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H Bacha

Publications and source records attributed to H Bacha.

At least 19 recordsLinked to original sources
PubMed2006

Cytotoxicity and related effects of T-2 toxin on cultured Vero cells.

T-2 toxin belongs to a group of mycotoxins synthesized by Fusarium fungi that are widely encountered as natural contaminants of certain important agricultural commodities particularly, cereals. Upon exposure, T-2 toxin causes severe human and animal diseases. It is considered to be a major causative agent in fatal alimentary toxic aleukia (ATA) in humans. In this study, cytotoxicity and apotosis induction by T-2 toxin was investigated in vitro on Vero cell line using the MTT and the neutral red viability assays, the induction of lipid peroxidation, the decrease of macromolecule levels (protein, DNA and RNA), DNA fragmentation and caspase-3-dependent apoptosis induction. Our results showed that T-2 toxin reduced cell viability correlated to an impairment of macromolecule levels. It also increased MDA formation, induced DNA fragmentation showed by DNA laddering patterns on agarose gel electrophoresis. This fragmentation is in relation with apoptosis induction which was confirmed by activation of caspase-3, and depletion of the mitochondrial membrane potential reflecting a mitochondrial dysfunction.

Animals↗
PubMed2005

Zearalenone induces chromosome aberrations in mouse bone marrow: preventive effect of 17beta-estradiol, progesterone and Vitamin E.

The cytogenetic effect of zearalenone (ZEN), a non-steroidal estrogenic mycotoxin, was evaluated in vivo, in mouse bone marrow cells, by assessing the percentage of cells bearing different chromosome aberrations. The studies included different conditions for animal treatment, as follows: (1) single intraperitoneal (ip) injection, (2) repeated ip injections, (3) pre-treatment for 24h with Vitamin E (Vit E), and (4) pre-treatment for 4h with 17beta-estradiol (17beta-Est) or progesterone (Prog). ZEN induced different types of chromosome aberrations, which was concentration-dependent (2-20 mg/kg bw). These doses corresponded to 0.4-4% of the LD50 in the mouse. Interestingly, when the dose of ZEN (40 mg/kg) was fractionated into four equivalent doses (4 x 10 mg/kg bw), into three doses (15 + 10 + 15 mg/kg bw), or into two equivalent doses (2 x 20 mg/kg bw), given every 24 h, the percentage of chromosome aberrations increased significantly. This finding suggests that ZEN proceeds by reversible binding on receptors that could become saturated, and that it damages the chromosomes in a 'hit and go' manner. Furthermore, pre-treatment of animals with 17beta-estradiol or progesterone significantly decreased the percentage of chromosome aberrations, suggesting that (i) these hormones bind to the same cytoplasmic receptors transported into the nucleus to elicit DNA damage, (ii) they may play a role in preventing chromosome aberrations induced by ZEN. Similarly, Vit E prevented these chromosome aberrations indicating that Vit E, previously reported to prevent most of the toxic effects induced by ZEN, may also bind to the same receptors.

Animals↗
PubMed2004

Cytotoxicity, inhibition of DNA and protein syntheses and oxidative damage in cultured cells exposed to zearalenone.

Mycotoxins are toxic metabolites of various fungi commonly found in feed and foodstuff and can cause very serious health problems in animals as well as in humans. Zearalenone (ZEN), a mycotoxin produced by various Fusarium species has several adverse effects. Indeed, ZEN has strong estrogenic activity associated with hyperestrogenism and several physiological alterations of the reproductive tract. Moreover, ZEN was shown to be hepatotoxic, haematotoxic, immunotoxic and genotoxic. The exact mechanism of ZEN toxicity is not completely established. The observed strong estrogenic effect of ZEN resulting from its competition with 17beta-estradiol in the binding to estrogen receptors is generally considered to underline most toxic effects of ZEN, but estrogenic activity alone cannot explain the diverse and apparent adverse effects. The objective of the present study was to determine the involvement of other possible mechanisms in ZEN induced toxicity. Cytotoxicity, cell cycle perturbation, inhibition of protein and DNA synthesis as well as the presumed later marker of oxidative stress, malondialdehyde, were monitored in Vero and Caco-2 cells exposed to ZEN. Our results showed that ZEN reduces cell viability correlated to cell cycle perturbation, inhibits protein and DNA syntheses and increases MDA formation in both cell lines in concentration-dependant manner. We assumed that cytotoxicity and oxidative damage are additional mechanisms of ZEN mediated toxicity.

