H O Hoppen

São Paulo State University, San Paulo, São Paulo, Brazil

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Publications (37)39.92 Total impact

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    ABSTRACT: Effects of a short-term hyper- and hypoprolactinaemia on serum concentrations of LH, testosterone and semen quality in six male Beagles were investigated. Blood samples were collected at 3-day intervals for 12 weeks. The time span was divided into five 3-week periods: pre-treatment, metoclopramide (MCP) treatment (0.2 mg/kg orally three times daily), cabergoline (CAB) treatment (5 microg/kg orally once daily), post-treatment 1 and post-treatment 2. In the latter, only semen characteristics were evaluated. Semen parameters were analyzed once per week during the whole 15-week investigation time. At the end of each period, the effects of a single intravenous injection of thyrotropin-releasing hormone (TRH; 10 microg/kg) on the secretion of prolactin (PRL), LH, testosterone, thyroid-stimulating hormone and thyroxine (T4) were investigated. Pre-treatment serum PRL concentration increased under MCP (p < 0.05), followed by a decrease under CAB administration (p < 0.05). Luteinizing hormone and testosterone concentrations were not affected. Except for straight-line sperm velocity, semen quality did not differ between collection periods. A single iv TRH injection induced a significant PRL increase at 20 min in all experimental periods except during CAB treatment. Luteinizing hormone and testosterone did not show clear TRH-related changes. Basic T4 levels were significantly reduced after CAB treatment (p < 0.05). The results of the present study demonstrate that MCP-induced short-term hyperprolactinaemia in male beagles does not seriously affect the hypothalamo-pituitary axis and semen quality.
    Reproduction in Domestic Animals 07/2009; 44 Suppl 2:320-5. · 1.39 Impact Factor
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    ABSTRACT: Pharmacologically-induced luteolysis or treatment with an antiprogestin in early post-implantation pregnancy in dogs results in asynchronous death and resorption of conceptuses, indicating variable rates of response of individual conceptuses towards progesterone deficiency. This variability also seems to occur in bitches showing pregnancy failure in response to spontaneous luteal deficiency. In a total of 10 beagle pregnancies (two consecutive pregnancies of five bitches), abortifacient treatments beginning on day 24 after ovulation (ov) involved either administration of a progestin antagonist (total of six pregnancies, in three bitches) or a luteolytic regimen of prostaglandin F(2alpha)-analogue together with a dopamine agonist (total of four pregnancies, in two bitches). The outcomes were evaluated in relation to four control pregnancies in two bitches by assay of serum progesterone, prolactin and relaxin at selected time points or within selected time periods, by ultrasound of conceptuses including measurement of uterine blood flow, and parameters of the blood fibrinolytic system including plasma fibrinogen and plasminogen. The process of embryonic death and conceptus resorption was variable in onset and duration both in bitches that received the progesterone antagonist aglepristone (AGLE) and in those under the luteolytic treatment (cloprostenol combined with cabergoline). Pregnancy termination (death of all embryos or foetuses, respectively) occurred as early as day 29 and as late as day 41 after ov in AGLE-treated bitches, and not earlier than day 37 after ov in luteolytic-treatment bitches. Impending embryonic death was not predicted by changes in relaxin concentration, parameters of the fibrinolytic system, or in the perfusion of small uteroplacental vessels.
