Biomedical subjects

H O Hoppen

Publications and source records attributed to H O Hoppen.

At least 19 recordsLinked to original sources

PubMed2003

[The effect of hypothyroidism on cardiac function in dogs].

The thyroid hormones have direct and indirect effects on the heart. So it is possible that depression of left ventricular function is associated with hypothyroidism. This publication describes cardiac findings (auscultation, electrocardiography, echocardiography) in ten hypothyroid dogs. Low heart rates, reduced R-amplitudes and bradycardic arrhythmias (first and second-degree AV block) were found on the electrocardiogram before treatment. On the echocardiograms most of the dogs showed reduced contractillity and reduced left ventricular wall thickness. Seven dogs were reexamined after levothyroxine supplementation. Effects of treatment were increased heart rates and R-amplitudes as well as disappearance of the bradycardic arrhythmias in electrocardiographic examination. The echocardiographic examination showed increased contractility and increased left ventricular wall thickness.

Animals↗

PubMed2002

[Relaxin: an important indicator of canine pregnancy].

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.

Abortion, Induced↗

PubMed2001

Determination of concentrations of sex steroids in blood plasma and semen of male dogs treated with delmadinone acetate or finasteride.

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.

5-alpha Reductase Inhibitors↗

PubMed2000

Cyclical endometrial steroid hormone receptor expression and proliferation intensity in the mare.

The aims of this study were to investigate the steroid hormone receptor expression and the proliferation intensity during the equine endometrial cycle by immunohistological methods, established for routine examination of formalin-fixed, paraplast-embedded specimens. Endometrial biopsy specimens were obtained during one cycle from 7 mares. In comparison with the blood steroid hormone levels the quantity and distribution of oestrogen (ER) and progesterone receptors (PR) and the proliferation marker Ki-67 antigen expression were investigated. Rising 17beta-oestradiol concentrations in preoestrus induce a synchronous expression of ER, PR and Ki-67 antigen in stromal cells. In the early dioestrus 17beta-oestradiol levels decrease and progesterone levels reach their maxima. This correlates with an intense proliferation activity and the highest hormone receptor expression in epithelial cells. In accordance to the morphological features of asynchronous glandular differentiation in fibrotic areas (endometrosis) their epithelial hormone receptor expression is out of phase.

Animals↗

PubMed1999

[Therapeutic and prophylactic effect of LH-release in cattle].

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.

Administration, Intravaginal↗

PubMed1999

[Diagnosis, therapy and endocrinologic parameters of persistent follicles in mares in comparison with preovulatory follicles].

During the 1997 breeding season persistent follicles were diagnosed in 17 mares. In 16 of these mares a total of 17 follicles were transabdominally punctured and the steroids oestradiol, progesterone and testosterone were measured in the follicular fluid and in blood serum. In ten mares serving as a control group preovulatory follicles were punctured. The follicular fluid of the persistent follicles revealed a very high variability of the steroid concentrations. Depending on the steroid ratio within the follicles, eight follicles were rated as being intact, three follicles were undergoing atresia and five follicles were luteinized. Because of the high oestradiol levels of the follicular fluid within the control group, all of these follicles were considered to be intact. In both groups, no correlation of the steroid concentration between serum and follicular fluid was detectable. This fact argues against a passive diffusion of the steroids through the follicular wall. By puncturing the persistent follicles it was possible to bring the affected mares back into a physiological oestrus cycle within a normal dioestrus period.

Animals↗

PubMed1997

Influence of melatonin and oestradiol on the opioidergic regulation of LH and prolactin release in pony mares.

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.

Animals↗

PubMed1997

Dynamics of haemostasis during the oestrous cycle and pregnancy in bitches.

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.

Analysis of Variance↗

PubMed1997

Effects of low doses of prostaglandin F2 alpha during the early luteal phase before and after implantation in beagle bitches.

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.

Abortion, Induced↗

PubMed1996

[The treatment of pseudopregnancy in the bitch with prolactin inhibitors metergoline and bromocriptine].

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.

Animals↗

PubMed1995

Gonadal sex hormones and dystonia: experimental studies in genetically dystonic hamsters.

