Role of the double luteinizing hormone peak, luteinizing follicles, and the secretion of inhibin for dominant follicle selection in Asian elephants (Elephas maximus).

Elephants express two luteinizing hormone (LH) peaks timed 3 wk apart during the follicular phase. This is in marked contrast with the classic mammalian estrous cycle model with its single, ovulation-inducing LH peak. It is not clear why ovulation and a rise in progesterone only occur after the second LH peak in elephants. However, by combining ovarian ultrasound and hormone measurements in five Asian elephants (Elephas maximus), we have found a novel strategy for dominant follicle selection and luteal tissue accumulation. Two distinct waves of follicles develop during the follicular phase, each of which is terminated by an LH peak. At the first (anovulatory) LH surge, the largest follicles measure between 10 and 19.0 mm. At 7 ± 2.4 days before the second (ovulatory) LH surge, luteinization of these large follicles occurs. Simultaneously with luteinized follicle (LUF) formation, immunoreactive (ir) inhibin concentrations rise and stay elevated for 41.8 ± 5.8 days after ovulation and the subsequent rise in progesterone. We have found a significant relationship between LUF diameter and serum ir-inhibin level (r(2) = 0.82, P < 0.001). The results indicate that circulating ir-inhibin concentrations are derived from the luteinized granulosa cells of LUFs. Therefore, it appears that the development of LUFs is a precondition for inhibin secretion, which in turn impacts the selection of the ovulatory follicle. Only now, a single dominant follicle may deviate from the second follicular wave and ovulate after the second LH peak. Thus, elephants have evolved a different strategy for corpus luteum formation and selection of the ovulatory follicle as compared with other mammals.

Circannual changes in the expression of vascular endothelial growth factor in the testis of roe deer (Capreolus capreolus).

Adult roe deer males show seasonal cycles of testicular growth and involution. The exact timing of these cycles requires endocrine regulation and local testicular control by autocrine/paracrine factors. Recent findings suggest that the vascular endothelial growth factor (VEGF) might have effects on both vascular and germinative cells in testis. Thus, we studied the expression pattern of vascular endothelial growth factor (VEGF) in roe deer testis using quantitative RT-PCR. The strength of VEGF mRNA expression depended on season. It reached its highest level at the peak of spermatogenesis during the pre-rutting period and had its nadir at the end of the rut when involution already began. The results suggested that VEGF may directly affect the regulation of spermatogenesis but may not be involved predominantly in testicular microvasculature as initially expected.

Serologic surveillance for selected viral agents in captive and free-ranging populations of Arabian oryx (Oryx leucoryx) from Saudi Arabia and the United Arab Emirates.

A total of 294 sera collected between 1999 and 2001 from eight captive and one free-ranging herds of Arabian oryx (Oryx leucoryx) distributed in Saudi Arabia (SA) and the United Arab Emirates (UAE) were assayed for antibodies against 13 selected viral agents. Arabian oryx have been exposed to bluetongue virus (BTV), epizootic hemorrhagic disease virus (EHDV), rinderpest virus (RPV), bovine respiratory syncytial virus (BRSV), bovine adenovirus 3 (BAV-3), cervid herpesvirus-1, foot-and-mouth disease virus, equine herpesvirus 9, and bovine viral diarrhea virus. The high seroprevalence to BTV and EHDV in the UAE and SA indicates that Arabian oryx are likely to be susceptible to infection by these viruses and therefore could act as a source of virus to vectors during the infective stage of infection. Moreover, antibodies were detected against RPV and BRSV in sera from SA and against BAV-3 in sera from the UAE. No antibodies were found against bovine herpesvirus-1, caprine herpesvirus-1, enzootic bovine leucosis virus, and peste des petits ruminants virus. On the basis of these results, caution should be applied when considering translocation of Arabian oryx, and only those proven to be free of infectious agents that might present a risk to other species should be moved.