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Three heteroarotinoids containing a nitrogen atom in the first ring and a C-O linking group between the two aryl rings were synthesized and evaluated for RAR and RXR retinoid receptor transactivation, tumor cell growth inhibition, and transglutaminase (TGase) induction. Ethyl 4-(N,4,4-trimethyl-1,2,3,4-tetrahydroquinolinyl)benzoate (1) contained an N-CH(3) group and activated all retinoid receptors except for RARgamma. Inceasing the hydrophobicity around the rings with analogues ethyl 4-(N,4,4,7-tetramethyl-1,2,3, 4-tetrahydroquinolin-6-oyloxy)benzoate (2) [7-methyl group added] and ethyl 4-(4,4-dimethyl-N-isopropyl-1,2,3, 4-tetrahydroquinolin-6-oyloxy)benzoate (3) [NCH(CH(3))(2) group at C-4] increased the potency and specificity for RARalpha, RARbeta, and RXRalpha, compared to 1, but had little effect on RXRbeta and RXRgamma activation. Although 1 and 3 were unable to activate RARgamma, 2 did activate this receptor with efficacy and high potency equal to that of 9-cis-retinoic acid (9-c-RA). All three heteroarotinoids exhibited 5-8-fold greater specificities for RARbeta over RARalpha. In addition, esters 1-3 inhibited the growth of two cell lines each derived from cervix, vulvar, ovarian, and head/neck tumors with similar efficiencies to that of 9-c-RA through a mechanism independent of apoptosis. The vulvar cell lines were the most sensitive, and the ovarian lines were the least sensitive. Ester 2 was similar to 1 and 3 except that 2 was a much more potent growth inhibitor of the two vulvar cell lines, which is consistent with strong RARgamma activation by 2 (but not by 1 and 3) and the high levels of RARgamma expression in skin. All three heteroarotinoids induced production of TGase, a marker of retinoid activity in human erythroleukemic cells. Esters 2 and 3 were the more potent TGase activators than 1, in agreement with the stronger activation of the RAR receptors by 2 and 3. The biological activities of these agents, and the RARgamma potency of 2 in particular, demonstrate the promise of these compounds as pharmaceutics for cancer and skin disorders.

Application of relatively low nitrogen doses results in high yield and high quality of Marandu grass under continuous stock. The herbage, forage accumulation rate, and nutritive value increased linearly with nitrogen application rate. Our data are applicable to that of tropical areas with Oxisol, seasonal rainfall (wet summer), Marandu palisade-grass, and Nellore cattle during the rearing phase.

The apparent nitrogen recovery was inversely proportional to the nitrogen application rates. The critical N increased with increasing nitrogen level and the NNI showed that the N application was enough to supply the critical N level for Marandu grass nutrition.

In this study, our aim was to explore variation in carbon and nitrogen isotope values within and between feathers of individual birds, and the factors that contribute to such variation. We examined isotopic variation in feathers collected from adults of two small congeneric petrel species, the broad-billed prion Pachyptila vittata and Antarctic prion P. desolata. Broad-billed prions are dietary specialists that feed predominantly on large copepods, and Antarctic prions feed on a wider range of small zooplankton taxa (Brooke 2004). Both species are vulnerable to predation by skuas Stercorarius spp. that breed near to prion colonies (Furness 1987), providing the remains of recently killed birds for sampling. These two species were considered to be ideal for our study, as narrow diet breadth should limit the degree of variation in feather isotope values related to individual diet specialisation. In addition, prions undergo a complete moult of primary feathers during the nonbreeding period (Bridge 2006), allowing us to examine changes in isotope values within and between feathers of individuals.

Differences in feather isotope values between samples were examined by fitting isotope value as the response variable in a linear m


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