Nano-TiO2 stability in medium and size as important factors of toxicity in macrophage-like cells.

TiO2 along with nano-TiO2 are commonly found in consumer products. In vivo studies have observed an accumulation of nano-TiO2 in macrophages. However, characteristics of nano-TiO2 determining toxicity remain unclear. In our study, the cytotoxic effects of 14 diverse nano-TiO2 on THP-1 macrophage-like cells were measured by 3 cytotoxicity assays (MTS, WST-1 and LDH). Total averaged cytotoxicity was calculated using principal component analysis. Characteristics of all 14 nano-TiO2 included hydrodynamic diameter, zeta potential, shape, polydispersity index (PDI) and concentration; moreover, crystal form, specific surface area and crystallite size were measured for 10 nano-TiO2.The variables affecting cytotoxicity were chosen using LASSO (least absolute shrinkage and selection operator). Except for concentration, PDI in media measured within 1 h after preparation of the nanomaterial dispersion was selected as a variable affecting cytotoxicity: stable dispersion resulted in higher cytotoxic effects. Crystallite size has been shown to have nonlinear effects (particles of sizes between 20 and 60 nm were cytotoxic while smaller and larger ones were not) and thus it has been excluded from LASSO. The shape (particles/fibre) and crystal form did not affect the cytotoxicity. PDI and the nonlinear effect of size could be an explanation for the inconsistencies of the cytotoxicity of nano-TiO2 in various studies.

Depletion of CLL-associated patrolling monocytes and macrophages controls disease development and repairs immune dysfunction in vivo.

Chronic lymphocytic leukemia (CLL) is characterized by apoptosis resistance and a dysfunctional immune system. Previous reports suggested a potential role of myeloid cells in mediating these defects. However, the composition and function of CLL-associated myeloid cells have not been thoroughly investigated in vivo. Using the Eµ-TCL1 mouse model, we observed severe skewing of myeloid cell populations with CLL development. Monocytes and M2-like macrophages infiltrated the peritoneal cavity of leukemic mice. Monocytes also accumulated in the spleen in a CCR2-dependent manner, and were severely skewed toward Ly6C(low) patrolling or nonclassical phenotype. In addition, the percentage of MHC-II(hi) dendritic cells and macrophages significantly dropped in the spleen. Gene expression profiling of CLL-associated monocytes revealed aberrantly high PD-L1 expression and secretion of multiple inflammatory and immunosuppressive cytokines like interleukin-10, tumor necrosis factor-α and CXCL9. In vivo myeloid cell depletion using liposomal Clodronate resulted in a significant control of CLL development accompanied by a pronounced repair of innate immune cell phenotypes and a partial resolution of systemic inflammation. In addition, CLL-associated skewing of T cells toward antigen-experienced phenotypes was repaired. The presented data suggest that targeting nonmalignant myeloid cells might serve as a novel immunotherapeutical strategy for CLL.

Frequency of chromosomal aberrations in Prague mothers and their newborns.

The capital city of Prague is one of the most polluted areas of the Czech Republic. The impact of air pollution on the level of chromosomal aberrations was systematically studied: analyses were performed using fluorescence in situ hybridization (FISH) with whole-chromosome painting for chromosomes #1 and #4. In the present study, we analyzed the levels of stable (one-way and two-way translocations) and unstable (acentric fragments) chromosomal aberrations in 42 mothers living in Prague and in their newborns. The average age of the mothers was 29 years (range, 20-40 years). Blood samples were collected from October 2007 to February 2008. The average levels of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) and benzo[a]pyrene (B[a]P) in respirable particles (PM2.5), as determined by stationary monitoring, were 21.0+/-12.3 ng/m(3) and 2.9+/-1.8 ng/m(3), respectively. We did not observe any effect of either c-PAH or B[a]P exposure on the genomic frequency of translocations (per 100 cells, F(G)/100) in either group due to their similar exposure during the winter months. The mean values of F(G)/100 representing stable aberrations were 0.09+/-0.13 vs 0.80+/-0.79 (p<0.001) for newborns vs mothers, indicating a significant increase of F(G)/100 with age. On the other hand, the frequency of unstable aberrations did not differ between the two groups. Our results demonstrate how the patterns of different types of aberration differed between newborns and mothers: we observed 64.3% unstable aberrations and 35.7% stable aberrations in newborns vs 19.7% and 80.3% in mothers, respectively. Our results indicate that after birth the frequencies of aberrations are very low and that the aberrations are represented mainly by acentric fragments. The changes observed in mothers show a shift to stable aberrations represented mainly by two-way translocations. The mother's age affected the level of aberrations in newborns: the group of children born to older mothers (31-40 years) had significantly increased F(G)/100 levels.

