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Abstract: Interference with the pregnancy-maintaining influence of progesterone is the basis of most methods for termination of unwanted pregnancy in dogs. The currently available methods are based on induction of luteolysis or blocking of the progesterone receptor. Inhibition of progesterone synthesis using a competitive inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD) could be another strategy to terminate unwanted pregnancies. In this study we investigated the effects of the 3β-HSD inhibitor trilostane on corpus luteum function in non-pregnant bitches. Trilostane was administered orally for seven consecutive days in either the pituitary-independent part of the luteal phase (PIP, start of treatment on D11 after ovulation, n = 6) or the pituitary-dependent part (PDP, start of treatment on D31 after ovulation, n = 6), in an oral dose of about 4.5 mg/kg bw, twice daily. Results were compared with those obtained in control bitches (n = 6). ACTH stimulation tests were performed to assess adrenocortical reserve capacity. Trilostane caused no apparent side effects and ACTH stimulation tests revealed good suppression of cortisol secretion. Trilostane also caused a significant decrease in plasma progesterone concentration. When it was stopped during PIP, progesterone secretion was completely restored and there was no difference in the length of the luteal phase between those dogs and control dogs (99 days, range 70–138 d and 99 d, range 60–112 d, respectively). When trilostane was stopped during PDP there was no post-treatment recovery of progesterone secretion and although the luteal phase tended to be shorter (66 d, range 41–101 d) the difference was not significant (P = 0.09). Plasma prolactin concentration did not increase after the trilostane-induced decrease in plasma progesterone. The interoestrous interval in dogs treated during PIP (234 d, range 175–269 d) or PDP (198 d, range 120–287 d) was not significantly shorter than the control interval (247 d, range 176–313 d). In conclusion, trilostane treatment was effective in decreasing plasma progesterone concentration in bitches during the luteal phase, but the dose regimen used in this study produced less clear-cut inhibition of ovarian steroidogenesis than have other strategies to decrease plasma progesterone concentration. Further studies are warranted to determine whether trilostane can be used to terminate unwanted pregnancy in the bitch without inducing adrenocortical insufficiency. [Copyright &y& Elsevier]

Abstract: It can be difficult to confirm the presence of remnant ovarian tissue (ROT) in bitches that are presumed to be ovariohysterectomised. A GnRH stimulation test can be used to distinguish ovariectomised bitches from those in anoestrus, but it is uncertain whether the GnRH-induced changes in plasma LH and oestradiol concentrations that occur in intact bitches also occur in ROT-bitches. We report here eighteen ROT-bitches and compare the results of GnRH stimulation tests with those of six ovariectomised and six bitches in anoestrus. The basal (n = 17) and/or GnRH-stimulated (n = 18) plasma oestradiol concentration was above the detection limit of the assay, i.e., < 7 pmol/l, in all ROT-bitches but below the detection limit in all ovariectomised bitches. Basal plasma LH concentration was significantly higher in ROT-bitches (4.1 ± 0.7 μg/L) than those in anoestrus (0.64 ± 0.04 μg/L), and significantly lower than in ovariectomised bitches (20.2 ± 3.6 μg/L). Basal plasma LH concentration was relatively high in bitches in which there was a long interval between ovariectomy and appearance of oestrus. GnRH administration resulted in a significant increase in plasma LH and oestradiol concentrations in ROT-bitches. The GnRH-induced increase and subsequent decline in plasma LH concentration were significantly less in ROT-bitches than in either ovariectomised bitches or those in anoestrus. The GnRH-induced increase in plasma oestradiol concentration was significantly smaller in ROT-bitches than in those in anoestrus. In conclusion, the results of this study demonstrate that in dogs ROT is associated with noticeable changes in the pituitary-ovarian axis and suggest that a GnRH stimulation test may be used to distinguish between completely ovariectomised bitches and those with ROT. [Copyright &y& Elsevier]

Abstract: Information on the pituitary-ovarian axis in dogs with a granulosa cell tumor (GCT) is lacking. Therefore, we investigated the plasma concentrations of luteinizing hormone (LH) and estradiol before and after gonadotropin-releasing hormone (GnRH) administration in seven bitches with a functional GCT (GCT-total), of which three were intact (GCT-intact) and four had remnant ovarian tissue (GCT-ROT). The results of the GnRH stimulation test were compared with those in six anestrous and six ovariectomized bitches. The most noteworthy results were as follows. The basal plasma LH concentrations of the GCT-ROT bitches were higher (P<0.05) than those of the anestrous bitches. The increment in the plasma LH concentration after GnRH administration in the GCT-total bitches was lower (P<0.001) than the increments in both the anestrous and ovariectomized bitches. The basal plasma estradiol concentrations in the GCT-total bitches were higher (P<0.001) than those in the anestrous and ovariectomized bitches. In conclusion, the pituitary-ovarian axis is affected in bitches with a functional GCT and is characterized by relatively high plasma LH concentrations in GCT-ROT bitches and a subnormal LH response to GnRH stimulation in all GCT bitches compared with those in anestrous and ovariectomized bitches. The relatively high proportion of dogs with remnant ovarian tissue among the GCT bitches suggests a pathogenetic role for elevated gonadotropin secretion in the pathogenesis of GCT. [Copyright &y& Elsevier]