    Reproduction in Domestic Animals 07/2009; 44 Suppl 2:174-81. · 1.39 Impact Factor
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    ABSTRACT: Concentrations of progesterone, prolactin and relaxin in serum at predetermined intervals after ovulation (day 0) in non-pregnant and pregnant normocyclic Beagles were assayed and results compared with those observed in German Shepherd dogs (GSD) in a previous study. The goal was to determine possible reproductive hormone specificities related to the GSD breed. Furthermore, the effects of medroxyprogesterone acetate (MPA)-treatment in non-pregnant Beagles and of progesterone supplementation in pregnant Beagles on the hormone concentrations were examined. Mean concentrations of progesterone and prolactin were not different in the non-pregnant Beagles compared with those seen in non-pregnant GSD, except at days 50-60, when progesterone concentrations were found to be higher in Beagles (p < 0.05). Mean progesterone concentrations in pregnant Beagles at days 50-60 after ovulation (day 0) were higher (p < 0.05) than in GSD at that time, but not at earlier time periods. Prolactin concentrations were higher (p < 0.05) in Beagles throughout pregnancy compared with those in the GSD. Mean relaxin concentrations were numerically but not significantly lower in GSD than in Beagles throughout pregnancy. A 10-day oral MPA treatment did not affect progesterone or prolactin secretion in normocyclic non-pregnant Beagles. Medroxyprogesterone acetate serum concentrations were approximately 3.9 ng/ml during treatment and decreased to 0.42 and 0.021 ng/ml within 5 and 15 days after end of treatment, respectively. Intramuscular progesterone supplementation from days 30 to 40 in pregnant Beagles resulted in higher concentrations of progesterone in the 36- to 45-day time periods; prolactin and relaxin concentrations were not significantly affected during or after treatment compared with administration of placebo. The results suggest a tendency towards deficient luteal function in the short-cycle GSD bitches previously studied, which in pregnancy may reflect the observed decreased prolactin concentrations; the possibility that GSD relaxin secretion is deficiency required needs further study. As oral treatment with MPA did not affect progesterone and prolactin release, it may be useful for studying luteal function in pregnant bitches with suspected hypoluteoidism.
    Reproduction in Domestic Animals 07/2009; 44 Suppl 2:59-64. · 1.39 Impact Factor
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    ABSTRACT: Different abortifacient regimes in dogs were analysed for their effect on the pregnancy corpora lutea (CL), namely, prostaglandin F2a analogue cloprostenol (CLO) combined with dopamine agonist cabergoline (CAB), or progesterone (P4) receptor antagonist aglepristone (AGL). Ovaries were collected after 6-10 days of treatment during first trimester. The CL of the control-group showed strong expression of relaxin (RLX), its receptor RXFP1 and enzymes of steroid biosynthesis (HSD) with high peripheral P4-levels. Whereas RXL, RXFP1 and HSD were lowest expressed in the CLO/CAB-group with a massive degeneration of CL and their blood vessels combined with low peripheral P4-level. The AGL-group showed less extensive CL degeneration and more intensive staining of the examined factors than CLO/CAB. In summary, all examined factors are associated with normal luteal function and are useful tools to stage luteolysis. Although both treatments have the same abortive action, their sequence of events on the CL is different.
    Reproduction in Domestic Animals 07/2009; 44 Suppl 2:185-9. · 1.39 Impact Factor
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    ABSTRACT: Concentrations of prolactin (PRL), LH, testosterone (T), TSH and thyroxine (T(4)) were determined before and at 20, 120 and 180 min after a single iv injection of thyrotropin-releasing hormone (TRH) in eight Beagles, eight Fox Terriers, six Labrador Retrievers and five Great Danes that were normospermic. Mean basal PRL concentrations were lower in the Fox Terriers compared with the Great Danes (p < 0.05). Mean LH concentrations were higher in the Fox Terriers than in the Beagles, and T was lower in the Fox Terriers at some times but not others (p < 0.05). Thyroid Stimulating Hormone (TSH) concentrations did not differ among breeds, while mean basal T(4) values were lower in Fox Terriers compared with Labrador Retrievers and Great Danes (p < 0.05). Stimulation of T(4) secretion 120 and 180 min after iv TRH injection was most pronounced in the Beagles and less in the Fox Terriers (p < 0.05). The results of the present study indicate that potential breed differences in circulating concentrations of PRL, LH, T, TSH and T(4) in male dogs with apparently normal fertility can be encountered, but further studies are needed to determine whether the observed differences are typical features of these breeds, reflect subsets of dogs within breeds, or are in part because of possible uncontrolled parameters such as sample timing, ambient photoperiod, housing conditions or diet.