The impact of air pollution on the levels of micronuclei measured by automated image analysis.

The measurement of micronuclei (MN) in human peripheral blood lymphocytes is frequently used in molecular epidemiology as one of the preferred methods for assessing chromosomal damage resulting from environmental mutagen exposure. In the present study, we evaluated the effect of exposure to carcinogenic polycyclic aromatic hydrocarbons (c-PAHs), volatile organic compounds (VOC) and smoking on the frequency of MN in a group of 56 city policemen living and working in Prague. The average age of the participants was 34+/-6 years. The study was conducted on the same subjects in February and May 2007. The concentrations of air pollutants were obtained from personal and stationary monitoring. A statistically significant decrease in the levels of pollutants was observed in May when compared with February, with the exception of toluene levels measured by stationary monitoring. The frequency of MN was determined by the automatic image scoring (MetaSystems Metafer 4, version 3.2.1) of DAPI-stained slides. The results of the image analysis indicated a significant difference in the frequency of MN (mean levels 7.32+/-3.42 and 4.67+/-2.92, for February and May, respectively). Our study suggests that automatic image analysis of MN is a highly sensitive method for evaluating the effect of c-PAHs and confirms that there are no differences between smokers and nonsmokers. These results demonstrate the ability of c-PAHs to increase MN frequency, even if the exposure to c-PAHs occurred up to 60 days before the collection of biological material. Our work is the first human biomonitoring study focused on the measurement of MN by automated image analysis for assessing chromosomal damage as a result of environmental mutagen exposure.

Biomarkers of exposure to tobacco smoke and environmental pollutants in mothers and their transplacental transfer to the foetus. Part II. Oxidative damage.

Oxidative damage to macromolecules may have numerous negative health consequences. We measured oxidative damage to DNA, proteins and lipids in 80 newborns and 79 mothers, analyzed the effect of mother's tobacco smoke exposure on oxidative stress, and assessed correlations between oxidative stress markers and bulky and PAH (polycyclic aromatic hydrocarbons)-specific DNA adducts. Mean levels (+/-S.D.) of 8-oxodeoxyguanosine (8-oxodG) per 10(5) dG in the placenta were 2.85+/-0.78; we did not see a difference between 8-oxodG levels in newborns born to mothers exposed and unexposed to tobacco smoke. Protein carbonyl levels, a marker of protein oxidation, were comparable in the umbilical cord and in maternal venous blood plasma (17.4+/-3.2 and 17.6+/-4.2nmol/ml plasma in newborns and mothers, respectively, p=0.66). Lipid peroxidation measured as levels of 15-F(2t)-isoprostane (15-F(2t)-IsoP) in plasma was significantly higher in newborns than in mothers (362+/-129 and 252+/-130pg/ml in newborns and mothers, respectively, p<0.001). We did not find any effect of tobacco smoke exposure on either biomarker in any group. Levels of both protein carbonyls and 15-F(2t)-IsoP in cord blood significantly correlated with those in maternal plasma (p<0.001). 8-oxodG levels positively correlated with plasma carbonyls in cord plasma, as well as with cotinine levels (marker of tobacco smoke exposure) in maternal plasma. 8-oxodG levels also correlated with bulky DNA adducts in lymphocyte DNA of newborns and mothers and with PAH-DNA adducts in the placenta. Our results showed higher lipid peroxidation in newborns than in mothers, close correlation of analyzed oxidative stress markers between newborns and mothers, and a relationship between oxidative stress and induction of DNA adducts.

Biomarkers of exposure to tobacco smoke and environmental pollutants in mothers and their transplacental transfer to the foetus. Part I: bulky DNA adducts.