Animals↗
PubMed1999

Karyomegaly of tubular cells as early stage marker of the nephrotoxicity induced by ochratoxin A in rats.

Cases of karyomegaly were described by Sclare and by Mihatch in patients affected with tubular-interstitial nephropathy. The Karyomegalic cells showed enlarged nuclei with accumulation of genetic material. No aetiology was suggested. Our study of rats experimentally intoxicated by ochratoxin A, a well-known nephrotoxic compound, indicates the presence of karyomegaly with alteration of the tubular tissue. In control animals no karyomegalic cells were detected. These observations suggest that karyomegaly with megacytosis may be caused by the nephrotoxic ochratoxin A in the kidney. In addition abnormal mitosis together with karyomegalic cells were observed at an earlier stage of the intoxication (30 days) suggesting possible regeneration if the OTA insults are stopped. After 90 days of treatment, the degeneration increased and only karyomegalic and apoptotic-like cells were observed indicating that the regeneration no longer occurs and that the degeneration becomes irreversible.

Animals↗
PubMed1998

Induction of a SOS repair system in lysogenic bacteria by zearalenone and its prevention by vitamin E.

Zearalenone (Zen) is an oestrogenic mycotoxin produced by several Fusarium species in cereals. It induces modifications of haematological parameters in rats with cytotoxicity and inhibition of macromolecular synthesis (nucleic acids and protein). Zen and its metabolites have oestrogenic and anabolic activities and interact with human oestrogen receptors. Zen and its metabolites showed a positive DNA damaging effect in recombination tests with Bacillus subtilis. It induces sister chromatid exchange and chromosomal aberration in CHO cells. Zen was found to be capable of inducing DNA-adduct formation in mouse liver. The genotoxicity of Zen was questionable until the last decade when increasing data tended to show this toxin to be genotoxic in vivo. However the mechanism of its genotoxicity and mutagenicity has not been completely clarified. The present investigations were designed to show whether Zen induces an SOS-DNA repair response in lysogenic bacteria which have an integrated lambda-bacteriophage in their genome. Zen was found to be genotoxic in the bacterial systems from a concentration of 1.50 mM and it was also bactericidal (IC50 = 1.45 mM). In addition vitamin E (6.0-12.0 mM) added 1 h prior to the toxin proved to prevent both the genotoxic and bactericidal effects of Zen. This vitamin could be active both as an antioxidant and as a radical scavenger. The specificity of this prevention is probably due to the similarity of structure between vitamin E and Zen.

Animals↗
PubMed1997

Retinol, ascorbic acid and alpha-tocopherol prevent DNA adduct formation in mice treated with the mycotoxins ochratoxin A and zearalenone.

Ochratoxin A (OTA), and zearalenone (ZEN), two mycotoxins, have been implicated in numerous mycotoxicoses in farm animals and are genotoxic. Several adducts were detected in mouse and rat kidney after a single administration of OTA and in mice organs after zearalenone treatment which induces hepatocellular adenomas. The effects of some vitamins such as retinol (A), ascorbic acid (C) and alpha-tocopherol (E), which are known to act as superoxide anion scavengers, were tested on OTA genotoxicity. Pretreatment of mice by vitamin E decreased DNA adducts by 80% in kidney. Vitamin A decreased DNA adduct levels by 70% and Vitamin C by 90% in kidney. In the same way, pretreatment of female mice with alpha-tocopherol before administration of zearalenone inhibited significantly DNA adduct formation in liver and in kidney. The total DNA adduct level after E treatment was decreased by 45% and 58% in liver and kidney respectively.

Animals↗
PubMed1996

Zearalenone induces modifications of haematological and biochemical parameters in rats.