In some kinds of idiopathic dystonia, including paroxysmal dystonia, a role of sex hormones has been suggested because of female predominance and onset, recurrence, or exacerbation of dystonic symptoms with pregnancy. Similar effects of pregnancy have recently been reported in a model of paroxysmal dystonia, the genetically dystonic hamster. Dystonia in mutant hamsters of both genders is transient, i.e., exhibits spontaneous remission at around puberty, strongly suggesting involvement of gonadal sex hormones. For exploration of the role of sex hormones in dystonia, we undertook a series of ontogenetic experiments in male and female dystonic hamsters. Mutant animals of both genders exhibited the same postnatal development of dystonia with maximum severity of dystonic attacks between weaning and approximately 40 days of age and spontaneous remission thereafter. As shown by plasma sex hormone determinations and, in females, vaginal cytology, spontaneous improvement of the movement disorder coincided with puberty in both genders. Male and female hamsters had about the same plasma levels of progesterone. Compared with nondystonic hamsters, onset of puberty was significantly retarded in both male and female dystonic hamsters. Furthermore, body weight gain was lower in dystonic animals, indicating retarded postnatal development. Gonadectomy at time of weaning did not alter the age-dependent development and remission of dystonia, suggesting that gonadal sex hormones are not critically involved in the disease in hamsters. We propose that transient paroxysmal dystonia in mutant hamsters is caused by postnatal retardation of brain development resulting in a temporary impairment of brain functions with spontaneous remission independent of gonadal sex hormones. In view of the fact that the brain can synthesize steroids such as progesterone independent of peripheral glands in both genders, such neurosteroids might be involved in the postnatal brain maturation that leads to remission of dystonia at around puberty in mutant hamsters.

Age Factors↗

PubMed1995

Advanced ovulation in gilts by the intrauterine application of a low molecular mass pronase-sensitive fraction of boar seminal plasma.

The shortening of the time interval between the onset of oestrus and ovulation in sows by the transcervical administration of seminal plasma was investigated in 23 German Landrace gilts, using the technique of single horn infusions (Mariensee model) in combination with the transcutaneous sonographic monitoring of ovaries. Preparative surgery comprised the detachment of the left uterine horn from the corpus, leaving the caudal end open to the peritoneal cavity but sealing the corpus wound. The left ovary was loosely tied to the ventral abdominal wall for better sonographic distinction. The animals were used in two to four consecutive cycles. After detection of oestrus by the teaser boar, the patent (right) horns were filled by transcervical infusion of 100 ml of a variety of test solutions. Ovulation was probed by transcutaneous sonography at intervals of 4 h thereafter. Native seminal plasma provoked ovulation in the ipsilateral ovary of the treated horn 10.7 h earlier than in the contralateral ovary. This effect was reduced to 7.3 h after charcoal treatment of seminal plasma; addition of 10 micrograms oestradiol restored the effect in full, while 10 micrograms of oestradiol in PBS shortened the time interval to only 3.3 h versus the control ovary. Little effect was seen with oestrone sulfate, none with prostaglandins in PBS or with PBS alone. The preliminary characterization of the nonsteroidal component of seminal plasma advancing ipsilateral ovulation after transcervical infusion suggests a proteinaceous nature. The activity resides in the 1-10 kDa fraction separated by ultrafiltration and is lost after treatment with pronase.

Animals↗

PubMed1994

Spontaneous and GnRH-induced pulsatile LH and testosterone release in pubertal, adult and aging male beagles.

Baseline concentrations of LH and testosterone (T) in blood, their pulses, and LH and T response to GnRH (5 microg/kg) treatment were compared in 19 sexually sound male beagles and in 2 sexually dysfunctional dogs. The intact beagles were allocated to 4 groups according to age, which ranged from pubertal 7-mo-old animals to 11-yr-old adults. Baseline concentrations of LH and T were measured every 15 min for a period of 6 h and for a further 3 h following challenge with GnRH. Both LH and T were released in a pulsatile fashion with a wide range of pulse frequency and amplitude. The time intervals between the LH and T pulses ranged from 30 to 60 min, with no significant difference between groups. However, LH concentrations were significantly higher (P<0.01) and T values were markedly lower in the 7-mo-old pubertal dogs than in the other age groups. Following GnRH administration, LH peaked within 15 to 30 min in all the animals, with a significantly higher increase occurring in the pubertal group (P<0.05). Peak T values occurred 15 to 105 min after the LH peaks, with no clear increases occurring in the pubertal dogs. In the 2 sexually dysfunctional animals, LH levels increased following GnRH treatment; however, T values remained extremely low both before and after treatment, indicating loss of Leydig cell function.

Journal Article↗

PubMed1994

The equine placenta and equine chorionic gonadotrophin--an overview.

Chorionic gonadotrophins seem to be unique for primate and equid species. Unlike primates, the equine conceptus does not implant in the maternal uterine endometrium until around day 37 of pregnancy. At this time specialized cells of the trophoblast, organized in the embryonic girdle, invade the endometrium and become established in the endometrial stroma, forming the so-called endometrial cups. This migration of girdle cells is accompanied by their morphological transformation into large decidual-like cells and by the appearance of a gonadotrophic hormone in the mare's blood. There is convincing evidence today that the hormone is of chorionic origin; therefore the term equine Chorionic Gonadotrophin (eCG) seems to be more appropriate than the formerly used term Pregnant Mare Serum Gonadotrophin (PMSG). Secretion of eCG peaks between days 60 and 80 in pregnant mares, to decline gradually until day 130 of gestation, with pronounced inter-individual variation. There appear to be no hormonal regulatory mechanisms controlling eCG synthesis and secretion, suggesting that the size and the morphology of the endometrial cups are the limiting factors. Equine CG is a glycoprotein hormone, composed of noncovalently bound alpha- and beta-subunits. The alpha-subunit consists of 96 amino acids and is identical for eCG and the pituitary hormones eLH, eFSH, and eTSH. The beta-subunit is similar to beta-hCG in that both have a C-terminal extension. It is comprised of 149 amino acids and the peptide primary structure is identical to that of beta-eLH.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1994

Progestin content and biosynthetic potential of the corpus luteum of the African elephant (Loxodonta africana).