(32)P-postlabelling and PAH-ELISA using the antiserum #29 were employed to analyze DNA adducts in venous and umbilical cord blood and the placenta of 79 mothers giving birth to 80 living babies in Prague (Czech Republic). Ambient air exposure was measured by stationary measurements of basic air pollutants (PM2.5, c-PAHs) during the entire pregnancy. Tobacco smoke exposure was assessed by questionnaire data and by plasma cotinine levels. The total DNA adduct levels in the lymphocytes of mothers and newborns were elevated by 30-40% (p<0.001) compared with the placenta. B[a]P-like DNA adduct (adduct with the identical chromatographic mobility on TLC as major BPDE derived DNA adduct) levels were elevated in the blood of mothers compared with the placenta and the blood of newborns (p<0.05 and p<0.01). In tobacco smoke-exposed mothers, higher DNA adduct levels in the blood of mothers and newborns compared with the placenta were found (p<0.001), whereas the total and B[a]P-like adduct levels were comparable in the blood of mothers and newborns. B[a]P-like adducts were elevated in the blood of mothers unexposed to tobacco smoke compared with that of corresponding newborns and the placenta (p<0.01). Total and B[a]P-like DNA adducts were increased in the placenta of tobacco smoke-exposed compared with unexposed mothers (p<0.001 and p<0.01). In lymphocytes of tobacco smoke-exposed mothers, the comparison of total adduct levels (1.18+/-0.67 vs. 0.92+/-0.28) and B[a]P-like DNA adducts (0.22+/-0.12 adducts/10(8) nucleotides vs. 0.15+/-0.06 adducts/10(8) nucleotides) with newborns indicated a 30-40% increase of adducts in mothers. Almost equal PAH-DNA adduct levels were detected by anti-BPDE-DNA ELISA in the placenta of tobacco smoke-exposed and -unexposed mothers. Our results suggest a protective effect of the placental barrier against the genotoxic effect of some tobacco smoke components between the circulation of mother and child. We found a correlation between adduct levels in the blood of mothers and newborns.

Chromosomal aberrations and SCEs as biomarkers of cancer risk.

Previous studies have suggested that the frequency of chromosomal aberrations (CAs), but not of sister chromatid exchanges (SCEs), predicts cancer risk. We have further examined this relationship in European cohorts comprising altogether almost 22,000 subjects, in the framework of a European collaborative project (CancerRiskBiomarkers). The present paper gives an overview of some of the results of the project, especially as regards CAs and SCEs. The results confirm that a high level of CAs is associated with an increased risk of cancer and indicate that this association does not depend on the time between CA analysis and cancer detection, i.e., is obviously not explained by undetected cancer. The present evidence indicates that both chromatid-type and chromosome-type CAs predict cancer, even though some data suggest that chromosome-type CAs may have a more pronounced predictive value than chromatid-type CAs. CA frequency appears to predict cancers at various sites, although there seems to be a particular association with gastrointestinal cancers. SCE frequency does not appear to have cancer predictive value, at least partly due to uncontrollable technical variation. A number of genetic polymorphisms of xenobiotic metabolism, DNA repair, and folate metabolism affect the level of CAs and might collectively contribute to the cancer predictivity of CAs. Other factors that may influence the association between CAs and cancer include, e.g., exposure to genotoxic carcinogens and internal generation of genotoxic species. Although the association between CA level and cancer is seen at the group level, an association probably also exists for the individual, although it is not known if an individual approach could be feasible. However, group level evidence should be enough to support the use of CA analysis as a tool in screening programs and prevention policies in occupational and environmental health.

Chromosomal aberrations in peripheral lymphocytes of children as biomarkers of environmental exposure and life style.

