Athanasios Papadopoulos

Glutathione S–transferase in the defence against pyrethroids in insects

The correlation between the natural levels of GST and the tolerance to the insecticide decamethrin (dMT), as well as the interaction between the molecules of affinity purified enzyme and the insecticide were investigated in order to collect further information on the obscure role of the Glutathione S-transferase system (GST) as a mechanism of defence against pyrethroids. The studies were carried out, comparatively, on the larvae and pupae developmental stages of the coleopteran Tenebrio molitor, which exhibit varying natural levels of GST activity. No stage dependent susceptibility of the insect against pyrethroid insecticides was found during the first 24 h, however 48 h after treatment, the KD50 dose increased significantly due to the recovery of some individuals from the larvae stage. Simultaneous injection of decamethrin with compounds which inhibit GST activity in vitro, resulted in an increased tolerance, which was more pronounced in the pupae stage. Inhibition studies combined with competitive fluorescence spectroscopy and high pressure liquid chromatography (HPLC) showed that the insecticide binds probably to the active site of the enzyme inhibiting its activity towards CDNB in a competitive manner, but is not conjugated with GSH. According to this, GST offers a passive protection towards pyrethroid insecticides by binding to their molecule in a sequestering mechanism.

Purification of cytosolic glutathione transferases from Schistocephalus solidus (plerocercoid): interaction with anthelmintics and products of lipid peroxidation

Glutathione (GSH) transferase isoenzymes have been partially resolved from the cytosol of Schistocephalus solidus (plerocercoid) by GSH affinity chromatography and chromatofocusing at pH 7-5. The presence of isomeric forms was also suggested by analytical isoelectric focusing and high-performance liquid chromatography (HPLC). Gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis indicated that GSH transferase forms were dimers with a subunit size of approximately 24 kDa. The major GSH transferase form in S. solidus (plerocercoid) showed greater biochemical relationship to the Mu family of mammalian GSH transferase compared to the mammalian Alpha or Pi families. The major subunit purified by GSH affinity chromatography and reversed-phase HPLC also showed high N-terminal homology with the Mu family. A minor GSH transferase form appeared more biochemically related to the Alpha family with respect to substrate specificity and inhibitor sensitivity. The major GSH transferase was inhibited by haematin-related compounds, bile acids and a number of anthelmintics including members of the benzimidazole and phenol-based class of compounds. The major GSH transferase had conjugating activity with members of the trans, trans-2,4-alkadienal and trans-2-alkenal series, secondary products of lipid peroxidation.

Diffuse Large Cell Lymphomas: Identification of Prognostic Factors and Validation of the International Non-Hodgkin’s Lymphoma Prognostic Index

Several clinical prognostic factors have been identified that predict treatment outcome in patients with diffuse large cell lymphomas. An International Non-Hodgkin’s Lymphoma Prognostic Index (IPI) has been recently formulated. We tried to identify the clinical prognostic factors that predict treatment outcome in Greek patients with diffuse large cell lymphomas and validated the IPI in these patients. The possible prognostic variables for tumor response, relapse-free (RFS) and overall survival (OS) were analyzed in 239 consecutive patients treated with anthracycline-based chemotherapy regimens. In univariate analysis, factors associated with poor response were stages III–IV, performance status (PS) ≥2, spleen and bone marrow involvement, more than one extranodal site involved, increased lactate dehydrogenase (LDH) value, hemoglobin (Hb) <12 g/dl, albumin <3.5 g/dl, erythrocyte sedimentation rate (ESR) >50 mm/h. Multivariate analysis identified stage, PS, more than one extranodal site involved, increased LDH level, and ESR > 50 mm/h as the factors more predictive of poor response. For RFS, multiple Cox analysis found stages III–IV and bone marrow involvement to be statistically significant. For OS, multiple Cox analysis identified stage III–IV, PS ≥2, bone marrow involvement, more than one extranodal site involved, increased LDH level and ESR > 50 mm/h as negative prognostic factors. Patients stratified in the different risk groups of the IPI had a significantly different outcome regarding complete response (CR) rate, RFS and OS. In conclusion, although age >60 years was not recognized as an adverse factor in this analysis, our patients stratified in the different groups of the IPI had significant differences in CR rate, 2-year RFS and OS verifying the prognostic significance of the index. Bone marrow involvement and ESR > 50 mm/h, parameters that are not included in the IPI, adversely affected survival.

Toxicological and ecotoxic impact of secondary and tertiary treated sewage effluents.

