Browsing by Author "Schuler, Gerhard"

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    Endocrine changes during pregnancy, parturition and post-partum in guanacos (Lama guanicoe)
    (ELSEVIER SCIENCE BV, 2009) Luis Riveros, Jose; Urquieta, Bessie; Bonacic, Cristian; Hoffmann, Bernd; Bas, Fernando; Schuler, Gerhard
    Plasma concentrations of progesterone (P4), estradiol-17 beta (E2), estrone (E1) and estrone sulfate (E1S) were measured during gestation in eight guanacos kept in captivity. Gestational length was 346.1 +/- 9.8 days. P4 plasma concentrations increased after ovulation and remained elevated until parturition. However, during the last 4 weeks of gestation, a gradual decrease from 4.17 x 1.17(+/- 1) nmol/L to 2.02 x 1.95(+/- 1) nmol/L on day 5 before parturition was observed, followed by a more abrupt final decline to baseline concentrations which were reached on the day after parturition. Mean E2 plasma concentrations started to increase during the eighth month of gestation, and were significantly elevated up to maximum concentrations of 484.7 x 1.21(+/- 1) pmol/L during the last 2 months of pregnancy. Concentrations returned to baseline during the last 2 days of gestation. An increase of E1S concentrations (p < 0.01) was observed in the eleventh month of gestation. Mean El S concentrations remained rather constant during the last 3 weeks of gestation between 4 to 8 nmol/L until parturition, when a steep precipitous decline was observed. E1 concentrations were slightly elevated during the last 4 weeks of gestation, however, maximum concentrations did not exceed 1.5 nmol/L The results show distinct species specific features of gestational steroid hormone profiles in the guanaco in comparison to domestic South American camelids, such as a more pronounced gradual prepartal decrease of P4 concentrations prior to the final decline to baseline, and clearly lesser EIS concentrations during the last 4 weeks of gestation, which lack a continuous prepartal increase. (C) 2009 Elsevier B.V. All rights reserved.
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    Ovarian follicular dynamics and hormonal secretory profiles in guanacos (Lama guanicoe)
    (ELSEVIER SCIENCE BV, 2010) Luis Riveros, Jose; Schuler, Gerhard; Bonacic, Cristian; Hoffmann, Bernd; Graciela Chaves, M.; Urquieta, Bessie
    The objective of the present study was to describe ovarian activity in 11 adult non-mated guanacos, evaluated every second day for 40 days by transrectal ultrasonography and by plasma estradiol-17 beta and progesterone concentrations. An inverse relationship (r = -0.29, P < 0.001) was observed between the diameter of the largest ovarian follicle and the total number of follicles indicating that follicular growth in guanacos occurs in waves. The mean duration of follicular wave was 15.1 +/- 4.2 days with a range from 9 to 26. The follicular growth phase was 7.0 +/- 2.4 days, the static phase 3.0 +/- 1.2 days, the regression phase 5.2 +/- 2.1 days and the inter-wave interval was 12.6 +/- 5.6 days. The maximum follicular diameter in each follicular wave was 10.2 +/- 2.1 mm with a range from 7.2 to 16.1 mm. Inter-wave intervals of longer duration were associated with a larger maximum follicle diameter (P<0.001). Follicular activity alternated between ovaries in 93% of the waves with 48% of dominant follicles occurring in the left and 52% in the right ovary without differences (P>0.05). Plasma estradiol-17 beta concentrations showed a wave-like pattern, varying from 20.0 to 92.1 pmol/L. Plasma progesterone concentrations remained below 1 nmol/L without any ultrasonic evidence of ovulation during the study. These results in guanacos suggest a follicular wave pattern more similar to the llama (Lama glama) than previously described in other South American and Old World camelid species. (C) 2009 Published by Elsevier B.V.