Assessment of Potential Carcinogenicity by Quantitative Structure-Activity Relationship (QSAR)

Already in 1978, Elisabeth C. Miller and James A. Miller came with a presumption that electrophilic molecules are predicted to be carcinogens. It is because DNA molecule is reached in nucleophilic centres that may covalently bind to such substances. Rules deduced by Millers are even nowadays irrefutable, and they are used as the basis of testing of the substance for its carcinogenicity potential. Toxicological discipline that emerged from Millers’ research is based on dependence of chemical structure of the substance and their biological activity. Even further, there are strict regularities between molecular structures and activities. The tool used in assessment of biological activity of a substance is known as SAR, an abbreviation from structure–activity relationship. Besides electrophilic centres, in assessment of carcinogenic potential of a substance, the SAR also encounters chemical surrounding (neighbouring functional groups), size of the substance, its lipophilicity, number and position of aryl rings, substitutions of hydrogens, epoxides in aliphatic moieties or rings, resonance stabilisation, etc. To these days, SAR has been upgraded to quantitative SAR (QSAR) which applies multivariate statistical methods quantitatively comparing detected characteristics of “alerts” with biological activity of known carcinogens. Nowadays, chemical industry developing novel active substances is unthinkable without application of QSAR

Toxicity of Pre-heated Composites Polymerized Directly and Through CAD/CAM Overlay

Svrha rada: Usporediti citotoksičnost/genotoksičnost zagrijanih kompozita polimeriziranih preko CAD/CAM overleja na kulturi izoliranih ljudskih limfocita. Materijali i postupci: Mikrohibridni (Z100, 3M ESPE) i nanopunjeni kompozit (Filtek Supreme Ultra, 3M ESPE) zagrijani su u uređaju za zagrijavanje kompozita (Calset, AdDent Inc.) na temperaturama od 37 °C (T1), 54 °C (T2) i 68 °C (T3). Mala količina zagrijanog kompozita stavljena je u cilindrični kalup (promjera 6 mm, debljine 0.65 mm), prekrivena Mylar folijom, sprešana, te osvjetljena izravno, preko CAD/CAM keramički pojačanog polimera (CRP) (LAVA Ultimate, 3M ESPE) ili CAD/CAM litij disilikatnog keramičkog overlaja (LDC)(e.max, Ivoclar/Vivadent) debljine 2 mm. Odmah nakon osvjetljavanja uzorci su stavljeni u staničnu kulturu limfocita izoliranih iz periferne krvi. Citotoksičnost je izmjerena metodom dvojnog bojenja etidijevim bromidom i akridinskom narančastom bojom koja omogućuje određivanje postotka živih stanica te stanica u apoptozi i nekrozi na osnovi njihovih morfoloških obilježja. Genotoksičnost je procijenjena uporabom komet-testa u alkalnim uvjetima. Rezultati: Za Z100, najveći postotak živih stanica zabilježen je na T1 (93,7 %) nakon izravnog osvjetljavanja; slijedi osvjetljavanje preko CRP-a (92,3 %) te LDC-a (91,7 % T1, T3). Za Filtek Supreme Ultra najveći postotak živih stranica zabilježen je nakon osvjetljavanja preko CRP-a (91,2 % T2), LDC-a (90 % T1, T3) te pri izravnom osvjetljavanju (88,7 % T2). Zaključak: Za oba ispitivana materijala, zagrijavanje na T1 i T2 postupak je izbora. S obzirom na genotoksičnost, ne preporučuje se zagrijavanje na T3.Objectives: The aim was to compare cytotoxicity/genotoxicity of pre-heated composites polymerized through CAD/CAM overlays on isolated human peripheral blood lymphocytes. Material and Methods: A microhybrid (Z100, 3M ESPE) and nanofilled composite (Filtek Supreme Ultra, 3M ESPE) were heated in a heating unit (Calset, AdDent Inc.) at different temperatures: 37 oC, 54 oC, and 68 oC. A small amount of heated composite was placed in a cylindrical mold (6mm diameter; 0.65mm thick), covered with a Mylar sheet, pressed and light-cured directly and through 2 mm thick CAD/CAM ceramic-reinforced polymer (CRP)(LAVA Ultimate, 3M ESPE) or CAD/CAM lithium disilicate ceramic (LDC)(e.max, Ivoclar/Vivadent) overlay. After curing, the specimens were immediately placed in a prepared lymphocyte cell culture. Cytotoxicity was assessed using a dye exclusion method by simultaneous staining with ethidium bromide and acridine orange, aimed to determine percentages of viable, apoptotic and necrotic cells. Genotoxicity was studied using alkaline comet assay. Results: For Z100, the highest percentage of viable cells is recorded at T1 (93.7%) after direct light curing, followed by light curing through CRP (92.3%) and through LDC (91.7%T1,T3). For Filtek Supreme Ultra, the highest percentage of viable cells is recorded while curing through CRP (91.0% T2), followed by LDC (90% T1,T3) and direct light curing (88.7%T2). Conclusion: For both tested materials, preheating the procedure at T1 and T2 may be the procedure of choice. In terms of genotoxicity, reheating at T3 may not be suggested

