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1.
Atelopus laetissimus is an endemic and threatened harlequin frog from the high mountain forests of Sierra Nevada de Santa Marta, Colombia. Knowledge of its reproductive biology is essential for understanding the intraspecific interactions that can help the conservation of Atelopus species. We quantified the energy, measured in body weight, invested by males and females of A. laetissimus for reproduction, and how this energetic investment is related to the survival of individuals and rainfall conditions in habitats during two years (2014 and 2015). Our results show plasticity in terms of reproductive phenology linked to rainfall with short- and long-duration breeding strategies. The first year of this study, 2014, had a precipitation level in accordance with the annual averages at the area. During this time frogs exhibit a short breeding period. Contrary to 2014, 2015 was a year with little precipitation, below the annual averages, which probably facilitated the females’ quick spawning in the creeks and a consequent reduction in the duration of amplexus and low breeding efforts by males. This, in turn, was related to a long breeding period that favors the survival and reproduction of males during the entire year. In 2014 we found a decrease of 25% to 30% body weight of potentially reproductive males, which may be attributed to a prolonged duration of amplectant events. 相似文献
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Summary The potential across the skin ofRana esculenta was remarkably reduced under Faraday conditions in comparison to animals kept under normal conditions. A pulsating electric field (10 Hz) practically abolished this effect. 相似文献
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J. R. Brentjens S. Matsuo G. A. Andres P. R. B. Caldwell L. Zamboni 《Cellular and molecular life sciences : CMLS》1986,42(4):399-402
Summary The localization of angiotensin converting enzyme (ACE) in the gonads of the normal rabbit was studied by immunofluorescence and immunoelectron microscopy. The enzyme is present in the cytoplasm of testicular spermatids and of epididymal and ejaculated spermatozoa, and on the surface of follicular and tubal cocytes. These findings support the hypothesis that ACE has a role in gamete maturation and in fertilization.Acknowledgments. This study was supported by NIH grant AM36807 and by grants from the American Heart Association, the Joe and Emily Lowe Foundation, and the Dana Foundation. We thank L. Fernandez, B. Luders, I. Pawlowski, and K. Schwegler for technical assistance. 相似文献
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E. L. Patterson W. W. Andres N. Bohonos 《Cellular and molecular life sciences : CMLS》1966,22(4):209-210
Zusammenfassung Ein Stoffwechselprodukt eines nicht klassifizierten Pilzes wurde als (+)-3-methyl-3,4-dihydro-8-oxyisocumarin, der optischen Antipode von Mellein, identifiziert. 相似文献
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Stefansson H Helgason A Thorleifsson G Steinthorsdottir V Masson G Barnard J Baker A Jonasdottir A Ingason A Gudnadottir VG Desnica N Hicks A Gylfason A Gudbjartsson DF Jonsdottir GM Sainz J Agnarsson K Birgisdottir B Ghosh S Olafsdottir A Cazier JB Kristjansson K Frigge ML Thorgeirsson TE Gulcher JR Kong A Stefansson K 《Nature genetics》2005,37(2):129-137
A refined physical map of chromosome 17q21.31 uncovered a 900-kb inversion polymorphism. Chromosomes with the inverted segment in different orientations represent two distinct lineages, H1 and H2, that have diverged for as much as 3 million years and show no evidence of having recombined. The H2 lineage is rare in Africans, almost absent in East Asians but found at a frequency of 20% in Europeans, in whom the haplotype structure is indicative of a history of positive selection. Here we show that the H2 lineage is undergoing positive selection in the Icelandic population, such that carrier females have more children and have higher recombination rates than noncarriers. 相似文献
6.
The introduction of the notion of family resemblance represented a major shift in Wittgenstein’s thoughts on the meaning of
words, moving away from a belief that words were well defined, to a view that words denoted less well defined categories of
meaning. This paper presents the use of the notion of family resemblance in the area of machine learning as an example of
the benefits that can accrue from adopting the kind of paradigm shift taken by Wittgenstein. The paper presents a model capable
of learning exemplars using the principle of family resemblance and adopting Bayesian networks for a representation of exemplars.
An empirical evaluation is presented on three data sets and shows promising results that suggest that previous assumptions
about the way we categories need reopening.
相似文献
Sunil VaderaEmail: |
7.
Gametes contain angiotensin converting enzyme (kininase II) 总被引:6,自引:0,他引:6
The localization of angiotensin converting enzyme (ACE) in the gonads of the normal rabbit was studied by immunofluorescence and immunoelectron microscopy. The enzyme is present in the cytoplasm of testicular spermatids and of epididymal and ejaculated spermatozoa, and on the surface of follicular and tubal oocytes. These findings support the hypothesis that ACE has a role in gamete maturation and in fertilization. 相似文献
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L. A. Mitscher W. W. Andres W. McCrae 《Cellular and molecular life sciences : CMLS》1964,20(5):258-259
Zusammenfassung Die Struktur des ausStreptomyces rubreticulae isolierten neuen Isocumarins, Reticulol, ist als 3-Methyl-6,8-dihydroxy-7-methoxyisocumarin ermittelt worden. 相似文献