Secondary sewage effluents are discharged in significant quantities in aquatic environments delivering pollutants that were not removed during treatment; yet advanced treated effluents are not lacking of contaminants. In this study, biochemical biomarkers were measured in liver and kidney of rainbow trout (Oncorynchus mykiss) exposed to unchlorinated, chlorinated and tertiary treated secondary sewage effluents. In addition, organic matter, nitrogen and suspended solids were assayed, while a common bioassay, Daphnia magna 21d reproduction test was also applied in order to examine potential relation between the performed bioassay and the biomarkers. Processes using oxidative conditions, such as ozonation and chlorination, resulted in significantly increased breeding rate (up to 74%) of the organism. Biomarkers measurements incorporated the determination of total glutathione (GSH), glutathione S-transferases (GST), glutathione peroxidase (GPX), lipid peroxidation (LPO) and an innovative biomarker in such applications, haem peroxidase. In general, the response of biomarkers was dependent upon the treatment method and it was tissue specific. Secondary effluents inhibited liver GST and haem peroxidase, while GSH levels and LPO were significantly provoked in liver. Ozonation provoked hepatic peroxidation, in terms of haem peroxidase and LPO, and GST; while the protective (to Reactive Oxidant Species - ROS) GSH was depleted, suggesting extended ROS attack to the organism. Similar response of biomarkers (but to a lesser extend) was observed after exposure of trout to effluents submitted to both coagulation and ozonation, emphasizing the significance of removing the residual organic matter by other methods than oxidative ones. Ozonation also enhanced renal LPO and GPX; however the former employment of coagulation limited the peroxidation phenomena. Chlorination mainly affected the levels of total GSH in both tissues.

Dioxin contamination after an accidental fire in the municipal landfill of Tagarades, Thessaloniki, Greece.

We report here a case study of dioxin contamination after a fire in the public landfill of Tagarades, which is situated southeast of Thessaloniki, Greece. The aim of this study was to determine the levels of PCDD/Fs and PCBs in food samples of meat, eggs, dairy products and vegetables, collected near the affected area, and to compare them with the usual levels found in Greek food. Soil samples were also gathered from various sites at a distance up to 5km from the landfill. Some food samples were found above the limits specified by the EU, while all food samples were above the usual levels of Greek food. The contaminated products were appropriately destroyed. The results of the soil and olive samples indicate a reverse correlation between dioxin contamination and distance from the contamination source. It should be noted that PCB levels were normal in all analyzed samples.

Effect of the form of the sesame-based diet on the absorption of lignans.

The effect of different forms of sesame-based diets on the concentration of plasma lignans was assayed by estimating the levels of certain lignans (sesame lignans and enterolignans) in the plasma of experimental animals. In a series of experiments, male Wistar rats were fed either a raw sesame-enriched diet or a tahini-enriched diet. The plasma concentration of the lignans (sesame lignans and enterolignans) was determined at various time intervals over a 24 h period after a single administration. Enterodiol and enterolactone concentration in the tahini-treated group was significantly higher than in the raw sesame-treated group. In another series of experiments, male Wistar rats were fed, for 15 d, diets enriched in raw dehulled sesame, sesame perisperm, sesame oil, tahini and a polyphenolic extract derived from the seed perisperm. Enterodiol and enterolactone plasma concentration was high in the case of the sesame perisperm in spite of its low concentration in the assessed sesame lignans. Overall, the levels of the sesame lignans and enterolignans present in plasma seem to be influenced not only by the amount of lignan intake but also by other factors such as the form of the sesame-based diet.

Treatment of intermediate‐ and high‐grade non‐Hodgkin's lymphoma using CEOP versus CNOP

Abstract: Introduction: During the last few years epirubicin (E) and mitoxantrone (M) (Novantrone) have been used in the treatment of non‐Hodgkins lymphoma (NHL), because of their favorable principal profile. In particular, M has less severe non‐hematological toxicity. Patients and methods: A randomized multicenter phase III study was conducted in order to compare the efficacy and toxicity of CEOP and CNOP in intermediate‐ and high‐grade NHL. CEOP (arm A) consisted of cyclophosphamide 1000 mg m−2, vincristine 2 mg, E 70 mg m−2 on day 1 and prednisone 60 mg on days 1–7. The CNOP regimen (arm B) was identical to CEOP except for replacement of E by M at a dose of 12 mg m−2. Randomization was stratified according to stages I–IV. From September 1993 to March 1999, 249 patients registered for the trial. Patient characteristics were equally distributed in the two arms, except for age and International Prognostic Index (IPI) groups. Results: There were no significant differences between the two groups in the rates of complete (CR) and partial response (PR). The overall response rate was 78% in arm A (57% CR, 21% PR) and 82% in arm B (60% CR, 22% PR). With a median follow‐up time of 47.3 months, the median survival was not reached in arm A, while it was 39.5 months in arm B (P = 0.09). Three‐year survival rates were 62.5% for CEOP and 51.5% for CNOP. There was no significant difference regarding the time to progression between the two groups (29.7 vs. 18.5 months); furthermore the median duration of CRs was 71.6 and 49 months for CEOP and CNOP, respectively (P = 0.07). The therapeutic efficacies of both regimens were equivalent among the four IPI groups. More alopecia was observed in arm A. WHO grade >2 neutropenia was more frequent in arm B. Supportive treatment with G‐CSF was given to 22 and 24 patients, respectively. Conclusion: There were no significant differences in terms of overall response rates, overall survival and time to progression between CEOP and CNOP in the treatment of intermediate‐ and high‐grade NHL. Patients with low or low intermediate IPI risk treated with either CEOP or CNOP showed significantly better survival, response rates and time to progression than those with high intermediate or high IPI risk. Therefore, new improved therapeutic approaches should be developed for the treatment of high IPI risk patients.