Zearalenone produced by the fungus Fusarium roseum causes important perturbations in the gestation cycle of the rat with hormonal disorders and infertility. In order to find out other eventual toxic effects, female rats were given intraperitoneally (i.p.) (1.5, 3 and 5 mg/kg) zearalenone in sterile olive oil. Forty-eight hours later, some blood parameters changed (hematocrit, MCV, the number of platelets and WBC) as well as some biochemical markers such as aminotransferases (ALT, AST), alkaline phosphatase (ALP), serum creatinine, bilirubin, indicating liver toxicity, and likely impairment of blood coagulation process.

Alkaline Phosphatase↗
PubMed1995

Foodstuffs and human blood contamination by the mycotoxin ochratoxin A: correlation with chronic interstitial nephropathy in Tunisia.

Ochratoxin A (OTA) has been detected in high amounts in human blood samples collected in nephrology departments in Tunisia from nephropathy patients under dialysis, especially those categorised as having a chronic interstitial nephropathy of unknown aetiology. These represent 12-26.1% of all chronic renal failure patients. To clarify the situation, food and blood samples were collected from nephropathy patients and controls, (with no familial case of nephropathy). The OTA assay showed very different scales of OTA food and blood contamination from 0.1 to 16.6 micrograms/kg and 0.1-2.3 ng/ml, respectively, in controls and healthy individuals and 0.3-46 830 micrograms/kg for food and 0.7-1136 ng/ml for blood in nephropathy patients. The disease seems related to OTA blood levels and food contaminations, since the control group was significantly different from the nephropathy group (p < 0.005) for both food and blood ochratoxin A contamination. Combined with data published already, the results emphasize the likely endemic aspect of this OTA-related nephropathy occurring in Tunisia and possibly in other countries of northern Africa. This nephropathy is very similar to Balkan endemic nephropathy.

Chronic Disease↗
PubMed1995

Genotoxicity of zearalenone, an estrogenic mycotoxin: DNA adduct formation in female mouse tissues.

Zearalenone is a non-steroidal estrogenic mycotoxin produced by several species of Fusarium which colonize maize, barley, oats, wheat and sorghum and have been implicated in numerous mycotoxicoses in farm animals, especially pigs. In a NTP mouse study a dose-related incidence of hepatocellular adenomas was seen in female mice. A limited number of genotoxicity assays have been conducted with zearalenone. Zearalenone was found to be negative in the Salmonella typhimurium assay. It was also negative in a eukaryotic cell mutation assay with Saccharomyces cerevisae. However, zearalenone and its estrogenic metabolites showed a positive DNA damaging effect in recombination tests with Bacillus subtilis. In this study DNA adducts in female mice and rat treated i.p or orally with zearalenone were determined using a 32P-postlabeling method. Several DNA adducts (12-15) were found in the kidney and liver of female mice treated with a single dose of zearalenone (2 mg/kg i.p. or orally). The total DNA adduct levels reached 114 +/- 37 and 1393 +/- 324 adducts/10(9) nucleotides respectively in kidney and liver after i.p. treatment and 548 +/- 50 adducts/10(9) nucleotides in liver after oral treatment. In mice ovary DNA adducts appeared only after repeated doses (1 mg/kg body wt on days 1, 5, 7, 9 and 10). The total DNA adducts after 10 days in this organ were 17 +/- 5 adducts/10(9) nucleotides. Some adducts were common to all organs. Others were specific to an organ. In contrast, no DNA adducts could be detected in rat organs after i.p. treatment. These results confirm the genotoxicity of zearalenone and its ability to induce hepatocellular adenomas, rather than tumours of genital organs, in mice.

Animals↗
PubMed1995

Ochratoxin A in human blood in relation to nephropathy in Tunisia.

The determination of ochratoxin A (OTA) in human blood in Tunisian populations is underway. The range of contamination is between 0.7 to 7.8 ng ml-1 for the general population and 12 to 55 ng ml-1 for people suffering from chronic renal failure. It appears that 21 to 64% of people suffering from nephropathy are OTA positive with a detection limit of 1ng ml-1. This situation prompted us to search for possible association of OTA contamination and nephropathy resembling Balkan endemic nephropathy. The classification of the ill population into chronic interstitial nephropathy (CIN), chronic glomerular nephropathy (CGN), chronic vascular nephropathy (CVN) and others, indicated that the largest is the CIN group which is significantly different from the other groups, and from the control (P < 0.005). Furthermore, it presented the highest OTA mean values (25 to 59 ng ml-1) compared with the control, CGN, CVN and other groups (6 to 18 ng ml-1) according to the designated region in Tunisia. The rural population seems to be more exposed to ochratoxins in Tunisia, as has been previously reported in the Balkans and Western Europe. Altogether, these results emphasise that in Tunisia an endemic ochratoxin-related nephropathy is probably occurring.