    Reproduction in Domestic Animals 07/2009; 44 Suppl 2:279-82. · 1.39 Impact Factor
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    ABSTRACT: The aim of the present study was to investigate the impact of various feed iodine supplementations up to the permitted maximum level in the EU, the effect of applying rapeseed meal (RSM) compared to a glucosinolate (GSL) free ration and the impact of two different iodine species (iodide, iodate) on milk, urinary, faecal and blood serum iodine as well as on T3 and T4 levels of blood. The results of the milk iodine are not completely shown but partly discussed in this paper. The study was conducted with 32 dairy cows, divided into 4 groups with 8 animals each. In two groups the cows were fed distillers dried grains with solubles (DDGS) as main protein source (16.5% of ration DM), in the other groups rapeseed meal (3.5 mmol GSL/kg) was applied. In each case half of the animals received feed with iodine in the form of potassium iodide, the other half as calcium iodate. Iodine supplementations of 0, 0.5, 1, 2, 3, 4 and 5 mg/kg DM were tested in consecutive periods of 21 days each. The supplementary iodine increased iodine contents of serum, urine and faeces. RSM application resulted in consistently higher iodine contents in the mentioned matrices just displaying significant differences at high supplementation levels. When feeding DDGS, at high iodine supplementations iodide caused higher serum and faecal iodine than iodate. Besides, the iodine species showed no consistent impact on the tested parameters. At the highest tested iodine supplementation (5 mg/kg DM) in the experimental groups (DDGS/iodide, DDGS/iodate, RSM/iodide, RSM/iodate) the iodine concentration of serum amounted to 234, 157, 334 and 361 µg/l, of urine to 1134, 1020, 2341 and 2513 µg/l and of faeces to 673, 354, 715 and 790 µg/kg fresh matter. At the same supplementation level T4 was significantly lowered. No impact was shown for the RSM application and the iodine species on T3 and T4. The results of the present study indicate that high iodine intakes not only cause strong increases in milk and urinary iodine but also lead to a considerable rise of iodine excretion via faeces. RSM in feed causes a shift of iodine normally excreted via milk to an excretion via urine and faeces accompanied by higher serum iodine.
    Livestock Science - LIVEST SCI. 01/2009; 125(2):223-231.
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    ABSTRACT: Rare earth elements (REE) have been used for decades in China to promote growth in plant production and farm animals. Studies are presently also being conducted under Western animal production conditions, however dose-response studies are relatively rare. In this study a total of 80 piglets were fed a diet supplemented with 0, 100, 200, 400 or 800 mg of citrate-bound rare earth elements, consisting of, %: lanthanum 30, cerium 55, praseodymium 5 and neodymium 10. The trial lasted 35 days, the initial mean body weight of the piglets was 7.2 kg. Apart from growth and feeding parameters, blood serum was analysed for T 3 and T 4 by radioimmunoassay (RIA). Feed intake decreased insignifi cantly with higher REE-levels. The daily weight gain of piglets amounted to 283 (control), 301 (100 mg), 254 (200 mg), 258 (400 mg) and 271 g (800 mg). Thyroid hormone levels increased with REE-supplementation. More dose-response studies will be necessary to prove the effects of REE on growth parameters and their intermediate effects.
    01/2008;
  • HO Hoppen
    Reproduction in Domestic Animals 10/2007; 30(4):149 - 152. · 1.39 Impact Factor
  • M. Lübbecke, E. Klug, H. O. Hoppen, W. Jöchle
    Reproduction in Domestic Animals 10/2007; 29(3):305 - 314. · 1.39 Impact Factor
