Biological activity of 2,4,8-trichlorodibenzofuran: promotion of rat liver foci and induction of cytochrome P-450-dependent monooxygenases

The biological activity of 2,4,8-trichlorodibenzofuran (2,4,8-TCDF) was tested using 2 endpoints: (a) the promotion of enzyme-altered, preneoplastic foci initiated by diethylnitrosamine (DEN) in livers of weanling female Sprague-Dawley rats; and (b) the induction of aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH), a marker for cytochrome P-4501 activity, in livers of adult female Sprague-Dawley rats and in H4IIEC3 rat hepatoma cells. When animals were treated with 200 or 500 mg/kg 2,4,8-TCDF 5 X weekly over 10 weeks after a single application of 10 mg/kg DNA, the higher dose of 2,4,8-TCDF had a promoting effect on the appearance of preneoplastic foci. Thus number and total area of foci deficient in adenosine-5'-triphosphatase were significantly increased by a factor of 1.6. 2,4,8-TCDF induced AHH-activities in 9000 X g supernatants of liver 2-3-fold, when rats were treated with 100-1000 mg/kg/day for 5 days and monooxygenase activities determined after another 3 days. The amounts of 2,4,8-TCDF required for inducing AHH activity in H4IIEC3 cells were 7 orders of magnitude higher than those of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). the results indicate that the 2,4,8-TCDF has a biological activity which is extremely low compared to that of 2,3,7,8-TCDD.     

Dose-dependent emergence of preneoplastic foci in rat livers after exposure to 2-nitropropane

Male and female Sprague-Dawley rats, 4–6 days old were exposed for 3 weeks (6 h/day, 5 days/week) to 2-nitropropane vapours of 0, 25, 40, 50, 80 and 125 ppm. One week later polychlorinated biphenyls (Clophen A50, 10 mg/kg body weight) were administered for promotion twice a week for 8 weeks. Thirteen weeks after starting the experiments the logarithms of the numbers of preneoplastic liver foci deficient in adenosine-5-triphosphatase were found to be linearly related to the exposure concentrations of 2-nitropropane. Male rats exhibited an approximately four times lower foci incidence than females.     

The DNA damaging drug cyproterone acetate causes gene mutations and induces glutathione-S-transferase P in the liver of female Big Blue transgenic F344 rats [published erratum appears in Carcinogenesis 1998 Apr;19(4):707]

The gestagenic and antiandrogenic drug cyproterone acetate (CPA) is mitogenic, tumorigenic and induces DNA-adducts and DNA-repair synthesis in rat liver. Thus CPA is expected to be mutagenic. However in vitro mutagenicity test systems were negative. To examine whether CPA induces mutations in rat liver, the in vivo mutation assay based on Big Blue transgenic F344 rats was employed. Single oral doses of 25, 50, 75, 100 and 200 mg CPA/kg b.w. respectively were administered to female Big Blue rats. Six weeks after treatment, liver DNA was assayed for mutations. At the highest dose, 200 mg CPA/kg b.w., the frequency of (17 +/- 4) x 10(-6) spontaneous mutations was increased to a maximum of (80 +/- 8) x 10(-6) mutations. One-hundred and 75 mg CPA/kg b.w. resulted in mutation frequencies of (35 +/- 5) and (27 +/- 5) x 10(-6), respectively. The mutation frequency at doses of 50 and 25 mg CPA/kg b.w. was similar to that of vehicle treated controls. Statistical analysis of the dose-effect relationship revealed that it was not possible to decide whether a threshold dose exists or not. DNA adducts were analyzed by the 32P-postlabelling technique. The total level of the major and the two minor adducts observed in the autoradiograms increased between doses of 25 to 75 mg CPA/kg b.w. to a maximum of approximately 12,000 +/- 3000 adducts per 10(9) nucleotides. The level did not further increase significantly with 100 and 200 mg CPA/kg b.w. After CPA treatment no preneoplastic liver foci were observed. However, single glutathione-S-transferase placental form (GST-P) positive hepatocytes were observed and the frequency was dependent on the dose. These cells are not supposed to represent initiated cells, since they occurred only transiently after 6 weeks and disappeared thereafter completely. In conclusion, our results demonstrate that CPA is mutagenic in vivo. The mutation frequency increased at high CPA doses, when the increase of the DNA adduct formation had already ceased. This suggests that the mitogenic activity of CPA is required to express the mutations.      

Rolle der Diabetesberatung im digitalen Zeitalter

Digitization has long since taken hold in the diabetes sector. Digital support including pumps, rtCGM (CGM: continuous glucose monitoring, rtCGM: real time CGM), iscCGM (intermittent scanning CGM), apps as well as measuring devices with pattern recognition and a reminder function has become commonplace in many areas. Training to become a diabetes advisor provides diabetes professionals with appropriate basic knowledge to advise the patient in self-management with technical support. Continuous medical training to empower and support patients in health literacy, data protection and the use of telemedicine is imperative.     