Adult↗
PubMed1992

Isolation and structure determination of natural analogues of the mycotoxin ochratoxin A produced by Aspergillus ochraceus.

Three new natural mycotoxins, analogues of ochratoxin A, in which the phenylalanine moiety is replaced by serine, hydroxyproline or lysine, were isolated from cultures of Aspergillus ochraceus by TLC followed by HPLC column chromatography. Their structures were determined after acidic hydrolysis by the characterisation of both their amino acid moieties and of ochratoxin alpha, the chlorinated dihydroisocoumarin moiety of ochratoxin A. These structures were confirmed by mass spectrum analysis.

Aspergillus ochraceus↗
PubMed1989

Influence of ochratoxin B on the ochratoxin A inhibition of phenylalanyl-tRNA formation in vitro and protein synthesis in hepatoma tissue culture cells.

Ochratoxin B (OTB), the dechloro-analogue of ochratoxin A (OTA), was studied separately and in combination with OTA on the aminoacylation of phenylalanine tRNA (tRNAPhe) catalysed by mice liver phenylalanyl-tRNA synthetase. OTB was neither a significant inhibitor of the reaction nor an antagonist of OTA. OTB was also assayed for its possible antagonistic effect on the in vivo protein synthesis inhibition caused by OTA in hepatoma tissue culture cells. No prevention of OTA inhibition could be found for OTB. It rather showed a slight additional inhibitory activity when mixed (100-180 microM) with low concentrations of OTA (40-60 microM). In conclusion, these results are not in favor of an antagonistic effect of OTB with respect to OTA action, at least on the level of cellular protein synthesis.

Animals↗
PubMed1985

Correlation between alimentary mycotoxin contamination and specific diseases.

Several pathological cases including primitive hepatomas, Reye's syndrome, alimentary toxic aleukaemia, were encountered in two different Tunisian Sahel hospitals. Contamination of some nutriments of the patients by mycotoxins (aflatoxins, trichothecenes, ochratoxin A, citrinin) are most likely involved in the origin of these diseases.

Carcinoma, Hepatocellular↗
PubMed1982

Conformational activation of aminoacyl-tRNA synthetases upon binding of tRNA. A facet of a multi-step adaptation process leading to the optimal biological activity.

The activation of the catalytic center of aminoacyl-tRNA synthetases upon binding of the tRNA, previously reported in the case of yeast phenylalanyl-tRNA and valyl-tRNA synthetases [Renaud et al., (1981) Proc. Natl Acad. Sci. USA, 78, 1606-1608] has been investigated in other systems. It is shown that this property is encountered not only in cognate systems (phenylalanyl, valyl and arginyl) but also in the non-cognate systems which are particularly efficient in misaminoacylation reactions. The arginyl system, the peculiarity of which is to form the aminoacyladenylate only in the presence of the cognate tRNA, is shown to be a border-line case of this general process of catalytic center activation. In the case of the phenylalanyl system, the crucial role of the wybutine residue (adjacent to the anticodon) in the activation of phenylalanyl-tRNA synthetase by the tRNA core has been analysed by comparison with native or modified non-cognate tRNAs (tRNATyr, tRNAArg). It is proposed that upon complex formation between a tRNA and its cognate aminoacyl-tRNA synthetase, a multistep adaptation process takes place in order to promote the optimal rate for the aminoacylation reaction, thus contributing to the specificity of this reaction.

Adaptation, Biological↗
PubMed1981

Study of the interaction between yeast tRNAphe and yeast phenylalanyl-tRNA synthetase by monochromatic ultraviolet irradiation at various wavelengths. Advantages and limits of the method.