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    ABSTRACT: Inhalt: Bei 1 7 klinisch geschlechtsgesunden Beagle-Rüden verschiedener Altersgruppen (1: 7 bis 8 Monate; II: 12 Monate; III: 23 Monate;IV: 3 bis 4 Jahre; V: 8 Jahre) wurden die Körper- und Hodenmaβe sowie die Sekretionsmuster von LH und Testosteron im peripheren Blutplasma bestimmt. Von jedem Ruden wurden im Abstand von 10 bis 14 Tagen zwei Blutprobenserien à 25 Einzelproben über einen Zeitraum von jeweils sechs Stunden unter Einhaltung 15 minütiger Intervalle gewonnen. Die Hodenlange war bei den 7 bis 8 Monate alten Tieren signifikant kleiner (p ≤ 0,01) als bei den älteren Rüden. Die 8 Jahre alten Hunde hatten die gröβten Gonaden. LH und Testosteron zeigten ein ausgeprägt pulsatiles Sekretionsmuster, wobei die LH-Werte zwischen 1,2 und 96 ng/ml und Testosteron zwischen 0,08 und 16 ng/ml varüerten. Die Pulsfrequenz unterschied sich nicht signifikant zwischen den Gruppen und lag im Mittel bei 4,5 Pulsen 16 Stunden. LH-Pulse wurden gewöhnlich von Testosteron-Pulsen gefolgt; der mittlere zeitliche Abstand zwischen beiden Ereignissen betrug 37 ± 15 Minuten.Die Plasmaproben der Gruppe I enthielten die höchsten LH- und die geringsten mittleren Testosteronkonzentrationen (15, 7 ± 13,6 ng/ml bzw. 2,0 ± 1,2 ng/ml). Das höchste durchschnittliche Testosteronniveau (3,6 ± 1,9 ng/ml) war in Gruppe III zu beobachten. Bei den 8 Jahre alten Hunden lag die mittlere LH-Konzentration signifikant unter derjenigen der 7 bis 8 und der 21 bis 23 Monate alten Tiere (p ± 0,01 bzw. p ± 0,05).Contents: Dynamics of LH and testosterone secretion in male beagles of different age In 17 clinically healthy male beagles of five age groups (I: 7 to 8 months, II: 12 months, III: 23 months, IV: 3 to 4 years, V: 8 years) the body size and the testicular dimensions were measured and the concentrations of LH and testosterone were determined in the peripheral blood. Two series of blood samples were collected from each dog with an interval of 10 to 14 days, each series consisting of 25 samples, taken every 15 minutes for 6 hours. The testicular length was significantly smaller (p ± 0.01) in the 7 to 8 months old dogs than in the older animals. The 8 year old dogs had the largest gonads. LH and testosterone secretion showed a marked pulsatility, with LH values ranging from 1.2 to 96 ng/ml and testosterone ranging from 0.08 to 16 ng/ml. Pulse frequency did not differ between groups and averaged 4,5 pulses/6 hours. LH pulses usually preceded testosterone pulses by an average of 37 ± 15 minutes.The samples of group I showed the highest mean LH concentration and the lowest mean testosterone value (15.7 ± 13.6 ng/ml and 2.0 ± 1.2 ng/ml resp.). The highest mean testosterone level (3.6 ± 1.9 ng/ml) was observed in group III. In the 8 year old dogs the mean LH-concentration was significantly lower than that of the animals aged 7 to 8 and 21 to 23 months (p ± 0.01 and p ± 0.05 resp.).
    Reproduction in Domestic Animals 10/2007; 25(2):78 - 86. · 1.39 Impact Factor
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    ABSTRACT: The aim of the present study was to investigate the effects of two medications on two subsequent abortions and plasma hormone concentrations of dogs. For this purpose, two groups of bitches (n=5 each), received the antiprogesterone aglepristone (Alizine) at 10mg/kg body weight on two subsequent days around day 30 after mating. In group II, the antiprolactin cabergoline (Galastop) was additionally administered po at 5 microg/kg body weight until the start of abortion. The plasma concentrations of relaxin, progesterone (P4) and estradiol-17beta (E2) were measured before, during and after each abortion. During the next cycle after the abortion, the same bitches were mated again and in pregnant animals, induction of abortion was performed as before. During the third cycle, pregnant bitches were allowed to whelp. Termination of first pregnancy occurred significantly earlier after the combined treatment (6.8 versus 10.6 days, p<0.05). In both groups and during both abortions, relaxin varied between individuals; however, there was a continuous decrease after the abortions and no significant differences between groups (p>0.05). In one bitch with high relaxin concentrations before treatment (11.6 ng/ml), a cystic endometrial hyperplasia was diagnosed. In the aglepristone only group, P4 concentrations increased significantly after the first application (p<0.05), then decreased continuously until day 45 after the beginning of abortion. In the combined group, there was a continuous decrease until day 45 (p>0.05). At this time, P4 concentrations between 0.47 and 84.9 nmol/l were measured in both groups. The level of E2 over time was not influenced by any medication. We therefore note that the two medications mainly influenced plasma concentrations of P4 in different ways, probably due to specific treatment-hormone interactions. However, all measurements fell within the range considered normal.