Promoting activity of di(2-ethylhexyl)phthalate in rat liver foci bioassay

Summary The plasticizer DEHP but not DEHS exerted a weak promoting effect in a 12-week rat liver foci bioassay, using weanling female Sprague-Dawley rats. The effect was similar after doses of 200 and 500 mg/kg body weight, given 3 times weekly by gavage for 11 consecutive weeks after initiation with a single oral dose of 8 mg DEN/kg body weight. Lower doses were ineffective. The incidence of foci with deficiency in ATPase was enhanced about twice compared to rats treated with DEN only. The incidence of foci with expression of GGTase was not affected by DEHP treatment. The results match the findings with lifetime exposure studies, when liver tumors were found in rats and mice. The actual risk for man from environmental DEHP contamination seems to be low; the intake from highly contaminated food is calculated to be about 400-fold lower than the lowest effective dose in this study.Abbreviations DEHP di(2-ethylhexyl)phthalate - DEHS di(2-ethylhexyl)sebacate - ATPase adenosine-5-triphosphatase (EC 3.6.1.3) - GGTase gamma-glutamyltranspeptidase (EC 2.3.2.2) - DEN diethylnitrosamine Supported by grants from Umweltbundesamt Berlin (UBA 10604017)     

Comparison of three rat liver foci bioassays--incidence of preneoplastic foci initiated by diethylnitrosamine

Three rat liver foci bioassays have been compared with respect to their sensitivity by the histochemical demonstration of preneoplastic foci, and by the biochemical determination of alterations in enzyme activities of serum indicating hepatotoxicity. We studied the initiation/promotion schedules according to Oesterle and Deml (A), and according to Pereira (B, Broad Spectrum Protocol), and the initiation/selection protocol according to Tatematsu et al. (C), with diethylnitrosamine (DEN), given as a single initiating dose of 10 and 30 mg/kg body wt respectively. With all schedules Sprague-Dawley rats, either females, 3 weeks old (A), or males, 6 weeks old (B, C) were used. For promotion polychlorinated biphenyls (A) or phenobarbital (B) were administered. Selection was performed with 2-acetylaminofluorene (C). The rats in schemes (B) and (C) underwent partial hepatectomy one day prior to initiation. The number and total area of foci deficient in adenosine-5'-triphosphatase (ATPase) and positive in gamma-glutamyltranspeptidase (GGTase) was evaluated. In the complete schedule with 30 mg of DEN in system (A) foci incidence exceeded that of the other systems by about 7-fold (ATPase) and 2-fold (GGTase) respectively. The lower dose of DEN and all control experiments resulted in a respective lower foci yield. With scheme (C), but not with schemes (A) and (B), e.g. serum fructose-1.6-bisphosphatase and alkaline phosphatase were increased, suggesting liver cell damage. Thus tested with DEN, scheme (A) is most sensitive and causes a low impairment of animals' welfare.     

Hämangiome

Zusammenfassung  Hämangiome zählen mit einem Auftreten von bis zu 10% zu den häufigsten gutartigen Tumoren im Kindesalter. Sie sind charakterisiert durch ein aggressives Wachstum während der ersten Lebensmonate (Proliferationsphase), gefolgt von einer allmählichen Regression (Involutionsphase) bis zur völligen Abheilung bei 90% der Patienten im Alter von 10–12 Jahren (Endstadium). Aufgrund des natürlichen Tumorverlaufs ist in der Regel eine abwartende Haltung indiziert. Bei einer Beeinträchtigung vitaler Funktionen durch den Tumor stehen neben Kryo-, Laser- oder operativer Therapie die systemische Therapie mit Glukokortikoiden (GK) oder Interferon zur Verfügung.

Impact of codon usage modification on T cell immunogenicity and longevity of HIV-1 gag-specific DNA vaccines

In this study, we analyzed the in vitro expression, potency and longevity of immune responses induced in a Balb/c mouse model by a synthetic HIV-1 GAG gene exhibiting a codon usage that was adapted to that of highly expressed mammalian genes (syngag). In contrast to a vector containing the wild-type (wt) GAG gene, the syngag construct enabled highly efficient Gag expression in both human and rodent cell lines in complete absence of Rev and Rev-responsive element. Immunization of Balb/c mice with the wt gag plasmid DNA induced only weak and inconsistent humoral immune responses. Mice vaccinated by syngag but not wt gag developed substantial and highly consistent Gag-specific antibody titers showing a clear T helper 1 polarization even with low doses of DNA. Moreover, vaccinated mice developed a strong Gag-specific cellular immune response, including cytotoxic T cells, which was not observed in wt gag-immunized animals. Both humoral and cellular immunity were efficient and lasted for more than 20 weeks. Furthermore, the induction of the humoral as well as the cellular immune response was independent of the immunization route (intramuscular or subcutaneous). These results clearly show the advantages of codon-optimized genes with respect to the expression and immunogenicity of plasmid DNA constructs, making them promising vaccine candidates for further studies.