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Publications (8)11.01 Total impact

  • C. Aurich, H. Hoppe, J E. Aurich
    Reproduction in Domestic Animals 10/2007; 30(4):188 - 192. · 1.39 Impact Factor
  • Reproduction in Domestic Animals 10/2007; 30(5):279 - 287. · 1.39 Impact Factor
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    ABSTRACT: The use of chilled-stored stallion semen is limited by its relatively short-term fertilizing capacity. An important reason for the decrease in fertility during storage is the peroxidation of sperm membrane lipids. In this study, effects of the antioxidants ascorbic acid (0.45 and 0.9 g/L) and catalase (0.45 x 10(6) and 1.8 x 10(6) units/L) on chilled-stored stallion semen were investigated. Semen was collected by artificial vagina from 7 stallions and was diluted with skim milk extender or glycin extender. Sperm motility and membrane integrity were investigated after dilution and after 24, 48 and 72 h at 5 degrees C. Ascorbic acid significantly increased the percentage of membrane-intact spermatozoa at 24, 48 and 72 h at 5 degrees C when compared with that of the controls (P < 0.05), irrespective of the extender. Ascorbic acid decreased the percentage of progressively motile spermatozoa (P < 0.05) at a concentration of 0.9 g/L in glycin extender. Catalase decreased (P < 0.05) progressively motile spermatozoa after 24, 48 and 72 h at 5 degrees C in skim milk extender at a concentration of 1.8 x 10(6) units/L. Catalase decreased (P < 0.05) the percentage of membrane-intact spermatozoa at 24 h. Motility and membrane integrity of spermatozoa after dilution with glycin extender containing catalase did not differ from the controls. In conclusion, ascorbic acid has protective effects on sperm membrane integrity in diluted stallion semen.
    Theriogenology 07/1997; 48(2):185-92. · 2.08 Impact Factor
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    ABSTRACT: Effects of seminal plasma on post-thaw motility and membrane integrity of cryopreserved horse spermatozoa were investigated. Carboxyfluorescein diacetate staining was used for the assessment of sperm membrane integrity. Adding 30% of seminal plasma from stallions with high post-thaw sperm motility to ejaculates from stallions with low post-thaw sperm motility increased progressive motility from 24.0 +/- 1.6 to 34.5 +/- 1.9% (P < 0.05) and membrane integrity from 27.0 +/- 2.1 to 34.3 +/- 2.3% membrane-intact spermatozoa (P < 0.05). Conversely, the addition of seminal plasma from stallions with low post-thaw sperm motility to ejaculates from stallions with high post-thaw motility decreased progressive motility from 36.0 +/- 1.6 to 30.0 +/- 2.7% (P < 0.05) but did not induce changes in membrane integrity. Seminal plasma from stallions with opposite post-thaw motility therefore clearly influenced the resistance of spermatozoa to the freezing and thawing process. We conclude that the individual composition of seminal plasma affects the suitability of stallions for semen cryopreservation.
    Theriogenology 10/1996; 46(5):791-7. · 2.08 Impact Factor
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    ABSTRACT: In the horse, endogenous opioids participate in the regulation of reproductive functions. Opioids inhibit LH release in mares during the luteal phase as well as in seasonally anovulatory mares and in stallions. The opioid inhibition of LH release in cyclic mares requires exposure to oestradiol and progesterone, and thus is regulated by a sequence of altering steroid environments. In seasonally anovulatory mares, an opioid inhibition of LH secretion might either be activated by low oestrogen concentrations or be independent from ovarian factors. An opioid regulation of prolactin secretion could not be detected in ovary-intact mares, irrespective of the time of the year. In ovariectomized mares, however, pretreatment with oestradiol and with oestradiol plus progesterone activated a naloxone-reversible inhibition of prolactin release. Opioids affect LH and prolactin release in stallions also. The opioid mechanisms are affected by gonadal hormones, undergo seasonal changes and, for LH, are most active during the non-breeding season. This could explain an increase in plasma LH concentrations that is seen at the beginning of the breeding season. An opioid regulation of prolactin secretion is evident in stallions, but seasonal changes do not parallel variations in the regulation of LH release.
    Animal Reproduction Science - ANIM REPROD SCI. 01/1996; 42(1):119-129.