    Theriogenology 10/2007; 68(6):889-95. · 2.08 Impact Factor
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    ABSTRACT: In the present study the concentration of relaxin in peripheral blood plasma was assessed during canine pregnancy for its suitability as a pregnancy indicator, using a newly developed relaxin enzyme immunoassay. A significant relaxin increase was found in pregnancy at day 24 after ovulation. However, this relaxin increase did not correlate either with litter size or with body weight of the bitch. Induction of abortion with prostaglandin F2 alpha resulted in reduced peripheral relaxin levels, suggesting a damage of the placenta due to this medical intervention. Thus, the results confirm that relaxin, which is produced by the placenta, is a useful marker for early pregnancy diagnosis in the bitch. Relaxin measurement is recommended for detection of pregnancy either alone, or as supplement of ultrasonographic findings.
    DTW. Deutsche tierärztliche Wochenschrift 02/2002; 109(1):8-12. · 0.41 Impact Factor
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    ABSTRACT: The concentrations of testosterone, 5 alpha-dihydrotestosterone, oestradiol and oestrone were determined in peripheral blood plasma and semen of male dogs. In an experimental study, three Beagles were treated once with delmadinone acetate (1 mg kg-1 body weight, i.m.) and three were submitted to oral applications of finasteride (1 mg kg-1 body weight) once a day for 3 weeks. In a clinical study, 51 dogs of different breeds were divided into four groups according to the total number of spermatozoa in ejaculates (normospermia, slight oligozoospermia, severe oligozoospermia and azoospermia). The testosterone concentrations were significantly lower in sperm-rich ejaculate fractions and prostatic secretions compared with blood plasma (P < 0.05). The lowest concentration of testosterone was found in prostatic fluid. Concentrations of 5 alpha-dihydrotestosterone were similar in blood plasma and sperm-rich fractions, and significantly lower in prostatic secretions (P < 0.05). The concentrations of oestradiol and oestrone did not differ between blood plasma and either ejaculate fraction. Significantly higher 5 alpha-dihydrotestosterone concentrations and significantly lower concentrations of oestradiol and oestrone were found in prostatic secretions from azoospermic ejaculates compared with prostatic secretions of normospermic and oligozoospermic ejaculates. Delmadinone acetate and finasteride caused reversible suppression of the secretory activity of the prostate gland. The application of delmadinone acetate led to a temporary alteration of maturation of epididymal spermatozoa.
    Journal of reproduction and fertility. Supplement 01/2001; 57:83-91.
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    ABSTRACT: The effects of dopaminergic and opioidergic systems on LH and prolactin release in Pony mares were investigated. Experiments were performed in intact mares during the non-breeding and the breeding seasons and in ovariectomized mares in November, March and May. Mares were treated with the dopamine D2-antagonist sulpiride, the opioid antagonist naloxone and naloxone plus sulpiride and saline. Naloxone alone and in combination with sulpiride increased plasma LH concentrations in intact anovulatory mares and in cyclic luteal phase mares, whereas sulpiride alone had no effect. None of the treatments influenced LH release in follicular phase mares. Naloxone administration significantly increased LH release in ovariectomized mares at all times of the year, the effect being most pronounced in March. Sulpiride administration increased plasma prolactin concentrations at all times of the year and was most pronounced in cyclic mares, whereas naloxone administration did not affect prolactin secretion. These results confirm that there are opioidergic pathways that regulate LH release and undergo seasonal changes in mares. No dopaminergic regulation of LH release or interactions between dopamine and opioids was demonstrated.
    Journal of reproduction and fertility. Supplement 01/2000;
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    ABSTRACT: In this study, LH release in response to the GnRH agonist buserelin and during treatment with a progesterone-releasing intravaginal device (PRID) was studied. A dose of 20 micrograms buserelin induced a more pronounced LH release than 4, 8, 40 and 80 micrograms. After injection of buserelin, pituitary response to a second buserelin injection was markedly reduced for at least 24 hours. Repeated buserelin injections at an interval of several hours therefore cannot be recommended. LH release was markedly suppressed by treatment with PRID. Two PRID tended to be more effective than one. After PRID removal, LH release increased significantly.
