-Mice possessing the lethal yellow mutation (C57BL/6J A y /a) become obese and develop hyperleptinemia and leptin resistance as they age. To determine the relationship between altered leptin physiology and reproductive function in these mice, we compared body weight (BW), serum leptin concentration, ovulation rate, and in vitro blastocyst development among 120-and 180-d-old lethal yellow and black non-mutant (a/a) mice. Estrous female yellow and black mice were mated with fertile black males. Oviducts were flushed ~ 36 h after mating and the recovered embryos were cultured for 96 h. BW, serum leptin levels, and the leptin:BW ratio differed among groups as follows: 180-d yellow > 120-d yellow > 180-d black = 120-d black. Ovulation rate was similar among 120-d yellow and black, and 180-d black mice. Among 180-d yellow mice, five of twelve mice failed to ovulate, but the other seven mice ovulated a similar number of oocytes as their black counterparts (8.4 ± 0.9 versus 8.0 ± 1.3). Non-ovulators had higher (P < 0.05) leptin levels (56.6 ± 1.8 ng·mL -1 ) than ovulators (46.2 ± 3.5), but BW did not differ significantly. Fewer embryos from 180-d yellow mice reached the blastocyst stage in culture than did the embryos from black mice (55% versus 83%, P < 0.05). Moreover, blastocyst development in 180-d old yellow mice negatively correlated with leptin levels (r = -0.797, P = 0.032) and leptin:BW ratio (r = -0.847, P = 0.016), but not with BW. Declining reproductive function in lethal yellow mice appears to be related to increasing levels of leptin and progression of leptin resistance. obesity / leptin / agouti / reproduction

Background: Women with polycystic ovary syndrome (PCOS) are often treated with insulinsensitizing agents, e.g. thiazolidinediones (TZD), which have been shown to reduce androgen levels and improved ovulatory function. Acting via peroxisome proliferator-activated receptor (PPAR) gamma, TZD alter the expression of a large variety of genes. Lethal yellow (LY; C57BL/6J Ay/a) mice, possessing a mutation (Ay) in the agouti gene locus, exhibit progressive obesity, reproductive dysfunction, and altered metabolic regulation similar to women with PCOS. The current study was designed to test the hypothesis that prolonged treatment of aging LY mice with the TZD, pioglitazone, alters the ovarian expression of genes that may impact reproduction.

The distribution and abundance of macroinvertebrates along a water depth gradient were studied in thermal and ambient temperature areas of a reservoir in the southeastern United States. Benthic samples were taken at 10 depths (0.16-5 m) during January- April, 1978. Factors affecting the depth distribution of Ceratopogonidae, Chaoboridae, Chironomidae, Ephemeroptera, Odonata, and Trichoptera are discussed. The relationship between abundance of organisms and water depth was more complex than an inverse relationship generally reported in the literature.

Background: Lethal yellow (LY; C57BL/6J A y /a) mice exhibit adult-onset obesity, altered metabolic regulation, and early reproductive senescence. The present study was designed to test the hypothesis that obese LY mice possess differences in expression of ovarian genes relative to age-matched lean mice.