaline sucrose gradients after the cells were lysed on the gradients. Treatment of the cells for 1 hr with nontoxic doses of N-diazoacetylglycine amide resulted in slower sedimentation of DNA. The number of single-strand breaks appeared rather linearly dose dependent for a large range of concentrations. Breaks were at their maximum after 1 hr of treatment, and no further increase in the number of breaks was seen. Some repair of the breaks probably occurs, but repair was sluggish even 68 hr after treatment. A significant part of the breaks was observed after incubation at 4 degrees in an ethylenediaminetetraacetate hypotonic solution. This seems to indicate that the compound does not require metabolic activation. Nontoxic doses of N-diazoacetylglycine amide and other similar derivatives exert mutagenic and carcinogenic activities. The presence of DNA damage and the difficulty in its repair at such doses could be related to both of these biological properties.

Azo Compounds↗
PubMed1976

Physicochemical alterations in the conformation of rat liver chromatin induced by carcinogens in vivo.

Administration of methylating carcinogens such as methyl methanesulfonate (120 mg/kg), dimethylnitrosamine (5 mg/kg), or methylnitrosourea (80 mg/kg) to rats resulted in an increased ellipticity in circular dichroism spectra and in an enhanced ability to bind ethidium bromide in the liver chromatin. Although shearing of the chromatin preparations increased both the ellipticity and number of binding sites for ethidium bromide, the carcinogen-induced effects were noticeable whether or not chromatin was sheared. Although the doses of the 3 carcinogens used in these studies are equivalent in their ability to induce strand breaks in liver DNA at 4 hr, their effects on the induction of conformational changes in liver chromatin are different. For example, methyl methanesulfonate induced the minimum conformational changes in liver chromatin at 4 hr, whereas methylnitrosourea induced the maximum changes at 4 hr. Methyl methanesulfonate and dimethylnitrosamine, on the other hand, induced maximum changes at 3 days. The conformational changes induced by methyl methanesulfonate and methylnitrosourea, and not by dimethylnitrosamine, tend to be repaired by 14 days.

Animals↗
PubMed1975

Alkaline lysis of mammalian cells for sedimentation analysis of nuclear DNA. Conformation of released DNA as monitored by physical, electron microscopic and enzymological techniques.

The degree of single strandedness of the DNA released from rat liver nuclei by various alkaline lysing solutions (including some with sodium dodecyl sulfate) was determined both before and after sedimentation in alkaline sucrose gradients employing electron microscopy, melting profiles, circular dichroism measurements, and digestibility by S1 nuclease. Regardless of the technique employed, the results obtained following alkaline sucrose gradient centrifugation of the DNA are consistent. The DNA was completely single stranded as judged by electron microscopy, circular dichroism spectra, and digestibility by S1 nuclease, an enzyme that specifically hydrolyzes single-stranded DNA. This was not true if the DNA was analyzed following alkaline lysis of the nuclei but before centrifugation. Under conditions which gave a complete transition to the single-stranded state, as judged by melting profiles and circular dichroism spectra, only 10-15% of the DNA was hydrolyzed by S1 nuclease. An increase in the susceptibility of the released DNA to S1 nuclease was observed with increases in the pH of the lysing solution. In order to release DNA which was single stranded as judged by both physical and enzymological techniques, the rat liver nuclei were lysed for 30 min with a 0.3 M NaOH lysing solution containing 0.5% dodecyl sulfate, 0.3 M NaCl and 0.03 M EDTA.

Animals↗
PubMed1975

In vivo repair of rat liver DNA damaged by 3-hydroxyxanthine.

Using alkaline and neutral sucrose gradients, it was observed that administration of the hepatocarcinogen, 3-hydroxyxanthine, to rats, resulted in the slower sedimentation of liver DNA in alkaline and neutral sucrose gradients. Slower sedimentation of liver DNA in alkaline sucrose gradients was apparent within 4 h following the administration of the carcinogen at a dose of 50 mug/g body weight. The fragmentation of liver DNA was progressive with an increase in the dose. Such fragmentation caused by a dose of 100 mug/g was largely repaired by 24 h following the administration of the carcinogen. Fragmentation and repair of liver DNA with a dose of 100 mug or more/g body weight was also seen using neutral sucrose gradients. In neutral sucrose gradients significant repair of the fragmented DNA was seen by 24 h after carcinogen. Liver DNA from rats given 3-hydroxyxanthine (100 mug/g for 4 h) or calf thymus DNA incubated in vitro with this carcinogen did not show any change in their melting profile.

Animals↗
PubMed1975

A clarification of the complex spectrum observed with the ultraviolet circular dichroism of ethidium bromide bound to DNA.

Ethidium bromide intercalation strongly effects the circular dichroism spectrum of DNA in the region of 230-300 mu, in a complex manner. In this report we present a study that quantitizes the relationships of the circular dichroism spectrum in the region of 230-300 mu and the ethidium bromide induced optical activity centered around 308 mu. We present evidence of two hidden cooperative bands that are probably the negative counterparts of the 308 mu band and 330 mu shoulder positive cooperative bands. The hidden band is quantitatively characterized. We confirm that the direct effect of ethidium bromide on the DNA spectrum is simply linearly proportional to the amount of intercalated dye. We also observe that the ethidium bromide enters freely when there is a molecule intercalated for every 3 sites, but that the intercalation is more difficult when the molecule intercalates at every second site.

Animals↗