    Tierärztliche Praxis. Ausgabe G, Grosstiere/Nutztiere 03/1999; 27(1):25-9. · 0.47 Impact Factor
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    C Aurich, J Lange, H O Hoppen, J E Aurich
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    ABSTRACT: The aim of this study was to investigate the influence of oestradiol, melatonin and season on the opioid regulation of LH and prolactin release. Effects of the opioid antagonist naloxone (0.5 mg/kg) on LH and prolactin secretion were determined in ovariectomized pony mares. In experiment 1, mares in January (n = 6) were pretreated with oestradiol benzoate (5 micrograms/kg) for 20 days. In experiment 2, beginning in May, mares (n = 7) received melatonin (15 mg) for 15 days and subsequently a combination of melatonin plus oestradiol for 20 days. In experiment 3, beginning in May, mares (n = 6) were pretreated with oestradiol for 30 days, left untreated for 12 days and then given melatonin for 35 days. In all experiments the animals were injected with the opioid antagonist naloxone and saline on 2 consecutive days prior to treatment. In experiment 1, animals received naloxone and saline on days 10 and 11 and 20 and 21 following oestradiol treatment. In experiment 2, naloxone and saline were administered on days 15 and 16 following melatonin treatment and on days 10 and 11 and 20 and 21 of melatonin plus oestradiol treatment. In experiment 3, the animals received naloxone and saline on days 10 and 11, 20 and 21 and 30 and 31 of oestradiol treatment, prior to melatonin treatment and on days 15 and 16, 25 and 26 and 35 and 36 following melatonin. In January (experiment 1), naloxone evoked a significant (P < 0.05) LH release at all times, however the LH increment in response to naloxone increased during oestradiol pretreatment (P < 0.05). During the breeding season (experiments 2 and 3), naloxone induced a significant (P < 0.05) increase in plasma LH concentrations when mares had not been pretreated with oestradiol or melatonin and after oestradiol pretreatment. Basal LH concentrations and the LH increment in response to naloxone increased significantly (P < 0.05) during the 30-day oestradiol pretreatment. Melatonin decreased the naloxone-induced LH release and the LH release in response to naloxone and saline no longer differed after 25 and 35 days of melatonin pretreatment. When melatonin was given together with oestradiol for 20 days, again a significant (P < 0.05) LH release in response to naloxone occurred. Prolactin release was significantly (P < 0.05) increased by naloxone when mares had been pretreated with only melatonin. The opioid antagonist did not affect prolactin release in mares that had not been pretreated or received oestradiol either alone or in combination with melatonin. In conclusion, in long-term ovariectomized mares, opioids inhibit LH secretion independent from ovarian factors. This opioid inhibition of LH secretion is enhanced by oestradiol and reduced by melatonin. Although short-term melatonin treatment inactivates the opioid regulation of LH release, a prolonged influence of melatonin as occurs in winter does not prevent activation of the opioid system. This indicates that effects of melatonin on the opioid regulation of LH release change with time. An opioid inhibition of prolactin secretion is activated by melatonin given for 15-35 days but is lost under the prolonged influence of a short-day melatonin signal in winter.
    Journal of Endocrinology 08/1997; 154(2):241-8. · 4.06 Impact Factor
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    ABSTRACT: Three groups of five beagle bitches were treated three times a day with natural prostaglandin F2 alpha (PGF2 alpha) at a dosage of either 20 micrograms kg-1 bodyweight (days 5-8 of metoestrus), 50 micrograms kg-1 bodyweight (days 5-11 of metoestrus) or 20 micrograms kg-1 bodyweight after detection of pregnancy (days 20-21 after ovulation) for 7 days. A dose of 20 micrograms PGF2 alpha kg-1 bodyweight administered during the early luteal stage could not induce a reliable decrease of progesterone concentrations, while injections of 50 micrograms PGF2 alpha kg-1 bodyweight beginning before implantation resulted in arrest of luteal progesterone production and prevention of nidation in all five bitches. The application of 20 micrograms PGF2 alpha kg-1 bodyweight shortly after implantation induced functional arrest of corpora lutea and led to embryonic or fetal resorption in all cases. In general, the luteolytic effect of low PGF2 alpha doses was insufficient because of the recovery of the corpora lutea seen in nearly all bitches and the prolonged process of embryonic or fetal resorption that increase the risk of uterine disease.