The original purpose of our study was to determine if the detection of chromosomal aberrations in peripheral lymphocytes of children might be used as a biomarker of environmental pollution and life style. We compared the results of cytogenetic analyses performed in children and adolescents in the periods 1984-1993 and 1994-1999, in a total of 3402 subjects. The frequency of aberrant cells (AB.C.) markedly decreased in the period 1994-1999 compared with the period 1984-1993. The decreases in AB.C. were significant in the age groups 7-15 and 16-19 years: 1.63% AB.C. versus 1.14% AB.C. and 2.02% AB.C. versus 1.08% AB.C., respectively (P<0.01). No difference in the frequency of AB.C. was observed in newborns. Based on our experience, we believe that monitoring the spontaneous level of chromosomal aberrations in children over 5 year periods may be used to examine the general changes in environmental pollution in larger geographic areas.

Risk of cancer in an occupationally exposed cohort with increased level of chromosomal aberrations.

We used cytogenetic analysis to carry out a cohort study in which the major objective was to test the association between frequency of chromosomal aberrations and subsequent risk of cancer. In spite of the extensive use of the cytogenetic analysis of human peripheral blood lymphocytes in biomonitoring of exposure to various mutagens and carcinogens on an ecologic level, the long-term effects of an increased frequency of chromosomal aberrations in individuals are still uncertain. Few epidemiologic studies have addressed this issue, and a moderate risk of cancer in individuals with an elevated frequency of chromosomal aberrations has been observed. In the present study, we analyzed data on 8,962 cytogenetic tests and 3,973 subjects. We found a significant and strong association between the frequency of chromosomal aberrations and cancer incidence in a group of miners exposed to radon, where a 1% increase in frequency of chromosomal aberrations was followed by a 64% increase in risk of cancer (p < 0.000). In contrast, the collected data are inadequate for a critical evaluation of the association with exposure to other chemicals.

The effect of dibenzo[a,1]pyrene and benzo[a]pyrene on human diploid lung fibroblasts: the induction of DNA adducts, expression of p53 and p21(WAF1) proteins and cell cycle distribution.

Polycyclic aromatic hydrocarbons (PAHs) present in ambient air are considered as potential human carcinogens, but the detailed mechanism of action is still unknown. Our aim was to study the in vitro effect of exposure to dibenzo[a,l]pyrene (DB[a,l]P), the most potent carcinogenic PAH ever tested, and benzo[a]pyrene (B[a]P) in a normal human diploid lung fibroblast cells (HEL) using multiple endpoints. DNA adduct levels were measured by 32P-postlabelling, the expression of p53 and p21(WAF1) proteins by western blotting and the cell cycle distribution by flow cytometry. For both PAHs, the DNA adduct formation was proportional to the time of exposure and dependent on the stage of cell growth in culture. DNA binding was detectable even at the lowest concentration used (24h exposure, 0.01 microM for both PAHs). The highest DNA adduct levels were observed after 24h of exposure in near-confluent cells (>90% of cells at G0/G1 phase), but DNA damage induced by DB[a,l]P was approximately 8-10 times higher at a concentration one order of magnitude lower as compared with B[a]P (for B[a]P at 1 microM and for DB[a,l]P at 0.1 microM: 237+/-107 and 2360+/-798 adducts/10(8) nucleotides, respectively). The induction of p53 and p21(WAF1) protein occurred subsequent to the induction of DNA adducts. The DNA adduct levels correlated with both p53 (R=0.832, P<0.001 and R=0.859, P<0.001, for DB[a,l]P and B[a]P, respectively) and p21(WAF1) levels (R=0.808, P<0.001 and R=0.797, P=0.001, for DB[a,l]P and B[a]P, respectively), regardless of the PAH exposure and the phase of cell growth. The results showed that a detectable increase of p53 and p21(WAF1) proteins (> or = 1.5-fold as compared with controls) requires a minimal DNA adduct level of approximately 200-250 adducts/10(8) nucleotides for both PAHs tested and suggest that the level of adducts rather than their structure triggers the p53 and p21(WAF1) responses. The cell cycle was altered after 12-16h of treatment, and after 24h of exposure to 0.1 microM DB[a,l]P in growing cells, there was approximately 24% increase in S phase cells accompanied by a decrease in G1 and G2/mitosis (G2/M) cells. Cell treatment with 1.0 microM B[a]P resulted in more subtle alterations. We conclude that DB[a,l]P, and to a lesser degree B[a]P, are able to induce DNA adducts as well as p53 and p21(WAF1) without eliciting G1 or G2/M arrests but rather an S phase delay/arrest. Whether the S phase delay observed in our study is beneficial for the survival of the cells remains to be further established.

