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M.B. Voltura

Publications and source records attributed to M.B. Voltura.

4 recordsLinked to original sources
USGS2006

Effects of dietary PCB exposure on reproduction in the white-footed mouse (Peromyscus leucopus)

Studies of the impact of environmental contaminants on reproduction have typically focused on effects on fertility and subsequent reproductive failure. Contaminants may also impact reproductive output or other aspects of life history through effects on resource acquisition or allocation. We fed successfully breeding female white-footed mice (Peromyscus leucopus) diets containing polychlorinated biphenyls (2:1 Aroclor 1242:1254) at levels of 0 (n = 10), 10 (n = 12), and 25 (n = 10) ppm (mg polychlorinated biphenyls [PCBs]/kg food). After 4 months on the diets, female mice were bred with male mice maintained on control food. There was no effect of PCB exposure on litter size at birth or weaning, although fewer female mice on the 25-ppm diet gave birth. There was no effect of PCB dose on maternal metabolic rate at peak lactation or on total food (dry matter) intake during lactation. Female mice on the 10-ppm diet, however, consumed more food per pup during lactation and weaned larger pups, although these differences disappeared after 4 weeks of age. We conclude that although moderate-term exposure to PCBs did decrease the number of litters produced for high-dose female mice, it did not change litter size, pup growth rate, or energetic measures for those female mice that did successfully reproduce.

Archives of Environmental Contamination and Toxico↗
USGS2001

Effects of pre- and postnatal polychlorinated biphenyl exposure on metabolic rate and thyroid hormones of white-footed mice

Energy budgets have proven to be a valuable tool for predicting life history from physiological data in terrestrial vertebrates, yet these concepts have not been applied to the physiological effects of contaminants. Contaminants might affect energy budgets by imposing an additional metabolic cost or by reducing the overall amount of energy taken in; either process will reduce the energy available for production (i.e., growth or reproduction). This study examined whole animal energetic effects of polychlorinated biphenyl (PCB) exposure in white-footed mice ( Peromyscus leucopus ). Exposure to PCBs is known to reduce concentrations of plasma thyroid hormones, and thyroid hormones exert strong control over the rate of energy metabolism in mammals. Peromyscus leucopus that were proven breeders were fed PCBs in their food at 0, 10, and 25 ppm. Through lactation, offspring were exposed to PCB from conception and were maintained on the maternal diet to adulthood. No effects were seen on energy metabolism (O 2 consumption, measured in adulthood) or on growth, but there were large dose-dependent decreases in thyroid hormone concentrations, particularly T 4 . The apparent disparity in our data between unchanged metabolic rates and 50% reductions in T 4 concentrations can be rationalized by noting that free T 3 (the fraction not bound to plasma protein) in treated mice was not significantly different from controls and that metabolism is most strongly influenced by free T 3 . Overall, this study did not demonstrate any energetic consequences of PCB exposure in P. leucopus at dietary concentrations up to 25 ppm.

Environmental Toxicology and Chemistry↗
USGS2000

Effects of dietary polychlorinated biphenyl exposure on energetics of white-footed mouse, Peromyscus leucopus

Energy budgets have provided physiological ecologists with a vital link between environmental variables and individual performance and should also prove useful to ecotoxicologists in understanding the effects of sublethal exposure in the field. Exposure to toxic compounds is likely to be metabolically expensive and may result in a trade-off between energy spent to detoxify and excrete contaminants and energy allocated to growth or reproduction. To quantify the energetic cost of polychlorinated biphenyl (PCB) exposure, we fed captive white-footed mice ( Peromyscus leucopus ) diets containing PCBs (2:1 Aroclor® 1242:1254) at levels of 0, 0.1, 10, and 25 ppm (mg PCBs/kg food). After six weeks on the diets, there were no differences in food intake (g/d), diet digestibility (%), or body mass related to the level of dietary PCBs. This indicated that short-term exposure to PCBs did not cause a detectable increase in energy need as measured by voluntary food intake. We continued to feed mice the PCB-containing diets for one year, at which time we repeated the food intake trial, and also measured oxygen consumption at 20 and 30°C. After one year, all mice had gained mass, but mice on the 25-ppm diet tended to be heavier than mice in the other groups. Compared to the control group, mice on the 25-ppm diet had higher food intake (4.1 vs 3.7 g/d; p = 0.06) and higher oxygen consumption at 30°C (40.1 vs 36.6 ml O 2 /h; p = 0.01). These results suggest that there is an energetic cost to long-term contaminant exposure that, when combined with other environmental stresses, may influence patterns of energy acquisition and allocation.

Environmental Toxicology and Chemistry↗