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    ABSTRACT: In order to determine if endogenous opioids regulate luteinising hormone (LH) and prolactin secretion via a common, gonadotropin-releasing hormone (GnRH) dependent pathway in the horse, effects of the opioid antagonist naloxone (300 mg) and the GnRH agonist buserelin (20 μg) on prolactin and LH secretion were investigated in stallions (n = 22), long-term castrated geldings (n = 15) and non-lactating mares during the luteal phase of the oestrous cycle (n = 16). Blood samples for determination of LH and prolactin concentrations were withdrawn at 15 min intervals for 120 min. After 60 min of sampling, animals were treated with either naloxone, buserelin or saline. In stallions, naloxone significantly increased LH as well as prolactin release (P < 0.05), indicating an opioid inhibition of both hormones, whereas in mares, naloxone stimulated only LH secretion (P < 0.05). No changes in plasma LH or prolactin concentrations after injection of naloxone were found in geldings. In all animal groups, buserelin induced a significant release of LH (P < 0.05) without affecting prolactin. We conclude that endogenous opioids inhibit LH and prolactin release in the horse but the regulation of these two hormones involves independent opioid pathways. These are activated differentially in stallions, geldings and mares. The opioid regulation of prolactin secretion is not mediated via GnRH.
    Animal Reproduction Science - ANIM REPROD SCI. 01/1996; 44(2):127-134.
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    ABSTRACT: To investigate the involvement of endogenous opioids in the regulation of gonadotrophin release in male horses, effects of the opioid antagonist naloxone (0.5 mg kg-1 i.v.) on plasma LH and testosterone concentrations and the possible influence of season and of gonadal steroids were investigated. To determine quantitative as well as qualitative changes in gonadotrophin release, LH concentrations were measured by radioimmunoassay and by an in vitro bioassay. Experiments were performed in May, August and December. In stallions, basal LH secretion in May and August was significantly higher than in December (May versus December: P < 0.01; August versus December: P < 0.05); plasma testosterone concentrations were highest in August (August versus May: P < 0.05, August versus December: P < 0.001). The basal bioactive LH concentration and the ratio of bioactive:immunoreactive LH in stallions were highest in May. Therefore, in addition to seasonal changes in quantitative LH secretion, the bioactivity of LH in the circulation also undergoes seasonal variations. Bioactive LH concentrations and the bioactive:immunoreactive ratio in geldings were higher than in stallions. Naloxone caused a significant increase in LH release in stallions in August and December (P < 0.001); no significant increase was found in May (P = 0.06). In geldings, naloxone did not induce any changes in LH secretion; in stallions, a highly significant correlation was observed between basal testosterone concentrations and the LH increment after injection of naloxone (P < 0.001). In August and December, the bioactive:immunoreactive ratio increased significantly (P < 0.05) after injection of naloxone in stallions, indicating a preferential release of LH molecules with high bioactivity. The bioactive:immunoreactive ratio did not change after naloxone injection in May. The naloxone-induced LH release was followed by a significant increase in plasma testosterone concentrations in stallions in August (P < 0.001) and December (P < 0.05). In conclusion, endogenous opioid systems are involved in the regulation of LH and testosterone secretion in stallions. These mechanisms undergo seasonal changes: their activity is increased during winter and decreased during the breeding season. By affecting LH release, endogenous opioids, at least in part, regulate seasonal changes in reproductive activity in the stallion.
    J Reprod Fertil 12/1994; 102(2):327-36.
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    ABSTRACT: To investigate an involvement of endogenous opioids in the regulation of circannual changes in reproductive activity, effects of the opioid antagonist naloxone on the concentration of immunoreactive and bioactive luteinizing hormone (LH) in plasma were measured in mares during the anovulatory season. Naloxone (0.5 mg/kg i.v.) caused a significant increase (P < 0.05) in immunoreactive as well as bioactive LH concentration in plasma. The amplitude of the increase in LH concentrations measured with an in vitro bioassay was more pronounced than the amplitude of the increase in LH secretion determined by radioimmunoassay. This indicates that although in seasonal anovulatory mares the bioactivity of LH in plasma is low, highly bioactive LH is present in the anterior pituitary and can be released by naloxone. The LH response to naloxone did not depend on the degree of ovarian follicular activity. It can be concluded that a tonic opioid inhibition of LH release is present in mares during at least part of the anovulatory season and that endogenous opioids seem to be involved in the regulation of seasonal reproductive activity in the horse. In contrast to the situation during the breeding season, the opioid systems regulating LH release are activated independently of luteal progesterone.
    Journal of Endocrinology 07/1994; 142(1):139-44. · 4.06 Impact Factor