Mutagenicity monitoring of airborne particulate matter (PM10) in the Czech Republic.

The mutagenic activities associated with inhalable airborne particulate matter (PM10) collected over a year in four towns (Czech Republic) have been determined. The dichloromethane extracts were tested for mutagenicity using the Ames plate incorporation test and the Kado microsuspension test both with Salmonella typhimurium TA98 and its derivative YG1041 tester strains in the presence and absence of S9 mixture. The aim of this study was to assess the suitability of both bacterial mutagenicity tests and to choose the appropriate indicator strain for monitoring purposes. To elucidate the correlation between mutagenicity and polycyclic aromatic hydrocarbons (PAHs), the concentration of PAHs in the air samples were determined by GC/MS. In general, the significant mutagenicity was obtained in organic extracts of all samples, but differences according to the method and tester strain used were observed. In both mutagenicity tests, the extractable organic mass (EOM) exhibited higher mutagenicity in the YG1041 strain (up to 97 rev/microg in the plate incorporation and 568 rev/microg in the microsuspension tests) than those in TA98 (up to 2.2 rev/microg in the plate incorporation and 14.5 rev/microg in the microsuspension tests). In the plate incorporation test, the direct mutagenic activity in YG1041 was on average 60-fold higher and in microsuspension assay 45-fold higher with respect to strain TA98. In the presence of S9 mix, the mutagenic potency in YG1041 declined (P<0.001) in summer, but increased in TA98 (P<0.05) in samples collected during the winter season. The microsuspension assay provided higher mutagenic responses in both tester strains, but in both strains a significant decrease of mutagenic potency was observed in the presence of S9 mix (P<0.001 for YG1041, P<0.05 for TA98 in winter). The mutagenic potencies detected with both indicator strains correlated well (r=0.54 to 0.87) within each mutagenicity test used but not (for TA98) or moderately (r=0.44 to 0. 66 for YG1041) between both of the tests. The mutagenic activity (in rev/m(3)) likewise the concentration of benzo[a]pyrene and sum of carcinogenic PAHs showed seasonal variation with distinctly higher values during winter season. A correlation between the PAH concentrations and the mutagenicity results for the plate incorporation, but not for the microsuspension tests was found. In samples from higher industrial areas, the higher mutagenicity values were obtained in plate incorporation test with TA98 and in both tests with YG1041 in summer season (P<0.05). According to our results, plate incorporation test seems to be more informative than microsuspension assay. For routine ambient air mutagenicity monitoring, the use of YG1041 tester strain without metabolic activation and the plate incorporation test are to be recommended.

Adverse reproductive outcomes from exposure to environmental mutagens.

The effect of environmental pollution on reproductive outcomes has been studied in the research project 'Teplice Program' analyzing the impact of air pollution on human health. Genotoxicity of urban air particles <10 microm (PM10) in in vitro system was determined by the analysis of DNA adducts. The highest DNA binding activity was observed in aromatic fraction, identifying DNA adducts of carcinogenic polycyclic aromatic hydrocarbons (PAHs) presumably diolepoxide-derived from: 9-hydroxybenzo[a]pyrene (9-OH-B[a]P), benzo[a]pyrene-r-7,-dihydrodiol-t-9,10-epoxide[+] (anti-BPDE), benzo[b]fluoranthene (B[b]F), chrysene (CHRY), benz[a]antracene (B[a]A), indeno[1,2,3-cd]pyrene (I[cd]P). Reproductive studies were conducted in both females and males. A study of the effects of PM10 exposure on pregnancy outcomes found the relationship between the intrauterine growth retardation (IUGR) and PM10 levels over 40 microg/m(3) in the first gestational month (Odds Ratio for 40-50 microg/m(3)50 microg/m(3)=1.9). Selected biomarkers were analyzed in venous blood, cord blood (chromosomal aberrations, comet assay) and placenta (DNA adducts, genetic polymorphisms of GSTM1 and NAT2 genotypes) of women enrolled in a nested case-control study. DNA adduct levels were higher in polluted vs. control districts, in smoking vs. nonsmoking mothers, and in GSTM1 null genotype, which was more pronounced in polluted district. No effect of air pollution was observed by cytogenetic analysis of chromosomal aberrations or by comet assay. The reproductive development of young men was followed by measures of semen quality, adjusted for ambient SO(2) exposure. The analysis identified significant associations with air pollution for <13% morphologically normal sperm, <29% sperm with normal head shape, <24% motile sperm. Analysis of aneuploidy in human sperm by FISH showed, aneuploidy YY8 was associated with season of heaviest air pollution. These findings are suggestive for an influence of air pollution on YY8 disomy. All these results indicate that air pollution may increase DNA damage in human population, which may be even higher for susceptible groups. Biomarkers of exposure (DNA adducts) and susceptibility (GSTM1 and NAT2) may indicate the risk of presumable low environmental exposure. Pregnancy outcome and semen studies imply that relatively low air pollution (higher than 40 microg PM10/m(3)) can significantly increase the adverse reproductive outcomes affecting both genders.