Genotoxic potential of dental bulk-fill resin composites

OBJECTIVE: To investigate both genotoxicity and hardening of bulk-fill composite materials applied in 4-mm layer thickness and photo-activated for different exposure times. METHODS: Three flowable bulk-fill materials and one conventional flowable composite were filled in molds (height: 4mm) and irradiated for 20 or 30s. The top (0mm) and bottom (4mm) specimen surface were mechanically scraped, and eluates (0.01g composite in 1.5ml RPMI 1640 cell culture media) prepared for each material, surface level and irradiation time. Genotoxicity was assessed in human leukocytes using both the alkaline comet assay and cytokinesis-blocked micronucleus assay, and Knoop hardness (KHN) was measured at the top and bottom specimen surface (n=8). RESULTS: At both irradiation times, none of the bulk-fill composites significantly affected comet assay parameters used in primary DNA damage assessment or induced significant formation of any of the scored chromatin abnormalities (number of micronuclei, nuclear buds, nucleoplasmic bridges), whether eluates were obtained from the top or bottom surface. Furthermore, no decrease in KHN from the top to the bottom surface of the bulk-fill materials was observed. On the other hand, the conventional composite irradiated for 20s showed at 4-mm depth a significant increase in the percentage of DNA that migrated in the tail and a significant increase in the number of nuclear buds, as well as a significant decrease in KHN relative to the top surface. SIGNIFICANCE: Bulk-fill resin composites, in contrast to conventional composite, applied in 4-mm thickness and photo-activated for at least 20s do not induce relevant genotoxic effects or mechanical instability

Effect of organic tomato (Lycopersicon esculentum) extract on the genotoxicity of doxorubicin in the Drosophila wing spot test

The consumption of organic tomatoes (ORTs) reduces the risk of harmful effects to humans and the environment caused by exposure to toxic agrochemicals. In this study, we used the somatic mutation and recombination test (SMART) of wing spots in Drosophila melanogaster to evaluate the genotoxicity of ORT and the effect of cotreatment with ORT on the genotoxicity of Doxorubicin® (DXR, a cancer chemotherapeutic agent) that is mediated by free radical formation. Standard (ST) cross larvae were treated chronically with solutions containing 25%, 50% or 100% of an aqueous extract of ORT, in the absence and presence of DXR (0.125 mg/mL), and the number of mutant spots on the wings of emergent flies was counted. ORT alone was not genotoxic but enhanced the toxicity of DXR when administered concomitantly with DXR. The ORT-enhanced frequency of spots induced by DXR may have resulted from the interaction of ORT with the enzymatic systems that catalyze the metabolic detoxification of this drug

Atrazine-induced apoptosis of splenocytes in BALB/C mice

<p>Abstract</p> <p>Background</p> <p>Atrazine (2-chloro-4-ethytlamino-6-isopropylamine-1,3,5-triazine; ATR), is the most commonly applied broad-spectrum herbicide in the world. Unintentional overspray of ATR poses an immune function health hazard. The biomolecular mechanisms responsible for ATR-induced immunotoxicity, however, are little understood. This study presents on our investigation into the apoptosis of splenocytes in mice exposed to ATR as we explore possible immunotoxic mechanisms.</p> <p>Methods</p> <p>Oral doses of ATR were administered to BALB/C mice for 21 days. The histopathology, lymphocyte apoptosis and the expression of apoptosis-related proteins from the Fas/Fas ligand (FasL) apoptotic pathway were examined from spleen samples.</p> <p>Results</p> <p>Mice administered ATR exhibited a significant decrease in spleen and thymus weight. Electron microscope histology of ultrathin sections of spleen revealed degenerative micromorphology indicative of apoptosis of splenocytes. Flow cytometry revealed that the percentage of apoptotic lymphocytes increased in a dose-dependent manner after ATR treatment. Western blots identified increased expression of Fas, FasL and active caspase-3 proteins in the treatment groups.</p> <p>Conclusions</p> <p>ATR is capable of inducing splenocytic apoptosis mediated by the Fas/FasL pathway in mice, which could be the potential mechanism underlying the immunotoxicity of ATR.</p

Chronic Exposure to the Herbicide, Atrazine, Causes Mitochondrial Dysfunction and Insulin Resistance

There is an apparent overlap between areas in the USA where the herbicide, atrazine (ATZ), is heavily used and obesity-prevalence maps of people with a BMI over 30. Given that herbicides act on photosystem II of the thylakoid membrane of chloroplasts, which have a functional structure similar to mitochondria, we investigated whether chronic exposure to low concentrations of ATZ might cause obesity or insulin resistance by damaging mitochondrial function. Sprague-Dawley rats (n = 48) were treated for 5 months with low concentrations (30 or 300 µg kg−1 day−1) of ATZ provided in drinking water. One group of animals was fed a regular diet for the entire period, and another group of animals was fed a high-fat diet (40% fat) for 2 months after 3 months of regular diet. Various parameters of insulin resistance were measured. Morphology and functional activities of mitochondria were evaluated in tissues of ATZ-exposed animals and in isolated mitochondria. Chronic administration of ATZ decreased basal metabolic rate, and increased body weight, intra-abdominal fat and insulin resistance without changing food intake or physical activity level. A high-fat diet further exacerbated insulin resistance and obesity. Mitochondria in skeletal muscle and liver of ATZ-treated rats were swollen with disrupted cristae. ATZ blocked the activities of oxidative phosphorylation complexes I and III, resulting in decreased oxygen consumption. It also suppressed the insulin-mediated phosphorylation of Akt. These results suggest that long-term exposure to the herbicide ATZ might contribute to the development of insulin resistance and obesity, particularly where a high-fat diet is prevalent

Modification of comet-FISH technique by using temperature instead of chemical denaturation

Comet-FISH technique is an extension of commonly used comet assay. Its purpose is to determine whether primary DNA damage which comet assay detects occurred within a sequence of interest that is visualized by hybridization of fluorescent probe. Presence of the signal in comet tail indicates impaired structural integrity of sequence. Our modifications to the original comet-FISH technique described by Rapp et al. (2000) [1] include: • increase in probe binding specificity, • increased rate of successful hybridization, • simultaneous temperature denaturation of both, slide and probe