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Pseudoephedrine and caffeine are found in many over-the-counter drugs including decongestants and weight loss chemicals. Both are proven central nervous system stimulants, and they may potentially interact on human health. Frog Embryo Teratogenesis Assay-Xenopus (FETAX) was used to determine the developmental toxicity of pseudoephedrine and caffeine mixtures and to determine if synergism or antagonism occurs between the two on developmental toxicity. FETAX is a 96-hour developmental toxicity assay that screens for direct acting teratogens. Both have both been evaluated for developmental toxicity in FETAX but not as mixtures. The 96-hr LC50, 96-hr EC50, MCIG, and TI were determined for pseudoephedrine and caffeine in various mixtures. We tested five binary mixturesofthe two chemicals. The mixtures were basedonthe toxic unitsofeach chemical; where one toxic unit was equal to the 96-hr LC50. The toxic unit mixtures were pseudoephedrine to caffeine at toxic unit ratios of 0:1, 1:0, 3:1, 1:1, and 1:3 based on published literature. Toxic units were plotted on an isobole graph to determine if synergism, concentration response or antagonism occurred. Mixtures acted in a concentration additive interaction on the developmental toxicity. Malformations in mixtures were similar to those seen in caffeine with the exception of the mixture containing the most pseudoephedrine.
Embryos of Xenopus laevis (clawed frog) are an excellent model system to use in studying the effects of agents on cell division. To test the effects of conjugated linoleic acid (CLA) on cell division, X. laevis embryos were exposed to various CLA concentrations. CLA is a dienoic fatty acid found in fats developed by ruminant animals. Previous studies on rodents have shown CLA to be effective in preventing cancer, particularly breast and prostate cancer. However, the exact method by which CLA produces its chemopreventive action is unknown. A 3% water-soluble solution of CLA (from PharmaNutrients) was diluted to produce 0.1%, 0.25%, and 0.5% solutions. The embryos were incubated in these solutions and developmental rates and any abnormalities were recorded. We found that CLA slowed down the rate of cell division, produced abnormal blastomeric pigmentation and morphology, and eventually stopped development altogether. Abnormalities were not observed in the 0.1% solution until 24 hours of exposure, at which time the embryos stopped developing. The 0.25% solution slowed down cell division after 2 hours of exposure, and completely stopped development of the embryos after 3.5 hours. The highest concentration inhibited cell division and development after only 1 hour of exposure. All three solutions caused abnormal cell shape and pigmentation: individual animal blastomeres appeared to be surrounded by yolky areas, embryos seemed more easily deform-able, and animal blastomeres appeared darker than the controls.
The mitochondrial salvage pathway supplies deoxyribonucleotide triphosphates for mitochondrial DNA synthesis. Its rate limiting enzymes are deoxyguanosine kinase (dGK) and thymidine kinase2. Mutations in these enzymes lead to several mitochondrial diseases in infants. Deoxyguanosine kinase3 (dGK3) is an isoform of dGK that was cloned from gestational day 8 mouse embryos. The objective of this study was to characterize the developmental expression of dGK3 in mouse embryos. Non-radioactive Northern blot and reverse transcription-polymerase chain reaction analyses were used. Expression analyses showed that the smaller sized transcript of dGK3 was expressed in embryos from gestational day 8 through day 17. Expression levels were uniform from gestational day 8 to 15 with the lowest expression on gestational day 17. Further analyses showed expression of the gene in multiple adult tissues indicating the dGK3 is not an embryonic isoform of dGK. This study is the first analysis of dGK3 expression during early development.