Home About us Contact
|
Home About us Contact | ||
|
|
||
Low-dose Exposure (low-dose + exposure)
Selected AbstractsDietary exposure to low doses of bisphenol A: Effects on reproduction and development in two generations of C57BL/6J miceCONGENITAL ANOMALIES, Issue 3 2010Kenichi Kobayashi Abstract The present study was conducted to examine the effects of low-dose exposure to bisphenol A on reproduction and development in two generations of mice. Pregnant female C57BL/6J mice (F0) were fed a diet containing low doses of bisphenol A (0, 0.33, 3.3, or 33 ppm) from gestational day 6 through postnatal day 22, and the weanlings (F1 and F2) from each F0 and F1 dam group, respectively, were also fed these same concentrations of bisphenol A ad libitum until sacrifice. There were no treatment-related changes in body weight, body weight gain, food consumption, gestation length, or the number of live births on postnatal day 1 in F0 dams between the control group and bisphenol A groups. Sex ratio and viability were similar in all F1 pups. No treatment-related changes were observed in body weight, food consumption, developmental parameters, anogenital distance, or weight of any of the organs (liver, kidney, heart, spleen, thymus, testis, ovary, or uterus) in F1 and F2 adults in either sex. The epididymis weight was slightly higher with 0.33 and 3.3 ppm in F1 males, but this slight increase was neither dose dependent nor seen across generations. There were no treatment-related effects of bisphenol A on cauda epididymal sperm count or sperm motility in F1 or F2 males. These findings indicate that dietary exposure to bisphenol A between 0.33 and 33 ppm does not adversely affect reproduction or development as assessed in two generations of mice. [source] Subchronic exposure of BALB/c and C57BL/6 strains of Mus musculus to the radioactive environment of the Chornobyl, Ukraine exclusion zoneENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2001Brenda E. Rodgers Abstract Environmental contamination resulting from the Chornobyl, Ukraine, disaster offers a unique opportunity to examine the in vivo biological effects of chronic, low-dose exposure to radiation. Laboratory studies of acute exposure to ionizing radiation have been used to estimate risk and potential human health effects by the extrapolation of laboratory data to situations of low-dose environmental radiation exposure. Few studies, however, have explored the biological consequences of low-dose exposure via in situ environmental radiation in a sentinel species. In the present study, laboratory strains of Mus musculus (BALB/c and 57BL/ 6) were placed in environmental enclosures in the Red Forest region of the Chornobyl exclusion zone. Blood samples were obtained every 10 d, and the micronucleus (MN) test was employed to assess the potential for cytogenetic damage from exposure to Chornobyl radiation. Radionuclide uptake was monitored throughout the study, and dose was estimated for each individual as well as for their offspring. Total dose for the mice experimentally exposed to this environment averaged 1162 mGy for BALB/c (30 d) and 1629 mGy for C57BL/6 (40 d). A higher MN frequency for both strains was observed at day 10, although this change was only statistically significant in the C57BL/6 mice (,23 = 13.41, p = 0.003). Subsequent samples from C57BL/6 resulted in values at or less than the initial frequencies. In BALB/c mice, an increase in MN was also evident at day 30 (,22 = 10.38, p = 0.006). The experimental design employed here allows for the incorporation of traditional laboratory strains, as well as transgenic strains of Mus, as sentinels of environmental radiation contamination. [source] Multiple stressor effects of methoprene, permethrin, and salinity on limb regeneration and molting in the mud fiddler crab (UCA pugnax)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Todd A. Stueckle Abstract Exposure to multiple stressors from natural and anthropogenic sources poses risk to sensitive crustacean growth and developmental processes. Applications of synthetic pyrethroids and insect growth regulators near shallow coastal waters may result in harmful mixture effects depending on the salinity regime. The potential for nonadditive effects of a permethrin (0.01,2 ,g/L), methoprene (0.03,10 ,g/L), and salinity (10,40 ppt) exposure on male and female Uca pugnax limb regeneration and molting processes was evaluated by employing a central composite rotatable design with multifactorial regression. Crabs underwent single-limb autotomy followed by a molting challenge under 1 of 16 different mixture treatments. During the exposure (21,66 d), individual limb growth, major molt stage duration, abnormal limb regeneration, and respiration were monitored. At 6 d postmolt, changes in body mass, carapace width, and body condition factor were evaluated. Dorsal carapace tissue was collected, and protein and chitin were extracted to determine the composition of newly synthesized exoskeleton. The present results suggest chronic, low-dose exposures to multiple pesticide stressors cause less-than-additive effects on U. pugnax growth processes. Under increasing concentrations of methoprene and permethrin, males had more protein in their exoskeletons and less gain in body mass, carapace width, and body condition compared to females. Females exhibited less gain in carapace width than controls in response to methoprene and permethrin. Females also displayed elevated respiration rates at all stages of molt, suggesting a high metabolic rate. Divergent growth and fitness between the sexes over the long term could influence crustacean population resilience. [source] Radiation and breast carcinogenesis,PEDIATRIC BLOOD & CANCER, Issue 5 2001John D. Boice Jr. Abstract With the possible exception of radiation-induced leukemia, more is known about radiation-induced breast cancer than any other malignancy [1, 2]. Fourteen cohort studies have provided quantitative information on the level of risk following a wide range of doses in different populations around the world. Comprehensive studies have been conducted in Canada, Germany, Japan, Sweden and other Nordic countries, the United Kingdom, and the USA (Table I). Key features are the linearity in the dose response (i.e., a straight line adequately fits the observed data), and the effect modification of age at exposure (i.e., risk is inversely related to exposure age and exposures past the menopausal ages appear to carry a very low risk); and the minimal effect of fractionating dose on subsequent risk [3]. A recent combined analysis of almost 78,000 women and 1,500 breast cancer cases from eight cohorts confirmed the downturn in risk at the highest dose levels (related in part to the killing of cells rather than transformation) and that fractionation of dose has little influence on risk, at least on an absolute scale [4]. It is not known whether persons predisposed to cancer are at enhanced risk of radiation-induced breast cancer from low-dose exposures, although this seems unlikely [5]. New data on the effects of high doses following childhood exposures will be forthcoming from long-term studies of the survivors of childhood cancer (6,8). Med. Pediatr. Oncol. 36:508,513, 2001. © 2001 Wiley-Liss, Inc. [source] | ||||||||||