@article{RuhlFritzscheVermotetal.2006,
  author    = {Ruhl, R. and Fritzsche, Britta and Vermot, J. and Niederreither, K. and Neumann, U. and Schmidt, A. and Schweigert, Florian J. and Dolle, P.},
  title     = {Regulation of expression of the retinoic acid-synthesising enzymes retinaldehyde dehydrogenases in the uteri of ovariectomised mice after treatment with oestrogen, gestagen and their combination},
  year      = {2006},
  abstract  = {The active metabolite of vitaminA, retinoic acid (RA), plays an important role in the female reproductive system. The synthesis of RA is tightly regulated by the activity of retinaldehyde dehydrogenases (Raldh). Among these, Raldh1 and Raldh2 exhibit specific temporal and spatial expression patterns in the mouse uterus, both during the oestrous cycle and early pregnancy. In the present study, we have assessed whether oestradiol and progesterone directly influence the uterine expression of Raldh1 and Raldh2 in ovariectomised mice. We investigated the effect of gestagen (promegestone 0.3 mg kg(-1) bodyweight), oestrogen (oestradiol 3 mu g kg(-1) bodyweight) and their combination on the uterine expression of Raldh2. Expression was analysed using in situ hybridisation and quantified using real-time detection reverse transcription-polymerase chain reaction. The results show that the expression of Raldh2 is rapidly (within 1-4 h) induced in stromal cells by oestrogen, but not by gestagen, treatment, whereas combined oestrogen + gestagen treatment leads to a more prolonged (48 h) response. In contrast, oestrogen, but not progesterone, treatment downregulates (within 4 - 24 h) Raldh1 expression in the uterine glandular epithelium. We conclude that the uterine RA concentrations are regulated by oestrogens via an effect on the expression of the Raldh synthesising enzymes. Such a regulation is consistent with the natural fluctuations of Raldh expression during the oestrous cycle, early pregnancy and blastocyst implantation},
  language  = {en}
}
@article{RoggeItagakiFishkinetal.2005,
  author    = {Rogge, B. and Itagaki, Y. and Fishkin, N. and Levi, E. and Ruhl, R. and Yi, S. S. and Nakanishi, K. and Hammerling, U.},
  title     = {Retinoylserine and retinoylalanine, natural products of the moth Trichoplusia ni},
  issn      = {0163-3864},
  year      = {2005},
  abstract  = {Insect cells convert vitamin A into a number of retinoids that are evolutionarily conserved with those of mammalian cells. However, insect cells also produce additional natural retinoids. Namely, two retinoic acid peptides, N- trans-retinoylserine (1) and N-trans-retinoylalanine (2), have been isolated from a cell line of the common cabbage looper, Trichoplusia ni. These are the first examples of naturally occurring retinoic acid linked to amino acids through an amide bond; the amino acid moieties are depicted in the more common L-configuration, although the absolute configuration was not determined due to the minuscule sample amount},
  language  = {en}
}
@article{GarciaRuhlSchweigert2005,
  author    = {Garcia, Ada and Ruhl, R. and Schweigert, Florian J.},
  title     = {Retinoid concentrations in the mouse during postnatal development and after maternal vitamin a supplementation},
  issn      = {0250-6807},
  year      = {2005},
  abstract  = {Background: Vitamin A (VA) and its derivates (retinoids) are important nutritional substances, which mediate their biological activity mainly via nuclear retinoid receptors. Maternal VA intake during lactation influences the VA content in milk and the VA status of the progeny. We investigated the effects of maternal supplementation during lactation and direct supplementation to the pups after weaning on the retinoid concentration in serum and liver of neonatal mice using high doses of VA. Methods: Dams were fed a basal (4,500 retinol equivalents/ kg diet) or a VA- supplemented (324,000 retinol equivalents/ kg diet) diet during lactation. Pups kept receiving the same diet after weaning. Serum and liver samples of the pups were collected during lactation at days 1, 3, 5, 7, and 14 and post-weaning at days 21 and 65 after birth. Samples were analysed for retinoids by high-performance liquid chromatography. Results: Maternal VA supplementation resulted in significantly higher concentrations of retinol, retinyl palmitate and retinyl stearate in serum of mice neonates at days 5, 7, 14, 21 and 65 after birth in comparison to the basal diet, whereas significantly higher concentrations were observed in liver at days 5, 14, 21 and 65 after birth. At day 7 after birth, a decrease in the liver retinoid concentrations occurred in the VA-supplemented diet. Conclusion: Our results show for the first time that supplementation with high doses of VA during the lactation period in mice can affect serum retinol concentrations in the neonates and report that day 7 after birth is a critical time in the tissue distribution of retinoids during postnatal development. Copyright (C) 2005 S. Karger AG, Basel},
  language  = {en}
}
@article{PuvogelBaumruckerSauerweinetal.2005,
  author    = {Puvogel, Gerke and Baumrucker, C. R. and Sauerwein, H. and Ruhl, R. and Ontsouka, E. and Hammon, H. M. and Blum, J. W.},
  title     = {Effects of an enhanced vitamin A intake during the dry period on retinoids, lactoferrin, IGF system, mammary gland epithelial cell apoptosis, and subsequent lactation in dairy cows},
  issn      = {0022-0302},
  year      = {2005},
  abstract  = {Studies in vitro show important interactions among vitamin A, lactoferrin, and insulin-like growth factor (IGF) binding proteins (IGFBP) and, thus, the IGF system. As a consequence, mammary gland epithelial cell proliferation and apoptosis during the bovine dry period and potential milk yield may be affected. We have studied effects of feeding vitamin A (550,000 IU/d) that exceed daily requirements about 8-fold for up to 2 mo to dairy cows during the dry period on concentrations of retinol and its metabolites in plasma and milk, milk lactoferrin, plasma and milk IGF-I and IGFBP- 3, lactoferrin and IGF-I mRNA levels in mammary gland tissue, mammary gland apoptosis, and 100-d milk yield in the ensuing lactation. In the group supplemented with vitamin A, the peripartal decrease of plasma retinol was delayed and attenuated, and colostral retinol plus retinylester concentration was enhanced, but colostral beta-carotene concentration decreased. The retinoic acid isomer 9,13-dicis retinoic acid that coeluted with 13-cis retinoic acid, was the predominant circulating retinoic acid and was higher in GrA than the control group. Plasma IGFBP-3 concentrations were positively correlated with plasma retinol concentrations (r = 0.51), but there were no group differences. Numbers of apoptotic epithelial cells in mammary epithelium were higher at drying off and parturition than in the middle of the dry period, coinciding with high concentrations of IGF-I and lactoferrin in mammary secretions. At parturition, numbers of apoptotic cells in mammary gland biopsies in cows supplemented with vitamin A were higher than in control cows. In conclusion, supplementation of dairy cows during the dry period with high amounts of vitamin A did not significantly modify concentrations of lactoferrin, IGFBP-3, and IGF-I in plasma and in mammary secretions, but slightly decreased energy-corrected 100-d milk yield and milk fat yield, possibly because of enhanced apoptic rates of mammary cells},
  language  = {en}
}