The interactions between yeast tRNAphe and phenylalanyl-tRNA synthetase were studied by analysis of the covalent adducts obtained upon monochromatic ultraviolet irradiation at different wavelengths (248, 282, 292, 302 and 313 nm). The high extent of inactivation of phenylalanyl-tRNA synthetase, together with the partial modification of tRNA, as well as the peculiar instability of most of the covalent bonds formed upon irradiation constitute severe limitations to the use of the technique and to the interpretation of the results. These disadvantages led us to select an irradiation wavelength of 248 nm and to use only mild isolation procedures allowing a good recovery of the covalent adducts formed. Seven major tryptic peptides of the enzyme were found to be cross-linked to tRNAPhe whereas six major T1-oligonucleotides were covalently linked to the protein, among these, the three cross-linked oligonucleotides previously described by Shoemaker and Schimmel (J. Biol. Chem. 250 (1975) 4440-4444) in the same system. The difference in the number of covalently linked oligonucleotides is discussed in the light of the instability of the covalent linkages. The localization of the six oligonucleotides at the inside of the two branches forming the L-shaped tRNA molecule is similar to that observed in the yeast valine system (Renaud et al., Eur. J. Biochem. 101 (1979) 475-483) and is consistent with the interaction model previously described (Rich and Schimmel, Nucl. Acids Res. 4 (1977) 1649-1665 and Ebel et al. in Transfer RNA: structure, properties and recognition, (1979) pp. 325-343 Cold Spring Harbor Laboratory, NY). The occurrence of covalent cross-linking upon irradiation in the tryptophan absorption band (302 nm) strongly suggests the participation of this residue in the stabilization of the tRNA enzyme complex.

Amino Acyl-tRNA Synthetases↗
PubMed1981

Conformational activation of the yeast phenylalanyl-tRNA synthetase catalytic site induced by tRNAPhe interaction: triggering of adenosine or CpCpA trinucleoside diphosphate aminoacylation upon binding of tRNAPhe lacking these residues.

Adenosine or CpCpA trinucleoside diphosphate can be aminoacylated by phenylalanyl-tRNA synthetase [L-phenylalanine:tRNAPhe ligase (AMP forming), EC 6.1.1.20] when the reaction takes place in the presence of tRNAPhe deprived of its 3' adenosine or pCpCpA terminus. This shows that, upon interaction with tRNA, a structural alteration of the enzyme's active site is achieved. This process may be a determining step in the specificity of the aminoacylation reaction.

Adenosine↗
PubMed1981

Fluorimetric study of yeast tRNAPheCCF in the complex with phenylalanyl-tRNA synthetase. Evidence for a correlation between the structural adaptation of both macromolecules and the appearance of the acylation activity.

The fluorescence properties of yeast tRNAPheCCF (tRNAPhe in which the 3'-terminal adenosine has been replaced by formycin) and tRNAPheCCFoxi-red (tRNAPheCCF after periodate oxidation followed by borohydride reduction) were studied in the complex with the cognate aminoacyl-tRNA synthetase. In both cases a conformational change affecting the 3' end was observed in a magnesium concentration range close to 1 mM. The modification of formycin fluorescence could be ascribed simultaneously to the existence of a tautomeric equilibrium of the fluorescent probe and to a pH effect raising from a prototropic effect at the active site of phenylalanyl-tRNA synthetase, and to a partial destacking of the 3'-formycin from the adjacent C residue. The observed transconformation, which can be related to the structure modification of the anticodon loop previously reported [Ehrlich, Lefèvre, and Remy (1980) Eur. J. Biochem. 103, 145-153], takes place in the magnesium concentration range allowing the transfer of the activated amino acid from the adenylate to the tRNA. The interconnection between the anticodon loop and the accepting end was further supported by the observation that wybutine excision hinders the specific structure modification of 3'-formycin upon binding to the synthetase. The tRNAPhe transconformations occurring in the complex with the cognate synthetase probably reflect a reciprocal adaptation of both macromolecules which might lead to the optimal aminoacylation velocity and thus contribute to the specificity of aminoacylation, since it was previously established that this specificity relies more strongly on the kinetics of the reaction than on a discrimination of tRNAs according to different affinities.

Amino Acyl-tRNA Synthetases↗