CD80 and IL-2 signals cooperate in the regression of tumors transplanted in congenitally athymic mice.

Interleukin-2 and CD80 transfectants of a methylcholanthrene-induced murine sarcoma Mc12 (Mc12-IL-2 and Mc12-CD80 cells) with similar tumorigenicity in euthymic mice were utilized for experiments designed to investigate a co-stimulatory role of the CD80 molecule in allogeneic, congenitally athymic (nu/nu) mice. The CD80-transfected cells were as tumorigenic in nu/nu mice as the parental Mc12 sarcoma. The IL-2-transfected cells grew only transiently and regressed in all nu/nu recipients during four weeks after challenge with doses up to 5x10(7) cells. The 1:1 mixture of parental Mc12 with Mc12-CD80 cells grew progressively in all inoculated nu/nu mice; in a 1:1 mixture with parental Mc12 cells, Mc12-IL-2 cells were able to cause regressions in approximately 50% of nu/nu mice; the 1:1 mixture of Mc12-IL-2 and Mc12-CD80 transfectants showed only transient growth and regressed during four weeks in all inoculated nu/nu mice. Adoptive transfer of cell-mediated immunity revealed that spleen cells from tumor regressors were capable of transferring the resistance to Mc12 tumor in nu/nu mice. The spleen cells from tumor regressors were not cytolytic when allowed to react in vitro with Mc12, Mc12-IL-2, or Mc12-CD80 target cells. However, when grown in IL-2-containing medium, splenocytes from tumor regressors, but not the splenocytes from tumor progressors, could develop cytolytic activity directed against Mc12 target cells that was comparable to that of the splenocytes from tumor-free controls. These results suggest that the rejection of tumors in nu/nu mice was mediated by IL-2-dependent mechanisms in which the CD80 molecule played a co-stimulatory role; the results also indicate that the ability to be activated by IL-2 and to give rise to cytolytic activity of nu/nu splenocytes from tumor progressors is decreased.

Event-related potential correlates of proactive interference in schizophrenic patients and controls.

Performance and event-related potentials (ERPs) were examined in a proactive interference (PI) task with 15 male schizophrenic patients and 15 matched healthy controls. Within a paired-associate task, 30 pairs of semantically unrelated words (A-B) were presented twice, followed by cued recall, in which the paired-associate B had to be named upon cue A. Subsequently, 50% of the A-words were paired with new words (A-C) and presented in random order together with 15 novel pairings (D-E). Slower responses and poorer recall of C- than of E-words in the final recall indicated PI in both groups. During acquisition, the paired-associates (C/E) evoked larger P3 and positive slow wave in controls than in patients. During recall, cues (A/D) evoked a slow wave with predominating anterior negativity in controls and posterior positivity in patients. The group-specific ERP pattern suggests deviant encoding and retrieval processes in schizophrenic individuals.

Granulocyte-macrophage colony-stimulating factor-producing tumour vaccines.