Effect of anoxia on the kinetic properties of pyruvate kinase and phosphofructokinase, and on glycogen phosphorylase activity in marine worms and earth worms

SummaryThe kinetic properties of PK and PFK were studied in aerobic versus 12-hours anoxic marine worms Hedistae(=Nereis) diversicolor and Diopatra neapolitana and earth worms Allolobophora calliginosa and Eisenia foetida. The total glycogen phosphorylase (a+b) activity and the percentage of active a form were also measured in the marine and earth worms under the same conditions. Anoxia exposure did not result in any significant changes of kinetic parameters of PK and total activities of glycogen phosphorylase from marine worms, but it altered the kinetic characteristics of PFK from H. diversicolor. Chromatographical studies showed that PK from both aerobic and anoxic marine worms is eluted from DEAE-cellulose as a single peak at 50 mM KCl. In contrast to marine worms, however, anoxia caused a marked change in kinetic properties of PK from both earth worms, resulting in a reduction of enzyme affinity for its substrate PEP. In addition, the enzyme existed in both earth worms in two distinct variants eluted from DEAE-cellulose column as peak I and peak II at 50 mM and 150 mM KCl, respectively. The ratio of enzyme units (peak I/peak II) was reduced significantly after 12 h of anoxia, indicating that these two peaks are interconvertible. Anoxia also caused a reduction of total glycogen phosphorylase activity in E. foetida and lowered the percentage of active a form of the enzyme by approximately 50% in both earth worms. Kinetic properties of PFK from both earth worms were not significantly affected by anoxia. However, their low Ka values for F-2,6-P2 imply that this effector may play an important role in PFK control in earth worms under anoxia.

Time-course of covalent modification of pyruvate kinase during anaerobiosis in the mantle muscle and the hepatopancreas of the limpet Patella caerulea (L)

SummaryThe changes in some kinetic properties of pyruvate kinase from the mantle muscle and the hepatopancreas of Patella caerulea, over a time-course of 16 or 8 h of acute hypoxia were studied. Up to the second hour of anaerobiosis PK exhibited changes of the kinetic properties in the direction of activation, whereas in the late stages of anaerobiosis in both tissues examined these changes occurred in the direction of inactivation. Although PKs from these tissues seemed to be regulated in a similar pattern during the early stages of anaerobiosis, they exhibited different kinetic properties under both normoxic and hypoxic conditions. Two forms of PK were found to be present in both the mantle muscle and the hepatopancreas of P. caerulea with different kinetic properties. The ratio of the enzyme units distributed between the two forms of PK (designated peak I and peak II) was varied during anaerobiosis indicating that the two forms of PK are interconvertible.

Effects of a diet rich in sesame ( Sesamum indicum ) pericarp on the expression of oestrogen receptor α and oestrogen receptor β in rat prostate and uterus

The expression of oestrogen receptors (ERalpha and ERbeta) in the prostate and uterus tissues of Wistar rats supplied for 8 weeks with a diet rich in sesame (Sesamum indicum) pericarp (30 %) was monitored. Eight male rats, aged 6 weeks, were divided into a control group fed on a normal diet, and an experimental one, provided with the normal diet enriched with 30 % sesame pericarp. A similar experiment was performed with female rats. At the end of the experiment, the prostate and uterus tissues were surgically removed and kept at - 80 degrees C for up to 2 months. Western blotting and quantitative real-time PCR (qRT-PCR) methods were used in order to investigate the levels of receptor proteins and mRNA. Significant increase in the expression of ERbeta in prostate and uterus was evident in both methods, while the magnitude of the observed alteration depended on the applied method. No statistically significant change was observed in the expression of ERalpha in uterus. In prostate, although the increase was more evident when investigated by means of qRT-PCR, the difference in expression of ERalpha was not statistically significant. In both tissues, a shift of the ratio of ERalpha:ERbeta in favour of ERbeta was evident, indicating, according to existing literature, a beneficial effect of the diet provided upon the health status of the organisms. It is suggested that this effect is attributed to the lignans present in the pericarp which exert phyto-oestrogenic activity.