Abstract: Plasma concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined 3–6 times daily in six Beagle bitches from the start of the follicular phase until 5d after the estimated day of ovulation. The aim of the study was to gain more detailed information regarding the changes in and the temporal relation between these hormones around the time of ovulation. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. The mean duration of the pre-ovulatory FSH surge (110±8h) was significantly longer than that of the pre-ovulatory LH surge (36±5h). The FSH surge started concomitantly with the pre-ovulatory LH surge in four bitches, and 12h before the start of the LH surge in the other two bitches. The pre-ovulatory LH surge had a bifurcated pattern in four bitches. The mean plasma LH concentration before (1.9±0.4μg/L) and after (1.9±0.3μg/L) the pre-ovulatory LH surge were similar. The mean plasma FSH concentration during the period 72–28h before the pre-ovulatory LH surge (1.6±0.3U/L) was lower (P <0.001) than that during the period 100–144h after the pre-ovulatory LH surge (3.1±0.2U/L). In conclusion, this study demonstrated concurrent pre-ovulatory surges of FSH and LH and provided more evidence for differential regulation of the secretion of FSH and LH. [Copyright &y& Elsevier]

Abstract: Compared with other domestic animals, relatively little is known about the changes in, and temporal relations between, reproductive hormones around the time of ovulation in the domestic bitch. Therefore, plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol-17β, progesterone, prolactin (PRL), and α-melanocyte-stimulating hormone (α-MSH) were determined one to six times daily from the start of the follicular phase until 5 days after the estimated day of ovulation in six Beagle bitches. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. A pre-ovulatory PRL or α-MSH surge was not observed. The pre-ovulatory FSH and LH surges started concomitantly in four bitches, but in two bitches the FSH surge started 12h earlier than the LH surge. The FSH surge (110±8h) lasted significantly longer than the LH surge (36±5h). In contrast with the pre-ovulatory FSH surge, the pre-ovulatory LH surge was bifurcated in four of six bitches. The mean plasma LH concentrations before (1.9±0.4μg/L) and after (1.9±0.3μg/L) the LH surge were similar, but the mean plasma FSH concentration before the FSH surge (1.6±0.3U/L) was significantly lower than that after the FSH surge (3.1±0.2U/L). In most bitches the highest plasma estradiol-17β concentration coincided with or followed the start of the pre-ovulatory LH surge. In five of the six bitches the plasma progesterone concentration started to rise just before or concurrently with the start of the LH surge. In conclusion, the results of this study provide evidence for the differential regulation of the secretion of LH and FSH in the bitch. In addition, the interrelationship of the plasma profiles of estradiol-17β and LH suggests a positive feedback effect of estradiol-17β on LH surge release. The start of the pre-ovulatory LH surge is associated with an increase in the plasma progesterone concentration in this species. [Copyright &y& Elsevier]

A number of conjectures have been given recently concerning the connection between the antiferromagnetic XXZ spin chain at Δ = -1/2 and various symmetry classes of alternating sign matrices. Here we use the integrability of the XXZ chain to gain further insight into these developments. In doing so we obtain a number of new results using Baxter's Q function for the XXZ chain for periodic, twisted and open boundary conditions. These include expressions for the elementary symmetric functions evaluated at the ground state solution of the Bethe roots. In this approach Schur functions play a central role and enable us to derive determinant expressions which appear in certain natural double products over the Bethe roots. When evaluated these give rise to the numbers counting different symmetry classes of alternating sign matrices. [ABSTRACT FROM AUTHOR]

It is shown that solvable mixed spin ladder models can be constructed from su(N) permutators. Heisenberg rung interactions appear as chemical potential terms in the Bethe Ansatz solution. Explicit examples given are a mixed spin- $$\frac{1}{2}$$ spin-1 ladder, a mixed spin- $$\frac{1}{2}$$ spin- $${\frac{3}{2}}$$ ladder and a spin-1 ladder with biquadratic interactions. [ABSTRACT FROM AUTHOR]