Murine sarcoma MC12 cells were transfected with the gene coding for murine granulocyte-macrophage colony-stimulating factor (GM-CSF). Tumorigenicity of a variety of cell clones with different expression of the inserted gene was assessed. All of the genetically manipulated MC12 cell clones examined were found to be less tumorigenic than the parental MC12 cell population. No correlation was observed between the production of GM-CSF by the clones and their tumorigenicity. It has been found that irradiation of the GM-CSF-producing cells with the dose of 150 Gy did not significantly inhibit the GM-CSF production during the period of 5 days after irradiation. These findings provided us with the rationale for using the irradiated GM-CSF-producing MC12 sarcoma vaccine for therapy. It has further been found than immunosensitivity of the genetically manipulated, GM-CSF-producing tumour targets to the IL-2-activated killer (LAK) cell-mediated cytolysis was significantly increased, as compared to the parental target cell population. Irradiated, GM-CSF-producing tumour vaccines were used for therapy of 3-day-old MC12 sarcoma transplants in syngeneic mice and for therapy of surgically induced minimal residual tumour disease. Neither small tumour transplants, nor tumour residua after surgery were significantly sensitive to the therapy with GM-CSF-producing tumour vaccines.

Spontaneous level of chromosomal aberrations in peripheral blood lymphocytes of control individuals of the Czech Republic population.

In order to assess the potential of cytogenetic determinations on peripheral blood lymphocytes as a mean of monitoring human population subjects to occupational and environmental exposures to genotoxins, accurate baseline data are required. During the past 20 years many results of the cytogenetic studies on peripheral blood lymphocytes from monitored occupationally exposed and non-exposed groups were obtained. At the time of blood drawing a questionnaire was administered. The questions covered a brief medical and family history including age, sex, medication, infectious diseases, smoking habits, X-ray examinations, alcohol consumption etc. Cytogenetic analysis from whole blood was carried out in short-term cultures. The cultivation time was 52 hours with all cells being in the first mitosis. A total of 100 well-spread metaphases containing 46 +/- 1 centromere were examined per donor on coded slides. Four categories of chromosome aberrations were evaluated: Chromatid and chromosome breaks, chromatid and chromosome exchanges. Cells bearing breaks or exchanges were classified as aberrant cells. Gaps were recorded but not scored as aberrations. Results of the cytogenetic analysis from control individuals (N = 5,430) indicated elevation of spontaneous frequency of aberrant cells (AB.C.) with age. We found 1.10% AB.C. (N = 551) in newborns; 0.71% AB.C. (N = 105) in the group 5-6 yr; 1.20% (N = 1,734) in the group 7-15 yr; 1.25% AB.C. (N = 239) in the group 16-19 yr and 1.59% (N = 2,801) in the group 20-63 yr.

The use of YG bacterial tester strains for the monitoring of drinking water mutagenicity.

The organic extract from the 50 drinking water specimens taken in four cities were tested for mutagenicity in the Ames test (plate incorporation assay) using the parent TA98 and TA100 strains, and derived YG1041 and YG1042 strains. Four dose levels of extractable organic matter (EOM) with duplicate plate per dose were used. Slopes (revertants/mg EOM) were calculated by the Bernstein linear regression rejection model using GeneTox Manager software. The mutagenicity observed in the conventional strains TA98 and TA100 did not reach the significant increase in all tested samples with the higher mutagenic response found in TA100-S9. With the YG1041 and YG1042 tester strains, the results obtained demonstrated the clear-cut direct dose-related mutagenicity response in all tested drinking water extracts. Compared with TA98 and TA100 strains, the numbers of YG induced revertants were approximately 20 times higher. The high sensitivity of the YG tester strains could facilitate the mutagenicity monitoring in drinking water extracts, and help reduce the volume of sample required. However, to identify the chemical contaminants in drinking water responsible for the mutagenicity further studies are required.

Chromosomal aberrations, sister-chromatid exchanges, cells with high frequency of SCE, micronuclei and comet assay parameters in 1, 3-butadiene-exposed workers.

