Elemental mercury evolution mediated by humic Acid.

Elemental mercury is formed in aqueous solution by the chemical reduction of mercuric ion in the presence of humic acid. The reduction proceeds via first order kinetics (rate constant, 0.009 hour-(1)) and is depndent on pH. The reaction mechanism involves interaction of the ionic metal species with the free radical electrons of the humic acid.

Effects of soya bean flakes and liquorice root extract on enzyme induction and toxicity in B6C3F1 mice.

Both soya bean flakes (SBF) and liquorice root extract (LRE) have previously been reported to have anticarcinogenic properties, which have been thought to be related to an increased activity of specific enzymes responsible for the detoxification of chemical carcinogens. 30- and 90-day studies were conducted in male B6C3F1 mice to determine which, if any, of several detoxification enzymes are induced by SBF or LRE. Mice fed 8 and 25% LRE showed a variety of adverse clinical signs, poor weight gain and 30% mortality. Significant increases in liver:body weight ratios were observed in both the SBF and LRE groups. No significant treatment-related gross autopsy findings were observed in any of the SBF groups. A number of abnormalities were observed in the LRE groups, including lesions of the kidney, liver, spleen and thymus. Liver samples from the 90-day study were analysed for 7-ethoxycoumarin O-deethylase (7-ECOD), benzo[a]pyrene hydroxylase (BPH), superoxide dismutase (SOD), glutathione S-transferase (GST) and UDP-glucuronyl transferase (UDPGT) at 90 days, and at an interim 30-day autopsy. No treatment-related increases were observed for BPH or SOD. Both SBF and LRE induced modest increases in UDPGT activity. SBF induced modest increases in GST activity, but LRE decreased this activity. 7-ECOD activity was significantly increased by LRE and decreased by SBF. Samples from a 30-day study in which both LRE and SBF were administered at various dose levels were examined for UDPGT activity; all dose groups showed decreases in UDPGT activity relative to controls. The results suggest that both SBF and LRE may alter the activities of specific enzymes involved in the detoxification of chemical carcinogens; however, the combination of these two foodstuffs may not produce an additive effect in B6C3F1 mice.

Transgenic production of a variant of human tissue-type plasminogen activator in goat milk: generation of transgenic goats and analysis of expression.

We report the first successful production of transgenic goats that express a heterologous protein in their milk. The production of a glycosylation variant of human tPA (LAtPA--longer acting tissue plasminogen activator) from an expression vector containing the murine whey acid promoter (WAP) operatively linked to the cDNA of a modified version of human tPA was examined in transgenic dairy goats. Two transgenic goats were identified from 29 animals born. The first animal, a female, was mated and allowed to carry the pregnancy to term. Milk was obtained upon parturition and was shown to contain enzymatically active LAtPA at a concentration of 3 micrograms/ml.

Induction of human tissue plasminogen activator in the mammary gland of transgenic goats.

Three transgenic females from a first generation transgenic male were induced to lactate between 11 and 12 months of age using a series of estrogen and progesterone injections. The milk contained human longer acting tissue plasminogen activator (LAtPA) at comparable concentrations (1-3 mg/ml) as occurred in the original founder female. In addition, the transgenic male was induced with a hormonal regime and was shown to produce 0.85 mg/ml of LAtPA. Milk protein gels indicated that the milk products (casein, IgG) were essentially normal. These experiments show that expression data for this vector can be evaluated in a shorter period of time in dairy goats than would be required through normal gestation and lactation schedules and can be used to identify the relative expression of transgenes in mammary tissue that would occur during normal lactation.

Induction of hepatic mutations in lacI transgenic mice.

Transgenic B6C3F1 and C57BL/6 mice containing a lambda shuttle vector that carries a lacI target and an alpha lacZ reporter gene have been constructed for use in in vivo mutagenesis assays. After chemical treatment of mice carrying the lacI target gene, genomic DNA is isolated and the shuttle vector is recovered by exposing the DNA to lambda phage packaging extracts in vitro. Mutations in the lacI target gene that inactivate the repressor gene allow expression of the alpha lacZ reporter gene, resulting in blue mutant plaques. We have examined the ability of two genotoxic agents, dimethylnitrosamine (DMN) and methylmethane sulfonate (MMS), to induce mutations in these transgenic mice. Both compounds induce a variety of DNA adducts in mouse liver; DMN is a hepatocarcinogen that induces significant hepatic cell proliferation, but MMS is not hepatocarcinogenic and does not induce hepatic cell proliferation. The effects of animal age, differences in strain and dosing regimen, and length of expression time were evaluated. Mice were treated for 5, 14 or 21 days and were sacrificed 1, 8 or 22 days after the final dose to evaluate the effects of increased expression time on mutant frequency in liver. In 3 week old mice, DMN (2 mg/kg/day) produced 10- to 20-fold elevations in mutant frequency that increased with expression time and the number of treatments. In contrast, MMS (20 mg/kg/day) failed to increase the mutant frequency. DMN failed to induce mutations in 6 week old mice at 2 mg/kg/day, but 4 mg/kg/day yielded significant elevations in hepatic mutations. Sequencing results indicate that treatment of mice with DMN produced predominantly C:G-->T:A transitions.(ABSTRACT TRUNCATED AT 250 WORDS)