The aim of this study was to examine the progestin content and biosynthetic potential of the corpus luteum of the African elephant (Loxodonta africana). Luteal tissue was collected from nonpregnant and early, mid- and late pregnant elephants (n = 2 per group) shot in the Kruger National Park. Pieces of individual corpora lutea (2-3 per animal; 23 in total) were stored directly in ethanol before hormone analysis. Matching tissue pieces were incubated for 2 h with [3H]pregnenolone (2 x 10(5) c.p.m.), after which tissue plus medium were also stored in ethanol. Progesterone and 17 alpha-hydroxyprogesterone immunoreactivity in tissue extracts were determined by enzymeimmunoassay and radioimmunoassay, respectively, before and after reverse phase HPLC. Progesterone immunoreactivity predominated over that of 17 alpha-hydroxyprogesterone in all corpora lutea examined but concentrations of both hormones were very low (73-374 ng g-1 and 3-93 ng g-1, respectively after HPLC). There were no obvious differences in hormone concentrations in corpora lutea from animals at different reproductive stages. Progesterone and 17 alpha-hydroxyprogesterone immunoreactivity assayed before HPLC was 10-30 times higher than that measured after chromatographic separation. HPLC consistently revealed two large immunoreactive peaks associated with relatively nonpolar compounds, which together accounted for most (at least 75%) of all progesterone immunoreactivity measured. Large amounts of radioactivity with the same retention times as these peaks were also detected after HPLC in samples incubated with [3H]pregnenolone. Analysis of conversion products from four corpus luteum incubations indicated that between 52% and 84% of [3H]pregnenolone had been converted; 19-33% was accounted for by progesterone, and 12-50% by the two substances represented by the unidentified peaks. Subsequent GCMS analysis identified the two immunoreactive peaks as 5 alpha-pregnane-3 alpha-ol-20-one and 5 alpha-pregnane-3,20-dione (5 alpha-dihydroprogesterone). These results indicate that the major progestins contained within and biosynthesized by corpora lutea of African elephants are 5 alpha-reduced metabolites, and that progesterone and 17 alpha-hydroxyprogesterone are quantitatively of minor importance.

17-alpha-Hydroxyprogesterone↗

PubMed1994

Effects of the opioid antagonist naloxone on release of luteinizing hormone in mares during the anovulatory season.

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.

Animals↗

PubMed1993

Maternal and fetal prostaglandin concentrations during late gestation in dairy cattle.

A study was conducted to measure the blood plasma concentrations of prostaglandin F2 alpha (PGF2 alpha), 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM), prostaglandin E2 (PGE2) and 13,14-dihydro-15-keto-prostaglandin E2 (PGEM) in the jugular vein, umbilical vein and artery and uterine vein of 18 Holstein Friesian cows during late gestation. A caesarean section was performed on all cows before term in order to obtain blood samples from the different sources. Plasma PG concentrations in the uterine or fetal circulation were significantly higher than in jugular vein plasma. Correlations between peripheral PG metabolite concentrations and primary PG concentrations in the various sources of the uterus or fetus were not significant (r = .17-.47) and demonstrated that prostaglandin values based upon peripheral blood alone are of limited value.

Animals↗

PubMed1993

A dystocia and caesarean section model to characterize uteroplacental prostaglandin concentrations associated with retained placenta in dairy cattle.

Plasma concentrations of prostaglandin F(2a) (PGF(2a), 13, 14-dihydro-15-keto-prostaglandin F(2a) (PGFM), prostaglandin E(2) (PGE(2)) and 13,14-dihydro-15-keto-prostaglandin E(2) (PGEM) were determined by RIA in blood samples taken from the jugular vein and the uteroplacental circulation (umbilical vein, umbilical artery and uterine vein) of 13 Holstein Friesian cows during caesarean section. According to discharge of placenta cows were divided in 2 groups. Group I (shedding of placenta within 12 hours, NRP, n=8) and Group II (retained placenta, RP, n=5). In blood samples taken from the jugular vein before surgery, no significant differences existed between groups regarding PGF(2a), PGFM, PGE(2) and PGEM. Concentrations of PGF(2a) and PGFM in the uteroplacental circulation of NRP cows were significantly higher than those of RP cows (except for PGFM in the umbilical vein). For all sampling sites except the jugular vein before surgery, PGE(2) and PGEM levels of NRP cows were significantly higher compared to RP cows.

Journal Article↗