The association of occupational exposure to 1,3-butadiene (BD) and induction of cytogenetic damage in peripheral lymphocytes was studied in 19 male workers from a monomer production unit and 19 control subjects from a heat production unit. The exposure to BD was measured by passive personal monitors. The following biomarkers were used: chromosomal aberrations (CA), sister chromatid exchanges (SCE), cells with a high frequency of SCE (HFC), micronuclei, comet assay parameters like tail length (TL) and percentage of DNA in tail [T (%)] and polymorphisms of GSTM1 and GSTT1 genotypes. BD exposure with a median value of 0.53 mg/m3 (range: 0.024-23.0) significantly increased (a) the percentage of cells with chromosomal aberrations in exposed vs. control groups (3.11% vs. 2.03%, P<0.01), (b) the frequency of SCE per cell (6.96 vs. 4.87, P<0.001), and (c) the percentage of HFC (19.9% vs. 4.1%, P<0.001). BD exposure had no significant effects on formation of micronuclei and on comet assay parameters. Effect of smoking was observed only for HFC in BD-exposed group. GSTM1 genotype affected chromosomal aberrations in exposed group, while GSTT1 genotype affected chromosomal aberrations in controls. No effect of GSTM1 or GSTT1 genotypes was observed on any other biomarkers used.

Interleukin-2 gene therapy of surgical minimal residual tumour disease.

Our study was designed to examine the effects of IL-2 gene therapy in a surgical minimal residual tumour disease (SMRTD). Mice were inoculated s.c. with methylcholanthrene (MC)-induced MC12 sarcoma cells. When the tumours reached 8 to 12 mm in diameter, they were excised, either completely ("microscopic SMRTD") or incompletely ("macroscopic SMRTD"). On day 90 after surgery, the tumour recurrence rate in untreated mice with microscopic SMRTD was approximately 30%, whereas in those with macroscopic SMRTD it was 75%. After surgery, experimental mice were treated with 2 types of irradiated, IL-2 gene-modified, IL-2-producing tumour cell vaccine. One type of vaccine was derived from the MC12 sarcoma cells (MC12-1L2/IV-3); the other type was derived from an unrelated X63-Ag8.653 plasmacytoma (X63-m-IL-2). Both types of vaccine failed to cure the macroscopic SMRTD. Whereas the X63-m-IL-2 vaccine was also ineffective in the microscopic SMRTD, the MC12-IL2/IV-3 vaccine was capable of preventing growth in all but one mouse (1164) with microscopic SMRTD when administered 2 to 5 days after surgery. If the vaccination took place 2 days before surgery or later than 5 days after surgery, the therapeutic activity was lost. Vaccination with irradiated parental MC12 cells did not produce any significant benefit compared to the operated-only mice. The protective effect of the MC12-L2/IV-3 vaccine was specific and comparatively long-lasting. Vaccinated mice, which had rejected the MC12 tumour residuum, were capable of rejecting a second inoculum of the MC12 sarcoma cells injected on days 35 to 110 after surgery but succumbed to the growth of 2 other unrelated murine sarcomas carrying different tumour-rejection antigens.

Immunogenicity, immunosensitivity and cell surface adhesiveness of tumour vaccines carrying an inserted CD80 gene.

Cell surface adhesiveness, immunogenicity and immunosensitivity of tumour vaccines modified by the CD80 gene transfection was examined and compared to that of the parental MC12 murine sarcoma. Insertion of the CD80 gene substantially enhanced the adhesiveness of the genetically modified tumour cells to nylon wool non-adherent (T) but not to nylon wool adherent (B) lymphocytes. The increased adhesive interaction could be inhibited by anti-CD80 monoclonal antibody. CD80+ transfectants were more sensitive to the cytotolytic effect of MC12-immune splenocytes and IL-2-activated spleen cells than the parental MC12 sarcoma. Similarly, spleen cells from syngeneic mice immunized with CD80+ transfectants displayed a higher cytolytic activity when allowed to react with MC12 cells than splenocytes from mice immunized with the parental MC12 cells. These results suggest that a positive correlation exists among the expression of the CD80 molecules, T cell adhesion to the genetically modified cells, immunosensitivity of the CD80+ transfectants and the capacity of the transfectants to activate cytolytic, tumour-reactive effector cells in vivo. This correlation provides a rationale for gene therapy based on the construction of CD80- modified tumour vaccines.