    Journal of reproduction and fertility. Supplement 02/1997; 51:251-7.
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    ABSTRACT: The blood coagulation status was studied in 31 bitches of different breeds during 33 oestrous cycles and during nine pregnancies. Two other bitches were ovariohysterectomized and received subcutaneous injections of oestradiol benzoate for 7 consecutive days. Blood samples were taken in early and late follicular phases, at ovulation, at day 1 after the end of oestrus as determined by cytology, at days 30, 60, 90 and 120 of metoestrus and in anoestrus. The samples were analysed for the concentrations of fibrinogen, fibrin(ogen) degradation products, as well as for the prothrombin time, the activated partial thromboplastin time, the antithrombin III activity, the number of platelets and the haematocrit. In other blood plasma samples the concentrations of oestradiol and progesterone were measured. In the two bitches that were ovariohysterectomized and received subcutaneous injections of oestradiol benzoate for 7 consecutive days, the coagulation parameters and hormones were examined in blood samples collected at appropriate terms and time intervals as in intact dogs. The significantly increased concentrations of fibrinogen and fibrin(ogen) degradation products, the large number of platelets and the decreased antithrombin III activity observed during the luteal phase of the nonpregnant and pregnant bitches are attributed to direct or indirect effects of the high peripheral progesterone concentrations. In the mid-luteal phase (day 30) this activation was more distinct during pregnancy than in the nonpregnant dogs presumably owing to additional effects of local processes in the uteroplacental area. Influences of high concentrations of oestradiol were not observed either during the follicular phase of the intact bitches or after oestradiol benzoate administration in the ovariohysterectomized dogs.
    Journal of reproduction and fertility. Supplement 02/1997; 51:185-93.
  • B Grünau, I Nolte, H O Hoppen
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    ABSTRACT: In the present study, the prolactin inhibitor Metergoline was compared with Bromocriptine and tested against a placebo in 63 pseudogravid bitches. Bromocriptine has already been tested successfully in numerous investigations on the therapy of canine pseudogravidity, but--probably because of its high price and vomitus as a frequent side effect--it has not been really introduced as a therapeutical device in canine practice. It can be deduced from the results presented herein that prolactin is essential for maintaining the pseudogravidity, but keeping up the lactation process--especially galactopoiesis--can probably not be ascribed solely to prolactin. However, prolactin definitely plays an essential role in the hormonal scenario, the detailed regulating mechanisms of which are not known until today. Thus, no statistically convincing therapy outcome could be achieved by the prolactin inhibitors compared to the placebo group. A tendency towards earlier regression of the symptoms "mammogenesis", "behavioural change" and "galactorrhea" was however present in the treated animals. A striking difference was the much more lively behaviour of the bitches with 53% being more lively in the Metergoline group, 37% in the Bromocriptine and 10% in the placebo group. There were also clear differences in the compatibility of the drugs; in the Bromocriptine group, 30% of the animals vomited, in the Metergoline only 6.3%. This however did not lead to termination of the therapy in any case. In two cases of the Metergoline group (6.3%), the medication was ended due to extreme restlessness.
    Tierärztliche Praxis 05/1996; 24(2):149-55. · 0.37 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 01/1996; 42(1):119-129. · 1.90 Impact Factor

Publication Stats

247 Citations
39.92 Total Impact Points

Institutions

  • 2009
    • São Paulo State University
      San Paulo, São Paulo, Brazil
  • 1991–2008
    • University of Veterinary Medicine Hannover
      • Institute of Food Toxicology and Chemical Analysis
      Hanover, Lower Saxony, Germany
  • 1993–2007
    • Hochschule Hannover
      Hanover, Lower Saxony, Germany
  • 1999–2000
    • University of Veterinary Medicine in Vienna
      Wien, Vienna, Austria